Photorefractive keratectomy versus laser in situ keratomileusis for moderate to high myopia. A randomized prospective study

Thin-flap laser-assisted in situ keratomileusis

PURPOSE OF REVIEW

Concerns regarding the increasing incidence of corneal ectasia following laser in situ keratomileusis procedures, together with increased understanding of the biomechanics of the cornea, has resulted in many refractive surgeons returning to surface ablation techniques such as photorefractive keratectomy. Even if surface ablation techniques offer a higher degree of safety than LASIK, they are associated with more pain and a slower visual recovery in the immediate postoperative period. This highlights the need for alternative procedures that offer the combined advantages of laser in situ keratomileusis and photorefractive keratectomy.

RECENT FINDINGS

Sub-Bowman's keratomileusis is a new procedure that provides the biomechanical stability and associated safety of photorefractive keratectomy with the visual results and reduced pain experience of laser in situ keratomileusis. This technique involves the use of the femtosecond laser to create a customized corneal flap of between 90 and 110 mum with a diameter based on the requirements of the individual patient and the type of excimer laser being used.

SUMMARY

This review outlines the rationale for sub-Bowman's keratomileusis and describes the efficacy, tolerability and safety of the procedure compared with photorefractive keratectomy.

Photorefractive keratectomy with mitomycin C versus LASIK in custom surgeries for myopia: a bilateral prospective randomized clinical trial

PURPOSE

To compare photorefractive keratectomy (PRK) with prophylactic use of mitomycin C (MMC) and LASIK in custom surgeries for myopic astigmatism.

METHODS

Eighty-eight eyes of 44 patients with a minimum estimated ablation depth of 50 microm were randomized to receive PRK with MMC 0.002% for 1 minute in one eye and LASIK in the fellow eye. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), cycloplegic refraction, slit-lamp microscopy, contrast sensitivity, specular microscopy, aberrometry, and a subjective questionnaire were evaluated. Forty-two patients completed 6-month follow-up.

RESULTS

Mean spherical equivalent refraction error before surgery and mean ablation depth were -3.99+/-1.20 diopters (D) and 73.09+/-14.55 microm in LASIK eyes, and -3.85+/-1.12 D and 70.7+/-14.07 microm in PRK with MMC eyes, respectively. Uncorrected visual acuity was significantly better in PRK with MMC eyes 3 months (P=.04) and 6 months (P=.01) after surgery. Best spectacle-corrected visual acuity and spherical equivalent refraction did not differ significantly in the groups during follow-up (P>.05). Significant haze was not observed in any PRK with MMC eye. Mean higher order aberration was lower in PRK with MMC eyes postoperatively compared with LASIK eyes (P=.01). Better contrast sensitivity was observed in PRK with MMC eyes than LASIK eyes (P<.05). The endothelial cell count did not differ significantly between groups (P=.65). In terms of visual satisfaction, PRK with MMC eyes were better rated.

CONCLUSIONS

Photorefractive keratectomy with MMC appears to be more effective than LASIK in custom surgery for moderate myopia. During 6-month follow-up, no toxic effects of MMC were evident. Long-term follow-up is necessary to attest its safety.

Wavefront-guided excimer laser ablation using photorefractive keratectomy and sub-Bowman's keratomileusis: a contralateral eye study

PURPOSE

To explain the basic science and clinical evidence that has led to the development of a new technique in corneal refractive surgery--sub-Bowman's keratomileusis (SBK).

METHODS

A comprehensive review of the literature and report of a contralateral eye study of 50 patients (100 eyes) enrolled at 2 sites (25 patients per site) and randomized according to the dominant eye was conducted. All eyes underwent a wavefront-guided refractive correction using the Alcon LADARVision4000 System. In one eye, an 8.5-mm, ETOH-assisted photorefractive keratectomy (PRK) was performed. In the second eye, an 8.5-mm, 100-microm flap was attempted using a 60 kHz IntraLase FS femtosecond laser. Pre- and postoperative tests included best spectacle-corrected visual acuity, uncorrected visual acuity, corneal topography, wavefront aberrometry, retinal image quality, contrast sensitivity, and biomechanical response of the cornea. Patients completed subjective questionnaires at each follow-up.

RESULTS

Clinical results demonstrate that SBK provides quicker visual recovery, although the data suggest that the 3- and 6-months results are similar in terms of visual outcomes. Reichert Ocular Response Analyzer results demonstrate that its impact on the cornea is similar to PRK.

CONCLUSIONS

This study indicates that SBK provides the visual recovery of a LASIK procedure with the Optical Response Analyzer results similar to PRK.

[A prospective intraindividual comparison between laser in situ keratomileusis and laser subepithelial keratectomy for myopia. 1-year follow-up results]

BACKGROUND

The aim of this study was to intraindividually compare the outcome of laser in situ keratomileusis (LASIK) and laser subepithelial keratectomy (LASEK) in patients with similar refraction in both eyes when treated with two different procedures.

PATIENTS AND METHODS

In this prospective nonrandomized study, 30 myopic patients with and without astigmatism were treated by Lasik in one eye and LasEk in the fellow eye. All eyes were treated using the MEL 70-G Excimer laser (Carl Zeiss Meditec, Germany). Uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA) as well as photopic contrast sensitivity (Pelli-Robson charts) and scotopic contrast sensitivity (Nyktometer, Rodenstock, Germany) were evaluated. The patients were also asked about their preferences regarding the procedures.

RESULTS

The preoperative spherical equivalent (SE) was -4.54+/-1.64 D and the mean BSCVA was 0.94 in Lasik eyes. The SE was -3.9+/-1.57 D and the BSCVA was 0.89 in LASEK eyes. The mean 1-year post-operative SE was -0.33+/-0.48 D in the Lasik eyes and -0.19+/-0.26 D in the LASEK eyes. Efficacy and safety were similar in the two groups, but Lasik eyes had a greater standard deviation at 1 year. Pelli-Robson contrast sensitivity was 10.75+/-3.05 in the Lasik eyes compared with 11.4+/-3.21 in the fellow LASEK eyes. Seventeen patients named Lasik and 12 patients named LASEK as their procedure of choice.

CONCLUSION

Both procedures enable similarly good results. LASEK showed a tendency to a smaller standard deviation in final refraction and better contrast sensitivity.

Effects of antiglaucoma drugs on refractive outcomes in eyes with myopic regression after laser in situ keratomileusis

PURPOSE

To assess effects of antiglaucoma drugs on refractive outcomes in eyes with myopic regression after laser in situ keratomileusis (LASIK).

DESIGN

Prospective, nonrandomized clinical trial.

METHODS

We examined 27 eyes with mean myopic regression +/- standard deviation of -1.26 +/- 0.48 diopters (D; range, -0.50 to -2.25 D) after LASIK. Nipradilol 2.5% was administered topically twice daily to these regressive eyes. We obtained the refraction (spherical equivalent, astigmatism), intraocular pressure (IOP) measurements, pachymetry, geometry, and refractive power of the cornea before and three months after treatment.

RESULTS

Mean manifest refraction was improved significantly from -1.02 +/- 0.52 D to -0.44 +/- 0.39 D (P < .001). However, mean manifest astigmatism was changed from -0.55 +/- 0.30 D to -0.49 +/- 0.22 D, but the difference was not significant (P = .23). The IOP was decreased significantly from 11.4 +/- 2.4 mm Hg to 9.4 +/- 1.3 mm Hg (P < .001). Central corneal thickness was not changed significantly from 505.2 +/- 39.3 microm to 503.6 +/- 38.7 microm (P = .61). The posterior corneal surface was shifted posteriorly by 9.1 +/- 8.2 microm, and the total refractive power of the cornea was decreased significantly, by 0.63 +/- 0.62 D (P < .001), at three months after application.

CONCLUSIONS

The preliminary data show that antiglaucoma drugs are effective for the reduction of the refractive regression, especially of the spherical errors, after LASIK. It is suggested that backward movement of the cornea may occur, possibly flattening the corneal curvature by lowering the IOP. Reduction of the IOP may contribute to improving regression after keratorefractive surgery.

Ten-year follow-up of laser in situ keratomileusis for myopia of up to -10 diopters

PURPOSE

To evaluate the long-term outcomes of laser in situ keratomileusis (LASIK) for myopia of up to -10 diopters (D).

DESIGN

A long-term (10-year) follow-up retrospective, interventional case series.

