Issue: May 1, 2005

ByJeanne Gonzalez

May 01, 2005

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Patients with diabetes at risk for dry eye syndrome

Decreased corneal sensitivity may be responsible, and patients may not be aware that they have dry eyes.

Issue: May 1, 2005

ByJeanne Gonzalez

Studies have shown a correlation between diabetes mellitus and dry eye syndrome. Several studies cite poor metabolic control, neuropathy and advanced retinopathy as risk factors for dry eye. Potential therapies include nutritional supplementation with vitamins C and E, experts say.

Many ophthalmologists are not aware of the relationship between the two conditions, said Ernest W. Kornmehl, MD, a corneal specialist in Massachusetts.

Worse, many diabetic patients may not be aware they have dry eye because the syndrome seems to be linked to loss of corneal sensation.

“Diabetes mellitus causes decreased corneal sensation. It’s similar to contact lenses. The reason many of these patients’ eyes are dry is because of the [interruption of the] feedback loop to the lacrimal gland. When you have decreased corneal sensation, there’s decreased tear production,” Dr. Kornmehl said in an interview with Ocular Surgery News.

Diabetes mellitus affects the nervous system, causing decreased sensation. Patients with diabetes may experience decreased sensation in their hands and feet, Dr. Kornmehl said. If the nonmyelinated nerves leading into the corneal epithelium are affected by the disease, decreased sensation can be experienced there as well, he said.

There are no epidemiological studies showing what percentage of the population with diabetes may have dry eye, said Stephen C. Pflugfelder, MD, a corneal specialist in Houston.

“There appears to be an increased incidence” of dry eye in patients with diabetes, Dr. Pflugfelder said. “The risk is greater with poorly controlled type 1 diabetes. [The incidence] increases if there is diabetic retinopathy.”

Dr. Pflugfelder said he believes the cause is related to sensory and autonomic neuropathy.

“We have reported that tear production decreases as corneal sensitivity decreases due to diabetes or other causes,” he said.

Dr. Pflugfelder suggested checking patients with diabetes for any changes in the corneal epithelium, especially punctate epitheliopathy.

Increased need for lubrication

In recent years, several studies have found decreased tear production in patients with diabetes.

Recently, researchers at the Hadassah Hospital in Jerusalem studied a large cohort to observe whether patients with diabetes required more ocular lubrication. Igor Kaiserman, MD, MSc, Mpa, and colleagues observed that keratoconjunctivitis sicca or keratitis sicca was more common in patients with diabetes. The researchers found that dry eye in patients with diabetes was correlated with their glycemic control.

The researchers evaluated 159,634 patients older than 50 years in 2003. Among that population, 22,382 (14%) had diabetes.

This large-scale study was the first to investigate artificial tear consumption in patients with diabetes, Dr. Kaiserman told OSN.

“A significantly higher percentage of diabetic patients received ocular lubrication, compared with nondiabetic patients. … A similar significant difference was prominent between diabetic and nondiabetic patients aged 60 to 89 years who were frequent users of ocular lubrication,” the researchers said.

The researchers performed HbA1c tests to measure glycemic control. They were able to correlate poor glycemic control with the increased need for ocular lubrication; 20.6% of patients with diabetes used ocular lubrication as opposed to 13.8% of otherwise healthy patients (P < .001),="" the="" researchers="">

“Since about 5% to 10% of adults are diabetic, the extent of dry eyes caused by diabetes is quite substantial, especially in the older population,” Dr. Kaiserman said in an interview. “We suggest asking diabetics about dry eye symptoms, examining tear film breakup time and Schirmer tests and treating them accordingly.”

Be proactive when treating patients with diabetes

Ophthalmologists should examine the tear meniscus, check for keratitis and carefully evaluate the conjunctival staining of patients with diabetes, said Ernest W. Kornmehl, MD.

Because of decreased corneal sensitivity, patients with diabetes mellitus may be unaware of dry eye symptoms.

“That’s why you have to do a thorough examination. They won’t feel the foreign body sensation or aching pain like most of our patients do. It’s up to the ophthalmologist to ask about increased redness and to look for particular signs on the examination,” Dr. Kornmehl said.

Ophthalmologists should also be aware that factors such as administration of antihistamines, or postmenopausal age in women, might exacerbate dry eye in patients with diabetes, Dr. Kornmehl said.

“We can’t forget that they’re also prone to all the other reasons for dryness, so it may be compounded significantly by these other things,” he said.

In light of studies demonstrating the link between diabetes and dry eye, ophthalmologists should ask patients about their HbA1c levels and ensure proper glycemic control. The longer the patient has had diabetes, the greater their decrease in sensation, Dr. Kornmehl said.

Decreased tear production

Researchers at the Chonnam National University Medical School and Hospital in Korea observed that diabetes progression was correlated with tear film and ocular surface changes.

“We think that diabetic patients with poor metabolic control, neuropathy and advanced stage of retinopathy should be examined for tear film and ocular surface changes,” said K. C. Yoon, MD, and colleagues in a study published in the Korean Journal of Ophthalmology.

