Photorefractive Keratectomy Enhancement Research Articles

Corneal Epithelial Remodeling Induced by Photorefractive Keratectomy Enhancement After Small-Incision Lenticule Extraction.

To assess changes in corneal epithelial thickness (ET) within 9-mm diameter cornea after photorefractive keratectomy (PRK) retreatment after small-incision lenticule extraction (SMILE). A total of 28 eyes of 19 patients with mean spherical equivalent of -1.30 ± 0.60 D who underwent retreatment after SMILE were included in this retrospective study. ET mapped across a 9-mm diameter area was obtained using wide-field optical coherence tomography (OCT) before and at one, three, and six months after surgery. The ET changes were compared between the different time points and analyzed zones. Before enhancement, the ET were 63.64 ± 6.01 µm and 61.25 ± 4.32 µm in central and paracentral zones, respectively. The ET of central and paracentral zones significantly decreased at one month and subsequently increased until six months. Six months after surgery, significant epithelial thickening occurred in 2- to 9-mm diameter cornea (all P < 0.05), whereas no significant change was observed in central 2-mm diameter cornea (P = 0.460). There was no significant difference in the ET between the central and paracentral zones (P = 1.00). The degree of myopic correction significantly correlated with the average ET in the central (P = 0.046) and paracentral (P = 0.033) zones at six months after PRK enhancement. No significant correlation was detected between the average ET of all zones and the postoperative spherical equivalent at six months after surgery (all P > 0.05). PRK enhancement did not alter the overall trend of corneal epithelial remodeling induced by SMILE. An asymmetric and flatter lenticule-like pattern of epithelial remodeling was observed six months after surgery, which did not affect the refractive outcomes. An asymmetric and centrally flattened lenticule-like pattern of epithelial remodeling was observed after PRK enhancement. Surgeons should consider expanding the intended optical zones for enhancement surgery after SMILE.

Use of primary and piggyback toric intraocular lenses for treatment of high myopic astigmatism

Introduction: High myopic astigmatism often presents a challenge for cataract surgeons. Procedures such as limbal relaxation incisions may also be impossible in the setting of an extensive refractive surgical history. Patient and Clinical Findings: A 61-year-old woman for cataract surgery with a history of automated lamellar keratoplasty, 4-incision radial keratotomy, and arcuate incisions in the left eye. Astigmatism was 8.00 diopters (D) by manifest refraction, and on optical biometry, corneal topography, and auto keratometry, astigmatism was 9.01 D, 7.52 D, and 8.25 D, respectively. Diagnosis, Intervention, and Outcomes: A primary in-the-bag toric intraocular lens (IOL) and piggyback toric IOL with reverse optic capture were used. A surgically induced astigmatism of 6.59 D, magnitude of error of −1.41 D, angle of error 5.6 degrees, and correction index of 0.82 were achieved. Owing to limited potential improvement with IOL rotation, additional enhancement with photorefractive keratectomy (PRK) of −0.61 −1.78 × 69 degrees was performed to achieve desired results and high patient satisfaction. Preoperative corrected distance visual acuity was 20/50, and the uncorrected visual acuity achieved after cataract surgery and PRK enhancement was 20/25. Conclusions: The use of double toric IOLs for treating high astigmatism in patients with prior keratorefractive surgery is reported.

Outcomes of LASIK vs PRK enhancement in eyes with prior cataract surgery.