METHODS

The study included 97 eyes of 70 patients with a preoperative spherical equivalent (SE) of up to -10 D treated with myopic LASIK at the Instituto Oftalmológico de Alicante, Alicante, Spain, using the VISX 20/20 excimer laser (Santa Clara, California, USA) and the Automated Corneal Shaper microkeratome (Chiron Vision, Irvine, California, USA). All patients were evaluated three months, one year, two years, five years, and 10 years after surgery. The main outcome measures were refractive predictability and stability, mean corneal keratometry, topographical cylinder, safety, efficacy, stability of visual acuity, and postoperative complications.

RESULTS

At 10 years, 71 (73%) of 97 eyes were within +/- 1.00 D and 89 (92%) were within +/- 2.00 D. Twenty eyes (20.8%) underwent retreatments because of overcorrection, undercorrection, regression, or both. The mean SE slightly decreased (myopic regression) over 10 years, with a mean myopic regression of -0.12 +/- 0.16 D per year. Fifty-four (54.6%) of 97 eyes demonstrated an increase in best spectacle-corrected visual acuity (BSCVA) after 10 years. No eye developed corneal ectasia in the long-term, and only three eyes lost more than two lines of BSCVA because of complications that were not attributable to the LASIK procedure.

CONCLUSIONS

LASIK for myopia of up to -10 D is a safe and effective procedure with slight myopic regression that slows down with time and a high rate of BSCVA increase in the long-term.

Ten-year follow-up of laser in situ keratomileusis for high myopia

PURPOSE

To evaluate the long-term outcomes of laser in situ keratomileusis (LASIK) for high myopia.

DESIGN

A long-term (10 years) follow-up retrospective interventional case series study.

METHODS

The study included 196 myopic eyes of 118 patients with a mean preoperative spherical equivalent of -13.95 +/- 2.79 diopter (D) treated with myopic LASIK at the Instituto Oftalmológico de Alicante, Spain using the VISX 20/20 excimer laser (VISX Inc, Santa Monica, California, USA) and the Automated Corneal Shaper microkeratome (Chiron Vision, Irvine, California, USA). All patients were evaluated three months, one year, two years, five years, and 10 years postoperatively. The main outcome measures were refractive predictability and stability, mean corneal keratometry, topographical cylinder, safety, efficacy, stability of visual acuity, and postoperative complications.

RESULTS

At 10 years, 82 (42%) of 196 eyes were within +/-1.00 D and 119 (61%) were within +/-2.00 D. Fifty-four (27.5%) eyes underwent retreatments attributable to under correction and/or regression. The myopic regression decreases with time in eyes that did not undergo retreatment with a mean rate of -0.25 +/- 0.18 D per year. Eleven eyes (5%) lost more than 2 lines of best spectacle-corrected visual acuity (BSCVA) and 78 eyes (40%) showed a postoperatively uncorrected visual acuity of 20/40 or better. Two eyes (1%) with more than 15 D myopic correction developed corneal ectasia.

CONCLUSIONS

LASIK for myopia over -10 D is a safe procedure with myopic regression that slows down with time and a high rate of BSCVA increase in the long-term.

LASEK and Photorefractive Keratectomy for Myopia: Clinical and Confocal Microscopy Comparison

PURPOSE

To compare postoperative visual acuity and corneal morphology after laser epithelial keratomileusis (LASEK) versus photorefractive keratectomy (PRK) in the correction of low to moderate myopia.

METHODS

In a double-blind, randomized clinical trial, 50 myopic patients (mean: -4.5 +/- 1.35 diopters) were randomized to receive LASEK in one eye and PRK in the fellow eye. No mitomycin C eye drops were used in this study. Patients were observed daily for 4 days, then at 1 month and every 3 months up to 1 year. Uncorrected and best-corrected visual acuity (UCVA and BSCVA), manifest refraction, corneal epithelium healing time, postoperative pain, and corneal haze were evaluated. Corneal wound healing was quantified with corneal confocal microscopy.

RESULTS

Refractive error, UCVA, and BSCVA were not statistically different between eyes treated with LASEK and PRK. Corneal epithelium healing time was 2.52 +/- 0.99 days in the eyes treated with PRK and 2.29 +/- 0.52 days in the eyes treated with LASEK (P=.22). The postoperative pain score was 2.17 +/- 0.87 in the eyes treated with PRK and 2.62 +/- 0.60 (P=.02) in the eyes treated with LASEK. Corneal confocal microscopy showed fewer stromal activated keratocytes and less extracellular matrix deposition in the eyes treated with LASEK than in the eyes treated with PRK at 1 month postoperatively (P=.003).

CONCLUSIONS

LASEK is an effective and safe procedure for low to moderate myopia, but it seems more painful until full corneal reepithelization. In the early postoperative period, the corneal wound healing process is significantly less intense in eyes treated with LASEK than in eyes treated with PRK. The role of LASEK in corneal wound healing modulation remains controversial.

Long-term Study of Artisan Phakic Intraocular Lens Implantation for the Correction of Moderate to High Myopia

PURPOSE

To determine the long-term performance of the Artisan phakic intraocular lens (PIOL) for the correction of myopia.

DESIGN

Long-term (10 years) retrospective follow-up study.

PARTICIPANTS

Eighty-nine eyes of 49 patients who underwent Artisan PIOL implantation for the correction of myopia.

METHODS

Comparisons were made between preoperative clinical data and the clinical data at 1, 6, and 10 years after surgery.

MAIN OUTCOME MEASURES

Refractive stability, refractive predictability, safety, efficacy, best-corrected visual acuity (BCVA), uncorrected visual acuity (UCVA), intraocular pressure, intraoperative problems, corneal endothelial cell density, corneal endothelial cell loss, and glare levels were evaluated.

RESULTS

The mean spherical equivalent (SE) after 10 years was -0.70+/-1.00 diopters (D; range, -4.00 to 2.00 D), with no significant change in mean SE between 1, 6, and 10 years. At 10 years, 68.8% of all eyes were within 1.0 D of the intended correction. At 10 years, 31.2% (n = 24) gained 1 or more Snellen lines of BCVA and 2.6% (n = 2) lost more than 2 Snellen lines of BCVA; 93.3% reached a BCVA of 20/40 or better, and 82.0% reached a UCVA of 20/40 or better. The mean intraocular pressure remained stable and was 15.5+/-3.5 mmHg (range, 7-25 mmHg) at 10 years. The mean endothelial cell loss was -8.86+/-16.01% (range, -51.69% to 34.43%) at 10 years.

CONCLUSIONS

Long-term results demonstrate that the implantation of an Artisan PIOL for the correction of moderate to high myopia is a stable, predictable, and safe method when strict inclusion criteria for surgery are applied. There was no significant loss of corneal endothelial cells and no reports of long-term glare.

Outcomes of Wavefront-Optimized Surface Ablation

PURPOSE

To compare early visual outcomes after wavefront-optimized advanced surface ablation (ASA) with those after wavefront-optimized LASIK.

DESIGN

Retrospective comparative series.

PARTICIPANTS

One hundred thirty-six eyes undergoing ASA and 136 preoperative refraction-matched eyes undergoing LASIK from June 2004 through October 2005.

METHODS

Database review of preoperative characteristics, including patient age, gender, refraction, and central corneal pachymetry; perioperative information, including type of surgery, flap thickness (for LASIK cases), ablation depth, and residual stromal bed thickness; and postoperative information, including uncorrected visual acuity (UCVA) at 1 day, 1 week, 2 weeks, and 3 months, refraction at 3 months, and complications. All ASA patients had topical mitomycin C applied intraoperatively.

MAIN OUTCOMES MEASURES

Postoperative UCVA, best spectacle-corrected visual acuity (BSCVA), spherical equivalent (SE) refraction, speed of visual recovery, and postoperative complications.

RESULTS

Surface ablation patients were younger (35.4 years vs. 39.8 years, P = 0.0002) and had thinner corneas (514 microm vs. 549 microm, P<0.0001) preoperatively. Average UCVA was significantly better after LASIK at 1 day (20/26.8 vs. 20/50.4, P<0.0001) and 2 weeks (20/24.4 vs. 20/33.3, P = 0.0002) postoperatively. However, by 3 months postoperatively, UCVA was better after ASA (20/20.8 vs. 20/22.7, P = 0.05), and 81.5% of patients achieved 20/20 or better UCVA after ASA, compared with 70.5% after LASIK (P = 0.05). More ASA eyes had postoperative UCVA that achieved or surpassed preoperative BSCVA than LASIK eyes (66% vs. 41.6%, P<0.0001). There were 53 patients who underwent bilateral simultaneous ASA. By 1 week, 87.5% had 20/40 or better UCVA in at least one eye and 62.5% had 20/40 or better UCVA in both eyes. By 2 weeks, 86.8% had 20/40 or better UCVA in one eye and 82.6% had 20/40 or better UCVA in both eyes.

