Posters

Relationship between corneal astigmatism and corneal topography

Poster Details

First Author: D.Rani INDIA

Co Author(s):    S. Khokhar   C. Dhul   Y. Gupta   A. Gupta           

Abstract Details

Purpose:

: To evaluate relationship between corneal astigmatism and corneal topography in healthy individuals

Setting:

Dr. Rajendra Prasad Centre for Ophthalmic Sciences, All India Institute of Medical Sciences, New Delhi

Methods:

A prospective case series of 32 eyes of 16 patients between age 7 years to 23 years with astigmatism in the range of 3 to 7 D(Diopters) and mean follow up of 3 years.  All patients underwent a cycloplegic refraction, a detailed anterior and posterior segment evaluation, corneal thickness measurement and corneal topographic analysis with Pentacam(Oculus Pentacam HR®) with Belin/Ambrosio enhanced ectasia display (BAD). The correlation of corneal topography and thickness with amount of astigmatism was serially observed. Bonferroni correction was applied for correlation and statistically significant p value was decided as 0.0045 (0.05 divided by 11 observations).

Results:

Mean spherical equivalent was -4.05±4.7 D(mean astigmatism -3.93D).Mean and maximum keratometry was 44.3±1.4 D and 47.3±2.09 D respectively. Corneal topography showed symmetrical bow tie (37.5%), asymmetrical bow tie with superior (34.3%) or inferior (25%)steepening and oval pattern (3.1 %). Mean pachymetry at centre, apex and thinnest pachymetry were 532.9±48.0 micrometer (μm), 533.8±48.9μm and 521.8±55.9μm. D-value (BAD) was 2.07±1.0 (0.49 to 4.54). At last follow up, 71.8% had normal cornea, 12.5% had forme-fruste keratoconus and 15.6 % had keratoconus. There was no significant correlation between keratometry, astigmatism, corneal topography and enhanced ectasia display.

Conclusions:

More than two-third of patients with cylinder >3 D had a normal corneal topography which remained normal over time. There is a risk of developing forme-fruste keratoconus or keratoconus and hence all patients with high astigmatism should undergo detailed corneal topographic and pachymetric evaluation and regular monitoring. However there is no significant correlation between corneal pachymetry, topography and astigmatism. Hence abnormality of one cannot be extrapolated to others. The amount of astigmatism is not directly related to risk of keratoconus.

Financial Disclosure:

None