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Purpose. To present the results of photorefractive keratectomy (PRK) for treatment of laser in situ keratomileusis (LASIK) flap complications. Methods. Compilation of case reports through solicitation on Kera-net, an Internet surgery discussion site. Results. PRK was performed on 13 patients from 2 weeks to 6 months after LASIK flap complications. The technique used for the PRK varied. Epithelial removal was performed using no-touch phototherapeutic keratectomy (PTK) in six of the 13 patients and manual debridement in the other seven patients. A dilute solution of 20% ethanol was used to facilitate manual debridement in five of the seven patients. In two of these five patients, the epithelium was replaced as in laser-assisted subepithelial keratomileusis (LASEK). A solution of 0.02% mitomycin C was used after laser ablation to prevent haze formation in three patients. After an average 7 months of follow-up, uncorrected visual acuity was 20/20 in six patients, 20/25 in four patients, and 20/30 in two patients. The visual acuity in one patient was 20/80, purposely left under-corrected for monovision. Best spectacle-corrected visual acuity was 20/20 in 10 of 13 patients. Three patients were 20/25, losing one line of best spectacle-corrected visual acuity. On slit-lamp examination, at last follow-up appointment, stromal haze was graded from trace to none in all patients. Conclusions. Photorefractive keratectomy is a safe and effective technique for treatment of patients with LASIK flap complications.

Objective To assess the safety and effectiveness of the LADARVision active tracking narrow beam excimer laser system (Alcon Surgical, Orlando, FL) using laser in situ keratomileusis (LASIK) for correction of spherical hyperopia, hyperopic astigmatism, and mixed astigmatism. Design A multicenter, prospective non-randomized (self-controlled) comparative trial. Participants A total of 360 eyes, including 152 spherical hyperopic, 143 hyperopic astigmatic, and 65 mixed astigmatic, were treated for up to +6.00-diopter (D) sphere with up to −6.00-D cylinder. Intervention Treatments were performed at six sites in the United States using a 6-mm optic zone with a 1.5-mm peripheral blend zone for a maximum ablation zone diameter of 9 mm. Main outcome measures Uncorrected visual acuity (UCVA), manifest refraction, vector analysis, best spectacle-corrected visual acuity (BSCVA), complications and adverse reactions, subjective symptoms, and patient satisfaction. Results Six and 12 months of follow-up, respectively, were available on 143 and 117 spherical hyperopic eyes, 124 and 74 hyperopic astigmatic eyes, and 57 and 38 mixed astigmatic eyes, respectively. For spherical hyperopes at 6 and 12 months, UCVA was 20/40 or better in 93.4% and 93.9% of eyes, respectively. The manifest refraction spherical equivalent (MRSE) was within 0.50 D of intended in 65.0% and 74.1% of eyes, respectively, and within 1.00 D in 87.4% and 91.4%, respectively. Refractive stability was demonstrated in 94.2% or more of eyes between the intervals of 1 to 3 months and 3 to 6 months and in 95.3% or more of eyes to 12 months. A loss of two lines of BSCVA occurred in 3.5% and 3.4%, respectively, and no eyes lost more than two lines. For hyperopic astigmats at 6 and 12 months, UCVA was 20/40 or better in 90.9% and 93.8% of eyes, respectively. The MRSE was within 0.50 D of intended in 60.5% and 73.0% of eyes, respectively, and within 1.00 D in 88.7% and 89.2% of eyes, respectively. Refractive stability was demonstrated in 96.5% or more of eyes, respectively, between the intervals of 1 to 3 months and 3 to 6 months and 95.5% or more to 12 months. A loss of two lines of BSCVA occurred in 5.8% and 1.4% of eyes, respectively, and no eyes lost more than two lines. For mixed astigmats at 6 and 12 months, UCVA was 20/40 or better in 92.6% and 94.4% of eyes, respectively. The MRSE was within 0.50 D of intended in 64.9% and 73.7% of eyes, respectively, and within 1.00 D in 87.7% and 94.7% of eyes, respectively. Refractive stability was demonstrated in 100% of eyes between the intervals of 1 to 3 months and 3 to 6 months and in 97.0% or more to 12 months. A loss of two lines of BSCVA occurred in 1.9% and 0.0% of eyes, respectively, and no eyes lost more than two lines. Conclusions The data support safety and effectiveness of the LASIK correction of spherical hyperopia, hyperopic astigmatism, and mixed astigmatism with the LADARVision system.

In a large study by Haft et al. of 4,772 eyes, only 3 (0.06 %) eyes had incomplete flaps due to suction loss [1]. By far the most common type of suction loss during femtosecond flap creation occurs during the raster pattern, either early (Fig. 29.1) or late but before the side cut is initiated. When suction loss occurs during a mechanical microkeratome LASIK procedure, the procedure should be terminated if the instrument actually started to cut the flap. Attempting to perform a recutting of the flap is not advisable since the same plane of dissection will not be attained.

Purpose: To evaluate the visual outcomes in patients having photorefractive keratectomy (PRK) to correct residual myopia after radial keratotomy (RK). Setting: Nine refractive surgery centers in the United States and one in South Korea. Methods: This retrospective analysis comprised 38 eyes of 32 patients treated with PRK after,RK and followed for 12 months. Analysis was based on pre-RK and prePRK refraction as well as response to RK (pre-RK minus pre-PRK refractions). Results: Mean pre-RK and pre-PRK refractions were −8.11 diopters (D) ± 2.92 (SD) and −4.28 ± 2.08 D, respectively. One month after PRK, mean refraction was +0.42 ± 1.56 D and regressed to -0.95 ± 1.24 D at 12 months. At 12 months, 65% of eyes had an uncorrected visual acuity of 20/40 or worse, and 11.1 % lost 2 or more lines of best corrected acuity. Of eyes with an original error of −6.00 or less, 81.8% were within ±1.00 D of intended correction at 12 months and of those with an original error of −9.12 to −20.00 D, 50.0% ( P = .004). All eyes with residual (pre-PRK) errors of −3.00 D or less and 42.9% with a residual error of −6.12 to −9.00 D were within ±1.00 D of intended correction ( P = .07). There were no statistically significant differences in the response to PRK between eyes that had an RK response of 0 to 3.00, 3.12 to 6.00, or 6.12 to 12.00 D. Conclusion: Patients with lower original and residual myopia achieved better visual outcomes after PRK than those with higher myopia. The amount of myopic correction achieved using RK was not predictive of the amount of myopic correction using PRK.

