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

Removal of INTACS for myopia

OBJECTIVE

To evaluate the safety and efficacy of the removal of INTACS.

DESIGN

Subgroup analysis from a nonrandomized comparative interventional trial.

PARTICIPANTS

Four hundred fifty-two patients with best spectacle-corrected visual acuity of 20/20 or better and myopia (1.0-3.5 diopters [D]) were enrolled in the U.S. Food and Drug Administration clinical trials of INTACS. Forty-six eyes among a total of 684 underwent INTACS removal.

INTERVENTION

INTACS removal.

METHODS

Safety and efficacy of INTACS removal was assessed by comparison of results from preoperative and 3-month postremoval visits. Safety was assessed by maintenance of preoperative best spectacle-corrected acuity and induction of astigmatism (measured by manifest refraction). Efficacy was assessed by comparison of mean spherical equivalent measured by both manifest and cycloplegic refraction, as well as percentage of eyes within +/- 0.5 D and +/- 1.0 D of baseline values. A subset of 27 patients completed a prospective questionnaire assessing the frequency of six visual symptoms (glare, halos, double vision, photophobia, night vision difficulties, and fluctuating vision).

MAIN OUTCOMES MEASURES

Best spectacle-corrected visual acuity, manifest refraction, and cycloplegic refraction.

RESULTS

Forty-one of 46 patients' eyes that had undergone INTACS removal had reached the 3-month postremoval visit. Of these eyes, 73% (30 of 41) had returned to within +/- 0.5 D and 97% (40 of 41) to within +/- 1.0 D of baseline spherical equivalent as measured by manifest refraction. With respect to astigmatism, 88% (36 of 41) had returned to within +/- 0.5 D and 100% (41 of 41) to within +/- 1.0 D of preoperative value. No patient had a loss of best spectacle-corrected acuity of more than 2 lines, with equal numbers of eyes having a loss or gain of 1 line (nine eyes) and 2 lines (one eye). For most eyes, INTACS removal was associated with a substantial reduction in the six types of visual symptoms; however, in some eyes (up to 15%) symptoms that had not been detected preoperatively were noted after INTACS removal.

CONCLUSIONS

INTACS removal was not associated with a loss (> 2 lines) of best spectacle-corrected visual acuity or induction (> 1 D) of astigmatism or myopia. INTACS removal was associated with a reversal to preoperative values in most cases.

Changes of posterior corneal astigmatism and tilt after myopic laser in situ keratomileusis

PURPOSE

The purpose of this study was to assess the changes of posterior corneal astigmatism and tilt after laser in situ keratomileusis (LASIK) and to correlate these changes with the amount of correction and the residual stromal bed thickness.

METHODS

This prospective nonrandomized (self-controlled) comparative trial included 57 eyes from 14 females and 15 males, whose mean age (+/- standard deviation [SD]) at the time of surgery was 33 +/- 9 years (range, 19-53), with a spherical equivalent (SEQ) of -1.00 to -15.50 (mean, -5.07 +/- 2.81) diopters (D). All LASIK procedures were accomplished with the Keratom II Coherent-Schwind excimer laser and the Moria Model One microkeratome (150-microm head). Subjective refractometry, Orbscan slit-scanning corneal topography analysis, and pachymetry were performed before and 3 months after LASIK for myopia (n= 35; -1.00 to -15.50 D [mean, -4.75 +/- 3.07]) or myopic astigmatism (n= 22; sphere, 0.00 to -9.75 D [mean, -4.75 +/- 2.36]; cylinder, -0.75 to -3.50 D [-1.68 +/- 0.86]). Intended ablation depth ranged from 12 to 108 (mean, 48 +/- 22) microm. Topographic raw data were decomposed into a set of Zernike polynomials as published in detail previously, and parameters for detection of asymmetric mechanical deformation of the cornea were derived. Posterior corneal astigmatism and tilt before and after LASIK were compared, and changes in these variables were correlated with the SEQ change (DeltaSEQ) and the residual corneal bed thickness (RBT).

RESULTS

The RBT after LASIK ranged from 186 to 373 (mean, 280 +/- 42) microm. Overall, astigmatism (0.19 +/- 0.07 D/0.22 +/- 0.13 D; p= 0.80) and tilt (3.58 +/- 0.35 degrees /3.65 +/- 0.48 degrees; p= 0.61) did not change significantly by 3 months after LASIK. In eyes with RBT < or =250 microm, the average change in astigmatism (0.05 +/- 0.11 versus 0.01 +/- 0.13 D; p= 0.46) and tilt (0.21 +/- 0.45 degrees versus 0.04 +/- 0.55 degrees; p= 0.30) was not greater than in eyes with RBT > 250 microm. Change in astigmatism (p= 0.19) and tilt (p= 0.56) did not correlate with the RBT during LASIK.

CONCLUSIONS

Zernike decomposition of topographic height data discloses that no significant asymmetric mechanical deformation of the posterior corneal curvature occurs after myopic LASIK. Further studies with long-term follow-up are needed to clarify whether this symmetry of the posterior corneal surface can indeed be preserved over time after LASIK if the RBT is < 250 microm.

Comparison of Laser in situ Keratomileusis Outcomes With the Nidek EC-5000 and Meditec Mel 70 Excimer Lasers

PURPOSE

To report refractive outcomes of laser in situ keratomileusis (LASIK) for myopia with and without astigmatism using the Nidek EC-5000 and Meditec Mel 70 excimer laser systems.

METHODS

A retrospective analysis of refractive outcomes with each laser was conducted. Approximately 5700 eyes treated for myopia and myopic astigmatism were analyzed. Preoperative sphere ranged from -0.25 to -15.50 D and cylinder ranged from -0.75 to -5.50 D. All statistical analyses were performed by Datagraph med version 2.8 refractive analysis software.

RESULTS

With the Nidek EC-5000 at 6 months after LASIK, mean spherical equivalent refraction was -0.24 D with 72% of eyes within +/- 0.50 D. In the Meditec cohort, the mean spherical equivalent was -0.54 D with 55% of eyes +/- 0.50 D.

CONCLUSION

Eyes treated for myopia and astigmatism with either of these lasers showed early refractive stability and similar efficacy. Higher incidences of epithelial ingrowth and haze were present in the Meditec treated eyes.

Is Abnormal Focal Steepening of the Cornea Related to Persistent Monocular Diplopia?

PURPOSE

Some case reports have shown that abnormal focal steepening of the cornea appears to cause monocular diplopia by prismatic effect. The purpose of this study was to ascertain prospectively if the pattern of corneal distortion was related specifically to persistent monocular diplopia.

METHODS

We selected 16 visually normal eyes (controls) and two groups of volunteers in which abnormal focal steepening of the cornea was expected to be found: 40 eyes of 20 volunteers who wore rigid gas-permeable contact lenses (RGP) for myopia and 10 eyes of seven patients with keratoconus. New charts that consisted of white dials on a black background were prepared for detection and measurement of secondary images. Any secondary image that could not be eliminated by any trial lens correction was defined as a persistent secondary image, using the charts. Corneal topography from all subjects was classified: round or oval, symmetric or asymmetric bowtie, abnormal focal steepening accompanied by contact lens-induced corneal warpage or keratoconus, or amorphous. We analyzed the relationship between the persistent secondary image and the corneal topographical patterns.

RESULTS

A persistent secondary image was detected from seven eyes of RGP wearers and all keratoconus eyes. All corneal topographies of the seven RGP eyes with a persistent secondary image showed abnormal focal steepening related to contact lens-induced corneal warpage. The direction of the persistent secondary image was approximately consistent with the location of the focal steepening as seen on the corneal topography.

CONCLUSION

Abnormal focal steepening of the cornea that appeared to produce a prismatic difference between two parts of the cornea was specifically related to persistent monocular diplopia.

Laser Epithelial Keratomileusis for Myopia With the Autonomous Laser

PURPOSE

To describe the refractive outcome, objective clinical data, and subjective patient experiences after laser epithelial keratomileusis (LASEK) at 1, 3, and 6 months after surgery.

