Case Study 201

Fig. 5.9L: Two difference keratoconus indices pages.

202 Step by Step Reading Pentacam Topography

Discussion

This case presents a patient with aberrant normal right corneal topography and very abnormal topography of the left cornea. This patient is a chronic user of contact lenses (CL), but even after she stopped using the CL for more than one month, the topography did not change. If you compare the two topographies, you will notice three important things: very steep symmetric bow tie on the sagittal curvature map, conic thickness map and much displaced thinnest location. The elevation maps seem to be normal. The KPD map is also normal. I presented in this case three comparison maps. The first map compares thickness; the difference in thickness is 42 µ, which is abnormal. The second map compares topometry; the vertical values are abnormal in the left eye. The third map compares keratoconus indices pages, see the abnormal curves and average. The diagnosis is abnormal cornea according to Amsler classification. I think the computer did not consider this case as keratoconus or at least keratoconus possible because of the symmetrical bow tie because—as previously mentioned—Amsler is based on curvature front map. However, this case is not a candidate neither for Lasik nor for PRK because of the abnormal and strange topography and because of the possibility of unpredictable post-Lasik results.

P.S. Because the Amsler classification is based on curvature front map and clinical signs, it is coded as TKC among the irregularity indices in the new version of Pentacam software; as it takes part of the decision and not to be completely

dependable.

Bibliography

1.Agarwal Sunita, et al. Dr Agarwals’ Textbook on Corneal Topography. Section I: introduction to corneal topography. Chapter 1: Fundamentals on corneal topography. Eds. Guillermo L. Simón and others. Jaypee Brothers 2006; 4-8.

2.Alan N Carlson. The Oculus Pentacam: Steering clear of bad decisions. Oculus: The Pentacam: the next wave in comprehensive eye scanner technology. ESCRS Sweden 2007.

3.Azar T Dimitri, et al. LASEK, PRK, and Excimer Laser Stromal Surface Ablation. Marcel Dekker 2003; 25-26.

4.Belin W Michael, Khachikian S Stephen. Elevation based topography: Screening for refractive surgery. Chapter 3: Understanding elevation based topography. Highlights of Ophthalmology International 2008; 40.

5.Benjamin F Boyd, et al. Wavefront analysis, aberrometers and corneal topography: section I: chapter 1: the refractive media of the human eye. Eds. Vidushi Sharma and others. Section II: chapter 3: Fundamentals on corneal topography. Eds. Guillermo L. Simón and others. Section III: chapter 8: corneal topography in irregular astigmatism: diagnostic tool in the evaluation of the quality of vision. Eds. Jorge L. Alió and others. Chapter 9: topographic and pachymetric changes induced by contact lenses. Eds. Jairo E. Hoyos and others. Chapter 10: corneal topography in cataract surgery. Eds. Samuel Boyd and Virgilio Centurion. Highlights of Ophthalmology International 2003;3-7;25;146;160-164;173- 176.

6.David D Bogorad. Getting started with the Pentacam. Oculus: The Pentacam: the next wave in comprehensive eye scanner technology. ESCRS Sweden 2007.

Index

208 Step by Step Reading Pentacam Topography

Index 209