BACKGROUND: The efficacy and predictability of photorefractive keratectomy and radial keratotomy become increasingly relevant. This retrospective study compares one surgeon's experience with photorefractive keratectomy and radial keratotomy over a 3-year period from 1990 to 1993. METHODSî Photorefractive keratectomy was performed on 103 eyes of 76 patients that met the inclusion criteria for the phase Hb, phase HI, and phototherapeutic keratectomy studies as delineated by the United States Food and Drug Administration. Radial keratotomy was performed on 117 eyes of 81 patients with up to 9.00 diopters (D) of myopia. RESULTS: In the photorefractive keratectomy group, 83% of the eyes achieved uncorrected visual acuity of at least 20/40; 37% saw 20/20; 88% had a refraction within 1.00 D of emmetropia, and 63% within 0.50 D of emmetropia. For the radial keratotomy group, 85% of the eyes achieved an uncorrected visual acuity of 20/40 or better; 27% saw 20/20; 88% had a refraction within 1.00 D of emmetropia; and 55% within 0.50 D of emmetropia. There were no serious complications, and only one single eye in each of the photorefractive keratectomy and radial keratotomy groups lost two lines or more of spectacle-corrected visual acuity. CONCLUSION: Photorefractive keratectomy and radial keratotomy are both effective procedures, and result in similar refractive outcomes for myopia of -1.00 to -9.00 D. [J Refract Surg. 1995;11:477-484.]

BACKGROUND: Treatment of corneal abrasions often involves antibiotic ointment and pressure patching. The corneal abrasions following excimer laser photorefractive keratectomy have been managed with disposable soft contact lenses and diclofenac (Voltaren) eye drops. METHODS: We report 13 patients with corneal abrasions from trauma or recurrent corneal erosions treated with application of a disposable soft contact lens and instillation of diclofenac and antibiotic eye drops. RESULTS: AU 13 patients reported significant pain relief and all abrasions healed within 3 days (most within 24 hours). Two of the recurrent erosion patients suffered subsequent spontaneous abrasions and one of the traumatic abrasion patients developed a possible infectious keratitis which cleared without visual loss. CONCLUSIONS: In this small series, the combination of a disposable soft contact lens and the instillation of diclofenac drops provided significant pain relief while the abrasion healed and allowed the patients to function with binocular vision. This treatment regimen offers an alternative to pressure patching in the treatment of corneal abrasions. [J Refract Corneal Surg. 1994;10:640-646.] RESUME INTRODUCTION: Le traitement des abrasions cornéennes utilise un collyre antibiotique et un cache l'oeil à pression. Les abrasions cornéennes après la kératectomie photo-réfractive ont été traité avec des lentilles de contacts flexibles et les gouttes du diclofenac. METHODES: Nous faisons un rapport sur 13 patients affectés d'abrasions cornéennes suivant le traumatisme ou des érosions répétées traités d'une lentille de contact flexible et des gouttes d'antibiotique et diclofenac. RESULTATS: Tous les patients ont noté un soulagement sifnificatif de douleur et toutes les abrasions furent guéries apreès 3 jours (la plupart apreès 24 heures). Deux patients avec des érosions répétés ont éprouvé des érosions spontanées et un des patients traumatisé à l'avance a développé une kératite peut-être infectieuse ce qui guérit sans perte de vision. CONCLUSIONS: Dans nos petites series, l'ensemble d'une lentille de contact flexible et 'instillation de gouttes du diclofenac ont donné un soulagement de douleur significatif pendant la guérison de l'abrasion et ont gardé la fonctionnement avec vision binoculaire. Cette méthode nous offre un alternatif au cache l'oeil pour le traitement des abrasions cornéennes. (Translated by Rob Mack, MD, Kansas City, Mo.) SOMMARIO PREMESSA: ? trattamento standard delle abrasioni corneali include pomate antibiotiche e bendaggio. Le abrasioni dopo cheratectomie fotorefrattiva sono state tratte con lenti a contatto morbide monouso e diclofenac in gocce. METODI: Riportiamo 13 pazienti con abrasione corneale dopo traumi o erosioni corneali recidivanti trattati con l'applicazione di una lente a contatto morbida monouso e l'instillazione di diclofenac e gocce di antibiotic. RISULTATI: Tutti 13 pazienti hanno riferito una significativa diminuzione del dolore e tutte le abrasioni si sono risolte entro 3 giorni (la maggior parte entro 24 ore). Due dei pazienti con erosioni recidivanti hanno successivamente riportato una abrasione spontanea ed uno dei pazienti con erosione traumatica ha sviluppato una cheratite presumibilmente infettiva che si è risolta senza calo visivo. CONCLUSIONI: In questa piccola serie, la combinazione di una lente a contatto morbida monouso e l'instiliazione di gocce di diclofenac ha determinato una significativa diminuzione del dolore mentre l'abrasione è guarita, ed ha permesso al paziente la visione binoculare. Questo trattamento rappresenta una alternativa al bendaggio nel trattamento delle abrasioni corneali. (Translated by Francesco Carones, MD, Milan, Italy)

