Laser in situ keratomileusis to treat myopia: early experience

Choroidal Neovascularization after Laser in Situ Keratomileusis in a Patient with Presumed Ocular Histoplasmosis Syndrome

Purpose

A 44-year-old patient with presumed ocular histoplasmosis syndrome (POHS) who developed a choroidal neovascularmembrane (CNV) after laser in situ keratomileusis (LASIK) surgery is presented.

METHODS

A 44-year-old male patient with moderate myopia and POHS who underwent LASIK surgery complained of distorted vision after the procedure. He had a quiet POHS lesion prior to refractive surgery. Fundus examination and fluorescein angiography revealed subfoveal CNV after the LASIK surgery. He underwent 2 sessions of photodynamic therapy (PDT).

Results

Subfoveal CNV involuted after PDT and his vision improved from 20/300 to 20/25 at 13 months follow-up.

CONCLUSIONS

CNV can be triggered by LASIK surgery in patients with POHS. Those patients should be made aware of and closely followed up postoperatively for this complication.

Efficacy and Safety of Topical Timolol Eye Drops in the Treatment of Myopic Regression after Laser In Situ Keratomileusis: A Systematic Review and Meta-Analysis

Aims. The aim of this study was to assess the efficacy and safety of timolol in the treatment of myopic regression after laser in situ keratomileusis (LASIK). Methods. We searched MEDLINE, CENTRAL, EMBASE, China National Knowledge Infrastructure (CNKI), and Chinese Biological Medicine (CBM) from the inception to July 2015 for relevant randomized controlled trials that examined timolol therapy for myopic regression. The methodological quality of the studies included was assessed using the Revman 5.3 software. Results. We included six clinical trials involving 483 eyes in this review, including 246 eyes in treated group and 237 eyes in controlled group. We observed statistically significant improvements on the postoperative SE in the 3 months. However, the change of CCT was not statistically different between the control group and the experimental group. There were fewer cases of IOP, UDVA, and CDVA in treated group having significant difference from the controlled group. Conclusions. Topical timolol could be an effective treatment for reduction of myopic regression especially the spherical errors after myopic LASIK. Further RCTs with larger sample sizes for these trials are warranted to determine the efficacy and limitation for myopic regression after LASIK.

Excimer laser surface ablation: a review of recent literature

The aim was to review the recently published literature on excimer laser surface ablation procedures, including photorefractive keratectomy (PRK), laser sub-epithelial keratomileusis (LASEK), microkeratome-assisted PRK (epi-LASIK) and trans-epithelial (laser-assisted) PRK, to help elucidate where and how surface ablation may best fit into current refractive surgical practice. The emphasis was on publications within the last three years and included systemic reviews, meta-analyses and randomised controlled trials. Where such evidence did not exist, selective large series cohort studies, case-controlled studies and case series with follow-up preferably greater than six months were examined and included. Refractive and visual outcomes are excellent and comparable to those after LASIK even in complex cases after previous corneal surgery. Indeed, surface ablation combined with corneal collagen cross-linking may be used in selected eyes with biomechanical instability, where LASIK is contraindicated. In addition, there is evidence to suggest that there may be less induction of higher order aberrations with surface techniques. Long-term stability and safety appear to be extremely satisfactory. The literature supports the use of modern excimer laser surface treatments, with outcomes comparable to those after LASIK and evidence of less induction of higher-order aberrations. Follow-up studies at 10 to 20 years indicate excellent stability and safety.

Effect of timolol on refractive outcomes in eyes with myopic regression after laser in situ keratomileusis: a prospective randomized clinical trial

PURPOSE

To compare the effects of timolol on refractive outcomes in eyes with myopic regression after laser in situ keratomileusis (LASIK) with a control-matched group.

DESIGN

Prospective, randomized, parallel-controlled, double-masked clinical trial. A computer-generated randomization list based on random block permutation (length 4 to 8) was used for treatment allocation.

METHODS

setting: Basir Eye Center, Tehran, Iran.

PATIENT POPULATION

Of 124 eyes with myopic regression after LASIK using Technolas 217-Z, 45 eyes in each group were analyzed.

INTERVENTION

Patients were randomly assigned into either Group 1, who received timolol 0.5% eye drops, or Group 2, who received artificial tears for 6 months.

MAIN OUTCOME MEASURE

Spherical equivalent (SE) at 6 months posttreatment.

RESULTS

In Group 1, SE improved from -1.48 ± 0.99 diopter (D) before treatment to -0.88 ± 0.91 D and -0.86 ± 0.93 D 6 months after treatment and 6 months after timolol discontinuation, respectively (P < .001). In Group 2, it was -1.57 ± 0.67 D, -1.83 ± 0.76 D, and -1.91 ± 0.70 D, respectively (P < .001). SE was significantly better in Group 1 6 months after treatment and 6 months after discontinuation of treatment (P < .001 for both comparisons). There was a 0.26 D decrease in SE improvement every 4 months after the surgery in the Group 1 (P < .001).

CONCLUSIONS

Timolol application is effective for the treatment of myopic regression after LASIK compared with control group. Its effects last for at least 6 months after its discontinuation.

Outcomes of Retreatment after Aborted Laser In Situ Keratomileusis due to Flap Complications

Purpose:

To determine the refractive outcomes and complications of retreatment after aborted primary laser in situ keratomileusis (LASIK) due to flap complications.

Materials and Methods:

This retrospective study evaluated 50 retreated eyes that had flap complications during primary LASIK at the Eye Consultants Center in Riyadh, Saudi Arabia. Data were analyzed for patients with at least 3 months follow-up post retreatment.

Results:

Thirty-three eyes of 31 consecutive patients with 3 months follow-up or later post retreatment were included. The primary LASIK was aborted due to incomplete flaps in 22 eyes (66.7%), buttonhole flaps in 7 eyes (21.2%), free partial flaps in 3 eyes (9.1%), and a free complete flap in 1 eye (3.0%). Twenty-two eyes (66.7%) were retreated with LASIK, and 11 eyes (33.3%) were retreated with surface ablation. The mean spherical equivalent (SE) was –0.23 ± 0.72 D, the mean astigmatism was –0.65 ± 0.89 D, and the mean loss of the best corrected visual acuity (BCVA) was 0.78 lines at the final postoperative visit. At the last postoperative visit, 20/30 or better BCVA was achieved in 90.1% of eyes that underwent retreatment with LASIK and in 91% of eyes that were retreated with surface ablation. There was no statistical difference in postoperative SE between eyes retreated with LASIK and eyes retreated with surface ablation (P = 0.610). There was no statistical difference in postoperative BCVA between eyes retreated with LASIK and those retreated with surface ablation (P = 0.756). There were no intraoperative complications and no eyes required a second retreatment.