CONCLUSION

Initial visual recovery is more rapid after LASIK; however, by 3 months postoperatively UCVA and SE refractions were better after ASA. Advanced surface ablation is an effective alternative to LASIK, and based on early visual recovery, bilateral simultaneous surface ablation is a reasonable alternative to sequential surgery for the majority of patients.

Laser Epithelial Keratomileusis for the Correction of Hyperopia Using a 7.0-mm Optical Zone With the Schwind ESIRIS Laser

PURPOSE

To investigate the efficacy of laser epithelial keratomileusis (LASEK) for the correction of hyperopia using a 7.0-mm optical zone and a 9.0-mm total ablation zone diameter with the Schwind ESIRIS flying-spot laser.

METHODS

Forty-seven patients (70 eyes) were treated with a mean preoperative spherical equivalent refraction of +2.32 diopters (D) (range: 0 to +5.00 D). All eyes underwent LASEK using 15% alcohol with a 20-second application.

RESULTS

An intact epithelial flap was obtained in 66 (94%) eyes. In 70 eyes at 12 months, the mean spherical equivalent refraction was +0.09 D (range: -0.75 to +1.00 D) with all (100%) eyes within +/- 1.00 D of the intended correction and 60 (86%) eyes within +/- 0.50 D. In 40 eyes with 24-month follow-up, the refractive correction remained stable after 6 months. Hyperopic cylindrical corrections were attempted in 49 eyes (range: +0.25 to +5.00 D) with vector analysis demonstrating a mean 102% correction at 12 to 24 months. In 60 non-amblyopic eyes, uncorrected visual acuity was > or = 20/20 in 47 (78%) eyes. Thirty-three (47%) eyes gained 1 to 2 lines of Snellen decimal equivalent best spectacle-corrected visual acuity, 30 (43%) eyes showed no change, and 7 (10%) eyes lost 1 line. Eight (11%) eyes at 12 to 24 months had grade +/- 1 of paracentral corneal haze and 57 (81%) had no haze. At 12 months (n = 70), the safety index was 1.06 with an efficacy index of 0.95. Analysis of higher order wavefront aberrations showed no significant changes in root-mean-square values post-operatively, except for a significant reduction of fourth order spherical aberration (P < .05).

CONCLUSIONS

Laser epithelial keratomileusis for hyperopia up to +5.00 D using a 7.0-mm optical zone with the Schwind ESIRIS laser provides excellent refractive and visual outcomes with minimal complications. In eyes followed for 24 months, the refractive correction remained stable after 6 months.

Uses and complications of mitomycin C in ophthalmology

Mitomycin C is a chemotherapeutic agent that acts by inhibiting DNA synthesis. Its use and application in ophthalmology has been increasing in recent years because of its modulatory effects on wound healing. Current applications include pterygium surgery, glaucoma surgery, corneal refractive surgery, cicatricial eye disease, conjunctival neoplasia and allergic eye disease. Although it has been used successfully in these conditions, it has also been associated with significant complications. This article reviews the current trends and uses of mitomycin C in the eye and its reported complications.

Postoperative Pain Following Epi-LASIK, LASEK, and PRK for Myopia

PURPOSE

To compare mechanical epithelial separation using the epi-LASIK technique with alcohol assisted separation (LASEK).

METHODS

Patients deemed suitable for surface ablation were randomized to receive epi-LASIK in one eye and LASEK in the other eye. If epi-LASIK failed, the procedure was converted to photorefractive keratectomy (PRK), forming the third comparison group. The outcome measures were postoperative pain, vision, refraction, and haze. Patients were followed for 3 months.

RESULTS

Fifty-seven patients (95 eyes) were included in this study (38 epi-LASIK, 19 PRK, and 38 LASEK eyes). There was a 33% rate of conversion from intended epi-LASIK to PRK. Epi-LASIK patients were found to have significantly less pain in the first few hours after surgery but at 4 hours all patients had the same levels of pain, which improved to minimal or no pain at 24 hours. No significant difference was noted among groups for vision, refractive error, and haze; however, epi-LASIK patients had the best day 1 visual acuity.

CONCLUSIONS

Epi-LASIK offers comparable visual and refractive results to other surface ablation techniques with lower levels of postoperative pain only for the first 2 hours. However, there was a high rate of flap failure and conversion to PRK.

A control-matched comparison of laser epithelial keratomileusis and laser in situ keratomileusis for low to moderate myopia

PURPOSE

To compare the visual and refractive outcomes of laser epithelial keratomileusis (LASEK) and laser in situ keratomileusis (LASIK) for the treatment of low to moderate myopia.

DESIGN

Retrospective, nonrandomized, control-matched study.

METHODS

The charts of 2257 eyes that underwent LASEK or LASIK treatment were reviewed. Patients who were 21 years of age or older having between -0.75 and -6.00 diopters (D) of myopia with up to -2.25 D of astigmatism were included. One hundred twenty-two LASEK-treated eyes were matched with 122 LASIK-treated eyes having preoperative spheres, cylinders, and spherical equivalent (SE) within +/-0.50 D. Both groups had similar preoperative best spectacle-corrected visual acuity (BSCVA), laser platform, and follow-up durations. Outcome measures were visual and refractive results.

RESULTS

Preoperatively, the mean SE was -3.50 +/- 1.40 D for LASEK and -3.50 +/- 1.42 D for LASIK (P = .59). Postoperatively, the mean logarithm of minimum angle of resolution (logMAR) uncorrected visual acuity (UCVA) was 0.01 +/- 0.08 (20/21) for LASEK and 0.06 +/- 0.12 (20/23) for LASIK; the mean SE was -0.15 +/- 0.40 D for LASEK and -0.37 +/- 0.45 D for LASIK; and the mean logMAR of BSCVA was -0.03 +/- 0.06 (20/19) for LASEK and -0.02 +/- 0.05 (20/19) for LASIK. No eye lost 2 or more lines of BSCVA in both groups.

CONCLUSIONS

Slight differences in the visual and refractive results between LASEK and LASIK were observed, despite the use of the same nomogram. Both procedures were safe, effective, and predictable. Nomogram adjustment may be necessary for LASIK surgeons adopting surface ablation.

Optical Quality Analysis After Surface Excimer Laser Ablation: The Relationship Between Wavefront Aberration and Subepithelial Haze

PURPOSE

To investigate the relationship between mild and moderate corneal haze and the distribution of higher order wavefront aberrations after photorefractive keratectomy (PRK).

METHODS

Thirty-six eyes from 18 patients who underwent PRK were divided into two groups: 10 eyes with corneal haze and 26 eyes without corneal haze (control). All eyes were evaluated up to 6 months after PRK. Wavefront aberrations were measured using a psychophysical wavefront sensor and the NIDEK OPD-Scan. Topography, point spread function, and modulation transfer function maps were obtained from the OPD-Scan.

RESULTS

The mean total higher order aberration was slightly higher in the corneal haze group than in the control group. This difference was not statistically significant. The mean third order coma aberrations were higher and mean fourth order spherical aberrations were lower in the haze group compared with the control group, although neither difference attained statistical significance. The t test values were 1.05, -0.38, -1.10, -0.08, and -0.23, when comparing the mean third, fourth, fifth, sixth, and seventh order aberrations, respectively. None of these differences attained statistical significance. In terms of Zernike coefficients, Z-1 and Z1 showed greater mean root-mean-square (RMS) in the haze group (0.33 and 0.35 microm, respectively) than those for the control group (0.26 and 0.23 microm, respectively) (t=0.71 and P=.49; t=0.84 and P=.43, respectively). However, ZO had lower RMS in the haze group (0.18 microm) than in the control group (0.28 microm). This difference also was not statistically significant.

CONCLUSIONS

In this study comparing the optical aberrations of eyes with and without corneal haze after PRK, corneal haze did not affect the magnitude and distribution of higher order aberrations in a predictable manner.

Evidence for Superior Efficacy and Safety of LASIK over Photorefractive Keratectomy for Correction of Myopia

PURPOSE

To examine possible differences in efficacy and safety between LASIK and photorefractive keratectomy (PRK) for correction of myopia.

DESIGN

Meta-analysis/systematic review.