METHODS

This was a retrospective, nonrandomized, comparative study of 58 LASEK-treated eyes (36 patients) with myopia (with and without astigmatism) between -1.50 and -14.75 D (mean -7.80 +/- 2.90 D, median -7.90 D). Refractive surgery was performed using the Alcon Summit Autonomous LADAR Vision excimer laser. Manifest refraction, best-spectacle and uncorrected Snellen visual acuity, stability of refraction, and corneal haze were evaluated before surgery and up to 6 months after surgery. A group of randomly selected LASIK-treated eyes were compared at each time point.

RESULTS

Patients who opted for monovision (n=12) were excluded. In the emmetropia targeted eyes (n=46), 45%, 83%, 85%, and 89% achieved 20/40 or better uncorrected Snellen visual acuity (UCVA) at 1 day, 1 week, 2 weeks, and 1 month respectively. At 6 months, 73% (n=28) of eyes treated achieved UCVA 20/20 with 97% achieving 20/40 or better (mean, -0.51 D). At 3 and 6 months, 71% (n=46) and 68% (n=28) were within +/- 0.50 D of emmetropia. The percentage of eyes that achieved UCVA 20/40 or better at 6 months was 97% (n=28). Visually significant corneal haze was evident in two LASEK-treated patients (four eyes) at 6 months. No eyes lost two or more lines of best spectacle-corrected Snellen visual acuity.

CONCLUSIONS

Preliminary data suggest that LASEK appears to be a safe, effective, and comparable alternative to LASIK, even for higher amounts of myopia. A prospective, randomized clinical trial is needed to better define the role of LASEK as it compares to other refractive procedures, specifically LASIK and PRK.

Comparison of photorefractive keratectomy, astigmatic PRK, laser in situ keratomileusis, and astigmatic LASIK in the treatment of myopia

PURPOSE

To determine factors affecting refractive and visual outcomes in patients treated with astigmatic and spherical photorefractive keratectomy (A-PRK and PRK) and laser in situ keratomileusis (A-LASIK and LASIK).

SETTING

University referral refractive surgery clinic.

METHODS

Refractive and visual acuity results in 619 eyes of 388 consecutive patients having refractive surgery over a 2-year period by a single surgeon were retrospectively analyzed. Patients were divided into mild-to-moderate myopia (spherical equivalent [SE] less than -6.12 diopters [D]) and high myopia (SE -6.12 D or higher). Multivariate and logistic regression analyses were performed.

RESULTS

Refractive results in flap-based and PRK-based procedures were comparable in mild-to-moderate myopia patients but were significantly better in high-myopia patients having flap-based procedures. Refractive stability was greater in flap-based procedures than in PRK-based procedures. Elliptical ablations yielded a marked reduction in the astigmatic cylinder in patients having A-LASIK and A-PRK, while spherical PRK induced small amounts of with-the-rule astigmatism. Complications were uncommon in both groups, consisting primarily of epithelial ingrowth in flap-based procedures and haze in PRK-based procedures. Multivariate regression identified the preoperative SE as a significant determinant of PRK outcomes (with higher success for lower myopia) and intraocular pressure as a minor determinant of outcomes in PRK-based and flap-based procedures. Logistic regression suggested that only the preoperative SE was a significant factor in predicting the likelihood of poor outcomes in PRK patients.

CONCLUSIONS

Refractive outcomes were almost identical in patients having elliptical or spherical ablations with flap-based or PRK-based procedures. In eyes with mild-to-moderate myopia, there was little difference in refractive or visual outcomes between flap-based and PRK-based procedures; in eyes with high myopia, flap-based procedures offered more predictable refractive outcomes and better visual outcomes.

Prospective Randomized Study of Corneal Aberrations 1 Year After Radial Keratotomy or Photorefractive Keratectomy

PURPOSE

To evaluate the optical properties of the cornea 1 year after either radial keratotomy (RK) or photorefractive keratectomy (PRK) in a randomized group of patients with low myopia.

METHODS

Ninety-six patients with myopia between -0.75 and -5.00 D were randomized to either radial keratotomy (n = 46) or photorefractive keratectomy (n = 50). Topography maps were obtained 1 year after surgery and analyzed by computation of total corneal wavefront aberration and Zernike polynomial coefficients for pupil sizes of 2, 4, and 6 mm. The 4-mm pupil size was used for optimization of the model.

RESULTS

The total corneal wavefront aberrations after RK and PRK were similar and not statistically different. Wavefront aberrations arising from astigmatism or defocus accounted for approximately 70% of the total wavefront error at all pupil sizes in both groups. All types of aberrations, and in particular spherical aberration, increased significantly with increasing pupil size. Higher-order wavefront aberrations were almost twice as high after RK than after PRK at pupil sizes of 4 and 6 mm. Spherical aberration and coma were slightly higher after PRK than after RK.

CONCLUSIONS

Pupil size had a major effect on corneal aberrations after RK and PRK. The most important aberrations were sphero-cylindrical, in which eyes became significantly more myopic with increasing pupil size. The image forming properties of the cornea are better after PRK compared with RK due to the lesser amount of higher-order aberrations.

Laser in situ keratomileusis for myopia and astigmatism: safety and efficacy: a report by the American Academy of Ophthalmology

OBJECTIVE

This document describes laser in situ keratomileusis (LASIK) for myopia and astigmatism and examines the evidence to answer key questions about the efficacy and safety of the procedure.

METHODS

A literature search conducted for the years 1968 to 2000 retrieved 486 citations and an update search conducted in June 2001 yielded an additional 243 articles. The panel members reviewed 160 of these articles and selected 47 for the panel methodologist to review and rate according to the strength of evidence. A Level I rating is assigned to properly conducted, well-designed, randomized clinical trials; a Level II rating is assigned to well-designed cohort and case-control studies; and a Level III rating is assigned to case series and poorly designed prospective and retrospective studies, including case-control studies.

RESULTS

The assessment describes randomized controlled trials published in 1997 or later (Level I evidence) and more recent comparative and noncomparative case series (Level II and Level III evidence), focusing on results for safety and effectiveness. It is difficult to extrapolate results from these studies that are comparable to current practices with the most recent generation lasers because of the rapid evolution of LASIK technology and techniques. It is also difficult to compare studies because of variations in the range of preoperative myopia, follow-up periods, lasers, nomograms, microkeratomes and techniques, the time frame of the study, and the investigators' experience.

CONCLUSIONS

For low to moderate myopia, results from studies in the literature have shown that LASIK is effective and predictable in terms of obtaining very good to excellent uncorrected visual acuity and that it is safe in terms of minimal loss of visual acuity. For moderate to high myopia (>6.0 D), the results are more variable, given the wide range of preoperative myopia. The results are similar for treated eyes with mild to moderate degrees of astigmatism (<2.0 D). Serious adverse complications leading to significant permanent visual loss such as infections and corneal ectasia probably occur rarely in LASIK procedures; however, side effects such as dry eyes, night time starbursts, and reduced contrast sensitivity occur relatively frequently. There were insufficient data in prospective, comparative trials to describe the relative advantages and disadvantages of different lasers or nomograms.

The role of ultraviolet-B in corneal healing following excimer laser in situ keratomileusis

Corneal photoablation with the 193 nm argon fluoride excimer laser during photorefractive keratectomy (PRK) in high diopter range is frequently associated with subepithelial haze and consequent refractive regression due to avascular corneal wound healing. The wound healing response can be augmented by Ultraviolet-B (UV-B) exposure originating from sun or solarium. Clinically Laser in situ Keratomileusis (LASIK) even in high diopter range is associated with less subepithelial haze and regression than PRK. In an animal model, the morphologic changes of the rabbit cornea were evaluated following LASIK and secondary UV-B exposure. Light microscpic changes were found to be insignificant. Transmission electron microscopy (TEM) normal epithelium, epithelial adhesion structures and normal anterior stroma showed in the LASIK treated UV-B irradiated rabbit eyes. Around the peripheral LASIK cut, migrating keratocytes with pseudopodia were observed. Under the flap (160 microm depth) the overall stromal collagen structure was normal, some activated keratocytes and mild extracellular matrix formation within and around keratocytes were noted. Within activated keratocytes TEM showed prominent rough endoplasmic reticulum, Golgi apparatus, mitochondria and extracellular vacuoles, which showed resolution with time. These changes were much milder than in PRK treated-UV-B irradiated eyes. Secondary UV-B caused no long-term disturbance in corneal transparency in LASIK and UV-B treated rabbit eyes.

