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Influence of contact lens wear on topography indices in keratoconus and in estimating progression prior to collagen cross-linking

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Session Details

Session Title: Cross-Linking II

Session Date/Time: Tuesday 16/09/2014 | 16:30-18:00

Paper Time: 16:52

Venue: Boulevard A

First Author: : P.Vaddavalli INDIA

Co Author(s): :    P. Kumar              

Abstract Details


To evaluate the influence of gas permeable contact lens wear on the topography indices of keratoconus corneas and to estimate the duration of discontination of lens wear required to accurately assess progression before collagen crosslinking.


LV Prasad Eye Institute, Hyderabad, India


In this prospective study, 29 eyes of 20 patients with a clinical diagnosis of keratoconus underwent corneal topography using the Orbscan Iiz system. All participants were RGP contact lens wearers with the minimum experience of a year and the average wearing time of at least eight hours per day. Baseline corneal topography was performed within 5 minutes of removal of contact lenses. Topographic indices such as Simulated Keratometry (SimK) Astigmatism, Maximum and Minimum Keratometry (Max and Min K) values, mean power at central 3mm and 5mm zones were noted. Patients were then advised to discontinue their habitual lenses and advised to switch to spectacle wear in one eye. Patients were reviewed at one weekly intervals for 6 weeks and underwent topography by the same examiner each visit.


Corneal topographic maps of 29 eyes from 18 keratoconus patients were analysed. 10 were male (55.5%) and 8 were female (44.4%) and mean age of the patients was 20.26 ± 4.42 years. 23 of the 29 eyes (79.31%) were fitted with three-point touch technique (group 1) and 6 out of 29 eyes (20.68%) were fitted with apical clearance technique (group 2). 18 out of 29 eyes had moderate Keratoconus (Mean K value 45D - 52D) and 11 out of 29 eyes had severe Keratoconus (Mean K value > 52D). Maximum and minimum Keratometry values, Mean power of the central 3 mm and 5 mm zones and thinnest pachymetry values were noted at each visit. One-way repeated measure ANOVA was used to analyse the mean difference between the different indices of the consecutive topographic maps. Statistically significant differences were seen in the mean difference between the first and the second consecutive scans for indices such as Max K values (-2.13D; p <0.005), Min K values (- 1.0086D; p<0.005), Sim K’s astigmatism (-1.127D; p <0.005) and Mean power in central 3 mm zone (-0.83D; p= <0.005).They did not show any significant change in the subsequent follow up visits.


All topography indices returned to baseline within one week of discontinuation of GP lenses. Hence, a period of one week of discontinuation of RGP lenses seems adequate to reliably compare topography maps and estimate progression in keratoconus prior to advising collagen crosslinking.

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