Custom Photorefractive Keratectomy Research Articles

Topography-Guided Custom Photorefractive Keratectomy for Myopia in Primary Eyes With the WaveLight EX500 Platform.

To evaluate the outcomes after topography-guided ablation treatment (T-CAT) for the correction of myopia and myopic astigmatism with photorefractive keratectomy (PRK). This was a retrospective, non-comparative case series study of 25 patients (40 eyes) with low to moderate myopia with or without astigmatism who underwent topography-guided custom PRK with the Wave-Light EX500 excimer laser platform (Alcon Laboratories, Inc., Fort Worth, TX). The customized treatment plan was based on Topolyzer Vario topography system (Alcon Laboratories, Inc.) data. The patients were observed for 6 months after the procedure. The surgery significantly reduced the manifest refractive spherical equivalent (MRSE), sphere, and cylinder (P < .05) at 6 months of follow-up. Compared with the preoperative corrected distance visual acuity (CDVA), 8 (20%) and 10 (25%) of 40 eyes gained one or more lines of postoperative uncorrected distance visual acuity at 3 and 6 months, respectively. Only 1 eye presented loss of one line of CDVA at 6 months postoperatively, which was due to delayed epithelial healing. Ten patients (15 eyes) reported symptoms related to dry eye and the vision of 21 patients (17 eyes) fluctuated during the first month. The T-CAT custom PRK procedure provided good early outcomes for treating patients with low to moderate myopia with or without astigmatism. [J Refract Surg. 2018;34(8):541-546.].

Customized photorefractive keratectomy to correct high ametropia after penetrating keratoplasty: A pilot study

PurposeTo evaluate preliminarily the safety and efficacy of customized photorefractive keratectomy (PRK) to correct ametropia and irregular astigmatism after penetrating keratoplasty (PK). MethodsThis pilot study included five eyes of five patients with a mean spherical equivalent of −5.1±1.46D (range from −2.75 to −6.50D). In all cases, ametropia and irregular astigmatism was corrected with topography-guided customized PRK. Ocular examinations with topographic analysis were performed preoperatively as well as at 1, 3 and 6 months after surgery. ResultsAll eyes gained postoperatively at least three Snellen lines of uncorrected visual acuity. Mean refractive spherical equivalent was 0.62±0.63D (range from −0.25 to −1.75D) at 6 months postoperatively. ConclusionOur pilot study suggests that customized PRK can be a safe and effective method for treating ametropia and irregular astigmatisms after PK. Future studies with larger samples and longer follow-ups should be performed to confirm these results.

Custom vs Conventional PRK: A Prospective, Randomized, Contralateral Eye Comparison of Postoperative Visual Function

To determine whether VISX S4 (VISX Inc) custom photorefractive keratectomy (PRK) results in better visual outcomes than VISX S4 conventional PRK. Photorefractive keratectomy was performed on 80 eyes from 40 patients in this randomized, prospective, contralateral eye study. Dominant eyes were randomized to one group with the fellow eye receiving the alternate treatment. Primary outcome measures included uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), contrast sensitivity, and root-mean-square (RMS) higher order aberrations. Mean UDVA was -0.023±0.099 (20/19) in the custom group and -0.044±0.080 (20/18) in the conventional group 6 months after surgery (P=.293). Mean CDVA was -0.073±0.067 (20/17) in the custom group and -0.079±0.071 (20/17) in the conventional group 6 months after surgery (P=.659). Total higher order aberration RMS and spherical aberration increased in both groups compared to preoperative values (P<.05). Coma increased in the conventional group (P<.05) whereas it was similar to preoperative values in the custom group. No significant differences were noted in induction of trefoil. Custom and conventional PRK were shown to be safe and effective with excellent visual acuity and contrast sensitivity performance at 6 and 12 months. Conventional PRK induced more coma than custom PRK; however, this did not seem to correlate with clinical outcomes.

Posterior Linear Stromal Haze Formation after Simultaneous Photorefractive Keratectomy followed by Corneal Collagen Cross-linking

To report the development of posterior linear stromal haze after simultaneous photorefractive keratectomy (PRK) followed by corneal collagen cross-linking (CXL). Combined simultaneous customized PRK followed by corneal collagen cross-linking was performed in 23 patients (28 eyes) with keratoconus. Corneas were examined biomicroscopically and by means of confocal microscopy before surgery and 1, 3, 6, 9, and 12 months after surgery. Posterior linear stromal haze was observed clinically (slit lamp biomicroscopy) one month after surgery in 13 of 28 eyes (46.42%). No corneal edema or anterior haze formation was evident. Confocal microscopy revealed in those 13 eyes a hyperreflective area at the level of the posterior stroma 1 month after combined treatment. Both slit lamp examination and corneal confocal microscopy follow-up demonstrated a gradual anterior movement and a decrease in reflectance of this finding. At 12 months this posterior linear stromal haze, despite its anterior movement and decreased density, did not completely disappear at slit lamp and confocal microscopy analysis. Posterior linear stromal haze formation may appear after simultaneous PRK followed by CXL in patients with keratoconus. This finding seems to gradually become less dense and slowly moves toward the anterior stroma.

