It was mentioned in an earlier chapter that diabetics tend to develop senile cataracts at an earlier stage than normal. Once developed, cataracts also progress more quickly in diabetics compared with nondiabetics. In addition, a rapidly advancing type of cataract is seen in young poorly controlled patients. This is a true diabetic cataract. This cataract is bilateral and consists of snowflake posterior or anterior opacities, matures rapidly and is similar to the rare cataract seen in starvation from whatever cause. The routine testing of urine of patients with cataracts produces a good return of positive results, making this an essential screening test.
It was also mentioned in a previous chapter that the refractive power of the lens might change in response to a rise in the blood sugar level. This results from increased hydration of the lens in patients with high uncontrolled blood sugar levels. Undiscovered diabetics quite often become short-sighted because of this so-called index myopia. They can then obtain some distance glasses and subsequently consult their doctor, who treats their diabetes. By this time the glasses are made and, of course, turn out to be unsatisfactory, because the index myopia can improve with treatment. In some instances index myopia proves irreversible, being the first sign of cataract formation.
Figure 21.1. Rubeosis iridis.EH
• Duration of diabetes
• Poor diabetic control
• Renal impairment
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