Dr. Yoon and colleagues conducted a study in 94 eyes of 47 patients with type 2 diabetes mellitus. Thirty healthy patients (60 eyes) served as a control group. Researchers evaluated the degree of keratoepitheliopathy and corneal sensitivity and performed tear breakup time tests, Schirmer tests and conjunctival impression cytology.

They observed that patients with diabetes had more severe keratoepitheliopathy and corneal sensitivity. Tear breakup time and tear secretion were significantly reduced in patients with diabetes. Conjunctival impression cytology showed increased conjunctival squamous metaplasia and decreased goblet cell density in patients with diabetes. The researchers said the degree of severity also corresponded with the patients’ stage of diabetic retinopathy.

Photocoagulation and dry eye

A large study by H. Y. Li, MD, and colleagues in Beijing showed that the deterioration of tear film production was related to the severity of diabetic retinopathy and its treatment.

“Dry eye score had a good correlation with diabetic retinopathy and photocoagulation (P < .01),="" but="" was="" poorly="" correlated="" with="" age,="" gender,="" insulin,="" duration="" of="" diabetes="" mellitus="" and="" metabolic="" control="">P > .05),” the researchers said.

The researchers evaluated 111 patients with diabetes, and 100 patients served as controls. The patients were separated into three groups according to the degree of diabetic retinopathy: no retinopathy, background retinopathy and proliferative retinopathy.

Patients with proliferative retinopathy had higher scores for dry eye, the researchers found. Schirmer and tear breakup tests showed significantly decreased tear production in these patients.

Patients were also divided according to whether they had undergone photocoagulation or not. Patients who had undergone photocoagulation also had higher dry eye scores and faster tear breakup times than patients who had not undergone photocoagulation, but the Schirmer test scores were similar between the groups.

Risk factors

Poor metabolic glucose control, panretinal argon laser photocoagulation and proliferative retinopathy were found to be risk factors for dry eye in patients with diabetes by M. Ozdemir, MD, and colleagues in Turkey.

“Tear film and Schirmer test values were significantly lower in diabetic patients compared with control subjects,” the researchers said.

The researchers evaluated 41 patients with diabetes and 20 healthy patients. They performed an ophthalmic examination, tear breakup time, Schirmer testing, fluorescein dye and rose bengal staining. Patients also answered a questionnaire eliciting symptoms.

More patients with diabetes had abnormal fluorescein and rose bengal staining scores (P < .001),="" the="" researchers="" said.="" abnormal="" tear="" function="" tests="" were="" also="" associated="" with="" the="" risk="" factors="" investigated.="">

“These patients should be followed more carefully, and should be referred to an ophthalmologist when required,” the study authors said.

Vitamin supplements

A 2002 study observed that vitamins C and E supplementation in diabetic patients was effective in protecting against oxidative stress and increased levels of nitric oxide (NO), two factors that aggravate dry eye.

V. Peponis, MD, and colleagues at the University of Athens, said previous research has shown that oxidative stress increases free radical activity, likely because of ultraviolet exposure. Oxidative stress is defined as an imbalance between free radical production and the antioxidant effect during tissue injury. NO is involved in ocular inflammation, they noted.

The researchers observed that diabetic patients who took vitamins C and E had reduced oxidative stress and decreased NO levels. They postulated that the supplements have qualities that are protective against free radicals, helping to preserve the epithelium.

“We suggest that the antioxidant activity of these compounds results in a decrease in the oxidative burden in the ocular surface that could lead to elimination of NO and its cytotoxic effects,” the researchers said.

For Your Information:

Ernest W. Kornmehl, MD, can be reached at 62 Walnut St., Wellesley, MA 02481; 781-237-3366; fax: 781-237-6611.

Stephen C. Pfl ugfelder, MD, can be reached at Baylor Vision, Baylor College of Medicine, Dept of Ophthalmology, 6550 Fannin, Suite 1501, Houston, TX 77030; 713-798-5940; fax: 713-7981457.

Igor Kaiserman , MD, MSc, Mpa, can be reached at the Department of Ophthalmology, Hadassah University Hospital, Jerusalem, Israel; 972-50-7784764; fax: 972-26416242; e-mail: Igor@Dr-Kaiserman.com.

Reference:

Kaiserman I, Kaiserman N, et al. Dry eye in diabetic patients. Am J Ophthalmol. 2005;139(3):498-503.
Yoon KC, Im SK, Seo MS. Changes of tear film and ocular surface in diabetes mellitus. Korean J Ophthalmol. 2004;18(2):168-174.
Li HY, Pang GX, Xu ZZ. Tear film function of patients with type 2 diabetes. [Abstract in English, article in Chinese.] Zhongguo Yi Xue Ke Xue Yuan Xue Bao. 2004;26(6):682-686.
Ozdemir M, Buyukbese MA, et al. Risk factors for ocular surface disorders in patients with diabets mellitus. Diabetes Res Clin Pract. 2003;59(3):195-199.
Peponis V, Papathanasiou M, et al. Protective role of oral antioxidant supplementation in ocular surface of diabetic patients. Br J Ophthalmol. 2002;86:1369-1373.

Jeanne Michelle Gonzalez is an OSN Staff Writer who covers all aspects of ophthalmology, specializing in practice management, regulatory and legislative issues. She focuses geographically on Latin America.