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Biomedical subjects

Mark A Terry

Publications and source records attributed to Mark A Terry.

16 recordsLinked to original sources
PubMed2006

Topographic screening of donor eyes for previous refractive surgery.

PURPOSE: To determine whether donor eyes had previous refractive surgery using Orbscan (Bausch & Lomb Surgical) corneal topography. SETTING: Lions Eye Bank of Oregon, Portland, Oregon, USA, and Maisonneuve-Rosemont, Hospital, Montreal, Quebec, Canada. METHODS: Orbscan corneal topographies of 50 donor eyes from the Lions Eye Bank of Oregon were obtained; 10 eyes had previous refractive surgery (6 laser in situ keratomileusis, 2 photorefractive keratectomy, 2 radial keratotomy) to correct myopia, and 40 had not had surgery. Algorithms based on corneal anterior and posterior elevations and anterior tangential curvature were developed: The difference in curvature (DC) was based on the difference in the mean anterior tangential curvature between central and midperipheral areas; difference in elevation (DE) represented the difference between the anterior and posterior central elevations. Receiver-operating characteristic (ROC) curves for each algorithm were obtained, and sensitivity values at fixed specificities were calculated. RESULTS: The mean area under the ROC curve, which corresponds to the probability of correctly identifying the presence of a previous refractive surgery, was 0.853 +/- 0.079 (SE) for DC and 0.933 +/- 0.057 for DE. The DC algorithm resulted in a sensitivity of 80% for a specificity of 87.5%, and DE yielded a sensitivity of 90% for a specificity of 92.5%. There was a strong correlation between the value of the DE and DC algorithms and the amount of previous refractive surgery (DC: r = 0.84, P = .008; DE: r = 0.76, P = .028). CONCLUSION: The results led to a proposed criteria-based system using Orbscan corneal topography to screen eye-bank eyes for previous refractive surgery.

Adult↗
PubMed2006

Deep lamellar endothelial keratoplasty: early complications and their management.

PURPOSE: To report the early vision-threatening complications in a large series of deep lamellar endothelial keratoplasty (DLEK) procedures and discuss the management of these complications. METHODS: The first 100 consecutive patients to reach the 6-month postoperative gate of a prospective, institutional review board-approved protocol for DLEK surgery were reviewed for intraoperative and postoperative complications. The method of treatment of these complications and the outcome of that treatment were recorded. RESULTS: Two eyes (2 of 100 = 2%) were converted to PK at the time of DLEK surgery. Of the 98 patients who had complete DLEK surgeries, 4 eyes (4 of 98 = 4%) were noted to have a dislocated disk on the first postoperative day. The dislocated disk in each case was repositioned in a short, often topical anesthesia technique, and all corneas cleared. One eye had primary graft failure (caused by surgeon error) resulting in disk dislocation. It was successfully replaced with another disk on postoperative day 1. Four patients (4 of 98 = 4%) experienced graft rejection of the donor disk from stopping steroids, but all grafts cleared with restarting of steroids. One patient required surgery for steroid-aggravated glaucoma. In the 5 cases of DLEK surgery in which the clear crystalline lens was left in place, no cataracts were induced at the 6-month postoperative gate. There were no infections, ulcerations, healing defects, or late dislocations. No patient required a contact lens, relaxing incision, or LASIK for residual refractive error. CONCLUSIONS: DLEK surgery is technically challenging, and yet complications from the surgery in our series were relatively rare and easily resolved. By eliminating sutures and high astigmatism, DLEK surgery avoids the usual complications often associated with transplant surgery.

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PubMed2006

Histology of dislocations in endothelial keratoplasty (DSEK and DLEK): a laboratory-based, surgical solution to dislocation in 100 consecutive DSEK cases.