To compare postenhancement visual acuity between patients who underwent postcataract laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK). A private, tertiary referral practice in Sioux Falls, South Dakota. 3-year, retrospective chart review. Patients who underwent postcataract extraction excimer laser enhancement surgery targeted for emmetropia (±0.50 diopter). Postenhancement uncorrected distance visual acuity (UDVA) and manifest refraction spherical equivalent (MRSE) was recorded for all available follow-ups and compared for both groups. 822 postcataract enhanced eyes (491 LASIK; 331 PRK). For patients with at least 6-month follow-up, mean UDVA was 0.05 ± 0.13 logMAR in LASIK-enhanced patients and 0.15 ± 0.20 in PRK-enhanced patients ( P < .001). Mean absolute value MRSE was 0.22 ± 0.36 and 0.48 ± 0.62 for LASIK-enhanced and PRK-enhanced patients at or beyond 6 months, respectively ( P < .001). 330 (67%) LASIK-enhanced patients achieved 20/20 or better postenhancement UDVA, compared with 142 (43%) PRK-enhanced patients ( P < .001). Controlling for pre-enhancement UDVA, LASIK-enhanced patients showed significantly better postenhancement UDVA than PRK-enhanced patients, except in those with pre-enhancement vision of 20/20 or better, or those worse than 20/50. LASIK-enhanced virgin corneas had mean postenhancement of 0.05 ± 0.14 UDVA compared with 0.13 ± 0.19 UDVA in PRK-enhanced virgin cornea patients ( P < .001). LASIK provides better and more predictable outcomes in UDVA than PRK in postcataract enhancement patients, even when controlling for pre-enhancement visual acuity and prior ocular procedures.

Visual Outcomes of Photorefractive Keratectomy Enhancement After Primary LASIK.

To evaluate the safety, efficacy, and predictability of photorefractive keratectomy (PRK) at least 4 years after primary laser in situ keratomileusis (LASIK) and compare it to the United States Food and Drug Administration (FDA) criteria. This retrospective, single-site study compared patients who underwent PRK enhancement from 2014 to 2019 after primary LASIK to those who only underwent primary LASIK without re-treatment from the same time period. Patient demographics and clinical information were compared between the two groups. Visual outcomes and postoperative complications were evaluated in the enhancement group. A total of 374 eyes with PRK enhancement were compared to 472 without re-treatment. Age, sex, surgical eye, and preoperative sphere, and spherical equivalent (SE) were significantly different between the enhancement and control groups (P < .05). At 12 months post-enhancement, 67% had uncorrected distance visual acuity (UDVA) of 20/20 or better, 98% had UDVA of 20/40 or better, and 0.4% of eyes lost at least two lines of corrected distance visual acuity (CDVA). A total of 83% and 98% of eyes were within ±0.50 and ±1.00 diopters of the target, respectively. Post-enhancement complications (n = 66) included dryness (6.1%), epithelial ingrowth (2.7%), and haze (2.7%). Older age at the time of the primary LASIK, female sex, right surgical eye, and more myopic sphere and SE were risk factors for enhancement. Although PRK enhancements are considered off-label procedures, they produce favorable outcomes at 3 and 12 months postoperatively while meeting FDA benchmarks for safety, efficacy, and predictability. [J Refract Surg. 2022;38(11):733-740.].

Photorefractive Keratectomy Enhancement (PRK) After Small-Incision Lenticule Extraction (SMILE).

PurposeTo determine rates of enhancement and visual prognosis following photorefractive keratectomy (PRK) enhancement of small-incision lenticule extraction (SMILE).Patients and MethodsThis retrospective, single-site study reviewed all cases of primary SMILE at Hoopes Vision in Draper, Utah between March 14, 2017 and April 8, 2022 to identify any cases that required follow-up enhancement. Primary SMILE was performed using Visumax 500 kHz femtosecond laser (Carl Zeiss Meditec, Jena, Germany). All enhancements were performed with alcohol-assisted PRK, using a WaveLight EX500 excimer laser (Alcon Laboratories, Inc., Fort Worth, TX).ResultsFour hundred and five eyes underwent primary SMILE, of which 15 later underwent PRK enhancement (enhancement rate of 3.7%). No significant difference in pre-SMILE data was identified between the enhancement and non-enhancement groups. The average age of those who underwent PRK enhancement was 33.8±6.3 years old and ranged from 25 to 45. Following primary SMILE, 13 eyes (87%) had an uncorrected distance visual acuity (UDVA) of 20/40 or better, and none had a UDVA of 20/20 or better. After one year of post-enhancement follow-up, all eyes had a UDVA of 20/40 or better, and 13 eyes (87%) had a UDVA of 20/20 or better (Figure 1). All were within one diopter of target spherical equivalent (SEQ), 13 (87%) were within 0.50 D, and 10 (67%) were within 0.25 D. Of those with 12-month follow-up data, none had UDVA worse than corrected distance visual acuity (CDVA), and none had lost lines of CDVA. Efficacy and safety indices were 1.03 and 0.99, respectively.ConclusionFollowing SMILE, ophthalmologists may anticipate an enhancement rate of one to seven percent. In these cases, PRK is a safe and effective procedure for enhancement of SMILE.