Iris-claw Phakic Intraocular Lens for High Myopia

PURPOSE

To evaluate the efficacy, safety, predictability, and stability of implanting a polymethylmethacrylate (PMMA) phakic intraocular lens (PIOL) (the Artisan myopia lens) to correct high myopia.

METHODS

An Artisan myopia lens was implanted in 78 consecutive eyes of 49 patients with preoperative myopia that ranged from -6.25 to -28.00 D. Mean patient age was 42.4 years. Mean follow-up was 10.7 months and all patients were followed for at least 6 months; 45 eyes had follow-up of 12 months, and 10 eyes had 24 months. The desired outcome was emmetropia in all eyes except for those eyes with preoperative myopia greater then -23.00 D.

RESULTS

Fifty-three eyes (67.9%) had a postoperative refraction at the last follow-up examination within +/-1.00 D of emmetropia, and 39 eyes (50.0%) had a postoperative refraction +/- within 0.50 D of emmetropia. The postoperative refraction remained stable during the entire follow-up period. Mean spectacle-corrected visual acuity improved from 20/32 preoperatively to 20/25 postoperatively. Mean postoperative uncorrected visual acuity was 20/32. There was no significant change in endothelial cell density from baseline. We did not encounter major complications.

CONCLUSION

Implantation of the Artisan myopia lens to correct high myopia resulted in a stable and fairly predictable refractive outcome. A significant endothelial cell change was not detected.

Evaluation of corneal stromal changes in vivo after laser in situ keratomileusis with confocal microscopy

PURPOSE

To assess by in vivo confocal microscopy the modifications of the corneal stroma after laser in situ keratomileusis (LASIK) for myopia.

DESIGN

Nonrandomized comparative (self-controlled) trial.

PARTICIPANTS

Sixteen eyes of 13 patients were examined before surgery and at days 8, 30, and 90, and 9 eyes were examined at 6 months postoperatively using an in vivo confocal microscope. TESTING/INTERVENTION: Stromal morphologic changes, keratocyte density, flap thickness, and subclinical haze were evaluated and compared at different time points. LASIK was performed with a Flapmaker microkeratome (Solan Ophthalmic products, Jacksonville, FL) and a Lasersight LSX excimer laser (LaserSight Technologies Inc., Winter Park, FL).

MAIN OUTCOME MEASURE

Confocal microscopy results.

RESULTS

Microfolds at the Bowman's layer were found in most eyes, as well as variable reflectivity particles (pa) located at the interface level in all eyes examined postoperatively. The density of these particles significantly decreased with time with, respectively, 504 +/- 101 pa/mm2 at day 8 and 380 +/- 111 pa/mm2 at day 30 (P = 0.003), 332 +/- 100 pa/mm2 at month 3 and 312 +/- 40 pa/mm2 at month 6. The mean flap and the activated-cells area thicknesses were, respectively, 102 +/- 26 microm and 61 +/- 19 microm and showed significant negative correlation (P < 0.0001). The intensity of the added peak (47.3 microm 8.6%), corresponding to the subclinical haze, realized by Z-scan measure, was also negatively correlated with flap thickness (P = 0.01). Keratocyte (k) density quantified in the posterior stroma significantly increased from day 0 (480 +/- 67 k/mm2) to day 8 (701 +/- 41 k/mm2, P < 0.0001 compared with day 0) and day 30 (917 +/- 143 k/mm2, P = 0.0006, compared with day 0) but significantly decreased at 3 months postoperatively (597 +/- 56 k/mm2, P < 0.0001 compared with day 30) to reach the initial level at month 6 (502 +/- 41 k/mm2, nonsignificant compared with day 0). There was no correlation between preoperative or postoperative spherical equivalent and the density of particles, keratocytes, and the haze intensity.

CONCLUSIONS

This study confirms the presence of microfolds and particles at the interface level, as well as subclinical impairment. Evaluation of keratocyte density constitutes a major contribution of confocal microscopy toward an understanding of the keratocyte response to corneal wound healing after corneal refractive surgery. Moreover, flap thickness seems to be involved in the postoperative cellular activation with a higher response when thin.

Laser in situ keratomileusis for residual myopia after radial keratotomy and photorefractive keratectomy

PURPOSE

To evaluate the visual outcome, stability, and complications of laser in situ keratomileusis (LASIK) for residual myopia after radial keratotomy (RK) and photorefractive keratectomy (PRK).

SETTING

Dr. Agarwal's Eye Hospital, Chennai, India.

METHODS

Twenty eyes that had LASIK treatment for residual myopia after RK (10 eyes) or PRK (10 eyes) were retrospectively analyzed. Laser in situ keratomileusis was performed after a mean period of 24.3 months +/- 0.75 (SD) in the RK group and 22.0 +/- 1.07 months in the PRK group.

RESULTS

At the last follow-up, the mean spherical equivalent was reduced from -6.05 +/- 1.98 diopters (D) to -1.26 +/- 0.32 D (P <.05) in the RK group and from -3.38 +/- 1.30 D to -0.55 +/- 0.40 D (P <.005) in the PRK group. The mean uncorrected visual acuity improved from 20/300 (range 20/600 to 20/200) to 20/40 (range 20/60 to 20/20) (P <.05) and from 20/200 (range 20/800 to 20/80) to 20/25 (range 20/40 to 20/20) (P <.05), respectively. Two eyes in the RK group and 3 in the PRK group gained 1 line of best corrected visual acuity, and 2 eyes in the RK group lost 1 line. No sight-threatening complications such as a free flap, corneal ectasia, or a retinal complication occurred. There was no statistically significant difference in corneal haze before and after LASIK. Two eyes in the RK group required repositioning of the flap because of irregular apposition to the stromal bed.

CONCLUSION

Laser in situ keratomileusis was safe, effective, and stable in the treatment of residual myopia after RK and PRK.

Late natural history of corneal topography after excimer laser photorefractive keratectomy

PURPOSE

To investigate the 3 month to 1 year natural history of corneal topography after excimer laser photorefractive keratectomy (PRK).

DESIGN

A prospective, multicenter, nonrandomized comparative study.

PARTICIPANTS

A total of 75 eyes of 68 patients with myopia were studied.

INTERVENTION

Excimer laser photorefractive keratectomy and computer-assisted videokeratography were performed.

MAIN OUTCOME MEASURES

Preoperative and 3, 6, and 12 month postoperative topography patterns were compared and changes assessed by averaging defined sectors of the ablation zone in individual maps to produce composite "average" topography maps.

RESULTS

Corneal topography was relatively smooth 3 months after PRK. By 12 months, the corneal contour in general had become even more uniform. No "central island" effect was observed. When looking at right and left eyes independently, there was a tendency toward maximum flattening nasally.

CONCLUSIONS

Corneal topography in general continues to smooth from 3 to 12 months after PRK, possibly as a result of epithelial and stromal healing and remodeling. Right and left eyes on average show mirror-image, spatially oriented topography patterns.

Comparison of laser epithelial keratomileusis and photorefractive keratectomy for low to moderate myopia

PURPOSE

To compare the effectiveness, safety, and stability of laser epithelial keratomileusis (LASEK), a modified photorefractive keratectomy (PRK) technique, with those of conventional PRK for low to moderate myopia.

SETTING

Department of Ophthalmology, Yonsei University School of Medicine, Seoul, Korea.

METHODS

In this prospective study, 27 patients with a manifest refraction of -3.00 to -6.50 diopters were treated and followed for 3 months. In each case, PRK was performed in 1 eye and LASEK in the other eye. The first eye treated and the surgical method used in the first eye were randomized. Postoperative pain, epithelial healing time, uncorrected visual acuity (UCVA), manifest refraction, corneal haze, and surgical preference were examined in PRK- and LASEK-treated eyes.

RESULTS

During the 3 month follow-up, there were no significant between-eye differences in epithelial healing time, UCVA, or refractive error. However, LASEK-treated eyes had lower postoperative pain scores (P =.047) and corneal haze scores (1 month; P =.02) than PRK-treated eyes. Seventeen patients (63%) preferred the LASEK procedure.

