optometry.naija: Glaucoma Week Series episode 7 ( Types of Glaucoma...: "Optom Glaucoma classifications could be based on the size of the angle between the corneal endothelium and anterior portion of the fenestrat..."
Optom
optometry is discussed here, eye diseases and disabilities are highlighted and management of such ocular conditions enumerated.
Sunday, 10 April 2011
Glaucoma Week Series episode 7 ( Types of Glaucoma)
Optom
Glaucoma classifications could be based on the size of the angle between the corneal endothelium and anterior portion of the fenestrated iris. This angle is a passage way to the trabecular meshwork, which contributes about 90% of total aqueous humor drainage. Hence, it could be, 1)Open angle glaucoma, & 2) Closed angle glaucoma. The former, as the name denotes, has a clear passage way to the trabecular meshwork when viewed through a Gionoscope lens on a slit lamp bi-microscope. Therefore the cause of this type of Glaucoma is not related to resistance to drainage per say, it often times result as a brake down in the physiology of the trabecular meshwork or as a result of some subtle factors that often results to disk excavation and death of ganglion cell fibres of the Retina.
The Open angle type of Glaucoma shows little or no symptom in early stages and its often always bilateral. This type of Glaucoma rarely affects children! It contributes almost 85% or more of the total glaucoma cases. It is common in the black race.
The later, Closed Angle Glaucoma, often blocks or reduces the passage way to the trabecular meshwork. It shows severe symptoms ranging from redness, pains, epiphora (excessive tearing), photophobia, haziness of the cornea etc It often affects one eye @ a time and causes a lot of discomfort to the person.
Glaucoma could classified according to a precursor. If there is a known secondary cause such as the use of topical steroids, ocular trauma, Diabetes, Hyptertension, cataract etc, such Glaucoma is known as secondary Glaucoma. This type of Glaucoma is common in adults above 60 years. While primary Glaucoma often has no known precursor (i.e. the person's eyes do not have any pre-existing ocular problem).
Glaucoma could be classified depending on mode of onset, hence a sudden symptom of Glaucoma denotes acute Glaucoma, while the type of Glaucoma that does not present symptoms in time suggests a chronic Glaucoma. It should be noted that Acute Glaucoma and closed angle glaucoma are similar also some secondary Glaucoma mimic acute onset glaucoma. And chronic glaucoma is similar to open angle Glaucoma.
Glaucoma is very dangerous but very tricky to identify, hence it becomes imperative for you to go for constant eye check to enable one identify the disease in time!
Glaucoma is a killer...be wary of it!
To be continued.....
Dr Ezebuiroh Victor Okwudiri.
Glaucoma classifications could be based on the size of the angle between the corneal endothelium and anterior portion of the fenestrated iris. This angle is a passage way to the trabecular meshwork, which contributes about 90% of total aqueous humor drainage. Hence, it could be, 1)Open angle glaucoma, & 2) Closed angle glaucoma. The former, as the name denotes, has a clear passage way to the trabecular meshwork when viewed through a Gionoscope lens on a slit lamp bi-microscope. Therefore the cause of this type of Glaucoma is not related to resistance to drainage per say, it often times result as a brake down in the physiology of the trabecular meshwork or as a result of some subtle factors that often results to disk excavation and death of ganglion cell fibres of the Retina.
The Open angle type of Glaucoma shows little or no symptom in early stages and its often always bilateral. This type of Glaucoma rarely affects children! It contributes almost 85% or more of the total glaucoma cases. It is common in the black race.
The later, Closed Angle Glaucoma, often blocks or reduces the passage way to the trabecular meshwork. It shows severe symptoms ranging from redness, pains, epiphora (excessive tearing), photophobia, haziness of the cornea etc It often affects one eye @ a time and causes a lot of discomfort to the person.
Glaucoma could classified according to a precursor. If there is a known secondary cause such as the use of topical steroids, ocular trauma, Diabetes, Hyptertension, cataract etc, such Glaucoma is known as secondary Glaucoma. This type of Glaucoma is common in adults above 60 years. While primary Glaucoma often has no known precursor (i.e. the person's eyes do not have any pre-existing ocular problem).
Glaucoma could be classified depending on mode of onset, hence a sudden symptom of Glaucoma denotes acute Glaucoma, while the type of Glaucoma that does not present symptoms in time suggests a chronic Glaucoma. It should be noted that Acute Glaucoma and closed angle glaucoma are similar also some secondary Glaucoma mimic acute onset glaucoma. And chronic glaucoma is similar to open angle Glaucoma.
Glaucoma is very dangerous but very tricky to identify, hence it becomes imperative for you to go for constant eye check to enable one identify the disease in time!
Glaucoma is a killer...be wary of it!
To be continued.....
Dr Ezebuiroh Victor Okwudiri.
Saturday, 9 April 2011
optometry.naija: Glaucoma Week Series 2011- episode 6 ( Understandi...
optometry.naija: Glaucoma Week Series 2011- episode 6 ( Understandi...: "Optom The eyeball is a pear-like globe surrounded by the uveal body and reinforced by the sclera and the cornea externally which actua..."
Optom
Optom
Glaucoma Week Series 2011- episode 6 ( Understanding Glaucoma)
Optom
The eyeball is a pear-like globe surrounded by the uveal body and reinforced by the sclera and the cornea externally which actually provides its (the eyeball's) toughness. It is filled with two types of liquid that defer basically,only, in their viscous status. They are the vitreous humor, occupying the posterior eyeball and bound by the retina posteriorly and the posterior crystalline lens, the pars plana and the ciliary process. the vitreous humor, a gel, faces the optic nerve head and the lamina cribosa. it is always almost static & rather behaves like a connective tissue!
The aqueous humor occupies the anterior portion of the eyeball, separated from the vitreous humor by the crystalline lens, pars plicata, anterior cilliary process and bound anteriorly by the endothelium of the cornea. The fluid is in a constant flux by a process known as inflow and outflow mechanisms. This two mechanisms, though poorly understood, provides the basis of intra-ocular pressure (I.O.P)of the eyeball. I.O.P is an important factor in glaucoma though its effect on individual eyeballs suggests an arbitrary relationship, yet it remains the only controllable factor in Glaucoma management.
