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L. A. Macfadden, L. S. Gray, N. C. Strang, D. Seidel; The Effect of Eye Rotation on Measurements of Peripheral Retinal Shape Using the IOLMaster. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4002.
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© ARVO (1962-2015); The Authors (2016-present)
The measurement of retinal shape using the IOLMaster has relied on the subjects rotating their eye to measure peripherally. However there is no data on whether eye rotation affects peripheral ocular shape. The aim of this experiment is to determine whether eye rotation affects the measurement of peripheral retinal shape in myopic and hyperopic subjects using the IOLMaster.
24 subjects participated with informed consent in the experiment (10 myopes (MYO), 10 hyperopes (HYP) and 4 emmetropes (EMM)). All subjects were visually normal with VA of 0.0 logMAR or better. The mean age of the subjects was 21.4±2.2years, and all were students in the University. Cycloplegia and mydriasis were induced using 1.0% Cyclopentolate and the measurements were taken 30 mins after instillation of the eyedrops. Peripheral retinal curvature was measured with the IOLMaster (Zeiss) which measures axial length using partial coherence interferometry. 5 measures of axial length were taken at 10 degree intervals from 0-40 degrees nasally and temporally using 2 experimental paradigms. Experiment 1. Subjects rotated their eye to view an LED target array, attached to the front of the instrument. Experiment 2. Subjects maintained fixation on a stationary target in the primary position while the IOL master was rotated about the centre of rotation of the eye. The data was fitted using 2nd order polynomials with a different curve being fitted to the temporal and nasal shape to take into account retinal asymmetry.
Results were analysed in terms of the 1st and 2nd order coefficients from the best fit polynomials. Significant asymmetry between the temporal and nasal retinal shapes was found in the MYO group (p<0.01) with the nasal retina having a flatter profile. This asymmetry was found in both experimental paradigms. There was no measurable retinal asymmetry in either the HYP or EMM group. Eye rotation produced a significant shift in the less prolate direction in both temporal (p<0.01) and nasal (p<0.01) retinal profiles in the MYO group. No significant effect of eye rotation was identified in either the EMM group or the HYP group.
1. Asymmetry between the temporal and nasal retinal profiles is more pronounced in the myopic eye. 2. Ocular rotation has a substantial effect on the retinal profile measured by the IOLMaster in myopic eyes. 3. These factors need to be taken into account when measuring retinal shape using eye rotation.
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