Purpose:
To evaluate the structure of the outer retina in several retinal diseases and assess its correlation with visual acuity.
Methods:
A cross-sectional study was performed. Spectral domain optical coherence tomography (Heidelberg OCT) scans of 160 eyes of 80 patients. Retinal pathologies included diabetic retinopathy with macular edema, retinal vein occlusion, age-related macular degeneration, epiretinal membrane, dome-shaped macula, macular foveoschisis, central serous retinopathy and vitreomacular traction.The images were graded with Adobe Photoshop CS3. The external limiting membrane (ELM), inner segment and outer segment (IS/OS) of the photoreceptors, and outer photoreceptor border were manually delineated to evaluate integrity and regularity of the layers. If a disruption was found in any of the layers, the length of the defect was measured in pixels. Thickness of the outer nuclear layer (ONL) and outer plexiform layer (OPL) were also recorded. After grading the images, they were subdivided by the topographic changes and then correlated with the visual acuity.
Results:
The visual acuity varied from 20/20 to HM. Irregularities and discontinuity of the retinal layers were variable and they showed a statistically significant association (p<0.05) with reduced visual acuity. Thickness of the ONL also demonstrated high correlation with visual acuity. The highest correlation was found with the IS/OS boundary and the ELM. The abnormalities in the retinal layers were seen in 85% of the cases, regardless of the clinical diagnosis.
Conclusions:
Spectral domain OCT enables the study of the anatomical structure of the retina and closely reflects a histological section. Outer retina abnormalities, especially in the IS of the IS/OS boundary and the ELM, are associated with poorer visual acuity.
Keywords: retina: distal (photoreceptors, horizontal cells, bipolar cells) • macula/fovea • comparative anatomy