Outcomes of simultaneous photorefractive keratectomy and collagen crosslinking.

OBJECTIVE: To report the outcomes and complications of combined photorefractive keratectomy (PRK) and collagen crosslinking (CXL). DESIGN: A retrospective cohort study of consecutive patients undergoing combined PRK-CXL between 2011 and 2013 at Care Laser, Inc, Tel Aviv, Israel. PARTICIPANTS: Ninety-eight eyes of 56 patients were included. Only patients without keratoconus were included. METHODS: Data were collected from the patients' files and imaging devices. Main outcome measures were corrected and uncorrected distance visual acuity (CDVA/UDVA); spherical equivalent (SE); refractive, keratometric, and pachymetric stability; and the occurrence of postoperative complications. RESULTS: Mean age was 27.69 ± 6.6 years. UDVA improved from 1.38 ± 0.60 to 0.15 ± 0.24 logMAR (p < 0.001). SE improved from -4.45 ± 2.87 diopter (D) to +0.20 ± 0.90 D (p < 0.001), and 69% of the patients were within ±0.50 D from emmetropia. Four eyes had significant corneal haze; of them 3 eyes lost more than 2 Snellen lines. No cases of corneal ectasia were recorded. CONCLUSIONS: In our cohort PRK-CXL achieved significantly improved UDVA and SE compared to baseline. Corneal haze was a significant complication. Refractive results were less accurate than published for patients undergoing PRK procedures. Although no cases of corneal ectasia were seen, given the rarity of such complication, the added benefit of CXL remains to be proven.

Risk Assessment for Corneal Ectasia following Photorefractive Keratectomy.

PURPOSE: To analyze the risk factors associated with a series of ectasia cases following photorefractive keratectomy (PRK) and all published cases. METHODS: In a retrospective study on post-PRK ectasia patients, 9 eyes of 7 patients were included, in addition to 20 eyes of 13 patients from the literature. Risk of post-PRK ectasia was calculated using the ectasia risk score system (ERSS) for laser in situ keratomileusis (LASIK) patients. The percent tissue altered (PTA) was also evaluated. RESULTS: ERSS scoring of zero for age, RSB, and spherical equivalent was found in 66%, 86%, and 86% of the eyes, respectively. Pachymetry risk score was 2 in 60% of the eyes and 3 or 4 in 16% of the eyes. Topography risk score was 3 in 41% of the eyes and 4 in 21% of the eyes. Cumulative ectasia risk score was ≥4 (high risk) in 77% of the eyes and ≥3 (medium and high risk) in 86% of the eyes. Average PTA was 23.2 ± 7.0%. All eyes but one had a PTA < 40%. CONCLUSIONS: Preoperative corneal topographic abnormalities and thin corneas may be significant risk factors for developing ectasia following PRK. Post-LASIK ectasia risk scoring also has relevance in the risk for developing post-PRK ectasia.

The effect of laser-assisted in situ keratomileusis on retinal nerve fiber layer measurements obtained with scanning laser polarimetry.

PURPOSE: Scanning laser polarimetry provides indirect measurements of retinal nerve fiber layer thickness by measuring the retardation of polarized laser light as it passes through the retinal nerve fiber layer. Laser-assisted in situ keratomileusis is a refractive technique by which corneal stromal photoablation is achieved by the structural and refractive changes induced by the excimer laser. Both techniques are becoming widely performed and there is some evidence that scanning laser polarimetry measurements are significantly changed after laser-assisted in situ keratomileusis. The authors performed a larger study to determine whether laser-assisted in situ keratomileusis induces predictable and consistent alterations in the measurement of retinal nerve fiber layer thickness. METHODS: Retinal nerve fiber layer thickness measurements using scanning laser polarimetry were performed 1 week before and 1 week after laser-assisted in situ keratomileusis in 30 consecutive eyes (16 patients) undergoing the procedure at The Eye Institute. RESULTS: Mean +/- SD preoperative spherical equivalent refraction was -4.66 +/- 2.40 D, mean ablation depth was 73.0 +/- 36.23 microm, and mean patient age was 40.6 +/- 8.7 years. Six of 12 retinal nerve fiber layer thickness measurements showed significant change (P < 0.05) after laser-assisted in situ keratomileusis. There was no correlation with corneal ablation depth (P > 0.05) for all parameters. CONCLUSION: Laser-assisted in situ keratomileusis significantly affects retinal nerve fiber layer thickness measurements obtained by scanning laser polarimetry. Sequential images should be interpreted with caution and new postoperative baseline images should be obtained.

Laser in situ keratomileusis for residual myopia after photorefractive keratectomy.

PURPOSE: To evaluate the efficacy and safety of laser in situ keratomileusis (LASIK) for myopic regression and undercorrection after photorefractive keratectomy (PRK). SETTING: The Eye Institute, Sydney, Australia. METHODS: Fifty eyes of 32 patients were treated by LASIK for residual myopia following primary PRK. The mean spherical equivalent refraction (SEQ) was -2.92 diopters (D) +/- 1.57 (SD) (range -0.75 to -7.88 D). The mean refractive cylinder was 0.96 +/- 0.74 D (range 0 to 3.50 D). For analysis, the eyes were divided into 2 groups: those with 0 or low corneal haze (Group 1) and those with severe corneal haze (Group 2). In Group 1, the SEQ was -1.99 +/- 0.79 D (range -0.75 to -3.75 D) and in Group 2, -3.77 +/- 1.62 D (range -0.75 to -7.90 D). The procedure was performed using the Chiron Automated Corneal Shaper and the Summit Apex Plus laser. The mean interval between PRK and LASIK was 25 months (range 9 to 59 months). The following parameters were studied before and after LASIK retreatment: SEQ, mean refractive cylinder, uncorrected visual acuity (UCVA), and best corrected visual acuity (BCVA). Complications after LASIK retreatment were evaluated. RESULTS: Six months after LASIK, the mean SEQ in all eyes was -0.65 +/- 0.86 D (range +1.50 to -3.35 D); 70.0% of eyes were within +/-1.00 D of emmetropia and the UCVA was 6/12 or better in 72.5%. The mean SEQ in Group 1 was -0.22 +/- 0.55 D (range -0.88 to -1.50 D) and in Group 2, -0.97+/- 0.92 D (range 0.12 to -3.25 D); the UCVA was 6/12 or better in 94.0% of eyes in Group 1 and in 56.0% in Group 2. No statistically significant between-group difference was found in lines of Snellen acuity lost or gained at 6 months. No eye lost more than 1 line of BCVA. CONCLUSIONS: Laser in situ keratomileusis appears to be a safe, effective, and predictable procedure for treating eyes with 0 or low haze with residual myopia after PRK. It is less predictable in eyes with severe haze.