Effects of laser in situ keratomileusis (LASIK) on the corneal endothelium 3 years postoperatively

Effect of Myopic Femtosecond Laser-Assisted LASIK on Anterior Chamber Inflammation (Flare Values) and Corneal Endothelium: A Prospective before and after Study

PURPOSE

This study aimed to investigate whether femtosecond laser-assisted LASIK (FS-LASIK) surgery causes inflammation in the anterior chamber and to analyze its effect on endothelial cells.

METHODS

This prospective, longitudinal study included left eyes of 30 patients (19 females) who had undergone FS-LASIK surgery due to myopia and myopic astigmatism. Endothelial cell density (ECD) and morphological measurements were performed using a specular microscopy, and laser flare photometry was used to measure the anterior chamber flare values on the day of surgery. iFS™ Advanced FS and VISX STAR S4-IR Wavescan Excimer Laser platforms were used. Flare measurements were repeated on the postoperative 1st day and 7th day and the 1st and 3rd months. The endothelial measurements were repeated in the 3rd month.

RESULTS

Preoperatively, the mean flare was 5.59 ± 1.24 photons/ms; it was 6.49 ± 2.42 on the postoperative 1st day, 5.87 ± 2.27 on the 7th day, 5.68 ± 1.66 on the 1st month, and 5.35 ± 1.24 on the 3rd month. A significant difference was observed only between the preoperative and postoperative 1st day flare values (p=0.047). The decrease in the ECD was clinically insignificant but statistically significant, with an average of 97.0 ± 209.9 cell count/mm2 (3.3%, p=0.017). However, there was no significant change in the coefficient of variation (p=0.448) and hexagonality (p=0.096). No significant correlation was found between the increase in the flare value on the postoperative 1st day and variables. A significant correlation was found between the decrease in ECD and the preoperative ECD (r = 0.356, p=0.027).

CONCLUSION

FS-LASIK caused minimal inflammation in the anterior chamber on only the 1st postoperative day; additionally, a minimal decrease of cell count with no morphological changes were noted in the endothelial cells on postoperative 3rd month. This trial is registered with NCT04899258.

[Morphological changes of cornea in children with hyperopia in the immediate and remote postoperative period after laser keratomieleusis according to confocal microscopy data]

Studying morphological changes of cornea in the remote postoperative period is becoming increasingly relevant with refractive surgeries being adapted for children.

PURPOSE

comparative analysis of keratocyte density and hystomorphologic changes of cornea after laser in situ keratomieleusis (LASIK) and femtosecond laser-assisted LASIK (FS-LASIK) in children with hyperopia.

MATERIAL AND METHODS

109 patients aged 6-17 years in 2 groups were examined with 'Confoscan-4' confocal microscope.

RESULTS

In comparison with initial data, keratocyte density decreased in the immediate postoperative period after FS-LASIK and LASIK in average by 17.09%, 64.31% and 12.2% in the corneal flap, directly in the laser influence zone (interface) and in the retroablation zone respectively. After 5 years, keratocyte density decreased in the corneal flap, interface zone and retroablation zone by 12.01%, 48.71% and 8.06% respectively in comparison with initial data. A circular scar at the flap edge was left after FS-LASIK; keratocyte density in the corneal flap and in the interface zone was in average 8.9% and 15.28% higher respectively, and twice more subepithelial nerves were noted compared to LASIK.

CONCLUSIONS

In the remote postoperative period keratocyte density in the corneal decreased in average by 43% after FS-LASIK and by 46% after LASIK in comparison with initial data. No changes were seen in the morphologic state of the cornea outside the influence zone. Both the technologies are safe, however keratocyte density and the number of subepithelial nerves are higher in the cornea flap and in the interface zone after FS-LASIK; corneal stability is assured by a circular scar formed at the flap edge.

Short term effects of small incision lenticule extraction surgery on corneal endothelium

AIM

To assess the effects of small incision lenticule extraction (SMILE) surgery on the corneal endothelium at 1d to 1mo postoperatively.

