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Lauren N. Ayton, Chi D. Luu, Robyn H. Guymer; Choroidal Thickness in Retinitis Pigmentosa. Invest. Ophthalmol. Vis. Sci. 2011;52(14):4926.
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To facilitate the development of a retinal prosthesis to be placed in the supra-choroidal space, knowledge of the thickness of the choroid in eyes with retinitis pigmentosa (RP) is essential to develop safe implantation techniques and for device design. There is a lack of reliable data on the choroidal thickness profiles of healthy and diseased eyes in the current literature. The aim of this study was to investigate the choroidal thickness in normal eyes and eyes with RP.
Choroidal thickness was measured in 34 eyes of 19 patients with RP. Diagnosis of RP was confirmed with clinical ocular fundus examination, fundus photography and electroretinography. The choroidal thickness measurements were made using an inverted scan with Heidelberg Spectralis Optical Coherence Tomography (OCT). The choroidal thickness was measured at the fovea and at ±8 degrees eccentricity in the nasal and temporal retina. Similar data was collected on 14 eyes of age-matched control subjects, who did not have any ocular disease or pathological refractive error.
Visual acuity in the RP eyes ranged from light perception to 6/7.5, and the mean duration of disease was 27.2 years (range 6 - 52 years). The mean choroidal thickness at the fovea (330.6 ± 83.6µm) was greater than that of the temporal (300.6 ± 73.2µm) and nasal (240.7 ± 58.4µm) retina in normal eyes. In RP patients, the mean thickness was also greater at the fovea (242.2 ± 89.6µm) than the temporal (213 ± 71.23µm) and nasal (160.8 ± 59.72µm) retina, but all values were significantly lower than in the age-matched controls (p<0.001). The choroidal thickness at the fovea was significantly correlated with visual acuity (r=-0.45, p=0.007), such that subjects with poorer acuity also showed a thinner choroidal layer. The sub-foveal choroidal thickness also was significantly lower in patients with longer duration of disease (r=0.5, p=0.003).
We have shown that patients with RP have a thinner choroidal layer than age matched controls. Decreased choroidal thickness was also correlated to visual acuity and disease duration, with patients with poorer acuity and/or longer disease duration having thinner choroidal layers. This information will be valuable for the development of retinal prosthetic implants and the surgical procedure required for placement of a supra-choroidal implant.
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