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The Western Journal of Medicine Jul 1998Excimer laser photorefractive keratectomy and excimer laser in situ keratomileusis are relatively new treatment modalities that can be used to correct refractive errors... (Review)
Review
Excimer laser photorefractive keratectomy and excimer laser in situ keratomileusis are relatively new treatment modalities that can be used to correct refractive errors of the eye. They are most commonly used to correct myopia (nearsightedness) but can also be used to correct hyperopia (farsightedness) and astigmatism. The excimer laser alters the refractive state of the eye by removing tissue from the anterior cornea through a process known as photoablative decomposition. This process uses ultraviolet energy from the excimer laser to disrupt chemical bonds in the cornea without causing any thermal damage to surrounding tissue. The modified anterior corneal surface enables light to be focused on the retina, thereby reducing or eliminating the dependence on glasses and contact lenses. We discuss in detail all aspects of excimer laser refractive surgery--techniques, indications and contraindications, clinical outcomes, and complications.
Topics: Humans; Lasers, Excimer; Photorefractive Keratectomy; Postoperative Complications; Refractive Surgical Procedures
PubMed: 9682628
DOI: No ID Found -
Scientific Reports May 2021This study was aimed to assess the outcomes of simultaneous phototherapeutic keratectomy (PTK) and photoastigmatic keratectomy (PAK), with special attention to...
This study was aimed to assess the outcomes of simultaneous phototherapeutic keratectomy (PTK) and photoastigmatic keratectomy (PAK), with special attention to astigmatic correction. We comprised 70 eyes of 70 patients who underwent simultaneous PTK and PAK in patients having granular corneal dystrophy and band keratopathy with refractive astigmatism of 1 diopter (D) or more. Preoperatively and 6 months postoperatively, we assessed corrected uncorrected distance visual acuity (UDVA), distance visual acuity (CDVA), manifest spherical equivalent, refractive astigmatism, corneal astigmatism, and higher-order aberrations (HOAs). LogMAR CDVA significantly improved, from 0.27 ± 0.27 preoperatively, to 0.13 ± 0.21 postoperatively (Paired t test, p < 0.001). LogMAR UDVA also significantly improved, from 0.70 ± 0.32 preoperatively, to 0.57 ± 0.41 postoperatively (p = 0.043). Refractive astigmatism significantly decreased, from 2.12 ± 0.95 D preoperatively, to 0.89 ± 0.81 D postoperatively (p < 0.001). Corneal astigmatism also significantly decreased, from 2.17 ± 0.90 D preoperatively, to 1.08 ± 0.71 D postoperatively (p < 0.001). Corneal HOAs did not significantly change, from 0.54 ± 0.30 µm preoperatively, to 0.48 ± 0.20 µm postoperatively (p = 0.140). No significant complications occurred in any eye. Simultaneous PTK and PAK treatment is effective not only for improving visual acuity, but also for reducing astigmatism.
Topics: Aged; Aged, 80 and over; Astigmatism; Cornea; Corneal Dystrophies, Hereditary; Corneal Topography; Female; Humans; Male; Middle Aged; Photorefractive Keratectomy; Refraction, Ocular; Retrospective Studies; Visual Acuity
PubMed: 33947941
DOI: 10.1038/s41598-021-89044-3 -
Journal of Current Ophthalmology 2022To compare clinical outcomes of wavefront-optimized (WFO) and wavefront-guided (WFG) photorefractive keratectomy (PRK) in patients with moderate-to-high astigmatism.
PURPOSE
To compare clinical outcomes of wavefront-optimized (WFO) and wavefront-guided (WFG) photorefractive keratectomy (PRK) in patients with moderate-to-high astigmatism.
METHODS
Patients with corneal cylinder above 2 diopters and myopic spherical equivalent were randomized into WFO or WFG PRK. Visual acuity (VA), refraction, contrast sensitivity, higher-order aberrations (HOAs), and astigmatic vector differences were documented and compared for 6 months after surgery.
