Classification of Anterior and Posterior Elevation and Axial Curvature Maps of Cornea using the Orbscan in Myopic Eyes

Bae, Cheol Yong; Kim, Sang Duck; Kim, Jae Duck

Abstract

PURPOSE: To evaluate anterior and posterior elevation maps and axial curvature maps in myopic eyes.
METHODS
One hundred and four eyes of 52 myopic patients were investigated using the Orbscan (Orbtek, Inc., USA). The anterior and posterior maps were defined as PAR CTS. And the axial curvature maps were designated as Bogan's classification. We got the distribution and astigmatism power of every map patterns, and the similarity of both eyes under map patterns.
RESULTS
Island (37.5%) was the most common anterior elevation pattern, and regular ridge (36.5%) pattern was the most common in posterior corneal surface. There was more significant astigmatism in regular ridge and irregular ridge patterns than incomplete ridge in anterior corneal surface. And astigmatism was more significant on regular ridge than incomplete ridge in posterior corneal surfaces. There was no significant difference between topography of anterior and posterior corneal surface. In axial curvature maps, symmetric bow tie was 35.6% of 104 eyes, and irregular, oval, asymmetric bow tie, round were observed in 27.9%, 18.3%, 13.5%, 4.8%, respectively. Mean astigmatism was significantly high on symmetric bow tie than round. Similarity of both eyes was 50% in anterior elevation maps, 26.3% in posterior corneal surface, and 59.6% in axial curvature maps.
CONCLUSIONS
Anterior and posterior elevation and axial power corneal topography maps using the Orbscan were useful for evaluation of normal cornea and preoperative and postoperative corneal status at refractive surgery. But, there were many irregular types and low similarity of both eyes relatively.