How diabetes affects contact lens wear

Mass media and medical publications have been warning for years that the incidence of diabetes is rising rapidly and predicting a “health catastrophe” in which more than 10 percent of the U.S. population would be living with this disease.¹ The future looks even worse with statistics showing that the rate of prediabetes has been climbing even faster than predicted² and that without significant lifestyle changes, most people with prediabetes condition will develop type 2 diabetes within 10 years.^3,4

If diabetes-related problems are soon to become the reason for nearly 90 percent of patient visits to U.S. physicians, as has been suggested, then optometrists will be seeing many more of these cases.⁴ But optometrists should be expanding their management beyond checking patients for signs of diabetic retinopathy.

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Diabetes and dry eye

“There are distinct evidence-based reasons why we should be looking at the ocular surface,” said Milton M. Hom, OD, FAAO, who is in private practice in Azusa, CA, and a member of Optometry Times Editorial Advisory Board. He spoke at the SECO 2016 meeting in Atlanta.

According to Dr. Hom, studies have shown that half of patients with type 2 diabetes also have dry eye symptoms and that the higher the hemoglobin A1C (HBA1C) values, the higher the rate of dry eye syndrome.⁵

The association may be linked to automatic neuropathy, which decreases corneal sensitivity and affects feedback mechanisms and lacrimal gland secretion. In addition, hyperglycemia impairs inflammatory cell function and raises the risk of corneal infection.

Patients with diabetes are also at risk of endothelial cell loss, impaired sensitivity, and recurrent corneal abrasions.

“The diabetic endothelium is morphologically abnormal,” Dr. Hom said.

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To better address the host of eye-related risks associated with diabetes, Dr. Hom divides his management of these patients into two categories addressed in separate visits: one for the standard diabetic exam and one for ocular surface problems. During the ocular surface exam, measurement of HBA1C is standard. These readings can offer a more accurate picture of the disease status than glucometer readings because they provide a snapshot of the amount of glucose in the blood over the past two to three months.

Currently, an A1C level of 6.5 percent or higher indicates diabetes.⁶ This is lower than the value used in the past, and it’s likely to be reduced again in a few years, according to Dr. Hom. The rationale for adjusting the numbers is early intervention and better treatment outcomes

“That’s going to increase the number of patients with diabetes that you’re seeing,” he said.

Next: Contact lenses and diabetes

Contact lenses and diabetes

Patients who have diabetes and wear contact lenses are particularly challenging for optometrists. The susceptibility of patients with diabetes to corneal erosions, occurring at multiple places on the cornea,⁷ must be a factor in recommending a lens and ongoing patient management, Dr. Hom said.

Not every patient with diabetes is a good candidate for contact lenses, based on A1C levels and ocular surface health. But if contact lenses seem to be appropriate, the best option may be daily disposable contact lenses.⁸

While there is no absolute upper limit of A1C levels that prohibits fitting for contact lenses, a value in the 7 percent to 8 percent range warrants caution, and a patient with an A1C level of 10 percent ordinarily would not be a good candidate. ⁸

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“I will fit patients with high A1C levels with daily disposable lenses, but I watch them very, very closely, and I tell them that if they start experiencing abrasions, they will need to make some changes,” Dr. Hom said.

Every case must be considered individually rather than solely on the basis of a test result. He has seen patients with high A1C values but no evidence of ocular surface disease.

Every optometrist has patients who refuse to wear disposable lenses, even against the doctor’s recommendation. In these instances, tell diabetic patients they can wear reusable lenses but should use a hydrogen peroxide-based care system to reduce the risk of ocular surface problems, Dr. Hom said.

Next: Keep a mindful eye

Keep a mindful eye

Vigilance with patients who have diabetes requires not only monitoring for retinopathy, corneal abrasions, and contact lens-related complications but corneal ulcerations, Dr. Hom said. Standard treatment for corneal ulcers relies on initial treatment with an antibiotic, followed by an added steroid. But this could be counterproductive in patients with diabetes.