Conclusion:

Creation of a flap after a previous intraoperative flap complication was not associated with any complications. The refractive outcomes of retreatment with LASIK or surface ablation were comparable and reasonably favorable.

Femtosecond LASIK retreatment using side cutting only

PURPOSE

To present visual and refractive outcomes in 11 eyes that underwent femtosecond LASIK and subsequent retreatment with flap lifting using only side cutting.

METHODS

Seven patients (11 eyes) with a mean age of 30.55±5.42 years (range: 24 to 39 years) underwent retreatment 18.18±5.41 months (range: 12 to 26 months) after primary LASIK treatment with side cutting only using a femtosecond laser for the correction of residual refractive error.

RESULTS

Mean follow-up after retreatment was 7.72±1.48 months (range: 6 to 10 months). No intra- or postoperative complications were found after LASIK retreatment. Uncorrected distance visual acuity (UDVA) improved in all patients. Mean UDVA improved from 0.54±0.12 (decimal scale) (range: 0.4 to 0.7) preoperatively to 0.99±0.03 (range: 0.9 to 1.0) after retreatment. No patient lost lines of corrected distance visual acuity.

CONCLUSIONS

Retreatment using a femtosecond laser to create only a side cut is an effective modality to treat residual refractive errors in postoperative LASIK patients.

Intraoperative flap complications in laser in situ keratomileusis with two types of microkeratomes

PURPOSE

To determine the incidence and types of intraoperative flap complications in laser in situ keratomileusis (LASIK) encountered with the Hansatome microkeratome and the Moria microkeratome.

METHODS

In this retrospective case series, all patients with intraoperative flap complications who were treated between June 1999 and July 2008 at the Eye Consultants Center in Riyadh, Saudi Arabia, were identified and reviewed.

RESULTS

Of the 4352 subjects who underwent bilateral primary LASIK procedure, intraoperative microkeratome complications were detected in 89 eyes of 83 patients. The overall incidence of flap complications was 89/8704 (1.00%): incomplete flaps occurred in 53 eyes (0.60%), followed by buttonhole flaps in 17 eyes (0.19%), free complete flaps in 10 eyes (0.11%), free partial flaps in 6 eyes (0.07%), sluffed epithelium in 2 eyes (0.023%), and a splitted flap (vertical flap cut) in 1 eye (0.01%). The incidence rates of intraoperative flap complications with the Hansatome microkeratome and the Moria microkeratome were 1.21% (41/3378) and 0.90% (48/5326), respectively (P = 0.19). There was a statistically significant difference between the two microkeratomes with regard to the incidence of buttonhole flaps: 0.33% (11/3378) for the Hansatome microkeratome versus 0.11% (6/5326) for the Moria microkeratome (P = 0.04).

CONCLUSION

Generally, the incidence rates of intraoperative flap complications with the Hansatome microkeratome and the Moria microkeratome were similar. However, buttonhole flaps occurred more often with the Hansatome microkeratome (a type of microkeratome that produces larger flaps). The commonest complication encountered was the incomplete flap, followed by the buttonhole flap and free flap.

Effect of laser in situ keratomileusis on vision analyzed using preoperative optical quality

PURPOSE

To evaluate the effect on vision of laser in situ keratomileusis (LASIK) based on preoperative optical quality.

SETTING

Universitat Politècnica de Catalunya, Terrassa, and Barcelona Institute of Ocular Microsurgery, Barcelona, Spain.

DESIGN

Comparative case series.

METHODS

The relative change in optical quality and visual acuity were evaluated in eyes that had LASIK for myopia. The optical quality was assessed before and 3 months after surgery using parameters provided by a double-pass system. Patients were classified into 4 groups by preoperative optical quality: low (Group 1), moderate (Group 2), high (Group 3), and very high (Group 4).

RESULTS

The study evaluated 25 patients (50 eyes). The optical quality parameters improved postoperatively in Group 1 and Group 2, with the improvement ranging from 15% to 21% and from 13% to 17%, respectively. The preoperative and postoperative optical quality in Group 3 was similar. The optical quality in Group 4 worsened significantly by percentages ranging from -20% to -26%. Although visual acuity had the same trend, there were no statistically significant changes.

CONCLUSION

The changes in optical quality after LASIK surgery depended on the patient's preoperative optical quality; visual acuity showed the same trend, although no change was significant.

Short-term corneal endothelial changes after laser-assisted subepithelial keratectomy

To investigate the short-term effects of laser-assisted subepithelial keratectomy (LASEK) on the corneal endothelium, 10 patients undergoing LASEK for myopia without complications (20 eyes) were observed. Each eye was evaluated by slit-lamp biomicroscopy and non-contact specular microscopy pre-operatively, and at 15 min, 1 day and 1 week post-operatively. The decrease in endothelial cell density was statistically significant at 15 min post-operatively, and the difference between pre-operative and 15-min post-operative coefficient of variation of cell size was also statistically significant. The percentage of hexagonal cells was significantly different from baseline levels at 15 min and at 1 day post-operatively. All parameters at 1 week post-operatively were not statistically different from those observed pre-operatively. Immediate changes in endothelial cell number and morphology occurred following LASEK, but endothelial morphology returned to the pre-operative condition after 1 week. Long-term follow-up is needed to identify further consequences of this procedure.

Excimer laser-assisted lamellar keratoplasty and the corneal endothelium

PURPOSE

To evaluate endothelial changes after excimer laser-assisted lamellar keratoplasty.

DESIGN

Retrospective, interventional case series.

METHODS

Seven eyes of 7 keratoconus patients were evaluated for 1 year after pachymetry-guided lamellar keratoplasty, performed using the iRES Laser (Ligi Tecnologie Medicali S.p.A.), with the Corneal Lamellar Ablation for Transplantation software (Ligi Tecnologie Medicali S.p.A.) procedure. Both anterior segment optical coherence tomography (Visante OCT; Carl Zeiss Meditec, Inc) and in vivo confocal microscopy (Corneal Confocal Microscope CS4; NIDEK Technologies) images were collected.

RESULTS

Changes in morphologic features were investigated and the endothelium was assessed quantitatively in all 7 patients. In 6 eyes, we measured a mean residual bed thickness of 151.3 +/- 5.46 microm, and a mean endothelial cell density loss of 5.38% at 1 year after surgery, as compared with preoperative values. The mean percentage hexagonality change was 15.67%, and the mean coefficient of variation change was -21.11%. In 1 eye, a residual bed thickness of 72 microm was found and endothelial loss after 1 year was 72.26%; assessment of the coefficient of variation and percentage hexagonality by manual Confoscan4 software (NIDEK Technologies) was not practicable in this case.

