Su-Ho Lim1,2, Seongyong Jeong2,3, Jang Hwan Ahn2,3, Jano van Hemert4, Min Sagong5,6. 1. Department of Ophthalmology, Daegu Veterans Health Service Medical Center, Daegu, Korea. 2. Department of Ophthalmology, Yeungnam University College of Medicine, 170 Hyunchung-ro, Nam-gu, 42815, Daegu, Korea. 3. Yeungnam Eye Center, Yeungnam University Hospital, Daegu, Korea. 4. Optos plc, Dunfermline, United Kingdom. 5. Department of Ophthalmology, Yeungnam University College of Medicine, 170 Hyunchung-ro, Nam-gu, 42815, Daegu, Korea. msagong@ynu.ac.kr. 6. Yeungnam Eye Center, Yeungnam University Hospital, Daegu, Korea. msagong@ynu.ac.kr.
Abstract
BACKGROUND: Ultra-widefiled (UWF) retinal images include significant distortion when they are projected onto a two-dimensional surface for viewing. Therefore, many clinical studies that require quantitative analysis of fundus images have used stereographic projection algorithm, three-dimensional fundus image was mapped to a two-dimensional stereographic plane by projecting all relevant pixels onto a plane through the equator of the eye. However, even with this impressive algorithm, refractive error itself might affect the size and quality of images theoretically. The purpose of this study is to investigate the effects of refractive power on retinal area measurements (quantification) using UWF retinal imaging (Optos California; Dunfermline, Scotland, UK). METHODS: A prospective, interventional study comprised 50 healthy eyes. UWF images were acquired first without the use of a soft contact lens (CL) and then repeated with six CLs (+ 9D, +6D, +3D, -3D, -6D, and - 9D). Using stereographically projected UWF images, the optic disc was outlined by 15-17 points and quantified in metric units. We divided the subjects into three groups according to axial length: Groups A (22-24 mm), B (24-26 mm), and C (≥ 26 mm). The primary outcome was percentage change before and after use of the CLs. Secondary outcome was proportion of subjects with magnification effects, maximal changes > 10 %. RESULTS: The study population was 6, 28, and 16 eyes in each group. Overall changes for the measured area were not significantly different in the whole study population. Group C had a larger proportion of magnification effects compared to Groups A and B (50.0 %, 0 %, and 3.6 %, P = 0.020). Measured area with plus lenses was significantly higher in Group C (P < 0.001). CONCLUSIONS: The use of CLs might affect quantification of eyes with long axial length when using UWF images. Ophthalmologists should consider refractive error when measuring area in long eyes.
BACKGROUND: Ultra-widefiled (UWF) retinal images include significant distortion when they are projected onto a two-dimensional surface for viewing. Therefore, many clinical studies that require quantitative analysis of fundus images have used stereographic projection algorithm, three-dimensional fundus image was mapped to a two-dimensional stereographic plane by projecting all relevant pixels onto a plane through the equator of the eye. However, even with this impressive algorithm, refractive error itself might affect the size and quality of images theoretically. The purpose of this study is to investigate the effects of refractive power on retinal area measurements (quantification) using UWF retinal imaging (Optos California; Dunfermline, Scotland, UK). METHODS: A prospective, interventional study comprised 50 healthy eyes. UWF images were acquired first without the use of a soft contact lens (CL) and then repeated with six CLs (+ 9D, +6D, +3D, -3D, -6D, and - 9D). Using stereographically projected UWF images, the optic disc was outlined by 15-17 points and quantified in metric units. We divided the subjects into three groups according to axial length: Groups A (22-24 mm), B (24-26 mm), and C (≥ 26 mm). The primary outcome was percentage change before and after use of the CLs. Secondary outcome was proportion of subjects with magnification effects, maximal changes > 10 %. RESULTS: The study population was 6, 28, and 16 eyes in each group. Overall changes for the measured area were not significantly different in the whole study population. Group C had a larger proportion of magnification effects compared to Groups A and B (50.0 %, 0 %, and 3.6 %, P = 0.020). Measured area with plus lenses was significantly higher in Group C (P < 0.001). CONCLUSIONS: The use of CLs might affect quantification of eyes with long axial length when using UWF images. Ophthalmologists should consider refractive error when measuring area in long eyes.
Entities:
Keywords:
Area measurement; Axial length; Quantification; Retina; Ultra‐widefield imaging
Authors: Min Sagong; Jano van Hemert; Lisa C Olmos de Koo; Cullen Barnett; SriniVas R Sadda Journal: Ophthalmology Date: 2015-01-08 Impact factor: 12.079
Authors: Colin S Tan; Milton C Chew; Jano van Hemert; Michael A Singer; Darren Bell; SriniVas R Sadda Journal: Br J Ophthalmol Date: 2015-07-01 Impact factor: 4.638
Authors: Kang Wang; Khalil Ghasemi Falavarjani; Muneeswar G Nittala; Min Sagong; Charles C Wykoff; Jano van Hemert; Michael Ip; SriniVas R Sadda Journal: Invest Ophthalmol Vis Sci Date: 2018-07-02 Impact factor: 4.799