Abstract
Purpose :
Retinitis pigmentosa (RP) is characterized by progressive degeneration of photoreceptors, leading to thinning of the 'photoreceptor layer' and attenuation of retinal arterioles, presumed to be due to vascular perfusion differential. Spectral-domain OCT (SD-OCT) provides retinal thickness in various areas of retina. With the advent of this novel technology of OCT angiography (OCTA), it provides a 3D noninvasive vascular perfusion mapping of various retinal layers and choriocapillaris. This study correlates the retinal thickness by SD-OCT with the vascular perfusion indices, as measured by OCTA in this cohort of patients with RP.
Methods :
Patients with RP who had both SD-OCT (Spectralis, Heidelberg) and OCTA (Avanti, Optovue) done (29 eyes of 16 patients) were included in this study. Retinal thickness was measured in all 9 ETDRS subfields - central (CMT), inner ring (parafoveal) and outer ring (perifoveal) in all eyes by SD-OCT. The OCTA reported perfusion indices (vessel density and flow index) in parafoveal and perifoveal areas for each of the 4 en-face layers of the retina - superficial plexus, deep plexus, photoreceptors and choriocapillaris. Correlation statistics were performed between the central macular thickness (CMT) by SD-OCT and visual acuity; perifoveal and parafoveal retinal thickness with perfusion indices in each retinal layer in the same zones.
Results :
The mean parafoveal retinal thickness was 301.36±47.69; and mean perifoveal retinal thickness was 254.92±33.18. OCTA showed that there was marked decrease in perfusion indices in superficial and deep retinal plexus and marked increase in the photoreceptor layer in patients with RP compared to normal (p<0.001) with no significant change in choriocapillaris layer (p>0.05). There was poor correlation of retinal thickness to perfusion indices of superficial and deep plexus but better correlation was noted with perfusion indices of that of photoreceptor layer and choriocapillaris (r≥0.5).
Conclusions :
The parafoveal and perifoveal retinal thickness did not correlate well with the superficial and deep plexus vascular perfusion indices but with the photoreceptor and choriocapillaris indices. This new technology of OCTA gives an insight into the pathogenesis of RP and may be of prognostic value as a marker for the severity of the disease in the future.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.