Conventional versus custom ablation in photorefractive keratectomy: Randomized clinical trial

To compare visual outcomes and changes in total higher-order aberrations (HOAs) between conventional photorefractive keratectomy (PRK) and custom PRK SETTING: Department of Ophthalmology, Labbafinejad Medical Center, Ophthalmic Research Center, Shahid Beheshti University of Medical Sciences and Negah Eye Center, Tehran, Iran. This clinical trial comprised eyes having bilateral myopic PRK with the Technolas 217z excimer machine. One eye had conventional ablation (conventional group) and the other eye, wavefront-guided custom treatment (custom group). Changes in postoperative visual acuity, cycloplegic refraction, contrast sensitivity function, and root mean square higher-order aberrations (RMS HOAs) were compared between the 2 groups. The mean age of the 28 patients (56 eyes) was 26.7 years. The mean preoperative cycloplegic spherical equivalent refractive error was -4.92 diopters (D) +/- 1.6 (SD) and the mean refractive astigmatism, 0.91 +/- 1.0 D. There was no statistically significant difference between the 2 groups in preoperative cycloplegic refractive error, HOAs, or contrast sensitivity function. The mean follow-up was 8.1 +/- 3.3 months. The increase in RMS HOAs from preoperatively to postoperatively was statistically significantly higher in the custom group in the 6.0 mm zone (P = .03) but not in the 4.0 mm zone (P = .26). The decrease in low mesopic contrast sensitivity function was statistically significant in both groups. The RMS HOAs significantly increased after PRK with both methods. The results suggest that custom ablation is more sensitive to optical zone (OZ) size and may yield more aberrations with an OZ smaller than 6.0 mm.

Aspheric Profile versus Wavefront-Guided Ablation Photorefractive Keratectomy for the Correction of Myopia using the Allegretto Eye Q

To compare the results of photorefractive keratectomy (PRK) with Q-factor customized aspheric ablation and wavefront-guided customized ablation for correction of myopia compound with astigmatism. Fifty-six patients were enrolled in this prospective controlled study. In each patient, one eye was randomly assigned for treatment with the Q-factor customized PRK (custom-Q study group) and the other eye treated with wavefront-guided customized PRK. Preoperative and 3-month postoperative manifest refraction, contrast sensitivity, visual acuity, aberrometry, and asphericity of the cornea were compared between the two groups. All eyes were treated with the Wavelight Eye-Q 400 Hz excimer laser in a single refractive surgery center by a single surgeon. Uncorrected visual acuity (UCVA) improved to 20/20 or more and 20/25 or more in 34 eyes (60.7%) and 56 eyes (100%), respectively, in the wavefront-guided ablation group and in 36 eyes (64.2%) and 54 eyes (96.4%) in the custom-Q ablation group. All eyes had UCVA of 20/40 or better. A total of 54 eyes (96.4%) in the wavefront-guided ablation group and 56 (100%) in the custom-Q ablation group had spherical equivalent (SE) within -/+0.5 D. One eye in each group (2%) lost >or=2 lines of best-corrected visual acuity (BCVA). High order root mean square (RMS) in the wavefront-guided group was 0.3630-/+0.13 mum preoperatively and 0.427-/+0.17 at 3 months (p=0.2). In the custom-Q ablation group it was 0.329-/+0.092 preoperatively and 0.4730-/+0.181 at 3 months after PRK (p=0.08). Regarding safety and refractive efficacy, custom-Q ablation profiles were clinically equivalent to wavefront-guided profiles in corrections of myopia up to -6.00 D and astigmatism up to 2.50 D.

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.