PARTICIPANTS

Patient data from previously reported prospective randomized controlled trials (PRCTs) and a systematic review of prospective case series in the Food and Drug Administration (FDA) clinical trials database.

METHODS

A comprehensive literature search was performed using the Cochrane Collaboration methodology to identify PRCTs comparing LASIK and PRK for correction of myopia. A meta-analysis was performed on the results of PRCTs. In parallel, a systematic review of prospective data from FDA case series of LASIK and PRK for correction of myopia was undertaken.

MAIN OUTCOME MEASURES

Key efficacy outcomes (uncorrected visual acuity [UCVA] > or = 20/20, +/-0.50 diopters [D] of the target mean refractive spherical equivalent) and safety outcomes (loss of > or =2 lines of best spectacle-corrected visual acuity [BSCVA], final BSCVA > or = 20/40, and final BSCVA < 20/25 where preoperative BSCVA was > or =20/20).

RESULTS

Seven PRCTs were identified comparing PRK (683 eyes) and LASIK (403 eyes) for correction of myopia. More LASIK patients achieved UCVA > or = 20/20 at 6 months (odds ratio, random effects model [95% confidence interval], 1.72 [1.14-2.58]; P = 0.009) and 12 months (1.78 [1.15-2.75], P = 0.01). Loss of > or =2 lines of BSCVA at 6 months was less frequent with LASIK (2.69 [1.01-7.18], P = 0.05). Data from 14 LASIK (7810 eyes) and 10 PRK (4414 eyes) FDA laser approval case series showed that more LASIK patients achieved UCVA of 20/20 or better at 12 months (1.15 [1.03-1.29], P = 0.01), significantly more LASIK patients were within +/-0.50 D of target refraction at 6 months (1.38 [1.26-1.50], P<0.00001) and 12 months (1.21 [1.08-1.36], P = 0.0009) after treatment, and loss of > or =2 lines of BSCVA at 6 months was less frequent with LASIK (2.91 [2.22-3.83], P<0.00001).

CONCLUSIONS

LASIK appears to have efficacy and safety superior to those of PRK. However, the data examined are from studies conducted > or =5 years ago. It is therefore unclear how our findings relate to present-day methods and outcomes. Further trials comparing contemporary equipment and techniques are needed to reevaluate the relative merits of these procedures.

Comparison of Laser Epithelial Keratomileusis With and Without the Use of Mitomycin C

PURPOSE

To analyze the results of prophylactic intraoperative use of mitomycin C (MMC) in laser epithelial keratomileusis (LASEK).

METHODS

A retrospective analysis of 30 LASEK cases that received MMC 0.02% intraoperatively (MMC group) was performed and compared to the results obtained in 28 LASEK cases not receiving MMC (no MMC group). Mitomycin C was placed in contact with the ablation zone for 75 seconds with an imbibed microsponge. Both groups received postoperative fluorometholone for 3 months. Preoperative spherical equivalent refraction was -5.72 +/- 2.82 diopters (D) in the MMC group and -5.81 +/- 2.74 D in the no MMC group. Best spectacle-corrected visual acuity was 0.88 +/- 0.12 in the MMC group and 0.88 +/- 0.13 in the no MMC group.

RESULTS

Spherical equivalent refraction at 6 months postoperatively was +0.11 +/- 0.13 D in the MMC group and +0.09 +/- 0.37 D in the no MMC group. Best spectacle-corrected visual acuity was 0.90 +/- 0.13 in the MMC group and 0.88 +/- 0.13 in the no MMC group. Uncorrected visual acuity (UCVA) > or = 20/40 was obtained in 93.3% of cases in the MMC group and in 89.3% of cases in the no MMC group; UCVA > or = 20/25 was achieved in 76.6% of cases in the MMC group and in 71.4% of cases in the no MMC group. Haze incidence for the MMC group was: trace: 0%, Grades I: 0%, II: 0%, III 0%, IV: 0%, and for the no MMC group: trace: 17.9%, Grades I: 3.6%, II: 0%, III: 0%, IV: 0%. A statistically significant difference (P<.001) was noted in haze intensity between the MMC group and no MMC group.

CONCLUSIONS

Prophylactic use of intraoperative MMC in LASEK significantly decreases haze incidence.

Rethinking contact lens associated keratitis

This review presents a critical analysis of the literature relating to the use of binomial and polynomial classification schemes for categorising corneal infiltrative events (CIEs) associated with contact lens wear and the epidemiology of such events. The results of the Manchester Keratitis Study-a 12-month, prospective, hospital-based epidemiological study of contact lens wearer suffering from CIEs-are used as a tool to challenge and test traditional thinking in relation to contact lens associated keratitis. An innovative aspect of this study is the use of a novel clinical severity matrix to systematically score the severity of CIEs based on 10 key signs and symptoms. The ambiguities inherent in using binomial classification schemes (such as, microbial versus sterile, ulcerative versus non-ulcerative etcetera) are highlighted. The failure of a polynomial scheme-due to extensive classification overlap between proposed sub-types of CIEs-is demonstrated using a Venn diagram. A cartographic analysis reveals that infiltrates tend to occur in the superior cornea of patients wearing extended wear silicone hydrogel lenses, in the central cornea of patients wearing daily wear hydrogel daily disposable lenses and in the peripheral cornea of patients wearing daily wear hydrogel (excluding daily disposable) lenses. Infiltrates that occur more towards the limbus are less severe. The incidence of CIEs is higher when contact lenses are worn overnight. Logistic analysis reveals that the risk of developing a severe CIE is five times greater with conventional hydrogel extended wear versus silicone hydrogel extended wear. The male gender, smoking, a healthy eye and body, and the late Winter months are associated with an increased risk of developing CIEs. The rate of significant visual loss as a result of developing a CIE is low. Two key conclusions are drawn from this work, which represent a radical rethinking of this potentially sight-threatening condition. CIEs should be considered as a continuous spectrum of ocular disease. If a contact lens wearer presents with a sore eye that is becoming progressively worse and a CIE is observed in that eye, lens wear should be suspended and anti-microbial therapy initiated immediately.

The Influence of Incision-Induced Astigmatism and Axial Lens Position on the Correction of Myopic Astigmatism with the Artisan Toric Phakic Intraocular Lens

PURPOSE

To evaluate postoperative astigmatism with regard to incision-induced astigmatism and deviation in axial alignment with the use of preoperative limbal marking with the Javal keratometer (Haag Streit, Bern, Switzerland) in eyes implanted with the Artisan toric phakic intraocular lens (IOL) (Ophtec, Groningen, The Netherlands).

DESIGN

Prospective nonrandomized trial.

PARTICIPANTS

Fifty-four eyes of 33 patients with myopia (mean, -9.67 diopters [D]) and astigmatism (mean, -3.44 D).

INTERVENTION

The enclavation site was marked on the limbus using the Javal keratometer. The Artisan toric phakic IOL was implanted according to the axis marked on the limbus. Follow-up was a minimum of 6 months.

MAIN OUTCOME MEASURES

Safety index, efficacy index, predictability, safety, and vector analysis of total refractive correction were determined. The effects of axis misalignment and incision-induced astigmatism on the final refractive error were evaluated.

RESULTS

At 6 months after surgery, the safety index was 1.29+/-0.29 and the efficacy index was 1.04+/-0.35. Mean spherical equivalent subjective refraction reduced from -11.39+/-4.86 D before surgery to -0.38+/-0.57 D at 6 months. Sixty-seven percent of eyes were within 0.50 D of attempted refraction and 89% were within 1.00 D. Mean preoperative cylinder was 2.92+/-1.60 D at 91.4 degrees . At 6 months, the mean cylinder was 0.28+/-0.54 D at 174.3 degrees . No eyes lost 2 or more lines of best-corrected visual acuity at 6 months. Eighty-three percent of eyes achieved uncorrected visual acuity of 20/40 and 28% achieved 20/20. Vector analysis of total surgically induced astigmatism revealed a mean cylindrical change of 3.21+/-1.71 D. Average axis misalignment was 0.37+/-5.34 degrees . The mean incision-induced astigmatism was 0.74+/-0.61 D at 0.2 degrees .

CONCLUSIONS

Implantation of the myopic toric IOL leads to safe, efficacious, and predictable results. The level of unpredictability caused by minor axis IOL misalignment has minimal effects on the residual refractive error. The procedure of axis alignment with the Javal keratometer seems to be an accurate method of marking the eye for toric IOL implantation. Incision-induced astigmatism can result in an overcorrection of the cylinder. A systematic undercorrection of -0.50 D for attempted cylindrical outcome could result in an achieved correction closer to emmetropia.