CONCLUSIONS

Our results showed that the Corneal Lamellar Ablation for Transplantation procedure induced mild changes to the endothelium in corneas with a mean residual bed thickness of 151.3 +/- 5.46 microm, but serious damage in one eye with a residual bed thickness of 72 microm.

Corneal endothelial cell density after femtosecond thin-flap LASIK and PRK for myopia: a contralateral eye study

PURPOSE

To compare the effect of femtosecond thinflap LASIK and photorefractive keratectomy (PRK) on postoperative endothelial cell density.

METHODS

In a prospective, randomized, contralateral, single-center clinical trial, 25 patients (mean age: 30+/-5 years [range: 21 to 38 years]) underwent PRK in one eye and thin-flap LASIK in the fellow eye for the correction of myopia using a wavefront-guided platform. The central corneal endothelial cell density was measured using the NIDEK Confoscan 4 preoperatively, and at 1 and 3 months postoperatively. Changes in endothelial cell density were analyzed over time between the two refractive techniques.

RESULTS

In PRK, the average preoperative endothelial cell density was 3011+/-329 cells/mm(2), which decreased to 2951+/-327 cells/mm(2) at 1 month (P=.5736) and 2982+/-365 cells/mm(2) at 3 months (P=.6513). In thinflap LASIK, the average preoperative endothelial cell density was 2995+/-325 cells/mm(2), which decreased to 2977+/-358 cells/mm(2) at 1 month (P=.5756) and 2931+/-369 cells/mm(2) at 3 months (P=.4106). No statistically significant difference was found between the two groups at 1 (P=.7404) or 3 (P=.3208) months postoperatively.

CONCLUSIONS

No statistically significant change was noted in endothelial cell density following either PRK or thin-flap LASIK for the treatment of myopia. Furthermore, no statistically significant difference was found between the two groups out to 3 months postoperatively, indicating that thin-flap LASIK is as safe as PRK with regards to endothelial health.

LASIK Complication due to Laser Firing Failure and its Management

A case of an intraoperative Laser in situ keratomileusis (LASIK) complication due to excimer laser firing failure was presented. After cutting the corneal flap, excimer laser treatment was initiated. However, at 34% completion the laser (Technolas((R)) 217z Bausch & Lomb Rochester, NY) stopped firing for no apparent reason. The flap was repositioned over the cornea and the patient was sent to the waiting room. The laser technician was called and he resolved the problem within 20 mins. The same treatment profile was loaded into the laser instrument and 34% of the excimer laser treatment was applied to a piece of paper. Then, the patient was returned to the operating theater and the flap was reopened with a cannula. The remaining (66%) excimer laser treatment was applied in the same session. On the following day the cornea was clear and the uncorrected visual acuity (UCVA) was 20/20. The UCVA increased to 20/16 in the first week and remained at this level at the 6-month follow-up.

Distribution of angle kappa measurements with Orbscan II in a population-based survey

PURPOSE

To determine the mean angle kappa and its determinants in the population of Tehran, Iran.

METHODS

In a cross-sectional survey with random cluster sampling, a total of 442 participants aged >14 years were selected from 4 municipality districts of Tehran for Orbscan acquisitions. Exclusion criteria were history of eye surgery for refractive errors, cataract or glaucoma, and use of topical medication or any type of contact lens at the time of the study. Mean angle kappa in different age and gender groups and its association with other factors was assessed. Considering the high correlation between the right and left eyes, only results of the right eyes are presented.

RESULTS

After applying exclusion criteria, 800 eyes (399 right eyes and 401 left eyes) were examined. Mean participant age was 40.6±16.8 years (range: 14 to 81 years), and 38.8% of eyes were from men. Mean angle kappa was 5.46±1.33° in total; 5.41±1.32° in men and 5.49±1.34° in women (P=.558). It decreased significantly with age; 0.015°/year (P<.001). In individuals with myopia, emmetropia, and hypermetropia, the mean value was 5.13±1.50°, 5.72±1.10°, and 5.52±1.19°, respectively (P=.025); the post-hoc test indicated this was due to the difference between emmetropes and myopes.

CONCLUSIONS

According to our results, angle kappa reduces with age, and the inter-gender difference is not significant. Largest angle kappas were seen among individuals with emmetropia. Angle kappas were larger in the hypermetropic population compared to the myopic population.

Corneal endothelial cell loss 9 years after excimer laser keratorefractive surgery

OBJECTIVE

To determine the long-term changes in the corneal endothelium after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK).

METHODS

Twenty-nine eyes (16 patients) received myopic LASIK or PRK, with intended correction to emmetropia. Central endothelial photographs were taken before and 9 years after surgery and were analyzed by the same masked investigator after appropriate calibration for magnification. Comparisons were made by using generalized estimating equation models to account for any correlation between fellow eyes of the same patient. The annual exponential rate of cell loss was compared with cell loss during a 10-year period in 42 normal (unoperated) corneas of 42 subjects.

RESULTS

Endothelial cell density 9 years after LASIK and PRK had decreased by 5.3% from preoperative density (P < .001), whereas coefficient of variation of cell area (P = .24) and percentage of hexagonal cells (P = .19) did not change. The mean annual rate of cell loss after refractive surgery (0.6% [standard deviation, 0.8%]) was not different from that in normal corneas (0.6% [0.5%], P = .88; minimum detectable difference = 0.5%; alpha = .05; beta = .20).

CONCLUSIONS

Laser in situ keratomileusis and PRK had no long-term effect on the corneal endothelium. Corneas that have undergone LASIK or PRK can be considered for use as donors for posterior lamellar keratoplasty procedures.

Incidence, management, and visual outcomes of buttonholed laser in situ keratomileusis flaps

PURPOSE

To describe the incidence, management, and visual outcomes of buttonholed laser in situ keratomileusis (LASIK) flaps.

SETTING

Private practice, Riyadh, Saudi Arabia.

METHODS

This retrospective review identified eyes that developed buttonholed flaps during LASIK. Preoperative, intraoperative, and postoperative data were obtained to identify factors predictive of this complication.