METHODS

A retrospective, observational study was conducted on 47 patients (47 eyes) who received SMILE surgery. Patients were grouped according to contact lens wear condition. The corneal endothelium was examined preoperatively and at 1d, 1wk and 1mo postoperatively. The corneal endothelium was analyzed for endothelial cell density (ECD), percentage of hexagonal cells, and coefficient of variation (CV) of cell size.

RESULTS

There were no significant decrease in the ECD, percentage of hexagonal cells or increase in CV at 1d, 1wk and 1mo postoperatively (P>0.05). However, there was a small increase of ECD by 2.88% in contact lens wearers (78.26±113.62 cell/mm(2), P<0.05).

CONCLUSION

SMILE has no significant adverse effects on the corneal ECD and morphology during 1mo follow-up time.

Corneal endothelial cell density after myopic intra-LASIK and the effect of AC gas bubbles on the corneal endothelium

PURPOSE

To evaluate the endothelial cell density (ECD) change after laser-assisted in situ keratomileusis (LASIK) using IntraLase FS30® and the influence of anterior chamber gas bubbles (AC gas bubbles) produced during flap creation on the corneal endothelium during the excimer laser ablation.

METHODS

Myopic LASIK was performed in 436 eyes of 252 patients at Shinagawa LASIK Center. Average age was 32.4±7.05 years. IntraLase FS30® was used for flap creation and Allgretto Wave Eye-Q® 400Hz was used for excimer laser ablation. Preoperative and 3-month postoperative ECD were measured with a noncontact specular microscope (Noncon Robo FA-3509®) and compared. The preoperative and 3-month postoperative ECD changes that developed AC gas bubbles during the flap creation (19 eyes of 18 patients) were also examined. The change of ECD was compared to the group that did not produce AC gas bubbles.

RESULTS

The average ECD reduction after LASIK was -15±102 cells/mm2 for AC gas bubbles (-) group (0.51%, p>0.05) and -35±130 cells/mm2 (1.21%, p>0.05) for AC gas bubbles (+) group. There was no significant ECD change in the AC gas bubbles (-) and AC gas bubbles (+) groups, and no significant difference was observed between AC gas bubbles (-) and AC gas bubbles (+) groups.

CONCLUSIONS

IntraLase FS30® is a safe and effective tool for LASIK operation which does not cause damage to corneal endothelium. Anterior chamber gas bubbles produced during flap creation did not damage corneal endothelial cells and did not interfere with LASIK operations.

Small-aperture corneal inlay for the correction of presbyopia: 3-year follow-up

PURPOSE

To report the 3-year postoperative safety and efficacy outcomes of the Acufocus corneal inlay.

SETTING

University Eye Clinic, Paracelsus Medical University, Salzburg, Austria.

DESIGN

Prospective nonrandomized noncomparative cohort study.

METHODS

The corneal inlay was implanted in the nondominant eye of naturally emmetropic presbyopic patients. Refraction, uncorrected near (UNVA), intermediate (UIVA), and distance (UDVA) visual acuities; corrected distance visual acuity (CDVA); contrast sensitivity; visual fields; subjective patient satisfaction and symptoms; and operative and postoperative adverse events and complications were evaluated.

RESULTS

The study enrolled 32 patients. The mean UNVA improved from Jaeger (J) 6 preoperatively to J1 at 3 years and the mean UIVA, from 20/40 to 20/25, respectively. At 3 years, 97% of eyes had a UNVA of J3 or better and 91% had a UIVA of 20/32 or better. The mean UDVA was 20/20, with all eyes achieving 20/32 or better. Nine eyes (28.3%) lost 1 line of CDVA, 1 eye (3.1%) lost more than 2 lines (3.8 lines), and 3 eyes (9.3%) gained 1 line. No inlay was explanted, and no inflammatory reactions were observed. At 3 years, 15.6% of patients reported severe night-vision problems and 6.3% (versus 87.5% preoperatively) reported being dependent on reading glasses.