Functional outcome and patient satisfaction after Artisan phakic intraocular lens implantation for the correction of myopia

PURPOSE

To determine patient satisfaction after Artisan phakic intraocular lens (PIOL) implantation to correct myopia.

DESIGN

Non-comparative prospective case series.

METHODS

One hundred twenty eyes of 60 patients who had undergone Artisan PIOL implantation to correct myopia were analyzed. A validated questionnaire that consisted of 66 satisfaction items were self-administered by patients 12 months after surgery. Clinical parameters (PIOL decentration, the difference between pupil size and PIOL optical zone, and optical aberrations) were measured. Main outcome measures of satisfaction scale scores (global satisfaction, quality of uncorrected and corrected vision, night vision, glare, day and night driving) were analyzed. Correlations with clinical parameters were obtained.

RESULTS

After surgery, 98.3% of patients were satisfied, and 73.3% of patients considered their night vision to be the same or better; 44.1% of patients reported more bothersome glare. The night vision score correlated with spheric aberration (r = -0.303; P = .020). The glare score correlated with the difference between scotopic pupil size and PIOL optical zone (r = -0.280; P = .030) and vertical coma (r = -0.337; P = .009). The night driving score correlated with postoperative spheric equivalent (r = 0.375; P = .009), total root mean square aberrations (r = -0.337; P = .017), higher order root mean square aberrations (r = -0.313; P = .027), and vertical coma (r = -0.297; P = .036).

CONCLUSION

Overall satisfaction after Artisan PIOL implantation for myopia is excellent. The quality of night vision and night driving were related to scotopic pupil size, individual higher order aberrations, and residual refractive error.

Laser eye surgery for refractive errors

Several laser and non-laser refractive surgical procedures have been used to modify the shape of the cornea and correct myopia, hyperopia, astigmatism, and presbyopia. Introduction of the excimer laser to reshape the cornea has resulted in remarkable developments in the correction of these refractive errors. Combined with other advanced ophthalmological instruments, laser refractive eye surgery has resulted in a substantial rise in the safety, efficacy, and predictability of surgical outcomes. Despite these advances, certain limitations and complications persist. In this review, we describe the history, preoperative assessment, surgical techniques, outcomes, and complications of laser refractive surgery.

Photorefractive keratectomy (PRK) versus laser-assisted in-situ keratomileusis (LASIK) for myopia

BACKGROUND

Myopia (also known as short-sightedness or near-sightedness) is an ocular condition in which the refractive power of the eye is greater than is required, resulting in light from distant objects being focused in front of the retina instead of directly on it. The two most commonly used surgical techniques to permanently correct myopia are photorefractive keratectomy (PRK) and laser-assisted in-situ keratomileusis (LASIK).

OBJECTIVES

The aim of this review was to compare the effectiveness and safety of PRK and LASIK for correction of myopia.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (2005, Issue 3), MEDLINE (1966 to September 2005), EMBASE (1980 to September 2005) and LILACs (1982 to 3 November 2005). We also searched the reference lists of the studies and the Science Citation Index.

SELECTION CRITERIA

We included randomised controlled trials comparing PRK and LASIK for correction of any degree of myopia. We also included data on adverse events from prospective multicentre consecutive case series in the Food and Drugs Administration (FDA) trials database (http//www.fda.gov/cdrh/LASIK/lasers.htm).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data. Data were summarised using odds ratio and mean difference. Odds ratios were combined using a random-effects model after testing for heterogeneity.

MAIN RESULTS

This review included six randomised controlled trials involving a total of 417 eyes, of which 201 were treated with PRK and 216 with LASIK. We found that although LASIK gives a faster visual recovery than PRK, the effectiveness of these two procedures is comparable. We found some evidence that LASIK may be less likely than PRK to result in loss of best spectacle-corrected visual acuity.

AUTHORS' CONCLUSIONS

LASIK gives a faster visual recovery than PRK but the effectiveness of these two procedures is comparable. Further trials using contemporary techniques are required to determine whether LASIK and PRK are equally safe.

Laser Subepithelial Keratomileusis for the Correction of High Myopia With the Schwind ESIRIS Scanning Spot Laser

PURPOSE

To investigate the efficacy of laser subepithelial keratomileusis (LASEK) for the correction of high myopia with the Schwind ESIRIS scanning spot laser (Schwind eye-tech-solutions Gmbh & Co, Kleinostheim, Germany).

METHODS

Fifty-one patients (76 eyes) were treated with a mean preoperative spherical equivalent refraction of -7.55 diopters (D) (range: -6.0 to -10.75 D). All eyes received a LASEK technique using 15% alcohol with a 20-second application.

RESULTS

An intact epithelial flap was obtained in 73 (96%) eyes. At 1 week, uncorrected visual acuity (UCVA) was > or =20/30 in 53 (70%) eyes and > or =20/60 in all eyes. At 6 months (n=76), the mean SE was +0.08 D (range: -1.00 to +1.875 D) with 73 (96%) eyes within +/-1.0 D of the intended correction and 60 (79%) eyes within +/-0.5 D. At 12 months (n=46), the mean SE was -0.07 D (range: -1.375 to +2.0 D) with 44 (96%) eyes within +/-1.0 D of the intended correction and 37 (80%) eyes within +/-0.5 D. Myopic cylindrical corrections were attempted in 68 eyes (range: -0.25 to -4.25 D) with vector analysis demonstrating a mean 85% correction. At last follow-up, UCVA was > or =20/20 in 47 (62%) eyes, > or =20/25 in 63 (83%) eyes, and > or =20/40 in 75 (99%) eyes. Three (4%) eyes gained two lines of Snellen decimal equivalent best spectacle-corrected visual acuity compared to preoperative levels, 68 (89%) eyes showed no change or gained one line, and 5 (7%) eyes lost one line. None lost more than one line. Only 2 (3%) eyes at 6 to 12 months had more than +1 axial corneal haze and 50 (66%) showed no evidence of haze on slit-lamp examination.

CONCLUSIONS

Laser subepithelial keratomileusis for myopia up to -11.00 D with the Schwind ESIRIS laser provides good refractive and visual outcomes, with acceptable visual recovery and minimal complications.

Complications and visual outcome of LASIK performed by anterior segment fellows vs experienced faculty supervisors

PURPOSE

To determine the complication rates and visual outcome of laser-assisted in situ keratomileusis (LASIK) that is performed by anterior segment fellows and to compare their results with the results of their experienced faculty supervisors.

DESIGN

A single-center, retrospective, interventional, nonrandomized, comparative case series.

METHODS

Chart review of the initial 50 LASIK procedures that were performed by each of 10 anterior segment fellows and the first 50 inclusion criteria-matched, contemporaneously performed cases of four faculty members at the King Khaled Eye Specialist Hospital between March and December 2003.

RESULTS

There were no statistically significant differences between fellow and faculty cases with respect to complication rates and final visual outcomes. The fellows were significantly more likely to experience microkeratome-related flap complications during their first 25 cases, compared with their second 25 cases (4.8% vs 1.2%; P = .03). Fellows were significantly more likely to perform enhancements (8.0% vs 2.0%; P = .0002), after which the eyes in their group were more likely to be within 1 diopter of the intended refractive target than those in the faculty group (96.0% vs 91.0%; P = .01). Although not statistically significant, eyes in the fellow group were four-fold (2.0% vs 0.5%) more likely to lose two or more lines of best spectacle corrected visual acuity than those in the faculty group.

CONCLUSION

To minimize the adverse impact of complications during the learning curve of novice LASIK surgeons, the introduction of this procedure in a well-structured, supervised setting (such as a subspecialty fellowship training program) is recommended.

A return to primitive practice? Radial keratotomy revisited

Recently, a refractive surgeon was quoted in the national and professional press as proposing that radial keratotomy (RK) is to be preferred over laser procedures, such as photorefractive keratectomy (PRK) and laser assisted in situ keratomileusis (LASIK). The rationale for this public recommendation was that the RK procedure achieves better visual results and fewer complications than the laser procedures. Peer reviewed literature on these refractive procedures was surveyed to establish the validity of such a statement and it was found that current data do not support the notion that RK results in better visual outcomes than PRK and LASIK The true incidence of complications is difficult to establish. However, when the post procedure chronic effects are compared between RK, PRK and LA SIK, it becomes apparent that the post-RK patient pays the highest price, by a large margin, in visual quality impairment and corneal health. Although the visual acuity outcomes for low to moderate myopes, when corrected by any of the three refractive procedures considered here, are not dramatically different, we concluded that RK is not the preferred methodology because of its associated chronic visual and corneal health complications.