RESULTS

Of 4250 primary LASIK procedures, 17 eyes (0.4%) with buttonholed flaps were identified. Buttonholes occurred with the Hansatome microkeratome in 64.7% of eyes and with the Moria microkeratome in 35.3% of eyes, the incidence of buttonholed flaps was 0.62% and 0.19%, respectively (P = .03). Laser ablation was performed at the same time as buttonhole formation in 8 eyes (47.1%) and was aborted in the other eyes. Retreatment was performed in 10 eyes (58.8%); of retreated eyes, 6 had repeat LASIK and 3 had surface ablation. The final spherical equivalent refraction was -0.38 diopter +/- 0.79 (SD). Two eyes had a final loss of more than 2 lines of best corrected visual acuity (BCVA). The mean loss of BCVA lines was 0.72 in eyes that had complete LASIK, 0.62 in eyes that had aborted LASIK followed by retreatment with repeat LASIK, and 0.80 in eyes that had aborted LASIK followed by retreatment with surface ablation.

CONCLUSIONS

Buttonholed flaps occurred more frequently in the second of 2 consecutively treated eyes. Microkeratomes that produce a larger diameter flap were more likely to produce flap buttonholes. The least loss of BCVA was achieved when LASIK was aborted and then repeated after refractive stability.

LASIK for myopia of -9.00 to -17.00 D with the VISX STAR S2: 2- to 5-year follow-up

PURPOSE

To evaluate long-term results of LASIK in the correction of high myopia.

METHODS

Preoperative and early postoperative data, including uncorrected and best spectacle-corrected visual acuity and refraction, were collected retrospectively from 77 eyes of 47 patients who underwent LASIK for myopia of at least -9.00 diopters (D) performed with the VISX STAR S2 excimer laser in our hospital from 1999 to 2003. An additional examination with a satisfaction query was performed 2 to 5 years postoperatively.

RESULTS

After 2- to 5-year follow-up, 40% of eyes has a spherical equivalent refraction within 1.00 D of the original intended refraction, 70% within 2.00 D, and 91% within 3.00 D. Only one eye lost two Snellen lines of visual acuity, whereas three eyes gained two lines and the remainder had no significant change. Regression was mild but significant in the long-term, with mean spherical equivalent refraction being -1.21 D at 1 month, -1.82 D at 6 months, and -1.95 D at 2 to 5 years. Stability was similar in a subgroup of eyes followed for at least 4 years. Nine eyes had mild postoperative complications, which resolved without permanent consequences. All patients, except one, were very satisfied with the results and would have chosen the surgery again.

CONCLUSIONS

With careful patient selection and safety precautions, LASIK is a safe alternative with moderate stability but limited predictability in the treatment of myopia of -9.00 to -17.00 D.

Variables affecting refractive outcome following LASIK for myopia

AIM

To investigate factors affecting refractive outcome following LASIK for myopia.

METHOD

Six hundred and seventy-four consecutive uncomplicated myopic LASIK surgeries, performed by a single surgeon, either using the Technolas 217 planoscan (n=372) or the NIDEK EC 5000 (n=302), were evaluated. Stratified random sampling was used to match the groups for refractive error, patient age, and gender. The final analysis included 302 patients from each treatment group. Conditions were identical for both surgeries, and pre-operative refractive errors were between -1.00 and -14.00 DS and <-1.50 DC. Refractive success was defined as -0.50 to +0.50 DS of the targeted refraction measured 3 months after surgery. A stepwise logistical regression analysis was used to determine variables associated with refractive failure.

RESULTS

A successful refractive outcome was achieved in 78% (235/302) of surgeries using the Technolas laser and in 88% (266/302) using the NIDEK laser. Predictor variables for not achieving refractive success were pre-operative refractive error of above -5.00 DS, age more than 40 years, and surgery performed with the Technolas laser.

CONCLUSION

Both the Technolas 217 and the NIDEK EC-5000 excimer lasers achieve a successful refractive outcome in the majority of cases. However, patient and surgical factors can influence refractive outcome.

Eleven-year follow-up of laser in situ keratomileusis

PURPOSE

To report the long-term (11-year) outcomes (stability and complications) of laser in situ keratomileusis (LASIK) in patients with high myopia.

SETTING

University refractive surgery center.

METHODS

Seven patients (4 with bilateral treatment and 3 with unilateral treatment) who had myopic LASIK and completed 11 years of follow-up were included in the study.

RESULTS

The mean age of the 2 men and 5 women was 41.7 years +/- 6.5 (SD) (range 34 to 50 years). The mean follow-up was 140.18 +/- 6.70 months (range 132 to 150 months). At 11 years, the spherical equivalent error was statistically significantly reduced, from a mean of -12.96 +/- 3.17 diopters (D) (range -19.00 to -10.00 D) before LASIK to a mean of -1.14 +/- 1.67 D (range -4.25 to 1.00 D) after (P<.001). Predictability of postoperative refraction 6 months and 11 years after LASIK showed that 6 eyes (55%) were within +/-1.00 D of intended correction. No late postoperative complications occurred. Five patients (8 eyes, 73%) were satisfied with the final outcome.

CONCLUSIONS

Laser in situ keratomileusis was moderately predictable in the correction of high degrees of myopia. After the sixth postoperative month, refractive and topographic stability were obtained. No long-term sight-threatening complications occurred during the follow-up period.

Comparison of residual stromal bed and flap thickness in primary and repeat laser in situ keratomileusis in myopic patients

PURPOSE

To compare the change in residual stromal thickness and flap thickness between primary laser in situ keratomileusis (LASIK) and repeat LASIK in myopic patients.

SETTING

Melbourne Excimer Laser Group, East Melbourne, Australia.

METHODS

This retrospective nonrandomized comparative trial comprised 46 eyes of 34 patients who had repeat LASIK. The thickness of the residual stromal bed was calculated by subtracting the calculated stromal ablation from pachymetry of the stromal bed after cutting the flap in primary treatment and directly measuring during retreatment. The thickness of the LASIK flap in primary and repeat LASIK was calculated by subtracting the central pachymetry of the stromal bed after creating the flap from pachymetry before cutting and lifting the flap, respectively. The main outcome measures were comparison of the residual stromal bed and flap thickness between the primary treatment and the retreatment.

RESULTS

The mean thickness of the calculated residual stromal bed after primary treatment was 329.8 microm +/- 40.8 (SD), and the mean measured residual stromal bed at retreatment was 317.3 +/- 42.8 microm. The mean difference in residual stromal bed thickness was 12.5 +/- 13.0 microm (P<.001). Sixteen eyes (34.7%) had a decrease in bed thickness between 11 microm and 20 microm. The mean flap thickness during primary LASIK and repeat LASIK was 145.2 +/- 17.1 microm and 169 +/- 18.3 microm, respectively. The mean interval between primary treatment and retreatment was 7.4 +/- 4.1 months. The mean change in flap thickness was 23.8 +/- 15.2 microm (P<.001). Fifteen eyes (32%) had an increase in flap thickness between 11 microm and 20 microm. There was a negative correlation between refractive error before primary treatment and the difference in flap thickness. No correlation was found between the difference in flap thickness and the interval between the primary treatment and the repeat treatment.