PURPOSE: Laboratory studies were performed to evaluate the histologic differences between the recipient bed after deep lamellar endothelial keratoplasty (DLEK) surgery and Descemet's-stripping endothelial keratoplasty (DSEK) surgery. Relevant new surgical strategies to prevent dislocation in DSEK surgery were initiated in our first 100 consecutive clinical cases. METHODS: Ten pairs of cadaver eyes had a DLEK in 1 eye and a DSEK in the fellow eye, and the posterior stromal surface was analyzed by scanning electron microscopy at x50 magnification. Based on the findings in these cadaver eyes, our DSEK procedure was modified to include surgical roughening in the peripheral recipient bed in 100 consecutive eyes. One hundred percent of these eyes were followed for at least 60 days after surgery to determine the rate of donor dislocation. RESULTS: In all 10 pairs of cadaver eyes, the DSEK stromal interface showed a smoother surface than DLEK eyes, without the presence of cut stromal fibrils. The DLEK surface was less smooth than the DSEK eyes, but with the presence of uniformly cut fibrils over the entire surface. Subsequent surgical modifications to the DSEK procedure to include scraping and roughening of the recipient peripheral bed in humans resulted in only a 4% (4/100) dislocation rate of the donor tissue into the anterior chamber. One of these 4 dislocated donors was seen on the first postoperative day and was the only primary graft failure in the series. The other 3 cases were fully attached on the first postoperative day with no interface fluid, but they dislocated later on postoperative days 2, 3, and 4. CONCLUSION: The high rate of dislocation of the donor disc in DSEK may be caused by the absence of recipient stromal fibrils to initially bind to the donor stromal fibrils. Clinical success with a surgical technique of selectively scraping the peripheral recipient bed to promote donor edge adhesion (while leaving the central bed untouched for vision) may aid in the prevention of donor dislocation in DSEK surgery. Reduction of dislocation in DSEK surgery has also been associated with a reduced rate of iatrogenic primary graft failure (PGF) to 1%.

Corneal Diseases↗
PubMed2005

Stability of vision, topography, and endothelial cell density from 1 year to 2 years after deep lamellar endothelial keratoplasty surgery.

PURPOSE: To evaluate whether the visual, topographic, and endothelial cell count results observed 1 year after deep lamellar endothelial keratoplasty (DLEK) surgery remain stable up to 2 years after surgery. DESIGN: Prospective, noncomparative, interventional case series. PARTICIPANTS: Twenty eyes of 20 patients with corneal edema from Fuchs' endothelial dystrophy. METHODS: Deep lamellar endothelial keratoplasty endothelial replacement surgery, with a 9.0-mm or 9.5-mm scleral access incision and a specialized intrastromal trephine, was performed. Snellen visual acuities, corneal topography, and endothelial cell counts were prospectively measured preoperatively and 1 year and 2 years after DLEK. MAIN OUTCOME MEASURES: Uncorrected and best spectacle-corrected visual acuity (BSCVA), refractive and topographic astigmatism, mean corneal curvature, topographic regularity and symmetry, and endothelial cell density. RESULTS: At 1 year postoperatively, BSCVA averaged 20/50 (range, 20/25-20/200), spherical equivalents (SE) averaged -0.194+/-1.521 diopters (D), manifest refraction (MR) astigmatism averaged 2.04+/-1.05 D (range, 0.0-4.0 D), topographic astigmatism averaged 2.3+/-1.1 D, mean corneal curvature was 43.2+/-1.8 D, the surface regularity index (SRI) averaged 1.16+/-0.41, and the surface asymmetry index (SAI) averaged 1.05+/-1.09. At 2 years postoperatively, BSCVA averaged 20/48 (range, 20/25-20/200), SE averaged -0.369+/-1.267 D, MR astigmatism averaged 1.76+/-0.66 D (range, 0.75-3.0 D), topographic astigmatism averaged 2.4+/-1.1 D, mean corneal curvature was 43.6+/-1.8 D, the SRI averaged 1.13+/-0.44, and the SAI averaged 0.76+/-0.59. There was no significant change in visual or topographic parameters between 1 year and 2 years postoperatively (P>0.05). Endothelial cell counts averaged 2335+/-468 cells/mm(2) at 1 year and 2151+/-457 cells/mm(2) at 2 years postoperatively (P = 0.041). CONCLUSIONS: Deep lamellar endothelial keratoplasty provides stable refractions, corneal topography, and endothelial cell densities as long as 2 years after surgery. The absence of corneal sutures in this technique seems to prevent the sutures in/sutures out changes in SE refractions and corneal topography sometimes seen after penetrating keratoplasty (PK). Deep lamellar endothelial keratoplasty is, therefore, an excellent alternative to PK for patients with endothelial dystrophies.

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PubMed2005

Deep lamellar endothelial keratoplasty visual acuity, astigmatism, and endothelial survival in a large prospective series.