CONCLUSIONS

These 3-year results support the safety and efficacy of the corneal inlay to correct presbyopia in naturally emmetropic presbyopic patients. However, despite a significant gain in UNVA and UIVA, 28.3% of patients lost 1 line of CDVA.

Corneal endothelium after refractive surgery

The endothelium is vital to the health and optical clarity of the human cornea. The safety of procedures to correct refractive errors depends on preservation of an intact corneal endothelium. Disease states and genetic and environmental factors affect the corneal endothelium; an unstable corneal endothelium can impact the success of refractive surgery. Technological advances and recent laboratory findings have improved the ability to assess the endothelium. The status of the corneal endothelium after laser in situ keratomileusis, photorefractive keratectomy, phakic intraocular lenses, and adjuvants to these treatments has been the topic of numerous clinical trials. Safety guidelines for refractive surgery procedures should be followed to minimize deleterious effects on the corneal endothelium.

FINANCIAL DISCLOSURE

Neither author has a financial or proprietary interest in any material or method mentioned.

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.

Refractive surgical correction of presbyopia with the AcuFocus small aperture corneal inlay: two-year follow-up

PURPOSE

To evaluate the safety and efficacy of the AcuFocus Corneal Inlay 7000 (ACI 7000) implanted in emmetropic presbyopic patients for the improvement of near and intermediate vision over 2-year follow-up.

METHODS

This prospective, non-randomized, non-comparative study included 32 naturally emmetropic presbyopic patients. The intracorneal inlay was implanted in the non-dominant eye over the pupil by creating a superior-hinged flap with the IntraLase 60-kHz femtosecond laser (Abbott Medical Optics). Inlay centration was over the line of sight. Minimum postoperative follow-up was 24 months.

RESULTS

After mean follow-up of 24.2±0.8 months (range: 24 to 26 months), 96.9% of patients read J3 or better in the implanted eye. Mean binocular uncorrected near visual acuity improved from J6 preoperatively to J1 after 24 months. Mean binocular uncorrected intermediate visual acuity (UIVA) was 20/20 at 1 month and remained 20/20 throughout 24-month follow-up, with 71.9% of eyes reaching UIVA of 20/20 or better. At 24 months, mean uncorrected distance visual acuity was 20/20 in the implanted eye and 20/16 binocularly. No inlay was explanted during the study. Two decentered inlays were recentered after 6 months because of in-sufficient increase in near and intermediate visual acuity. Both patients' near and intermediate visual acuity improved significantly after recentration.

CONCLUSIONS

The ACI 7000 seems to provide a safe and effective treatment for presbyopia over follow-up of 2 years.

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.

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.

Implantable telescope for end-stage age-related macular degeneration: long-term visual acuity and safety outcomes

PURPOSE

To evaluate long-term safety and best-corrected visual acuity (BCVA) results of a telescope prosthesis in patients with end-stage age-related macular degeneration (AMD).

DESIGN

Prospective, open-label clinical trial with fellow-eye controls.

METHODS

Patients with end-stage AMD (bilateral geographic atrophy or disciform scars; BCVA, 20/80 to 20/800) received the telescope prosthesis at 28 centers. Methods were similar to those described in the one-year results, with follow-up visits continuing at 18 and 24 months. Main outcome measures included BCVA change from baseline, endothelial cell density (ECD) and morphometry, and incidence of complications.

RESULTS

At two years, data from 174 (92.6%) of 188 available patients were analyzed. Overall, 103 (59.5%) of 173 telescope-implanted eyes gained three lines or more (doubling of visual angle) of BCVA compared with 18 (10.3%) of 174 fellow control eyes (P < .0001). Mean BCVA improved 3.6 lines (standard deviation [SD], 1.9 lines) and 2.8 lines (SD, 2.3 lines) from baseline in eyes with the 3X and 2.2X device models, respectively. Mean ECD stabilized through two years, with 2.4% mean cell loss occurring from one to two years. There was no significant change in coefficient of variation or percentage of hexagonal endothelial cells from within six months to two years after surgery. The most common complication was inflammatory deposits.