CONCLUSIONS

Laser epithelial keratomileusis safely and effectively treated eyes with low to moderate myopia. It reduced the incidence of significant postoperative pain and corneal haze and may prevent the flap- and interface-related problems of laser in situ keratomileusis.

Effect of brimonidine tartrate ophthalmic solution 0.2% on pupil size in normal eyes under different luminance conditions

PURPOSE

To evaluate the effect of brimonidine tartrate ophthalmic solution 0.2% (Alphagan) on pupil size in normal eyes. Three luminance conditions were used to assess the potential use of brimonidine in postoperative refractive patients who experience nighttime vision problems related to large pupil size.

SETTING

McDonald Eye Associates, Fayetteville, Arkansas, USA.

METHODS

Pupil size was measured in 16 eyes of 16 participants with the Colvard pupillometer under 3 luminance conditions. One drop of brimonidine 0.2% was administered to each patient. Pupil size was then measured using the same technique 30 minutes and 4 and 6 hours after drop administration.

RESULTS

Under scotopic conditions, 100% of the pupils showed significant miosis at 30 minutes (P <.05). The effect continued in all eyes for 4 hours. At 6 hours, a miotic effect was still present in 81.3%. However, under photopic luminance, there was no significant effect on pupil size in all 16 eyes (P >.05). The pupil size in 5 eyes (31.2%) was not affected at 30 minutes or 4 or 6 hours. At 6 hours, 15 eyes (93.8%) had returned to their preinstillation size.

CONCLUSION

Brimonidine tartrate 0.2% had a significant effect in decreasing pupil size under scotopic conditions. The results indicate that the drug can decrease night-vision difficulties such as halos, star bursts, glare, and monocular diplopia in postoperative refractive patients.

Posterior corneal curvature changes after myopic laser in situ keratomileusis

OBJECTIVE

To assess the posterior corneal power and asphericity changes after myopic laser in situ keratomileusis (LASIK) and to correlate these changes with the amount of correction and the residual stromal bed thickness.

DESIGN

Prospective nonrandomized (self-controlled) comparative study.

PARTICIPANTS

Fifty-seven eyes of 14 women and 15 men, mean age at the time of surgery 33 +/- 9 (range, 19-53) years with a spherical equivalent (SEQ) of -1.00 to -15.50 (mean, -5.07 +/- 2.81) diopters (DI).

INTERVENTION

All procedures were performed with the Keratom II Coherent-Schwind excimer laser and and the Moria Model One microkeratome (150-microm head). Subjective refractometry, Orbscan slit scanning corneal topography analysis and pachymetry were performed before and 3 months after LASIK for myopia (n=35, -1.00 to -15.50 D, mean -4.75 +/- -3.07 D) or myopic astigmatism (n=22, sphere 0.00 to -9.75 D, mean -4.75 +/- 2.36 D; cylinder -0.75 to -3.50 D, mean -1.68 +/- 0.86 D). Intended ablation depth ranged from 12 to 108 (mean, 48 +/- 22) microm. Topographic raw data were decomposed into a set of Zernike polynomials as published in detail previously, and parameters potentially indicative for detection of a "mild keratectasia" were derived.

MAIN OUTCOME MEASURES

Posterior central corneal power and asphericity before and after LASIK were compared, and changes of these variables were correlated with the SEQ change (deltaSEQ)and the residual corneal bed thickness RBT).

RESULTS

The mean RBT after LASIK was 280 +/- 42 microm. Overall, change of posterior power (-6.28 +/- 0.22 D/ -6.39 +/- 0.23 D, P=0.02) was statistically significant and change of asphericity (0.98 +/-0.07/1.14 +/- -.20, P<0.0001) was highly significant. In eyes with RBT < or =250 microm, the average change of posterior central power (-0.20 +/- 0.10 D vs. -0.08 +/- 0.18 D) was significantly greater than in eyes with RBT >250 microm (P=0.003). The change of posterior corneal power correlated significantly with deltaSEQ (P=0.004) and the RBT (P=0.002).

CONCLUSIONS

Increased negative keratometric diopters and oblate asphericity of the posterior corneal curvature suggest that mild "keratectesia" of the cornea may be common early after LASIK. Further stuudies with longer follow-up are required to clarify whether this biomechanical deformation is progressive and whether a residual bed thickness of >250 microm can completely prevent it.

Comparison of Laser in situ Keratomileusis Outcomes With the Nidek EC-5000 and LSX LaserSight Excimer Lasers

PURPOSE

To report the results of laser in situ keratomileusis (LASIK) for myopia with and without astigmatism using the Nidek EC-5000 and LaserSight LSX excimer laser systems.

METHODS

A retrospective analysis of refractive outcomes with each laser was conducted. Approximately 2,900 myopic and astigmatic treatments up to -10.00 D (spherical equivalent refraction) were analyzed using refractive outcomes analysis software.

RESULTS

At 6 months postoperatively, 78% of patients treated with the Nidek EC-5000 laser and 53% of patients treated with the LaserSight LSX laser were within +/-0.50 D of the intended correction.

CONCLUSION

A difference in safety, stability, and efficacy of LASIK was found that favored the Nidek EC-5000 excimer laser.

Hyperopic laser in situ keratomileusis to treat overcorrected myopic LASIK

PURPOSE

To evaluate the safety and efficacy of hyperopic laser in situ keratomileusis (LASIK) in treating hyperopia caused by overcorrected myopic LASIK and to evaluate a new technique to place the hyperopic treatment after lifting the initial myopic flap.

SETTING

Open-access outpatient excimer laser surgical facility.

METHODS

A retrospective analysis was performed of 54 eyes in 47 patients who had spherical hyperopic LASIK by 21 surgeons for the treatment of significant hyperopia after overcorrected LASIK for myopia. In 42 eyes, the initial LASIK flaps were lifted and in 12 eyes, new flaps were cut. The mean age of the 25 men (53%) and 22 women (47%) was 48.2 years +/- 8.4 (SD). Outcome measures included refractive error, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), and complications. The mean follow-up was 2.97 months.

RESULTS

In eyes in which postoperative emmetropia was attempted (n = 45), the mean spherical equivalent improved from +1.21 +/- 0.49 diopters (D) preoperatively to -0.38 +/- 0.50 D postoperatively (P <.001). The mean UCVA improved from 20/38.6 +/- 16.3 to 20/27.4 +/- 9.4 (P <.001). At the last follow-up, 69% of eyes were within +/-0.5 D and 96% were within +/-1.0 D of emmetropia; 42% had a UCVA of 20/20 and 96% had a UCVA of 20/40 or better. No eyes lost 2 or more lines of BSCVA. No vision-threatening complications occurred. Results in patients who had initial flaps lifted and those who had new flaps cut were statistically indistinguishable. On average, achieved hyperopic corrections were 18% greater than intended.

CONCLUSION

Hyperopic LASIK was safe, predictable, and effective in the treatment of hyperopia caused by overcorrected myopic LASIK. Results were similar whether the original flap was lifted or a new one was cut.

Comparison of Laser in situ Keratomileusis and Photorefractive Keratectomy for the Correction of Myopia of -6.00 Diopters or Less

PURPOSE

To evaluate the safety and efficacy of laser in situ keratomileusis (LASIK) compared to photorefractive keratectomy (PRK) for the correction of low or moderate myopia (-0.50 to -6.00 D) at 6 months after surgery.

METHODS

The study population comprised a non-randomized consecutive series of 622 eyes of 392 patients who were treated with the Nidek EC-5000 excimer laser. LASIK was performed using the ACS Chiron microkeratome on 314 eyes and surface PRK on 308 eyes. All patients were treated using a standard protocol, then assessed at 1, 3, and 6 months postoperatively.

RESULTS

Forty-four percent of the LASIK group and 67% of the PRK group attended their 6-month examination. Eighty percent of patients (111 eyes) after LASIK and 65% (136 eyes) after PRK had an uncorrected visual acuity of 20/20 or better. Spherical equivalent refraction was within +/-0.50 D of intended refraction in 78% (109 eyes) for LASIK and 82% (170 eyes) for PRK. Loss of two more lines of best spectacle-corrected visual acuity at 6 months occurred in 1.4% (2 eyes) of the LASIK group and 1.0% (2 eyes) of the PRK group.