Incidence and morbidity of hospital-presenting corneal infiltrative events associated with contact lens wear

AIM

To determine the incidence and morbidity (visual loss) of hospital-presenting corneal infiltrative events (CIEs) associated with the wearing of current generation contact lenses.

METHODS

All contact lens wearers presenting with any form of corneal infiltrate/ulcer to a hospital centre in Manchester, UK, were surveyed in this 12-month, prospective, hospital-based epidemiological study. A clinical severity matrix was used to quantify the overall severity of presenting signs and symptoms. The size of the hospital catchment population and the wearing modalities (daily wear [DW] or extended wear [EW]) and lens types used in that population were estimated from relevant demographic and market data to facilitate the calculation of incidence. We also attempted to ascertain, from their eye care practitioners, the visual acuity (VA) of patients suffering from CIEs prior to and at about six months following attendance at the hospital.

RESULTS

During the survey period, 118 patients presented with CIEs of varying severity. The annual incidence (cases per 10,000 wearers) for all wearing modalities and lens types is 21.3 (95 per cent confidence interval 17.8 to 25.5). The incidence of CIEs for each wearing modality and lens type is: DW rigid, 8.6 (3.9 to 18.7); DW hydrogel daily disposable, 14.0 (9.3 to 21.0); DW hydrogel (excluding daily disposable), 20.4 (15.9 to 26.2); DW silicone hydrogel, 55.9 (9.9 to 309.6); EW rigid, zero (0.0 to 1758.8); EW hydrogel, 144.6 (66.4 to 311.8) and EW silicone hydrogel, 118.6 (75.2 to 186.7). The risk of developing a CIE with EW lenses was 8.1 (5.3 to 12.5) times greater than that with DW lenses (p < 0.0001). Although there was no difference between EW hydrogel and EW silicone hydrogel lenses with respect to the risk of developing CIEs, the clinical severity of CIEs was greater with EW hydrogel lenses (p = 0.04). Results of VA for pre- and post-hospital attendance were obtained from 38 patients, none of whom lost more than one line of VA. For the study population, zero patients (95 per cent CI: 0 to 9.2 per cent) suffered a significant loss of VA as a result of developing a CIE.

CONCLUSIONS

Overall, there is an eight times higher incidence of CIEs in wearers who sleep in contact lenses compared with wearers who use lenses only during the waking hours. For those who choose to routinely or intermittently sleep in soft contact lenses, silicone hydrogels are the lens of first choice because CIEs are less clinically severe with this lens type compared with hydrogel lenses. The rate of significant visual loss as a result of developing a CIE is low.

Artisan Phakic Intraocular Lens for Correcting High Myopia

OBJECTIVES

To evaluate the safety indexes and efficacy of Artisan phakic intraocular lens (IOL) for the correction of high myopia.

METHODS

Retrospective interventional case series reports. Thirty-one eyes (22 patients) with myopia from -5.25 to -19.00 diopters underwent implantation of an Artisan phakic IOL. Follow-up examinations were performed at 1 day, 1 week, 1 month, and 3 months. The following parameters were recorded: manifest refraction, slit-lamp examination, applanation tonometry, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), complications or adverse reactions. The primary variable was the refractive outcome at 3 months. Secondary variables were change in BSCVA, and efficacy and safety indexes.

RESULTS

At 3 months, mean spherical equivalent was -0.50 +/- 0.36 diopters (range, -1.25 - plano). In 29 eyes (93.5%) UCVA was 6/12 or better; the other three eyes had UCVA of 6/15. The difference between preoperative and 1 week postoperative BSCVA was not statistically significant (p = 0.25). Comparison of BSCVA at 1 week and at 1 month was statistically significant (p = 0.05); this difference was even more significant at 3 months (p = 0.01). The BSCVA remained the same or improved for all the eyes. BSCVA for 20 eyes (64.5%) had improved one or more lines in visual acuity. Mean endothelial cell loss at 3 months was 3.96%.

CONCLUSION

The Artisan lens is a safe, predictable, and efficacious method to correct high myopia. Postoperative gain in BSCVA was achieved for the majority of eyes. Future study to assess safety indexes and risk of complications is required with long-term follow-up.

Improved Safety in Contemporary LASIK

PURPOSE

To examine the risk of serious visual loss in contemporary LASIK.

DESIGN

Retrospective, noncomparative, consecutive case series combined with a structured literature review and comparison with historical controls.

PARTICIPANTS

One thousand consecutive cases of LASIK performed from January 2000 to January 2004 by 1 surgeon. One thousand nine hundred eighty-two cases with 6-month review data in postmillennial Food and Drug Administration (FDA) trials of LASIK for myopia and astigmatism and 5203 patients with 6 month review data in similar premillennial FDA trials.

METHODS

LASIK was performed with the Hansatome microkeratome and a VISX Star (S2, S3, or S4) laser. There were 899 myopic treatments (spherical equivalent < or =-10.5 diopters [D]; average -4.2 D; standard deviations [SD] D = 1.9 D; astigmatism < or =4.75 D), 87 hyperopic treatments (spherical equivalent < or =+4.25 D; average +2.4 D; SD = 0.9 D; astigmatism < or =3.5 D), and 14 treatments for mixed astigmatism (< or =4.5 D). Outcome data were obtained from a review of case notes and compared with historical data from FDA trials.

MAIN OUTCOME MEASURES

Best-spectacle corrected visual acuity (BSCVA) preoperatively and at final review was compared in our case series with reference to the United Kingdom driving standard (BSCVA> or =20/30). Subsidiary outcome measures included duration of follow-up, intraoperative, and postoperative complication rates. Six-month postoperative data on standard safety criteria (numbers of patients losing > or =2 lines BSCVA, BSCVA <20/40, and final BSCVA <20/25 for patients with preoperative BSCVA > or =20/20) were examined in FDA trials.

RESULTS

In our clinical series, no case with a preoperative BSCVA of 20/20 or better had a final BSCVA of <20/30 at final review (97.5% confidence interval [CI], 0%-0.37%); 4 eyes had a BSCVA <20/25 (0.41%; 95%CI, 0.11%-1.02%). The median interval between surgery and final review was 2 months (range, 1-45 months). In FDA studies recruiting pre-2000, 1.4% of patients lost > or =2 lines of BSCVA versus 0.6% in postmillennial studies (P = 0.005); 0.45% of patients in premillennial studies lost BSCVA to <20/40 compared with no patients in postmillennial studies (P = 0.001); and 1.68% of patients in premillennial studies with a preoperative BSCVA > or =20/20 had a postoperative BSCVA <20/25 compared with 0.16% in postmillennial studies (P< or =0.001).

CONCLUSIONS

Compared with premillennial results, the risk of visual loss is significantly reduced in contemporary LASIK.

Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes

PURPOSE

To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.

DESIGN

Prospective, double-masked, randomized clinical trial.

PARTICIPANTS

Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.

METHODS

In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).

MAIN OUTCOME MEASURES

Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.

RESULTS

Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).

CONCLUSION

Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.

Flap lift for LASIK retreatment in eyes with myopia

PURPOSE

To analyze the results achieved with LASIK retreatment after lifting the original flap in a large series of patients.

DESIGN

Retrospective, noncomparative, interventional consecutive case series.

PARTICIPANTS

Two thousand four hundred twenty-two consecutive eyes undergoing LASIK surgery for myopia, including 334 eyes submitted to flap lift for LASIK retreatment.

MAIN OUTCOME MEASURES

Uncorrected visual acuity, best-corrected visual acuity, refractive error, and complications.

RESULTS

LASIK retreatment was performed in 334 eyes (14%), and the mean time between initial procedure and retreatment was 8.2+/-6.2 months. The mean spherical equivalent (SE) improved from -1.2+/-0.6 diopters (D) (range, -4.2 to +1.2 D) before retreatment to +0.2+/-0.4 D (range, -3.1 to +1.1 D) after the retreatment. The uncorrected visual acuity (UCVA) after retreatment was 20/20 or better in 58% and 20/40 or better in 92% of eyes. The mean SE was within +/-1.0 D in 96% of the patients and within +/-0.5 D in 80.5% after retreatment. Eighteen eyes (5%) lost 1 line of best-corrected visual acuity, and 4 eyes (1%) lost 2 lines.