CONCLUSIONS

Long-term results of this telescope prosthesis show the substantial BCVA improvement at one year is maintained at two years. Key indicators of corneal health demonstrate ECD change that reflects remodeling of the endothelium associated with the implantation procedure. ECD stabilizes over time, and there is no evidence of any ongoing endothelial trauma.

Effect of Mitomycin C on the Corneal Endothelium When Used for Corneal Subepithelial Haze Prophylaxis Following Photorefractive Keratectomy

PURPOSE

To evaluate the potential effect of topical mitomycin C (MMC) on the corneal endothelium of myopic patients undergoing photorefractive keratectomy (PRK).

METHODS

Sixteen eyes with a planned ablation depth >75 microm underwent PRK followed by 0.02% MMC applied for 12 seconds using a methylcellulose sponge. Endothelial specular microscopy was performed with the Keeler-Konan specular photomicroscope in 16 eyes before and at least 1 year after surgery. Mean follow-up was 18 months (range: 12 to 24 months). Mean cell density, coefficient of variation of mean cell area, and percentage of hexagonal cells were measured and calculated using computerized morphometric analysis.

RESULTS

Mean endothelial cell densities before and after surgery were 2882 +/- 783 cells/mm2 (range: 1511 to 4022 cells/mm2) and 2867 +/- 588 cells/mm2 (range: 1638 to 3881 cells/mm2), respectively (P > .05). Mean coefficient of variation before and after surgery was 0.30 +/- 0.07 (range: 0.23 to 0.49) and 0.26 +/- 0.04 (range: 0.22 to 0.33), respectively (P=.06). Mean percentage of hexagonal cells before and after surgery was 61% +/- 6.8% (range: 47% to 70%) and 66% +/- 6.7% (range: 54% to 75%), respectively.

CONCLUSIONS

Administration of MMC for haze prophylaxis following PRK did not have a significant effect on quantitative endothelial cell density or qualitative morphometric parameters in this study.

Factors affecting corneal endothelial morphology

PURPOSE

To study the effects of age, race, years of contact lens wear, and degree of myopia on endothelial cell density, the coefficient of variation, and the percentage of hexagonal cells.

METHODS

A total of 149 subjects with a broad variation in age (19 to 71 years), refractive error (39.6% had myopia over -5.00 D), and contact lens history (13.4% had >20 years of wear) were examined. Most subjects were white, but one third were Asian. The Konan specular microscope was used to capture images from 1 eye of each subject and analyzed with the KSS-300 software. Multiple regression analysis was used to build models of endothelial cell density, polymegathism, and pleomorphism.

RESULTS

Age and race significantly affected endothelial cell density (ECD = 3274 - 12.7 x Age + [164 if Asian]). Years of contact lens wear, age, and their interaction significantly affected coefficient of variation (CoV = 24.3 + 0.72 x CLyears + 0.18 x Age - 0.011 x interaction). Years of contact lens wear, age, and refractive error all independently affected the percentage of hexagonal cells (% Hex = 70 - 0.29 x CLyears - 0.21 x Age + 0.4 x Rx).

CONCLUSIONS

The three key aspects of corneal endothelial morphology are influenced by different factors. Any impact of contact lens wear on endothelial cell density may be caused by the confounding effect of age, and refractive error was associated with the percentage of hexagonal cells. Therefore, in studying the influence of drugs, devices, or disease, it is important to control for several subject-related factors.

