Treatment of irregular astigmatism with a broad beam excimer laser.

BACKGROUND: Four basic types of irregular astigmatism are described: central elevation, central flat area, eccentric elevation, and eccentric flat area. METHODS: The importance of the Munnerlyn formula is shown for the treatment of irregular astigmatism. A new diagnostic entity is described, the steep/flat ratio, modeled on the inferior/superior ratio described previously in keratoconus. Calculation of the steep/flat ratio is described using the cross sectional view of videokeratography, leading to specific treatments for the four types of irregular astigmatism. Surgical technique using the VISX Star excimer laser for repeated laser in situ keratomileusis (LASIK) is described. RESULTS: Case studies are given for each of the forms of irregular astigmatism showing improved topographic appearance and indicating treatment parameters. In each case, improvement of both uncorrected and spectacle-corrected visual acuity is demonstrated. CONCLUSIONS: Irregular astigmatism is an important complication of refractive surgery. Four basic forms of irregular astigmatism can be treated with a broad beam excimer laser.

Assessment of corneal wound healing by interactive topography.

INTRODUCTION: Constitutive properties of the cornea and wounds within the cornea have been measured previously by destructive methods in which a strip of cornea was removed, placed on an instrument, and stretched until broken. To assess corneal wound healing and the interaction of medication, incision patterns and other clinical issues, we present a simple, noninvasive test of corneal wound healing utilizing a videokeratoscope and Honan balloon. METHODS: A pre-test corneal topography was performed. The Honan balloon was placed on the eye at a pressure of 30mm mercury for 5 minutes. After removal of the balloon, additional corneal topographies were performed for comparison to the baseline topography. Study eyes were divided into six groups: 15 eyes in the normal group not involved in the Honan balloon test, 15 eyes formed a control group without previous ocular surgery, 15 eyes were within 3 months of radial keratotomy (RK), 15 eyes were more than 9 months after RK, 12 eyes had previous automated in situ keratomileusis (ALK), and 12 eyes had previous penetrating keratoplasty (PK). RESULTS: Average videokeratometric flattening was reported for all groups at intervals of 1, 2, and 3 minutes after removal of the Honan balloon. The normal group flattened by 0.04 +/- 0.10 D (range, +0.10 to -0.12 D) at 1 minute; 0.02 +/- 0.08 D (range, +0.10 to -0.10 D) at 2 minutes; and 0.02 +/- 0.06 D (range, +0.10 to -0.09 D) at 3 minutes. The control group flattened by -0.10 +/- 0.10 D (range, +0.30 to -0.30 D) at 1 minute; 0.01 +/- 0.12 D (range, +0.15 to -0.25 D) at 2 minutes; and 0.07 +/- 0.11 D (range, +0.14 to -0.18 D) at 3 minutes. The 3-month RK group flattened 0.95 +/- 0.23 D (range, 1.35 to 0.67 D) at 1 minute; 0.53 +/- 0.16 D (range, 0.71 to 0.39 D) at 2 minutes; and 0.40 +/- 0.15 D (range, 0.56 to 0.30 D) at 3 minutes. The 9-month RK group flattened 0.10 +/- 0.13 D (range, 0.23 to 0.02 D) at 1 minute; 0.10 +/- 0.12 D (range, 0.18 to -0.01 D) at 2 minutes; and 0.01 +/- 0.14 D (range 0.05 to 0.10 D) at 3 minutes. The ALK group flattened 0.65 +/- 0.42 D (range 0.98 to 0.38 D) at 1 minute; 0.27 +/- 0.19 D (range 0.39 to 0.10 D) at 2 minutes; and 0.21 +/- 0.17 D (range, 0.29 to 0.09 D) at 3 minutes. The PK group flattened 1.30 +/- 0.60 D (range, 1.75 to 0.90 D) at 1 minute; 1.18 +/- 0.43 D (range, 1.51 to 0.98 D) at 2 minutes; and 0.41 +/- 0.57 D (range, 0.88 to 0.30 D) at 3 minutes. CONCLUSIONS: We have established normal corneal wound healing curves from preliminary data utilizing Buzard interactive topography on normal control eyes and after radial keratotomy, automated lamellar keratoplasty, and penetrating keratoplasty. Deviation from these normal curves indicates either excessive or inadequate wound healing.

Transient central corneal steepening after radial keratotomy.

