Cataract
 

Hypermature cataract. Note the wrinkling of the anterior capsule, the lens has liquefied and leaks out of the capsule. A morgagnian cataract. The cortex  has turned into milky liquid and the  nucleus is displaced inferiorly. A rosette cataract. This is seen in  blunt trauma. Look for other signs  in the posterior segment such as choroidal tear or retinal detachment. A lamellar cataract. There are  opacities at various levels of the  fetal nucleus. It is the most common  type of congenital cataract.  A posterior subcapsular cataract.  Causes include steroid use, retinitis  pigmentosa, atopic dermatitis  diabetes and chronic uveitis. A droplet cataract seen in a patient with galactosaemia.

Cataract may be cortical, nuclear, subcapsular or in any combination. Examine the cataract with different forms of biomicroscopic illumination so that you can describe the location of the cataract. For example, retroillumination is best for anterior and posterior subcapsular opacities whereas direct focal slit illumination is best for examining the different zones of the lens and thus locate the opacities. The location of the cataract can suggest the cause.  In the examination: a. if the patient is young and has bilateral cataract. Consider the following: atopic dermatitis (observe the face for dermatitis) diabetic mellitus (examine the fundus for diabetic retinopathy retinitis pigmentosa (examine the fundi for pigmentary changes) myotonic dystrophy (note the typical facies of frontal balding, bilateral ptosis and delayed muscle relaxation) b. in unilateral cataract. Look for: Fuch's heterochromic uveitis trauma chronic uveitis retinal detachment

Questions:

1. What happen to the lens in poorly controlled diabetes mellitus?

Answer
There is a significant shift in the fluid content of the normal lens probably related to the accumulation of sorbital inside the diabetic lens. The result is myopia or rapid formation of subcapsular granular cataract also called the snowstorm cataract.

2. In which form of cataract would the patient gain a second sight and why?

Answer
Nuclear sclerotic cataract. The increased density of the nucleus increases the refractive index and as a result the patient develop myopia. As a result, patients who previously need plus lenses for reading find that they can now read without glasses.

3. How can cataract cause glaucoma?

Answer
The following mechanisms may be responsible:
a. pharcomorphic glaucoma. Cataract can increase the lens size causing shallowing of the anterior chamber and angle closure.
b. phacolytic glaucoma. Lens protein leaks form the lens and elicites a macrophagic response. The inflammatory material blocks the flow of aqueous through the trabecular meshwork.
c. phacoantigenic uveitis. This is caused by lens protein released through a ruptured lens capsule causing a granulomatous inflammation.
 
 

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