Wound instability and management after cataract surgery in a patient with prior laser in situ keratomileusis

We report a case of cataract wound instability and subsequent management after cataract surgery in a patient who had had hyperopic laser in situ keratomileusis (LASIK). Standard cataract surgery was performed through a nasal limbal incision. One day postoperatively, the uncorrected visual acuity (UCVA) was 20/20 and the wound was stable. Subsequent examinations revealed overlying corneal edema, cataract wound slippage with corresponding with-the-rule astigmatism, and decreased vision. Separating and resuturing the cataract wound resulted in significant and stable improvement in the UCVA to 20/40. At 18 months, the best corrected visual acuity was 20/20 with a refraction of -3.50 +0.25x155 and keratometry of 44.75/45.00@155. Understanding wound stability and its management in cataract surgery in patients with prior LASIK refractive surgery will become increasingly important as more of these patients present.

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

PURPOSE

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

DESIGN

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

PARTICIPANTS

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

METHODS

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

MAIN OUTCOME MEASURES

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

RESULTS

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

CONCLUSIONS

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

Interface fluid syndrome in laser in situ keratomileusis after complicated trabeculectomy

A 69-year-old man developed stromal edema and a pocket of fluid in the laser in situ keratomileusis (LASIK) interface wound in the left eye after acute endothelial cell loss from complicated trabeculectomy. He eventually required penetrating keratoplasty along with cataract surgery. Histologic examination of the corneal button showed an edematous 720 microm central residual stromal bed, a 54 microm empty space at the level of the central interface wound, and a 154 microm LASIK flap. The endothelial cell count was 0 to 2 cells per high-power field, corresponding to a cell density of 450 to 500 cells/mm(2). Four years after LASIK, the central interface wound was susceptible to forming a pocket of serous fluid after the corneal endothelial function was compromised.

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.

Morphometry of Cells and Guttae in Subjects With Normal or Guttate Endothelium With a Contour Detection Algorithm

PURPOSE

To develop a semiautomatic method to analyze morphology of cells and guttae in corneal endothelium.

METHODS

Specular endothelial pictures from 42 and 21 subjects with healthy and guttate corneas, respectively, were analyzed independently by two observers with cell contour-extracting routines. One observer also analyzed healthy endothelia with the Corner method (Bambi). Differences between observers and between methods in mean cell area (MCA), coefficient of variation (CV), and percentage of cells with five, six, or seven sides were tested for significance with paired t tests. The Contour analysis of pictures with guttae included their mean area.

RESULTS

There were no significant differences in MCA, CV, or the percentage of cells with five, six, or seven sides between the measurements obtained on repeated analysis by the same observer or on a second analysis performed by a different observer with the Contour method. However, the differences between the Contour and Bambi methods were statistically significant for MCA (337.5 +/- 37.7 vs. 327.7 +/- 36.5), CV (0.32 +/- 0.05 vs. 0.30 +/- 0.05), and percentage of cells with six and seven sides, but not for the percentage of five-sided cells. In subjects with guttata, the MCA was 561 +/- 170 microm, and the mean area of guttae was 1,538 +/- 849 microm.

CONCLUSIONS

This detection algorithm is repeatable and reproducible, and it generates a cell border overlay useful in analyzing the morphology of cells and guttae. The analysis of corneal guttae could become a useful follow-up procedure to discriminate between patients with corneal guttata and Fuchs dystrophy.

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.

Pathologic findings in postmortem corneas after successful laser in situ keratomileusis

PURPOSE

To examine the histologic and ultrastructural features of human corneas after successful laser in situ keratomileusis (LASIK).

METHODS

Corneas from 48 eyes of 25 postmortem patients were processed for histology and transmission electron microscopy (TEM). The 25 patients had LASIK between 3 months and 7 years prior to death. Evaluation of all 5 layers of the cornea and the LASIK flap interface region was done using routine histology, periodic acid-Schiff (PAS)-stained specimens, toluidine blue-stained thick sections, and TEM.