Inflow mechanism originates from the ciliary body, anterior crystalline lens on the posterior channels, the pupillary aperture and ends @ the trabecular meshwork. @ the trabecular meshwork, the outflow mechanism commences. the trigger factor of these two mechanisms of flow is poorly understood but undoubtedly contributes hugely in the pathophysiology of glaucoma. Another outflow channel that dont really influence I.O.P is the uveo-sleral flow located around the junction of the pars plicata and the sclera. It contributes about 10% of total outflow while the trabecular meshwork contributes almost 90% of outflow & influences I.O.P & is influenced by I.O.P too.
The outflow mechanism commences from the trabecular meshwork, the Sinus Venosus Sclerae or Canal of Schlemm, into the larger episcleral venous spaces then into the vena cava...etc etc & the process repeats itself again. The indirect outflow @ the uveo-scleral spaces follows through the capillaries of that part of the ciliary body and escapes into the episcleral spaces & straight into the larger veins- the vena cava!
Any process that disrupts these dual mechanisms results in a disrupted equillibruim of flow with subsequent rise in I.O.P with a resultant pressure on the optic nerve head, the most vulnerable part of the sclera the lamina cribosa becomes a culprit, choking the optic nerve fibres and subsequent death of those fibres.
Cell mediated apoptosis especially on the lamina cribosa and/or the optic nerve fibres can also can contribute to glaucoma formation in some case of 'normal' tension glaucoma.
Ishcaemia of blood vessel supplying the optic nerve head can result to Optic nerve fibre deaths. Also neovascularisation on the optic nerve head, as in Diabetic patients for instance has been implicated in optic nerve death. These all contributes to the formation of Glaucoma but the process is poorly understood, though well articulated.
We will treat the different types of Glaucoma subsequently...
To be continued!
Dr Ezebuiroh Victor Okwudiri.
The eyeball is a pear-like globe surrounded by the uveal body and reinforced by the sclera and the cornea externally which actually provides its (the eyeball's) toughness. It is filled with two types of liquid that defer basically,only, in their viscous status. They are the vitreous humor, occupying the posterior eyeball and bound by the retina posteriorly and the posterior crystalline lens, the pars plana and the ciliary process. the vitreous humor, a gel, faces the optic nerve head and the lamina cribosa. it is always almost static & rather behaves like a connective tissue!
The aqueous humor occupies the anterior portion of the eyeball, separated from the vitreous humor by the crystalline lens, pars plicata, anterior cilliary process and bound anteriorly by the endothelium of the cornea. The fluid is in a constant flux by a process known as inflow and outflow mechanisms. This two mechanisms, though poorly understood, provides the basis of intra-ocular pressure (I.O.P)of the eyeball. I.O.P is an important factor in glaucoma though its effect on individual eyeballs suggests an arbitrary relationship, yet it remains the only controllable factor in Glaucoma management.
Inflow mechanism originates from the ciliary body, anterior crystalline lens on the posterior channels, the pupillary aperture and ends @ the trabecular meshwork. @ the trabecular meshwork, the outflow mechanism commences. the trigger factor of these two mechanisms of flow is poorly understood but undoubtedly contributes hugely in the pathophysiology of glaucoma. Another outflow channel that dont really influence I.O.P is the uveo-sleral flow located around the junction of the pars plicata and the sclera. It contributes about 10% of total outflow while the trabecular meshwork contributes almost 90% of outflow & influences I.O.P & is influenced by I.O.P too.
The outflow mechanism commences from the trabecular meshwork, the Sinus Venosus Sclerae or Canal of Schlemm, into the larger episcleral venous spaces then into the vena cava...etc etc & the process repeats itself again. The indirect outflow @ the uveo-scleral spaces follows through the capillaries of that part of the ciliary body and escapes into the episcleral spaces & straight into the larger veins- the vena cava!
Any process that disrupts these dual mechanisms results in a disrupted equillibruim of flow with subsequent rise in I.O.P with a resultant pressure on the optic nerve head, the most vulnerable part of the sclera the lamina cribosa becomes a culprit, choking the optic nerve fibres and subsequent death of those fibres.
Cell mediated apoptosis especially on the lamina cribosa and/or the optic nerve fibres can also can contribute to glaucoma formation in some case of 'normal' tension glaucoma.
Ishcaemia of blood vessel supplying the optic nerve head can result to Optic nerve fibre deaths. Also neovascularisation on the optic nerve head, as in Diabetic patients for instance has been implicated in optic nerve death. These all contributes to the formation of Glaucoma but the process is poorly understood, though well articulated.
We will treat the different types of Glaucoma subsequently...
To be continued!
Dr Ezebuiroh Victor Okwudiri.
Wednesday, 6 April 2011
optometry.naija: Glaucoma Week Series 2011- episode 5 ( The Optic n...
optometry.naija: Glaucoma Week Series 2011- episode 5 ( The Optic n...: "Optom The Optic nerve, the cranial nerve II, is the anterior extension of the white matter of the brain. It arises from the ganglion cells o..."
Optom
Optom
Glaucoma Week Series 2011- episode 5 ( The Optic nerve head)
Optom
The Optic nerve, the cranial nerve II, is the anterior extension of the white matter of the brain. It arises from the ganglion cells of the neural retina to the lateral geniculate body. It is made up of approximately 1 million axons, mainly myelinated except those of the retina. These axons relay with the visual cortex of the brain via the optic radiation. The Optic nerve head is covered by a thin strip of flexible sclera known as the lamina cribrosa.It separates the myelinated part of the Optic nerve from the unmyelinated retina. This strip of sclera is susceptible to damage & injury. The optic nerve does not possess Schwann cell and hence do not regenerate when injured or damaged.
The Optic nerve is is covered by three layers of meninges and it is surrounded by an extension of the subarachnoid space. The Optic nerve head is supplied by the arterial branches of the long and short posterior ciliary arteries, the central retinal artery and from the partial arterial circle of Haller-Zinn. The blood supply of Optic nerve drains into the central retinal vein.