RESULTS
The total number of 362 eyes from 181 patients was analyzed. The amount of total aberration was reduced 2.7 root mean square (RMS) and 2.9 RMS in the WFO and WFG groups, respectively ( < 0.001 in each group and between the groups). HOAs including coma, trefoil, and spherical aberrations increased in both the groups ( < 0.001) but were significantly more in the WFO group ( < 0.001). The increased spherical aberration was similar in both the groups ( = 0.12). Surgically induced astigmatism was not significantly different between the groups ( = 0.20). The magnitude of error was significantly higher in the WFO group ( < 0.001), but the absolute angle of error and the arithmetic angle of error were not significantly different between the groups ( = 0.20 and = 0.30, respectively).
CONCLUSION
WFO and WFG platforms of PRK appear comparable in terms of VA, refractive correction, and total aberration. Yet, HOAs may increase especially after WFO PRK.
PubMed: 36147260
DOI: 10.4103/joco.joco_18_21 -
The Cochrane Database of Systematic... Feb 2016Myopia (near-sightedness or short-sightedness) is a condition in which the refractive power of the eye is greater than required. The most frequent complaint of people... (Meta-Analysis)
Meta-Analysis Review
BACKGROUND
Myopia (near-sightedness or short-sightedness) is a condition in which the refractive power of the eye is greater than required. The most frequent complaint of people with myopia is blurred distance vision, which can be eliminated by conventional optical aids such as spectacles or contact lenses, or by refractive surgery procedures such as photorefractive keratectomy (PRK) and laser epithelial keratomileusis (LASEK). PRK uses laser to remove the corneal stroma. Similar to PRK, LASEK first creates an epithelial flap and then replaces it after ablating the corneal stroma. The relative benefits and harms of LASEK and PRK, as shown in different trials, warrant a systematic review.
OBJECTIVES
The objective of this review is to compare LASEK versus PRK for correction of myopia by evaluating their efficacy and safety in terms of postoperative uncorrected visual acuity, residual refractive error, and associated complications.
SEARCH METHODS
We searched CENTRAL (which contains the Cochrane Eyes and Vision group Trials Register) (2015 Issue 12), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to December 2015), EMBASE (January 1980 to December 2015), Latin American and Caribbean Health Sciences (LILACS) (January 1982 to December 2015), the ISRCTN registry (www.isrctn.com/editAdvancedSearch), ClinicalTrials.gov (www.clinicaltrials.gov) and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 15 December 2015. We used the Science Citation Index and searched the reference lists of the included trials to identify relevant trials for this review.
SELECTION CRITERIA
We included in this review randomized controlled trials (RCTs) comparing LASEK versus PRK for correction of myopia. Trial participants were 18 years of age or older and had no co-existing ocular or systemic diseases that might affect refractive status or wound healing.
DATA COLLECTION AND ANALYSIS
Two review authors independently screened all reports and assessed the risk of bias of trials included in this review. We extracted data and summarized findings using risk ratios and mean differences. We used a random-effects model when we identified at least three trials, and we used a fixed-effect model when we found fewer than three trials.
MAIN RESULTS
We included 11 RCTs with a total of 428 participants 18 years of age or older with low to moderate myopia. These trials were conducted in the Czech Republic, Brazil, Italy, Iran, China, Korea, Mexico, Turkey, USA, and UK. Investigators of 10 out of 11 trials randomly assigned one eye of each participant to be treated with LASEK and the other with PRK, but did not perform paired-eye (matched) analysis. Because of differences in outcome measures and follow-up times among the included trials, few trials contributed data for many of the outcomes we analyzed for this review. Overall, we judged RCTs to be at unclear risk of bias due to poor reporting; however, because of imprecision, inconsistency, and potential reporting bias, we graded the quality of the evidence from very low to moderate for outcomes assessed in this review.The proportion of eyes with uncorrected visual acuity of 20/20 or better at 12-month follow-up was comparable in LASEK and PRK groups (risk ratio (RR) 0.98, 95% confidence interval (95% CI) 0.92 to 1.05). Although the 95% CI suggests little to no difference in effect between groups, we judged the quality of the evidence to be low because only one trial reported this outcome (102 eyes). At 12 months post treatment, data from two trials suggest no difference or a possibly small effect in favor of PRK over LASEK for the proportion of eyes achieving ± 0.50 D of target refraction (RR 0.93, 95% CI 00.84 to 1.03; 152 eyes; low-quality evidence). At 12 months post treatment, one trial reported that one of 51 eyes in the LASEK group lost one line or more best-spectacle corrected visual acuity compared with none of 51 eyes in the PRK group (RR 3.00, 95% CI 0.13 to 71.96; very low-quality evidence).Three trials reported adverse outcomes at 12 months of follow-up or longer. At 12 months post treatment, three trials reported corneal haze score; however, data were insufficient and were inconsistent among the trials, precluding meta-analysis. One trial reported little or no difference in corneal haze scores between groups; another trial reported that corneal haze scores were lower in the LASEK group than in the PRK group; and one trial did not report analyzable data to estimate a treatment effect. At 24 months post treatment, one trial reported a lower, but clinically unimportant, difference in corneal haze score for LASEK compared with PRK (MD -0.22, 95% CI -0.30 to -0.14; 184 eyes; low-quality evidence).
