Epithelial removal with the excimer laser (laser-scrape) in photorefractive keratectomy retreatment

The Effectiveness of Corneal Epithelial Debridement Performed with an Alcohol-Impregnated Sponge

OBJECTIVE

To evaluate the clinical outcomes of patients who underwent corneal surgery with debridement of epithelium by localised application of an alcohol-impregnated sponge instead of the usual alcohol reservoir method.

DESIGN

This study retrospectively included 52 eyes of 27 patients who underwent LASEK (laser-assisted subepithelial keratectomy) and CXL (cross-linking) surgery after application of this alcohol-assisted debridement method between January 2019 and April 2019.

PARTICIPANTS

Twenty-four patients who underwent LASEK and three patients who underwent CXL surgery were included in this study, which comprised a total of 52 eye operations.

METHODS

Epithelial debridement was performed after placing a 20% ethanol-impregnated sponge on the cornea for 20 seconds.

RESULTS

The mean pachymetry value was 509.40 ± 30.37 µm, the mean preoperative spherical equivalent was - 2.14 ± 1.02 dioptres, and the highest myopia and astigmatism values were - 4.25 dioptres and - 2.75 dioptres, respectively. It was seen that the corneal epithelium was completely and easily debrided in a size identical to that of the applied sponge.

CONCLUSIONS

Complete debridement of the corneal epithelium can be performed quickly, safely, and easily with this specially prepared sponge.

One-step transepithelial topography-guided ablation in the treatment of myopic astigmatism

PURPOSE

To evaluate one-step topography-guided transepithelial ablation in the treatment of low to moderate myopic astigmatism using a 1KHz excimer laser.

METHODS

Retrospective study of 117 consecutive eyes available for evaluation 12 months after surgery. Pre- and post-operative visual and refractive data as well as post-operative pain and haze were analyzed. A novel technique integrating custom refractive- and epithelial- ablation in a single uninterrupted procedure was used.

RESULTS

The mean pre-operative spherical equivalent (SE) and the mean cylinder were: -3.22 diopters (D) ±1.54 (SD) (range -0.63 to -7.25 D) and -0.77 D ±0.65 (range 0 to -4.50 D), respectively. At 12 months after surgery: no eyes lost ≥2 lines of corrected distant visual acuity (CDVA). Safety and efficacy indexes were 1.27 and 1.09, respectively. Uncorrected distant visual acuity (UDVA) was ≥20/20 in 96.6% of the eyes. Manifest refraction spherical equivalent was within ±0.5 D of the desired refraction in 93.2% of the eyes. Average root mean square (RMS) wavefront error measured at central 6 mm, increased from 0.38 pre-operatively to 0.47 µm post-operatively. Refractive stability was achieved and sustained 1 month after surgery. No visually significant haze was registered during the observation period. Post-operative pain was reported in 4.5% of patients.

CONCLUSIONS

One-step transepithelial topography-guided treatment for low to moderate myopia and astigmatism performed with a 1 KHz laser, provided safe, effective, predictable and stable results with low pain and no visually significant haze.

Combined phototherapeutic keratectomy and therapeutic contact lens for recurrent erosions in bullous keratopathy

AIMS

To evaluate the therapeutic effects of excimer laser phototherapeutic keratectomy (PTK) combined with therapeutic contact lens for painful recurrent corneal erosions (RCE) secondary to bullous keratopathy (BK) not suitable for penetrating keratoplasty.

METHODS

Excimer laser PTK was performed prospectively in eight eyes with painful RCE due to BK visually expecting no benefit from penetrating keratoplasty. After mechanical removal of the epithelium, the corneas were ablated with 50 pulses in the central 6.5 mm zone (ablation rate 0.25 microm per pulse) and another 200 pulses for polishing the periphery. After PTK, therapeutic contact lenses were applied for 3 months. The mean follow up period after PTK was 10.9 months (ranging from 6 to 15 months).

RESULTS

All patients experienced relief of their pain symptoms after the epithelium healed. Only one patient complained of occasional stinging pain with intermittent recurrence of small bullae. He refused a second treatment because the pain was much less than that before the surgery and quite tolerable. No infection or other complications were noted.

CONCLUSION

PTK with deeper ablation and adjunctive therapeutic contact lens is an easy to perform and effective treatment with less recurrence rate for patients with BK and poor visual potential.

Laser in situ keratomileusis enhancement after photorefractive keratectomy

OBJECTIVE

To describe the safety, effectiveness, and predictability of laser in situ keratomileusis (LASIK) for correcting residual myopia after primary photorefractive keratectomy (PRK).

DESIGN

A retrospective, noncomparative case series.

PARTICIPANTS AND INTERVENTION

Thirty-six consecutive eyes of 30 patients underwent LASIK after primary PRK. A Multiscan Schwind excimer laser was used for LASIK enhancement.

