How tilted optic discs may affect myopic eyes
Excerpted from page 53 of the January/February 2017 edition of AOA Focus.
The occurrence of tilted optic discs appears in about 1 to 2% of the population. While it is generally considered to be a benign and congenital—albeit uncorrectable—condition, a recent study in the journal Optometry & Vision Science took a closer look, using optical coherence tomography to compare differences between myopic eyes with and without tilted discs.
In the experiment, researchers examined the eyes of 60 highly myopic subjects.
The mean spherical equivalent refraction (the lens power of their glasses or contacts) of the subjects was 6.0. Twenty-one of the 60 subjects had tilted optic discs. Using optical coherence tomography, scientists compared retinal thickness and biometric parameters between eyes with tilted discs and those without. They found no difference in biometric parameters. There were some differences in macular nerve fiber layer thickness, but not in retinal nerve fiber layer thickness. The tilted disc group was shown to suffer from a greater degree of myopia than the non-tilted disc group.
A piece of the puzzle
"It is one of these situations where if you have a glaucoma suspect with tilted discs, you always wonder if there is an influence from the tilt that is actually creating an altered retinal nerve fiber layer artifact," says Mile Brujic, O.D., who practices in Ohio. "What this shows is that when you compare it to optic nerves in myopes that aren't tilted, there is no difference between the two. That tells us we can look at these tilted discs and, with a higher level of confidence, we can make better treatment decisions when we are doing optical coherence tomography on those individuals."
Dr. Brujic describes tilted disc syndrome as a variant-something that is recorded by an eye care professional, but is not considered a pathology. It occurs when the nerve enters the eye at an oblique angle rather than a perpendicular one. In his opinion, the findings of this study offer the most value to the 2 to 3% of the population who suffer from glaucoma.
"This study will not have much effect on how we manage myopia, but it will influence the way we interpret data for potential optic nerve head disease, glaucoma being one of them," he says.
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