Pupil size hints a future woes for young diabetics

By David Douglas

NEW YORK (Reuters Health) - Tests of pupil function, as an indicator of how well the automatic nervous system is working, may help predict how likely young diabetics are to develop "microvascular disease" -- that is disease of the small blood vessels -- as many diabetic do.

Australian researchers found that small pupil size in adolescents with type 1 diabetes predicted deterioration of the retina, or retinopathy, and also microalbuminuria, 12 years later.

Microalbuminuria is a complication of diabetes marked by small amounts of the protein albumin in urine. It is the first sign of kidney disease and a marker of increased risk of heart disease.

Dr. Ann M. Maguire, of The Childrens Hospital at Westmead, Sydney, and colleagues examined data on 335 adolescents with type 1 diabetes who had undergone tests of cardiovascular and pupillary regulation by the so-called autonomic nervous system in the early 1990s.

Some 12 years later, attempts were made to contact these subjects and ultimately 137 participated in the follow-up study.

Of these participants, 10 percent of patients had had severe retinopathy that required laser therapy, 15 percent had moderate retinopathy and 44 percent had mild retinopathy. In all, 19 percent had microalbuminuria.

While there was no relationship between baseline cardiovascular tests and the development of complications, the team found that small pupil size -- a marker of early nerve damage -- at baseline was independently associated with the development of microalbuminuria and retinopathy.

"These patients," Maguire concluded, "may represent a high-risk group who would benefit from more intensive insulin therapy. We recommend further research to determine if improved (blood sugar) control when pupil abnormalities first appear would improve the condition and lead to fewer complications."

SOURCE: Diabetes Care January 2007.