PRK Enhancement for Residual Refractive Error After Primary PRK: A Retrospective Study.

IntroductionThe efficacy and safety of photorefractive keratectomy (PRK) has been well documented, but outcomes of PRK enhancement following PRK remain understudied. This study aimed to evaluate the safety, efficacy, and predictability of PRK enhancement in patients with residual refractive error after primary PRK and compare these results to prior studies as well as Food and Drug Administration (FDA) safety and efficacy clinical endpoints.MethodsThis non-randomized, retrospective chart analysis included eyes with a history of PRK that underwent PRK enhancement at a single center. Post-enhancement data were documented at 3-month and 1-year visits. Patient characteristics between the study group and a control group who underwent primary PRK only were compared. Safety and efficacy measures included change in uncorrected distance visual acuity (UDVA), change in corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), amount of induced astigmatism, and presence of serious adverse events.ResultsA total of 188 eyes from 141 patients were included. When compared to the control group, women underwent PRK enhancement at a higher rate than men (P = 0.004). The group undergoing PRK enhancement had a higher sphere (P = 0.013) and spherical equivalent (P = 0.004) than the control group at the time of primary PRK. MRSE was reduced to − 0.97 ± 0.72 D (− 2.25 to + 2.13 D) from pre-enhancement values of − 0.98 ± 0.66 D (− 2.75 to + 1.75 D) and stable over 12-month visits with 86% and 98% of eyes within ± 0.50 D and ± 1.00 D of target, respectively. UDVA of 20/20 or better was achieved in 75% of eyes. The UDVA of 75% of eyes remained the same or improved by 1 or more Snellen lines compared with pre-enhancement CDVA.ConclusionOur results demonstrate that, when compared with previous studies, modern PRK enhancement after PRK has improved visual acuity and refractive outcomes. Though PRK enhancement is not an FDA approved procedure, we show that it meets or exceeds the FDA criteria for the correction of refractive error.

Estratégia de tratamento para fibrose subepitelial grave bilateral após aprimoramento com ceratectomia fotorrefrativa

ABSTRACT A 27-year-old healthy man with a history of bilateral photorefractive keratectomy (PRK) enhancement after femtosecond laser in situ keratomileusis (LASIK) presented with decreased uncorrected distance visual acuity (UDVA) of 20/125 in the right eye (OD) and 20/300 in the left eye (OS) six months after PRK. Examination revealed bilateral dense subepithelial opacities. Both eyes (OU) were treated with superficial keratectomy combined with phototherapeutic keratectomy (PTK) and adjunctive application of mitomycin C 0.02%. At three months follow up UDVA was 20/30 OD and 20/25 OS. Superficial keratectomy combined with PTK seems to be a safe and efficient technique for treatment of dense subepithelial scar formation following PRK enhancement after LASIK.

Stromal scar in a laser in situ keratomileusis flap after photorefractive keratectomy enhancement: June consultation #1

Stromal scar in a laser in situ keratomileusis flap after photorefractive keratectomy enhancement: June consultation #1

Etiology and outcomes of secondary surgical intervention for dissatisfied patients after pseudophakic monovision.

