Purpose
Background: Retinitis pigmentosa (RP) encompasses a group of hereditary retinal diseases that result in the progressive loss of rod and finally cone photoreceptors, resulting in blindness. RP can have an autosomal dominant, autosomal recessive or X-linked inheritance pattern. Sporadic cases have also been reported. The clinical consequences are varied. Histological studies of the disease are well known. However, retinal structural modifications in vivo are crucial. The recent development of an automated segmentation process of retinal layers on SD-OCT images could allow a precise evaluation and personal follow up. Purpose: To investigate the automated retinal segmentation features with SD-OCT and to evaluate the relationship between retinal layer impairment and visual function in patients with RP.
Methods
Patients and Method: A prospective, case-control study of 60 eyes of 30 patients with RP imaged using the Spectralis HRA and OCT (Heidelberg Engineering, Heidelberg, Germany), with the automated layer segmentation software implemented in the instrument. Inclusion criteria: 30 consecutive RP patients with clear media to allow adequate OCT examination were included. The retinal layers thickness was measured by automated segmentation of the OCT image beneath the fovea, at 500 µm and 1500 µm intervals, nasally and temporally to the center of the fovea. These measurements were compared to those of 30 healthy, refractive and age-matched controls, with no clinical evidence of retinal or glaucomatous disease. Visual acuity was measured using the ETDRS scale.
Results
Primary endpoint: Visual impairment was highly related with central photoreceptor thickness (p<0.0001). Secondary endpoint: Visual impairment was related with - photoreceptor thickness at 500µm nasal and temporal from the center; - inner plexiform layer and ganglion cell layer complex thickness at each measurement; - inner nuclear layer and outer nuclear layer were not related to visual impairment. Photoreceptor thickness was related to outer nuclear layer thickness.
Conclusions
Our study has shown a relationship between visual impairment and specifics retinal layer thickness. The relationship between photoreceptor and outer nuclear layers thickness could help to improve the knowledge of the general progression of the disease. This new device could possibly help to identify precise phenotypes and be an insight into genotypes.