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KMID : 1159320160180020149
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Korean Journal of Vision Science
2016 Volume.18 No. 2 p.149 ~ p.156
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Prediction of Axial Length Using Schematic Eyes in Emmetropia
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Kim Hyeong-Su
Cho Hyun-Gug
Moon Byeong-Yeon
Yu Dong-Sik
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Abstract
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Purpose: This study aimed to drive formulas and evaluate their usefulness to predict axial length (AL) on the basis of refractive error and corneal radius using schematic eyes.
Methods: This study comprised 101 emmetropic subjects (174 eyes) with a mean age of 54.62±9.11 years. All subjects were free of any ocular disease and had no history of ocular surgery or trauma. Formulas for calculation of ALs were obtained using Gullstrand’s exact schematic eye, Gullstrand’s simplified schematic eye, Gullstrand-Emsley’s schematic eye, Le Grand’s schematic eye, and Bennett and Rabbetts’schematic eye, respectively. ALs were predicted by each formula with measured refractive error and corneal radius by auto-refractometer. The calculated ALs were compared with measured ALs by IOL-master, and the agreement between ALs were evaluated.
Results: The difference between measured AL and calculated AL was small in the order of Gullstrand’s simplified schematic eye, Gullstrand-Emsley’s schematic eye, Bennett and Rabbetts’ schematic eye, Le Grand’s schematic eye, and Gullstrand’s exact schematic eye. Gullstrand’s simplified schematic eye only was not statistically significant (p=0.390), there was high agreement between two ALs in Gullstrand’s simplified schematic eye.
Conclusions: Axial length can be more accurately predicted by formula for calculation based on refractive error and corneal radius using Gullstrand’s simplified schematic eye in emmetropia. Therefore, the accuracy prediction of axial length using a formula could be applied to design of individual spectacle lenses.
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KEYWORD
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Axial length, Schematic eye, Refractive error, Corneal radius, Ophthalmic lens design
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