Survey of patients with granular, lattice, avellino, and Reis-Bücklers corneal dystrophies for mutations in the BIGH3 and gelsolin genes.

OBJECTIVES: To search for novel mutations that cause corneal stromal dystrophies and to confirm or revise the clinical diagnosis of patients with these mutations. PATIENTS: Through review of the records of the Cogan Eye Pathology Laboratory at the Massachusetts Eye and Ear Infirmary, Boston, and of clinical records, we ascertained 14 unrelated patients with the clinical or histopathologic diagnosis of granular (3 cases), Avellino (5 cases), lattice (5 cases), or Reis-Bücklers (1 case) corneal dystrophy. METHODS: Clinical records and histopathologic findings of the index patients and their relatives were reviewed. Patients and selected relatives donated a blood sample from which leukocyte DNA was purified and assayed for mutations in the BIGH3 gene and, in 2 patients, the gelsolin gene, using the polymerase chain reaction and direct genomic sequencing. RESULTS: All index patients with the diagnosis of granular dystrophy or Avellino dystrophy had the missense mutation Arg555Trp or Arg124His, respectively, previously reported in the BIGH3 gene. Of the 5 index patients with a prior diagnosis of lattice dystrophy, 2 had the originally reported lattice mutation (Arg124Cys) in the BIGH3 gene, 1 had a more recently reported missense mutation (His626Arg) in the same gene, 1 had the missense mutation Asp187Asn in the gelsolin gene, and 1 had no detected mutation in either gene. Affected members of the family with Reis-Bücklers dystrophy did not carry the previously reported mutations Arg555Gln or Arg124Leu but instead carried a novel missense mutation Gly623Asp in the BIGH3 gene. CONCLUSIONS: Molecular genetic analysis can improve the accuracy of diagnosis of patients with corneal dystrophies. Two patients with a prior diagnosis of lattice corneal dystrophy had their diagnosis changed to gelsolin-related amyloidosis (1 case) or secondary, nonhereditary localized amyloidosis (1 case). A novel mutation in the BIGH3 gene that causes Reis-Bücklers dystrophy was uncovered through this analysis, and another recently reported novel mutation was encountered. These findings serve to expand our knowledge of the spectrum of pathogenic mutations in BIGH3.

Late traumatic dislocation of laser in situ keratomileusis corneal flaps.

PURPOSE: To report the management and outcome of late-onset traumatic dislocation of laser in situ keratomileusis (LASIK) flaps. DESIGN: Retrospective, observational case series. PARTICIPANTS: Four patients with late-onset LASIK flap dislocation occurring after mechanical trauma at various intervals (10 days-2 months) after the procedure. INTERVENTION: In all cases of postoperative traumatic LASIK flap dislocation, the flap was refloated with scraping and irrigation of the underlying stromal bed within 12 hours of the injury. A bandage contact lens was placed, and a regimen including topical antibiotics and corticosteroids was instituted in all cases. MAIN OUTCOME MEASURES: Best spectacle-corrected visual acuity and complications associated with the surgery were monitored. RESULTS: Postoperative follow-up ranged from 4 to 21 months. Nonprogressive epithelial ingrowth was noted in one patient and diffuse lamellar keratitis developed in another patient. All patients recovered pretrauma spectacle-corrected visual acuity. CONCLUSIONS: Corneal LASIK flaps are prone to mechanical dislocation as late as 2 months after the procedure. Appropriate management results in recovery of optimal visual outcomes.

Management of severe flap wrinkling or dislodgment after laser in situ keratomileusis.

PURPOSE: To review the management and results of cases with severe flap wrinkling or dislodgment after laser in situ keratomileusis (LASIK). SETTING: University Eye Center, Department of Ophthalmology and Visual Sciences, Prince of Wales Hospital, The Chinese University of Hong Kong. METHODS: Four patients with severe flap wrinkling or dislodgment after LASIK are described. Surgical repositioning of the flap was performed in all cases. Flap status, refractive changes, and final uncorrected and best corrected visual acuities were used to evaluate the outcome of flap repositioning. RESULTS: Flap repositioning required suturing in 2 patients, 1 of whom developed severe epithelial ingrowth with melting of the corneal flap and stromal bed and eventually required flap removal. The stromal inflammation resolved, and the corneal surface re-epithelialized after flap excision. In 2 other patients, wedge-shaped tissue excision (1.0 x 1.5 mm) from the superior portion of the corneal flap was necessary to allow better flap realignment. In 1 of these patients, the corneal flap was eventually converted to a free cap to correct residual wrinkling. At a mean follow-up of 15 months, the postoperative uncorrected visual acuity ranged from 20/20 to 20/60, and the best spectacle-corrected visual acuity (BSCVA) was 20/30 or better in all patients. In 1 patient, BSCVA decreased by 1 line. CONCLUSIONS: Flap dislodgment and wrinkling are serious postoperative complications of LASIK. Early recognition of these complications and prompt surgical management are crucial to achieve a successful surgical and visual outcome.

