Kurt A. Buzard

Corneal transplant for keratoconus: Results in early and late disease

Purpose: To evaluate the results and complication 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. Conclusion: The risk‐benefit ratio 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.

Treatment of mild to moderate keratoconus with laser in situ keratomileusis

PURPOSE To evaluate the effectiveness, stability, and complications of laser in situ keratomileusis (LASIK) to treat myopic astigmatism in patients with keratoconus. SETTING Buzard Eye Institute, Las Vegas, Nevada, USA. METHODS This study included 16 eyes of 9 patients who had keratometric and/or clinical evidence of keratoconus. Mean age was 45 years, and refraction was stable for at least 2 years. Two treatment approaches were evaluated. RESULTS Mean preoperative spherical equivalent was -4.23 diopters (D) +/- 2.14 (SD) with a mean steep keratometry of 46.81 +/- 3.07 D. Mean preoperative keratometric cylinder was 3.08 +/- 2.22 D. Mean postoperative keratometric cylinder was 3.00 +/- 4.78 D and mean spherical equivalent, -0.44 +/- 0.86 D. Mean postoperative steep keratometry was 44.12 +/- 7.17 D. Two eyes lost 1 line of best corrected visual acuity (BCVA), 1 eye lost 3 lines, and 2 lost 4 lines. Penetrating keratoplasty (PKP) was scheduled in 3 eyes 1 to 2 years after the primary LASIK. CONCLUSION The initial visual results appear promising; but longer term results revealed regression of the refractive outcome in some cases. Moreover, despite improvement in the postoperative spherical equivalent and uncorrected visual acuity in most cases, the risk of loss of BCVA and the necessity of performing PKP in 3 cases lead us not to consider LASIK as a primary solution for keratoconus.

Comparison of postoperative astigmatism with incisions of varying length closed with horizontal sutures and with no sutures.

ABSTRACT Four groups of cataract patients having phacoemulsification with a scleral tunnel incision were studied. Three groups had incision lengths of 5.0, 6.0, and 6.5 min closed with a single horizontal suture. The fourth group of patients had 5.0 mm incisions without suture closure. We found no statistical difference between these groups in the vector astigmatic changes over a four week period and subsequently over a 6.9 ± 3.7 week period. The patients in all groups returned to their preoperative astigmatic values within one to two weeks within the statistical significance achieved in this study.

Two cases of toxic anterior segment syndrome from generic trypan blue

&NA; We report 2 cases of toxic anterior segment syndrome (TASS) resulting from impurities in generic trypan blue that was administered intracamerally to improve visualization of the capsule. Histology of the corneal buttons revealed foci of inflammatory response and complete loss of endothelial cells. Cell culture analysis showed that the generic trypan blue was approximately twice as toxic to the endothelium as a proprietary trypan blue. Ophthalmologists should be aware that any substance administered intraocularly can be a source of complications, and they should know the source of all material used in surgery. Financial Disclosure: No author has a financial or proprietary interest in any material or method mentioned.

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.

Holographic interferometry of the corneal surface

Previous attempts to analyze the corneal surface have been limited to geometric interpretation of ring displacement (Placido disc technology). Use of holographic interferometry allows real time optical measurement of the corneal surface. Clinical examples of holographic interferometry are presented.

Pilocarpine in the Management of Overcorrection After Radial Keratotomy

BACKGROUND Induced hyperopia is a potential complication of radial keratotomy with few effective treatments. We report the results of a retrospective study to evaluate the effectiveness of pilocarpine in the treatment of eyes overcorrected by radial keratotomy. METHODS Sixteen eyes of 14 patients, from a consecutive pool of 200 eyes who underwent radial keratotomy, had hyperopia. The patients were subsequently treated with topical pilocarpine. The patients were treated from 3 to 14 weeks (mean, 8.2 weeks). RESULTS The mean time of diagnosis of hyperopia was 3 weeks after the surgery (range, 1 to 12 weeks). The mean spherical equivalent of the manifest (fogging) refraction was +1.92 diopters (D) (range, +0.75 D to +5.00 D) and the keratometric power ranged from 31.25 D to 41.00 D (mean, 36.05 D). Mean uncorrected visual acuity before the treatment with pilocarpine was 20/50. After the treatment with pilocarpine, the mean spherical equivalent refraction was -0.31 D (range, -1.75 D to +0.50 D). The mean keratometric power was 38.32 D (range, 34.87 D to 43.12 D), with a mean uncorrected visual acuity at 20/25. The patients were followed for 8 to 49 weeks after treatment without pilocarpine (mean, 21 weeks). The mean spherical equivalent refraction and keratometric readings after that period were -0.71 D (range, -2.25 D to +0.25 D) and 38.33 D (range, 36.12 D to 43.12 D), respectively. All eyes in this study had more than 1.00 D of reduction of hyperopia at the conclusion of the study. CONCLUSION Pilocarpine effectively reduced overcorrections after radial keratotomy. After termination of treatment, the steepening of corneal curvature was maintained.

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.

Induction of astigmatism by straight transverse corneal incisions, 45° long, at different clear zones in human cadaver eyes

BACKGROUND Two of the major factors affecting the amount of astigmatism correction are the length of the transverse incision and its distance from the center of the cornea. Many nomograms used in clinical practice have been created by varying the length or clear zone diameter of the incisions. A simplification of this situation has been suggested by Thornton, who has theorized that straight transverse incisions, subtending 45 degrees of arc, have equal astigmatic corrective effect at different clear zones. Our study tested Thorntons theory in human donor eyes. METHODS Ten eyes were tested at four clear zones: 5.0, 6.0, 7.0, and 8.0 mm. Paired straight transverse incisions, subtending an arc of 45 degrees (2.1 to 3.3 mm long), were centered on the 90-degree meridian. Preoperative keratometric readings at the 180- and 90-degree meridians were compared to the postoperative readings; the difference was the total astigmatism induced. We also calculated the coupling ratio. RESULTS Students t-tests comparing clear zones 6.0 and 7.0 mm revealed a statistical difference (p = .0085) in total astigmatic induction, greater for the 6.0-millimeter zone. The coupling ratio decreased as the clear zone diameter increased, presumably as a result of diminished flattening effect along the incised meridian. One-way analysis of variance indicated that the groups were different (p = .0001), and that the theory noted above was incorrect. CONCLUSIONS The effect of transverse incisions subtending the same angular length, drops off dramatically with clear zones larger than 6.0 mm, contrary to the theory of Thornton. This effect may be due to reduction in coupling as the clear zone diameter increases, suggesting that the greatest efficacy is achieved for transverse incisions placed between 5.0- and 6.0-millimeter zones.