Effect of ocular magnification on macular measurements made using spectral domain optical coherence tomography

• Published in: Indian journal of ophthalmology Vol. 63; no. 5; pp. 427 - 431
• Main Authors: Parthasarathy, Mohana, Bhende, Muna
• Format: Journal Article
• Language: English
• Published: India Medknow Publications 01.05.2015; Medknow Publications and Media Pvt. Ltd; Medknow Publications & Media Pvt. Ltd; Medknow Publications & Media Pvt Ltd; Wolters Kluwer Medknow Publications
• Subjects: Adaptive optics; Adult; Age-related macular degeneration; axial length; Central reading center; Choroid; Choroidal imaging; Choroidal neovascularization; choroidal thickness; Community; cone density; Cystoid macular edema; dexamethasone implant; digital imaging; en-face optical coherence tomography; enhanced depth imaging technique; external limiting membrane; Female; Follow-Up Studies; Fovea Centralis - cytology; foveal diameter; foveal slope; Fundus autofluorescence; Humans; idiopathic juxtafoveal telangiectasis; juxtafoveal retinal telangiectasia; Karnataka Internet-assisted Diagnosis of Retinopathy of Prematurity; lipofuscin; lutein; Macula Lutea - cytology; macular edema; macular pigment; macular telangiectasia; Male; Microscope-integrated optical coherence tomography; myopia; Müller cells; ocular magnification; optical coherence tomography; Original; Ozurdex; parafoveal telangiectasis; perifoveal telangiectasis; polypoidal choroidal vasculopathy; randomized controlled trial; Reference Values; Refraction, Ocular - physiology; Refractive Errors - diagnostic imaging; RESCAN; retina; retinal angiomatous proliferation; retinal dystrophies; retinal imaging; retinal telangiectasis; retinopathy of prematurity; Retrospective Studies; serous retinal detachment; spectral domain optical coherence tomography; standard operating procedure; subretinal neovascularization; swept source optical coherence tomography; telemedicine; Tomography, Optical Coherence - methods; universal screening; uveitis; vitreoretinal surgery; zeaxanthin; ocular magnification; optical coherence tomography; foveal diameter; Artifact; foveal slope
• ISSN: 0301-4738; 1998-3689; 1998-3689
• DOI: 10.4103/0301-4738.159877

Aim: The aim of the present study was to study the effect of ocular magnification on macular measurements made using spectral domain optical coherence tomography (OCT). Materials and Methods: One hundred and fifty-one subjects were included from the normative study of foveal morphology carried out at our hospital. Subjects underwent comprehensive eye examination and macular scanning using Cirrus high-definition OCT and axial length (AXL) measurement. Macular cube 512 × 128 scan protocol was used for scanning the macula. Automated measurements of the fovea namely foveal diameter, foveal slope (lateral measurements) and foveal depth (axial measurement) were taken. A correction factor for ocular magnification was done using the formula t = p × q × s, where "t0" is the corrected measurement, "p" is the magnification of OCT, "q0" is the ocular magnification, and "s" is the measurement on OCT without correction. The difference between corrected and uncorrected measurements was evaluated for statistical significance. Results: Mean AXL was 22.95 ± 0.78 mm. Refractive error ranged from −3D to +4D. Mean difference between measured and corrected foveal diameter, slope and depth was 166.05 ± 95.37 ΅m (P < 0.001), 0.81° ± 0.53° (P < 0.001) and 0.05 ± 0.49 ΅m (P = 0.178) respectively. AXL lesser than the OCT calibrated value of 24.46 mm showed an increased foveal diameter (r = 0.961, P < 0.001) and a reduced foveal slope (r = −0.863, P < 0.001) than the corrected value. Conclusion: Lateral measurements made on OCT varied with AXL s other than the OCT calibrated value of 24.46 mm. Therefore, to estimate the actual dimensions of a retinal lesion using OCT, especially lateral dimensions, we recommend correction for the ocular magnification factor.