Abstract
Purpose: :
To correlate structural and functional changes of the macula in patients with retinitis pigmentosa (RP) in order to assess the integrity of intraretinal layers by OCTRIMA software.
Methods: :
Twenty-nine eyes of 22 patients with RP and seventeen eyes of 17 healthy subjects were retrospectively selected for this study. Optical coherence tomography (OCT) examination was performed on each macula. The raw OCT data were processed using OCTRIMA. The thickness of the retinal nerve fiber layer (RNFL), ganglion cell layer and inner plexiform layer complex (GCL+IPL), inner nuclear layer and outer plexiform layer complex (INL+OPL) and the outer nuclear layer (ONL) were recorded. The patients with RP underwent also multifocal electroretinography (mfERG) examination. The eyes of RP patients were divided into two groups based on retinal functional involvement. The RP-NA (no activity) group consisted of 12 eyes which had no detectable mfERG. The RP-A (activity) groupconsisted of 17 eyes which had diminished but detectable central mfERG. Thickness values of the intraretinal structures and the retina were compared between the RP-NA, RP-A and control groups using ANOVA followed by Newman-Keuls test.
Results: :
In the central region of the macula the thickness of the ONL was significantly decreased in the RP-NA eyes compared to both RP-A eyes and controls (84±13, 107±18 and 112±7 µm, respectively, p<0.05). In the pericentral region, the ONL showed significant thinning in the RP-NA and RP-A groups compared to controls (56±14, 61±13 and 87±5 µm, respectively, p<0.05), while the thickness of the RNFL, GCL+IPL and INL+OPL was significantly decreased only in the RP-NA eyes compared to RP-A eyes and controls (23±7, 27±5 and 25±3 for RNFL, 77±9, 96±15 and 93±8 for GCL+IPL, 66±11, 77±6 µm and 75±6 for INL+OPL, respectively, p<0.05 in all cases). In the peripheral region, the RNFL was significantly thicker in the RP-NA and RP-A groups compared to controls (55±14, 56±10 and 43±2 µm, respectively, p<0.05), while the thickness of the GCL+IPL and ONL was significantly decreased in the RP-NA and RP-A groups compared to controls (50±12, 49±9, 67±4 and 46±13, 45 ±11, 75±3 µm, respectively, p<0.05).
Conclusions: :
Our in vivo results support that degeneration of the outer retina precedes the changes of the inner retina in RP. OCT image segmentation could be a valuable tool for the evaluation of retinal changes in RP which could help the planning of therapeutic interventions such as retinal implants in the future.
Keywords: retinal degenerations: hereditary • image processing • electroretinography: clinical