To evaluate the etiology and the clinical outcomes of secondary surgical interventions for dissatisfied patients after pseudophakic monovision. Department of Ophthalmology, Kitasato University Hospital, Kanagawa, Japan. Retrospective case series. This study comprised 12 eyes in 12 patients (age 66.2±5.6years) who underwent photorefractive keratectomy (PRK) enhancement to improve their dissatisfaction after pseudophakic monovision. We quantitatively assessed the visual and refractive outcomes and the subjective satisfaction measured using a visual analog scale, that ranged from 0 (very dissatisfied) to 10 (very satisfied), before and 3months after PRK enhancement. Six (50%) of the 12 patients were dissatisfied with their various distance visions because of a large amount of anisometropia (≥2.50D). Two (16.7%) were dissatisfied with their distance vision after conventional monovision because of residual cylindrical errors (≥0.75D) in the dominant eye. Three (25%) was an unknown origin. The remaining one of the 12 patients was dissatisfied due to the unadaptability to crossed monovision. Eleven (91.7%) eyes were within ±0.5D of the targeted correction after PRK enhancement. The overall satisfaction score was significantly improved, from 3.7±2.4 (range 0-7) preoperatively to 6.0±2.4 (range 2-9) postoperatively (p=0.02). No vision-threatening complications were seen throughout the observation period. PRK enhancement was effective with predictable refractive results and thus improved patient satisfaction for dissatisfied patients after pseudophakic monovision. These findings also suggest that the accurate correction of refractive errors plays a key role in successful pseudophakic monovision.

Biomechanical Weakening of Different Re-treatment Options After Small Incision Lenticule Extraction (SMILE).

To determine the corneal weakening induced by different re-treatment options after small incision lenticule extraction (SMILE) and investigate the potential of corneal cross-linking (CXL) to reestablish the original corneal stress resistance. A total of 96 freshly enucleated porcine corneas were used. The initial refractive correction was defined to be -11.00 diopters (D) and the required enhancement to be -3.00 D. Three different re-treatment options were analyzed: -3D Re-SMILE, -3D photorefractive keratectomy (PRK) on top of the SMILE cap, and cap-to-flap conversion and -3D excimer ablation on the stromal bed (LASIK). The control condition did not receive any treatment. Subsequently, accelerated CXL (9 mW/cm2, 10 min) was performed in two groups with currently common enhancement techniques: following cap-to-flap conversion (-3D LASIK enhancement) and in controls. Biomechanical properties were measured with stress-strain extensometry ranging from 1.27 to 12.5 N. The Re-SMILE and PRK enhancement did not significantly reduce the overall elastic modulus of the cornea compared to controls (24.7 ± 2.23 and 22.7 ± 2.61 versus 23.8 ± 3.35 MPa, P ≥ .176), whereas LASIK enhancement did (22.2 ± 3.37 MPa, P = .048). CXL treatment significantly increased the elastic modulus compared to all non-cross-linked conditions (P ≤.001). Refractive surgery decreased the overall elastic modulus by 7%, whereas CXL increased it by 20%. In enhancement, the corneal biomechanical integrity is less affected with both Re-SMILE and PRK enhancement. Corneal weakening through laser refractive surgery is small compared to the stiffening effect after CXL. [J Refract Surg. 2017;33(3):193-198.].

Outcomes of photorefractive keratectomy enhancement after LASIK.

To report the outcomes of photorefractive keratectomy (PRK) enhancement after LASIK for patients diagnosed as having hyperopic and myopic refractive errors. In this retrospective case series at a single private practice in the United States, all patients undergoing PRK enhancement after LASIK were identified. Patients with visually significant cataract, non-plano targets, and follow-up of fewer than 226 days were excluded. The primary outcome measure was uncorrected distance visual acuity (UDVA) with secondary measures of corrected distance visual acuity (CDVA) and postoperative refractive error. Linear regression analysis was performed for actual versus targeted change in spherical equivalent. Mean UDVA improved from 20/39 to 20/24 for hyperopes (n = 14; P < .002) and from 20/45 to 20/22 for myopes (n = 29; P < .0000001) after enhancement. All patients had a UDVA of 20/40 or better at their most recent follow-up visit. Fifty percent of hyperopes and 65.5% of myopes were 20/20 or better. The mean refractive error for hyperopes changed from +1.10 ± 0.71 (range: +0.13 to +2.25 diopters [D]) to +0.38 ± 0.66 D (range: -0.75 to +1.38 D) and from -1.21 ± 0.61 (range: -3.25 to -0.38 D) to +0.34 ± 0.45 D (range: -0.25 to +1.75 D) for myopes. The manifest refraction cylinder decreased from 0.84 to 0.46 D in hyperopes (P = .02) and from 0.64 to 0.26 D in myopes (P < .002). CDVA was maintained in both groups, with only one patient in each worse than 20/20. There was a nonsignificant trend toward less haze in the patients receiving mitomycin C (5.1% vs 25%, P = .14). Linear regression showed a tendency toward overtreatment in the myopic group. PRK is safe and highly effective for patients who previously underwent LASIK and in whom the surgeon would prefer not to perform a flap-lift enhancement.

