Keratectomy For High Myopia Research Articles

Single-step transepithelial photorefractive keratectomy in high myopia: qualitative and quantitative visual functions.

To investigate quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy (TransPRK) in high myopia. In a prospective interventional case-series, 30 eyes with high myopia (-6.00 to -8.75 D) with (up to -3.00 D) or without astigmatism were enrolled from Bina Eye Hospital, Tehran, Iran. One-step TransPRK was performed with aberration-free aspherical optimized profile and SCHWIND AMARIS 500 laser. One-year follow-up results for refraction, visual acuities, vector analysis, ocular wave-front (OWF) and corneal wave-front (CWF) higher order aberrations (HOA), contrast sensitivity (CS), and post-operative haze were assessed. After the surgery, both photopic and mesopic CSs significantly improved (both P<0.001). We detected significant induction of OWF coma and trefoil (P<0.001 for both) HOAs; CWF coma (P=0.002), spherical (P<0.001), and tetrafoil (P=0.003) HOAs in 6 mm analysis diameter; and CWF trefoil (P=0.04) HOA in 4 mm analysis diameter. The range of mean induction observed for various HOAs was 0.005-0.11 µm. The 86.7% of eyes reached an uncorrected distance visual acuity of 20/20 or better; 96.7% of eyes were within ±0.5 D of targeted spherical refraction. In vector analysis, mean correction index value was 1.03 and mean index of success was 0.22. By 12mo after the operation, no eye lost any number of corrected distance visual acuity lines. We detected no corneal haze greater than 1+ throughout the follow-up. Our findings show promising effects of single-step TransPRK on quality of vision in high myopic eyes. It also improves refraction and visual acuity.

Refractive Regression and Changes in Central Corneal Thickness Three Years after Laser-Assisted Subepithelial Keratectomy for High Myopia in Eyes with Thin Corneas: A Retrospective Study

ABSTRACTThis retrospective study aimed to explore refractive regression and central corneal thickness (CCT) following laser-assisted subepithelial keratectomy (LASEK) performed for the correction of high myopia in eyes with thin corneas. Forty patients (19 male, 21 female; mean age, 28.5 years) representing 76 treated eyes were included. The mean optical zone was 6.10 ± 0.32 mm, and the mean ablation depth was 121.53 ± 15.48 µm. CCT was significantly greater three years after surgery than at three months after surgery (425.66 ± 15.44 vs. 385.20 ± 12.81, respectively; p<0.001). The mean change in CCT from three months to three years was 40.46 ± 14.02 µm. The SE at three years was greater than that at three months (p<0.001). Although there was refractive regression, these data suggest that LASEK may have utility in the correction of high myopia in eyes with thin corneas.

Mitomycin C–Assisted Photorefractive Keratectomy in High Myopia: A Long-Term Safety Study

Mitomycin C–Assisted Photorefractive Keratectomy in High Myopia: A Long-Term Safety Study

Mitomycin C–Assisted Photorefractive Keratectomy in High Myopia: A Long-term Safety Study

To evaluate the long-term corneal safety of topical mitomycin C (MMC) used during photorefractive keratectomy to prevent haze formation in highly myopic eyes. Twenty-eight patients with bilateral high myopia underwent photorefractive keratectomy. One eye was randomly assigned to intraoperative 0.02% MMC and the fellow eye to conventional treatment. Each eye was checked at baseline and at 5 years after surgery using in vivo corneal confocal microscopy. At baseline, the endothelial cell density was 2970 ± 295 cells per square millimeter in the MMC-treated eyes and 2839 ± 323 cells per square millimeter in the control eyes. At 5 years, it was 2803 ± 307 and 2780 ± 264 cells per square millimeter, respectively (P = 0.27). The number of corneal nerve fibers was 3.9 ± 1.6 in the MMC-treated eyes and 4.4 ± 1.3 in the control eyes. At 5 years, it was 3.0 ± 1.6 and 2.7 ± 1.3, respectively (P = 0.15). The density of corneal nerves was 9600 ± 2915 μm/mm(2) in the MMC-treated eyes and 11,352 ± 3898 μm/mm(2) in the control eyes. At 5 years, the density was higher in the MMC-treated eyes (6790 ± 2447 μm/mm(2)) than in the control eyes (6024 ± 2977 μm/mm(2)) (P = 0.003). The number of nerve beadings at baseline was 12.9 ± 1.7/100 μm in the MMC-treated eyes and 12.3 ± 2.0/100 μm in the control eyes. At 5 years, it was 9.9 ± 2.6/100 and 9.4 ± 2.9/100 μm, respectively (P = 1.00). At 5 years, corneal nerve branching and tortuosity were similar in the 2 groups (P = 0.88 and 0.54, respectively). Epithelium thickness remained statistically unchanged (P = 0.69). Intraoperative use of topical 0.02% MMC compared with standard treatment does not induce significant long-term corneal changes, as assessed by in vivo corneal confocal microscopy.