Three case studies are presented illustrating topographic transient central steep island following radial keratotomy. Three stages are apparent: first, a central corneal steepening; next, an overcorrection with exaggerated central flattening; and, finally, the final refractive correction. The steepening is probably caused by temporary midperipheral swelling of the cornea.

The effect of various methods of eye immobilization on corneal topography.

BACKGROUND: Accurate, predictable, and safe refractive surgery requires immobilization of the eye. We measured the effects of current eye fixation techniques on human cadaver eyes. MATERIALS AND METHODS: Central to our study was a device specially designed to secure cadaver eyes and stabilize intraocular pressure. Topographical measurements were made with a modified Model 2 Corneal Analysis System (EyeSys Technologies, Houston, Tex) mounted vertically to allow analysis of a cadaver eye mounted in the artificial orbit. The effect on human cadaver eyes of six fixation instruments was assessed: forceps, U-shaped fixation forceps, a full Hofman-Thornton ring, a VISX vacuum fixation ring, a Meditec suction ring, and a new instrument, the Eye Fixation Speculum. RESULTS: The circular vacuum fixation rings caused minimal distortion, resulting in less than 1.00 diopter (D) of change. Forceps and U-shaped fixation forceps, which apply force at one or two points, caused significantly more distortion. Single-point fixation forceps distorted the cornea at the point of application a mean of +5.50 +/- 3.50 D, and, at 180 degrees from the point of instrument application, a mean of +2.00 +/- 1.90 D. U-shaped forceps apply force at two points, 90 degrees and 270 degrees, from the axis of instrument application. At these axes, the cornea was distorted a mean of +9.40 +/- 3.70 D and +8.30 +/- 3.10 D, respectively. CONCLUSIONS: Single- and multi-point fixation instruments, due to an asymmetric application of fixation force, significantly distort the cornea. Ring fixation instruments, which apply a more equally distributed force, cause less distortion.

Corneal transplant for keratoconus: results in early and late disease.

PURPOSE: To evaluate the results and complications rates associated with corneal transplantation for keratoconus and assess the prospects of using penetrating keratoplasty at a much earlier stage. SETTING: Buzard Eye Institute, Las Vegas, Nevada, USA. METHODS: In this prospective clinical study, 104 eyes of 76 patients had corneal transplantation for keratoconus identified by corneal topography, keratometry, pachymetry, and/or retinoscopy. Sutures were removed at a mean of 15 months; mean follow-up was 42 months. All surgeries were performed by one surgeon using a torque-antitorque suture method. Eyes were grouped according to severity of the disease: early (n = 24); moderate (n = 47); high (n = 33). Preoperative keratometry was 40.00 to 49.00, 50.00 to 59.00, and 60.00 to 90.00 diopters (D), respectively. The criteria for corneal transplant were a best spectacle-corrected visual acuity of 20/40 or worse and keratoconus clearly identified by one of the above methods. Secondary procedures included repair of wound dehiscence (33 eyes, 31%), relaxing incisions (33 eyes, 31%), wedge resections (5 eyes, 5%), and automated lamellar keratoplasty (4 eyes, 4%). RESULTS: Mean postoperative uncorrected visual acuity at last follow-up was 0.43 +/- 0.3 (20/50), with 46 eyes (44%) achieving 20/40 or better. Mean best corrected visual acuity (BCVA) at last follow-up was 0.83 +/- 0.2 (20/25). Sixty eyes (58%) achieved 20/40 or better BCVA at 1 month and 92 eyes (88%), at 3 months. At last follow-up, mean average keratometric astigmatism was 3.10 +/- 1.70 D, mean keratometry was 43.30 +/- 2.20 D, and mean spherical equivalent was -1.70 +/- 3.00 D. Complications included 21 graft rejections (20%); 19 were successfully treated with topical and oral steroids. No expulsive hemorrhage or endophthalmitis occurred. CONCLUSIONS: The risk-benefit for corneal transplantation has been significantly altered by improved surgical and postoperative techniques. The improved results, low complication rate, and postoperative enhancement management indicate that corneal transplantation is a viable option early in the clinical course of keratoconus.

Excimer laser assisted in situ keratomileusis for hyperopia.

