Correlation Between Visual Function and Photoreceptor Inner/outer Segment Junction in Patients with Retinitis Pigmentosa

Purpose: To determine whether a significant correlation exists between the visual acuity or foveal thickness and the status of the inner and outer segment junction (IS/OS) of the photoreceptor in patients with retinitis pigmentosa (RP).

Methods: Three hundred eyes of 163 patients with RP were examined with the optical coherence tomography (OCT). The IS/OS appeared as a distinct, highly reflective line just vitread of the retinal pigment epithelium in the OCT3 images. The IS/OS line was graded into three groups. The correlations between the grade of the IS/OS and age, best-corrected visual acuity (BCVA), and central foveal thickness (CFT) were determined.

Results: Grade 1 included 93 eyes (31.0%) in which an IS/OS line was not seen, Grade 2 included 67 eyes (22.3%) with an abnormal IS/OS, and Grade 3 included 140 eyes (46.7%) with a normal IS/OS. The correlation between the IS/OS grade and age was not significant (P=0.5536). The IS/OS grade was significantly correlated with BCVA and CFT (both P<0.0001). The BCVA was significantly better in Grade 3 eyes than Grades 1 and 2 (both P<0.0001). The CFT was significantly thinner in Grade 1 eyes than in Grades 2 and 3 (both P<0.0001). In Grade 3, the mean length of the IS/OS was 2.51+/-1.42 mm (+/-SD). The length of the IS/OS was significantly correlated with the BCVA (P<0.0001, r=-0.375).

Conclusions: The presence of the IS/OS was associated with better visual acuity and thicker fovea in RP patients. The absence of an IS/OS may reflect a foveal dysfunction in RP patients.