Endothelial cell density after photorefractive keratectomy for moderate myopia using a 213 nm solid-state laser system

One-Year Results of Photorefractive Keratectomy for Myopia and Compound Myopic Astigmatism with 210 nm Wavelength All Solid-State Laser for Refractive Surgery

BACKGROUND

To examine the 12-month clinical and refractive outcomes of PRK performed with a UV all-solid-state laser.

METHODS

The study included healthy patients with myopia and/or compound myopic astigmatism enrolled for refractive surgery and treated with PRK using a 210 nm wavelength, 2 kHz repetition rate, UV all-solid-state laser (LaserSoft, Katana Technologies GmbH, Kleinmachnow, Germany). All subjects were examined at baseline and after 1, 3, 6, and 12 months after the treatment with a slit lamp, refraction, visual acuity assessment (logMAR chart), tonometry, ophthalmoscopy, and corneal tomography with a Scheimpflug camera. The outcome measures considered were uncorrected (UDVA) and corrected (CDVA) distance visual acuities, refraction, central corneal thickness, and transparency. The efficacy, safety, predictability, and stability were determined.

RESULTS

The study included 34 eyes of 19 patients. The mean UDVA changed from 1.20 ± 0.43 to -0.05 ± 0.10 logMAR at 12 months, and the mean CDVA changed from -0.03 ± 0.06 to -0.06 ± 0.09 logMAR, respectively. The mean spherical equivalent (SE) changed from -4.90 ± 2.12 D to -0.01 ± 0.40 D and was within ±0.50 D of the intended correction in 91% of eyes and within ±1.00 D in 97% of eyes at 12 months. No eyes lost lines of visual acuity, and 64% of eyes gained one or more lines.

CONCLUSIONS

PRK with the 210 nm wavelength, 2 kHz repetition rate, all-solid-state laser LaserSoft system proved to have good visual, refractive, and clinical outcomes after the follow-up at 12 months. The emerging gas-free, solid-state technology might be considered a valid alternative for the gas operating lasers for corneal refractive surgery.

Comparison of central corneal thickness and endothelial cell measurements by Scheimpflug camera system and two noncontact specular microscopes

PURPOSE

To investigate the correlation of Scheimpflug camera system and two noncontact specular microscopes in terms of central corneal thickness (CCT) and corneal endothelial cell morphology measurements.

METHODS

One hundred eyes of 50 healthy subjects were examined by Pentacam Scheimpflug Analyzer, CEM-530 (Nidek Co, Ltd, Gamagori, Japan) and CellChek XL (Konan Medical, California, USA) via fully automated image analysis with no corrections made. Measurement differences and agreement between instruments were determined by intraclass correlation analysis.

RESULTS

The mean age of the subjects was 36.74 ± 8.59 (range 22-57). CCTs were well correlated among all devices, with having CEM-530 the thinnest and CellChek XL the thickest measurements (intraclass correlation coefficient (ICC) = 0.83; p < 0.001 and ICC = 0.78; p < 0.001, respectively). Mean endothelial cell density (ECD) given by CEM-530 was lower than CellChek XL (2613.17 ± 228.62 and 2862.72 ± 170.42 cells/mm², respectively; ICC = 0.43; p < 0.001). Mean value for coefficient of variation (CV) was 28.57 ± 3.61 in CEM-530 and 30.30 ± 3.53 in CellChek XL. Cell hexagonality (HEX) with CEM-530 was higher than with CellChek XL (68.70 ± 4.16% and 45.19 ± 6.58%, respectively).

CONCLUSIONS

ECDs with CellChek XL and CEM-530 have good correlation, but the values obtained by CellChek XL are higher than CEM-530. Measurements for HEX and CV differ significantly and show weak correlation. Thus, we do not recommend interchangeable use of CellChek XL and CEM-530. In terms of CCTs, Pentacam, CEM-530 and CellChek XL specular microscopy instruments are reliable devices.