Evaluation of pentoxifylline in the prevention of haze after photorefractive keratectomy in the rabbit.

BACKGROUND: Pentoxifylline (PTX) is a methylxanthine derivative that, besides its hemorrheologic properties, possesses multiple physiologic effects at the cellular level. It has been used in keloid prevention due to its ability to inhibit the secretion of collagen and glycosaminoglycans from activated fibroblasts. METHODS: Ten New Zealand White (NZW) rabbits underwent a -7.00 diopters, 6.0 mm diameter photorefractive keratectomy after laser ablation of the epithelium with a VISX 20/20 excimer laser. The bare stroma was stained with fresh 0.5% dichlorotriazinyl aminofluorescein (DTAF). The procedure was performed on both eyes, 4 days apart. One eye received 1% Pentoxifylline qid and the other balanced salt solution qid as a control for 4 weeks, starting the same day of surgery. Two masked observers graded the amount of haze at 2, 4, 6, and 8 weeks after surgery using slit-lamp biomicroscopy. Three rabbits were sacrificed at 2 and 4 weeks followed by two rabbits at 6 and 8 weeks. The area between the DTAF-stained collagen to the base of the epithelium was measured using a digital image analyzer. RESULTS: There was no statistically significant difference in the amount of haze either by slit-lamp microscopy or by histological analysis between the pentoxifylline-treated eyes and the controls at any time interval (Student's t-test: 0.16 to 0.92) CONCLUSION: Pentoxifylline did not seem to affect haze formation in a PRK rabbit model. As no signs of toxicity were observed, further studies might examine higher concentrations or dose frequencies.

Late onset of haze associated with viral keratoconjunctivitis following photorefractive keratectomy.

BACKGROUND: To report a newly recognized cause of late onset of corneal haze following photorefractive keratectomy (PRK). METHODS: A 35-year old woman who underwent uneventful PRK and subsequently developed viral keratoconjunctivitis 1 year after treatment. RESULTS: During resolution of the viral keratoconjunctivitis, the patient developed extensive central corneal subepithelial infiltrates and anterior stromal fibrosis in the PRK ablation zone. More than 1 year after the initial infection, the central subepithelial fibrosis persisted, complicated by myopic regression, central steep island on videokeratography, and loss of five lines of spectacle-corrected visual acuity. By the end of the second year after the infection, visual acuity had improved with disappearance of the central steep island on videokeratography. However, the myopic regression and subepithelial fibrosis remained. CONCLUSION: Patients who undergo PRK may be at greater risk of visual loss following viral keratoconjunctivitis secondary to persistent subepithelial infiltrates and/or stromal fibrosis within the PRK treatment zone.

A prospective evaluation of alcohol-assisted versus mechanical epithelial removal before photorefractive keratectomy.

