CLINICAL SCIENCES Slitlamp, Specular, and Light Microscopic Findings of Human Donor Corneas After Laser-assisted In Situ Keratomileusis V. Vinod Mootha, MD; Dan Dawson, MD; Amit Kumar, MD; Joel Gleiser, MD; Clifford Qualls, PhD; Daniel M. Albert, MD Objective: To examine slitlamp, specular, and light mi- slitlamp examination, of which 3 were confirmed by his- croscopic features of human donor corneas known to have topathologic examination. Highly reflective particles were undergone laser-assisted in situ keratomileusis (LASIK). seen by specular microscopy in the stroma of 23 (88%) of 26 LASIK donor corneas, but only 1 (4%) of 26 con- Methods: Twenty-six donor corneas known to have un- trol donor corneas had a single highly reflective particle dergone LASIK prospectively underwent slitlamp exami- in the stroma (PϽ.001). The mean central endothelial nation with particular attention to the presence of a flap cell counts were similar: 2138 cells/mm2 in the LASIK edge, as well as specular microscopy with particular at- group compared with 2250 cells/mm2 in the controls tention to the presence of highly reflective particles in (P=.39). Vacuolization and pyknosis of keratocytes the stroma corresponding to the LASIK interface. Cen- was a consistent histopathologic finding after LASIK. tral endothelial cell density and pachymetery were ob- Metallic particles at the interface were not detected by tained. They were compared with 26 control donor cor- histology. neas without LASIK. Eleven LASIK donor corneas were processed for histology. Twenty-six donor corneas with Conclusions: Detection of a flap edge by slitlamp ex- no known prior keratorefractive surgery also under- amination may detect at least half of the donor corneas went similar slitlamp examination and specular micros- that may have undergone LASIK. The detection of highly copy to serve as controls. reflective stromal particles may form an effective basis for screening for LASIK donor corneas using specular mi- Results: Twelve (46%) of 26 LASIK donor corneas had croscopy and requires further study. an obvious flap edge, and 10 (39%) had a subtle flap edge by slitlamp examination. Four (15%) had infiltrates by Arch Ophthalmol. 2004;122:686-692 N 2001, THE 80 EYE BANKS OF THE quired to protect the donor cornea pool. Eye Bank Association of America Corneal topography and pachymetry,3,4 provided tissue for 46532 cor- videokeratography,5,6 dark-field biomi- neal transplantation proce- croscopy,7 wavefront analysis,8 and opti- dures.1 With millions of proce- cal coherence tomography9 have been pro- Idures already performed in the United posed as screening tools for the detection States, the increasing popularity of laser- of previous refractive surgery. However, assisted in situ keratomileusis (LASIK) none of these instruments are readily avail- threatens the donor cornea pool. Cor- able at most eye banks. From the Division of neas that have had any previous refrac- The in vivo confocal microscope con- Ophthalmology, Department tive surgery are not suitable for transplan- sistently demonstrates the presence of vari- of Surgery, The University tation because of structural and optical able reflectivity particles in the corneal in- of New Mexico Health Sciences compromise to the tissue. Michaeli- terfaces of all patients after LASIK.10,11 Center and School of Medicine, Cohen et al2 described 2 patients who un- Pisella et al10 speculate that the highly re- and New Mexico VA Health derwent penetrating keratoplasty by sur- flective interface particles consist of me- Care System, Albuquerque geons who were unaware that the donor tallic particles originating from the mi- (Drs Mootha and Qualls); and eyes had previous LASIK. In one of these crokeratome blade and the less reflective Department of Ophthalmology cases, separation of the corneal lamellae particles may represent cellular debris or and Visual Sciences, University 11 of Wisconsin, Madison was noted at the time of surgery. plastic particles. Gokmen et al used the (Drs Dawson, Kumar, Gleiser, Eye banks rely primarily on the medi- presence of the highly reflective particles and Albert). The authors have cal and social history interview to detect found in all examined patients with the in no relevant financial interest in donors who have had previous refractive vivo confocal microscope as a basis to mea- this article. surgery. New screening techniques are re- sure the thickness of the LASIK flap. In an- (REPRINTED) ARCH OPHTHALMOL / VOL 122, MAY 2004 WWW.ARCHOPHTHALMOL.COM 686 ©2004 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/25/2021 other recent confocal microscope study,12 highly reflec- tive particles were found in the anterior stroma in 78 of Table 1. Demographics of Laser-assisted In Situ 85 confocal scans performed after LASIK. Like the con- Keratomileusis (LASIK) Donor Corneas and Controls focal microscope, the specular microscope is a reflected LASIK Controls P light microscope. The specular microscope is readily avail- Demographic (n = 26) (n = 26) Value* able at eye banks and is used