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Yukari Jo, Yasushi Ikuno, Yoshiaki Yasuno, Kouji Nishida; Choroidal Thickness Volumetric Analysis In Pathological Myopia Using High-penetration Optical Coherence Tomography. Invest. Ophthalmol. Vis. Sci. 2011;52(14):2709.
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© ARVO (1962-2015); The Authors (2016-present)
The previous optical coherence tomographic (OCT) studies have shown that choroidal thickness in myopic eyes is thinner than emmetropic eyes. In this study, we compared the choroidal volume and thickness of the nine macular sectors as defined by the Early Treatment Diabetic Retinopathy Study (ETDRS) between highly myopic eyes and normal eyes using high-penetration OCT (HP-OCT).
A custom-built HP-OCT (Swept source, 50,000 A-scan/s, 1060 nm wavelength) was used to image 12 eyes of 6 subjects with highly myopic eyes (< -6.0D) and 10 emmetropic eyes from normal database under 45 years old. The scan protocol was 6 x 6 mm square raster scan consisting of 512 x 256 A-scans. We manually traced the PRE and chorio-scleral interface (CSI) in every 8 horizontal B-scans (32 scans in total). Custom software was used for volumetric analyses and calculated the total choroidal volume and mean thickness at 9 sectors as ETDRS chart. The eyes with macular disease, glaucoma, and with poor image quality were excluded. We obtained informed consent from all participants and an IRB approval from Osaka University Hospital.
The average age of myopic group was 33.3± 3.9 (Mean± SD) years. Similarly the average refractive error (RE) was -9.6± 2.3 D and the average axial length (AL) was 27.4± 1.3 mm. The myopic group was significantly younger (P<.0001), greater myopic RE (P<.0001), and longer AL (P<.0001). The average choroidal volume of the central 6 mm circle was 6.3± 2.3mm3 in high myopic eyes, it is significantly smaller than emmetropic eyes (8.3± 2.2, P<0.05). The average subfoveal choroidal thickness was 286± 120µm (74.1%, compared to controls), which was thinner with a borderline significance (P=.06). The choroidal thickness of nasal sector within 3mm circle was 268± 120µm (73.9%), 297± 112µm (76.1%) at superior, 294± 113µm (75.3%) at temporal, and 295± 116µm (74.0%) at inferior. Temporal and superior sector were significantly thinner than emmetropic eyes (P=0.05 for both). And nasal and inferior was thinner with borderline significance. (P=0.07, and 0.06, respectively). Then, nasal sector within 6mm circle was 229± 99µm (70.1% to controls), 307± 110µm (78.4%) at superior, 296± 103µm (76.9%) at temporal, and 298± 107µm (76.9%) at inferior. Temporal, nasal, and inferior were significantly thinner (P<0.05), superior was borderline (P=0.07).
The choroidal thickness was significantly thinner in highly myopic eyes in volumetric analysis. Myopic choroid has specific pattern in its thickness.
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