OBJECTIVE: The purpose of the study is to compare alcohol-assisted versus mechanical debridement of the corneal epithelium before photorefractive keratectomy (PRK) for low-to-moderate myopia. DESIGN: A prospective study was performed on a group of consecutive patients operated on at the Massachusetts Eye and Ear Infirmary from February to April 1996 and followed for 6 months. PARTICIPANTS: Eighty patients (eyes) were divided in 2 groups: 40 alcohol and 40 mechanical. INTERVENTION: The patients underwent PRK for myopia (-1.5 to -7.5 diopters) with a Summit Apex excimer laser. The corneal epithelium was removed either with 20% ethanol or with a scalpel blade. MAIN OUTCOME MEASURES: The two groups were compared for epithelial removal time, epithelial defect size at the end of surgery, and rate of re-epithelialization. Uncorrected visual acuity (UCVA), refractive outcome, best-corrected visual acuity (BCVA), and subjective haze were measured at 4 days and at 1, 3, and 6 months. In an additional short-term study, 40 patients (20 alcohol, 20 mechanical) had intraoperative pachymetry performed. RESULTS: Alcohol-assisted de-epithelialization was faster than mechanical debridement (107 [+/-20.6 standard deviation] versus 141 [+/-30.5] seconds [P < 0.0001]) and led to a more circumscribed and reproducible epithelial defect at the end of surgery (87,739 [+/-11,852] versus 103,518 [+/-33,942] square pixels [t test, P = 0.04; f test, P = 0.001]). At 4 days, 95% of the alcohol-treated patients had healed compared with 78% of the mechanically scraped patients (Fisher's exact test, P = 0.04). The alcohol group had a better UCVA at 4 days (logarithm of the minimum angle of resolution UCVA 0.36 [+/-0.22] versus 0.51 [+/-0.26]) and at 1 month (0.14 [+/-0.17] versus 0.22 [+/-0.16] [Mann-Whitney U test, P = 0.02 and P = 0.03]) but equalized at 3 months (0.10 [+/-0.14] versus 0.13 [+/-0.16]) and at 6 months (0.11 [+/-0.15] versus 0.14 [+/-0.13] [Mann-Whitney U test, P = 0.23 and P = 0.34]). There was a trend toward less subjective haze in the alcohol-treated patients over the course of the study (area under the curve, 71.9 [+/-35.3] versus 87.9 [+/-33.8] [Mann-Whitney U test, P = 0.07]). The difference from target was equivalent in both groups at 6 months (-0.22 [+/-0.58] diopter in the alcohol group and -0.43 [+/-0.52] diopter in the mechanical group [t test, P = 0.14; f test, P = 0.57]). There were no differences in intraoperative pachymetry, corneal uniformity index as calculated from the corneal topography, and loss of BCVA between the two groups. CONCLUSIONS: Twenty percent ethanol is a simple, safe, and effective alternative to mechanical scraping before PRK and appears to be associated with a quicker visual rehabilitation.

Effects of 50% ethanol and mechanical epithelial debridement on corneal structure before and after excimer photorefractive keratectomy.

PURPOSE: The corneal epithelium is generally removed before photoablation in photorefractive keratectomy (PRK) because laser transepithelial PRK may result in surface irregularity caused by variability in epithelial thickness and differing ablation rates between epithelium and stroma. We compared the effects of mechanical deepithelialization with chemical epithelial removal by using 50% ethanol on the corneal structure. METHODS: Fourteen rabbits underwent corneal deepithelialization by using a blade in the left eye and 24 h later in the right eye. Another 14 rabbits underwent corneal deepithelialization by using 50% ethanol solution. Half of the eyes treated with each technique underwent PRK after deepithelialization. Pachymetry was performed before and after each procedure on right eyes. Keratocyte and neutrophil densities were assessed by light microscopy. RESULTS: Among non-laser-treatment groups, eyes that underwent mechanical deepithelialization had decreased corneal thickness (p = 0.001), increased keratocyte densities (p = 0.03), and no significant difference in neutrophil densities (p = 0.91) compared with chemically treated eyes 24 h after surgery. Among laser-treatment groups, eyes that underwent mechanical epithelial removal had increased keratocyte densities (p = 0.001), decreased corneal thickness (p = 0.03), and increased neutrophil densities (p = 0.03) 24 h after surgery compared with chemically treated eyes. CONCLUSION: Deepithelialization with 50% ethanol causes more keratocyte loss with perhaps more corneal edema, but less stromal influx of neutrophils, than does a mechanical technique 24 h after PRK in a rabbit model. Corneal deepithelialization with dilute ethanol may be a viable option in PRK. However, further investigation into the safety of this technique is warranted before it can be widely applied clinically.

Hydrops and spontaneous perforation in pellucid marginal corneal degeneration.

PURPOSE: Pellucid marginal degeneration of the cornea (1,2) is an idiopathic condition characterized by noninflammatory, nonulcerative thinning of the inferior, peripheral cornea. Occasionally the condition is complicated by acute corneal hydrops (3). We describe a patient with findings suggestive of pellucid marginal corneal degeneration who experienced acute hydrops and spontaneous perforation of the cornea. METHOD: A retrospective analysis of the case was conducted. RESULTS: A 56-year-old woman was seen with decreased vision in the left eye. Clinical findings, including computerized corneal topography, were suggestive of pellucid marginal degeneration. Two weeks later, the patient had hydrops and spontaneous perforation of the left cornea. Medical workup of the patient and histopathologic and microbiologic studies of the corneal specimen revealed no contributory disease process. The patient underwent emergency tectonic lamellar keratoplasty and is doing well after subsequent optical penetrating keratoplasty. CONCLUSION: We believe this is the first report of a case of pellucid marginal degeneration of the cornea complicated by hydrops and perforation.

