EyeWorld Asia-Pacific September 2012 Issue

38 EWAP rEfrActivE September 2012 An image from the Pentacam using the BAD II analysis. One patient, three opinions A 21-year-old female soft contact lens wearer presents in your practice as a candidate for refractive surgery. Her contacts have been out for 2 weeks and the refraction is about –3.25 sphere in both eyes. EyeWorld presented this history along with two topographies to three refractive surgeons and asked for their recommendation on the following question: Is the patient a candidate for refractive surgery? Michael W. Belin, MD, professor of ophthalmology and vision science, University of Arizona, Tucson, Ariz., USA; Louis Probst, MD , chief laser surgeon, senior medical advisor, TLC Laser Eye Centers, Chicago, Ill., USA; and Richard L. Lindstrom, MD , adjunct professor emeritus, ophthalmology department, University of Minnesota, Minneapolis, Minn., USA, and founder and attending surgeon, Minnesota Eye Consultants, Minneapolis, weighed in. Dr. Belin: “This is a young female moderate myope who presents for a refractive surgery evaluation. She has four maps (two for each eye) from the Humphrey Atlas [Carl Zeiss Meditec, Dublin, Calif., USA/Jena, Germany]. I no longer use, and have not used for over 5 years, any Placido-derived topographies, believing that accurate elevation systems have for the most part supplanted the need for Placido analysis. “The four-map composite display (anterior curvature, anterior and posterior elevation, and corneal thickness) is a commonly used display by many. The third display (‘refractive’) is one that I do not recommend using, as it was designed with anterior curvature indices to mimic a Placido system and does so with the same false positives and false negatives associated with Placido-derived anterior curvature. “The BAD display shows a normal anterior elevation, which is why you have a normal reading Placido analysis and a normal posterior elevation. The thinnest points are 516 and 524 OD/OS, and the elevation values at the thinnest point are well within normal levels. “The area of concern is in the pachymetric progression. Both eyes have PTI (Percentage Thickness Increase) tracings that fall below the 95% confidence interval, and the Progression Index (max) OD is 1.53, which is high. The Ambrosio Relational Thickness (ARTmax) (thinnest point/PImax) is 337. These values (PTI graph, PImax, and ARTmax) are borderline values, which is why the overall reading of these maps is roughly 1.8 SD from the norm and flagged as ‘yellow.’ “Based on the current exams, I would not perform LASIK, in part due to the age of the patient combined with the borderline BAD display. The overall correction (SE –3.62/–3.46) is low enough to easily consider surface treatment, but I would still want documented tomographic stability over time before proceeding. If treated, I would also consider conventional treatment (for tissue saving) as both the cylinder and high order aberrations are very low. When the U.S. catches up with the rest of the world, this may be a good example of where prophylactic crosslinking would be applicable.” Dr. Probst: “This is a fantastic demonstration of the conundrum that is created with our advanced screening tools. As a low myope with reasonable pachymetry and normal topographies, this patient appears to be an excellent candidate for LASIK. While the Zeiss Pathfinder II software indicated no abnormalities, the Pentacam BAD II analysis software A refractive surgery case study by faith A. Hayden EyeWorld Staff Writer [Oculus, Lynnwood, Wash., USA] detected a pachymetric progression in both eyes that is 2 SD below normal, and therefore the eyes are flagged as ‘suspicious.’ This means that the patient may need to undergo further testing for ‘better’ maps, cancelled, or relegated to PRK. As physicians we clearly want to do the safest procedure for our patients, however the extended healing with PRK is rarely popular with the patients, referring Atlas topography with Pathfinder II analysis. This shows normal topography with a high likelihood of a “normal” topography and no signs statistically of suspect keratoconus.