Dry Eye Dx and Tx

Diabetes and the Dry Eye

BY WILLIAM TOWNSEND, OD, FAAO

Huang et al (2009) projected that during the 25 years between 2009 and 2034, the number of Americans with diagnosed and undiagnosed diabetes will increase from 23.7 million to 44.1 million. Retinopathy is a commonly recognized ocular complication of diabetes, but many people are unaware of the impact of diabetes on the ocular surface.

Diabetes’ Role in Dry Eye

The literature suggests that the severity of the diabetes influences its contribution to dry eye development. Wang and coworkers (2010) reported that diabetics without complications have no increased risk for developing dry eye, whereas diabetes with complications significantly elevates this risk. The same study found that hyperlipidemia—a frequent finding in diabetes characterized by moderately elevated triglyceride levels, reduced high-density lipid (HDL) cholesterol values, and small, dense low-density lipid (LDL) particles—is also a risk factor for developing dry eye. Hyperlipidemia is associated with insulin resistance and usually precedes the onset of diabetes (Solano et al, 2006).

Tear proteins are important to the health of the ocular surface, but studies show that they are altered in diabetic and non-diabetic dry eye sufferers (Chiva, 2011). Studies have recently revealed that diabetic patients who do not suffer from dry eye have tear proteins that are dissimilar in number and intensity from those of non-diabetic subjects (Grus et al, 2002). Alterations in the tear proteins of diabetics correlate with the duration of diabetic disease and steadily increase over time (Grus et al, 1998).

One possible explanation for increased dry eye in diabetics is neuropathy. An intact neurological system is crucial to maintaining the ocular surface. In patients who have mild, moderate, and severe neuropathy, the integrity of the “functional unit” is compromised, leading to ocular dryness (Bansal et al, 2006). Cousen et al (2007) demonstrated that diabetics have reduced basal tear production and threshold corneal sensitivity attributed to diabetic neuropathy. Saini and Mittal (1996) determined that diabetics who have normal fundi typically have normal corneal sensitivity, but those who have diabetic retinopathy demonstrated some degree of decreased sensation. These studies collectively suggest that routine screening for corneal hypoesthesia could be valuable in the dry eye workup of diabetic patients and may also be a predictor of the state of the retina.

Meibomian gland dysfunction (MGD) is strongly associated with and is a primary cause of dry eye. Viso et al (2012) reported that after controlling for age and gender, asymptomatic MGD was more than twice as common in individuals who have diabetes. There was no increased prevalence of symptomatic MGD in diabetic patients. This study suggests that we should evaluate patients who have diabetes for MGD and dry eye, even if they are asymptomatic.

Children are Affected, Too

You might assume that diabetic children have no issues with ocular dryness. Akinci et al (2007) evaluated 104 children with type 1 diabetes and 104 age- and sex-matched controls. They found that 15.4 percent of diabetic children reported dry eye symptoms, versus 1.9 percent of the control subjects. Dry eye signs were identified in 7.7 percent of diabetic children; by comparison only 0.96 percent of controls showed evidence of dry eye. A definitive dry eye diagnosis was made in 7.7 percent of diabetic children, while none of the control subjects were diagnosed. This suggests that all children who have diabetes should be evaluated for signs and symptoms of ocular dryness. CLS

For references, please visit www.clspectrum.com/references.asp and click on document #204.