A 23-year-old man is referred to you for refractive surgery by his father, a local ophthalmologist. The patient has low myopia, 0.75 D of against-the-rule astigmatism, and normal pachymetry readings. The father wants to explore whether his son is a candidate for LASIK and provides images from his own workup (Figure 1). You obtain additional imaging and measurements (Figures 2-3).
Would you offer this patient LASIK, PRK, or no treatment?
—Case prepared by Colman R. Kraff, MD.
MITCH BROWN, OD
My response assumes that the clinical examination is normal and that the patient's BSCVA is 20/20 or better and symmetric bilaterally. Imaging with the Pentacam Comprehensive Eye Scanner (Oculus Optikgeräte GmbH) shows a normal, slightly astigmatic, against-the-rule (ATR) shape. The sagittal and tangential curvature maps show no areas of asymmetric steepening. The elevation maps are consistent with mild ATR toricity and have no isolated areas of central or paracentral elevation. The images are bilaterally symmetric.
Testing with the Atlas 9000 Corneal Topography System (Carl Zeiss Meditec, Inc.) shows normal curvature and elevation maps that are consistent with ATR astigmatism when compared to a best-fit spherical reference.
I do not use the Visante OCT (Carl Zeiss Meditec, Inc.) to assess corneal shape and am unfamiliar with the information it provides. With that disclosure, however, I would propose that the images provided appear to be consistent with the Atlas and the Pentacam in that they seem to reflect a normal ATR toric corneal shape. The anterior axial curvature maps show slight relative steepening nasally compared to temporally in both eyes. Reiterating my unfamiliarity with the Visante, I do not think that would change my recommendation. Otherwise, nothing stands out as significantly abnormal or asymmetric.
It is important to note that the Atlas and Visante OCT images display quarter-diopter scales, which may accentuate small differences in curvature and perhaps make them appear more significant than they may actually be.
A recent internal analysis of Optical Express' database (unpublished data, July 2012) involved 1,429 low myopes with ATR astigmatism. They were all 25 years of age or younger and underwent treatment between January 2008 and January 2012. The patients did well and did not appear to be at increased risk of ectasia.
Given the available data, I would be comfortable recommending LASIK to this patient.
YOSHIHIRO KITAZAWA, MD, PhD
I would not offer any kind of laser refractive surgery to this patient for two reasons. First, because this patient is a young man and has low myopia, he is at risk of decreasing UCVA with increasing myopia as he ages, even if the surgery is performed successfully and without complication. Second, he has ATR astigmatism, which is uncommon in young people and raises the possibility of keratoconus or pellucid marginal degeneration (PMD).
Low ATR astigmatism is evident in both the axial and sagittal curvature of topography. Slight central flattening does not demonstrate a horizontal bowtie such as a butterfly pattern. The central corneal thickness is quite normal, but the thinnest point has shifted slightly to the lower temporal position; peripheral corneal thinning, however, which is typical in PMD, is not evident. Imaging with the Pentacam does not reveal abnormal posterior elevation.
In conclusion, I would not recommend laser refractive surgery, because this patient is at risk of a keratectatic complication, although the diagnosis of keratoconus or PMD is uncertain at present. If the patient strongly desires improved UCVA, I would offer him the option of the Visian TICL (STAAR Surgical Company; not available in the United States).
COLMAN R. KRAFF, MD
When a young patient presents with low myopia and a low amount of ATR astigmatism, I carefully study the axial topographic maps. In this case, the axial topographies suggest a shape that could be consistent with early PMD. Although the posterior elevations on the Pentacam scans are normal and the Visante posterior elevation is within normal limits, the axial topography is definitely abnormal.
This type of abnormal corneal topography would place this patient in a higher-risk category of developing corneal ectasia after LASIK. When his young age is added to the equation, he has two risk factors. I therefore feel that LASIK is contraindicated in this clinical situation, regardless of the patient's normal corneal thickness and low myopia. It might be possible to safely perform surface ablation on this patient in the future. Before such a procedure, I would want to document complete stability of the cornea with serial topographies over a few years. This patient might also benefit from PRK combined with corneal collagen cross-linking, either abroad or in the United States if and when the procedure is approved.
Section Editor Stephen Coleman, MD, is the director of Coleman Vision in Albuquerque, New Mexico. Dr. Coleman may be reached at (505) 821-8880; email@example.com.
Section Editor Parag A. Majmudar, MD, is an associate professor, Cornea Service, Rush University Medical Center, Chicago Cornea Consultants, Ltd.
Section Editor Karl G. Stonecipher, MD, is the director of refractive surgery at TLC in Greensboro, North Carolina.
Mitch Brown, OD, is the deputy medical director and optometry director for the Global Optical Express Group in San Diego, California. He acknowledged no financial interest in the products or companies he mentioned. Dr. Brown may be reached at firstname.lastname@example.org.
Yoshihiro Kitazawa, MD, PhD, is the chief medical director of Optical Express Japan, Kobe-Kanagawa Eye Clinic in Tokyo. He acknowledged no financial interest in the products or companies he mentioned. Dr. Kitazawa may be reached at email@example.com.
Colman R. Kraff, MD, is the director of refractive surgery for the Kraff Eye Institute in Chicago. He is a consultant to Abbott Medical Optics Inc. and on the IMAB for Optical Express. Dr. Kraff may be reached at (312) 444-1111; firstname.lastname@example.org.