Photorefractive Keratectomy with Adjunctive Mitomycin C for Residual Error after Laser-Assisted In Situ Keratomileusis Using the Pulzar 213 nm Solid-State Laser: Early Results

Purpose. To evaluate the accuracy, efficacy, stability, and safety of photorefractive keratectomy (PRK) enhancement using the Pulzar 213 nm solid-state laser (SSL) with adjunctive Mitomycin C in eyes previously treated with laser assisted in situ keratomileusis (LASIK) with residual error of refraction. Methods. This is a prospective noncomparative case series of 16 eyes of 12 patients who underwent PRK for residual refractive error after primary LASIK. Mitomycin C 0.02% was used after the PRK to prevent haze formation. Outcomes measured were pre- and postoperative manifest refraction spherical equivalent (MRSE), uncorrected (UDVA) and best-corrected distance visual acuity (CDVA), and slit lamp evidence of corneal complications. Results. The mean UDVA improved from 20/70 preoperatively to 20/30 postoperatively. The average gain in lines for the UDVA was 2.38. After six months of followup, the postoperative MRSE within 0.50 D in 56% (9) of eyes and 94% (15) eyes were within 1.0 diopters of the intended correction. No eyes developed haze all throughout the study. Conclusion. PRK enhancement with adjunctive use of Mitomycin C for the correction of residual error of refraction after LASIK using the Pulzar 213 nm solid-state laser is an accurate, effective, and safe procedure.

Corneal wavefront-guided photorefractive keratectomy in patients with irregular corneas after corneal refractive surgery

To evaluate the corrective potential of corneal wavefront-guided photorefractive keratectomy (PRK) in patients with high levels of corneal aberrations and symptoms after previous corneal refractive surgery. Vissum-Instituto de Oftalmológico de Alicante, Alicante, Spain. This study comprised 25 eyes (20 patients) that had 1 or more previous unsuccessful keratorefractive procedure. All eyes had PRK retreatment using the Esiris excimer laser and ORK-CAM software for customized ablation design. All eyes had a high preoperative level of corneal higher-order aberrations (HOAs) (coma-like or spherical-like root mean square [RMS] >0.5 microm). Changes in refractive outcomes, subjective symptoms, and corneal aberrometry were evaluated during a 6-month follow-up. Uncorrected visual acuity improved significantly from preoperatively (mean 0.48) to 6 months after retreatment (mean 0.75) (P<.01). The mean best spectacle-corrected visual acuity (BSCVA) also improved significantly, from 0.78 to 0.90, respectively (P<.01). Forty-four percent of patients gained 1 or more lines of BSCVA. The reduction in cylinder at 6 months was statistically significant (P= .01). Corneal aberrometry at 6 months showed a statistically significant reduction in total (P= .01), spherical-like (P<.01), coma-like (P= .02), and primary coma (P<.01) RMS. At 6 months, 72% of patients had low or no perception of halos and all reported no glare. Corneal wavefront-guided PRK enhancement with the ORK-CAM system minimized corneal HOAs in eyes with previous unsuccessful keratorefractive surgery.

Photorefractive keratectomy for the correction of residual refractive error with Intacs intrastromal corneal ring segments in place

