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Central Corneal Thickness Z-Ring Corneal Confocal Microscopy Versus Ultrasound Pachymetry

Purpose: To compare the repeatability and validity of corneal pachymetry by a corneal confocal microscope with a z-axis adapter (Confoscan 4.0 with z-ring adapter: z-CS4) versus ultrasound (US) pachymetry in the measurement of central corneal thickness (CCT). Methods: CCT in 44 eyes of 44 subjects was determined with z-CS4. Z-CS4 exams were used to estimate the repeatability of thickness measurement by z-ring adapter for this confocal microscope. Intraclass Correlation Coefficient (ICC) between two different z-CS4 users was also determined. CCT in the same 44 eyes was determined with US pachymetry and measurements were compared with z-CS4 CCT. Results: Z-CS4 CCT showed high intrainstrument reproducibility (ICC = 0.989; 95%CI 0.982-0.993; P < 0.0001). Mean difference among three CCT consecutive measures, in the same eye, was 0.8 ± 11.1 μm. High correlation was found between two users (ICC = 0.896; 95%IC 0.830-0.937; P < 0.0001). Z-CS4 CCT showed high correlation with US pachymetry (ICC = 0.921; 95%CI 0.851-0.958; P < 0.0001). Mean corneal thickness determined was statistically different with the two methods (US: 512.6 ± 65.8 μm; z-CS4: 487.8 ± 60.1 μm; P < 0.0001). Conclusion: Z-CS4 seems an accurate, noninvasive and reproducible technique for CCT evaluation and confirms that central cornea is thinner when measured with confocal microscopy compared to ultrasounds.

Mitomycin C-assisted photorefractive keratectomy in high myopia: a long-term safety study.

Purpose: To evaluate the long-term corneal safety of topical mitomycin C (MMC) used during photorefractive keratectomy to prevent haze formation in highly myopic eyes. Methods: 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. Results: 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/mm2 in the MMC-treated eyes and 11,352 ± 3898 μm/mm2 in the control eyes. At 5 years, the density was higher in the MMC-treated eyes (6790 ± 2447 μm/mm2) than in the control eyes (6024 ± 2977 μm/mm2) (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). Conclusions: 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.

LASEK and photorefractive keratectomy for myopia: clinical and confocal microscopy comparison.

PURPOSE To compare postoperative visual acuity and corneal morphology after laser epithelial keratomileusis (LASEK) versus photorefractive keratectomy (PRK) in the correction of low to moderate myopia. METHODS In a double-blind, randomized clinical trial, 50 myopic patients (mean: -4.5 +/- 1.35 diopters) were randomized to receive LASEK in one eye and PRK in the fellow eye. No mitomycin C eye drops were used in this study. Patients were observed daily for 4 days, then at 1 month and every 3 months up to 1 year. Uncorrected and best-corrected visual acuity (UCVA and BSCVA), manifest refraction, corneal epithelium healing time, postoperative pain, and corneal haze were evaluated. Corneal wound healing was quantified with corneal confocal microscopy. RESULTS Refractive error, UCVA, and BSCVA were not statistically different between eyes treated with LASEK and PRK. Corneal epithelium healing time was 2.52 +/- 0.99 days in the eyes treated with PRK and 2.29 +/- 0.52 days in the eyes treated with LASEK (P=.22). The postoperative pain score was 2.17 +/- 0.87 in the eyes treated with PRK and 2.62 +/- 0.60 (P=.02) in the eyes treated with LASEK. Corneal confocal microscopy showed fewer stromal activated keratocytes and less extracellular matrix deposition in the eyes treated with LASEK than in the eyes treated with PRK at 1 month postoperatively (P=.003). CONCLUSIONS LASEK is an effective and safe procedure for low to moderate myopia, but it seems more painful until full corneal reepithelization. In the early postoperative period, the corneal wound healing process is significantly less intense in eyes treated with LASEK than in eyes treated with PRK. The role of LASEK in corneal wound healing modulation remains controversial.

Long-term Effects on Corneal Keratocytes of Mitomycin C During Photorefractive Keratectomy: A Randomized Contralateral Eye Confocal Microscopy Study

PURPOSE To evaluate the long-term side effects of mitomycin C (MMC) assisted photorefractive keratectomy (PRK) on corneal keratocytes of highly myopic eyes. METHODS Twenty-eight patients with bilateral myopia from -7.00 to -14.25 diopters (D) underwent PRK on both eyes, one eye of each patient received topical application of 0.02% MMC for 2 minutes immediately after the PRK procedure. Corneal keratocyte density was quantified by corneal confocal microscopy at baseline and 5 years postoperatively. RESULTS Photorefractive keratectomy reduced keratocyte density in the most anterior stromal layer, without a statistically significant difference between MMC and standard treated eyes. Posterior stromal layers showed no signs of keratocyte loss with either techniques. CONCLUSIONS Phototherapeutic keratectomy with 0.02% topical MMC has no significant side effects on corneal keratocytes compared to standard PRK, as documented by in vivo corneal confocal microscopy.

Wavefront-optimized surface ablation with the Allegretto Wave Eye-Q excimer laser platform: 12-month visual and refractive results.

PURPOSE To evaluate the wavefront-optimized algorithm of the Allegretto Wave Eye-Q (Wavelight AG) 400-Hz excimer laser platform. METHODS Three hundred three eyes of 303 patients treated with advanced surface ablation were evaluated prospectively. Topical mitomycin C (MMC) was used when ablation was ≥80 μm. Efficacy, safety, and predictability at 12 months were quantified with subjective refraction, visual acuity (logMAR), and slit-lamp examination. RESULTS Mean postoperative uncorrected distance visual acuity (UDVA) was 20/20.5 (0.01±0.05 logMAR). Postoperative UDVA was equal or better than preoperative corrected distance visual acuity (CDVA) in 94.7% of eyes. Efficacy index was 1.05. Corrected distance visual acuity was maintained (93.7%) or improved (5.9%) in 99.6% of treated eyes. No patient lost ≥2 lines. Safety index was 1.05. Haze at 12 months was grade ≤0.5 in 98% of treated eyes and grade ≤1 in 100% of treated eyes. Mean postoperative manifest refraction spherical equivalent (MRSE) was -0.03±0.15 diopters (D). Postoperative MRSE was within ±0.50 D in 99% of eyes. Overcorrection was documented in 0.66% and undercorrection in 0.33% of eyes. CONCLUSIONS The wavefront-optimized algorithm of the Allegretto Wave Eye-Q excimer laser platform showed good efficacy, safety, and predictability in advanced surface ablation, with or without MMC intraoperative use.