Background: The aim of this study is to analyze and compare the progression of photoreceptor atrophy among siblings affected by retinitis pigmentosa by means of spectral SD-OCT.
Methods: Fifty three eyes of 27 patients belonging to 12 family clusters were analyzed. To assess the annual progression rate of photoreceptor atrophy, the ellipsoid zone (EZ) line was measured in OCT sections through the fovea. We used multivariate generalized mixed effects to model the rate of progression and its relation to the initial ellipsoid zone line width.
Results: During our 4.84 years (± 1.44) mean follow up time (range 3-7) 53 eyes were examined. The ellipsoid zone line width declined with a yearly average rate of 76.4 μm (4.16% / year) (p-value < 0.0001). Progression rates were poorly correlated within family clusters (p-value = 0.23) and showed statistical difference between affected siblings (p-value = 0.007). There was no correlation between inter-familiar progression rate and mode of inheritance (p-value = 0.98) as well as between age and ellipsoid zone line width among siblings (p-value = 0.91).
Conclusion: RP could be extremely heterogeneous even among siblings: an accurate and sensitive method to follow the progression of the disease is fundamental for future development of clinical trials and therapy strategies.
Keywords: Disease progression; Ellipsoid zone; Retinitis pigmentosa; SD-OCT; Siblings.