Choroidal Thickness in Choroideremia

Abstract

Purpose: To compare the subfoveal choroidal thickness in patients with Choroideremia (CHM) and in normal age-matched male control patients using Enhanced Depth Imaging Optical Coherence Tomography (EDI OCT)

Methods: EDI OCT was performed in male patients with a clinical and genetic diagnosis of CHM and in age-matched patients without significant retinal or choroidal pathology. An EDI Volume scan covering a 30 x 20-degree area centered at the fovea was used. Each scan has 47 sections, with an average of 50 scans for each section. The choroidal thickness was measured directly below the fovea from the outer border of the retinal pigment epithelium (RPE) to the inner scleral border. CHM patients were divided into three groups based on the subfoveal retinal features: group 1 absence of outer retinal layers, group 2 evidence of abnormal outer retinal layers, group 3 normal outer retinal layers. Statistical analysis was performed to compare the median choroidal thickness between CHM and normal patients (Mann-Whitney U Test), to evaluate the relationship between the retinal and choroidal degeneration in CHM patients (Kruskal-Wallis Test) and to compare the choroid in normal controls versus CHM patients with normal subfoveal retinal features (Mann-Whitney U Test)

Results: 32 patients (63 eyes) were enrolled: 31 eyes of 16 CHM patients (mean age 39.2 years, range 15-62) and 32 eyes of 16 normal patients (mean age 39.7 years, range 17-60). The median choroidal thickness was 151 μm (interquartile range 76-206) in CHM patients and 316 μm (interquartile range 271-335) in control patients; a statistically significant difference between the two groups was found (p < 0.0001). Choroidal thickness was statistically different between the 3 groups classified according to retinal changes (p < 0.001). In patients with CHM and normal subfoveal retinal features the choroid was statistically significant thinner than choroidal thickness in the control patients (p < 0.0001)

Conclusions: The choroidal thickness is significantly decreased in CHM patients with both retinal and choroidal degeneration increasing during the disease process. CHM patients with normal subfoveal retina have a thinner choroid than the control patients, thus suggesting that RPE-choroid degeneration precedes photoreceptor loss, supporting the rationale for targeting the RPE with adeno-associated virus 2 in gene therapy approaches for CHM

Keywords: 696 retinal degenerations: hereditary • 550 imaging/image analysis: clinical