AUTHORS' CONCLUSIONS
Uncertainty surrounds differences in efficacy, accuracy, safety, and adverse effects between LASEK and PRK for eyes with low to moderate myopia. Future trials comparing LASEK versus PRK should follow reporting standards and follow correct analysis. Trial investigators should expand enrollment criteria to include participants with high myopia and should evaluate visual acuity, refraction, epithelial healing time, pain scores, and adverse events.
Topics: Adult; Humans; Keratectomy, Subepithelial, Laser-Assisted; Myopia; Photorefractive Keratectomy; Randomized Controlled Trials as Topic; Time Factors; Visual Acuity
PubMed: 26899152
DOI: 10.1002/14651858.CD009799.pub2 -
Journal of Medicine and Life 2020Refractive eye surgeries are one of the most non-emergent ophthalmic surgeries due to the effect on the reduction of refractive errors, increasing visual acuity,...
Refractive eye surgeries are one of the most non-emergent ophthalmic surgeries due to the effect on the reduction of refractive errors, increasing visual acuity, enhancing the quality of vision, and indirectly increasing the quality of life of patients. The aim of this study was to determine Pentacam indices in the patients who underwent photorefractive keratectomy (PRK) during 2014-2018, as well as to show their correlation with the type of refractive error. This descriptive cross-sectional study was performed on 2215 eyes of 1125 patients undergoing PRK surgery. The patients' checklist, including demographic information, refractive index, keratometry, pachymetry, corneal surface zone indices, and progressive corneal thickness indices, was provided. All data were analyzed using the IBM SPSS software, version 25. The findings showed that there was a significant association between posterior corneal astigmatism (PCA) and anterior corneal astigmatism (ACA) (p=0.00). The mean Kmax front was recorded as 44.844 ± 1.58 D, which was significantly correlated with the type of refractive errors (p=0.00). According to the findings, there was a significant relationship between anterior chamber indices and refractive error types and their severity (p=0.00). There was also a significant correlation between the surface zone and keratoconus indices (i.e., index of surface variance - ISV, index of vertical asymmetry - IVA, index of height asymmetry - IHA, and minimum radius of curvature - Rmin) with refractive errors (p=0.00). The findings showed that some of the Pentacam indices could be related to the types of refractive errors in patients undergoing PRK surgery. Therefore, their evaluation is of great importance in this regard.
Topics: Adult; Astigmatism; Corneal Pachymetry; Cross-Sectional Studies; Female; Humans; Male; Photorefractive Keratectomy; Quality of Life; Visual Acuity
PubMed: 33456601
DOI: 10.25122/jml-2020-0057 -
Korean Journal of Ophthalmology : KJO Apr 2021To compare single-step transepithelial photorefractive keratectomy (TPRK) to conventional alcohol assisted epithelial removal then photorefractive keratectomy (AAPRK)... (Randomized Controlled Trial)
Randomized Controlled Trial
PURPOSE
To compare single-step transepithelial photorefractive keratectomy (TPRK) to conventional alcohol assisted epithelial removal then photorefractive keratectomy (AAPRK) regarding pain, epithelial healing, visual acuity, corneal haze measured subjectively and objectively, higher order aberrations changes, contrast sensitivity and vector analysis of astigmatic correction with one year follow-up.