Long-Term Results of Excimer Laser Photorefractive Keratectomy in High Myopia: A Preliminary Report

To evaluate the results of 193-nm excimer laser photorefractive keratectomy (PRK) performed on highly myopic eyes with a follow-up of at least 2 years. Fifty-three eyes of 41 patients were treated with a myopic PRK for an attempted correction ranging between -8 and -17 D (mean -10.9 +/- 2.8 SD). The follow-up ranged from 24 to 60 months (mean 34.1 months +/- 10 SD). Fifty-three percent of the eyes achieved a refraction within +/- 2 D of the planned correction, with a refractive error greater than 4 D in 21% of the treated eyes. The uncorrected visual acuity was 20/40 or better in 45% of the eyes. There were no significant opacities in 85% of the eyes examined. A second treatment was performed on 5 eyes. The results suggest that excimer laser PRK is a safe and relatively effective alternative for treating highly myopic eyes, and its effects are stable over a long period of time.

The corneal endothelium 12 months after photorefractive keratectomy in high myopia.

To determine if photorefractive keratectomy with a 193 nm excimer laser could cause human corneal endothelial changes, mainly in high dioptric treatments. 18 patients underwent a treatment ranging from 7 to 13 diopters at the corneal apex (mean 10.3 +/- 1.4 SD) with an estimated corneal thinning ranging from 62 to 116 microns (mean 90.7 +/- 12 SD). In these patients a comparison between the number and shape of the corneal endothelial cells has been performed before and 12 months after PRK. The mean cell density was 2818 +/- 337 mm2, before surgery, and 2894 +/- 301 mm2 after 12 months. The polymorphic index was 79.0 +/- 2.3, before surgery, and 81.0 +/- 5.0 after 12 months with no significant changes (p = 0.16 and P = 0.09, respectively). These results show that photorefractive keratectomy does not cause any significant observable damage to the central corneal endothelium up to 12 months after surgery, even in high myopic treatments.

Results of Photorefractive Keratectomy in High Myopia and Hyperopia

Excimer laser photorefractive keratectomy (PRK) has been used successfully to treat low and moderate myopia. High myopia (>8.0 D) is being successfully treated with PRK using the newer scanning laser systems. The incidence of haze and regression has decreased with the use of these newer systems. As scanning laser systems with larger optical treatment zones have been developed, the postoperative stability of hyperopes has improved. Further evaluation of eyes with longer foltow-up will establish the long-term safety and stability of PRK for hyperopia.

Measurement of Corneal Thickness by Ultrasound After Photorefractive Keratectomy in High Myopia

Photorefractive keratectomy (PRK) has been used to treat myopia in human eyes since 1988. We evaluated corneal ablation depth after excimer laser myopic photorefractive keratectomy with the Summit Technology ExciMed UV200LA laser. Preoperative refraction was: mean 9.58 diopters (D) +/- 2.01, (range 6 to 17). We used ultrasound pachometry (1640 m/sec) in 40 eyes of 33 patients. Mean follow-up was of 49.5 weeks (range 16 to 76). The measurement of the corneal thickness showed a reduction of the initial thickness followed by an inconsistent increase caused by wound healing and tissue proliferation. The data showed no direct correlation between diopters of refractive correction and the change in corneal thickness.