CONCLUSIONS

Intraoperative pachymetry of the stromal bed during retreatment is strongly recommended as the residual stromal bed and flap thickness changes between primary and retreatment. There is a tendency for the measured stromal bed at retreatment to be thinner than the calculated stromal bed and for the flap to be thicker than previously measured.

Diffuse lamellar keratitis induced by toxic chemicals after laser in situ keratomileusis

PURPOSE

To assess whether toxic chemicals produced during autoclaving sterilization were 1 of the main causes of diffuse lamellar keratitis (DLK) and to analyze the clinical outcomes of patients developing DLK after laser in situ keratomileusis (LASIK) treated with intensive topical corticosteroids.

SETTING

Department of Ophthalmology, Taichung Veterans General Hospital, Taichung, Taiwan, Republic of China.

METHODS

A total of 14 eyes of 7 patients received technically smooth LASIK and developed DLK, including 6 severe and 8 mild DLK cases. In all eyes the same microkeratome was used; it was contaminated with toxic chemical materials produced accidentally by coautoclaving instruments and a foam piece.

RESULTS

Six eyes of 3 patients developed severe DLK on the same day, and 8 eyes of 4 patients developed mild DLK during the next LASIK surgery. After intensive topical corticosteroid treatment, lamellar infiltrates disappeared in 3 days in mild DLK eyes and 2 weeks in severe DLK eyes. No eye was treated with flap lifting and interface irrigation. For grade 4 DLK, the corneal opacity and flap folds disappeared in 4 weeks. There were no instances of permanent corneal scarring or loss of best spectacle-corrected visual acuity.

CONCLUSIONS

Toxic chemicals produced during instrument autoclaving sterilization are a possible cause of DLK. Immediate diagnosis and treatment with intensive corticosteroid drops are critical and can resolve severe DLK.

Cell delivery in regenerative medicine: the cell sheet engineering approach

Recently, cell-based therapies have developed as a foundation for regenerative medicine. General approaches for cell delivery have thus far involved the use of direct injection of single cell suspensions into the target tissues. Additionally, tissue engineering with the general paradigm of seeding cells into biodegradable scaffolds has also evolved as a method for the reconstruction of various tissues and organs. With success in clinical trials, regenerative therapies using these approaches have therefore garnered significant interest and attention. As a novel alternative, we have developed cell sheet engineering using temperature-responsive culture dishes, which allows for the non-invasive harvest of cultured cells as intact sheets along with their deposited extracellular matrix. Using this approach, cell sheets can be directly transplanted to host tissues without the use of scaffolding or carrier materials, or used to create in vitro tissue constructs via the layering of individual cell sheets. In addition to simple transplantation, cell sheet engineered constructs have also been applied for alternative therapies such as endoscopic transplantation, combinatorial tissue reconstruction, and polysurgery to overcome limitations of regenerative therapies and cell delivery using conventional approaches.

Laser in situ keratomileusis in patients with corneal guttata and family history of Fuchs' endothelial dystrophy

PURPOSE

To report 1-year results of laser in situ keratomileusis (LASIK) in 7 eyes with corneal endothelial guttata and a family history of Fuchs' endothelial dystrophy.

SETTING

John Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.

METHODS

A retrospective chart review was performed of 4 patients (7 eyes) who had trace to 1+endothelial guttata and a family history of Fuchs dystrophy and then had uneventful LASIK for the correction of myopia and myopic astigmatism. Preoperative and postoperative measurements included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), corneal pachymetry, endothelial cell density (ECD), manifest refraction, and spherical equivalent. The changes in ECD, pachymetry, and spherical equivalent after LASIK were subjected to statistical analysis using a paired Student t test to determine significance.

RESULTS

Transient corneal edema was noted in the early postoperative period in 3 eyes of 2 patients. At 1 year, 6 of the 7 (86%) eyes had lost > or =2 lines of BSCVA. A statistically significant decrease in ECD of 12.4% +/- 2.7% was observed at 1 year compared with baseline (P < .001). An increase in corneal thickness (P = .006) and a statistically significant myopic shift in spherical equivalent (P = .017) was also noted at 1 year compared with 3 months.

CONCLUSIONS

Patients with mild corneal guttata and a family history of Fuchs' dystrophy are prone to transient corneal edema, loss of BSCVA, endothelial cell loss, and myopic regression after uneventful LASIK for correction of myopia and myopic astigmatism.

Effects of laser in situ keratomileusis on the corneal endothelium

The purpose of this study was to assess the effects of laser in situ keratomileusis (LASIK) on the corneal endothelium. In a prospective study, the corneal endothelium of 87 eyes (45 patients) was examined before and 1 month after LASIK. Patients were divided into two groups: people who wear contact lenses (48 eyes) and people who had never worn contact lenses (39 eyes). The corneal endothelium was analyzed for cell density, percentage of hexagonal cells, and coefficient of variation (CV) of cell size. The mean cell density and percentage of hexagonal cells was significantly higher 1 month after LASIK for all 87 eyes. However, the mean CV of cell size was not significantly different. In contact lens wearers, there was a significant increase in mean cell density and percentage of hexagonal cells, but there was no significant change in mean CV of cell size after LASIK. Among patients who had never worn contact lenses, no significant changes were noted in mean cell density, percentage of hexagonal cells, or mean CV of cell size. In this study, LASIK caused no damage to the corneal endothelium. Postoperative improvements in the mean cell density and percentage of hexagonal cells in patients who were contact lens wearers may be related to the discontinuance of contact lens use after LASIK.

Laser in situ keratomileusis in patients with posterior polymorphous dystrophy

PURPOSE

To report short-term results of LASIK in 4 eyes with the vesicular form of posterior polymorphous dystrophy (PPMD).

METHOD

A review was performed of 2 patients with PPMD who underwent bilateral LASIK. Patients were asymptomatic at the time of presentation and had no prior ocular history. Preoperative measurements were made of uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), corneal pachymetry, and endothelial cell density (ECD). All 4 eyes underwent uneventful LASIK. Postoperative measurements of UCVA and BSCVA were performed at follow-up visits 1 day, 1 month, 3 months, and 1 year after surgery, along with pachymetry and ECD measurements at the 3-month and 1-year visits. Results were analyzed.

RESULTS

At 1 year, all eyes had an UCVA equal to or better than 20/25 and BSCVA equal to or better than 20/20. There was a small mean endothelial cell loss (2.3%) at 1 year. No adverse events were experienced.