Pilot study of hyperopic LASIK using the solid-state laser technology

BACKGROUND

To evaluate and report the visual, refractive, and aberrometric outcomes of LASIK for the correction of low to moderate hyperopia in a pilot group using a commercially available solid-state laser

METHODS

Prospective pilot study including 11 consecutive eyes with low to moderate hyperopia of six patients undergoing LASIK surgery using the Pulzar Z1 solid-state laser (CustomVis Laser Pty Ltd., currently CV Laser). Visual, refractive, and aberrometric changes were evaluated. Potential complications were evaluated as well. Mean follow-up time was 6.6 months (range, 3 to 11 months).

RESULTS

A significant improvement in LogMAR uncorrected distance visual acuity (UDVA) was observed postoperatively (p = 0.01). No significant change was detected in LogMAR corrected distance visual acuity (CDVA) (p = 0.21). Postoperative LogMAR UDVA was 0.1 (about 20/25) or better in ten eyes (90.9 %). Mean overall efficacy and safety indices were 1.03 and 1.12. Postoperatively, no losses of lines of CDVA were observed. Postoperative spherical equivalent was within ± 1.00 D in ten eyes (90.9 %). With regard to aberrations, no statistically significant changes were found in higher order and primary coma RMS postoperatively (p ≥ 0.21), and only minimal but statistically significant negativization of primary spherical aberration (p = 0.02) was observed. No severe complications were observed.

CONCLUSION

LASIK surgery using the solid-state laser technology seems to be a useful procedure for the correction of low to moderate hyperopia, with minimal induction of higher order aberrations.

Results of laser in situ keratomileusis performed using solid-state laser technology

PURPOSE

To evaluate and report the visual, refractive, and aberrometry outcomes of laser in situ keratomileusis (LASIK) to correct low to moderate myopia using a commercial solid-state laser.

SETTING

Oftalmar, Medimar International Hospital, Alicante, Spain.

DESIGN

Prospective case series.

METHODS

This study evaluated consecutive eyes with low to moderate myopia that had LASIK performed using a Pulzar Z1 solid-state laser. Visual, refractive, and aberrometry changes as well as potential complications were evaluated.

RESULTS

The study enrolled 60 eyes (34 patients). The mean follow-up was 8.5 months (range 6 to 13 months). There was a significant improvement in logMAR uncorrected distance visual acuity (UDVA) postoperatively (P<.01). No significant change was detected in logMAR corrected distance visual acuity (CDVA) (P=.21). The postoperative logMAR UDVA was 0.1 (approximately 20/25) or better in 57 eyes (95.00%). The mean overall efficacy index was 0.99 and the mean safety index, 1.02. Postoperatively, 1 eye (1.67%) lost lines (1 line) of CDVA. The postoperative spherical equivalent was within ± 0.50 diopter in 58 eyes (96.67%). There was a small, but statistically significant increase in the primary coma root mean square (0.17 μm) and in the magnitude of primary spherical aberration (0.09 μm). No severe complications occurred.

CONCLUSION

Laser in situ keratomileusis using the solid-state laser provided predictable correction of low to moderate myopia, minimizing the induction of higher-order aberrations and preserving CDVA.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Photorefractive keratectomy in posterior polymorphous dystrophy with vesicular and band subtypes

PURPOSE

To evaluate the safety and efficacy of photorefractive keratectomy (PRK) in patients with posterior polymorphous dystrophy (PPMD) with vesicular and band subtypes.

SETTING

Walter Reed Center for Refractive Surgery, Washington, DC, USA.

DESIGN

Case series.

METHODS

The records of patients with PPMD who had PRK between January 2002 and May 2009 were reviewed. Data for analysis included sex, age, ablation depth, residual stromal bed thickness, manifest spherical equivalent, uncorrected (UDVA) and corrected (CDVA) distance visual acuities, central corneal thickness (CCT), endothelial cell density (ECD), intraocular pressure (IOP), and complications. Preoperative and postoperative results were compared using the Wilcoxon signed-rank test, with P < .05 considered significant.

RESULTS

Fourteen eyes of 7 men (mean age 29.1 years ± 9.1 [SD]; range 21 to 42 years) with at least a 6-month follow-up were reviewed. At the final follow-up (mean 19.5 months; range 6.3 to 58.3 months), all eyes had a UDVA of 20/15 and all eyes were within ± 0.50 diopter of emmetropia. The CDVA was unchanged from preoperatively in 71.4% of eyes and improved by 1 line in 28.6%. There were no significant complications. The IOP did not change significantly over the follow-up (P = .272). At the final visit, the mean ECD (2795.3 ± 366.0 cells/mm(2)) was unchanged from baseline (2809.1 ± 338.3 cells/mm(2)) (P = .114).