BACKGROUND: Excimer laser (VISX) photorefractive keratectomy was performed using nitrogen flowing through the ocular fixation ring. It was felt that eliminating nitrogen flow may provide faster early visual rehabilitation. METHODS: Two groups of 50 consecutive eyes underwent photorefractive keratectomy with (N 2 flow) and without (no N 2 flow) nitrogen flow, and were evaluated at 1 month postoperatively. RESULTS: There were more under- or overcorrections exceeding 1.00 diopter (D) in the N 2 flow than in the no N 2 flow groups. Eighteen eyes in the N 2 flow and 11 in no N 2 flow groups saw 20/50 or less, without correction. Fourteen eyes in the N 2 flow and nine eyes in the no N 2 flow groups lost two or more lines of best spectacle-corrected visual acuity. Four eyes in the N 2 flow and none in the no N 2 flow groups increased more than 1.00 D of astigmatism. CONCLUSION: The elimination of nitrogen flow in photorefractive keratectomy performed with the VISX laser appears to improve visual results in the early postoperative period. [J Refract Corneal Surg. 1994;10:321-326.] RÉSUMÉ INTRODUCTION: La kératectomie photo-refractive au laser excimer (VISX) fut réalisée avec et sans la projection de nitrogène par l'anneau de fixation de l'oeil a fin de préciser l'effet du nitrogène sur le début de la récupération visuelle. MÉTHODES: Deux groupes de 50 yeux consécutifs suites ont subi la kératectomie photo-réfractive avec et sans la projection de nitrogène, et ont été évalués un mois après la chirurgie. RÉSULTATS: On a constaté plus d'yeux sur- et sous-corrigés d'au moins 1,0 dioptrie dans le groupe traité avec le coulement du nitrogène que dans l'autre groupe. Dix-huit yeux traités avec nitrogène et 11 yeux traités sans nitrogène ont di montre une acuité visuelle égale à ou inférieure à 20/50. Quatorze yeux traités avec nitrogène et 9 yeux traités sans nitrogène ont perdu au moins deux lignes de meilleure acuité corrigée sur l'échelle de Snellen. Quatre yeux dans le groupe traité avec le nitrogène et aucun dex yeux dans l'autre groupe ont éprouvé une augmentation de l'astigmatisme d'au moins, 1,0 dioptrie. CONCLUSION: L'élimination du coulement du nitrogène dans la kératectomie photorefractive au laser excimer de VISX pourrait améliorer les résultats visuels dans le début de la période postopératoire. (Translated by Rob Mack, MD, Iowa City, Iowa.) SOMMARIO PREMESSA: La cheratectomia fotore fratti va (PRK) mediante laser ad Eccimeri (VISX) e' stata effettuata utilizzando un flusso di nitrogeno attraverso l'anello di fissazione oculare. Si riteneva che eliminando tale flusso di nitrogeno si potesse ottenere un recupero funzionale piu' rapido.

BACKGROUND: Excimer laser photorefractive keratectomy tor the correction of myopia is presently under investigation in the United States by the Food and Drug Administration (FDA). The Phase 1 1 -B FDA study is being conducted on 75 normally sighted myopic eyes utilizing three currently available excimer lasers. This report presents the 1 -year results on 12 myopic eyes treated with the VISX excimer laser system at the Ellis Eye Center at Cedars-Sinai Medical Center in Los Angeles under the Phase H-B FDA protocol. METHODS: Twelve eyes of 12 patients with myopia between - 1.75 and -5.00 diopters underwent 193 nm argon/fluoride excimer laser photorefractive keratectomy. The epithelium was mechanically removed, and fixation was accomplished with a suction ring which provided nitrogen flow across the corneal surface. The computer controlled corneal ablations were 5.00 mm in diameter and were accomplished with an iris diaphragm closing from large to small. RESULTS: The preoperative spherical equivalent myopia was -3.50 D (SD = 1.02) and the postoperative myopia was -0.25 (SD = 0.48). Eleven of the 12 patients achieved an uncorrected visual acuity of 20/30 or better and were corrected to within ±0.50 D of emmetropia. All corneas demonstrated a mild reticular subepithelial haze which was barely visible at 1 year. There were no visionthreatening complications and none of the eyes experienced a loss of best corrected visual acuity. CONCLUSIONS: In this small trial, the excimer laser appears to be capable of accurately changing the refractive power of the cornea for the correction of myopia with minimal side effects. Only when larger numbers of patients undergo the procedure will we be able to determine the safety and efficacy of photorefractive keratectomy as a refractive surgical procedure Refract Corneal Surg 1992;8:269-273.) RÉSUMÉ INTRODUCTION. La kératectomie refractive lamellaire au laser excimer pour Ia correction de la myopie est maintenant un sujet d'investigation chez la Food and Drug Administration (FDA) aux Etats-Unis. On est en train de conduire la phase H-B de l'étude clinique chez 75 yeux myopes avec une potenìiaìiìé de vision de 10/10° en utilisant trois lasers maintenant disponibles. Cette communication présente les résultats de 12 yeux myopes traités aux VISX système de laser excimer chez The Ellis Eye Center au Cedars-Sinai Medical Center à Los Angefes, selon le protocole de la phase M-B de la FDA, et suivis depuis une année.

In the Prospective Evaluation of Radial Keratotomy (PERK) Study, 793 eyes of 435 patients with 2 to 8 diopters (D) of myopia received a standardized surgery consisting of 8 incisions with a diamond-bladed knife set at 100% of the thinnest paracentral ultrasonic corneal thickness measurement and a diameter of the clear zone of 3.0 to 4.5 mm; 97 eyes (12%) received an additional 8 incisions. There were 757 eyes (95%) followed for 3 to 6.3 years. After surgery, uncorrected visual acuity was 20/40 or better in 88% of eyes

Two patients, a 4 1 -year-old female diabetic and a 37-year-old male, were undercorrected after radial keratotomy (spherical equivalents of -3.25 diopters in each eye). Because they were unable to wear a coniaci lens and had uncorrected visual acuities of 20/400 and 20/100, respectively, they elected to undergo excimer laser photorefractive keratectomy to reduce the myopia by 3.00 D and 2.75 D, respectively. Three months postoperatively, both patients were within 0.50 D of emmetropia. Videokeratography demonstrated a fairly uniform zone of central flattening. The previous radial keratotomy surgery and the diabetes (in one patient) did not appear to complicate the surgery. Excimer laser photorefractive keratectomy appears to hold promise as a means of correcting eyes left undercorrected by radial keratotomy. (Refract Corneal Surg 1991;7:146-150.)