Treatment of Keratoconus by Topography-guided Customized Photorefractive Keratectomy: Two-year Follow-up Study

To evaluate the outcome of treatment of mild to moderate keratoconus with photorefractive keratectomy (PRK) and computed videokeratography for customized ablation of the superficial corneal layers. Eighteen nonconsecutive patients with bilateral keratoconus (Krumeich classification, grade 2) were examined. Both eyes were treated in 7 patients and 1 eye in 11 patients. Eight contralateral eyes served as controls. Photorefractive keratectomy was performed with the Zeiss MEL 70 excimer laser using the topographically supported customized ablation program. We evaluated changes in keratoconus topography data at 6 (25 eyes), 12 (25 eyes), and 24 (22 eyes) months after treatment (mean follow-up: 22.56 +/- 3.97 months) and versus control eyes. Changes in visual acuity and manifest refraction (spherical equivalent and cylindrical component) were also evaluated during follow-up. The mean keratoconus index, keratoconus severity index, keratoconus apex, keratoconus predictor index, opposite sector index, and differential sector index were significantly lower (all P < .0001) 24 months after treatment versus baseline data. Keratoconus topography parameters were significantly worse in control eyes 24 months after study onset versus baseline. Mean uncorrected visual acuity (P < .0001) and best spectacle-corrected visual acuity (P < .05) were significantly increased 24 months after surgery. Customized photorefractive surgery improved videokeratography indices and clinical data in patients affected by grade 2 keratoconus.

Effects of nonsteroidal ophthalmic drops on epithelial healing and pain in patients undergoing bilateral photorefractive keratectomy (PRK)

The present study, which was designed as a prospective, double-masked, randomized, controlled, single-site study, was conducted to compare the effects of 3 approved ophthalmic nonsteroidal anti-inflammatory drugs-nepafenac ophthalmic suspension 0.1% (Nevanac; Alcon Laboratories, Inc., Fort Worth, Tex), ketorolac tromethamine ophthalmic solution 0.4% (Acular LS; Allergan, Irvine, Calif), and bromfenac 0.09% (Xibromtrade mark; ISTA Pharmaceuticals, Irvine, Calif)-on corneal reepithelialization and postoperative pain control in patients undergoing photorefractive keratectomy. In addition to nonsteroidal anti-inflammatory drugs, each patient received an antibiotic-moxifloxacin hydrochloride ophthalmic solution 0.5% (nepafenac group) or gatifloxacin ophthalmic solution 0.3% (ketorolac and bromfenac groups). All treatments were administered 3 times daily beginning 1 d preoperatively and continuing for 1 wk postoperatively; prednisolone acetate 1.0% was administered concurrently 4 times daily. Bandage contact lenses were replaced at each postoperative visit for corneal staining and epithelial defect grading. Self-evaluation of pain relief was recorded on postoperative days 1 and 3 with the use of a visual analog scale. A total of 29 patients (58 eyes) were enrolled and underwent bilateral custom photorefractive keratectomy. Mean time to reepithelialization was 5.50+/-1.59 d for the nepafenac 0.1% group, 5.62+/-1.23 d for the ketorolac 0.4% group, and 7.25+/-2.53 d for the bromfenac 0.09% group. A significant difference was detected between nepafenac 0.1% and bromfenac 0.09% and between ketorolac 0.4% and bromfenac 0.09% (P<.05). Significant reductions in pain scores were observed with nepafenac 0.1% on day 1 (-1.13) and day 3 (-1.32), ketorolac 0.4% on day 3 (-0.88), and bromfenac 0.09% on day 3 (-0.83). No adverse events were reported. Eyes treated with nepafenac 0.1% or ketorolac 0.4% achieved complete reepithelialization significantly faster than those treated with bromfenac 0.09%. Daily contact lens removal and application of fluorescein may have delayed reepithelialization in the overall population; however, the effect would have been the same in all 3 groups. Pain relief with nepafenac 0.1% was achieved sooner than with ketorolac 0.4% or bromfenac 0.09%.

Topographic Customized Photorefractive Keratectomy for Regular and Irregular Astigmatism After Penetrating Keratoplasty Using the LIGI CIPTA/LaserSight Platform