PURPOSE: To evaluate hyperopic surgical correction with 6.0 mm optical zone hyperopic laser in situ keratomileusis (LASIK) after various refractive procedures. SETTING: Buzard Eye Institute, Las Vegas, Nevada, USA. METHODS: This study followed 14 eyes of 14 patients who had hyperopic LASIK with a VISX Star laser. Mean follow-up was 8 months. The patients represented a variety of preoperative situations, including primary radial keratotomy (RK) (5 eyes) primary automated lamellar keratectomy (ALK) (2 eyes), primary LASIK (3 eyes), congenital hyperopia (1 eye), and combinations of ALK, RK, and LASIK. In all patients, a toroidal or "doughnut-shaped" ablation was constructed with the use of a 3.5 mm diameter soft contact lens as a blocking agent centrally with a 6.0 mm outside beam diameter. RESULTS: Mean preoperative spherical equivalent was +1.33 diopters (D) +/- 0.5 (SD) (range +0.50 to +1.88 D). The mean spherical equivalent was -0.32 +/- 1.20 D (range -1.25 to +2.63 D) at 1 month postoperatively and -0.15 +/- 0.60 D (range -1.13 to +1.25 D) at the last follow-up. Uncorrected visual acuity of 20/40 was obtained by 13 eyes (93%). No eye lost 2 or more lines of best corrected visual acuity at last follow-up. Four eyes required a postoperative LASIK enhancement procedure to correct induced myopia. No significant complications were seen. CONCLUSION: Hyperopic LASIK with the technique used in this study appeared safe, predictable, and stable. It represents a simple way to add hyperopic correction to existing laser systems.

Automated keratomileusis in situ: clinical study of 142 eyes.

PURPOSE: To compare a modified automated lamellar keratoplasty (ALK) technique that uses two blades with the original technique, which uses one blade. SETTING: Buzard Eye Institute, Las Vegas, Nevada. METHODS: This study comprised 142 eyes of 85 patients who had ALK: 107 using the original one-blade technique (Group 1) and 35 eyes using the modified two-blade technique (Group 2). Mean follow-up was 11 months in Group 1 and 3 months in Group 2. RESULTS: Mean preoperative spherical equivalent was -8.93 diopters (D) +/- 2.80 (SD) in Group 1 and -8.33 +/- 2.80 D in Group 2. No patient had worse than 20/80 best corrected visual acuity preoperatively. Mean spherical equivalent at 1 month was -2.06 +/- 2.00 D in Group 1 and -0.79 +/- 1.20 D in Group 2 (P < .05). Mean postoperative spherical equivalent at last follow-up was -0.43 +/- 0.90 and -0.65 +/- 1.10 D, respectively. At last follow-up, 104 eyes (97%) in Group 1 and 34 (97%) in Group 2 had a spherical equivalent between +1.00 and -3.00 D, and 90 eyes (84%) in Group 1 and 27 (77%) in Group 2 had 20/40 uncorrected visual acuity. Seven eyes (7%) in Group 1 and 1 (3%) in Group 2 lost two or more lines of best corrected visual acuity at last follow-up. Three months after ALK (for equal comparison), 25 eyes (23%) in Group 1 and 3 (8%) in Group 2 required radial keratotomy; 20 (19%) and 2 (6%), respectively, needed ALK revision; and 45 eyes (42%) and 17 (47%) needed astigmatic keratotomy. CONCLUSIONS: The results suggest that ALK is capable of impressive myopic corrections across a broad range of refractive error. The procedure is not accurate enough with a single microkeratome pass and requires enhancement procedures including recuts of the bed with the microkeratome and astigmatic and radial keratotomies. Using two blades to achieve an even cut gives better spherical equivalent and best corrected visual acuity results and lower enhancement rates.

Clinical results of arcuate incisions to correct astigmatism.

PURPOSE: To evaluate the effectiveness of arcuate incisions for correcting congenital, post-cataract, post-radial keratotomy, and post-trapezoidal keratotomy astigmatism. SETTING: Buzard Eye Institute, Las Vegas, Nevada. METHODS: In this retrospective study, 46 eyes of 29 patients had arcuate incisions to correct astigmatism. The average age of patients was 52 years. RESULTS: Mean preoperative astigmatism was 3.51 +/- 1.57 D (keratometric) and 3.41 +/- 1.44 D (manifest). Mean preoperative uncorrected visual acuity was 20/80, ranging from 20/30 to 20/400. Thirty eyes had a pair of 45-degree arcuate incisions, 10 eyes had a pair of 60-degree arcuate incisions, and 6 eyes had a pair of 90-degree arcuate incisions. Mean follow-up was 6 months. Mean postoperative astigmatism was 1.46 +/- 1.07 D (keratometric) and 1.05 +/- 0.94 D (manifest), with a reduction of astigmatism in all operated eyes. Mean postoperative uncorrected visual acuity was 20/32, ranging from 20/20 to 20/60. The analysis of the vector astigmatic change showed that only two patients were overcorrected after the procedure. CONCLUSION: The predictability and safety of arcuate incisions are reflected in these results.

