High Myopia Linked to Retinal Layer Thinning

High myopia is associated with thinning of numerous retinal parameters that are seen in both individuals with glaucoma and those with suspected glaucoma, indicating that clinicians should consider refractive status in those with suspected glaucoma, a report in the Journal of Glaucoma suggests. 

A retrospective chart review shows the spectrum of myopia in people with suspected glaucoma. Investigated evaluated the relationship between spherical equivalent and measurements of ganglion cell-inner plexiform layer (GCIPL), RNFL, and optic nerve head (ONH) parameters, in addition to determining which parameters most accurately reflect myopic change. 

The total cohort included 76 eyes from 76 adults with suspected glaucoma from the New England Eye Center at Tufts Medical Center in Boston, Massachusetts, between October 2019 and February 2020. Suspected glaucoma was defined as at least 1 eye with intraocular pressure (IOP) greater than 21 mm Hg or an optic disc with clinical glaucoma signs, or both. 

Twenty-seven, 25, and 24 eyes were included in the low, moderate, and high myopia groups, respectively. These groups were comparable across baseline characteristics, with the exception of spherical equivalent (-1.71±0.74 D, -4.16±0.91 D, and -8.27±2.43 D in each group, respectively). 

Four cases of suspected glaucoma were diagnosed based on the presence of ocular hypertension alone; 93.4% of cases were diagnosed through clinical findings alone, and 1.3% (1 patient) was diagnosed on both ocular hypertension and clinical findings. In each myopia group, 2, 1, and 1 eye, respectively, had elevated IOP only, while 24, 24, and 23 eyes demonstrated only clinical findings, with 1 eye having both. 

In the high myopia group, all retinal nerve fiber layer parameters, excluding temporal, were significantly thinner compared with those in the low and moderate myopia groups, with no statistically significant differences were noted between the low and moderate myopia groups for any retinal nerve fiber layer parameters. Disc area and cup volume were the only ONH parameters with a significant decrease in the moderate and high myopia groups.

The high myopia group demonstrated significantly thinner GCIPL across all parameters, compared with the low and moderate myopia groups, with the exception of supertemporal GCIPL in the moderate group, and with the exception of inferonasal GCIPL in the low myopia group, there were no statistically significant differences between the low and moderate groups for any GCIPL parameters. 

Across all patients, the strongest associations for RNFL, ONH, and GCIPL parameters — superior RNFL (r₁ = 0.526, β = 2.270), cup volume (r₁ = 0.372, β = 0.017), and minimum GCIPL (r₁ = 0.547, β = 2.026; P < 0.05 for all) — were all “particularly weak” but statistically significant.

Area under the curve values for RNFL parameters, excluding temporal RNFL, demonstrated a “statistically significant ability” to differentiate high myopia from lower myopia.

Study limitations include the use of spherical equivalent rather than axial length, the possible, inadvertent inclusion of more participants with refractive rather than axial myopia, and a lack of a control group for those with myopia. 

Nuances in OCT parameter measurements previously shown to occur in patients with myopia and glaucoma also occur in patients with myopia who are glaucoma suspects, according to the researchers. “Furthermore, our study reveals that nontemporal RNFL and nontemporal GCIPL parameters are comparable in their utility to reliably distinguish thinning in glaucoma suspects.” 

Reference

Miller GD, Abu-Qamar O, Salim S. Evaluation of retinal nerve fiber layer, ganglion cell-inner plexiform layer, and optic nerve head in glaucoma suspects with varying myopia. J Glaucoma. 2021;30(5):e213-e221. doi:10.1097/IJG0000000000001834