CONCLUSIONS

Photorefractive keratectomy in PPMD patients with vesicular and band subtypes resulted in excellent visual outcomes and a low incidence of adverse effects. Endothelial cell densities did not change significantly in the early postoperative period.

FINANCIAL DISCLOSURE

No author has a financial or proprietary interest in any material or method mentioned.

Comparison of wavefront-guided photorefractive keratectomy and foldable iris-fixated phakic intraocular lens implantation for low to moderate myopia

PURPOSE

To compare and evaluate the visual and refractive outcomes of myopic wavefront-guided photorefractive keratectomy (PRK) and foldable phakic intraocular lens (pIOL) implantation for myopia.

SETTING

Department of Ophthalmology, Haaglanden Medical Center, The Hague, The Netherlands.

DESIGN

Comparative case series.

METHODS

The differences in visual acuity and residual refractive outcomes after wavefront-guided PRK and Artiflex foldable pIOL implantation were compared in eyes with low to moderate myopia (spherical error -4.0 to -7.0 diopters [D]; maximum cylinder 2.25 D). One-year follow-up results are presented.

RESULTS

At 1 year postoperatively, the mean decimal Snellen uncorrected distance visual acuity was 1.05 ± 0.21 (SD) in the PRK group (60 eyes) and 1.04 ± 0.21 in the pIOL group (33 eyes) and the mean corrected distance visual acuity (CDVA), 1.21 ± 0.18 and 1.24 ± 0.13, respectively. In the PRK group, 21.7% of eyes lost 1 to 3 lines of CDVA and 11.7% of eyes gained 1 or 2 lines. In the pIOL group, no eye lost lines of CDVA and 42% gained 1 or 2 lines. At 1 year, 80.0% of eyes in the PRK group and 90.9% of eyes in the pIOL group were within ± 0.50 D of the spherical equivalent.

CONCLUSION

There were no statistically significant differences in safety and efficacy between the pIOL group and the PRK group at 1 year. However, the percentage of eyes that gained lines of CDVA was significantly higher in the pIOL group.

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.

A comparison of corneal cellular responses after 213-nm compared with 193-nm laser photorefractive keratectomy in rabbits

PURPOSE

Corneal refractive surgery is typically performed using a 193-nm excimer laser. However, a recently developed 213-nm solid-state (5th harmonic) Nd:YAG laser presents some practical and user safety advantages, although the biological impact of using this wavelength remains poorly characterized. Here, we provide in vivo and in vitro comparisons of the corneal cellular outcomes after irradiation with 213 and 193 nm wavelengths.

METHODS

New Zealand White rabbits underwent photorefractive keratectomy with -5 diopters and a 6.5-mm optical zone and studied at time points up to 1 year. The development of haze was examined ophthalmologically and by detecting myofibroblasts immunohistochemically. Cell death was quantified using a terminal deoxynucleotidyl transferase-dUTP nick end labeling (TUNEL) assay, and the number of stromal keratocytes undergoing apoptosis estimated histologically. Superoxide dismutase activity was estimated in vitro by enzyme-linked immunosorbent assay in irradiated rabbit corneal keratocytes.

RESULTS

Our results demonstrate subtle differences in the cellular outcomes after irradiation with 213- and 193-nm lasers, despite similar degrees of corneal haze developing in both treatment groups. In vivo, the 213-nm laser results in more stable stromal cell numbers, implying a more predictable ablation outcome. In vitro, higher levels of superoxide dismutase in corneal keratocytes irradiated with 213 nm compared with 193 nm wavelengths suggest a better endogenous protection against free radicals induced by laser surgery.

CONCLUSIONS

The more favorable cellular responses after irradiation with 213 nm compared with 193 nm wavelengths are consistent with good clinical outcomes previously reported. Ablation with a 213 nm wavelength may result in better wound healing, leading to a more reliable correction of refractive errors.