Combined phacoemulsification and trabeculectomy with mitomycin-C.

PURPOSE: To examine the safety and efficacy of primary combined phacoemulsification, posterior chamber intraocular lens (IOL) implantation, and trabeculectomy with mitomycin-C (0.4 mg/ml) in patients with open-angle glaucoma and visually significant cataract. SETTING: University-hospital-based glaucoma referral practice. METHODS: In this study, data of 43 patients of a single surgeon were retrospectively analyzed. These consecutive patients had combined phacoemulsification, posterior chamber IOL implantation, and trabeculectomy with mitomycin-C. RESULTS: Thirty-eight patients (88%) had open-angle glaucoma and 5 (12%) pseudoexfoliative glaucoma. Thirty-eight patients (88%) had 12 months of follow-up; all had at least 6 months follow-up. Mean preoperative intraocular pressure (IOP) was 21.6 mm Hg +/- 6.8 (SD) (range 12.0 to 41.0 mm Hg) with 2.5 +/- 1.0 glaucoma medications. At last follow-up, mean IOP had decreased to 14.2 +/- 6.2 mm Hg (range 3.0 to 40.0 mm Hg) with 0.5 +/- 0.5 glaucoma medications. Twenty-one patients (55%) had an IOP of 15 mm Hg or less at 12 months. Best corrected visual acuity was 20/40 or better in 31 of 43 patients (72%) at last follow-up. A filtration bleb was noted in 33 of 40 patients (83%) at their last visit. Postoperative IOP spikes occurred in 17 patients (40%), transient hyphema in 12 (28%), transient wound leaks in 11 (26%), and superficial punctate keratopathy in 11 (26%). Three cases of persistent hypotony (IOP less than 5 mm Hg) and 1 case of epithelial downgrowth were also noted. CONCLUSION: Phacoemulsification with IOL implantation and combined trabeculectomy with mitomycin-C produced good visual acuity and excellent IOP control but resulted in some complications. The use of mitomycin-C in combined procedures does not appear to confer a significant benefit.

193-nm excimer photorefractive keratectomy in high myopia.

PURPOSE: To evaluate the refractive results of 193-nm excimer laser photorefractive keratectomy (PRK) performed on 48 highly myopic eyes in a multicenter study. METHODS: A Visx 2015 or 2000 argon-fluoride excimer laser and a single-zone ablation technique were used. Postoperatively, eyes were treated with topical fluoromethalone for up to 5 months. Most eyes were treated with a 6.0- to 6.2-mm beam diameter after undercorrections and increased regression were noted with a 5.5-mm beam in earlier studies. Forty-eight eyes were treated for myopia, which was between -8.0 and -15.25 diopters (D) (spherical equivalent). The mean preoperative refraction was -11.2 D. Retreatment was performed after 6 to 16 months on 11 eyes for undercorrection. All eyes not retreated were followed for at least 12 months. RESULTS: At 6 months, follow-up was available on 47 eyes. Of these eyes, 40% and 64% achieved corrections within 1 and 2 D of attempted correction, respectively. At 1 year, 60% of eyes attained 20/40 visual acuity or better uncorrected. Eleven patients (23%) were retreated between 6 to 16 months for undercorrection and/or regression. After retreatment, 47% and 81% of eyes achieved corrections within 1 and 2 D of attempted correction, respectively. At 1 year, 15% of eyes lost two lines of best-corrected visual acuity, and no eyes lost more than two lines. There was slightly more corneal haze seen in this group compared with the haze seen in patients undergoing PRK for low and moderate myopia. CONCLUSIONS: These data show that excimer PRK can correct high amounts of myopia with reasonable stability after 6 months. Excimer PRK is an effective surgical treatment of severe myopia, but long-term follow-up is still needed to assess the stability of its effect.