Cataract may be classified on the
-basis of stage of development
(e.g. intumescent, mature, hypermature),
-anatomical position of the
opacity (e.g. cortical, nuclear, subcapsular), or aetiology (diabetic, traumatic)
In clinical practice all 3 classifications tend to be used when describing a
cataract e.g. marked corticosteroid-induced posterior subcapsular opacities.
1. Intumescent:
When lens fibres degenerate to form a cataract there is breakdown of lens proteins into smaller molecules so that water passes into the lens which then swells. Such a lens may become so large that it causes severe shallowing of the anterior chamber and may close off the angle of the anterior chamber causing 'phakomorphic' glaucoma.
2. Mature:
A cataract is described as mature when the whole lens is opaque and no clear cortex is visible with a slit lamp. The mature cataract appears white and although the visual acuity is reduced to light perception, the ability to identify the direction of the light source is retained (normal projection to light). (LCW 4.4 p58) This important observation must always be recorded in these cases, as it gives some indication of the visual prognosis of a possible cataract extraction.
3. Hypermature:
In this stage the fens capsule in a mature cataract becomes permeable to liquefied lens matter which then leaks out into theaqueous. The cataract shrinks leaving a small brownish nucleus surrounded by a wrinkled capsule (Morgagnian cataract). Macrophages invade the aqueous
and the lens from the systemic circulation, engulf the lens matter and subsequently block the trabecular meshwork resulting in a rise in intraocular pressure ('phacolytic' glaucoma). Sometimes the cells sink to the bottom of the anterior chamber to produce the appearance of a hypopyon (sterile). The degree and speed of the pressure rise is also very variable. Lens induced
uveitis (phakoanaphylactic uveitis), due to the development of antibodies to lens protein after lens matter leaks into the anterior chamber, is to be distinguished from phacolytic glaucoma, although it may complicate it. After control of the intraocular pressure with osmotic diuretic agents e.g. diamox or mannitol and of the uveitis with corticostcroids, a lens extraction is performed. These lens induced conditions may also arise following lens capsule
rupture due to trauma or as a complication of surgery.
-basis of stage of development
(e.g. intumescent, mature, hypermature),
-anatomical position of the
opacity (e.g. cortical, nuclear, subcapsular), or aetiology (diabetic, traumatic)
In clinical practice all 3 classifications tend to be used when describing a
cataract e.g. marked corticosteroid-induced posterior subcapsular opacities.
1. Intumescent:
When lens fibres degenerate to form a cataract there is breakdown of lens proteins into smaller molecules so that water passes into the lens which then swells. Such a lens may become so large that it causes severe shallowing of the anterior chamber and may close off the angle of the anterior chamber causing 'phakomorphic' glaucoma.
2. Mature:
A cataract is described as mature when the whole lens is opaque and no clear cortex is visible with a slit lamp. The mature cataract appears white and although the visual acuity is reduced to light perception, the ability to identify the direction of the light source is retained (normal projection to light). (LCW 4.4 p58) This important observation must always be recorded in these cases, as it gives some indication of the visual prognosis of a possible cataract extraction.
3. Hypermature:
In this stage the fens capsule in a mature cataract becomes permeable to liquefied lens matter which then leaks out into theaqueous. The cataract shrinks leaving a small brownish nucleus surrounded by a wrinkled capsule (Morgagnian cataract). Macrophages invade the aqueous
and the lens from the systemic circulation, engulf the lens matter and subsequently block the trabecular meshwork resulting in a rise in intraocular pressure ('phacolytic' glaucoma). Sometimes the cells sink to the bottom of the anterior chamber to produce the appearance of a hypopyon (sterile). The degree and speed of the pressure rise is also very variable. Lens induced
uveitis (phakoanaphylactic uveitis), due to the development of antibodies to lens protein after lens matter leaks into the anterior chamber, is to be distinguished from phacolytic glaucoma, although it may complicate it. After control of the intraocular pressure with osmotic diuretic agents e.g. diamox or mannitol and of the uveitis with corticostcroids, a lens extraction is performed. These lens induced conditions may also arise following lens capsule
rupture due to trauma or as a complication of surgery.
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