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Effects of rigid-gas permeable contact lenses on spectral domain optic coherence tomography parameters in subjects with keratoconus

Poster Details

First Author: T.Küsbeci TURKEY

Co Author(s):    U. Uzunel   B. Yüce   B. Yüksel        

Abstract Details


To evaluate the effect of irregular astigmatism on retina nerve fiber layer (RNLF) thickness parameters obtained by Cirrus HD spectral-domain optic coherence tomography (OCT) in subjects with keratoconus. We also evaluated the change of these parameters after correcting irregular astigmatism with rigid-gas permeable (RGP) contact lenses.


Izmir Bozyaka Training and Research Hospital, Department of Ophthalmology, Turkey


Twenty three eyes of 15 patients who appealed to Izmir Bozyaka Education and Research Hospital Contact Lens Unit with mild keratoconus (Mean keratometry measurements were ≤ 52 D) were included to our study. Contact lenses were chosen between the two keratometric readings or a steep trial lens was fitted over the irregular cornea. Apical touch was permitted. Rose K2 (David Thomas Contact Lenses Ltd, Northampton, UK) contact lenses were applied for our patients. RNFL parameters (The average, superior, nasal, inferior, temporal and 12 clock-hour sectors mean RNFL thicknesses) and also signal strength were measured with OCT (Cirrus HD OCT; Carl Zeiss Meditec, Dublin, CA, USA), before RGP contact lens wearing. OCT measurements were repeated 30 minutes after RGP contact lens wearing. The results were compared with paired t test by using SPSS 15.0.


Mean age was 29.6±8.7 (15-47) years. Mean keratometry value was 47.9±2.1 (45.31-51.70) Mean BCVA was 0.55±0.42 (2.00-0.18) logMAR before contact lens wearing and 0.12±0.11 (0.40-0.00) logMAR after contact lens wearing(p<0.000). Mean signal strength was 6.78±1.62 before contact lens wearing and 8.78±1.08 after contact lens wearing and this difference was statistically significant(p<0.000). Average RNFL thickness was 88.69±15.66 (36-113) before correction with contact lenses and 93.82±12.23 (71-116) after correction with contact lenses. The difference was statistically significant (p=0.022). RNFL thickness at temporal quadrant was 61.39±9.23 (39-74) before contact lens wearing and 64.34±10.37 (42-80) after contact lens wearing (p=0.018). When examined in 12 clock-hour sectors RNFL thickness changed significantly after contact lens wearing at the 1,7 and 11 clock-hour sectors (respectively p=0.040, p=0.028, p=0.039).


RNFLthickness measurements with OCT are affected by irregular astigmatism such as a lot of factors age, refraction error, axial length, myopic tilted disk. Effects of irregular astigmatism on OCT measurements are significant especially on average RNFL thickness, temporal quadrant and 1, 7 and 11 clock-hour sectors. It is advised to repeat OCT measurements after contact lens wearing on patients with irregular astigmatism. FINANCIAL INTEREST: NONE

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