This retrospective study reports the results of radial keratotomy surgery on 225 eyes of 135 patients by one surgeon. Fifty-one percent of the eyes had four incisions and 45% had eight as the initial procedure. Fifteen percent of the eyes repeated surgery. The mean preoperative spherical equivalent refraction was -5.10 diopters (SD 1.90, range 1.20 to 11.60 D) and at 3 months to 1 year, the mean was -0.60 D (SD 1.00, range -4.80 to +3.40 D). For the entire series, 69% of the eyes achieved an uncorrected visual acuity of 20/40 or better, 73% were corrected to within ±1.00 D of emmetropia, and 3% were overcorrected by more than +1.00 D. For eyes with low preoperative myopia (-3.00 D and less), 100% achieved an uncorrected visual acuity of 20/40 or better, 97% were corrected to within ±1.00 D of emmetropia, and 3% were overcorrected by more than +1.00 D. For eyes with moderate myopia (-3.1 to -5.9 D), 73% achieved an uncorrected visual acuity of 20/40 or better, 81% were corrected to within ±1.00 D of emmetropia, and 3% were overcorrected by more than +1.00 D. For eyes with higher preoperative myopia ( -6.0 to -11.60 D), 47% achieved an uncorrected visual acuity of 20/40 or better, 45% were corrected to within ±1.00 D of emmetropia and 3% were overcorrected by more than +1.00 D. One hundred eyes with a follow-up of 2 years or greater were studied for stability; 77% changed by less than 1.00 D from the 1 year value; 17% changed by 1.00 D or more in the hyperopic direction; 6% changed by 1.00 D or more in the myopic direction. There were no vision threatening complications and only one eye had a postoperative best spectacle corrected visual acuity of less than 20/40. [Refractive and Corneal Surgery 1991;7:12-22.]

Four radial linear excisions were created by an argon fluoride (193 nm) excimer laser in the edematous cornea of a blind eye of a diabetic human patient. Partial thickness corneal trephinations were performed at 3, 7, and 18 months after surgery for histopathologic examination. At 3 months, a wide gap in Bowman's layer permitted extension of an epithelial plug to a depth of 0.35 mm; at 7 and 18 months, the depth of the epithelial plug was decreased to 0.29 mm and 0.01 mm, respectively. With wound healing, excision width decreased and the two cut ends of Bowman's layer were almost reapposed by 18 months, suggesting wound contraction. Linear excisions with the excimer laser appear to be wider than incisions made with a diamond blade, but the pattern of wound maturation appears to be similar. [Refractive and Corneal Surgery 1990;6:188-192.]

Purpose of review The role of scotopic pupil size as a factor in predicting night vision complaints is controversial. This review summarizes reports in the literature, some that have found and some that have failed to find a correlation with scotopic pupil size and night vision complaints. Recent findings Pupil-measuring devices are discussed along with informed consent issues and reports showing that wavefront aberrations increase with increasing pupil size. A new objective measuring device (Larson) showed a correlation with postoperative starbursts and pupil size and a decrease in starbursts with wavefront-guided treatments compared with conventional excimer laser treatments. Cortical adaptation allows many patients to adapt to their new night vision. Treatment options for those who remain symptomatic include drops to reduce pupil size and wavefront-guided retreatments. Summary Reports in the literature are conflicting, and refractive surgeons would be wise to inform their patients that large scotopic pupil size is a potential risk factor for night vision complaints. By doing this they will follow the recommendations in recent patient information brochures of both VISX (Santa Clara, California) and Alcon (Orlando, Florida) and on the United States Food and Drug Administration web site.

An aircraft pilot had bilateral photorefractive keratectomy (PRK) with intentional undercorrection in the nondominant eye for best uncorrected far and near visual acuity (monovision). After PRK, the patient was able to pilot an aircraft with no deleterious effects directly related to surgery. Evaluation of similar cases and further study will allow consensus on whether PRK is appropriate in these patients.

PURPOSE: To describe the off-label use of the Alcon LADARVision System for CustomCornea (LADARWave and LADARVision4000) in two patients, one for retreatment after laser in situ keratomileusis (LASIK) and one for retreatment after photorefractive keratectomy (PRK). METHODS AND RESULTS: Both patients were unhappy with the quality of their vision after initial refractive surgery. The first patient initially had LASIK to correct -4.75 D of myopia in each eye, and then had retreatment with CustomCornea. Before retreatment, manifest refraction was OD 0.50 -0.50 ? 180° (20/25 uncorrected) and OS -0.50 -0.75 ? 180° (20/40 uncorrected). Two months after retreatment with CustomCornea, his uncorrected visual acuity OD was 20/15, and 1 month after retreatment in his left eye, uncorrected visual acuity was 20/15. The second patient had PRK OD, with a postoperative uncorrected visual acuity of 20/25 and cycloplegic refraction of +1.00 -0.75 x 84°. After CustomCornea retreatment, his 3.5-month postoperative uncorrected visual acuity was 20/15 and manifest refraction was +0.50 -0.50 x 180°. CONCLUSION: The Alcon LADARVision System for CustomCornea was used effectively to retreat both a myopic LASIK and myopic PRK patient, primarily for subjective quality of night vision complaints. [J Refract Surg 2003;19:S697-S702]

Purpose To determine whether refractive complications can be prevented by applying the currently most accurate method of intraocular lens (IOL) power calculation in the post-radial keratotomy (RK) patient. Setting Department of Ophthalmology, University of California, Davis, Sacramento, and American Eye Institute, Cedars Sinai Medical Center, Los Angeles, California, USA. Methods Twenty-four eyes having cataract surgery after RK were studied retrospectively for the final postcataract refraction and for the target refraction used in selecting the IOL. Nine of the eyes were further studied for the keratometry (K) values obtained with different methods and for the theoretical postoperative refraction with an IOL aiming for plano or −1.50 diopters (D) based on the known flatter calculated K, axial length, power of the implanted IOL, and refraction after cataract surgery. Results Implantation of an IOL aiming for plano in the 24 post-RK eyes would have resulted in a hyperopic refraction in 83.4% cases. The choice of an IOL targeted at myopia reduced the frequency of hyperopia to 42.0% (24 cases). Selection of an IOL calculated with a flatter calculated K and aiming for plano decreased the frequency of hyperopia to 44.4%; however, aiming for −1.50 D still resulted in hyperopia in 44.4% of eyes (9 cases). Conclusions Unintentional hyperopia can be significantly decreased but not eliminated as a complication of post-RK cataract surgery. The accuracy of the IOL power determination can be improved if myopia is targeted as the postcataract surgery refractive error and the flatter calculated K is used in the IOL determination.

