Laser thermal keratoplasty for PRK overcorrection: Author’s reply

Abstract

The manuscript entitled, “Laser Thermal Keratoplasty for the Treatment of Photorefractive Keratectomy Overcorrections: A 1-Year Follow-up” (Ophthalmology 1998; 105: 926–31) was originally submitted in December, 1996. LTK is a recent technology and its limitations are not completely known. Since the initial submission to the journal, it is possible that new nomograms may have been developed to improve the results. The conclusions of the article published in Ophthalmology were based on the data and the clinical judgment that I acquired during the practice of the LTK technique. Dr. Kliger’s analysis of the results is focused on achieved refractions, as based on the ±0.5 or the ±1.0 D of emmetropia. In his letter, the initial problem of patients having a PRK overcorrection is ignored. All results are clearly specified in the article, including the percentage of eyes having equal or greater sphere than before the LTK (see Table 4), which, in fact, represents the percentage of eyes that did not respond to the treatment. For the PRK overcorrections, one-third of the patients did not respond to the treatment (see Table 4). Dr. Kliger states that “we cannot allow seemingly attractive aggregate statistics to override common sense.” I totally agree with such an opinion. However, the percentage of eyes within emmetropia is not the only issue in this study. Although some patients did not respond to the treatment, no loss of best-corrected visual acuity, no clinically significant scars, and no surgical complications were generated by the LTK post-PRK; the procedure did not put the patient’s visual quality at risk. However, some patients did respond to the treatment, making the procedure useful for them. A myopic patient who becomes a hyperope, even if it is low hyperopia, is usually quite disoriented and feels handicapped. The patient complains about loss of visual quality, and ultimately, about loss of quality of life. The correction of low overcorrected PRK patients, using LTK, can dramatically enhance the visual quality of some patients (actually, two-thirds). So it seems reasonable to propose a solution that will help two-thirds of these patients. Moreover, LTK does not jeopardize the use of further refractive surgery. I have performed hyperopic laser in situ keratomileusis and hyperopic PRK, using a scanning excimer laser, on eyes that were previously treated with LTK and needed further retreatment. Twelve months after the final retreatment, these eyes, from patients in the study, did not lose any lines of best-corrected visual acuity. However, 67% of them were between ±1.0 D of emmetropia and all were between ±2.0 D of emmetropia. At 12 months postoperatively, mean sphere was 0.5 ± 1.0 D. Ninety percent of these eyes had uncorrected visual acuity of 20/40 or better, and 60% of them had 20/25 or better. As one can see, nothing is still perfect, even if some patients may endure a +0.75 to a +1.0 D of remaining hyperopia and still be satisfied. In my experience, the best method to treat a PRK overcorrection is to avoid it, precisely as mentioned in the original manuscript of the study. The outcomes and low risks of LTK for low hyperopia (below +2 to +3 D) have already been reviewed and approved by other authors.1Koch D.D. Abarca A. Villarreal R. et al.Hyperopia correction by noncontact holmium: YAG laser thermal keratoplasty. Clinical study with two-year follow-up.Ophthalmology. 1996; 103: 731-740Abstract Full Text PDF PubMed Scopus (72) Google Scholar, 2Alio J.L. Ismail M.M. Sanchez Pego J.L. Correction of hyperopia with non-contact Ho YAG laser thermal keratoplasty.J Refract Surg. 1997; 13: 17-22PubMed Google Scholar LTK is not an invasive surgery and may create less complications than other types of refractive surgery. Generally speaking, one should be aware that regression of about 0.5 to 1.0 D can happen for some patients after LTK surgery. That is why I would recommend limiting the use of LTK to about +2 D of hyperopia, so that most patients would be within the ±1 D of emmetropia. I do not think that overcorrected patients should wait until an all-secured method is available. I hope that this letter will clarify my clinical evaluation of LTK for PRK overcorrections.