EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.
Issue link: https://digital.eyeworld.org/i/104833
January 2013 general erudition that conclusions about cause-and-effect relationships cannot be drawn.5 Other limitations of the study design include a small sample size and insufficient follow-up time to establish safety. Mean follow-up in this study was 4.8 years. It is important to note that even though the majority of post-LASIK ectasia cases become clinically evident within the first 9-18 months, clinical observation and several reported cases show development of post-PRK ectasia as late as 5 and even 9 years after PRK.6,7,8 PRK may delay the onset of post-op keratectasia when compared to LASIK.9 As a result, longer followup times are necessary for an accurate assessment of PRK safety in KCS cases. In addition, only 33% of the patients were followed up at Rothschild Foundation, while 19% were telephoned by the investigators and were subjectively deemed to have no complications, while yet another 21% were completely lost to followup. This combined with the fact that the original number of patients included in the study was small leads to lack of study power. Assuming that patients lost to follow-up are satisfied with the results is an inappropriate assumption. In addition, the mean age of the patients was 34 years in this study, which is substantially later than the patients who have progressive disease and are at higher risk. This study is based on topography and does not consider curvature maps or pachymetry, which increases the possibility of false positives, and patients who are not keratoconus suspects may be falsely labeled. PRK in these patients would not be expected to have any complications in the first place. Also, even though the authors expressed that there were no cases of ectasia or any other complications in this study, there were at least three cases of myopic regression, which constitute a complication. Overall this study highlights the use of computerized systems for diagnosing keratoconus suspects; however, their clinical use needs to be determined taking into consideration different topographic indices for early detection of KC. Most importantly, whether PRK is safe or has a protective role for KCS corneas remains to be determined. Larger, prospective studies with longer follow-up periods are required. EW suspected keratoconus: five-year follow-up. J Cataract Refract Surg 2012. 2. Y.S. Rabinowitz. Videokeratographic indices to aid in screening for keratoconus. J Refract Surg, 11 (1995):371-379. 3. N. Maeda, S.D. Klyce, M.K. Smolek, H.W. Thompson. Automated keratoconus screening with corneal topography analysis. Invest Ophthalmol Vis Sci, 35 (1994):2749-2757. 4. Rabinowitz YS, Rasheed K. KISA% index: a quantitative videokeratography algorithm embodying minimal topographic criteria for diag- nosing keratoconus. J Cataract Refract Surg. 1999 Oct;25(10):1327-1335. 5. Guyatt G, Rennie D, eds. Users' guides to the medical literature. Essentials of EvidenceBased Clinical Practice. AMA Press 2002:136. 6. Spadea L. Collagen crosslinking for ectasia following PRK performed in excimer laserassisted keratoplasty for keratoconus. Eur J Ophthalmol. 2012 Mar-Apr;22(2):274-7. 7. Kim, Hyojin PhD; Choi, Jun-Sub PhD; Joo, Choun-Ki MD, PhD. Corneal Ectasia After PRK: EW RESIDENTS Clinicopathologic Case Report. Cornea. Aug 2006;25(7):845-848. 8. Reznik J, Salz JJ, Klimava A. Development of unilateral corneal ectasia after PRK with ipsilateral preoperative forme fruste keratoconus. J Refract Surg. 2008 Oct;24(8):843-7. 9. Stephen D Klyce. Chasing the suspect: keratoconus. Br J Ophthalmol 2009;93:845-847. Contact information Mian: smian@med.umich.edu The power of one The THE ONE FEMTO PLATFORM FE MTO PLATFORM AT for cornea, presbyopia cataract. for cornea, presbyopia and cataract. Presenting the unparalleled Ziemer FEMTO LDV Z Models – a technical revolution in ocular surgery. No laser is more precise, more powerful or more progressive when it comes to meeting all your procedural needs in a single platform. 53 With Ziemer's FEMTO LDV Z Models, now you can operate Ziemer's with a modular femtosecond system that is easy to configure, designed to grow with your practice – cornea and presbyopia today, cataract tomorrow. tomorrow. www.ziemergroup.com www.ziemergroup.com References 1. Guedi M, Saad A, Audureau E, Gatinel D. Photorefractive keratectomy in patients with The Ziemer FEMTO LDV Z Models are FDA cleared and CE marked and available for immediate delivery. For some countries, availability may be restricted due to local regulatory requirements; please contact Ziemer for details. The creation of a corneal pocket is availability part of a presbyopia intervention. Availability of related corneal inlays and implants according to policy of the individual manufacturers and regulatory status in the individual countries. Cataract procedures with the FEMTO LDV Z2, Z4 and Z6 models are not cleared manufacturers in the United States and in all other countries. An upgrade possibility for these devices is planned once cataract options are available and cleared by the responsible regulatory bodies.