CONCLUSION

At 1 month follow-up, the percentage of eyes that achieved 20/20 uncorrected visual acuity was greater in the LASIK group than in the PRK group. At 6 months, visual and refractive outcomes of LASIK and PRK were similar. Although flap related complications occurred only after LASIK, the overall risk of loss of best spectacle-corrected visual acuity was not significantly greater than for PRK.

Outcome of corneal and laser astigmatic axis alignment in photoastigmatic refractive keratectomy

PURPOSE

To compare the refractive results of laser astigmatic treatment in eyes in which the astigmatic axes of the eye and laser are aligned by limbal marking at the 6 o'clock position and in eyes that are not marked.

SETTING

University Hospital and Clinics, Madison, Wisconsin, USA.

METHODS

This retrospective study comprised 143 eyes that had photoastigmatic refractive keratectomy with the VISX Star excimer laser. The eyes were divided into marked (G1) and unmarked (G2) groups. Based on the preoperative astigmatism, each group was subdivided into low astigmatism (</=1.00 diopter [D]) and high astigmatism (>/=1.25 D). Early postoperative manifest refractions (1.0 to 2.5 months) were analyzed. The Alpins vector analysis method was used to calculate the target induced astigmatism, surgically induced astigmatism, difference vector (DV), magnitude of error (ME), angle of error (AE), and index of success (IS).

RESULTS

There was no significant difference between the groups in DV, ME, and IS. When the subgroups were analyzed, the DV and ME were comparable; the IS in the G1 high astigmatism subgroup was significantly better than that in the G2 high astigmatism subgroup (0.22 +/- 0.08 and 0.29 +/- 0.04, respectively; P <.0001). There was comparable scatter of AE values; 30% and 36% in G1 and G2, respectively, had an AE of 0. Similar scatter was observed in the subgroups. Of the eyes that had an AE of 0, 90% and 43% in the high astigmatism subgroups of G1 and G2, respectively (P <.05), had full correction of astigmatism.

CONCLUSION

Limbal marking and subsequent eye and laser astigmatic axis alignment improved the refractive outcome of laser astigmatic treatment of >/=1.25 D. A preliminary report of an ongoing prospective randomized study of eyes that had laser in situ keratomileusis is included.

Effect of laser in situ keratomileusis on tear stability

OBJECTIVE

Patients frequently experience dry eye symptoms after laser in situ keratomileusis (LASIK). The mechanisms that lead to these changes are not well understood. The purpose of this study was to investigate the effect of LASIK on tear function.

DESIGN

Prospective, comparative, nonrandomized interventional trial.

PARTICIPANTS

Fifty-eight consecutive patients (96 eyes) who underwent myopic LASIK treatment.

METHODS

The prospective study involved 58 consecutive patients (96 eyes) who underwent sequential or bilateral LASIK for the correction of myopia. Dry eye symptoms, standardized Schirmer test values, basal tear secretion test, and tear break-up time were measured before surgery and 1 day, 1 week, and 1 month after surgery.

MAIN OUTCOME MEASURES

Schirmer test value, basal tear secretion value, and tear break-up time.

RESULTS

Before surgery, 15.6% of patients (15/96) had dry eye symptoms. After surgery, 94.8% of patients (91/96), 85.4% of patients (82/96), and 59.4% of patients (57/96) experienced dry eye symptoms at 1 day, 1 week, and 1 month, respectively. Schirmer test value (13.32 +/- 10. 67 mm) increased at 1 day (14.48 +/- 10.57 mm; P = 0.25) and subsequently decreased at 1 week (11.18 +/- 9.81 mm; P = 0.05) and at 1 month (10.83 +/- 10.02 mm; P = 0.03). Basal tear secretion test value (8.49 +/- 8.48 mm) decreased at 1 day (6.80 +/- 6.48 mm; P = 0.05), at 1 week (5.97 +/- 6.88 mm; P = 0.005), and at 1 month (5.89 +/- 6.24 mm; P = 0.007). Tear break-up time (5.32 +/- 2.35 seconds) decreased 1 day (4.14 +/- 1.90 seconds; P < 0.001) and 1 week (4.49 +/- 1.70 seconds; P = 0.004) after surgery and recovered by 1 month after surgery (5.09 +/- 3.03 seconds; P = 0.52). Poor preoperative tear functions with a Schirmer test value less than 10 mm was a significant risk factor (72% vs. 46%; relative risk, 1.58 [1.10-2.26]) for experiencing dry eye symptoms at 1 month after surgery.

CONCLUSIONS

Dry eye symptoms are common after myopic LASIK surgery. Laser in situ keratomileusis significantly altered the tear break-up time, Schirmer test values, and basal tear secretion. Patients with preexisting tear flow abnormality as demonstrated by Schirmer test values less than 10 mm are especially at risk of experiencing dry eye symptoms.

Laser in situ keratomileusis flap margin: wound healing and complications imaged by in vivo confocal microscopy

PURPOSE

To examine the healing response of laser in situ keratomileusis flap margin in vivo.

METHODS

Forty-three eyes of 43 patients who had undergone myopic (n = 39) or hyperopic (n = 4) laser in situ keratomileusis were examined once after surgery. The flap margin was imaged by in vivo confocal microscopy at various depths, and the wound healing response, flap alignment, and complications were evaluated. Ten eyes were examined on day 3 postoperatively, 13 eyes at 1 to 2 weeks, 10 eyes at 1 to 2 months, five eyes at 3 months, and five eyes at 6 months or later.

RESULTS

At 3 days after laser in situ keratomileusis, the surface epithelium and basal epithelium appeared normal. Keratocyte activation was strongest at 1 to 2 weeks and 1 to 2 months, and an increased amount of haze was observed correspondingly. Intrastromal epithelial cells forming a plug could occasionally be perceived in the wound gape. Wound constriction was completed in most cases by 3 to 6 months or later. Good alignment was observed in 12 of 43 flaps (27.9%) and moderate and poor alignment in 17 of 43 flaps (39.5%) and 13 of 43 flaps (30.2%), respectively. Poor alignment was not associated with lamellar epithelial ingrowth. Epithelial ingrowth was associated with dense haze at the interface. Diffuse lamellar keratitis was imaged in two corneas after hyperopic laser in situ keratomileusis.

CONCLUSIONS

The laser in situ keratomileusis incision wound at the flap margin appears to heal after the sequence observed in incisional wounds in nonhuman primates. Complications, such as lamellar epithelial in growth and diffuse lamellar keratitis, were often observed, particularly after hyperopic laser in situ keratomileusis.

Photorefractive Keratectomy in Ophthalmic Residents

PURPOSE

To find out how ophthalmologists themselves experience the correction of myopia after photorefractive keratectomy. Visuomotor functions were of special interest.

METHODS

Four ophthalmology residents and one medical engineer underwent photorefractive keratectomy for myopia. Objective measurements including refraction, corneal topography, perimetry, contrast sensitivity, pattern visual evoked potentials, in vivo confocal microscopy, and a car driving simulator test were performed preoperatively, postoperatively, and at 6 months. Subjective evaluation was reported.

RESULTS

Performing ophthalmological examinations and microsurgery without spectacles was easier postoperatively and was appreciated by the four ophthalmology residents. Minimal haze formation, good accuracy, and normal performance in the car driving simulator were also observed. Visual fields, contrast sensitivity, and pattern visual evoked potentials did not show changes. Negative observations included postoperative pain for 2 to 4 days, dry eye symptoms, a period of anisometropia between operations, and hypersensitivity of the lids.

CONCLUSIONS

The four ophthalmic residents were satisfied with the outcome of their refractive surgery. Low to moderate myopic correction did not affect the objective measurements of high and low contrast sensitivity, pattern visual evoked potentials, or simulated car driving in dark illumination.

Effect of lamellar flap location on corneal topography after laser in situ keratomileusis

PURPOSE

To investigate the effect of hinge position on corneal topography after laser in situ keratomileusis (LASIK) for myopia.

SETTING

Academic center and refractive surgery practice.

