High myopia linked with low levels of thinning in retinal nerve fiber layer
Key takeaways:
- Patients with high myopia experienced the least thinning in retinal nerve fiber layer.
- The findings could be beneficial for diagnosing patients with glaucoma in high myopia.
A cohort of patients with high myopia experienced significantly low levels of thinning in the peripapillary retinal nerve fiber layer in the temporal quadrant and macular retinal nerve fiber layer, according to a pilot study.
The findings, published in PLoS One, additionally indicated that biomarkers may be beneficial for diagnosing glaucoma among patients with high myopia.
“Myopia is a growing public health problem predicted to affect 5 billion people worldwide, while high myopia is expected to affect 9.8% of the world population by 2050,” Agne Markeviciute, MD, from the department of ophthalmology at Medical Academy at Lithuanian University of Health Sciences, and colleagues wrote. “The impact of myopia is broad and highly significant, yet the definitions used to grade myopia varies between studies and is often without consensus.”
Researchers sought to examine the differences in structural parameters among 42 patients (71.43% women; 100% white) with open-angle glaucoma (n = 14), high myopia (n = 14) and both conditions concurrently (n = 14).
They assessed mean peripapillary retinal nerve fiber layer (RNFL) thickness; RNFL thickness in superior, temporal, inferior and nasal quadrants; macular ganglion cell complex and its layers; vessel density of optic nerve head; and macula.
According to study results, patients with both diseases experienced significantly lower thickness of mean peripapillary RNFL (89 m; P = .021), temporal quadrant (64.5 m; P = .001) and inferior quadrant (107 m; P = .025) compared with those with only open-angle glaucoma or high myopia.
Researchers additionally found that the macular RNFL appeared thinnest among patients with both diseases concurrently (38.5 m; P < .001).
“The observed decrease in peripapillary retinal nerve fiber layer thickness of the temporal quadrant, macular retinal nerve fiber layer thickness, the decrease of macular vessel density at the inferior quadrant and decrease in vessel density of the optic nerve head temporal quadrant in deep capillary plexus could be beneficial for diagnosing glaucoma in high myopia,” the researchers wrote.
Perspective
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The standard OCT measurements of the RNFL and retinal ganglion cell (RGC) layers used for the detection of glaucoma are well-known to show diminished values in highly myopic patients, making it difficult to rely on the diagnostic value in this group. This pilot study indicates that the papillomacular bundle and macular measurements may be more relevant when attempting to detect glaucomatous disease in patients with axial elongation. Other values such as neuro-retinal rim, RGC thickness asymmetry between superior and inferior regions, and vascular density values in the macula and peripapillary region may also help discriminate glaucomatous disease in high myopia from anatomically thin tissue from myopia alone.
The measurements in this study were obtained from customized algorithms and differ from the analyses provided on commercial instruments. For now, the use of similar parameters should be approached with caution. Also, it would be helpful to stratify these differences across various stages of glaucoma to determine at what level of disease these values differentiate into thinning due to glaucoma and not axial myopia alone. Nonetheless, this pilot study provides compelling evidence for further investigation in the use of measurements in the temporal and macular regions in highly myopic patients suspected of having glaucoma.
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