“Steroids is increase the amount of glucose, especially in the liver. If the patient already has diabetes, you can increase blood sugar by putting him on steroids,” Dr. Hom said.

Nutritional support is another avenue for advising patients with diabetes, which to a great extent is a lifestyle disease.

“The evidence is pointing toward using omega-3 fatty acids to help control both dry eye and diabetes,” Dr. Hom said.

However, using omega-3s may also cause complications such as a higher risk of prostate cancer or a decrease in clotting factor.⁹ They are not a miracle product that will benefit all patients.

Today, many nutritional supplements contain both omega-3 and omega-6 fatty acids, which have opposite effects, with the goal of stimulating an anti-inflammatory pathway. But there is little evidence on the ideal ratio of omega-6 to omega-3 or the best way to modify the pathway, despite the opinions presented in some papers, Dr. Hom said.

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Most optometrists who recommend omega-3s or combination products know that they help some patients but not others.

“The reasons why omegas fail is because we have absolutely no idea what the omega-3 and omega-6 count is in our patients,” he said. ”The only way to know is to take blood samples and measure the fatty acid content.”

When doctors blindly recommend a supplement without baseline information, the patient may end up with too much or too little omega-3 or omega 6, producing little or no benefit and potentially some harm.

Answers about omega-3s may come from the ongoing DREAM (Dry Eye Assessment and Management Study) study, the first study on dry eye sponsored by the National Institutes of Health (NIH). In this multisite study, patients are assigned to either omega-3 supplements (2,000 mg EPA and 1,000 mg DHA per day) or placebo; the primary outcome measure is mean change in Ocular Surface Disease Index score from baseline at 6 and 12 months in the primary trial and from 12 months to 18 and 24 months in the extension study. Blood samples will be taken at the beginning and end of the study. The estimated study completion date is April 2017, according to data at clinicaltrials.gov.

Help for diabetic patients may also come from an unorthodox source. Google announced in 2014 that it is developing a smart contact lens that could measure glucose levels in tears using a miniature wireless chip and glucose sensor. Google is partnering with Alcon to bring the project to the market in the next few years.

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References

1. Ghasemi H, Gharebaghi R, Heidary F. Diabetes as a possible predisposer for blepharitis. Can J Ophthalmol. 2008 Aug;43(4):485.

2. Centers for Disease Control and Prevention. Number of Americans with diabetes projected to double or triple by 2050. Available at: http://www.cdc.gov/media/pressrel/2010/r101022.html. Accessed 4/18/16.

3. Centers for Disease Control and Prevention. Prediabetes. Available at: http://www.cdc.gov/diabetes/basics/prediabetes.html. Accessed 4/18/16.

4. Bar RS. Lifestyle changes could stop tsunami of diabetes cases. Des Moines Register. 2011 May 24:11A.

5. Seifart U, Strempel I. The dry eye and diabetes mellitus. Ophthalmologe. 1994 Apr;91(2):235-9.

6. American Diabetes Association. Diagnosing diabetes and learning about prediabetes. Available at: http://www.diabetes.org/diabetes-basics/diagnosis/. Accessed 4/18/16.

7. Rosenberg ME, Tervo TM, Immonen IJ, Müller LJ, Grönhagen-Riska C, Vesaluoma MH. Corneal structure and sensitivity in type 1 diabetes mellitus. Invest Ophthalmol Vis Sci. 2000 Sep;41(10):2915-21.

8. Orsborn G, Chous AP, Gelb K, Hom MH, Mitchell B, Ventocilla M. Managing contact lens wear in patients with diabetes. Advanced Ocular Care. 2014 Nov/Dec;5(8): 52-55.

9. Hom MM. Diabetes and dry eye: The forgotten connection. Rev Optom. Available at: http://www.reviewofoptometry.com/continuing_education/tabviewtest/lessonid/106952/. Accessed 4/19/16.