To be continued...
Dr Ezebuiroh Okwudiri Victor.
The Optic nerve, the cranial nerve II, is the anterior extension of the white matter of the brain. It arises from the ganglion cells of the neural retina to the lateral geniculate body. It is made up of approximately 1 million axons, mainly myelinated except those of the retina. These axons relay with the visual cortex of the brain via the optic radiation. The Optic nerve head is covered by a thin strip of flexible sclera known as the lamina cribrosa.It separates the myelinated part of the Optic nerve from the unmyelinated retina. This strip of sclera is susceptible to damage & injury. The optic nerve does not possess Schwann cell and hence do not regenerate when injured or damaged.
The Optic nerve is is covered by three layers of meninges and it is surrounded by an extension of the subarachnoid space. The Optic nerve head is supplied by the arterial branches of the long and short posterior ciliary arteries, the central retinal artery and from the partial arterial circle of Haller-Zinn. The blood supply of Optic nerve drains into the central retinal vein.
To be continued...
Dr Ezebuiroh Okwudiri Victor.
Monday, 28 March 2011
optometry.naija: Glaucoma Week Series 2011- episode 4 ( The Trabecu...
optometry.naija: Glaucoma Week Series 2011- episode 4 ( The Trabecu...: "Optom To fully understand the pathophysiology of glaucoma, it becomes imparative to understand route of inflow as well as outflow of the aqu..."
Optom
Optom
Glaucoma Week Series 2011- episode 4 ( The Trabecular meshwork, the canal of Schlem and the Uveoscleral spaces)
Optom
To fully understand the pathophysiology of glaucoma, it becomes imparative to understand route of inflow as well as outflow of the aqueous humor. It should be remembered that the eye is considered a leaking system of aqueous humor.
The trabecular meshwork is divided into three, they include the following-
1) The inner uveal meshwork: This part is closest to the anterior chamber. It is radially oriented and contains trabeculae.
2) The corneoscleral meshwork: This part consists oflarge amount of elastin and often described as the ciliary muscle tendon.
3) The Juxtacanacular meshwork (Cribiform meshwork): This part is close to the canal of Schlem (Sinus Venosus Sclerae). It consists of a thin strip of tissue covered by mono-layer endothelial cell. It recieves support by the connective tissues ground substances full of glycoaminoglycans and glycoproteins.
The canal of Schlem is acircular canal lined with endothelium that runs around the eyeball at the corneoscleral junction. It is positioned within the internal scleral sulcus and posteriorly related to the scleral spur. The inner endothelial wall of the sinus is related to the trabecular meshwork and the anterior chamber; but there is no direct passage way between the trabecular meshwork, the anterior chamber cavity and the sinus.
The scleral sinus is drained by 25-30 collector canals via the deep scleral venous plexus, then into the intrascleral plexus & the episcleral plexus which enters the larger circulation via the anterior ciliary veins.
A few of the collector canals bypass the deep scleral venous plexus and pass directly into the sclera via the subchoroidal vessels. These collector channels are known as aqueous veins.
85-95 % of aqueous outflow takes place through the trabecular meshwork via the Sinus Venosus Sclerae.
To be continued...
Dr Ezebuiroh Victor Okwudiri
To fully understand the pathophysiology of glaucoma, it becomes imparative to understand route of inflow as well as outflow of the aqueous humor. It should be remembered that the eye is considered a leaking system of aqueous humor.
The Trabecular Meshwork
The trabecular meshwork is a spongy porous tissue lined with trabeculocytes. It is located around the base of the cornea just beyond the line of Schwalbe. It sits just above the anterior fenestrated iris. It runs the course of the entire corneal base of the eye. It is avascular.The trabecular meshwork is divided into three, they include the following-
1) The inner uveal meshwork: This part is closest to the anterior chamber. It is radially oriented and contains trabeculae.
2) The corneoscleral meshwork: This part consists oflarge amount of elastin and often described as the ciliary muscle tendon.
3) The Juxtacanacular meshwork (Cribiform meshwork): This part is close to the canal of Schlem (Sinus Venosus Sclerae). It consists of a thin strip of tissue covered by mono-layer endothelial cell. It recieves support by the connective tissues ground substances full of glycoaminoglycans and glycoproteins.
Canal Of Schlem (Sinus Venosus Sclerae)
The canal of Schlem is acircular canal lined with endothelium that runs around the eyeball at the corneoscleral junction. It is positioned within the internal scleral sulcus and posteriorly related to the scleral spur. The inner endothelial wall of the sinus is related to the trabecular meshwork and the anterior chamber; but there is no direct passage way between the trabecular meshwork, the anterior chamber cavity and the sinus.
The scleral sinus is drained by 25-30 collector canals via the deep scleral venous plexus, then into the intrascleral plexus & the episcleral plexus which enters the larger circulation via the anterior ciliary veins.
A few of the collector canals bypass the deep scleral venous plexus and pass directly into the sclera via the subchoroidal vessels. These collector channels are known as aqueous veins.
85-95 % of aqueous outflow takes place through the trabecular meshwork via the Sinus Venosus Sclerae.
The Uveoscleral pathway
The junction between the uveal portion of the eye and the sclera is linked by the ciliary body smooth muscles. This area has been noted to play a role in outflow of aqueous humor. This area provides about 5-15 % drainage of the aqueous humor. It is known as the 'Extracanalicular' pathway. The aqueous humor is drained into the orbital blood vessels. Recently, the uveoscleral pathway has assumed a very important mechanism in the outflow mechanism of the aqueous humor.To be continued...
Dr Ezebuiroh Victor Okwudiri
Sunday, 27 March 2011
optometry.naija: Glaucoma Week Series 2011- episode 3 (The anatomy ...
optometry.naija: Glaucoma Week Series 2011- episode 3 (The anatomy ...: "Optom The Ciliary Body is a complete ring tissue that runs around the inside of the anterior sclera. It measures about 6 mm wide ( sli..."