CONCLUSIONS

Short-term results indicate efficacy and safety of LASIK on eyes with posterior polymorphous dystrophy. Further study is needed to assess long-term outcomes in a larger study population.

Flap and stromal bed thickness in laser in situ keratomileusis enhancement

PURPOSE

To evaluate whether flap thickness changes after the primary laser in situ keratomileusis (LASIK) procedure and to assess the accuracy of intraoperative pachymetry and ablation depth measurements in predicting stromal bed thickness before enhancement in eyes that have had primary myopic LASIK.

SETTING

Bascom Palmer Eye Institute, Miami, Florida, USA.

METHODS

This retrospective noncomparative interventional case series comprised 57 eyes of 42 patients who had LASIK enhancement between June 2001 and September 2002. Exclusion criteria included previous ocular surgery or complications during the first LASIK procedure. Only patients who had had LASIK and enhancement by the same surgeon at our institution and had intraoperative pachymetry readings for both procedures were included. The original flap was relifted in all enhancement procedures. Corneal thickness was routinely measured intraoperatively by ultrasound pachymetry. The age, eye, refraction, date of primary LASIK, central corneal thickness (CCT) and central stromal bed thickness at primary LASIK, depth of ablation, flap thickness (subtraction pachymetry), date of enhancement, CCT and central stromal bed thickness at enhancement, and flap thickness at enhancement were recorded.

RESULTS

Thirty-one eyes of 26 patients were myopic and 26 eyes of 16 patients were hyperopic before primary LASIK. The mean time between LASIK and enhancement was 218 days +/- 115 (SD) (193 +/- 88 days in myopic eyes and 248 +/- 136 days in hyperopic eyes [P = .068]). The flap tended to be thicker at enhancement than in the primary LASIK procedure by 9.3 +/- 25.7 microm in myopic eyes (P = .054) and 10.5 +/- 16.6 microm in hyperopic eyes (P = .004). A strong correlation was found between flap thickness in the first and second procedures in myopic and hyperopic eyes (r = 0.6). In myopic eyes, the mean difference between the estimated stromal bed thickness after the first procedure (central bed thickness- ablation depth) and the stromal bed thickness measured directly at enhancement was not statistically significant (3 +/- 29 microm; P = .54, paired t test). A strong correlation was found between the 2 measurements (r = 0.8, P<.001). Another strong correlation was found in myopic eyes between the estimated corneal thickness after the primary LASIK and the corneal thickness measured at enhancement (r = 0.81, P<.001). No correlation was found between the difference in flap thickness and the time to enhancement (r = 0.09 in myopic eyes and r = 0.01 in hyperopic eyes).

CONCLUSIONS

Flap thickness tended to be thicker at enhancement than at primary LASIK. Intraoperative pachymetry and ablation depth measurements proved to be precise tools to predict stromal bed thickness before enhancement in eyes that had had primary myopic LASIK. This information may help in planning LASIK enhancements.

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.

Nomogram Adjustment of Laser in situ Keratomileusis for Myopia and Myopic Astigmatism With the Alcon LADARVision System

PURPOSE

To evaluate the visual and refractive results of conventional (non-wavefront) laser in situ keratomileusis (LASIK) for treatment of myopia and myopic astigmatism using the Alcon LADARVision 4000 excimer laser system and nomogram adjustment techniques.

METHODS

A retrospective analysis of 499 eyes that had LASIK for myopia and myopic astigmatism was performed. Preoperative manifest spherical equivalent refraction ranged from -0.43 to -6.00 D and preoperative astigmatism ranged from 0 to -4.75 D. Patients were evaluated during 3 months following surgery.

RESULTS

One month after surgery, 72% of eyes examined (298/415 eyes) had uncorrected visual acuity (UCVA) of 20/20 or better. Three months after surgery, 83% of eyes examined (216/261 eyes) had UCVA of 20/20 or better. One and three months after surgery, 82% and 83% of eyes, respectively, were within +/-0.50 D of attempted correction; 97% of eyes were within +/-1.00 D at both 1 and 3 months. No eye lost more than 1 line of best spectacle-corrected visual acuity (BSCVA) at 3 months after surgery. At the 3-month examination, 83% of eyes had UCVA better than or equal to preoperative BSCVA.

CONCLUSIONS

Conventional LASIK to correct myopia and myopic astigmatism was safe and effective using the Alcon LADARVision 4000 excimer laser system. Outcomes were substantially improved throughout development of an accurate nomogram, derived from continually updated regression analysis of previous refractive results.

Comparison of the IntraLase femtosecond laser and mechanical keratomes for laser in situ keratomileusis

PURPOSE

To compare laser in situ keratomileusis (LASIK) results obtained with the femtosecond laser (IntraLase Corp.) to those obtained using 2 popular mechanical microkeratomes.

SETTING

Private practice, Greensboro, North Carolina, USA.

METHODS

This retrospective analysis compared LASIK outcomes with the femtosecond laser to those with the Carriazo-Barraquer (CB) microkeratome (Moria, Inc.) and the Hansatome microkeratome (Bausch & Lomb, Inc.). The 3 groups were matched for enrollment criteria and were operated on under similar conditions by the same surgeon.

RESULTS

There were 106 eyes in the IntraLase group, 126 eyes in the CB group, and 143 eyes in the Hansatome group. One day postoperatively, the uncorrected visual acuity (UCVA) results in the 3 groups were similar; at 3 months, the UCVA and the best spectacle-corrected visual acuity results were not significantly different. A manifest spheroequivalent of +/-0.50 diopter (D) was achieved in 91% of eyes in the IntraLase group, 73% of eyes in the CB group, and 74% of eyes in the Hansatome group (P<.01). IntraLase flaps were significantly thinner (P<.01) and varied less in thickness (P<.01) than flaps created with the other devices. The mean flap thickness was 114 microm +/- 14 (SD) with the IntraLase programmed for a 130 microm depth, 153 +/- 26 microm with the CB using a 130 microm plate, and 156 +/- 29 microm with the Hansatome using a 180 microm plate. Loose epithelium was encountered in 9.6% of eyes in the CB group and 7.7% of eyes in the Hansatome group but in no eye in the IntraLase group (P =.001). Surgically induced astigmatism in sphere corrections was significantly less with the IntraLase than with the other devices (P<.01).

CONCLUSIONS

The IntraLase demonstrated more predictable flap thickness, better astigmatic neutrality, and decreased epithelial injury than 2 popular mechanical microkeratomes.

