Visual outcomes after Epi-LASIK and PRK for low and moderate myopia.

PURPOSE: To evaluate visual outcomes following epi-LASIK compared to photorefractive keratectomy (PRK). METHODS: Of a total 294 patients aged ≥21 years, 145 (290 eyes) underwent epi-LASIK and 149 (298 eyes) underwent PRK for low to moderate myopia or myopic astigmatism. Epi-LASIK was performed with the Amadeus II epikeratome (Abbott Medical Optics) and PRK with the Amoils rotary epithelial brush (Innovative Excimer Solutions). All ablations were performed using the same excimer laser system. Outcome measures included intraoperative complications, corneal reepithelialization, postoperative pain, uncorrected distance visual acuity (UDVA), manifest refraction spherical equivalent (MRSE), corrected distance visual acuity (CDVA), corneal haze, and quality of vision. RESULTS: Mean preoperative MRSE was -2.97±1.19 diopters (D) for epi-LASIK versus -2.95±1.06 D for PRK. Complete reepithelialization was achieved by postoperative day 4 in 46.9% of epi-LASIK eyes versus 92.4% of PRK eyes, with superior UDVA at postoperative day 1 in the PRK group (P=.002). Using Fisher exact test, a significantly higher percentage of epi-LASIK eyes compared to PRK eyes achieved 20/15 or better at 1 month (25.8% vs 17.8%, P=.031), 3 months (62.3% vs 49.3%, P=.004), 6 months (77.1% vs 57.9%, P<.001), and 12 months (75.9% vs 61.9%, P=.002). A change in MRSE >0.50 D occurred in 8.4% of epi-LASIK eyes within the 3- and 12-month interval versus 17.7% of PRK eyes (P=.04). No differences were noted between the two procedures in CDVA or clinically significant haze. CONCLUSIONS: Epi-LASIK showed superior refractive efficacy and stability but required more time for wound healing, resulting in inferior early visual outcomes and a tendency to overcorrect higher refractive errors compared to PRK. Both treatments were safe and comparable in terms of pain and haze formation.

Visual and IOP outcomes after PRK in pigment dispersion syndrome.

PURPOSE: To report the results of photorefractive keratectomy (PRK) in patients with pigment dispersion syndrome. METHODS: The pre- and postoperative records of patients with pigment dispersion syndrome who underwent PRK between January 2002 and March 2009 were reviewed. Data for analysis included gender, age, ablation depth, surgical complications, manifest refraction spherical equivalent, uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), intraocular pressure (IOP), central corneal thickness (CCT), cup-to-disc (c/d) ratio, and postoperative complications. RESULTS: Thirty-seven eyes of 19 patients (17 men and 2 women) with a mean age of 37.5 ± 6.9 years were included for review. At final follow-up, mean 404.1±119.5 days postoperative, UDVA was 20/15 or better in 67.6%, 20/20 or better in 91.9%, and 20/25 or better in 100% of eyes; 94.6% of eyes were within 0.50 diopters (D) and 100% were within 1.00 D of emmetropia. Corrected distance visual acuity was unchanged from preoperative in 73% and improved by one line in 27% of eyes. No eye lost 1 or more lines of CDVA. When corrected for change in CCT and curvature, mean postoperative IOP was elevated from baseline (16.7 ± 3.8 mmHg) at 1 month (18.1 ± 4.9 mmHg, P =.044) but unchanged at any other time postoperatively. Two (11%) of 19 patients were steroid responders, requiring a single topical agent until completing the course of steroids. No significant change was noted in mean c/d ratio from baseline (0.35±0.12) to final postoperative (0.35 ± 0.13, P = .99). CONCLUSIONS: Although PRK in patients with pigment dispersion syndrome resulted in excellent UDVA, retention of CDVA, and low incidence of adverse effects 1 to 2 years after surgery, long-term safety and efficacy outcomes of PRK in this cohort remain speculative

Corneal biomechanics following epi-LASIK.

PURPOSE: To evaluate corneal biomechanical changes following epi-LASIK. METHODS: In this prospective study of 51 patients, corneal hysteresis (CH), corneal resistance factor (CRF), and intraocular pressure (IOP) were assessed using the Ocular Response Analyzer (ORA, Reichert Technologies) preoperatively and at 1, 3, 6, and 12 months after epi-LASIK. Repeated measures analysis of variance (ANOVA) was used to compare changes over time (alpha=.05). Intraocular pressure was also measured by Goldmann applanation tonometry. RESULTS: Corneal hysteresis decreased from 10.22±1.65 mmHg preoperatively to 8.17±1.25 mmHg at 1 month, 8.46±1.44 mmHg at 3 months, 8.63±1.31 mmHg at 6 months, and 8.53±1.49 mmHg at 12 months. Corneal resistance factor decreased from 10.01±1.80 mmHg preoperatively to 7.82±1.68, 8.03±1.85, 7.77±1.50, and 7.80±1.66 mmHg at 1, 3, 6, and 12 months, respectively. Repeated measures ANOVA showed a significant change over time for both CH and CRF (P<.0005). All measures of IOP changed significantly over time (P<.0005). CONCLUSIONS: Epi-LASIK resulted in a significant change in CH and CRF postoperatively. Although some recovery occurred over time, CH, CRF, and IOP did not revert to preoperative levels.

