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Between eye asymmetry in keratoconus in an Indian population
1Department of Ophthalmology, Postgraduate Institute of Medical Education and Research, Chandigarh 160012, India.
Purpose:
The purpose of this study was to assess the clinical as well as topographic asymmetry between the eyes in keratoconus.
Methods:
Clinical examination including retinoscopy, distant direct ophthalmoscopy, manual keratometry (Bausch & Lomb), slitlamp biomicroscopy and topography (Nidek ARK10000) was carried out on 44 eyes of 22 subjects. At least four high quality topographical images, which were within 0.25 D of one another as measured by simulated keratometry (SimK), were obtained for each eye. Of these, the one with the best alignment and at least six digitised rings was selected for analysis.
Results:
The visual acuity (logMAR), and spherical and cylindrical errors showed marked asymmetry with means of 0.3 +/- 0.3 (SD),-5.2 +/- 6.2 D,-3.1 +/- 2.5 D in the better eyes and 0.5 +/- 0.3,-9.8 +/- 8.5 D,-5.0 +/- 2.5 D in the worse eyes (p = 0.01, 0.05, 0.01, respectively). Scissoring retinoscopy reflex, oil droplet sign, Munson's sign, Vogt's striae, scarring and keratometry readings were significantly greater in the more affected eyes. The inferior-superior steepening, central corneal power and apex power as deduced from topography were significantly greater in the more affected eyes with values of 20.3 +/- 15.7 D, 51.4 +/- 10.1 D, 56.7 +/- 11.0 D in the better eyes and 30.4 +/- 18.6 D, 60.1 +/- 10.9 D, 68.7 +/- 19.6 D in the worse eyes (p = 0.05, 0.01, 0.02).
Conclusion:
Keratoconus is essentially a bilateral but asymmetric corneal degeneration. Seven of our patients had clinically unilateral keratoconus but on topography, based on KISA% index, six of the unaffected eyes were diagnosed as keratoconus though much milder than in the other eye.