METHODS

Topography data obtained from 89 eyes of 46 patients after LASIK were analyzed. Using a system of Cartesian coordinates, data along the horizontal and vertical axes were analyzed, measuring sagittal height and power change at 1 mm intervals from the ablation zone center. Data points that were equidistant and on opposite sides of the ablation center were compared to find asymmetry along either axis relative to nasally hinged flaps.

RESULTS

Along the horizontal axis, areas of the cornea closer to the hinge had a higher topography than areas farther from the hinge. Specifically, the points nearest and farthest from the hinge were significantly different in sagittal height (P <.034); the areas farthest from the hinge were reduced more after surgery (relatively lower topography). When results were stratified into low- and high-diopter corrections, this difference was significant in only the high-diopter group (P <.0006). Trends in power change were also observed. Areas of the cornea closer to the hinge were relatively flatter than areas farther from the hinge. Statistical significance was detected in only the low-diopter group at data points 2 mm from the ablation zone center in opposite directions (P <.008). No asymmetry was seen along the vertical axis in power change or sagittal height.

CONCLUSIONS

The lamellar flap in LASIK may influence postoperative corneal topography. Hypothetically, the corneal flap may retract toward the hinge, producing axial asymmetry in the postoperative topography relative to the hinge. Understanding the influence of corneal flap characteristics on post-LASIK topography may improve optical results and may be particularly important in the development and effectiveness of topography-guided ablation techniques.

Photorefractive keratectomy versus laser in situ keratomileusis: comparison of optical side effects. Summit PRK-LASIK Study Group

OBJECTIVE

This report presents patient-reported optical symptoms after photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).

DESIGN

Preoperative and postoperative patient surveys in a prospective, multicenter, randomized clinical trial.

PARTICIPANTS

Two hundred twenty eyes of 220 patients entered the study; 105 were randomized to PRK and 115 were randomized to LASIK.

INTERVENTION

All patients received a one-pass, multizone excimer laser ablation as part of either a PRK or LASIK procedure. Attempted corrections ranged from 6.00 to 15.00 diopters (D).

MAIN OUTCOME MEASURES

Glare, halo, and monocular diplopia symptoms as reported by patients on questionnaires before surgery and at the 6-month follow-up. Comparison was made between symptoms when using optical correction before surgery and symptoms without correction after surgery.

RESULTS

For both the PRK and LASIK groups analyzed individually, the difference in average glare index before surgery and after surgery was not statistically significant (P = 0.54 for PRK; P = 0.15 for LASIK; t test). Twenty-four PRK patients (41.4%) reported worsening of glare symptoms from baseline compared with 11 LASIK patients (21.6%); however, the difference between the two groups was not statistically significant (P = 0.086, chi-square test). Within the PRK group, the difference in average halo index before and after surgery was statistically significant (P = 0.0003, t test); in the LASIK group, it was not statistically significant (P = 0.1 1, t test). Thirty-four PRK patients (58.6%) reported worsening of halo symptoms from baseline compared with 26 LASIK patients (50.0%); this difference was not statistically significant (P = 0.086, chi-square test). For both the PRK and LASIK groups, the difference in average diplopia index before and after surgery was statistically significant (P < 0.0001 for PRK; 0.047 for LASIK; t test). Twenty-six PRK patients (44.8%) reported a worsening of monocular diplopia symptoms from baseline compared with 19 LASIK patients (35.8%); this difference was not statistically significant (P = 0.39, chi-square test). When changes in glare and halo from before surgery to after surgery were pooled as a glare-halo index, however, the PRK group did show a significantly greater likelihood of demonstrating an increase in symptoms compared with the LASIK group (P = 0.048, chi-square test).

CONCLUSIONS

Optical sequelae of glare, halo, and monocular diplopia may occur in some patients after either both PRK or LASIK for moderate to high myopia; in contradistinction, many other patients' preoperative symptoms improve after surgery. On average, PRK patients show an increase in halo and diplopia symptoms, but not glare, after surgery, and LASIK patients show an increase in diplopia, but not glare and halo symptoms. There is a suggestion of a somewhat lesser tendency toward postoperative optical symptoms in LASIK compared with PRK treated eyes.

Retreatment after initial laser in situ keratomileusis

PURPOSE

To report the results of laser in situ keratomileusis (LASIK) retreatment in patients with primary undercorrection and with postoperative regression and to assess the efficacy and safety of LASIK retreatment.

SETTING

The Eye Institute of Utah, Salt Lake City, Utah, USA.

METHODS

The prospective study included 157 eyes of 108 patients. Using the VISX Star laser, retreatments were performed for undercorrection in 43 eyes (27%) and for regression in 114 eyes (73%). The mean follow-up was 15 months (range 6 to 28 months) after the initial surgery and 10 months (range 3 to 25 months) after the repeat LASIK procedure.

RESULTS

Overall, the mean spherical equivalent (SE) was -6.11 +/- 2.35 diopters (D) (range -1.87 to -15.00 D) before LASIK and -1.28 +/- 0.57 D (range -0.50 to -3.25 D) prior to retreatment. At the last visit, it was -0.23 +/- 0.41 D (range -2.55 to 1.13 D). One hundred fifty-three eyes (97.5%) were within +/-1.00 D of emmetropia and 128 (81.5%), within +/-0.50 D. The uncorrected visual acuity was 20/20 or better in 68.8% of eyes and 20/40 or better in 98.1%. In all eyes, the best corrected visual acuity (BCVA) improved or remained within 1 line of the pre-revision level. However, 2 eyes (1.3%) lost 2 or more lines of pre-initial LASIK BCVA. Both eyes had a preoperative SE greater than -8.00 D; corneal irregularity was the cause of the decrease in vision.

CONCLUSIONS

Several conclusions can be drawn from this study. First, LASIK retreatment is effective and safe for correcting undercorrection and regression after initial LASIK, and a good visual outcome is expected. Second, in most eyes, regression occurs within 6 months after the initial LASIK. However, regression can develop up to 2 years after LASIK. Third, multiple retreatments will be required in some patients. The outcome in these cases is promising.

Microkeratome complications of laser in situ keratomileusis

PURPOSE

To evaluate the incidence, types, and outcome of microkeratome complications that occur during laser in situ keratomileusis (LASIK).

DESIGN

Retrospective, noncomparative, case series.

PARTICIPANTS

Three thousand nine hundred ninety-eight eyes that underwent primary LASIK by four surgeons between November 1996 and August 1998 at a university-based refractive center.

METHODS

All cases with significant microkeratome complications leading to abandonment of the LASIK procedure were identified and reviewed.

MAIN OUTCOME MEASURES

Incidence of complications, change in best corrected visual acuity (BCVA), change in refractive error, and types of complication.

RESULTS

There were 27 complications leading to abandonment of the LASIK procedure of 3998 eyes. The overall rate of microkeratome complication was 1 in 150 (0.68%), but it was 1 in 77 (1.3%) in the surgeons' first 1000 eyes, decreasing to 1 in 250 (0.4%) in the last 1000 eyes. Of the 24 planned bilateral cases, 15 complications (63%) happened on the first operated eye. Twenty-six of 27 eyes (96%) recovered to within one line of preoperative BCVA, and one eye lost two lines. At last examination before any repeat refractive procedures, spherical equivalent manifest refraction returned to within 1 diopter (D) of its preoperative value in 18 of 19 eyes (95%), and astigmatism in 16 of 19 eyes (84%) returned to within 1 D of its preoperative value. Sixteen of 27 eyes (59%) had repeat LASIK. Two eyes had complications at repeat LASIK, one of which led to abandonment of the LASIK procedure for a second time.

CONCLUSIONS

There is a significant learning curve in the use of the microkeratome. If ablation is not performed, flap complications rarely lead to significant visual loss and generally do not result in a change in refractive error.

Surgical outcomes of photorefractive keratectomy and laser in situ keratomileusis by inexperienced surgeons

PURPOSE

To investigate the results of photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) procedures performed by novice ophthalmologists and compare the results with those of experienced refractive surgeons.

SETTING

Doheny Eye Institute, University of Southern California, Los Angeles, and Department of Ophthalmology, University of California, Irvine, California, USA.