RESULTS

In patients for whom visual acuity was known, the first postoperative day uncorrected visual acuity was 20/15 to 20/30. In patients for whom clinical records were available, the postoperative corneal topography was normal and clinical examination showed a semicircular ring of haze at the wound margin of the LASIK flap. Histologically, the LASIK flap measured, on average, 142.7 microm (range, 100-200). A spectrum of abnormal histopathologic and ultrastructural findings was present in all corneas. Findings at the flap surface included elongated basal epithelial cells, epithelial hyperplasia, thickening and undulations of the epithelial basement membrane (EBM), and undulations of Bowman's layer. Findings in or adjacent to the wound included collagen lamellar disarray; activated keratocytes; quiescent keratocytes with small vacuoles; epithelial ingrowth; eosinophilic deposits; PAS-positive, electron-dense granular material interspersed with randomly ordered collagen fibrils; increased spacing between collagen fibrils; and widely spaced banded collagen. There was no observable correlation between postoperative intervals and the severity or type of pathologic change except for the accumulation the electron-dense granular material.

CONCLUSIONS

Permanent pathologic changes were present in all post-LASIK corneas. These changes were most prevalent in the lamellar interface wound. These changes along with other pathologic alterations in post-LASIK corneas may change the functionality of the cornea after LASIK.

Long-Term Changes in Corneal Endothelial Morphology After Discontinuation of Low Gas-Permeable Contact Lens Wear

PURPOSE

Low gas-permeable contact lens wear of polymethyl methacrylate or hydroxyethyl methacrylate material is known to cause morphologic abnormalities in the corneal endothelial cell layer. These lenses were widely prescribed and successfully worn until their use was actively discouraged in the late 1980s and early 1990s. This study was designed to investigate whether discontinuation of low gas-permeable contact lens wear leads to an improvement of corneal endothelial cell morphology.

METHODS

At the time of discontinuation and at least 5 years after discontinuation of low gas-permeable contact lens wear, noncontact specular photographs of the central corneal endothelium were made in 66 patients (14 male and 52 female, mean age 37.7 +/- 8.4, range 24.6-69.0). By computer analysis of endothelial photographs, parameters for polymegethism and pleomorphism were calculated, as well as cell density.

RESULTS

Mean follow-up time between photographs was 6.8 years (SD 1.1). Sixty-one patients were refitted with rigid high gas-permeable contact lenses or high-water-content soft lenses, and 5 patients switched to spectacle wear. A small but significant recovery of the corneal endothelial cell morphology was found for the mean coefficient of variation of cell area, from 37.5 to 35.7 (P = 0.022), and for the coefficient of variation of the number of sides, from 13.1 to 12.4 (P = 0.004). The mean percentage of hexagonal cells increased from 54.2 to 56.2 (P = 0.013). Although the corneal endothelial cell morphology improved significantly on cessation of LGP contact lens wear, the values did not return to levels observed in normal, non-contact lens wearing individuals. During follow-up, the mean endothelial cell density decreased significantly (P = 0.001) from 2994 to 2890 (a 3.5% cell loss in 6.8 years), which is similar to the known normal age-related cell loss of 0.6% per year in non-contact lens wearing healthy individuals.

CONCLUSION

Endothelial polymegethism and pleomorphism caused by PMMA or HEMA contact lens wear is partly reversible.

Long-term results of implantation of phakic posterior chamber intraocular lenses

PURPOSE

To study the incidence and progression of lens opacification after implantation of phakic posterior chamber intraocular lenses for myopia and its correlation with vaulting and endothelial cell density (ECD).

SETTING

Department of Ophthalmology, University of Vienna Medical School, Vienna, Austria.

METHODS

An implantable contact lens (ICL V4, Staar Surgical Inc.) was inserted in 76 myopic eyes. Patients were prospectively followed preoperatively and at 1, 3, 6, 12, 24, and 36 months. The uncorrected visual acuity and best corrected visual acuity (BCVA) were determined. Vaulting was measured optically with a Jaeger II pachymeter, and the crystalline lens was examined at the slitlamp for the presence and characteristics of opacification. Endothelial cell morphometry was performed by specular microscopy, and the ECD was calculated. Eyes in which lens opacification developed were followed for at least 12 months to determine the degree and course of visual impairment.