A study was undertaken to assess whether results of laser vision correction with the LADARVISION 193-nm excimer laser (Alcon-Autonomous technologies) can be improved with the use of wavefront analysis generated by a proprietary system including a Hartman-Schack sensor and expressed using Zernicke polynomials. A total of 82 eyes underwent LASIK in several centers with an improved algorithm, using the CustomCornea system. A subgroup of 48 eyes of 24 patients was randomized so that one eye undergoes conventional treatment and one eye undergoes treatment based on wavefront analysis. Treatment parameters were equal for each type of refractive error. 83% of all eyes had uncorrected vision of 20/20 or better and 95% were 20/25 or better. In all groups, uncorrected visual acuities did not improve significantly in eyes treated with wavefront analysis compared to conventional treatments. Higher order aberrations were consistently better corrected in eyes undergoing treatment based on wavefront analysis for LASIK at 6 months postop. In addition, the number of eyes with reduced RMS was significantly higher in the subset of eyes treated with a wavefront algorithm (38% vs. 5%). Wavefront technology may improve the outcomes of laser vision correction with the LADARVISION excimer laser. Further refinements of the technology and clinical trials will contribute to this goal.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A study was undertaken to assess whether results of excimer laser vision correction with the LADARVision 193nm excimer laser (Alcon Summit Autonomous) can be improved with the use of wavefront analysis generated by a proprietary system utilizing a Hartman-Schack sensor and expressed using Zemicke polynomials. Three patient groups were studied: Group 1 included 23 patients undergoing LASIK, Group 2 included 13 patients undergoing PRK (6 months follow-up available), and Group 3 (23 patients) undergoing LASIK with 1 week follow-up. Both eyes of each patient were randomized so that one eye underwent conventional treatment and one eye underwent treatment based on wavefront analysis. Treatment parameters were equal for each type of refractive error. In all groups, uncorrected visual acuities did not improve significantly in eyes treated with wavefront analysis compared to conventional treatments. However, higher order aberrations were consistently better corrected in eyes undergoing treatment based on wavefront analysis for LASIK (p=0.05) and for PRK (p=0.02) at 6 months postop. Wavefront technology may improve the outcomes of laser vision correction with the LADARVision excimer laser system. Further refinements of the technology and execution of clinical trials will contribute to this goal.

A study was undertaken to assess the safety and efficacy of LASIK with the LADARVision laser by Autonomous Technologies, (Orlando, FL). The study included four subsets: Spherical myopia -- up to -11.00D, spherical hyperopia -- up to +6.00D. Both myopic and hyperopic astigmatism could be corrected, up to 6.00D of astigmatism. A total of 105 patients participated. Sixty-six patients were myopic and 39 were hyperopic. The mean (+/- SD) age was 42.8 +/- 9.3 years for myopia and 53.2 +/- 9.9 years for hyperopia. At 3 months postop. Sixty-one myopic eyes were available for evaluation. Uncorrected visual acuity was 20/20 in 70% of eyes and 20/40 in 92.9% of all eyes. The refractive outcome was within +/- 0.50D in 73.8% of eyes and within +/- 1.00D in 96.7 of eyes. Thirty-eight hyperopic eyes were available. Uncorrected visual acuity was 20/20 in 42.1% of eyes and 20/40 in 88% of all eyes. The refractive outcome was within +/- 0.50D in 57.9% of eyes and within +/- 1.00D in 86.8% of eyes. Complications were not sight threatening and were discussed in detail. Lasik with the LADARVision laser appears to be safe and effective.

Objective To assess the safety and effectiveness of the Autonomous Technologies Corporation LADARVision excimer laser system for photorefractive keratectomy correction of myopia and astigmatism. Design A multicenter, prospective, noncomparative case series. Participants The cohort consisted of 467 eyes corrected for spherical myopia and 211 eyes corrected for myopia with astigmatism. Intervention Treatments were performed at six sites in the United States using a 6-mm ablation zone for spherical myopes and a 5.5-mm zone with a 1.0-mm blend for astigmats. Main outcome measures Visual acuity, subjective refraction, corneal haze, intraocular pressure, complications, adverse reactions, patient satisfaction, and corneal endothelial changes. Results Twelve-month follow-up was available on 414 spherical eyes and 175 astigmatic eyes. The results for spherical eyes with correction between −1 and −5.99 diopters (D) were: uncorrected visual acuity (UCVA) of 20/40 or better achieved by 98.1%, 20/20 or better by 72%, 1.8% lost 2 lines and 0.3% lost greater than 2 lines of best spectacle-corrected visual acuity (BSCVA); 76.4% were within 0.50 D of the target correction and 94.4% were within 1.00 D. The results for myopia with astigmatism with spherical equivalent correction between −1 and −5.99 D were: UCVA of 20/40 or better in 97.4%, 20/20 or better in 61.7%, 2.5% lost 2 lines and no eyes lost greater than 2 lines BSCVA; 73.9% were within 0.50 D of the target correction and 95% were within 1.00 D. For spherical myopes combined with myopic astigmats corrected for 6 to 10 D, results were: UCVA of 20/40 or better in 93.4%, 20/20 or better in 61.2%, 2.3% lost 2 lines and no eyes lost greater than 2 lines of BSCVA; 67.2% were within 0.50 D of the desired correction and 87.8% were within 1.00 D. Refractive stability was achieved between 3 and 6 months for the spherical and astigmatic groups. No eyes had corneal haze graded as moderate or greater, and there was no significant decrease in endothelial cell density. Conclusions Patients treated for 1 to 10 D of spherical equivalent myopia, with or without astigmatism, showed early refractive stability, excellent UCVA, no significant loss of BSCVA, no loss of endothelial cell density, and very low levels of corneal haze to 12 months after surgery.

The preliminary results of hyperopic photorefractive keratectomy (HPRK) performed with the VISX-Star excimer laser on 40 eyes of 25 patients are presented. 28 of 40 eyes had vision of 20/40 at 6 months and 22 of 25 eyes saw 20/40 12 months postoperatively. Eleven of 40 patients were over corrected 1.00 D at 6 months and no patients were overcorrected with the same amount at 12 months postop. At six months, no undercorrections of 1.00 D were observed and 3 of 25 eyes were undercorrected by 1.00 D at 12 months postop. At 6 months postop, 35 of 40 eyes saw for near J5 or better, and 20 of 25 saw J5 at 12 months postop. Complications included: induced astigmatism of 1.00 D (6 of 40 eyes at 6 months and 3 of 25 eyes at 12 months), and loss of two lines of best corrected vision (4 of 40 at 6 month,s and 2 of 25 at 12 months). HPRK appears to be safe and effective in correcting hyperopia of up to 4.00 D in the short to medium term.