Optom
Optom
Glaucoma Week Series 2011- episode 3 (The anatomy of the ciliary body)
Optom
The Ciliary Body is a complete ring tissue that runs around the inside of the anterior sclera. It measures about 6 mm wide ( slightly wider temporally than nasally). Anteriorly, the ciliary body extends to the sleral spur (This acts as an attacchment for the ciliary body ventrally. On the posterior side, the ciliary body continues into the ora serrata of the retina.
The ciliary body is divided into the anterior 'pars plicata' which is ridged and give rise to the ciliary process on which the crystalline lens zonule suspensory ligament anastomose. And the posterior 'pars plana' is smooth and flat which extends into the ora serrata and the choroid. @ the margin between the ora serrata and the ciliary body, the 'pars plana' is modified into a scalloped edge that fits into and corresponds with the tooth-like edge of the ora serrata of the neural part of the retina.
Structurally speaking, the ciliary body is made up of (1) The ciliary epithelium, (2) The ciliary stroma, and (3) The ciliary muscle.
The ciliary epithelium is that outermost part of the ciliary body that cover the inner surface of the cilliary body. It is made of two layers of pigmented and non-pigmented epithelial cells with their apices juxtaposing. Their basement membrances lies paralel with each other. These arrengement is unique and unlike in other epithelial cell which justifies the diferences in the content of blood plasma and aqueous humor! The ciliary epithelium forms the blood-aqueous barrier which plays a significant role in Intra-ocular pressure (IOP) maintainance.
The ciliary stroma is a bundle of loose connective tissue, rich in blood vessels and melanocytes. The loose connective tissue in the stroma forms a connective tissue core with the ciliary process. The stroma also provides attachment for the ciliary muscles which functions in crystaline lens accomodation.
The ciliary muscle is innervated by the posganglionic parasympathetic fibres derived from the oculo-motor nerves, via the short cilliary nerves. They form the bulk of the ciliary body and consists of smooth muscle fibres.
Finally,the aim of this detailed discription of the ciliary body is to identify the role it plays in production of aqueous humor and the regulation of IOP in the eye. The eye is regarded as a leaking system for aqueous humor, from the ciliary body to the collector channels and aqueous veins of the Sinus venosus sclerae (canal of Schlem); or the episcleral spaces. It is on record that the rate of aqueous humor formation is approximately 2.4+/-0.6 ul/min (Micro-liter per minute).
To be continued...
Dr Ezebuiroh Okwudiri Victor.
The Ciliary Body is a complete ring tissue that runs around the inside of the anterior sclera. It measures about 6 mm wide ( slightly wider temporally than nasally). Anteriorly, the ciliary body extends to the sleral spur (This acts as an attacchment for the ciliary body ventrally. On the posterior side, the ciliary body continues into the ora serrata of the retina.
The ciliary body is divided into the anterior 'pars plicata' which is ridged and give rise to the ciliary process on which the crystalline lens zonule suspensory ligament anastomose. And the posterior 'pars plana' is smooth and flat which extends into the ora serrata and the choroid. @ the margin between the ora serrata and the ciliary body, the 'pars plana' is modified into a scalloped edge that fits into and corresponds with the tooth-like edge of the ora serrata of the neural part of the retina.
Structurally speaking, the ciliary body is made up of (1) The ciliary epithelium, (2) The ciliary stroma, and (3) The ciliary muscle.
The ciliary epithelium is that outermost part of the ciliary body that cover the inner surface of the cilliary body. It is made of two layers of pigmented and non-pigmented epithelial cells with their apices juxtaposing. Their basement membrances lies paralel with each other. These arrengement is unique and unlike in other epithelial cell which justifies the diferences in the content of blood plasma and aqueous humor! The ciliary epithelium forms the blood-aqueous barrier which plays a significant role in Intra-ocular pressure (IOP) maintainance.
The ciliary stroma is a bundle of loose connective tissue, rich in blood vessels and melanocytes. The loose connective tissue in the stroma forms a connective tissue core with the ciliary process. The stroma also provides attachment for the ciliary muscles which functions in crystaline lens accomodation.
The ciliary muscle is innervated by the posganglionic parasympathetic fibres derived from the oculo-motor nerves, via the short cilliary nerves. They form the bulk of the ciliary body and consists of smooth muscle fibres.
Finally,the aim of this detailed discription of the ciliary body is to identify the role it plays in production of aqueous humor and the regulation of IOP in the eye. The eye is regarded as a leaking system for aqueous humor, from the ciliary body to the collector channels and aqueous veins of the Sinus venosus sclerae (canal of Schlem); or the episcleral spaces. It is on record that the rate of aqueous humor formation is approximately 2.4+/-0.6 ul/min (Micro-liter per minute).
To be continued...
Dr Ezebuiroh Okwudiri Victor.
Wednesday, 23 March 2011
optometry.naija: Glaucoma Week Series 2011- episode 2 (Physiology o...
optometry.naija: Glaucoma Week Series 2011- episode 2 (Physiology o...: "Optom Its good to be back. I was researching on today's topic- The Physiology of the Aqueous Humor. To fully grasp the effect of increased i..."
Optom
Optom
Glaucoma Week Series 2011- episode 2 (Physiology of the aqueous humor)
Optom
Its good to be back. I was researching on today's topic- The Physiology of the Aqueous Humor.
To fully grasp the effect of increased intra-ocular pressure, the physiology of the aqueous humor and constituent components of the aqueous need to be studied. For instance, it is known that a range of 9-21 mmHg has been the arbitrary intra-ocular pressure which is chiefly due to the aqueous humor; the aqueous humor has been known to carry pre-cursors like glutamate that lead to retinal ganglion cell apoptosis in the presence of cellular Nitric Oxide and the presence of plasma protein in the aqueous humor which increases the intra-ocular pressure.
The primary function of the aqueous humor includes the following:
* Maintaining the structural integrity of the eyeball
* Provides nutrition for avascular structures of the eyes- the crystalline lens,cornea & trabecular meshwork.