RESULTS

Lens opacification occurred in 11 eyes (14.5%). Opacification was correlated with intraoperative trauma to the crystalline lens, age older than 50 years, and decreased ECD values throughout the observation period. Vaulting of the ICL did not correlate with the risk for lens opacification. After onset of lens opacification, 6 eyes (55%) had a stable BCVA within +/-0.5 lines and 5 eyes had progressive opacification, losing between 3.5 lines and 0.5 lines (mean 1.8 lines +/- 1.1 [SD]). Three eyes (3.9%) in the progressive group had a 1- to 2-line loss of BCVA over preoperative values and subsequently had cataract surgery.

CONCLUSIONS

Risk factors for lens opacification after implantation of the model V4 ICL included intraoperative trauma to the crystalline lens and older age. Decreased ECD in eyes with opacification suggests ongoing inflammation as a cause. Patients younger than 45 years may have a significantly lower incidence of opacification.

Long Term Analysis of LASIK for the Correction of Refractive Errors After Penetrating Keratoplasty

PURPOSE

To determine the long-term safety and effectiveness of laser in-situ keratomileusis (LASIK) in the treatment of refractive errors following penetrating keratoplasty (PK).

METHODS

A retrospective review was performed of 57 eyes of 48 patients with anisometropia or high astigmatism who were unable to wear glasses or a contact lens after PK and who underwent LASIK for visual rehabilitation. Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BCVA), and corneal transplant integrity were recorded before surgery as well as up to 60 months after LASIK.

RESULTS

The mean follow-up after the LASIK was 21.4 +/- 14.2 months (range 3 to 60 months). Mean preoperative spherical equivalent (SE) was -4.19 +/- 3.38 D. The mean preoperative astigmatism was 4.67 +/- 2.18 D. Preoperative BCVA was 20/40 or better in 42 eyes (74%). At 2 years the mean SE was -0.61 +/- 1.81 D, and mean astigmatism was 1.94 +/- 1.35 D for the 28 eyes with follow-up. UCVA was 20/40 or better in 12 eyes (43%), and BCVA was 20/40 or better in 24 eyes (86%) at 2 years. A gain in BCVA of 1 line or more was seen in 8 eyes (29%). Two eyes (7%) had loss of 2 or more lines of BCVA at 2 years. There were 9 eyes (16%) that developed epithelial ingrowth. Five eyes (9%) in this series had repeat corneal transplants.

CONCLUSIONS

LASIK is effective for reducing ametropia after PK. Proper patient counseling is necessary because the results of LASIK after PK are not as good as, and complications are more frequent than in eyes with naturally occurring myopia and astigmatism. Complications are especially common in patients with mismatch of the donor and host cornea or in those with poor endothelial cell function.

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.

Evaluation of the corneal endothelium after hyperopic laser in situ keratomileusis

PURPOSE

To evaluate corneal endothelial changes after hyperopic laser in situ keratomileusis (LASIK) considering overestimation and underestimation of the cell count measurement.

SETTING

Department of Ophthalmology, Nara Medical University, Nara, Japan.

METHODS

The data were from the clinical trial of the Nidek EC-5000 excimer laser for hyperopic LASIK. The mean correction was 3.59 diopters (D) +/- 1.54 (SD) (range 2.0 to 6.0 D). Using noncontact specular microscopy, the corneal endothelial changes in 25 eyes of 15 patients who had hyperopic LASIK were measured. Follow-up ranged from 6 months (n = 25) to 1 year (n = 21). The overestimation and underestimation of the corneal endothelial cell count that would occur after +5.0 D hyperopic LASIK was hypothetically calculated.