Preliminary results of the correction of myopia up to -7.00 D by tracked photorefractive keratectomy (T-PRK) with a scanning and tracking excimer laser by Autonomous Technologies are discussed. 41 eyes participated (20 males). 28 eyes were evaluated one month postop. At epithelization day mean uncorrected vision was 20/45.3. At one month postop, 92.8 of eyes were 20/40 and 46.4% were 20/20. No eye was worse than 20/50. 75% of eyes were within +/- 0.5 D of emmetropia and 82% were within +/- 1.00 D of emmetropia. Eyes corrected for monovision were included. One eye lost 3 lines of best corrected vision, and had more than 1.00 D induced astigmatism due to a central corneal ulcer. Additional complications included symptomatic recurrent corneal erosions which were controlled with topical hypertonic saline. T-PRK appears to allow effective correction of low to moderate myopia. Further study will establish safety and efficacy of the procedure.

Multivariable regression analysis was used to evaluate the combined effects of some preoperative and operative variables on the change of refraction following excimer laser photorefractive keratectomy for myopia (PRK). This analysis was performed on 152 eyes (at 6 months postoperatively) and 156 eyes (at 12 months postoperatively). The following variables were considered: intended refractive correction, patient age, treatment zone, central corneal thickness, average corneal curvature, and intraocular pressure. At 6 months after surgery, the cumulative R2 was 0.43 with 0.38 attributed to the intended correction and 0.06 attributed to the preoperative corneal curvature. At 12 months, the cumulative R2 was 0.37 where 0.33 was attributed to the intended correction, 0.02 to the preoperative corneal curvature, and 0.01 to both preoperative corneal thickness and to the patient age. Further model augmentation is necessary to account for the remaining variability and the behavior of the residuals.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Some technical factors relating to the use of the VISX model 20/20 excimer laser for photorefractive keratectomy will be discussed and the way they affect the final optical correction will be demonstrated, as follows: (1) Discontinuation of nitrogen flow: improved corneal haze but induced a mean undercorrection of 0.8 D, 18 months postoperatively. (2) Discontinuation of the use of the fixation ring did not affect centration in a statistically significant fashion. (3) Enlargement of the optical from 5.0 mm to 6.0 mm zone did not affect the refractive outcome. Visual acuity was improved in eyes which had PRK done with a 6.0 mm optical zone.

Purpose: This report summarizes the authors' 3-year experience with excimer laser photorefractive keratectomy on 240 eyes of 161 patients. Methods: With constant laser emission parameters, nitrogen flow across the cornea was used on 79 eyes, whereas 161 eyes had no nitrogen flow. Of the 240 eyes, 74 were operated on without suction ring fixation. Postoperative pain management included patching and oral analgesics in 77 eyes and the use of topical diclofenac or ketorolac and a therapeutic soft contact lens in 163 eyes. Follow-up ranged from 1 month (206 eyes) to 36 months (10 eyes). Results: At 3 months, 88% (144 eyes) had uncorrected visual acuity of 20/40 or better; 86% (151 eyes) had corrected visual acuity to within ±1 diopter of intended correction, and 10% (17 eyes) lost two or more lines of best-corrected visual acuity. At 12 months, 89% (122 eyes) achieved uncorrected visual acuity of 20/40 or better, 79% (115 eyes) had corrected visual acuity to within ±1 diopter of intended correction, and 4% (6 eyes) lost two or more lines of best-corrected visual acuity. At 24 months, 92% (44 of 48 eyes) had uncorrected visual acuity of 20/40 or better, 86% (44 of 51 eyes) had corrected visual acuity to within ±1 diopter of intended correction, and 5% (2 eyes) lost two or more lines of best-corrected visual acuity. At 36 months, 90% (9 eyes) achieved an uncorrected visual acuity of 20/40 or better, 90% (9 eyes) had corrected visual acuity to within ±1 diopter of intended correction, and no eyes lost two or more lines of best-corrected visual acuity. Conclusions: The results obtained with one procedure are within accepted stan dards of accuracy for refractive surgery, and there is the potential for refinement of the final optical correction. Complication rates are low and are not vision threatening. They included increased intraocular pressure, epithelial "map dot" changes, and recurrent corneal erosion syndrome, "central islands", and others. Photorefractive keratectomy appears to be a safe procedure over the short and medium term.

This report summarizes the authors' 3-year experience with excimer laser photorefractive keratectomy (PRK) on 240 eyes of 161 patients. With constant laser emission parameters, nitrogen (N2) flow across the cornea was used on 79 eyes while 161 eyes had no N2 flow. 74 eyes were operated on without fixation with a suction ring. Postoperative pain management included patching and oral analgesics in 77 eyes and the use of topical Diclofenac or Ketorolac, and a therapeutic soft contact lens in 163 eyes. Follow up ranged from 1 month (206 eyes) to 36 months (10 eyes).© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Our two year experience with excimer laser photorefractive keratectomy for the correction of myopia on 160 eyes of 128 patients is described. All eyes were treated with a VISX Twenty- Twenty excimer laser, with the following parameters: radiant exposure 160 mJ/cm2, frequency 5 Hz, ablation zone diameter 5.0 to 5.5 mm, and stromal ablation rate 0.18 to 0.33 (mu) /pulse. A suction fixation ring was used in all cases either with nitrogen flow (79 eyes) or without nitrogen flow (81 eyes) across the cornea. Follow-up ranged from one month (152 eyes) to 24 months (12 eyes). The results are stable between 3 and 24 months with less than 0.25 D change in the mean postoperative spherical equivalents. In eyes with a follow-up of 6 to 24 months, 77% to 100% were 20/40 or better uncorrected, and 84% to 92% were corrected to within +/- 1 D of emmetropia. Further follow-up is needed to assess the long term safety and efficacy of the procedure.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Purpose: This report summarizes the authors' 2-year experience with excimer laser photorefractive keratectomy (PRK) on 160 eyes of 128 patients. Methods: All eyes were treated with an excimer laser: fluence, 160 mJ/cm 2 ; frequency, 5 Hz; ablation zone diameter, 5.0 to 5.5 mm; and depth per pulse, 0.21 to 0.27 μm. A suction fixation ring was used in all eyes either with nitrogen flow (79 eyes) or without nitrogen flow (81 eyes) across the cornea. Follow-up ranged from 1 month (152 eyes) to 24 months (12 eyes). Results: At 3 months, 82% (139) of eyes achieved an uncorrected visual acuity of 20/40 or better; 83% were corrected to within ±1 diopter (D) of intended correction and 30% lost one line of best-corrected visual acuity. At 6 months, 88% (124) of eyes achieved an uncorrected visual acuity of 20/40 or better; 84% were corrected to within ±1 D of intended correction and 15% lost one line of best-corrected visual acuity. At 12 months, 91% (71) of eyes achieved an uncorrected visual acuity of 20/40 or better; 84% were corrected to within ±1 D of intended correction and 17% lost one line of best-corrected visual acuity. At 24 months, 100% (12) of eyes achieved an uncorrected visual acuity of 20/40 or better; 91.6% were within ±1 D of intended correction and 0% lost one line of best-corrected visual acuity. Conclusions: In eyes with a follow-up of 6 to 24 months, 77% to 100% achieved an uncorrected visual acuity of 20/40 or better and 84% to 92% were corrected to within ±1 D of the intended correction. The authors conclude that excimer laser PRK appears to be a safe procedure capable of correcting the eyes of patients with low to moderate myopia with approximately the same degree of accuracy as radial keratotomy.

