In Chronic Kidney Disease, Retinal Parameters May Offer Visual Acuity Insight

Monitoring the parafoveal inner retinal thickness, peripapillary retinal nerve fiber layer (RNFL)-derived parameters, and ganglion cell complex (GCC)-derived parameters can help predict best-corrected visual acuity (BCVA) in patients with chronic kidney disease (CKD), according to research published Ophthalmology Therapy. However, gauging macular thinning via full retinal thickness, may not accurately estimate acuity.

This post hoc analysis looked at spectral domain optical coherence tomography (SD-OCT) images of 120 eyes from 120 patients (mean age 63.0±10.3 years) with CKD of at least stage 3 enrolled in 2 prospective studies , who were treated at a tertiary hospital in Taiwan, from August 2017 to July 2019. The participants were divided into 3 groups of 40 each by GCC defect severity; matched by sex, lens status, axial length, and other factors. Group 1 presented no defect, group 2 had a GCC defect parafoveally, and in group 3, defects reached beyond the parafoveal perimeter.

Mean best corrected visual acuity (BCVA) of patients in group 1 ( 0.076±0.101 logMAR) did not meaningfully differ from those in group 2 (0.100±0.127). In contrast, group 3 (0.196±0.191 logMAR) had a significantly worse BCVA than groups 1 and 2 (both P =.001). In linear regression analysis, 7 variables were largely associated with lower BCVA: peripapillary RNFL thickness, peripapillary RNFL defect present, parafoveal inner retinal thickness, and all GCC parameters — thickness, GCC global and focal loss volume, and defect reaching outside the parafovea (7 data points ranged from P =.009 to P <.001).

Conversely, central subfield retinal thickness (CRT), and parafoveal outer or full retinal thicknesses were not importantly linked to BCVA, thus macular thinning detected from full retinal thickness may be inadequate to assess acuity loss.

With multiple linear regression that adjusted for age, signal strength index, and other aspects, researchers found comparable results. Although, when including backward stepwise method for multiple linear regression, only 2 independent factors remained — age (coefficient 0.005, 95% CI 0.003 to 0.007, P <.001), and GCC defect spreading further than parafoveal boundaries (coefficient 0.079, 95% CI 0.021 to 0.138, P =.008).

When GCC defects reached outside the parafovea, visual acuity tended to be worse for both phakic (P =.006) and pseudophakic (P =.009) individuals. “Therefore, before cataract surgery, the extensiveness of GCC defects may provide useful information for the prediction of surgical outcomes, and for the selection of appropriate intraocular lens for patients with CKD,” according to the research team. Pseudophakic eyes trended older, but all 3 groups were age-matched.

The entire impact of ganglion cell loss on BCVA is still unknown — in glaucoma studies, central ganglion cells and vision have often been retained until later disease, or, an association between VA and GCC thickness was detected when change included the central papillomacular bundle. Other research indicates vision decline when structures are damaged beyond a tipping point. Current data suggests acuity worsens when central macular GCC loss is pronounced. 

Limitations of this study included a lack of microperimetry testing, and no information for fluid levels of patients undergoing dialysis. Also, results do not apply to those in disease classes the study excluded such as diabetic retinopathy, glaucoma, macular pucker, or retinal vein occlusion. A strength was careful matching among groups.