PURPOSE: To report the 6-month results for the treatment of endothelial dysfunction in a large, prospective series of deep lamellar endothelial keratoplasty (DLEK) procedures. DESIGN: Prospective, noncomparative, interventional case series. PARTICIPANTS: One hundred eyes of 88 patients with corneal edema from Fuchs' dystrophy and pseudophakia. METHODS: A limbal, scleral, partial-depth incision provided access for a deep lamellar corneal pocket dissection. Two eyes were converted to penetrating keratoplasty (PK) at the time of DLEK surgery because of poor dissections. Of the 98 eyes that had completed DLEK surgeries, 36 eyes received a large-incision technique (9-mm scleral access incision) and 62 eyes received a small-incision technique (5-mm scleral access incision). A 7.5- to 8.0-mm posterior lamellar disc of recipient tissue then was excised and replaced through the pocket with a similar size donor disc containing healthy endothelium. A temporary air bubble in the anterior chamber was used for donor tissue adherence, and no surface corneal incisions or sutures were necessary. MAIN OUTCOME MEASURES: Preoperative and postoperative best spectacle-corrected visual acuity (BSCVA), manifest refraction (MR) astigmatism, and endothelial cell density (ECD) were evaluated prospectively. RESULTS: At 6 months after surgery, all 98 DLEK corneas were clear and the grafts were healed in good position. The mean BSCVA was 20/46, with a range between 20/20 and 20/400. The average MR astigmatism was 1.34+/-0.86 diopters (D), representing an average change in astigmatism from before surgery of +0.28+/-1.08 D (P = 0.013). The average ECD at 6 months was 2140+/-427 cells/mm2, representing a mean cell loss from preoperative donor cell measurements of 25%. CONCLUSIONS: The DLEK procedure, with its absence of corneal surface incisions and sutures, preserves the normal corneal topography, minimizes astigmatism, and provides a healthy donor endothelial cell count and function. The DLEK procedure represents a reasonable alternative to PK, and compared with historical PK data, offers superior refractive outcomes in the treatment of endothelial dysfunction.

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PubMed2005

Small-incision deep lamellar endothelial keratoplasty (DLEK): six-month results in the first prospective clinical study.

PURPOSE: To evaluate the visual, topographic, and endothelial survival results in 25 consecutive patients who have received small-incision deep lamellar endothelial keratoplasty (DLEK) transplant surgery. METHODS: DLEK surgery was performed in 25 patients with Fuchs endothelial dystrophy or pseudophakic bullous keratopathy utilizing a 5-mm scleral access incision. Snellen visual acuities, refractive astigmatism, endothelial cell counts, and corneal topography were prospectively measured at preop and at 6 months after small-incision DLEK endothelial replacement surgery. RESULTS: Best spectacle-corrected visual acuity improved from an average of 20/90 (range 20/25 to 2'/200) before surgery to an average of 20/44 (range 20/25 to 20/200, P < 0.001) 6 months after surgery, with 56% of patients 20/40 or better at 6 months. Average refractive astigmatism at 6 months was 1.31 +/- 0.59 diopters (range 0.25 to 2.50 diopters), representing an average increase in astigmatism of 0.45 diopters from preop. Despite folding of the donor graft for placement into the recipient posterior lamellar bed, the average postoperative endothelial cell count at 6 months was 2122 +/- 510 cells/mm2 (range 1097 to 3202 cells/mm2) or an average 24% cell loss from donor eye preop measurements, a level of cell loss comparable to that reported after PK or after large-incision DLEK surgery. CONCLUSION: Small-incision DLEK surgery preserves the recipient corneal topography, resulting in very little change in astigmatism from preop. The excellent postoperative donor endothelial cell counts attest to the survival of donor endothelium despite folding of the graft for insertion. The small-incision DLEK technique may become the standard for endothelial replacement surgery in the future.

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PubMed2005

A practical femtosecond laser procedure for DLEK endothelial transplantation: cadaver eye histology and topography.