METHODS

In this retrospective case series, data were examined from the first PRK procedures by 33 consecutive ophthalmologists and the first LASIK procedures by 19 consecutive ophthalmologists. Preoperative and postoperative uncorrected visual acuity (UCVA) and best spectacle-corrected visual acuity (BSCVA), as well as intraoperative and early postoperative complications, were recorded.

RESULTS

In the PRK group, 33.3% of eyes achieved a UCVA of 20/20 and 87.8%, 20/40 or better; 54.5% were within +/-0.5 diopter (D) of emmetropia and 87.8%, within +/-1.0 D. Two eyes with a preoperative spherical equivalent of greater than -11.0 D lost 2 lines of BSCVA. If eyes with low myopia (</= -6.5 D) only were included, 40.7% achieved a UCVA of 20/20 and 96.3%, 20/40 or better. In the LASIK group, 52.6% achieved a UCVA of 20/20 and 84. 2%, 20/40 or better; 78.9% were within +/-0.5 D of emmetropia and 89. 5%, +/-1.0 D. No eye in the LASIK group lost 2 or more lines of BSCVA.

CONCLUSIONS

Photorefractive keratectomy and LASIK are reasonably safe procedures that can be learned quickly by ophthalmic surgeons. Our data suggest that results achieved by beginning surgeons are comparable to those reported by experienced surgeons.

Laser in situ keratomileusis for high myopia with the VISX star laser

PURPOSE

To evaluate the results of laser in situ keratomileusis (LASIK) for spherical and spherocylindrical myopia (range, 9-22 diopters [D]) with the VISX Star laser, (VISX Inc., Santa Clara, CA).

DESIGN

Non-comparative, single-surgeon interventional case series.

PARTICIPANTS

Two hundred ninety eyes of 175 patients.

METHODS

Consecutive patients who underwent LASIK in the study range with the VISX Star laser were evaluated for early (approximately 1 month) and late (after 9 months) outcomes. Both single procedure outcomes and results after reoperation for refractive enhancement were included.

MAIN OUTCOME MEASURES

Outcome measures included uncorrected visual acuity, manifest refraction, refractive predictability, refractive stability, best spectacle-corrected visual acuity (BSCVA), results of reoperations, and complications.

RESULTS

At the early postoperative examination, approximately 1 month after surgery, 285 of 290 eyes (98.3%) were examined. Uncorrected visual acuity of 20/40 or better occurred in 209 of 285 (73.3%) eyes, and 198 of 285 (69.5%) eyes had a manifest spheroequivalent between +/-1.00 D. Subsequently, 60 eyes (20.7%) underwent reoperation for refractive enhancement. Late results, beyond 8 months from the initial surgery and including reoperations, were available in 195 of 290 eyes (67.2%). Uncorrected visual acuity results of 20/40 or better were found in 166 of 195 eyes (85.1%) and of 20/25 or better in 99 of 195 eyes (50.8%). Manifest spheroequivalent results were +/-2.00 D in 187 of 195 eyes (95.9%) and +/-1.00 D in 148 of 195 eyes (75.9%). In a paired-cohort analysis of 131 single-procedure eyes seen at both intervals, refractive stability (change in manifest refractive spheroequivalent of less than 1.00 D) was present in 101 of 131 eyes (77.1%) between the two observation intervals. Overall, approximately 3.6% eyes lost 2 lines or more of BSCVA, and other complications (flap wrinkling and epithelial ingrowth) were reported in 2% of eyes. Improvement in BSCVA of 1 line or more occurred in 5.6% eyes.

CONCLUSIONS

Laser in situ keratomileusis for high myopia with the VISX Star laser provided satisfactory refractive and visual results that compare well with other reports in the literature. Subjective results and other measures of visual function need further evaluation.

Evaluation of Corneal Flap Dimensions and Cut Quality Using the Automated Corneal Shaper Microkeratome

PURPOSE

To evaluate flap dimensions and cut deterioration with repeated blade use in an automated microkeratome.

METHODS

The Automated Corneal Shaper (Chiron-Adatomed, Munich, Germany), 160-microm plate attached, was used to make a corneal flap in 90 pig cadaver eyes, reusing blades up to five times. Flap diameter was measured by planimetry and thickness was calculated by ultrasound pachymetry. Scanning electron microscopy of stromal beds and blade cutting edges was performed to assess cut deterioration after repeated blade use.

RESULTS

Mean flap central thickness was 125 +/- 32 microm. Mean vertical flap diameter was 7.6 +/- 0.4 mm. No correlation was found between thickness and diameter (r = 0.15, P = .45). Progressive thinning of the flap was observed in the direction of the flap hinge. Smooth cuts (using new blades) with periodic chatter lines at the keratectomy edge and in the stromal bed were observed with scanning electron microscopy. Increasing tissue remnants on the stromal bed and decreasing cut quality occurred with repeated blade use. Blades showed larger tissue remnants, nicks, and even folds on the cutting edge proportional to the number of times blades were used.

CONCLUSION

Satisfactory cut quality and reproducibility were obtained after a single use of stainless steel blades in the Automated Corneal Shaper microkeratome. Cut quality was degraded dramatically by repeated use of blades.

Laser in situ keratomileusis for correction of myopia and astigmatism after penetrating keratoplasty

PURPOSE

To determine the safety and effectiveness of laser in situ keratomileusis (LASIK) for visual rehabilitation of residual myopia and astigmatism after penetrating keratoplasty.

DESIGN

Prospective, noncomparative case series.

PARTICIPANTS

LASIK was performed on 23 eyes of 22 patients unable to wear glasses or contact lenses after penetrating keratoplasty due to anisometropia, high astigmatism, and/or contact lens-intolerance.

METHODS

All patients underwent LASIK for visual rehabilitation after penetrating keratoplasty. Uncorrected visual acuity and best spectacle-corrected visual acuity, degree of anisometropia, and corneal transplant integrity were recorded before surgery, as well as at 1 month, 3 months, 6 months, and 12 months after LASIK surgery.

RESULTS

The mean spherical equivalent before surgery was -7.58+/-4.42 diopters (D), which was reduced to -1.09+/-2.01 D, -0.79+/-1.84 D, -0.77+/-1.25 D, and -1.57+/-1.20 D, respectively, at 1, 3, 6, and 12 months after LASIK. The mean cylinder before surgery was 3.64+/-1.72 D, which was reduced to 1.98+/-1.15 D, 1.64+/-1.14 D, 1.48+/-0.92 D, and 1.29+/-1.04 D, respectively, at 1, 3, 6, and 12 months after LASIK. Spherical equivalent anisometropia was reduced from a mean of 6.88+/-4.4 D to 1.42+/-1.05 D at the final examination. Best-corrected visual acuity remained the same or improved in 21 of 23 eyes and decreased by 1 and 3 lines in 2 patients. There were no surgical flap or corneal transplant complications.

CONCLUSIONS

LASIK is a viable treatment alternative for myopia and astigmatism after penetrating keratoplasty in patients who are contact lens-intolerant. LASIK is more effective in treating myopia than astigmatism after penetrating keratoplasty.

Comparing predictability between eyes after bilateral laser in situ keratomileusis: a theoretical analysis of simultaneous versus sequential procedures

OBJECTIVE

To compare the predictability of laser in situ keratomileusis (LASIK) between eyes of individuals to determine whether the refractive result of the first eye is useful in improving fellow eye outcomes.

DESIGN

Single-center case series.

PARTICIPANTS

One surgeon and 196 eyes of 98 patients.

INTERVENTION

All patients received sequential bilateral LASIK. The mean time between procedures was 11.6 days. Attempted corrections ranged from 2.30 to 12.00 diopters (D).

MAIN OUTCOME MEASURES

Predictability (achieved minus attempted correction), postoperative manifest refraction, and theoretical postoperative manifest refraction, using a proposed attempted correction on the second eye based on first eye results, were analyzed.

