Dry eye linked to diabetes, decreased corneal sensation

"There is a very significant connection between diabetes and dry eye," said Dr. Gilbard, who is founder, chief executive officer, and chief scientific officer, Advanced Vision Research, Woburn, MA. "It all begins with the fact that we now know that elevated tear film osmolarity causes dry-eye ocular surface disease."

Connection with diabetes "Osmolarity can go up by either decreased tear production or increased evaporation, and production of tears can go down from either lacrimal gland disease, in flammation in the lacrimal gland such as we see in SjF6gren's syndrome, or anything that decreases corneal sensation. Just as irritated eyes tear more, eyes that are numb tear less," he said. "This is because intact cor neal sensation partially drives tear production."

While the links between diabetes, decreased corneal sensation, diabetic ret i nop athy, and dry eye seem clear, studies have produced conflicting results on the question of whether glycemic control plays a significant role in dry eye, Dr. Gilbard said.

How common is combination? Several studies have attempted to estimate the number of individuals with diabetes who also have dry eye symptoms, all finding a prevalence higher than in age-matched controls. The Canadian Dry Eye Epidemiology Study found 37% of diabetics have dry eye, while a German study by Seifart and Strempel found dry eye in 52.8% of diabetics (Ophthalmologe 1994;91:235-239).

A recent prospective study by Kaiserman et al., conducted in Israel's largest health maintenance organization, compared the prevalence of dry eye in a pro spec tive cohort of 22,382 diabetic patients over age 50 with that in the general population by examining their use of lubricant eye drops. They found that 20.6% of patients with diabetes used ocular lubrication for dry eye symptoms, compared with 13.8% of non-diabetic patients (Am J Ophthalmol 2005;139:498-503).

The findings of an association between diabetes and dry eye highlight the need for ophthalmologists to add another line of inquiry when a patient's history includes diabetes, Dr. Gilbard said.

"When we think about diabetes, we think about retina problems and retinopathy. We don't traditionally think about asking patients whether they have dry eye symptoms," he pointed out.

However, he continued, since studies suggest that decreased corneal sensation and an increase in dry eye correlate with diabetic retinopathy, clinicians need to ask diabetic patients whether they've experienced typical dry eye symptoms such as sandy, gritty eyes; irritation; or a burning sensation. They should also determine whether these symptoms, if pres ent, worsen as the day goes on, which is typical in dry eye, and is explained by the fact that tear film osmolarity increases as the day goes on.

Choice of treatments If patients have dry eye, there are many treatments to choose from, including drops, nutritional supplements, and punctal plugs.

Dr. Gilbard recommends Thera Tears lubricant eye drops (Advanced Vision Research), either preservative-free in single-use form, in a bottle with disappearing preservative, or in the liquid gel form, because they are hypotonic, effectively lowering elevated tear film osmolarity and removing the cause for dry eye irritation. The unit dose product with saturation dosing is particularly effective at lowering osmolarity quickly and providing rapid relief when used four times a day until symptoms are well controlled, he said.

"What you're doing is not just wetting the eye; you're rehydrating the tear film-ocular surface system and lowering tear film osmolarity," he explained.