Choroidal Structure Investigated by Choroidal Vascularity Index in Patients with Inherited Retinal Dystrophies
Kia Bayat1 , Kiana Hassanpour1 , Hamideh Sabbaghi2 , Narsis Daftarian3 , Sahba Fekri1 , Hamid Ahmadieh1 *
- Ophthalmic Research Center, Research Institute for Ophthalmology and Vision Science, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Ophthalmic Epidemiology Research Center, Research Institute for Ophthalmology and Vision Science, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Ocular Tissue Engineering Research Center, Research Institute for Ophthalmology and Vision Science, Shahid Beheshti University of Medical Sciences, Tehran, Iran
Abstract: To compare the choroidal structure between patients with inherited retinal dystrophies (IRDs) and healthy individuals by calculating the choroidal vascularity index (CVI).
Methods: The present study was conducted on 113 IRD patients. Also, 113 sex- and age- matched healthy individuals were enrolled as the control group. The patients’ data were extracted from the Iranian National Registry of IRDs (IRDReg®)
CVI was calculated by the method previously described by Sonoda. In brief, enhanced-depth imaging optical coherence tomography (EDI-OCT) images of each eye were binarized using imageJ ((ImageJ, NIH, Bethesda, ML). The sclerochoroidal junction was determined. The total choroidal area (TCA) was measured as the area between the junction and 1500 microns to the temporal and nasal from the foveal center. The luminal area (LA) was calculated as the black areas after niblack binarization. CVI was calculated as the ratio of LA by TCA. Stromal area (SA) was calculated by subtraction of LA from TCA. The CVI and other parameters were compared between different types of IRD and the control group.
Results: The diagnosis of IRD included retinitis pigmentosa (RP) in 69 patients, cone-rod dystrophy (CRD) in 15 patients, Usher syndrome in 15 patients, Leber congenital amaurosis (LCA) in 9 patients, and Stargardt disease (STGD) in 5 patients. The average age of the patients was 38.55 ± 13.62 years in cases and 36.89 ± 11.87 years in control group. Sixty-one (53.98%) individuals of both groups were male.
The average CVI was 0.65 ± 0.06 in the IRD patients and 0.7 ± 0.06 in the control group. (P-value < 0.001). Accordingly, the average of TCA and LA was 2.32±0.63 mm2 and 1.52±0.44 mm2 in patients with IRDs, respectively. The corresponding values were 2.68±0.6 mm2 and 1.85±0.36 mm2 in control group. TCA, and LA were significantly lower in IRD patients totally compared with the control group (all P-values < 0.001).
However, there was no statistically significant difference in terms of SA between cases and controls (0.8±0.24 mm2 vs 0.83±0.3 mm2, P-value= 0.47).
Conclusion: CVI is significantly lower in patients with IRD compared to healthy individuals.
Choroidal changes in IRDs might be more related to the changes in the lumen of the choroidal vessels rather than the stromal changes.