Acanthamoeba keratitis: is water exposure a true risk factor?

PURPOSE: Water exposure has been commonly cited in the literature as a significant risk factor for the development of Acanthamoeba keratitis. The purpose of this study was to test the hypothesis that the incidence of tap and contaminated water exposure in Acanthamoeba keratitis patients is no higher than in the normal contact lens population. METHODS: We retrospectively reviewed all patients all patients diagnosed with Acanthamoeba keratitis at Massachusetts Eye & Ear Infirmary from 1990-1994, and compared this group to a control population of healthy contact lens wearers assessed by a self-report questionnaire. RESULTS: A history of water exposure was reported by 64% (seven patients) diagnosed with Acanthamoeba keratitis. In comparison, 100% of the control population of healthy contact lens wearers (100 patients) reported comparable water exposure, and 87% of controls reported multiple sources of water exposure. CONCLUSIONS: The finding that the incidence of water exposure is actually lower in patients with Acanthamoeba keratitis than in the general contact lens population suggests that water exposure may be less important, and other factors more important in the development of this disease than previously assumed.

Dilute ethanol versus mechanical debridement before photorefractive keratectomy.

PURPOSE: To compare 18% ethanol versus mechanical epithelial debridement in a group of patients having photorefractive keratectomy (PRK) for low to moderate myopia or astigmatism. SETTING: Hospital San Jose de Monterrey, Mexico. METHODS: This prospective, paired study comprised 18 patients who had bilateral PRK between June 1994 and March 1995. One eye had ethanol (alcohol) debridement and the other, mechanical. Time between PRKs was about 6 months. The two groups (alcohol versus mechanical) were compared for rate of re-epithelialization, refractive outcome, improvement in uncorrected visual acuity (UCVA), subjective haze grading, and loss of best corrected visual acuity (BCVA). RESULTS: There was a nonsignificant trend in the alcohol-treated eyes toward a more rapid visual recovery. One week after PRK, 76% in the alcohol group but only 31% in the mechanical group had a UCVA of 20/40 or better. There were no significant between-group differences in rate of re-epithelialization, refractive outcome, subjective haze grading, and loss of BCVA. CONCLUSION: Chemical de-epithelialization with dilute ethanol appears to be a simple, safe, and effective alternative to mechanical scraping before PRK and might promote faster visual rehabilitation.

Comparison of suture-in and suture-out postkeratoplasty astigmatism with single running suture or combined running and interrupted sutures.

PURPOSE: To evaluate postkeratoplasty astigmatism between two suture techniques 2 to 4 years postoperatively in a group of patients previously studied 9 months postoperatively. METHODS: Thirty-two patients who underwent penetrating keratoplasty were randomly assigned to one of two groups. Group 1 (16 patients) had a 24-bite single running 10-0 nylon suture with postoperative suture tension adjustment; group 2 (16 patients) had combined 16-bite running and eight interrupted 10-0 nylon sutures with selective postoperative removal of interrupted sutures. During long-term follow-up, the running suture was removed in 19 patients (59%). RESULTS: Postoperative astigmatism was slightly lower in patients with the single running suture technique when sutures were in place and was slightly greater after the sutures were removed compared with the combined running and interrupted suture technique (sutures in: single running suture +/- SD, 2.6 +/- 1.2 diopters [five patients, 31%]; combined running and interrupted sutures, 3.8 +/- 1.1 diopters [eight patients, 50%]; sutures out: single running suture, 3.3 +/- 1.3 diopters [11 patients, 69%]; combined running and interrupted sutures, 2.8 +/- 1.5 diopters [eight patients, 50%]). These differences were not statistically significant (sutures in, P < .13; sutures out, P < .46). Averages of follow-up were group 1,48.3 +/- 10.6 months and group 2, 46.3 +/- 13.0 months. Follow-up ranged from 23 to 60 months. CONCLUSIONS: Postoperative astigmatism 4 years after penetrating keratoplasty is similar for these two suturing techniques, with or without residual sutures. A single running suture results in more rapid visual rehabilitation and less early astigmatism compared with the combined interrupted and running suture technique.