To lift or recut: Changing trends in LASIK enhancement

PURPOSE

To report serious complications caused by recutting laser in situ keratomileusis (LASIK) flaps for enhancement and reconsider the current preferred method of LASIK enhancement.

SETTING

Multiple surgeon practices.

METHODS

This retrospective noncomparative nonconsecutive case series comprised LASIK patients in the private practices of 9 experienced refractive surgeons and those reported in a survey of refractive surgeons. Case histories, refractions, corneal topographies, slitlamp photographs, and measurements of uncorrected and best corrected (BCVA) visual acuity after recutting LASIK flaps were collected. Surveys of refractive surgeons and an analysis of changing practice trends among the authors and these surgeons were assessed.

RESULTS

In 12 cases, significant loss of BCVA and subjective visual difficulties resulted from recutting LASIK flaps. Most surveyed surgeons had changed their practice from recutting to lifting flaps even 9 to 10 years postoperatively with good results.

CONCLUSION

Recutting flaps for enhancement should be avoided unless other alternatives are unavailable.

Residual cleaner after normal cleaning of laser in situ keratomileusis instruments

PURPOSE

To determine whether residual cleaner could be detected in the rinse solution of surgical instruments after a standard cleaning protocol.

SETTING

Magill Research Center for Vision Correction, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

The wavelength for maximum absorbance of 5 cleaners (Endozime) [The Ruhof Corp.], Enzol/Cidezyme [Advanced Sterilization Products], and Klenzyme [Steris Co.] enzymatic detergents; Palmolive Ultra dishwashing liquid [Colgate-Palmolive Co.]; and Universal concentrated surgical instrument cleaner and lubricant [B. Graczyk, Inc.]) was determined. Identically designed stainless-steel and titanium instruments were cleaned using a standardized protocol. Water temperatures of 25 degrees C (room temperature) or 40 degrees C (warm temperature) were used to rinse the instruments. The amount of residual cleaner in each rinse solution and remaining on each instrument at the completion of the cleaning procedure as a percentage of the total cleaner was determined.

RESULTS

Residues of all cleaners were detected using a standard protocol involving rinse solutions at 25 degrees C. Increasing the temperature of the rinse solutions significantly reduced the cleaner residues (P<.05, Friedman repeated-measures analysis of variance on ranks test and Student-Newman-Keuls test) regardless of the instrument material. No significant difference was detected in the residual cleaners on stainless-steel and titanium instruments.

CONCLUSIONS

Lower levels of cleaner residue were found on surgical instruments after a standard cleaning protocol using warm rinse water. Because cleaner residue has been reported to cause inflammation (eg, diffuse lamellar keratitis) after laser in situ keratomileusis (LASIK), it is advisable to use cleaners and cleaning protocols that result in acceptable cleaning without detectable levels of cleaner residue to avoid potentially harmful effects to the cornea after LASIK.

Change to Corneal Morphology after Refractive Surgery (Myopic Laser In Situ Keratomileusis) as Viewed with a Confocal Microscope

PURPOSE

This study aimed to look at morphological changes induced by myopic laser in situ keratomileusis (LASIK) in the human cornea using the confocal microscope and to investigate the link between these changes and alterations to corneal sensitivity.

METHODS

An in vivo slit-scanning real-time confocal microscope (Tomey ConfoScan P4, Erlangen, Germany) fitted with an Achroplan 40x/0.75 NA immersion objective and a Cochet-Bonnet esthesiometer were used to examine the morphology and sensitivity of the central corneas of six subjects (12 eyes) at an initial visit (before surgery), and at 1 week, 1 month, 3 months, and 6 months after LASIK for myopia.

RESULTS

Keratocyte density anterior to the flap interface showed differences between visits (p < 0.0001) and was found to be lower than at the initial visit at 1 week, 1 month, 3 months, and 6 months. Microfolds were noted at the level of the anterior limiting membrane in 11 of 12 eyes after surgery at all visits. Highly reflective flap interface particles were seen in all eyes at all visits after surgery. The subepithelial nerve fiber layer was clearly visible before surgery but could not be imaged in any of the eyes after surgery. Short, unconnected nerve fibers were observed 3 months after surgery; these appeared to form anastomosing interconnections after 6 months. Postsurgical corneal sensitivity was reduced during the first 3 months and recovered to presurgical levels after 6 months.

CONCLUSION

LASIK showed a decrease in anterior keratocyte density and microfolds in the anterior limiting membrane, and reflective particles were observed at the flap interface. Corneal sensitivity was depressed during the first 6 months after LASIK surgery; this time course paralleled the appearance of nerve regeneration during this period. Confocal microscopy is capable of providing interesting new insights into the effects of refractive surgery on corneal morphology.

Epi-LASIK: comparative histological evaluation of mechanical and alcohol-assisted epithelial separation

To compare the effect of mechanical and alcohol-assisted excision on the histological ultrastructure of epithelial disks from human corneas. Vardinoyiannion Eye Institute of Crete, University of Crete, Medical School, Crete, Greece. Ten eyes of 10 patients were deepithelialized by 1 of 2 two techniques. In 6 eyes, a customized instrument was used to mechanically separate the epithelial layer. In 4 eyes, the epithelial disks were obtained using the conventional laser-assisted subepithelial keratectomy (LASEK) technique; that is, with alcohol concentrations of 15% and 20%. All specimens were assessed by light and electron microscopy, and the histological findings of the 2 methods were compared. Transmission electron microscopy showed that when the epithelial disks were excised by mechanical separation, the lamina densa and lamina lucida were preserved and the hemidesmosomes had normal morphology along almost the entire length of the basement membrane. The basal epithelial cells of the separated epithelial disks showed minimal trauma and edema. Specimens obtained using 15% and 20% alcohol concentrations showed formation of cytoplasmic fragments of the basal epithelial cells, enlargement of the intercellular spaces, and extensive discontinuities in the basement membrane, which was excised at the level of the lamina lucida. Mechanical separation did not affect the normal cell morphology of the excised epithelial disks. Transmission electron microscopy of the specimens proved the manual technique is less invasive to epithelial integrity than LASEK using either alcohol concentration.

Comparison of designs of laser systems utilized for refractive surgery

Several different laser types are available on the market for the practitioner to use in refractive surgery. Each laser type has certain parameters that the surgeon must understand to obtain the best refractive outcomes. Studies published in peer-reviewed literature between February 2002 and March 2003 show that refractive results across all types of lasers have improved compared with those of several years ago. A difference in refractive outcomes between lasers is impossible to directly compare, as there are no randomized studies that hold surgeon or patient characteristics constant.

Corneal decompensation after laser in situ keratomileusis in fuchs' endothelial dystrophy

PURPOSE

To report corneal decompensation after laser in situ keratomileusis (LASIK) in a patient with Fuchs' endothelial dystrophy.

