Nina Tahhan


PURPOSE. To evaluate the effects of very short-term reverse geometry orthokeratology lens wear on corneal topography. METHOD. 10 subjects aged between 20 and 51 years, with refractive error range from plano to -4.00 D (cyl < -1.00) had topography measurements taken using Eyesys version 4.2 before and after 15 minutes of reverse geometry orthokeratology trial lens wear.The non-lens wearing eye was used as control. Difference maps were generated and the area where most change occurred in the treatment zone region was recorded in dioptres. Overall corneal eccentricity (e) was also compared before and after lens wear.

RESULTS. There were significant changes in e values after fifteen minutes of lens wear (p<0.001, paired t-tests) in test eyes when compared to changes in the control eyes. The mean change in e in the test eyes was -0.17 +/- 0.08 D. The difference recorded within the treatment zone, in the area where maximum flattening occurred in test eyes had a mean value of -1.72 D +/- 0.55 (range -1.22 D to -3.12 D). Two lens-wearing eyes showed areas of both steepening and flattening within the treatment zone on the difference map. Difference maps for the control eyes revealed no significant changes.

CONCLUSIONS. Our findings show that a significant amount of corneal topographical change can occur within a short period of reverse geometry lens wear. The results indicate that caution may need to be exercised when interpreting subsequent lens fits if made too soon after an initial trial. It has been reported that corneal epithelial changes are mostly responsible for the refractive effects produced by reverse geometry lenses. The present study indicates that such changes can occur in a matter of minutes.


Year: 2001

Program Number: Poster 43

Author Affiliation: CRC for Eye Research and Technology, UNSW

Co-Authors: Ramkumar Sridharan, Renee du Toit, Eric Papas

Co-Author Affiliation: CRC for Eye Research & Technology, Uni of NSW, CRC for Eye Research & Technology, Uni of NSW, Cornea & Contact Lens Research Unit, Uni of NSW

Room: Exhibit Hall C