Purpose To evaluate alteration of the optic radiation (OR) in patients with retinitis pigmentosa (RP) using fractional anisotropy (FA) measured by diffusion tensor MRI.

Methods We performed MRI and evaluated alteration of the ORs in 17 patients with RP and 27 healthy controls. Regions of interest were placed over the bilateral anterior and posterior areas of the ORs, and we measured the FA value of each region. Visual field (VF) tests were examined in all subjects, and we corrected the residual VF area according to the projection area to the striate cortex. Differences between the FA values of patients and healthy controls were tested. We performed regression analyses between the sum of the corrected VF areas and FA values in the anterior or posterior contralateral ORs in patients with RP. Moreover, we performed regression analyses between the average of FA values of ORs and the average of both eyes of visual acuity in patients with RP.

Results FA values of the bilateral anterior and posterior ORs were lower in patients with RP (anterior right, p=0.012; posterior right, p=0.0004; anterior left, p=0.0008; and posterior left, p=0.0004) compared with those of healthy controls. In patients with RP, significant correlations were observed between average FA values of anterior ORs and average visual acuity (correlation coefficient (r)=−0.54; p=0.025).

Conclusions In patients with RP, alterations may occur not only in the retina but also in the brain.