Excimer photorefractive keratectomy for low myopia and astigmatism with the Coherent-Schwind Keratom.

PURPOSE: To summarize the initial results of excimer laser photorefractive keratectomy (PRK) in 114 eyes of 89 patients using the Coherent-Schwind system and assess its safety, efficacy, and predictability. SETTING: Hospital San Jose de Monterrey-ITESM, Mexico. METHODS: The Coherent-Schwind Keratom excimer laser was used to correct low myopia (manifest spherical equivalent from -1.00 to -6.00 diopters [D], with manifest cylinder of -1.00 D or less) or myopic astigmatism (manifest spherical equivalent from -2.75 to -6.75 D, with manifest cylinder from -1.00 to -4.50 D) with standard settings. Ablation zone diameters were from 5.9 to 6.3 mm (low myopia) and 5.9 to 8.2 mm (astigmatism) with a repetition rate of 12 Hz. Follow-up was from 1 month (low myopia, n = 71; astigmatism, n = 35) to 6 months (low myopia, n = 36; astigmatism, n = 17). RESULTS: Six months after PRK, uncorrected visual acuity was 20/40 or better in 94% of the low myopia eyes (n = 36) and 77% of the astigmatism eyes (n = 17). Intended correction was within 1.00 D of the target spherical equivalent in 81 and 88% of eyes, respectively. No eyes in the low myopia group lost two lines of best corrected visual acuity, although 12% in the astigmatism group did. CONCLUSION: The Coherent-Schwind excimer laser appears to be effective in the treatment of low myopia and astigmatism, with results comparable to those of other laser systems after 6 months of follow-up. Further study of best corrected visual acuity loss after treatment of compound myopic astigmatism with this laser is warranted.

Assessment of ablation zone centration after photorefractive keratectomy using a vector center of mass formula.

BACKGROUND: Adequate centration of keratorefractive surgical procedures is essential for a successful outcome. An accurate technique to mathematically describe the centration and topography of the ablation zone after photorefractive keratectomy (PRK) would be valuable in assessing the effects of these variables on subsequent visual results. METHODS: A vector center of mass formula and computerized videokeratography were used to study the postoperative treatment zone centration and topography of 17 consecutive highly myopic patients (-6.00 to 12.00 diopters [D]). Each had undergone PRK using either a single 6.0 mm (n = 11) or three-stepped ablation zone (n = 6), with good visual results. RESULTS: Calculations disclosed mean ablation zone decentration relative to the pupil center for all patients to be 0.20 +/- 0.16 mm using the vector center of mass formula. Areas of uniform central corneal dioptric power (mean diameter 3.4 +/- 0.8 mm) and surrounding transition zones of declining dioptric power (mean slope 1.61 +/- 0.44 D/mm) were also determined. CONCLUSION: A new vector center of dioptric power distribution that analyzes centration and transition zone topography offers a rigorous but straightforward means to assess the effects of refractive corneal surgery procedures on central corneal topography.

Implantation of collagen plugs into incisional keratotomies.

PURPOSE: To evaluate whether supplementing incisional keratotomy bulk or gape with a biocompatible material enhances the refractive effect. SETTING: Refractive Surgery Laboratory, Massachusetts Eye and Ear Infirmary, Boston. METHODS: Collagen punctal plugs were implanted into astigmatic keratotomy (AK) incisions in the right eyes of five rabbits and six adult cats. The left eyes had AK only and served as controls. RESULTS: Some of the postoperative corneal topographic measurements suggested an enhanced refractive effect. At 1 month, histology demonstrated no remaining implant material and no inflammation in or near the incisions. CONCLUSIONS: Implanting a biocompatible material into AK incisions in two live animal models appears to be safe and may enhance the effect of the incisions. Further study is needed to quantify the magnitude and duration of any refractive effect.

Temperature measurements during phacoemulsification and erbium:YAG laser phacoablation in model systems.