PURPOSE: The manual dissection technique for deep lamellar endothelial keratoplasty (DLEK) surgery is technically difficult and may not be smooth enough for consistently optimal postoperative vision. We evaluated the feasibility and efficacy of using a femtosecond laser to perform the dissections in the DLEK procedure. METHODS: The Intralase femtosecond laser (with standard LASIK surgery spot settings) was used to create a 9.4-mm wide, 400-microm deep lamellar pocket dissection and a 5.0-mm wide side cut near-exit incision in 10 "recipient" whole cadaver eyes and in 10 "donor" cadaver corneal-scleral caps mounted onto an artificial anterior chamber. Recipient and donor disks were resected with special scissors, and the donor tissue was transplanted using the small incision (5.0-mm) DLEK technique. Topography of the recipient eyes was measured pre- and postlaser dissection, and the recipient and donor tissues were sent for scanning electron microscopy (SEM) analysis of the smoothness of the dissections. RESULTS: Successful lamellar dissections were obtained in all tissues. The mean recipient topographic corneal curvature postoperatively was 43.3 +/- 1.7 diopters, which was not a significant change from the preoperative curvature of 44.0 +/- 0.8 diopters (P = 0.430). The mean recipient topographic astigmatism postoperatively was 1.7 +/- 0.8 diopters, which was not a significant change from the preoperative recipient astigmatism of 1.6 +/- 0.7 diopters (P = 0.426). Comparison of the histology of the laser-formed stromal dissections by scanning electron microscopy, however, did not appear significantly better than histology after manual DLEK dissections in either the recipient or the donor tissues. CONCLUSIONS: A femtosecond laser can create the lamellar dissections for the DLEK procedure, making this procedure easier and faster. As in the manual technique, corneal topography is unchanged by this surgery. More work will need to be done, however, to optimize the laser settings to provide even smoother interface surfaces.

Astigmatism↗
PubMed2005

Deep lamellar endothelial keratoplasty: surgery in complex cases with severe preoperative visual loss.

PURPOSE: This study was designed to report the use of deep lamellar endothelial keratoplasty (DLEK) in combination with other intraocular surgeries in the treatment of eyes with severe bullous keratopathy and visual loss. METHODS: DLEK surgery was performed in six patients with severe bullous keratopathy and preoperative vision with a range of between count fingers and light perception only. DLEK was combined with vitrectomy and placement of a ciliary sulcus sutured intraocular lens in four patients and with cataract surgery in one patient. Two patients with vitreoretinal disease underwent pars plana vitrectomy within only 4 months after the DLEK donor tissue had been placed. Graft clarity, Snellen visual acuities, refractive astigmatism, endothelial cell counts, and corneal topography were prospectively measured at 6 and 12 months postoperatively. RESULTS: At 6 months after DLEK surgery, all grafts were clear and vision improved in all patients. Best spectacle-corrected visual acuity improved from count fingers level (or worse) before surgery to a range of 20/40 to 20/200 after surgery. Average refractive astigmatism at 6 months was 2.0 diopters (range, 0.50-4.00 diopters). The average postoperative endothelial cell count was 1,679 +/- 380 (range, 1,200-2,298) cells/mm at 6 months and 1,449 +/- 365 (range, 1,105-2,043) cells/mm at 12 months. Vitreoretinal surgery subsequent to graft placement did not affect corneal clarity or dislodge the grafted tissue. CONCLUSIONS: DLEK surgery can be used in cases with severe visual loss caused by bullous keratopathy with transfer of healthy donor endothelium, clearing of the central cornea, and restoration of useful vision. DLEK also can be successfully combined with other intraocular surgeries such as vitrectomy, intraocular lens exchange, and sutured intraocular lens surgery. The DLEK graft can tolerate subsequent intraocular surgery performed as early as 3 months after placement of the donor tissue.

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PubMed2004

Rapid visual rehabilitation after endothelial transplants with deep lamellar endothelial keratoplasty (DLEK).

OBJECTIVE: To evaluate the speed of visual recovery in 30 consecutive patients with Fuchs endothelial dystrophy who received deep lamellar endothelial keratoplasty (DLEK) transplant surgery. METHODS: Best spectacle-corrected visual acuity (BSCVA) by manifest refraction and uncorrected visual acuity (UVA) were prospectively measured at preop, at 1 week, and at 1, 3, 6, 12, and 18 months after DLEK. The LogMAR of the postop vision was compared against each patient's preop vision. Visual results at 6 months were also compared against potential acuity meter (PAM) results in 27 patients. All eyes had reached at least the 6-month follow-up interval. RESULTS: Two of the first 32 eyes originally enrolled in the protocol were converted at surgery to standard penetrating keratoplasty (PK), and so DLEK data were obtained on 30 eyes for this report. Average BSCVA and UVA were better than preop vision at every time point, achieving statistical significance by 3 months (P < 0.05). Average preop BSCVA was 20/162 (range 20/40 to CF), improving to 20/63 at 3 months (range 20/25 to 20/200), 20/56 at 6 months, 20/51 at 1 year, and 20/46 at 18 months. Of the 27 patients who had PAM testing, 52% (14 of 27) had BSCVAs within 1 line of their PAM at 3 months, 63% (17 of 27) were within 1 line at 6 months, 71% (12 of 17) were within 1 line at 1 year, and 83% (10 of 12) were within 1 line at 18 months (P < 0.05 compared with preop from 3 months on). CONCLUSION: DLEK surgery preserves the normal corneal surface topography and allows rapid visual recovery of useful vision by 3 months. The visual acuity continues to improve over time.