RESULTS

The measured endothelial cell count per 1.0 mm(2) did not significantly decrease up to 1 year after hyperopic LASIK (preoperatively, 2508 +/- 395; at 1 year, 2814 +/- 349). The hypothetical calculation revealed that a +5.0 D hyperopic correction corresponded to a 0.1% underestimation of the corneal endothelial cell count.

CONCLUSIONS

Underestimation of the corneal endothelial cell count after hyperopic LASIK was negligible. Hyperopic LASIK with the Nidek EC-5000 excimer laser did not significantly decrease corneal endothelial cells up to 1 year after surgery.

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.

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.

Endothelial Cell Studies in Patients After Photorefractive Keratectomy for Hyperopia

PURPOSE

To report central and peripheral corneal endothelial cell studies performed as part of the VISX hyperopic photorefractive keratectomy (PRK) clinical trial.

METHODS

During this prospective, multicenter clinical trial, which was part of an FDA investigation, endothelial cell specular microscopy was done at five centers. Non-contact central and peripheral cell density, percent hexagonality, and coefficient of variability of cell size were obtained using the Konan Noncon Robo SP-8000FA with BAMBI analysis software. Data were gathered at baseline and at 1, 6, and 12 months after hyperopic PRK.

RESULTS

Analysis of results of 171 eyes demonstrated no statistically significant detrimental changes in the corneal endothelium at any postoperative time point. The statistically significant changes noted were interpreted as an improvement in cell morphology and were attributed to the cessation of contact lens wear following treatment.

CONCLUSION

Hyperopic PRK with the VISX STAR S2 Excimer Laser System produced no statistically significant adverse effect on the corneal endothelium.

Endothelial decompensation after laser in situ keratomileusis

We report the results of laser in situ keratomileusis (LASIK) in a 58-year-old woman with a history of corneal guttata in the right eye and mild Fuchs' dystrophy in the left eye. Preoperative pachymetry was 586 microm and 656 microm, respectively. The surgical treatment was +1.50 diopters (D) in the right eye and +3.25 D in the left eye. Surgery was performed using a VISX S2 Star laser and a Hansatome microkeratome with a 9.5 mm ring. Postoperatively, edema in the right eye resolved and pachymetry returned to 585 microm, but the left cornea decompensated despite maximum medical therapy and had a final pachymetry of 779 microm. The patient was referred to our cornea service for penetrating keratoplasty, which was performed 14 months after the LASIK treatment.

Two-year Corneal Endothelial Cell Assessment Following INTACS Implantation

PURPOSE

To evaluate the 2-year effects of intrastromal corneal ring segments (INTACS) on the corneal endothelium.

METHODS

Non-contact specular microscopy was performed as a subgroup test in a Phase III clinical trial. Endothelial cell images were collected before surgery and at 6, 12, and 24 months after surgery at the central and peripheral (6 and 10 o'clock) regions. Images were recorded and analyzed later by a central reading center. Cell density, coefficient of variation, and percent hexagonal cells were determined.

RESULTS

There were no clinically significant changes in the endothelial cell structure at 6, 12, and 24 months (102 eyes). There was a gain of 5 cells/mm2 (6 months) and 3 cells/mm2 (12 months) at the central region of the cornea and a loss of 28 cells/mm2 at 24 months. At the 6 o'clock region of the cornea, there was a loss of 0, 24, and 92 cells/mm2 at 6, 12, and 24 months. At the 10 o'clock region of the cornea, there was a loss of 14, 30, and 94 cells/mm2 at 6, 12, and 24 months. INTACS did not statistically affect the central cell density at 6 and 12 months, however, there was a slight loss centrally at 24 months. At 24 months, all corneal regions had a slight decrease in cell density. In all eyes, mean central and peripheral endothelial cell counts remained above 2495 cells/mm2. Coefficient of variation improved and percent hexagonal cells remained unchanged.

CONCLUSION

Endothelial cell density changes at 2 years after INTACS implantation were not clinically significant and endothelial cell remodeling was present.