METHODS

Observational case report.

RESULTS

A 47-year-old woman with cornea guttata without symptoms or findings of corneal edema had uneventful LASIK for -5.50 -0.50 x 150 in the right eye and -4.00 -1.25 x 170 in the left eye. Postoperatively, she developed corneal edema, with significant loss of best-corrected visual acuity in both eyes. Preoperative corneal thickness was 587 microm in the right eye and 549 microm in the left eye, measured by ultrasound pachymetry. These readings were 550 and 560 microm on day 67 postoperatively. Endothelial cell counts showed means of 1209 and 1661 cells/mm2 in the right and left eyes, respectively.

CONCLUSION

Caution is suggested when considering LASIK in eyes with severe cornea guttata.

Corneal flap complications in refractive surgery: Part 1: development of an experimental animal model

PURPOSE

To report the outcome, learning curve, and complication rates of an experimental animal model for corneal flaps in refractive surgery.

SETTING

Magill Research Center for Vision Correction, Storm Eye Institute, Charleston, South Carolina, USA.

METHODS

Corneal flaps with a nasal or a temporal hinge were created in 190 eyes of 95 Dutch Belted rabbits using the Automated Corneal Shaper microkeratome (Bausch & Lomb Surgical). Diffuse lamellar keratitis (DLK) was induced by inoculating the corneal interfaces with 1 of 7 substances. Postoperatively, the eyes were examined with a slitlamp. Special emphasis was placed on corneal flap complications and the relationship between slipped flaps and hinge position and/or inoculation agent.

RESULTS

A good corneal flap was achieved in 174 eyes (92%). The eyes with a nasal hinge had a lower incidence of slipped flaps (14%) than eyes with a temporal hinge (37%) (P =.02).

CONCLUSION

With the animal model described, corneal flaps were created in a precise and reproducible way in more than 90% of eyes. Nasal hinged flaps showed less postoperative displacements than temporal hinged flaps and are adequate for further study.

Effect of Laser in situ Keratomileusis on the Corneal Endothelium

PURPOSE

To assess the effects of laser in situ keratomileusis (LASIK) on the corneal endothelium.

METHODS

In a prospective study, preoperative and 12-month postoperative specular microscopy of the central corneal endothelium and corneal thickness assessment was done in 180 eyes of 105 patients (mean age 31.96 +/- 8.88 years; range 16 to 55 yr) who had LASIK to correct myopia. The central endothelium was analyzed for several parameters including cell density, coefficient of variation, and corneal thickness. Preoperative and postoperative data were compared.

RESULTS

The mean preoperative endothelial cell density was 2,547.37 +/- 282.00 cells/mm2, mean coefficient of variation of cell size was 58.33 +/- 11.50%, and mean central corneal thickness was 558.90 +/- 28.42 microm. There was not a statistically significant change in mean endothelial cell density (2,508.24 +/- 289.57 cells/mm2) or mean coefficient of variation (58.61 +/- 9.89%) at 1 year after surgery (P >.05 ). Average endothelial cell loss was 1.54% at 1 year after surgery. Mean central corneal thickness at 12 months postoperatively was 493.24 +/- 52.55 microm (P<.01).

CONCLUSION

LASIK did not appear to alter corneal endothelial cell density at 12 months postoperatively.

First Clinical Results With the Femtosecond Neodynium-glass Laser in Refractive Surgery

PURPOSE

We evaluated four femtosecond laser intrastromal cutting procedures: creation of a corneal flap for laser in situ keratomileusis (LASIK), tunnel and entry cut for intracorneal ring, corneal flap and removable lens for keratomileusis, and intrastromal ablation for myopia and hyperopia.

METHODS

A clinical trial using a femtosecond surgical laser (IntraLase Corporation) was performed in partially sighted eyes. Femto-LASIK treatment was performed on 46 eyes up to -14.00 D; 16 patients received intracorneal ring segments (Femto-ICRS); 5 patients each with one highly myopic eye had femtosecond laser keratomileusis (FLK), and 13 patients each with one myopic or hyperopic eye had intrastromal ablation (ISPRK). In Femto-LASIK, excimer laser ablation was done under the flap. In Femto-ICRS, ring segments were introduced into the laser-created channels. In femtosecond laser keratomileusis, a lens-shaped block of stroma was removed manually from under the flap.

RESULTS

No difference was found between the results obtained with Femto-LASIK and a standard microkeratome. No refractive effects occurred when the created flap was not elevated. In cases of Femto-ICRS and conventional ICRS produced the same refractive results. With Femto-ICRS, no intraoperative complications occurred and visual acuity improved immediately after surgery. In femtosecond laser keratomileusis, high myopia was corrected without using excimer laser ablation; centralization of the treatment area was excellent. In intrastromal ablation, 1 to 2 hours after surgery the corneas were highly transparent; refractive results were stable.

CONCLUSIONS

Femtosecond lasers can produce precise intrastromal cutting, offering significant safety and other advantages (no razor blades, corneal trauma, partial resections, or sterilization issues) over current techniques.

Diffuse lamellar keratitis: evaluation of etiology, histopathologic findings, and clinical implications in an experimental animal model

PURPOSE

To induce diffuse lamellar keratitis (DLK) and investigate the potential causative agents in an animal model.

SETTING

Magill Research Center for Vision Correction, Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

In 70 eyes of 35 Dutch Belted rabbits, a corneal flap was cut and the interface randomly exposed to 1 of 7 substances: Pseudomonas aeruginosa endotoxin, 1 of 2 Staphylococcus aureus exotoxins, meibomian gland secretion, povidone-iodine 10%, Palmolive Ultra soap, and Klenzyme soap. Slitlamp examinations were performed 1, 3, 5, and 7 days postoperatively. The DLK was staged from 1 to 4. On day 7, the rabbits were killed and the eyes enucleated and processed for histopathologic examination.

RESULTS

At the end of the study, 54 eyes (46 exposed, 8 control) were available for evaluation. The 8 eyes studied concurrently in the control group remained clear and did not show interface inflammation. Thirty-one of 46 eyes (67%) treated with the various test substances developed DLK. The highest DLK rates were found with the cleaning soap Palmolive Ultra (100%; P =.022) and P. aeruginosa lipopolysaccharide endotoxin (90%; P =.026).

CONCLUSIONS

Interface inflammation was consistently induced in the animal model. All 7 agents caused DLK in at least some eyes. The histopathologic evaluation showed the morphologic profile of the marked inflammatory cellular reaction that occurred in almost all the specimens.