AIM: To assess photoreceptor morphology in patients with retinitis pigmentosa(RP) using frequency domain optical coherence tomography (FD-OCT)and its correlation with visual acuity (VA). METHODS: Thirty eyes of 15 patients with RP were imaged with FD-OCT . Patients were selected based on history, examination, fluorescein angiography, and electroretino-graphy. Concurrently, 40 eyes of 20 normal subjects were imaged with FD-OCT. Total retinal thickness (RT),inner retinal layer (IRL) and outer retinal layer (ORL) were defined and measured on FD-OCT images in all subjects and were compared between the two groups using independent-sample t test. The RT and ORL thickness measurements in RP patients were correlated with visual acuity using Pearson correlation and linear regression. RESULTS:FD-OCT demonstrated macular photoreceptor thinning in all RP patients. The difference in IRL between RP patients and normal subjects was not statistically significant (P=0.058), but the difference in RT and ORL between the two groups was significant (P<0.01). Visual acuity showed a fair correlation with RT and an excellent correlation with ORL . CONCLUSION :In the current study using FD-OCT, a new thickness measurement termed ORL is demonstrated to quantify photoreceptor loss. ORL was statistically thinner in patients with RP than in normal eyes and showed correlation with logMAR visual acuity. ORL appears to be a probable predictor of visual acuity in RP.