Correlating optical coherence tomography biomarkers with visual acuity in nigerian retinitis pigmentosa patients

Background: Spectral Domain Optical Coherence Tomography (SD-OCT) has been used for imaging retinitis pigmentosa (RP) eyes and provides useful information on microstructural changes.

Aim: To review SD-OCT findings and correlate the central foveal thickness (CFT), outer nuclear layer (ONL), external limiting membrane (ELM), and ellipsoid zone (EZ) with visual function in nonsyndromic RP eyes.

Patients and methods: A multicenter, retrospective review of records from consecutive eyes diagnosed to have RP. Biodata, systemic disease, visual acuity, lens status, intraocular pressure, and SD-OCT images were examined. The CFT was categorized into normal (250-299 microns), atrophic (0-249 microns), and edematous (≥300 microns). The ONL, ELM, and EZ within the subfoveal area was assessed and rated as normal, reduced (if less than normal), or absent (if missing). The status of these biomarkers was correlated with visual acuity and statistical analysis performed using Pearson Chi², P < 0.05. In addition, the vitreomacular interface was examined for the presence of vitreomacular traction (VMT), vitreomacular adhesion (VMA), and epiretinal membrane (ERM).

Results: Fifty-two RP eyes of 27 patients had SD-OCT images that were used for study analysis. There were 17 males and 10 females; 52% of participants were between 31 and 50 years (age range: 22-77 years). An atrophic retina was the most common finding in 42 eyes (81%); the average CFT in the atrophic group was 175 microns (range: 111-245 microns). There were three eyes with cystoid macular edema, and seven eyes were normal. For the OCT biomarkers, a reduction in ONL and ELM occurred in 69% and 46% of eyes, respectively, while an absence was the most common EZ finding (in 50% of eyes). There was a significant correlation between the presence or absence of the three biomarkers and presenting vision: ONL, ELM, and EZ with P values of 0.000, 0.006, and 0.011, respectively. The CFT had no significant correlation with vision; P = 0.522. Other findings on OCT include ERM 17%, VMA 6%, and VMT 2%.

Conclusion: This report supports the notion that OCT image reporting on physical retinal structure in RP eyes can be used to predict disease effects on vision. A prospective study to better quantify the degree of structural change and correlate with the degree of functional loss is required for RP gene types in Nigerians and black Africans.