CONCLUSIONS

LASIK retreatment surgery performed by relifting the flap was a useful procedure for correcting residual refractive errors after the primary LASIK procedure. It provided good uncorrected visual acuity, predictable results, good refractive stability, and few complications.

An experimental model of mycobacterial infection under corneal flaps

In order to develop a new experimental animal model of infection with Mycobacterium chelonae in keratomileusis, we conducted a double-blind prospective study on 24 adult male New Zealand rabbits. One eye of each rabbit was submitted to automatic lamellar keratotomy with the automatic corneal shaper under general anesthesia. Eyes were immunosuppressed by a single local injection of methyl prednisolone. Twelve animals were inoculated into the keratomileusis interface with 1 microl of 10(6) heat-inactivated bacteria (heat-inactivated inoculum controls) and 12 with 1 microl of 10(6) live bacteria. Trimethoprim drops (0.1%, w/v) were used as prophylaxis for the surgical procedure every 4 h (50 microl, qid). Animals were examined by 2 observers under a slit lamp on the 1st, 3rd, 5th, 7th, 11th, 16th, and 23rd postoperative days. Slit lamp photographs were taken to document clinical signs. Animals were sacrificed when corneal disease was detected and corneal samples were taken for microbiological analysis. Eleven of 12 experimental rabbits developed corneal disease, and M. chelonae could be isolated from nine rabbits. Eleven of the 12 controls receiving a heat-inactivated inoculum did not develop corneal disease. M. chelonae was not isolated from any of the control rabbits receiving a heat-inactivated inoculum, or from the healthy cornea of control rabbits. Corneal infection by M. chelonae was successfully induced in rabbits submitted to keratomileusis. To our knowledge, this is the first animal model of M. chelonae infection following corneal flaps for refractive surgery to be described in the literature and can be used for the analysis of therapeutic responses.

Hyperopic Photorefractive Keratectomy With Adjunctive Topical Mitomycin C for Refractive Error After Penetrating Keratoplasty for Keratoconus

OBJECTIVE

To present a case of photorefractive keratectomy (PRK) with adjunctive topical mitomycin C (MMC) in an anisometropic hyperopic patient after penetrating keratoplasty (PKP) for keratoconus.

METHODS

Interventional case report, chart review, and literature review.

RESULTS

A 43-year-old man with a refraction of +7.00 -4.75 x 125 in the right eye underwent PRK 10 months after PKP for keratoconus. The patient had sutures removed for 3 months and was intolerant of contact lenses. After photoablation, 0.02% MMC was applied to the corneal stromal bed. The patient was followed up daily until the epithelium closed and at 1 week, 1 month, 3 months, and 6 months postoperatively.

CONCLUSIONS

To our knowledge, this represents the first reported case of the use of MMC to prevent postoperative haze after PRK for PKP in an eye with keratoconus. MMC (0.02%) applied topically to the cornea immediately after PRK is safe and effective to treat a hyperopic refractive error after PKP and prevent postoperative corneal haze formation without the risks of performing a lamellar flap into an ectatic corneal bed.

Outcome after treatment of ametropia with implantable contact lenses

OBJECTIVE

To evaluate long-term results after insertion of implantable contact lenses (ICLs) in phakic eyes.

DESIGN

Prospective, noncomparative, interventional case series.

PARTICIPANTS

Seventy-five phakic eyes (65 myopic, 10 hyperopic eyes) of 45 patients aged 21.7 to 60.6 years were included.

INTERVENTION

STAAR Collamer Implantable Contact Lenses (STAAR Surgical Inc., Nidau, Switzerland) were implanted for correction of high myopia and hyperopia.

MAIN OUTCOME MEASURES

Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), and intraocular pressure (IOP) were determined. Presence of lens opacification and the distance between the ICL and the crystalline lens were assessed by slit-lamp examination before surgery and at 1, 3, 6 months, and yearly after lens implantation.

RESULTS

Preoperative mean spherical equivalent was -16.23+/-5.29 diopters (D) for myopic eyes and +7.88 +/-1.46 D for hyperopic eyes. After ICL implantation, mean residual refractive error was -1.77+/-2.17 D in myopic patients and +0.44+/-0.69 D in hyperopic patients. Preoperative mean UCVA was Snellen 0.03+/-0.03 for myopic patients and Snellen 0.12+/-0.16 for hyperopic patients. Preoperative mean BCVA was Snellen 0.49+/-0.23 for myopic patients and Snellen 0.82+/-0.23 for hyperopic patients. After ICL implantation, mean UCVA up to the end of individual observation time was Snellen 0.36+/-0.36 for myopic patients and Snellen 0.58+/-0.28 for hyperopic patients. Mean BCVA was Snellen 0.73+/-0.26 for myopic and Snellen 0.80+/-0.24 for hyperopic patients. Mean preoperative IOP was 14.2+/-2.7 mmHg, and mean postoperative IOP was 13.46+/-2.1 mmHg over all follow-up investigations. The main complication was the development of subcapsular anterior opacifications of the crystalline lens in 25 eyes (33.3%), 2 of which showed direct contact to the ICL. Eleven eyes (14.7%) were stable in opacification and 14 eyes (18.7%) had progressive opacifications. The median time to opacification was 27.1 months. In 8 patients (10.7%), the subjective visual impairment mandated cataract surgery.

CONCLUSIONS

The most significant long-term complication after ICL implantation is the formation of opacifications of the crystalline lens with the risk of the necessity of subsequent cataract surgery (10.7%). Old age, female gender, and contralateral opacification are independent significant risk factors for early formation of opacifications in this patient group.

Ocular Surface Management of Photorefractive Keratectomy and Laser in situ Keratomileusis

PURPOSE

To examine the effects of keratorefractive surgery and ocular surface management on goblet cell density, dry eye symptom incidence, and spherical equivalent refraction.

METHODS

We performed a retrospective analysis of four myopia groups: Untreated controls (n = 53); PRK (n = 51); LASIK without ocular surface management (n = 56); LASIK with ocular surface management (n = 140). Ocular surface management involved the routine use of non-preserved artificial tears and other lubricants before, during, and after surgery. Lid hygiene procedures, topical anti-inflammatory agents, and punctal plugs were used on indication. Assessments were conducted before and up to 12 months after surgery (right eyes only in patients with both eyes operated, and in the left or right eye in patients with one eye operated).

RESULTS

Surgery caused a significant reduction in goblet cell density, with the greatest reduction in the LASIK without ocular surface management group. No significant differences were detected in dry eye symptoms or spherical equivalent refraction between PRK and LASIK without ocular surface management. Ocular surface management significantly minimized LASIK-induced decreases in goblet cell density and was associated with significantly less myopic outcomes at months 1 to 3 and 6 to 9 after LASIK. After surgery (1 to 3 mo), dry eye symptoms were significantly lower in the LASIK with ocular surface management group. In all groups, significant inverse correlations existed between goblet cell density and dry eye symptoms.

CONCLUSIONS

Ocular surface management minimized the negative impact of LASIK on goblet cell density and reduced dry eye symptoms. Without ocular surface management, goblet cell density and dry eye symptoms after LASIK were similar to or worse than after PRK.

Pediatric refractive surgery

PURPOSE OF REVIEW

This article reviews the literature on pediatric refractive surgery from 1995 to 2003 and discusses the practical issues surrounding the application of modern refractive surgery to children.

RECENT FINDINGS

Preliminary data show that refractive surgery can be successfully performed in children and that the short term complication rate seems to be similar to that reported in adults.

SUMMARY

Refractive surgery may hold promise for cases in which traditional treatment methods have failed. Additional study is needed to define the role of refractive surgery in children and in the treatment of amblyopia and strabismus.

Technical Improvements in Photorefractive Keratectomy for Correction of High Myopia

PURPOSE

To evaluate the effects of hardware and software improvements in photorefractive keratectomy (PRK) for the treatment of highly myopic eyes.

METHODS

A retrospective study was carried out in 554 patients (582 eyes) with myopia between -7.00 and -17.00 D (mean -11.20 +/- 3.60 D) who had undergone PRK using the Aesculap Meditec laser. Group 1 with a 5-mm-diameter single ablation zone; Group 2 with a 5-mm-diameter single zone surrounded by a 2-mm tapered transitional zone; Group 3 and Group 4, same as Group 2 but with the laser upgraded with a smoke aspiration control system (Group 3), and with a computer-controlled fluence (Group 4).