to study the endothelial cell count density and morphologic structure in donor cor- Male/female ratio 16:10 12:14 .40 Age, mean, y 50 66 Ͻ.001 neas. This study attempted to determine the usefulness Death to preservation time, h 11.7 8.8 .10 of the specular microscope to detect the presence of the Days after death of specular 5.8 6.0 .90 highly reflective particles in the region of the central microscopy of stroma stroma corresponding to an interface in donor corneas Days after death of specular 4.8 2.5 .01 known to have had LASIK. To our knowledge, this study microscopy of endothelium is the first to examine the endothelium of donor corneas after LASIK surgery. The specular microscope was also *All t tests except for Fisher exact test of sex. used to assess central endothelial cell density and cen- tral corneal pachymetry measurements. This study also cell area ϫ100) and percentage of hexagonal cells were calcu- attempted to determine the usefulness of the slitlamp to lated by the software of the Keratoanalyzer specular micro- identify the LASIK flap edge in postmortem eyes. scope. Central pachymetry measurements were obtained on each cornea optically by focusing from the endothelium to the epi- In this study, we looked at the histologic findings thelium using the z-axis knob. The z-axis knob was used to of 11 of these LASIK donor corneas. One other histo- search for highly reflective central stromal particles starting from 13 logic study of human corneas after successful LASIK a depth of 150 µm from the endothelium. The paracentral stroma included only 4 corneas. Other reports of histologic was examined by use of the x-axis and y-axis knobs on the mi- changes in human corneas involved corneal button speci- croscope platform. The central stroma was examined at 25-µm mens after penetrating keratoplasty for LASIK-related increments toward the epithelium. The specular microscope complications14-16 or phthisical blind eyes in which the was sharply focused on any highly reflective particle in the procedure was performed just before enucleation.17 stroma, and its depth from the endothelium was noted. The maximum number of particles in any field observed was counted in each cornea. Twenty-six donor corneas already present at METHODS the New Mexico Lions Eye Bank with no known history of prior keratorefractive surgery underwent similar slitlamp examina- This project was approved by the Human Research Review Com- tion and specular microscopy to serve as controls. mittee of The University of New Mexico Health Sciences Cen- Eleven LASIK donor corneas were placed in 10% neutral ter. With use of the medical and social history interview, par- buffered formalin and processed for permanent sections. Five- ticipating eye banks of Tissue Banks International (Baltimore, micron serial sections from the center of the donor corneas were Md) identified potential donor corneas that had undergone obtained. They were examined under light microscopy (origi- LASIK. After consent for research was obtained, the corneas nal magnification, ϫ20 to ϫ400) after being stained with he- were removed by in situ excision and were placed in vials with matoxylin-eosin and periodic acid–Schiff. Optisol-GS corneal storage medium (Chiron Ophthalmics, Ir- The refractive data of the LASIK donors, including the pre- vine, Calif) by eye bank technicians using established proto- operative manifest refraction, preoperative pachymetry, date cols of the Eye Bank Association of America.18 Central endo- of LASIK, microkeratome used, footplate depth, and amount thelial cell counts were obtained by the participating eye bank of ablation, were obtained if possible. The collected data were responsible for harvesting the cornea. The corneas were sent to entered into an Excel spreadsheet (Microsoft Corp, Redmond, the New Mexico Lions Eye Bank, Albuquerque, using protocols Wash), and analyses were performed with SAS statistical soft- established by the Eye Bank Association of America.18 The do- ware, version 8.02 (SAS Institute, Cary, NC). nor corneas were stored at 4°C until further examination. Twenty-six donor corneas known to have undergone LASIK RESULTS prospectively underwent slitlamp examination with particu- lar attention to the presence of a flap edge. A cornea fellowship– Demographic information on the LASIK donor corneas trained investigator (V.V.M.) used the slitlamp examination to and controls is given in Table 1. The mean donor age rate the LASIK flap edge as “obvious,” “subtle,” or “absent.” among the LASIK corneas (50 years) was younger than The LASIK donor corneas with an absent flap edge were con- Ͻ firmed to have had the refractive surgery by histopathologic that among the controls (66 years) (P .001). On aver- examination. These corneas then underwent thorough specu- age, specular microscopic examination of the endothe- lar microscopy with the Konan Eyebank Keratoanalyzer (Ko- lium occurred 4.8 days after death in the LASIK group nan Medical, Tokyo, Japan) with attention to the presence of compared with 2.5 days in the controls (P=.01).