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PubMed2003

Replacing the endothelium without corneal surface incisions or sutures: the first United States clinical series using the deep lamellar endothelial keratoplasty procedure.

PURPOSE: To report the 6- and 12-month results of the first United States clinical series of deep lamellar endothelial keratoplasty (DLEK) in the treatment of endothelial dysfunction. DESIGN: Prospective, noncomparative, interventional case series. PARTICIPANTS: Eight eyes of eight patients with corneal edema from Fuchs' dystrophy and pseudophakia. METHODS: A 9.0-mm limbal, scleral, partial-depth incision provided access for a deep lamellar corneal pocket dissection. A 7.5- to 8.0-mm posterior lamellar disc of recipient tissue was then excised and replaced through the pocket with a same size donor disc containing healthy endothelium. A temporary air bubble in the anterior chamber was used for donor tissue adherence, and no surface corneal incisions or sutures were necessary. MAIN OUTCOME MEASURES: Preoperative and postoperative best spectacle-corrected visual acuity (BSCVA), manifest refraction astigmatism, TMS-1 topography, ultrasonic pachymetry, Orbscan topography, and endothelial cell density were evaluated. Intraoperative and postoperative complications are reported. RESULTS: At 6 and 12 months after surgery, all eight corneas were clear and the grafts were healed in good position. At 6 months, the BSCVA varied between 20/30 and 20/70, the average change in astigmatism from before surgery was +1.13 diopters (D; +/-1.50 D), the average change in corneal power was -0.4 D (+/-1.7 D), the average pachymetry was 648 micro m (+/-134 micro m), and the average endothelial cell count was 2290 cells/mm(2) (+/-372 cells/mm(2)). At 12 months, three of the four eyes reaching this time gate were 20/40 or better, with a change in astigmatism from before surgery of only +0.81 D (+/- 0.55 D), a corneal power change of -1.3 D (+/- 0.4 D), and an endothelial density of 2409 cells/mm(2) (+/- 154 cells/mm(2)). One of the original nine eyes entered into this study required conversion to standard penetrating keratoplasty as a result of a microperforation during recipient pocket dissection and has experienced no ill effects. CONCLUSIONS: The DLEK procedure, with its absence of corneal surface incisions and sutures, is a safe procedure that preserves the normal corneal topography, minimizes astigmatism and corneal power changes, and provides a healthy donor endothelial cell count and function. If interface optical clarity can be maintained, then this technique offers considerable advantages over penetrating keratoplasty in the treatment of endothelial dysfunction.

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PubMed2003

Endothelial replacement: the limbal pocket approach.

The limbal pocket approach to endothelial replacement shows extraordinary promise in fulfilling the ideal goals of surgical treatment for endothelial dysfunction. From its inception, DLEK surgery has demonstrated that, by preserving the limbus and eliminating surface corneal incisions and sutures, the corneal topography can be stabilized with little change from preoperative measurements of astigmatism and corneal power. The surgical dissection planes of DLEK surgery are inherently stronger than that of PK or any other form of endothelial replacement, allowing early stability of the refraction and making the eye safer from blunt trauma over the long term. Further work with DLEK must be performed in perfecting the optical properties of the stromal interface before this technique can be used widely; however, as technology and techniques improve, DLEK surgery holds the promise of being the ideal method for endothelial replacement in the 21st century.

Corneal Diseases↗
PubMed2003

In pursuit of emmetropia: spherical equivalent refraction results with deep lamellar endothelial keratoplasty (DLEK).