To evaluate the efficacy and safety of photorefractive keratectomy (PRK) for residual refractive errors in patients who had previous insertion of intrastromal corneal ring segments (Intacs, Addition Technology, Inc.) for treatment of low myopia. Shiley Eye Center, University of California San Diego, La Jolla, California, USA. This retrospective case series comprised patients who had Intacs segment implantation and subsequently developed myopic regression. Eight eyes of 5 patients had PRK over the Intacs in situ for the correction of the residual refractive error. Six (75%) of the 8 eyes had plano refraction with 20/20 or better uncorrected visual acuity (UCVA) 1 month after PRK enhancement. Three months postoperatively, all eyes had plano refraction with 20/20 or better acuity. At the last follow-up examination (up to 2 years), all eyes had near plano vision (20/10 to 20/25). The corneal surface epithelium in all eyes healed in 3 to 5 days. One patient had subepithelial haze in both eyes, which resolved with epithelial scraping with mitomycin-C (MMC) application and a phototherapeutic keratectomy enhancement. This small series showed that PRK can be used to treat residual refractive error after Intacs insertion. The UCVA was 20/25 or better in all cases after PRK enhancement. The incidence of post-PRK haze in this series of patients was high; topical MMC might be used in future cases to mitigate the problem.

Management of Irregular Astigmatism Following Rotationally Disoriented Free Cap After LASIK

To illustrate the challenges associated with a misaligned free flap (cap) and to report the outcome of applying wavefront-guided customized photorefractive keratectomy (PRK) followed by conventional PRK ablation to correct residual refractive error and aberrations after LASIK free cap complications. The clinical course and surgical interventions of two patients with free cap complications from LASIK surgery were reviewed. The first patient underwent a total of six interventions after the initial LASIK procedure, and the second patient underwent a total of five interventions. Interventions included cap lift, cap rotation, custom PRK, and conventional PRK enhancement with prophylactic topical mitomycin C (MMC). Customized PRK treatment and subsequent enhancements with prophylactic topical MMC led to the recovery of best spectacle-corrected visual acuity (BSCVA), neutralization of higher and lower order aberrations, and astigmatic neutrality. Symptoms related to higher order aberrations resolved in both patients. Wavefront-guided custom PRK for higher order aberrations followed by conventional PRK enhancement for residual lower order aberrations, both with topical MMC application, represents an efficacious strategy for treating patients with loss of BSCVA and visual symptoms due to LASIK free cap complications.

Secondary procedures after presbyopic lens exchange

Purpose: To assess the indications, incidence, and outcome of secondary procedures after presbyopic lens exchange (PRELEX). Setting: Private practice, Siena, Italy. Methods: This prospective nonrandomized single-surgeon study comprised 52 patients having PRELEX by phacoemulsification and multifocal intraocular lens (IOL) implantation. The preoperative mean spherical equivalent (SE) was +2.50 diopters (D) ± 1.38 (SD) (range 0 to +6.0 D). Results: Monocular PRELEX was performed in 8 patients who canceled the fellow-eye surgery because of halos; in this group, the residual refractive error was corrected by photorefractive keratectomy (PRK) in 4 eyes, but this did not alleviate halos and IOL exchange was ultimately needed in 7 eyes. Binocular PRELEX was completed in 44 patients; in this group, 14 eyes (8 patients) had PRK for a residual error. The postoperative mean absolute SE in the 18 PRK-treated eyes was 0.33 D (95% confidence interval [CI] of improvement, 0.57-1.32) and the mean uncorrected visual acuity, 0.8 (95% CI of improvement, 0.32-0.45). The final SE was within ±0.5 D in 15 eyes (83.0%) and within ±1.0 D in 18 eyes. Halos after PRK were unchanged in 6 patients, slightly improved in 4, and improved in 2. Photorefractive keratectomy or IOL exchange was needed in eyes with a preoperative SE between plano and +1.75 D (15/40 eyes, 38%) and not needed in eyes with a preoperative SE greater than +1.75 D (0%) (95% CI of difference, 23%-53%). Conclusions: Presbyopic lens exchange in eyes with emmetropia and low hyperopia was associated with a significantly higher percentage of secondary procedures. Photorefractive keratectomy enhancement can improve distance vision but has a limited effect on halos.

