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Study shows impact of diabetic corneal nerve damage

24/01/2018By Matthew Woodley
Diabetes-related corneal nerve damage could be an early indicator of similar issues in other parts of the body, and may also lead to complications following cataract and refractive surgery, an Australian literature review has found.

The 18-month review, led by UNSW School of Optometry and Vision Science (SOVS) senior lecturer Dr Maria Markoulli, was conducted to determine research into the effect diabetes has on the front of the eye, specifically the cornea and tear film. She said the review contained ‘clinical pearls’ for treating diabetic patients, and that it also highlighted an area of study that, until recently, had been somewhat neglected.

“We’re very familiar with the impact that diabetes has on the back of the eye, because that can obviously have very sight-threatening consequences. But we don’t often talk about what diabetes can do to the front of the eye,” Markoulli told Insight.

"You can see these changes before they start to show up anywhere else in the body by having a look at the nerves in the cornea."
Dr Maria Markoulli, UNSW School of Optometry and Vision Science

“For example, diabetes affects the nerves of the cornea, along with the peripheral nervous system, but these changes happen first in the cornea before they happen elsewhere in the body.”

Markoulli said this could have important consequences for diabetic patients, especially those at risk of peripheral nerve damage.

“At the moment, if someone has diabetes and you want to test if they’ve started to lose some of the peripheral nerves – such as sensitivity in the fingertips or the feet – its really hard to detect, and it’s often not detected until its too late,” she explained.

“By that stage it’s hard to treat and in really extreme circumstances that can lead to patients having their limbs amputated. But, you can see these changes before they start to show up anywhere else in the body by having a look at the nerves in the cornea.”

However, despite providing a helpful surrogate measure for potential peripheral nerve damage, it can also have serious vision-related consequences. According to the review, diabetic patients with corneal nerve damage are more susceptible to ocular surface diseases including dry eye and corneal ulceration, while it can also lead to complications associated with surgery.

Importantly, due to the heightened risk of post-operative corneal complications in various types of ocular surgery, Markoulli said clinicians needed to make diabetic patients aware of the potential hazards before they underwent any procedure.

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“If I was seeing a patient who was in this situation, I’d be making sure they knew that there was a risk possibly. I’d then be monitoring them very closely after surgery to make sure this didn’t occur,” she said.

“There is an increased risk of infections in diabetes and we think that’s partly because of the reduced number of nerves in the cornea, as well as the change in the balance of the protective proteins within the tear film.

“The combination of these factors, we think, makes the cornea more fragile and so more prone to injury. These ulcers can take quite a long time to heal as well and when you’ve got an open wound, you’ve got more chance of infection.”

Markoulli said the review provided more potential avenues for research that the group would possibly pursue some in the future. The review was published in the January 2018 issue of The Ocular Surface.

More reading: Full study.

Image courtesy: Flickr | Community Eye Health


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