PURPOSE: To determine if the new technique for endothelial transplantation of DLEK (deep lamellar endothelial keratoplasty) can offer predictable corneal curvature and improved refractive spherical equivalent results compared with reports for traditional penetrating keratoplasty. METHODS: Twenty-seven consecutive Fuchs corneal dystrophy patients received DLEK surgery to replace their endothelium. Topographic corneal curvature and refractive spherical equivalents were evaluated at preop and at 6 and 12 months postop. RESULTS: At 6 months (n = 27) the average corneal curvature was 43.8 +/- 1.4 D, representing a mean change from preop corneal curvature of only -0.1 +/- 1.7 D. At 12 months (n = 18) the average corneal power was 43.5 +/- 1.7 D. The average corneal curvature at 6 and 12 months was not significantly different from pre-op (P = 0.119). The average refractive spherical equivalent result at 6 months was -0.44 +/- 1.7 D, and at 12 months was -0.44 +/- 1.6 D. The 6- and 12-month refractive spherical equivalent results were not statistically different from the preop spherical equivalent refractions (P = 0.922). All patients could be easily refracted, and several patients were fit with stable glasses as early as 3 months after DLEK surgery. CONCLUSION: DLEK surgery preserves the preoperative corneal curvature and therefore allows better matching of postop corneal curvature to the IOL power. This increase in predictability of the postoperative corneal curvature makes the choice of IOL power for the new "triple procedure" more accurate, eliminates the need for contact lens wear after PK, and provides earlier visual rehabilitation after endothelial replacement.

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PubMed2002

Objective screening methods for prior refractive surgery in donor tissue.

PURPOSE: Laser refractive surgery presents a growing contamination of the available corneal donor pool. There currently is no objective method for screening donor tissue for previous refractive surgery. We evaluated the usefulness of pachymetry and curvature maps in the screening of donor corneas. METHODS: Pachymetry and curvature maps were generated from the Orbscan for 40 normal donor eyes. The average central pachymetry measurement was subtracted from the thinnest average midperipheral pachymetry measurement for each map to generate a normal range of pachymetry measurements. For curvature, the average curvature at the 3-mm zone was subtracted from the average curvature at the 7-mm zone to generate a normal range of corneal curvature. The pachymetry and curvature results from 10 donor eyes that had undergone refractive surgery were then compared with the normal range for each technique. RESULTS: The average difference in pachymetry measurements between the midperipheral and central cornea for normal eyes was 0.040 +/- 0.026 mm. Four of 10 corneas that had undergone refractive surgery were outside two standard deviations of this normal range. The average difference in corneal curvature between the 7-mm zone and the 3-mm zone for the healthy eyes was -0.2 +/- 1.0 diopters. Four (40%) of 10 corneas that had undergone refractive surgery were identified with this method. When combined, the pachymetry and curvature methods detected seven (70%) of 10 corneas that had undergone refractive surgery. CONCLUSION: Regional differences in thickness and curvature in donor eyes may provide methods for screening for refractive surgery for myopia. Refinement in mathematical manipulations may further improve the sensitivity of these techniques.

Adult↗
PubMed2002

Use of a portable topography machine for screening donor tissue for prior refractive surgery.

PURPOSE: We investigated whether a portable, hand-held topography unit could be used to measure corneal topography either at the donor site or in the laboratory and whether the technology could be used to screen donor eye tissue for prior refractive surgery. METHODS: The corneal topography of 22 eyes of 12 normal donors was measured with the Keratron Scout portable topography machine before and after whole-eye enucleation. Field and laboratory measurements of central curvature, astigmatism, and the difference between the corneal curvature at the 7-mm and the 3-mm zone were compared. The 7-mm and 3-mm zone curvature differences were also used to screen for eyes that had undergone refractive surgery. RESULTS: The mean central curvature of the normal eyes in the field [43.28 +/- 1.58 diopter (D)] was not significantly different from the mean curvature in the laboratory (43.52 +/- 1.72 D; p= 0.20). Field and laboratory astigmatism was 2.02 +/- 1.13 D and 1.64 +/- 1.38 D, respectively (p = 0.26, not significant). The eyes had a normal prolate shape, with the corneal power less in the periphery than in the center (mean difference between the 7-mm and 3-mm zone of -1.48 +/- 0.83 D in the field and -1.77 +/- 0.73 D in the lab; = 0.069). Field and laboratory measurements of corneal shape correlated well with each other. Eight of eight eyes with refractive surgery for myopia and one of two eyes with hexagonal keratotomy for hyperopia were outside 2 SD of the normal range. CONCLUSION: The Scout can be used to measure corneal topography at the donor site and in the eye bank laboratory with comparable results. Regional power differences between the corneal periphery and center could be used as a method for screening donor eyes for prior refractive surgery.

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