Sixty-two eyes underwent excimer laser photorefractive keratectomy (PRK) for the correction of myopia at Cedars-Sinai-Medical-Center. The first group of 12 patients are presented with follow up data of ten months postoperatively. The second group of 50 patients are presented with follow up data of three months postoperatively. An in-depth comparison of pre and postoperative refractive data is presented. Comparisons between pre and postoperative corrected and uncorrected Snellen visual acuities are provided in order to asses the functional visual result of the procedure.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

BACKGROUND: During excimer laser photorefractive keratectomy, central Bowman's layer and superficial stroma are removed. A potential disadvantage of this technique is whether proper epithelization of the cornea will occur in the event of a corneal abrasion. A potential advantage of photorefractive keratectomy over radial keratotomy in the event of blunt trauma is the presumably sound structural integrity of the cornea following superficial removal of stroma in photorefractive keratectomy compared to the weakened cornea following deep incisions in radial keratotomy. METHODS: We report two patients who sustained corneal abrasions from blunt trauma to the eye and orbit following photorefractive keratectomyone following a fist injury and the other following a karate kick. RESULTS: In both patients, the corneal abrasions healed without incident and without recurrent erosions and both corneas remained intact. CONCLUSIONS: Corneal abrasion following trauma in two patients who has undergone photorefractive keratectomy healed as expected in a normal cornea. Although it is uncertain whether the trauma in these patients would have been sufficient to rupture radial keratotomy incisions, as would be expected from a superficial photorefractive keratectomy, the corneas remained intact following blunt trauma. [Refract Corneal Surg. 1994;10:36-37.)

Five radial keratotomy predictive software programs are reviewed. The review consists of a brief description of each program and a comparative analysis of four hypothetical radial keratotomy patients with preoperative myopia of: - 2.50, - 5.00, - 7.50 and - 10.00. Significant differences in the recommended surgery for these patients is apparent. A sample printout of each program's predictions on the - 7.50 D patient is included. The true value of these programs will become apparent when independent surgeons report a prospective analysis detailing the accuracy of these predictions.

The Prospective Evaluation of Radial Keratotomy (PERK) study is a nine-center, self-controlled clinical trial of a standardized technique of radial keratotomy in 435 patients who had physiologic myopia with a preoperative refraction between -2.00 and -8.00 diopters. The surgical technique consisted of eight incisions using a diamond micrometer knife with blade length determined by intraoperative ultrasonic pachymetry and the diameter of central clear zone determined by preoperative refraction. At one year after surgery, myopia was reduced in all eyes; 60% were within +/- 1.00 diopter of emmetropia; 30% were undercorrected and 10% were overcorrected by more than 1.00 diopter (range of refraction, -4.25 to +3.38 D). Uncorrected visual acuity was 20/40 or better in 78% of eyes. The operation was most effective in eyes with a refraction between -2.00 and -4.25 diopters. Thirteen percent of patients lost one or two Snellen lines of best corrected visual acuity. However, all but three eyes could be corrected to 20/20. Ten percent of patients increased astigmatism more than 1.00 diopter. Disabling glare was not detected with a clinical glare tester, but three patients reduced their driving at night because of glare. Between six months and one year, the refraction changed by greater than 0.50 diopters in 19% of eyes.

SUMMARY Two studies were carried out to determine and compare the effects of several sources of variation on the measurement of corneal thickness using the standard optical pachymeter and three ultrasonic pachymeters. Sources of variation included: intra- and inter-session variation, inter-observer variation, left/right eye variation, and variations due to alternate settings of ultrasonic sound frequencies. It was found that the optical pachymeter had a) two to three times as much intra-session variation as that of the ultrasound pachymeters, b) significant inter-observer variation (P = 0.015), and c) significant differences between left and right eye thickness determinations (P < 0.005). On the other hand, ultrasonic pachymeters demonstrated a) high reproducibility, b) no inter-observer variation, and c) no left/right eye variation. These results have implications for the use of pachymetry in measuring corneal thickness for radial keratotomy and other refractive surgery.

Six recent reports of the results of Radial Keratotomy are summarized. In order to improve these results, the percentage of under- and overcorrected patients must be reduced. Hopefully, this can be accomplished by more careful patient selection and improved surgical plans aided by the various radial keratotomy predictive software programs that are now available. Pharmacologic manipulation of corneal wound healing and improvements in instrumentation should also be helpful.

Radial keratotomy with the Meditec excimer laser was performed on the blind eyes of three human volunteers. Eight radial incisions at approximately 50% to 60% of corneal thickness with a 5.0 mm optical zone resulted in 1 to 2 diopters of corneal flattening, Clinically the incisions appeared to heal well, but they seem more translucent than standard RK incisions performed with a diamond knife, Although the technique appears to be promising, further investigations are needed to quantitate the procedure and to study the wound healing of the excimer incisions.