PURPOSE: To compare the potential for thermal injury to ocular structure resulting from phacoemulsification ultrasound energy and erbium:YAG (Er:YAG) laser output. SETTING: Morse Laser Laboratory, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston. METHODS: Ultrasonic phacoemulsification energy and ER:YAG laser output (10 J/cm2, 10 Hz, 0.3 watts) sufficient for lens removal were applied to model systems and human cadaver eyes. Temperatures were measured with ultrafine thermocouples interfaced to a microcomputer data acquisition system. RESULTS: Although greater than 95% of energy from laser output is converted to thermal energy, temperature rise in model systems and cadaver eyes was 10 to 15 times greater after pulsed application of ultrasound energy than after Er:YAG laser application. At 100% power, approximately 4 watts of ultrasound power is converted to heat. Temperature rise following both laser and ultrasound applications decreased with irrigation in cadaver eyes and increasing volume in a model system. With continuous irrigation (20 cc/min), the temperature rise at 2 minutes measured at the corneal endothelial surface, within the corneal stroma, and in the anterior chamber angle of cadaver eyes was approximately 0.5 degrees Celsius (degrees C) after laser application and 7.0 degrees C after ultrasound application. Without irrigation, temperatures rose 2.5 degrees C after laser application and 35.0 degrees C after ultrasound application. CONCLUSION: At operating parameters sufficient for lens removal, the Er:YAG laser imparted less thermal energy to whole eyes and model systems than ultrasonic phacoemulsification.

Measurement and modeling of thermal transients during Er:YAG laser irradiation of vitreous.

BACKGROUND AND OBJECTIVE: We investigated the transient thermal behavior of vitreous in order to understand the local thermal effects of laser output, and to predict the potential for unintentional injury during Er:YAG laser vitreoretinal surgery. STUDY DESIGN/MATERIALS AND METHODS: The output of a free-running Er:YAG laser (2.94 microns, 300 microseconds FWHM) was delivered through a fiberoptic and applied to en bloc samples of bovine vitreous. Temperature was measured with ultrafine thermocouples. RESULTS: For 6 mJ pulse energy at 10 Hz, a temperature rise of 20 degrees C is measured 500 microns from the laser tip. The temperature rise is localized with a rapid fall-off greater than 1 mm from the energy source. At constant time-averaged laser power, the temperature profile is independent of repetition rate. Our finite-difference model generates results qualitatively consistent with measured data and allows for investigation of the influence of thermophysical parameters on heat transfer. CONCLUSION: Thermal injury to ocular structures should be limited during intravitreal application of Er:YAG laser energy.

The combined (Genesis) technique of radial keratotomy. A prospective, multicenter study. Refractive Keratoplasty Study Group.

PURPOSE: A prospective, multicenter, clinical study to evaluate a standardized surgical (Genesis) protocol which includes combined-technique radial incisions in patients seeking reduction of their physiologic myopia. The combined incisions were designed to incorporate the safety of the centrifugal incision technique with the efficacy of the centripetal incision technique. METHODS: A total of 375 eyes undergoing radial keratotomy procedures performed in six different clinical centers were analyzed. All procedures were performed in accordance with the Genesis nomograms. The Genesis protocol called for using preoperative screening pachymetry to guide central clear zone size selection, incising the thinnest corneal quadrant first, suturing corneal perforations, and discouraged more than one enhancement procedure, when indicated. Globe fixation technique served as a study variable. RESULTS: Mean follow-up was 6.2 months (range, 1.5-12 months). Mean residual cycloplegic refraction was -0.48 +/- 0.61 diopters (D) (range, -2.50 to +1.50 D); 92% of eyes were within 1 D of the planned goal of -0.50 D and 85% were within 1 D of emmetropia; 14% were myopic; and 1% was hyperopic by more than 1 D. Uncorrected visual acuity was 20/40 or better in 95% of eyes; the remaining 5% retaining myopic refractive errors. A single procedure was performed in 73% of eyes, and 99% received less than two enhancements. Of eyes with no enhancements, 97% had uncorrected visual acuity of 20/40 or better. One study eye (0.3%) had a two-line loss of spectacle visual acuity. There were no invasions of the central clear zone. Globe fixation was a significant predictor for enhancement incidence (P < 0.001) but not for perforation incidence (P = 0.06). Incision sequence was predictive for perforation incidence (P < 0.0002). CONCLUSION: The combined-technique of radial keratotomy, coupled with the Genesis surgical protocol, affords centrifugal incision safety with centripetal incision efficacy. The Genesis nomograms, with a built in refractive outcome goal of -0.50 D provide an acceptable degree of accuracy and predictability while guarding against hyperopic overcorrection.