Oral gabapentin for photorefractive keratectomy pain.

PURPOSE: To compare the efficacy of oral gabapentin versus placebo for the control of severe pain after photorefractive keratectomy (PRK). SETTING: Center for Refractive Surgery, Walter Reed Army Medical Center, Washington, DC, USA. DESIGN: Randomized masked clinical trial. METHODS: This single-center clinical trial comprised active-duty United States Army soldiers aged 21 years or older having bilateral PRK for myopia with or without astigmatism. Patients received gabapentin 300 mg or placebo 3 times daily for 7 days beginning 2 days before and continuing for 4 days after surgery. Current and maximum pain levels were assessed using the Visual Analog Pain scale 2 hours after surgery and then daily on days 1 through 4. Repeated-measures analysis of variance (ANOVA) was used to compare the current and maximum pain scores over time between the gabapentin group and the placebo group. The Fisher exact test was used to determine whether there was a difference in severe pain (>7/10) between the 2 groups. RESULTS: Forty-two patients received gabapentin and 41 patients, placebo. The repeated-measures ANOVA showed no significant difference between the 2 groups in current pain (P = .84) or in maximum pain over time (P = .35). Oxycodone-acetaminophen use in the gabapentin group was significantly higher than in the placebo group 1 day postoperatively (P = .034). CONCLUSION: When added to a standardized postoperative pain regimen, gabapentin use led to no additional improvement in PRK pain control compared with a placebo at the dose and the time intervals tested.

Scattered ultraviolet emissions during refractive surgery using a high-frequency, wavefront-optimized excimer laser platform.

PURPOSE: To evaluate occupational ultraviolet (UV) exposure during photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK) with the Allegretto Wave Eye-Q 400 Hz excimer laser. SETTING: Walter Reed Center for Refractive Surgery, Washington, DC, USA. METHODS: Intraoperative UV measurements were performed during PRK with epithelial removal using an Amoils brush, PRK with epithelial removal using 20% ethanol, or femtosecond LASIK. A LaserStar power/energy meter with a silicone detector (model PD-10) was used for the measurements. The maximum pulse energy 25.4 cm from the corneal surface was recorded for each surgical procedure. Measurements were evaluated using a worst-case scenario for exposure of operating room personnel, and the results were compared with the occupational exposure limit set by the International Commission on Non-Ionizing Radiation Protection. RESULTS: Measurements were taken during 15 cases of each procedure. The mean maximum exposure was 129.38 nJ/pulse +/- 79.48 (SD) during brush PRK, 69.72 +/- 68.80 nJ/pulse during ethanol PRK, and 29.17 +/- 13.82 nJ/pulse during LASIK. The mean maximum exposure per eye was 0.085 mJ/cm(2), 0.046 mJ/cm(2), and 0.01 mJ/cm(2), respectively. The worst-case cumulative exposure during a heavy workday of 20 patients (40 eyes) was calculated at 3.92 mJ/cm(2), 1.51 mJ/cm(2), and 0.79 mJ/cm(2) for brush PRK, ethanol PRK, and LASIK, respectively. CONCLUSION: Results indicate that the excimer laser platform used in the study may yield greater UV exposure than previous systems; however, the levels did not exceed occupational exposure limits. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

Effect of blast trauma and corneal foreign bodies on visual performance.

PURPOSE: To evaluate the effect of non-penetrating corneal foreign bodies secondary to explosive blasts on the visual performance of soldiers. METHODS: In a prospective, non-interventional study subjective visual performance and objective optical quality of 11 injured eyes with retained corneal foreign bodies were compared with that of 11 normal controls. Visual performance measures consisted of best spectacle-corrected high-contrast visual acuity (HCVA), low-contrast (5%) visual acuity (LCVA), and contrast sensitivity (CS). LCVA was evaluated in two luminance levels (photopic and mesopic) and two glare conditions (with and without glare). Acuity measurements were scored using logMAR notation. Objective optical quality was assessed comparing total root mean square wavefront error (WFE) and percent higher order aberrations. Modulation transfer functions calculated from the wavefront maps were used to predict the results of the psychophysical contrast testing. RESULTS: HCVA of injured eyes (M = -0.03) did not differ significantly (t(20) = 1.56, p = 0.13) when compared with controls (M = -0.09). However, visual performance of injured eyes (M = 0.33) was significantly worse than control eyes (M = 0.11) on photopic LCVA (t(20) = 4.16, p < 0.001), mesopic LCVA(M = 0.44 vs. M = 0.21, t(20) = 3.85, p = 0.001), mesopic LCVA with glare (M = 0.49 vs. M = 0.21, t(20) = 3.66, p = 0.002), and small letter CS (M = 0.25 vs. M = 0.90, t(20) = -6.6, p < 0.001). For a 6-mm pupil, mean absolute WFE attributed to higher order aberrations for the injured eyes was 0.86 microm and 0.59 microm for the control eyes. This difference was significant (t(20) = -2.15, p = 0.044). CONCLUSIONS: Although HCVA was no different than the normal controls, visual performance of the injured eyes was significantly worse in terms of LCVA and CS. On average, visual performance can be broadly predicted by the modulation transfer function derived from the subjects' wavefront aberration map.