Glaucomatous Damage Indicated By Inner Nuclear Layer, GCIPL Thinning

Reductions in macular inner nuclear layer (INL) and ganglion cell-inner plexiform layer (GCIPL) thicknesses may indicate glaucomatous damage in patients with open-angle glaucoma, according to findings published in Ophthalmic and Physiological Optics.

Investigators included patients with open-angle glaucoma (n=271; mean age, 64.44 years; 109 women) and healthy control individuals (n=548; mean age, 50.36 years; 300 women) from a single center in the study. All study participants underwent comprehensive eye examinations which included optical coherence tomography (OCT). The primary outcomes for this study were variations in INL, GCIPL, and outer retinal complex (ORC) thicknesses between groups and the potential associations between layer thickness changes and glaucoma outcomes.

In the multiple linear regression analysis, GCIPL thickness was associated with age (P <.0001), refractive error (P =.02), and sex (P <.0001). For INL and ORC thicknesses, age and gender were negatively correlated (all P ≤.0006) and refractive errors were positively associated (both P ≤.003). Overall, the maximum deviation in retinal thickness due to age was 3.13% for GCIPL, -2.26% for INL, and -0.54% for ORC.

In the cluster analysis of glaucoma deviation maps, at least 2 clusters were identified. Patients who did not have visual field defects according to Hodapp-Parrish-Anderson criteria had a ring-like pattern of changes in the CGIPL without a corresponding change in the INL or ORC, likely indicating early-stage disease. Patients with inferior visual field defects, however, tended to present with superior GCIPL defects and those with superior visual field defects exhibited inferior GCIPL defects, corresponding with worsening mean deviation.

Corresponding ORC thickness increases accompanied GCIPL thickness reductions, and these correlations indicated a negative association with glaucoma severity (mean deviation: r, 0.256; pattern standard deviation: r, -0.207; both P <.0001). Similar associations were observed for INL and ORC deviations. However glaucoma severity was correlated only with mean deviation (r, 0.149; P =.01) and not with pattern standard deviation (r, -0.041; P =.50).

“Colocalized reductions in INL thickness may be observed in conjunction with reduced GCIPL thickness measurements, and a weak but significant correlation suggests that greater reductions in INL thickness may occur with increasing glaucoma severity,” according to the study authors. “By contrast, no consistent change in the ORC was observed. These findings could support the notion that trans-synaptic retrograde degeneration may occur in glaucoma, although not extending past the INL.”

Study limitations include a single center design and a limited refractive error range in participants with glaucoma.