Arcuate Transverse Keratotomy Remains a Useful Adjunct to Correct Astigmatism in Conjunction With Photorefractive Keratectomy

To retrospectively evaluate the effectiveness of paired, arcuate transverse keratotomy (Arc-T) performed prior to or after photorefractive keratectomy (PRK) to correct low to moderate amounts of natural or laser-induced astigmatism. Spherical PRK was performed in 730 eyes for myopia of -1.00 to -7.00 D. PRK with arcuate transverse keratotomy was performed in 150 of these eyes; we studied 123 eyes that did not have PRK enhancement. Arc-T was performed prior to PRK in all 37 study eyes with astigmatism of 1.50 D or more at the preoperative examination. Arc-T keratotomy was performed after PRK in 86 study eyes for residual astigmatism of +0.75 D or more and uncorrected visual acuity of 20/30 or worse. Arc-T before PRK group: PRK was performed at a mean 1.0 +/- 1.5 months after Arc-T. Mean astigmatism decreased from +2.40 +/- 0.6 D (range, 1.00 to 4.00 D) before Arc-T to 0.60 +/- 0.60 D (range, 0 to 2.25 D) after Arc-T (P < .0001). Net change in astigmatism was 1.80 +/- 0.60 D (range, 0.80 to 2.80 D) and mean reduction was 75%. Spherical equivalent refraction changed from -4.10 +/- 1.90 D (range, -0.25 to -8.10 D) to -4.40 +/- 1.80 D after Arc-T (P = .002). Mean change in spherical equivalent refraction after Arc-T was -0.30 +/- 0.50 D (range, -1.10 to +0.40 D). Arc-T after PRK group: Arc-T was performed at a mean 3.5 +/- 1.9 months after PRK. Six months after Arc-T, astigmatism was decreased from +1.50 +/- 0.60 D to 0.40 +/- 0.40 D (P = .04). Net change in astigmatism at 6 months was 1.10 +/- 0.60 D and mean reduction was 74%. Vector change in astigmatism magnitude was 1.30 +/- 0.60 D (range, 0 to 4.00 D) at 6 months and vector change in astigmatism axis was 65 degrees +/- 68 degrees. Spherical equivalent refraction did not change when Arc-T was performed after PRK for eyes with low astigmatism (P = .4). Arc-T retreatment was performed in 6 of 37 (16%) eyes that had Arc-T before PRK and 18 of 86 (21%) eyes that had Arc-T after PRK (P = .12). Arcuate transverse keratotomy performed prior to PRK for high astigmatism or after PRK for lower levels of residual astigmatism effectively improved visual outcome. Coupling was less predictable for high levels of astigmatism correction with Arc-T.

Photorefractive keratectomy retreatments: Comparison of two methods of excimer laser epithelium removal

Background Regression and undertreatment after initial photorefractive keratectomy (PRK) in higher myopes is not unusual. Patients frequently desire 20/20 uncorrected vision, which necessitates retreatments or enhancements. However, the safest and most efficacious way to treat these patients has not yet been established. This study evaluates two techniques of PRK enhancements, comparing two different methods of laser epithelial removal. Design Retrospective, nonrandomized, comparative trial. Participants A total of 224 eyes. Methods Eyes were identified that had 6-month follow-up after a PRK enhancement from February 1995 through February 1997. Two methods of treatment were identified. The same VISX 20/20B laser in the same clinic was used for all retreatments. Group I patients had a total removal of the epithelium in a mode phototherapeutic keratectomy (PTK) prior to the refractive ablation. Group II patients had a total laser epithelial removal in two steps prior to the refractive ablation. The first step was a PRK and then a PTK. Main outcome measure The disappearance of epithelial fluorescence was the end point for the PTK ablation in groups I and II. Results There were 131 eyes in group I and 93 eyes in group II. The mean spherical equivalent (SE) prior to the original PRK in group I was −7.5 diopters (D) ± 3 D and in group II was −7.75 D ± 2.34 D. The mean SE prior to the PRK retreatment in group I was −2.22 D ± 1.29 D and in group II was −1.89 D ± 0.83 D. The mean postoperative 6-month SE after the PRK enhancement in group I was −0.05 D ± 0.80 D and in group II was 0.01 D ± 1.08 D. A greater proportion of group I eyes (7.8%) had arcuate haze and a hyperopic shift from the 1- to 6-month postoperative visit ( P = 0.03). Conclusions A two-step laser epithelial removal compared with a one-step PTK epithelial laser removal in PRK retreatments provides a more even and confluent epithelial removal, less risk of arcuate haze development, and less risk of a hyperopic shift from 1 to 6 months after the retreatment.