RESULTS

At 1 week, 1 month, and 3 months, predictability of the first operated eye was correlated with predictability of the fellow eye (1 week: mean 1st = 0.33 D, mean 2nd = 0.33 D, Pearson coefficient = 0.46, P < 0.0005; 1 month: mean 1st = 0.028 D, mean 2nd = -0.020 D, Pearson coefficient = 0.43, P < 0.0005; 3 months: mean 1st = -0.22 D, mean 2nd = -0.12 D, Pearson coefficient = 0.52, P < 0.0005). At the 3-month follow-up of the second eye, comparing the actual distance from emmetropia with that calculated using a theoretical proposed attempted correction based on the first eye refraction, distance from emmetropia was closer in the theoretical correction group. This finding was stronger in patients with preoperative myopia less than 5.5 D (P = 0.03). For this group, 93% of patients in the proposed attempted correction group would fall within 1.0 D of emmetropia compared to 80% found in the actual outcomes.

CONCLUSIONS

The refractive predictability between the two eyes of an individual after LASIK is correlated. Theoretically, therefore, one may be able to achieve correction closer to emmetropia in the second eye by applying the refractive predictability results from the first operated eye. In this study, using a theoretical proposed attempted correction in the second eye based on the first eye outcome, we have shown that better outcomes in the second eye are possible, particularly in low myopes. Thus, it may be advantageous to perform bilateral LASIK sequentially rather than simultaneously, using predictability outcomes from the first operated eye in planning fellow eye treatment. Moreover, waiting approximately 1 week was found to be potentially as effective as waiting longer periods of time between treatments. Further studies are necessary to better assess the actual clinical significance of these findings.

Superficial lamellar keratectomy using an automated microkeratome to excise corneal scarring caused by photorefractive keratectomy

Corneal haze is a recognized complication of excimer laser photorefractive keratectomy. When severe, it can result in the formation of a dense corneal scar, with a reduction in best corrected visual acuity. In extreme cases, medical treatment and repeated phototherapeutic excimer ablations may fail to restore corneal transparency. In these patients, penetrating keratoplasty (PKP) has been used to restore visual function. We describe a technique for excising a superficial corneal scar using an automated microkeratome. The resultant corneal surface is quite smooth, and good visual acuity may be restored without resorting to PKP.

Visual, refractive, and subjective outcomes after photorefractive keratectomy for myopia of 6 to 10 diopters using the Nidek laser

PURPOSE

To analyze the results of photorefractive keratectomy (PRK) for myopia of 6.0 to 10.0 diopters (D) using the Nidek laser and compare them with those in other series, including LASIK, and to analyze the subjective aspects of vision.

SETTING

Remuera Eye Clinic, Auckland, New Zealand.

METHOD

One hundred ninety-two eyes of 162 consecutive PRK patients with a 6 month follow-up were studied. All had myopia in the range of 6.0 to 10.0 D by spherical equivalent. Astigmatism of up to 3.5 D was treated by laser simultaneously. At 6 months, uncorrected visual acuity, best spectacle-corrected visual acuity, residual refractive error, and corneal haze were recorded. After the 6 month examination, a questionnaire was sent to all patients.

RESULTS

Uncorrected visual acuity of 20/20 was achieved in 59% of eyes and of 20/40 or better in 94%. The accuracy of correction was +/- 0.5 D of emmetropia in 77% and +/- 1.0 D in 94%. In 2 eyes (1.0%), corneal haze was assessed as 2+ and 2 Snellen lines of best corrected visual acuity were lost. The questionnaire revealed that 45% of patients had difficulties with night vision. This was better than before surgery in 35% but worse in 31%. Halos were seen around lights by 52%, but these were less than before surgery in 21% and worse in 26%. There was undue sensitivity to glare in 29%, but this was better than before surgery in 19% and worse in 28%. The overall quality of vision was better than before surgery in 60% and worse in 17%. Seventy-seven percent did not need spectacles. Ninety-eight percent said they would have the surgery again.

CONCLUSIONS

As long as the patients are informed of the limitations of PRK for myopia, the results are acceptable.

Retinal detachment associated with excimer laser

Recent reports of retinal pathology associated with laser refractive surgery are documented. The overall risk of retinal disease following photorefractive keratectomy or laser-assisted in situ keratomileusis is discussed, and the potential causal associations between anterior segment laser and posterior segment pathology are assessed.

Surgically induced astigmatism after photorefractive keratectomy and laser in situ keratomileusis. Summit PRK-LASIK Study Group

PURPOSE

To compare the axis and magnitude of surgically induced astigmatism in photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK).

SETTING

Multicenter clinical trial.

METHODS

In this prospective randomized trial, 220 eyes of 220 patients entered the study cohort: 105 randomized to PRK and 115 to LASIK. All patients received a single-pass, multizone excimer laser ablation as part of a PRK or LASIK procedure. Attempted corrections ranged from -6.00 to -15.00 diopters (D). The LASIK procedures were performed with nasal hinges. Absolute changes in astigmatism and axis and magnitude of surgically induced astigmatism were analyzed. Patients were followed for up to 6 month.

RESULTS

In the PRK group, the mean change in absolute astigmatism was +0.14, +0.16 and +0.32 D at 1, 3, and 6 months, respectively; in the LASIK group, the mean change was -0.15, -0.08, and -0.03 D, respectively. At all time points, a greater proportion of PRK than LASIK eyes had an increase in absolute magnitude of astigmatism. In the PRK group, the axis of vectoral-induced astigmatism was significantly different from random at 3 and 6 months (P = .01, P < .001), respectively) with a tendency for induced with-the-rule shifts postoperatively. In the LASIK group, the axis of vectoral-induced astigmatism was significantly different from random at only 1 month (P = .04), and there was no preponderant direction of axis shift. Despite these findings, other analyses showed no statistically significant between-group differences in vectoral axis or magnitude of surgically induced astigmatism.

CONCLUSIONS

Induced astigmatism was generally less and more random in axis in LASIK than in PRK; a general trend for induced with-the-rule astigmatism in PRK was not seen in LASIK. Hypothetically, the lamellar corneal flap in LASIK may counteract the tendency toward steepening at 90 degrees seen in PRK by retracting toward the hinge, by masking underlying induced astigmatism in the ablation zone, or by its mitigating influence on postoperative corneal healing.

Flap complications associated with lamellar refractive surgery

PURPOSE

Corneal lamellar refractive surgery for myopia reduces the risk of corneal haze but adds to the risk of flap complications. We retrospectively determined the incidence of flap complications in the initial series of eyes undergoing lamellar refractive surgery by one surgeon. We assessed the incidence of flap complications overall, the trend in these complications during the surgeon's learning curve, and the impact of the complications on best spectacle-corrected visual acuity.

METHODS

Charts of the first 1,019 eyes that underwent myopic keratomileusis in situ or laser in situ keratomileusis were reviewed for flap complications and visual outcome.

RESULTS

Of the 1,019 eyes, 490 eyes underwent myopic keratomileusis in situ, and 529 eyes underwent laser in situ keratomileusis. Eighty-eight (8.6%) of 1,019 eyes had flap-related complications. Six eyes had two complications. Intraoperative complications included irregular keratectomy in nine eyes (0.9%), incomplete keratectomy in three eyes (0.3%), and a free cap in 10 eyes (1.0%). The incidence of intraoperative complications was six (6.0%) in the first 100 consecutive eyes, 14 (2.3%) in the next 600 consecutive eyes (P = .04, chi-square test), and one (0.3%) in the last 300 eyes (P = .03, chi-square test). Postoperative complications included displaced flaps that required repositioning in 20 eyes (2.0%), folds in the flap that required repositioning in 11 eyes (1.1%), diffuse lamellar keratitis in 18 eyes (1.8%), infectious keratitis in one eye (0.1%), and epithelial ingrowth that required removal in 22 eyes (2.2%). The incidence of flap displacement and folds in 200 eyes in which we irrigated under the flap and allowed it to settle without further manipulation averaged 8.5%, whereas the incidence in other groups of 100 consecutive eyes averaged 0.8% (P < .00001, chi-square test). The incidence of diffuse lamellar keratitis was 0.2% in eyes that had undergone myopic keratomileusis in situ and 3.2% in eyes treated by laser in situ keratomileusis (P = .0003, chi-square test). No eye lost 2 or more lines of best spectacle-corrected visual acuity because of flap complications.

CONCLUSION

Flap complications after lamellar refractive surgery are relatively common but rarely lead to a permanent decrease in visual acuity. Physician experience with the microkeratome and with the handling of the corneal flap decreases the incidence of flap complications.