*It facilitates cellular & humoral immune responses.
* It provides a barrier against cataractogenic ultraviolet radiations.
Leber's theory of simple filtration assumes that the walls of the cillary capillaries of the eyes acts like a sieve and the aqueous humor was filtered through the walls of the capillaries by the pressure of the blood.
Blood plasma & the aqueous humor are roughly composed of equal soluble solutes but contain roughly unequal amounts of proteins, non-electrolytes(e.g. Glucose, urea etc), electrolytes (e.g. Sodium ions etc), organic acids. This theory of simple filtration could not explain it.
Hence leading to the postulations of other mechanisms, viz
1) Ultra-filtration which assumes that the cilliary walls acts as a semi-permeable membrance which allows water and soluble solutes to easily pass through leaving behind the non-soluble macro-molecules behind. This mechanism could not explain the reason why, say, freely diffusable urea and glucose are less in the aqueous than in the blood plasma etc.
2)Secretion-diffusion theory assumes the cilliary body as a semi-permeable membrane but secretion is by active transport in the presence of carbonate ions as buffer system or actively involved in the active transport of H+ ion which determines the flow of aqueous humor. Remember the effect of Diamox on aqueous humor secretion? It depends on this mechanism.
3) Pinocytosis assumes that the vesicles on the epithelium of the cillary body is a vesicle undergoing endocytosis in the presence of ATP (Adenosine Triphosphate) which explains the mechanism of secretion of aqueous humor.
Its good to be back. I was researching on today's topic- The Physiology of the Aqueous Humor.
To fully grasp the effect of increased intra-ocular pressure, the physiology of the aqueous humor and constituent components of the aqueous need to be studied. For instance, it is known that a range of 9-21 mmHg has been the arbitrary intra-ocular pressure which is chiefly due to the aqueous humor; the aqueous humor has been known to carry pre-cursors like glutamate that lead to retinal ganglion cell apoptosis in the presence of cellular Nitric Oxide and the presence of plasma protein in the aqueous humor which increases the intra-ocular pressure.
The primary function of the aqueous humor includes the following:
* Maintaining the structural integrity of the eyeball
* Provides nutrition for avascular structures of the eyes- the crystalline lens,cornea & trabecular meshwork.
*It facilitates cellular & humoral immune responses.
* It provides a barrier against cataractogenic ultraviolet radiations.
Formation of aqueous humor
There is no clear-cut explanation of the exact mechanism of aqueous humor formation. The theory of Laber on simple filtration had been the generally accepted mechanism of aqueous humor formation until recent studies showed it could not explain the many differences between blood plasma and the aqueous humor.Leber's theory of simple filtration assumes that the walls of the cillary capillaries of the eyes acts like a sieve and the aqueous humor was filtered through the walls of the capillaries by the pressure of the blood.
Blood plasma & the aqueous humor are roughly composed of equal soluble solutes but contain roughly unequal amounts of proteins, non-electrolytes(e.g. Glucose, urea etc), electrolytes (e.g. Sodium ions etc), organic acids. This theory of simple filtration could not explain it.
Hence leading to the postulations of other mechanisms, viz
1) Ultra-filtration which assumes that the cilliary walls acts as a semi-permeable membrance which allows water and soluble solutes to easily pass through leaving behind the non-soluble macro-molecules behind. This mechanism could not explain the reason why, say, freely diffusable urea and glucose are less in the aqueous than in the blood plasma etc.
2)Secretion-diffusion theory assumes the cilliary body as a semi-permeable membrane but secretion is by active transport in the presence of carbonate ions as buffer system or actively involved in the active transport of H+ ion which determines the flow of aqueous humor. Remember the effect of Diamox on aqueous humor secretion? It depends on this mechanism.
3) Pinocytosis assumes that the vesicles on the epithelium of the cillary body is a vesicle undergoing endocytosis in the presence of ATP (Adenosine Triphosphate) which explains the mechanism of secretion of aqueous humor.
Rate of flow of Aqueous humor
About 150uL/Hr with a range of 1.1%-1.9% of the volume of the anterior chamber per minute.
Physical characteristics of AH
a) It has a higher osmotic pressure than blood plasma.
b) It as a slightly higher specific gravity than water.
c) It has a slightly more alkalinic PH than the blood. PH is 7.53.
d) It has a refractive index of 1.336.
Factors that affect the formation of AH
1) Breakdown of blood/aqueous barrier.
2) Changes in the lumen of cilliary capillaries.
3) Changes in IOP.
4) Diurnal Variation.
5) Age etc
To be continued,
Dr Victor Ezebuiroh Okwudiri
2) Changes in the lumen of cilliary capillaries.
3) Changes in IOP.
4) Diurnal Variation.
5) Age etc
To be continued,
Dr Victor Ezebuiroh Okwudiri
Sunday, 20 March 2011
Glaucoma Week Series 2011- episode 1
Optom
Yesterday, I introduced Glaucoma as a chronic eye disease syndrome that destroys the Optic nerve head secondary to intra-ocular pressure build-up and/or ishaemia of retinal vessels.
The cilliary body, a part of the cilliary process which holds the crystalline lens in place, is a serous membrane that secretes the aqueous humour. The cilliary body is located in the posterior portion of the eyeball as against the anterior portion of the eye that houses the anterior chamber, the canal of Shclem,the Trabecular meshwork & the Episleral outflow.
The aqueous humour secreted flows through the posterior to the anterior chamber via the pupillary opening. This process is continuous since the almost avascular anterior chamber must get nutrition and maintain an amount of internal pressure to resist implosion. The aqueous humour is responsible in maintaining the transparency of the cornea and the crystalline lens, it also enable these structures not to dry up. The aqueous humour also contain immunological properties that protect the internal eye from diseases. But it must flow out through the trabecular meshwork and/or the Episcleral spaces.
The amount of inflow of the aqueous and that of the outflow must maintain a kind of equilibrium. The absence of the equilibrium is one of the theories of the formation of Glaucoma.
To be continued.
Dr Ezebuiroh Victor.
