According to a report released in May, an estimated 18 million Americans now have diabetes and another 20 million have impaired glucose tolerance that can lead to the full-blown disease. The prevalence of type 2, in fact, has tripled in the last 30 years along with the steady upsurge in obesity. In addition to facing higher rates of heart disease and potential complications such as neuropathy and retinopathy, diabetics are also more likely to suffer from dry eye according to findings from a recent prospective study (1).

Researchers followed the medical records of nearly 160,000 patients, 22,382 of them diabetics, in one of Israel's largest HMOs for 1 year. All filled prescriptions for ocular lubricants were documented, and the proportion of ocular lubrication consumers among diabetic and non-diabetic patients aged 50 and older was compared. HbA1c was also measured to examine the relationship between glycemic control and lubricant use.

A significantly higher percentage of diabetics (21%) were shown to receive the medications compared with non-diabetics (14%) in all age groups and for both sexes (Fig 1). Significantly more diabetics were frequent users of the medication (> 12 filled prescriptions yearly) than were KCS patients without diabetes. A clear trend between higher lubricant use and poorer glycemic control, regardless of age, was also observed.

The findings suggest that blood sugar control is important in preventing or reducing KCS in diabetics. According to the authors, small vessel damage and autonomic neuropathy may reduce lacrimal gland function. Decreased corneal sensitivity, which interrupts tearing reflex, could also play a role.

Commentary

Results from several small controlled trials report that supplemental gamma-linolenic acid (GLA) improves symptoms of dry eye in KCS and post PRK (2,3). While this fatty acid has not been evaluated specifically in diabetic patients, there is evidence that GLA metabolism is impaired in diabetes (4). Additionally, GLA (480 mg daily) has been shown in a placebo-controlled trial to improve diabetic neuropathy (5).

Figure1. Percent of diabetic and non-diabetic patients who filled prescriptions for ocular lubrication, stratified by age. The percent of diabetic patients prescribed lubrications was statistically significantly larger than the percent of non-diabetic patients (X2 test, P < .0001 for all age groups).

References

1. Kaiserman, et al. Dry eye in diabetic patients. Am J Ophthalmol 139:498-503, 2005.
2. Barbarino S, et al. Systemic linoleic and gamma-linolenic acid therapy in dry eye syndrome with an inflammatory component. Cornea 22:97-101, 2003.
3. Macri, et al. The effect of LA and GLA on tear production, tear clearance and on the ocular surface after PRK surgery. Graefes Arch Clin Exp Ophthalmol 241:561-6, 2003.
4. Mikhailidis DP, et al. The effect of DGLA on platelet aggregation and prostaglandin release, erythrocyte membrane fatty acids and serum lipids: evidence for defects in PGE1 synthesis and delta-5 desaturase activity in insulin-dependent diabetics. Diabetes Res 3:7-12, 1986.
5. Keen H, et al. Treatment of diabetic neuropathy with gamma-linolenic acid. The gamma-linolenic acid multicenter trial group. Diabetes Care 16:8-15, 1993.