RESULTS

In Group 1 at 2 years after PRK (50 eyes), 10 eyes (20%) were within +/-1.00 D of attempted correction and 13 eyes (26%) were within +/-2.00 D. In Group 2 at 2 years (118 eyes), 42 eyes (36%) were within +/-1.00 D of attempted correction and 65 eyes (55%) were within +/-2.00 D. In Group 3 at 2 years (43 eyes), 18 eyes (42%) were within +/-1.00 D of attempted correction and 28 eyes (65%) were within +/-2.00 D. In Group 4 at 2 years (47 eyes), 25 eyes (53%) were within +/-1.00 D of attempted correction and 29 eyes (62%) were within +/-2.00 D.

CONCLUSIONS

Software and hardware improvements facilitated PRK correction of high myopia with reasonable predictability, especially if a tapered transition zone was used. At 12 and 24-month follow-up, only the use of a tapered transition zone was associated with a statistically significant improvement in predictability.

Laser Epithelial Keratomileusis: Outcome of Initial Cases Performed by an Experienced Surgeon

PURPOSE

To evaluate refractive outcome and objective clinical data, and determine efficacy, predictability, and safety of laser epithelial keratomileusis (LASEK) for myopic treatments.

METHODS

We performed a retrospective non-comparative single-surgeon case series on the first 20 LASEK procedures (Alcon LADARVision 4000 laser). Mean patient age was 41.2 years (range 21 to 60 yr): 13 men and 7 women. Mean preoperative spherical equivalent refraction was -6.47+/-2.78 D. Corneal haze, uncorrected and spectacle-corrected visual acuity and manifest refraction were evaluated.

RESULTS

Of 20 eyes studied, 3 were corrected for monovision. In the non-monovision group, 20/40 or better visual acuity was achieved in 94% (16 eyes) at 1 month, 100% (13 eyes) at 3 months, and 91% (10 eyes) at 6 months after LASEK; 20/20 or better was achieved in 12% (2 eyes) at 1 month, 46% (6 eyes) at 3 months, and 45% (5 eyes) at 6 months. Corneal haze at 1 month was grade 0.5 in 35% (7 eyes), 1 in 20% (4 eyes) and 2 in 10% (2 eyes). At 3 months, 62% (12 eyes) had grade 0.5 and 31% (6 eyes) had grade 1. At 6 months, 58% (12 eyes) had grade 0.5, 25% (5 eyes) had grade 1, and 8% (2 eyes) had grade 2.

CONCLUSIONS

LASEK is a challenging procedure. Creating the epithelial flap is not simple and may have contributed to the high haze incidence in our study.

Incidence and associations of retreatment after LASIK

PURPOSE

To determine the incidence and risk factors for laser in situ keratomileusis (LASIK) retreatment and to present a novel retreatment technique.

DESIGN

Retrospective noncomparative consecutive case series.

PARTICIPANTS

Two thousand four hundred eighty-five eyes (1306 patients) underwent LASIK surgery for myopia, hyperopia, or astigmatism using either the Summit Apex Plus or the Alcon LADARVision excimer laser systems. Only retreatments for residual refractive error were included.

MAIN OUTCOME MEASURES

Prevalence and incidence of retreatments were determined. Potential risk factors for retreatment, including age, gender, and attempted correction, were assessed. Refractive error and a ratio of residual sphere to cylinder in retreated eyes were also analyzed.

RESULTS

Of the total cohort studied, 288 eyes of 233 patients underwent one retreatment, and 3 eyes of 3 patients required two retreatment procedures. The overall 1-year incidence of retreatment was 10.5%. The average length of time between initial treatment and enhancement was 7.3 +/- 6.4 months; 85% of retreatments took place within 1 year. Two hundred eighty-five of the 288 retreatments were accomplished using a manual flap lift approach; 3 eyes required a repeat microkeratome cut. Higher initial corrections and residual astigmatism were associated with a significantly higher rate of retreatment. Patients older than 40 years were at greater risk for retreatment. There was no gender difference.

CONCLUSIONS

Higher initial corrections, astigmatism, and older age are risk factors for LASIK retreatment. Most LASIK flaps can be lifted using the manual technique described up to 3 years after initial surgery.

Infectious keratitis after photorefractive keratectomy

PURPOSE

To elucidate risk factors, microbial culture results, and visual outcomes for infectious keratitis after photorefractive keratectomy (PRK).

DESIGN

Multicenter, retrospective chart review, case report, and literature review.

METHODS

The records of 12 patients with infectious keratitis after PRK were reviewed.

MAIN OUTCOME MEASURES

Causative organism, response to medical treatment, and visual outcome.

RESULTS

Infectious keratitis developed in 13 eyes of 12 patients after PRK. Organisms cultured were Staphylococcus aureus (n = 5), including a bilateral case of methicillin-resistant Staphylococcus aureus; Staphylococcus epidermidis (n = 4); Streptococcus pneumoniae (n = 3); and Streptococcus viridans (n = 1). Four patients manipulated their contact lenses, and 2 patients were exposed to nosocomial organisms while working in a hospital environment. Prophylactic antibiotics used were tobramycin (nine cases), polymyxin B-trimethoprim (three cases), and ciprofloxacin (one case). Final best spectacle-corrected visual acuity ranged from 20/20 to 20/100.

CONCLUSIONS

Infectious corneal ulceration is a serious potential complication of PRK. Gram-positive organisms are the most common pathogens. Antibiotic prophylaxis should be broad spectrum and should include gram-positive coverage.

Laser in situ keratomileusis flap stability during simulated aircraft ejection in a rabbit model

PURPOSE

To determine the stability of the laser in situ keratomileusis (LASIK) flap in a rabbit model when subjected to vertical acceleration at nine times the force of gravity (+9 Gz) in an aircraft cockpit ejection simulator.

METHODS

Thirty-six eyes from 25 New Zealand white rabbits underwent LASIK flap creation without laser photoablation. One month after surgery, the rabbits were sedated and harnessed in a cockpit ejection seat simulator used to train United States Air Force pilots. They then underwent a controlled rapid-sequence ejection at +9 Gz. Subsequently, the rabbits were euthanized and the corneas harvested for microscopic examination. Refractive measurements and corneal examination were made before LASIK flap creation and prior to and after the +9 Gz ejections. Determination of LASIK flap dislocation was based on clinical observation of flap slippage or a significant shift in pre-ejection to postejection cylinder axis.

RESULTS

The average preoperative refraction of the rabbit eye was +1.83 D + 3.25 D x 086 degrees. The average change from pre-ejection to postejection was 0.04 D sphere, 0.02 D cylinder, 6.8 axis degrees, and 0.04 D spherical equivalent. The pre-ejection to postejection measurements were not statistically significantly different by a paired test. Laser in situ keratomileusis flap dislocation or ejection-induced corneal folds or striae were not clinically observed. Histologic examination revealed well-healed LASIK flaps but no reactive keratocytes at the central stromal-stromal interface.

CONCLUSIONS

Healed LASIK flaps as created in this rabbit model without laser ablation are stable when subjected to a rapid vertical ejection at nine times the force of gravity.

LASIK vs LASEK vs PRK: advantages and indications

The advent of the excimer laser as an instrument for use in reshaping the corneal stroma was a great step forward in refractive surgery. Laser energy can be delivered on the stromal surface in the photorefractive keratectomy (PRK) procedure or deeper on the corneal stroma by the means of a lamellar surgery in which a flap is created with the microkeratome in the laser in situ keratomileusis (LASIK) procedure. LASIK is currently the dominant procedure in refractive surgery. The main advantage of LASIK over PRK is related to maintaining the central corneal epithelium. This increases comfort during the early post-operative period, allows for rapid visual recovery, and reduces the wound healing response. Reduced wound healing correlates with less regression for high corrections and a lower rate of complications such as significant stromal opacity (haze). PRK, however, remains as an excellent option for mild to moderate corrections, particularly for cases associated with thin corneas, recurrent erosions, or a predisposition for trauma (Martial arts, military, etc.). Recently, a modification of PRK, laser subepithelial keratomileusis (LASEK), was introduced. In the LASEK procedure, an epithelial flap is created and replaced after the ablation. The benefits, if any, of the creation of an epithelial flap compared to traditional PRK are not fully appreciated. Advocates of LASEK suggest that there is less discomfort in the early postoperative period, faster visual recovery, and less haze compared to standard PRK for correction of similar levels of refractive error. Additional long-term clinical studies, along with laboratory research, will be crucial to validate these potential advantages of LASEK procedure.