Yesterday, I introduced Glaucoma as a chronic eye disease syndrome that destroys the Optic nerve head secondary to intra-ocular pressure build-up and/or ishaemia of retinal vessels.
The cilliary body, a part of the cilliary process which holds the crystalline lens in place, is a serous membrane that secretes the aqueous humour. The cilliary body is located in the posterior portion of the eyeball as against the anterior portion of the eye that houses the anterior chamber, the canal of Shclem,the Trabecular meshwork & the Episleral outflow.
The aqueous humour secreted flows through the posterior to the anterior chamber via the pupillary opening. This process is continuous since the almost avascular anterior chamber must get nutrition and maintain an amount of internal pressure to resist implosion. The aqueous humour is responsible in maintaining the transparency of the cornea and the crystalline lens, it also enable these structures not to dry up. The aqueous humour also contain immunological properties that protect the internal eye from diseases. But it must flow out through the trabecular meshwork and/or the Episcleral spaces.
The amount of inflow of the aqueous and that of the outflow must maintain a kind of equilibrium. The absence of the equilibrium is one of the theories of the formation of Glaucoma.
To be continued.
Dr Ezebuiroh Victor.
Saturday, 19 March 2011
optometry.naija: Glaucoma Week Series 2011
optometry.naija: Glaucoma Week Series 2011: "Optom Glaucoma is a chronic eye disease syndrome that ultimately destroys the optic nerve head @ the insertions of the lamina cribrosa..."
Optom
Optom
Glaucoma Week Series 2011
Optom
Glaucoma is a chronic eye disease syndrome that ultimately destroys the optic nerve head @ the insertions of the lamina cribrosa. This eye disease syndrome is presented with the following:
1) Cupping of the optic nerve head.
2) Reduction in the central visual field.
3)Compromised intra-ocular pressure.
4) Progressive retinal vascular ischaemia
5) Retinal ganglion cell fibre apoptosis secondary to the release of glutamate in the area of infaction.
Glaucoma is divided into the primary and secondary types, depending on the disease process. The primary type is often idiopathic, while the secondary type is almost always as a result of an underlying cause like Diabetes, hypertension, Uveitis, smaller than normal angle between the anterior iris and the corneal endothelium etc. The primary type accounts for almost 75-80 % of glaucoma, while the secondary is comparatively rare.
Glaucoma has no cure and the aim of management is to reduce or even stop the progressive excavation of the optic nerve head in the area of the lamina cribrosa. Though intra-ocular pressure compromise is the target of treatment, but research is going on presently on the use of neuro-protectors to reverse and/or stop the process of apoptosis.
Africans and Asians are more commonly affected by primary & secondary glaucoma respectively. Aging increases the chances of developing the disease. Other factors includes positive family history of glaucoma, diabetes, hypertension, cataract, ocular blunt trauma, the use of steroids for a prolonged period of time, myopia especially the progressive type of myopia etc
Glaucoma stills your sight silently in most cases & nothing can be done about that! We therefore ask you to be wary of such. Go for regular eye tests. The Glaucoma series continues tomorrow.
Dr Victor Ezebuiroh.
Glaucoma is a chronic eye disease syndrome that ultimately destroys the optic nerve head @ the insertions of the lamina cribrosa. This eye disease syndrome is presented with the following:
1) Cupping of the optic nerve head.
2) Reduction in the central visual field.
3)Compromised intra-ocular pressure.
4) Progressive retinal vascular ischaemia
5) Retinal ganglion cell fibre apoptosis secondary to the release of glutamate in the area of infaction.
Glaucoma is divided into the primary and secondary types, depending on the disease process. The primary type is often idiopathic, while the secondary type is almost always as a result of an underlying cause like Diabetes, hypertension, Uveitis, smaller than normal angle between the anterior iris and the corneal endothelium etc. The primary type accounts for almost 75-80 % of glaucoma, while the secondary is comparatively rare.
Glaucoma has no cure and the aim of management is to reduce or even stop the progressive excavation of the optic nerve head in the area of the lamina cribrosa. Though intra-ocular pressure compromise is the target of treatment, but research is going on presently on the use of neuro-protectors to reverse and/or stop the process of apoptosis.
Africans and Asians are more commonly affected by primary & secondary glaucoma respectively. Aging increases the chances of developing the disease. Other factors includes positive family history of glaucoma, diabetes, hypertension, cataract, ocular blunt trauma, the use of steroids for a prolonged period of time, myopia especially the progressive type of myopia etc
Glaucoma stills your sight silently in most cases & nothing can be done about that! We therefore ask you to be wary of such. Go for regular eye tests. The Glaucoma series continues tomorrow.
Dr Victor Ezebuiroh.
Friday, 18 March 2011
optometry.naija: Naija Optometry and their place in public health s...
optometry.naija: Naija Optometry and their place in public health s...: "Optom Optometry is comparatively new in this country Naija. Before 1987, most Optometrists were B.Sc holders in Optometry (The English versi..."
Optom
Optom
Naija Optometry and their place in public health sector
Optom
Optometry is comparatively new in this country Naija. Before 1987, most Optometrists were B.Sc holders in Optometry (The English version of Optometry). We could not integrate or be integrated into the main stream health sector- have you noticed that in most military recruitments, Optometric qualifications are not indicated!
Does it baffle you? It's the fact.
In 1987 when the new Doctors of Optometry (O.D.) were inducted from Abia state University, a mere state university for that matter, the B.Sc graduates and undergraduates from UniBen, A federal University, were put under pressure to upgrade their certificates in ABSU to O.D.; a move that did not go down well with our UniBen counterpart, subsequently those that could afford to go to USA or Canada, where OD is awarded, left! The rest either countinued with their B.Sc Optometry till date practising & our catatonic regulatory body is not expected to bat an eyelid.