MAIN OUTCOME MEASURES

Uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity, refraction, videokeratography, and complications were determined before and after LASIK retreatment. Follow-up was at least 12 months.

RESULTS

Before LASIK, 11.11% of eyes showed a UCVA of 20/40 or better. This increased to 94.44% 12 months after LASIK. A UCVA of 20/25 or better was achieved in 0% before and in 72.22% after retreatment. Refraction +/-0.5 diopters (spherical equivalent) represented 0% of eyes before and 77.78% of eyes after enhancement. Before LASIK, two eyes had significant haze. Haze remained in these two eyes and appeared in another eye.

CONCLUSIONS

Laser in situ keratomileusis proved to be safe and effective for treating residual myopia after PRK. Care must be taken when considering LASIK retreatment in patients with significant haze after primary PRK.

Corneal haze after photorefractive keratectomy using different epithelial removal techniques: mechanical debridement versus laser scrape

PURPOSE

To determine differences of corneal wound healing and haze after photorefractive keratectomy (PRK) using either mechanical epithelial debridement or laser-scrape epithelial removal in human subjects.

DESIGN

A 6-month randomized, masked, prospective, paired-eye clinical study.

PARTICIPANTS

Twenty eyes in 10 myopic patients treated between March 1999 and May 1999.

INTERVENTION

Photorefractive keratectomy treatments with two different epithelial removal techniques. Continuous z-scan of confocal image, termed confocal microscopy through focusing (CMTF), was performed before surgery and at 3 weeks, 6 weeks, 3 months, and 6 months after surgery.

MAIN OUTCOMES MEASURES

Epithelial and stromal thickness measurement, achieved stromal ablation depth, and objective assessment of corneal light-backscattering (corneal haze) were obtained from digital image analysis of the CMTF scans. Manifest refraction was also measured. Student's paired t test or two-way repeated-measures analysis of variance after rank transformation were performed to evaluate statistical differences between groups.

RESULTS

Comparison of the mean posttreatment spherical equivalent between the two techniques showed no statistically significant difference. In preoperative corneas, mean epithelial thickness was 50.08+/-3.70 microm in the mechanical debridement group and 50.49+/-4.01 microm in laser-scrape group (not significant). For both groups, the epithelium was significantly thinner at 3 weeks, but returned to preoperative values by 6 months, with no difference between groups. Planned stromal ablation depth by PRK was 59.38+/-11.48 microm (39-73 microm; n = 8) in the mechanical group and 57.75 +/- 7.21 microm (48-70 microm; n = 8) in the laser-scrape group. Achieved stromal ablation depth was not significantly different between the two groups. Most importantly, in both groups CMTF-measured corneal haze increased significantly after surgery, peaked at 3 months, and then decreased at 6 months, with no significant difference between groups. (Power = 0.96).

CONCLUSIONS

There is no significant difference in the corneal wound healing response between mechanical epithelial debridement versus laser-scrape technique in human myopic eyes undergoing PRK.

One-year results of PRK in low and moderate myopia: fewer than 0.5% of eyes lose two or more lines of vision

PURPOSE

To retrospectively evaluate the results of myopic photorefractive keratectomy (PRK) for different levels of intended correction, including analysis of loss of best spectacle-corrected visual acuity.

METHODS

Four hundred seventy-five consecutive eyes with 1 year of follow-up that had PRK for the correction of 1-7 diopters (D) of myopia by using the Summit SVS Apex excimer laser. Three hundred forty-eight eyes were examined at 1 year. This study was confined to the 236 eyes with 1 year of follow-up that had PRK without astigmatic keratotomy. Eyes also were analyzed according to the range of attempted correction (0-3 D, low; 3.1-6D, moderate; and > or =6.1 D, high moderate). Manifest refraction, uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), surface regularity index (SRI), and surface asymmetry index (SAI) were evaluated for each group.

RESULTS

One year after PRK, 91% of all eyes were within 1 diopter and 73% of eyes were within 0.5 diopter of emmetropia. Uncorrected visual acuity was 20/25 or better in 79% and 20/40 or better in 96% of eyes. Two lines of BSCVA were lost in only 0.4% of eyes (one of 236). No eye lost >2 lines of BSCVA, and 30% gained one line. Mean SRI and SAI were increased as compared with preoperative values, but were within the normal range for our patient population (ranges, 0.2-1.0 and 0.1-0.7, respectively). UCVA, BSCVA, and predictability decreased, whereas SAI and SRI increased, with increasing attempted correction.

CONCLUSION

PRK effectively reduced myopia in all eyes with 12 months' follow-up. Predictability tended to decrease with increasing attempted correction, even for low to moderate myopia. PRK may induce mild surface asymmetry and irregularity, and these alterations tend to increase with higher attempted correction. Fewer than 0.5% of eyes lost > or =2 lines of best-corrected visual acuity.