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The topography of the peripheral cornea

Read, Scott A., Collins, Michael J., Carney, Leo G., & Franklin, Ross (2005) The topography of the peripheral cornea. In American Academy of Optometry Meeting, 2005, San Deigo, California.

Abstract

Purpose

Few studies have investigated the peripheral cornea outside of the central 6mm. We examined the topography of the peripheral cornea in a large group of young adult subjects and report normative data for this population.

Methods

Corneal topography data were acquired for 100 young adult subjects using a method that allows the combination of central and peripheral maps to produce one large, extended corneal topography map. This computer-based method involves matching the common topographical features in the overlapping maps.

Results

The average apical radius Ro was found to be 7.78 ± 0.2 mm and the asphericity value (Q) was -0.18 ± 0.09 for the central 6mm corneal diameter. Both Ro and Q were found to change significantly with increasing corneal diameter (p <0.001). For a 10 mm corneal diameter, Ro was found to be on average 7.72 ± 0.2 mm and Q -0.36 ± 0.09. The corneal height data was also averaged along the steepest and flattest corneal meridian for each subject. The average Ro was found to be 7.68 ± 0.26 mm and Q -0.32 ± 0.1 along the steepest meridian and Ro 7.81 ± 0.24 mm and Q -0.30 ± 0.1 along the flattest meridian for a 9mm corneal diameter. The average Ro and Q values were found to differ significantly as a function of corneal meridian (both p <0.01) indicating that the steepest corneal meridian flattens in the periphery at a slightly more rapid rate. The RMS fit errors for the conic section (Q) increase markedly for larger corneal diameters. A better fit to the data was attained for the bigger corneal diameters by using higher order polynomial fits (9th order). The average corneal power vectors “M” “J0” and “J45” were all found to reduce significantly in magnitude with increasing corneal diameter (p <0.01), indicating a significant flattening and reduction in toricity for the peripheral cornea.

Conclusions

The peripheral cornea is poorly estimated with a simple conic section. The cornea flattens and becomes slightly less astigmatic in the periphery.

Impact and interest:

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ID Code: 12128
Item Type: Conference Paper
Additional Information: abstract published in Optometry and Vision Science, 82, 055023.
Additional URLs:
Subjects: Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300)
Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300) > Vision Science (111303)
Australian and New Zealand Standard Research Classification > MEDICAL AND HEALTH SCIENCES (110000) > OPTOMETRY AND OPHTHALMOLOGY (111300) > Optical Technology (111302)
Divisions: Current > Research Centres > Centre for Health Research
Current > QUT Faculties and Divisions > Faculty of Health
Current > Institutes > Institute of Health and Biomedical Innovation
Copyright Owner: Copyright 2005 Lippincott Williams & Wilkins
Deposited On: 23 Jan 2008
Last Modified: 10 Nov 2014 15:09

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