When the ODs both locally gotten or got from a foriegn universities were busy garbing themselves with their new found title they let their position to eye health slip. @ the moment, most Ophthalmic nurses would challenge an Optometrist in a public health facility! why? Because most Optometrists are not employed by the ministry of health, despite what the real sector stands to gain by such inclusion. Our Regulatory body is a toothless bulldog & a lazy one for that matter; second, our internal squabble between ABSU, IMSU or UNIBEN product dwarfed our relevance then finally no plan for Optometric department of a hospital. You might want to argue that an Optometric unit is located in the department of Ophthalmology in 'big' hospitals; what we actually have there is an Optical workshop than an Optometric Department!
Consequently, the Public health sector cannot boast to have a control of ocular related disabilities. The very many poor surgical outcomes in many government hospitals could be traced to the near absence of Optometrists in this sector. Other challenges faced in the Ophthalmology departments due to the under utilization of Optometrists includes bad refraction, poor procedural approach to eye care, poor rehabilitative eye care, poor ocular post-surgical care & outcome etc
The sustainability of eye care is a function of the Optometrist all over the world. The emphasis of the government on health care reform should not live eye care behind. For an eye care management to be effective, the place of the Optometrist both in the private & public health sectors should be the top priority. We are hence urging the ministry of health all over the federation to make practising Optometry in government hospitals a must. Let departments of Optometry in the hospitals be upgraded to challenge the overwheming cases of eye diseases or disabilities! Please we cant afford to wait anylonger.
Dr Ezebuiroh Victor.
Optometry is comparatively new in this country Naija. Before 1987, most Optometrists were B.Sc holders in Optometry (The English version of Optometry). We could not integrate or be integrated into the main stream health sector- have you noticed that in most military recruitments, Optometric qualifications are not indicated!
Does it baffle you? It's the fact.
In 1987 when the new Doctors of Optometry (O.D.) were inducted from Abia state University, a mere state university for that matter, the B.Sc graduates and undergraduates from UniBen, A federal University, were put under pressure to upgrade their certificates in ABSU to O.D.; a move that did not go down well with our UniBen counterpart, subsequently those that could afford to go to USA or Canada, where OD is awarded, left! The rest either countinued with their B.Sc Optometry till date practising & our catatonic regulatory body is not expected to bat an eyelid.
When the ODs both locally gotten or got from a foriegn universities were busy garbing themselves with their new found title they let their position to eye health slip. @ the moment, most Ophthalmic nurses would challenge an Optometrist in a public health facility! why? Because most Optometrists are not employed by the ministry of health, despite what the real sector stands to gain by such inclusion. Our Regulatory body is a toothless bulldog & a lazy one for that matter; second, our internal squabble between ABSU, IMSU or UNIBEN product dwarfed our relevance then finally no plan for Optometric department of a hospital. You might want to argue that an Optometric unit is located in the department of Ophthalmology in 'big' hospitals; what we actually have there is an Optical workshop than an Optometric Department!
Consequently, the Public health sector cannot boast to have a control of ocular related disabilities. The very many poor surgical outcomes in many government hospitals could be traced to the near absence of Optometrists in this sector. Other challenges faced in the Ophthalmology departments due to the under utilization of Optometrists includes bad refraction, poor procedural approach to eye care, poor rehabilitative eye care, poor ocular post-surgical care & outcome etc
The sustainability of eye care is a function of the Optometrist all over the world. The emphasis of the government on health care reform should not live eye care behind. For an eye care management to be effective, the place of the Optometrist both in the private & public health sectors should be the top priority. We are hence urging the ministry of health all over the federation to make practising Optometry in government hospitals a must. Let departments of Optometry in the hospitals be upgraded to challenge the overwheming cases of eye diseases or disabilities! Please we cant afford to wait anylonger.
Dr Ezebuiroh Victor.
Wednesday, 16 March 2011
Practising Optometry in Naija
Optom
In 1981 the American version of Optometry was introduced in A.B.S.U & the first set OD (Doctor of Optometry) was inducted in 1987, since then the scope of practice entered on the fast drive. From lens prescription & glazing, to the dispensing of topical agents, then to the long term co-management of such chronic diseases with ocular co-morbidity like Diabetes, Hypertension, Rheumatoid Arthritis etc; finally today some Optometrists are venturing into minor ocular surgeries!
Eye care management is a complex and expensive procedure...but blindness is more expensive! Governments worldwide, often subsidizes the expensiveness of eye care management which the long run effect is the massive reduction in blindness and improved activities of daily living. It is not so in Naija.
Eye care is not a government priority in Naija. The trail blazing success in Optometry, which gives more than 75% of eye care services in this country, are mostly the private sector initiatives. More than 80% of Optometric practices in Naija are owned by private individuals. In southern Naija alone, 90% of Optometric clinics are run by individuals.
Government hospitals that run a well equiped Optometric eye centres can only be found in Abuja, Lagos and maybe in Portharcourt and Enugu etc. The reason is partly on the government's insensitivity to the health sector, partly the squabble between the very few Ophthalmologists practising in this country and optometrists practising locally; partly to the almost precarious regulatory board of ours - NOA & ODOBN (Nigerian Optometrist Association & Optometrists and Dispensing Optician Board of Nigeria).
Despite these odds, private practises especially in the rural & semi-rural areas, had to rely on obsolete equipments like the schiotz Tonometers etc in managing cases in those areas. The lack of credit facilities to site such Optometric centres in those areas are almost non available except from private donations or loans that attract 30% to 40% interest rates. In such circumstance, the cost of providing services to these rural and semi-rual areas comes with a high tag which these superstitious people could hardly affort. Inshort, pracising Optometry in the rural areas or semi-rural areas in Naija is an uphill task...in those areas, avoidable causes of blindness is winning!
Vision 2020 initiatives which were planned with the rurals & semi-rurals had been highjacked for personal aggrandizement. The cost of standard eye equipments are very prohibitive and there is a huge interllectual drain in this field to other countries where praticising Optometry is rewarding. This has allowed the untrained Opticians to take over especially in the south and by the horrible Ophthalmic nurses in the north of Naija.
More rural dwellers and semi-rural individuals are fast lossing the battle to avoidable causes of blindness, while Vision 2020 is less than 9 years from today! Is Vision 2020 a mirage or a reality?
