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Evaluation of corneal tomography in primary pterygium
Session Title: Cornea Medical
Session Date/Time: Monday 07/10/2013 | 08:00-10:00
Paper Time: 09:48
Venue: Elicium 1 (First Floor)
First Author: : S.Goel INDIA
Co Author(s): : M. Vanathi T. Agarwal S. Khokhar T. Dada
To study the effect of pterygium on corneal tomography and corneal wavefront aberrations at the anterior and posterior corneal surface using scheimpflug imaging with pentacam and to correlate it with the dimensional parameters of pterygium.
Clinical data regarding symptoms, duration of pterygium, visual acuity was recorded for 55 patients (age=43.4 years, SD=11.5 and 2:1 male: female ratio) with unilateral primary pterygium. All pterygia were examined with Pentacam and imaged using zeiss slit lamp mounted camera and dimensions (length, height, corneal area encroached) measured using image J software. Spearman correlation analysis was performed to evaluate the effect of pterygium on corneal tomography and wavefront aberrations.
The mean length, height and area of pterygium encroaching onto the cornea was 2.23(+/-1.15) mm, 4.85(+/-1.37) mm and 8.07(+/-5.9 mm2). Corneal astigmatism (flattening of horizontal axis) significantly correlated with dimensions of pterygium (rho=0.469 for height, rho=0.465 for area and rho=0.357 for length of pterygium, p<0.0005). Strongest correlation was seen between fraction of corneal area encroached by pterygium with induced astigmatism, rho= 0.738, p<0.0005. At the posterior corneal surface against the rule astigmatism was noted as against with the rule at the anterior corneal surface. Significantly higher corneal wavefront aberrations were noted in eyes with pterygia (both lower and higher order at anterior surface and only higher order at posterior surface) with spearmans correlation coefficient being highest with corneal area encroached by pterygium (rho=0.540 for LOA and 0.553 for HOA) and distance from pupillary centre (rho=0.531 for LOA and 0.564 for HOA).
There was a significant increase in corneal volume, which also did correlate significantly with dimensions of pterygium (H>A>L). Central corneal elevation, corneal thickness, pupillary diameter, AC depth, mean corneal curvature, Q-value and were comparable in eyes with pterygium and normal control eyes.
Pterygium leads to deterioration of visual performance not only by causing refractive and topographic changes but also by causing a significant increase in corneal wavefront aberrations (both lower order and higher order), which may explain why the patients have significant visual symptoms despite visual axis sparing and appreciated visual correction.