Results of four- and eight-single-pass incision radial keratotomy for high myopia (-6.00 to -11.63 diopters) are reported in 50 eyes. The mean preoperative spherical equivalent refractive error was - 7.06 diopters (D) and the mean postoperative spherical equivalent was -1.02 D. Fifty percent of the eyes were corrected to within ± 1 D of emmetropia and 38% achieved an uncorrected visual acuity of 20/40 or better. The mean myopia reduction by age groups was as follows: 20 to 29 = 5.5 D; 30 to 39 = 6.1D; 40 to 49 = 6.5 D; over 50 = 7.5 D.

The first 112 consecutive eyes (75 patients) to undergo four-incision radial keratotomy (RK) performed by four surgeons were evaluated retrospectively. The preoperative myopia (spherical equivalent) ranged from −1.12 to −7.00 D (95% between −1.12 and −4.25 D). The preoperative uncorrected visual acuity was 20/100 or worse in 95% of the eyes. A six-month follow-up was achieved in 95% of the eyes and 45% were followed over one year. Following four incision RK, 79% of the eyes achieved 20/40 or better vision and 82% were corrected to within 1 D of emmetropia. Following repeat RK in 15 eyes (13%), 82% had uncorrected visual acuity of 20/40 or better, and 90% were corrected to within 1 D of emmetropia. Only 3.5% of the eyes were overcorrected by more than 1 D and only one eye had induced astigmatism greater than 1 D. For eyes with preoperative myopia up to −4.25 D over 90% achieved uncorrected visual acuity of 20/40 or better and were within 1 D of emmetropia following primary four incision RK and a second four incisions in 13 eyes (12%). Only 3.5% of the eyes in this group were overcorrected by more than 1 D. There were no serious complications.

Radial keratotomy was performed on six stumptail monkey eyes (Macaca speciosa) and 22 owl monkey eyes (Aotus trivirgotus). Changes in keratometry, specular microscopy, and tonometry have been studied postoperatively for three to six months. Sixteen radial incisions in stumptail monkey eyes resulted in a significant mean corneal flattening of 2.75 diopters (P less than 0.005). This effect was stable with a mean 2.50 diopters flattening remaining six months after surgery. Sixteen radial incisions in ten owl monkey eyes resulted in a much greater short-term effect, with a mean 10.50 diopters of flattening present at two weeks postoperatively. This flattening deteriorated over the observation period, and no significant effect was noted three months after surgery. A comparison of 8 vs 16 incisions on owl monkey eyes demonstrated that these two procedures are equally effective in initially flattening the cornea. Complications and side effects encountered included perforations, irregular astigmatism, corneal neovascularization, transitory increase in pachometry, and decrease in central corneal endothelial cell density in isolated cases.

Preoperative and postoperative corneascope photographs of 368 myopic patients undergoing radial keratotomy in the Prospective Evaluation of Radial Keratotomy (PERK) study were optically scanned and digitized. A high-resolution scanning system was developed in order to quantify the preoperative and postoperative corneal shape accurately. Careful analysis of the 72 data points in the nine representative rings demonstrated that corneal topography is best represented by radius of curvature from the center to the periphery. The normal myopic cornea flattens approximately +0.28 mm from the center to the periphery, demonstrating the cornea's aspheric nature. More highly myopic patients in the PERK population (-4.50 to -8.00 diopters [D]) demonstrated corneas that are 0.08 to 0.10 mm steeper than the less myopic population (-2.00 to -3.12 D). Optical zone, patient age, and gender are all correlated to changes in corneal topography after radial keratotomy. In more myopic populations, men have corneas which are flatter than those of women by 0.09 to 0.11 mm in all rings represented on corneoscopy. Highly myopic males also experience more corneal flattening after 3.0-mm optical zone radial keratotomy. Regardless of the optical zone used in radial keratotomy, the resulting corneal topography flattens in all rings. However, the ratio of millimeters of radius of curvature change to diopters of correction is consistent for each ring. The dioptric change observed after radial keratotomy corresponds closely with the millimeters of flattening at the respective rings being examined. The central rings flatten 0.166-mm radius of curvature per diopter of refractive alteration obtained. The largest degree of corneal flattening occurs centrally, 0.72 mm, in the more highly myopic patients who underwent 3-mm optical zone radial keratotomy. The use of smaller optical zones in radial keratotomy produces larger changes in the radius of curvature and, consequently, in the amount of refraction than when larger optical zones are used. When compared with younger patients, older patients with 3.0, 3.5, and 4.0 optical zone radial keratotomies experience more central and peripheral corneal flattening. This study of the corneal topography of the myopic population demonstrates that the refractive change resulting from radial keratotomy is related to alterations in corneal topography. The use of similar modifications of the corneal surface may be effective for newer refractive surgical procedures.

• The effects of optical clear zone size and incision redeepening following four-and eight-incision radial keratotomy were studied in a series of human cadaver eyes. Keratometry was measured with both the Terry keratometer and corneascope photographs. After eight incisions, induced corneal flattening for each clear zone (Terry keratometry readings) was 3.0 mm, 9.06 diopters; 4.0 mm, 6.44 D; 5.0 mm, 5.23 D; and 6.0 mm, 2.29 D. Differences were statistically significant, except for the 4.0-mm and 5.0-mm zones. Induced corneal flattening following eight incisions (corneoscopy) was 3.0 mm, 9.83 D; 4.0 mm, 8.87 D; 5.0 mm, 6.04 D; and 6.0 mm, 2.59 D. Differences were statistically significant, except for the 3.0-mm and 4.0-mm zones. Peripheral redeepening of the incisions did not significantly increase the amount of corneal flattening for any optical zone, as measured by the Terry keratometer. However, the 3.0-mm optical zone flattened an additional 1.23 D after the redeepening incisions, as measured by corneoscopy. The redeepening incisions were complicated by perforations in 38% of the eyes. Titrating the effect of radial keratotomy by varying the size of the optical zone appears to be valid, but the value of peripheral redeepening in the acute laboratory situation is not supported by these data.

Despite the introduction of ultrasonic axial length measurements and a variety of intraocular lens implant prediction formulas, postoperative predicted errors greater than 2 diopters occur in approximately 5% to 10% of lens implantations, and occasional errors of 5 diopters to 7 diopters or greater are still encountered. An informal survey revealed successful lens implant exchanges for initial postoperative refractive errors of +4.37 to -14.00 diopters in eight eyes.