Optometry has a role to play here as usual, we are asking all the factors contributing to this disgaceful loss in the battle for 'right to sight'. We have a stake here, yes, in restoring sight to the blind!
Dr Victor Ezebuiroh.
In 1981 the American version of Optometry was introduced in A.B.S.U & the first set OD (Doctor of Optometry) was inducted in 1987, since then the scope of practice entered on the fast drive. From lens prescription & glazing, to the dispensing of topical agents, then to the long term co-management of such chronic diseases with ocular co-morbidity like Diabetes, Hypertension, Rheumatoid Arthritis etc; finally today some Optometrists are venturing into minor ocular surgeries!
Eye care management is a complex and expensive procedure...but blindness is more expensive! Governments worldwide, often subsidizes the expensiveness of eye care management which the long run effect is the massive reduction in blindness and improved activities of daily living. It is not so in Naija.
Eye care is not a government priority in Naija. The trail blazing success in Optometry, which gives more than 75% of eye care services in this country, are mostly the private sector initiatives. More than 80% of Optometric practices in Naija are owned by private individuals. In southern Naija alone, 90% of Optometric clinics are run by individuals.
Government hospitals that run a well equiped Optometric eye centres can only be found in Abuja, Lagos and maybe in Portharcourt and Enugu etc. The reason is partly on the government's insensitivity to the health sector, partly the squabble between the very few Ophthalmologists practising in this country and optometrists practising locally; partly to the almost precarious regulatory board of ours - NOA & ODOBN (Nigerian Optometrist Association & Optometrists and Dispensing Optician Board of Nigeria).
Despite these odds, private practises especially in the rural & semi-rural areas, had to rely on obsolete equipments like the schiotz Tonometers etc in managing cases in those areas. The lack of credit facilities to site such Optometric centres in those areas are almost non available except from private donations or loans that attract 30% to 40% interest rates. In such circumstance, the cost of providing services to these rural and semi-rual areas comes with a high tag which these superstitious people could hardly affort. Inshort, pracising Optometry in the rural areas or semi-rural areas in Naija is an uphill task...in those areas, avoidable causes of blindness is winning!
Vision 2020 initiatives which were planned with the rurals & semi-rurals had been highjacked for personal aggrandizement. The cost of standard eye equipments are very prohibitive and there is a huge interllectual drain in this field to other countries where praticising Optometry is rewarding. This has allowed the untrained Opticians to take over especially in the south and by the horrible Ophthalmic nurses in the north of Naija.
More rural dwellers and semi-rural individuals are fast lossing the battle to avoidable causes of blindness, while Vision 2020 is less than 9 years from today! Is Vision 2020 a mirage or a reality?
Optometry has a role to play here as usual, we are asking all the factors contributing to this disgaceful loss in the battle for 'right to sight'. We have a stake here, yes, in restoring sight to the blind!
Dr Victor Ezebuiroh.
Monday, 14 March 2011
Training Optometrists recieve in Nigerian Universities
Optom
The poor representation of Nigeiran Optometrists in the face of globalization and age of internet is an obvious nemesis when it comes to putting down stakes in the affairs of eye care management in this country, Naija.
Most modern equipments are not introduced to the undergraduate Optometrist at all. They are left in the blind & suddenly automated equipments, both the ones we've heard about and some that so many interns & undergraduates have not heard of.
Aside the horrible half-baked preparations to start practising Optometry in our universities, the morale's low due mainly to our toothless-bulldog board. The Optometrist and Dispensing Optician Board of Nigeria (ODOBN) is not very representative, as well as the various schools that train Optometrists!
We call on the appropiate authorities to make necessary concessions & prepare us for Vision 2020!
Dr Ezebuiroh Okwudiri.
The poor representation of Nigeiran Optometrists in the face of globalization and age of internet is an obvious nemesis when it comes to putting down stakes in the affairs of eye care management in this country, Naija.
Most modern equipments are not introduced to the undergraduate Optometrist at all. They are left in the blind & suddenly automated equipments, both the ones we've heard about and some that so many interns & undergraduates have not heard of.
Aside the horrible half-baked preparations to start practising Optometry in our universities, the morale's low due mainly to our toothless-bulldog board. The Optometrist and Dispensing Optician Board of Nigeria (ODOBN) is not very representative, as well as the various schools that train Optometrists!
We call on the appropiate authorities to make necessary concessions & prepare us for Vision 2020!
Dr Ezebuiroh Okwudiri.
Thursday, 10 March 2011
Optometry in Action!
Optom
Optometry has definitely come to stay in Naija, Africa and the world @large. with the overwhelming geometric rate of blindness, visual handicap etc as a result of Cataract, Glaucoma, Refractive errors etc one can understand our position in area of visual health priority!
Our dear Ophthalmologists are too few @ in most cases under-trained to tackle the over-flow of patients with vision challenges.
I see a time coming when Optometrists would be placed in the front-burner in the issues of say, cataract extraction...we're effectively managing Glaucoma and other chronic ocular conditions!
All I can say's that Optometry is the solution of blindness in 21st century & beyond. Hence Optometrists, answer that clarion call.
Prepare yourselves professionally for the challenges ahead! Vision 2020 is a professional responsibility!
Dr Ezebuiroh Odogwu Victor.
Optometry has definitely come to stay in Naija, Africa and the world @large. with the overwhelming geometric rate of blindness, visual handicap etc as a result of Cataract, Glaucoma, Refractive errors etc one can understand our position in area of visual health priority!
Our dear Ophthalmologists are too few @ in most cases under-trained to tackle the over-flow of patients with vision challenges.
I see a time coming when Optometrists would be placed in the front-burner in the issues of say, cataract extraction...we're effectively managing Glaucoma and other chronic ocular conditions!
All I can say's that Optometry is the solution of blindness in 21st century & beyond. Hence Optometrists, answer that clarion call.
Prepare yourselves professionally for the challenges ahead! Vision 2020 is a professional responsibility!
Dr Ezebuiroh Odogwu Victor.
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