To evaluate the use of a software ablation program (Corneal Interactive Programmed Topographic Ablation [CIPTA]) that provides customized photorefractive keratectomy (PRK) to correct astigmatism after keratoplasty. In this prospective, noncomparative, consecutive case series, 44 eyes underwent CIPTA for correction of astigmatism after penetrating keratoplasty. Eighteen eyes were treated for regular astigmatism and 26 eyes were treated for irregular astigmatism after penetrating keratoplasty. Orbscan II topography (Bausch & Lomb) and a flying-spot laser (LaserScan 2000; LaserSight) were used. Epithelial debridement with alcohol was performed before PRK in 16 eyes and transepithelial PRK was performed in 28 eyes. Mean target-induced astigmatism was 8.19 +/- 2.68 diopters (D) and 7.68 +/- 4.50 D in the regular and irregular astigmatism groups, respectively. Mean follow-up was 25.4 +/- 13 months. At last postoperative follow-up, 13 (72.2%) and 18 (69.2%) eyes in the regular and irregular astigmatism groups, respectively, had uncorrected visual acuity (UCVA) better than 20/40. Four (22.2%) and 8 (30.7%) eyes in the regular and irregular astigmatism groups, respectively, had UCVA of 20/20. Fourteen (77.7%) and 18 (69.2%) eyes in the regular and irregular astigmatism groups, respectively, were within 1.00 D of attempted correction in spherical equivalent manifest refraction. No eye lost Snellen lines of best spectacle-corrected visual acuity. Mean surgically induced astigmatism was 7.66 +/- 2.70 D and 6.99 +/- 3.80 D for the regular and irregular astigmatism groups, respectively. Index of success of astigmatic correction was 0.138 and 0.137 for the regular and irregular astigmatism groups, respectively. Haze developed in three eyes. Topography-driven PRK using CIPTA software is a suitable solution for correcting regular and irregular astigmatism after penetrating keratoplasty.

Wavefront-guided Treatment of Symptomatic Eyes Using the LADAR6000 Excimer Laser

To evaluate the clinical results of wavefront-guided customized treatment of eyes that underwent previous keratorefractive surgery with clinically significant visual symptoms related to the presence of higher order aberrations, with or without defocus/astigmatism. Twenty-eight consecutive eyes of 19 symptomatic patients underwent wavefront-guided custom photorefractive keratectomy (PRK with mitomycin C) to correct low and high order aberrations, using the LADAR-Vision platform. All eyes had manifest refractive spherical equivalent (MRSE) error from 0.00 to -4.25 diopters (D), and high order aberrations root-mean-square (RMS) values >0.80 microm for a 6.0-mm measurement diameter (mean: 1.18 microm). Eyes were examined at 1, 3, and 6 months postoperatively. Uncorrected (UCVA) and best spectacle-corrected visual acuity (BSCVA), MRSE, wavefront measurement of high order aberrations, and patient subjective evaluation were the parameters used to assess the treatment. Six months after treatment, all 28 eyes had an improvement in UCVA compared to preoperative values. Seventeen (60.7%) eyes gained lines of BSCVA (1 to 3 lines) whereas 1 eye lost 1 line. Although the amount of positive defocus was intentionally and empirically undercorrected in this study, MRSE was slightly hyperopic (mean +0.65 D, range: -0.25 to +1.75 D). All eyes showed a reduction in pre-existing high order aberrations, with a mean reduction of 47% (0.62 microm). Spherical aberration reduced the most (mean 60%), coma was reduced by a mean 29%, and all other terms were reduced by a mean 42% compared to preoperative values. Subjectively, all patients but 1 (both eyes treated) noticed a reduction in their pre-existing visual symptoms. Overall, the treatment was considered satisfactory by the patients in terms of visual quality gain. This series of consecutive treatments of symptomatic eyes indicates wavefront-guided custom ablation is an effective surgical option to reduce visually impairing high order aberrations and related visual symptoms. To avoid the resulting hyperopic shift, some significant nomogram adjustments are necessary, most often when pre-existing positive spherical aberration is present.

Two-step procedure to enlarge small optical zones after photorefractive keratectomy for high myopia

We describe a method for the visual rehabilitation of patients with small optical zones and related complaints after photorefractive keratectomy (PRK) and laser in situ keratomileusis for high myopia. In many of these cases from the early 1990s, low central corneal thickness in combination with residual myopia did not allow for enlargement of the small optical zone by a topography-guided treatment in the first instance. We therefore perform, as a first step, a clear lens exchange aiming at hyperopia. This enables us to perform, as a second step, a topography-guided customized PRK with marked enlargement of the optical zone. Such 2-step procedures may be of great benefit to patients with small optical zones and low central corneal thickness.

Custom photorefractive keratectomy ablations for the correction of spherical and cylindrical refractive error and higher-order aberration.

Photorefractive keratectomy is an evolving refractive procedure for correcting myopia, hyperopia, and astigmatism. Earlier descriptions of the patterns required for this surgery are based on paraxial optics. In this investigation the required pattern is generalized to account for spherical refractive error (defocus), axial astigmatism of arbitrary orientation, and fourth-order aberrations of the eye. The patterns described in this study can be used to customize photorefractive keratectomy and to provide corrections that account for aberration content as well as paraxial values. Furthermore, a description of the pattern along the boundary of the optical zone is given, which may prove useful in designing blending zones. An example of the use of these techniques is given for a schematic eye model.