METHODS
A prospective double-blind randomized study of 29 subjects (58 eyes) who underwent myopic aberration-free laser correction by smart pulse technology using Schwind Amaris 1050 Hz with 1-year follow-up. Right eye was randomly treated by AAPRK or TPRK. Postoperative assessment was performed on day 1 and 3, at 1st week, and 1st, 3rd, 6th, and 12th months. Patients were assessed for pain, epithelial healing, visual acuity, corneal haze, astigmatic correction, higher order aberrations and contrast sensitivity.
RESULTS
Epithelial healing was complete by the 3rd day in 62.1% of AAPRK eyes and in 89.7% of TPRK eyes. First day postoperative pain was higher in TPRK group (p = 0.0134). The decimal uncorrected visual acuity at 12 months was 1.47 ± 0.39 and 1.57 ± 0.38 in the AAPRK and TPRK groups respectively (p = 0.3719). Post-photorefractive keratectomy haze reached a final level of 0.04 ± 0.14 and 0.02 ± 0.1 in AAPRK and TPRK groups respectively (p = 0.5607). Contrast sensitivity was comparable in low and high frequency cycles per degree. Vector analysis of astigmatic correction showed correction index at one year of 0.99 and 1.05 for AAPRK and TPRK groups respectively.
CONCLUSIONS
Alcohol assisted and transepithelial photorefractive keratectomy have comparable results regarding safety and efficacy.
Topics: Double-Blind Method; Epithelium, Corneal; Follow-Up Studies; Humans; Lasers, Excimer; Photorefractive Keratectomy; Prospective Studies; Refraction, Ocular; Treatment Outcome
PubMed: 33596623
DOI: 10.3341/kjo.2020.0105 -
Therapeutic Advances in Ophthalmology 2022Corneal collagen cross-linking (CXL) is considered an effective procedure for slowing down or eliminating the progression of keratoconus. New techniques, in combination...
BACKGROUND
Corneal collagen cross-linking (CXL) is considered an effective procedure for slowing down or eliminating the progression of keratoconus. New techniques, in combination with CXL, have been proposed to stop the evolution of keratoconus and improve the visual function.
OBJECTIVE
To evaluate the effectiveness of combined photorefractive keratectomy (PRK) with mitomycin-C (MMC) application and CXL in the management of grade 1-2 keratoconus over a 2-year follow-up.
METHODS
Fifteen eyes underwent topography-guided PRK with 0.02% MMC application immediately followed by standard CXL.
RESULTS
Best corrected visual acuity improved from 0.15 ± 0.11 logMAR to 0.08 ± 0.09 logMAR at 24 months ( < 0.0001) in treated eyes. Mean steepest meridian keratometry reduced from 48.79 ± 3.22 D at baseline to 46.16 ± 3.11 D at 24 months ( < 0.0001). Mean flattest meridian keratometry reduced from 45.18 ± 2.17 D preoperatively to 44.35 ± 2.19 D at 24 months ( < 0.0001).
CONCLUSION
Simultaneous topography-guided PRK with MMC 0.02% application and standard CXL is a safe, promising and effective procedure in the treatment of mild and moderate keratoconus.
PubMed: 35340750
DOI: 10.1177/25158414221083362 -
Journal of Refractive Surgery... Dec 2018To determine how photorefractive keratectomy (PRK) and mitomycin C (MMC) affect corneal nerves and their regeneration over time after surgery.
PURPOSE
To determine how photorefractive keratectomy (PRK) and mitomycin C (MMC) affect corneal nerves and their regeneration over time after surgery.
METHODS
Twenty-eight New Zealand rabbits had corneal epithelial scraping with (n = 3) and without (n = 3) MMC 0.02% or -9.00 diopter PRK with (n = 6) and without (n = 16) MMC 0.02%. Corneas were removed after death and corneal nerve morphology was evaluated using acetylcholinesterase immunohistochemistry and beta-III tubulin staining after 1 day for all groups, after 1 month for PRK with and without MMC, and 2, 3, and 6 months after PRK without MMC. Image-Pro software (Media Cybernetics, Rockville, MD) was used to quantitate the area of nerve loss after the procedures and, consequently, regeneration of the nerves over time. Opposite eyes were used as controls.
RESULTS
Epithelial scraping with MMC treatment did not show a statistically significant difference in nerve loss compared to epithelial scraping without MMC (P = .40). PRK with MMC was significantly different from PRK without MMC at 1 day after surgery (P = .0009) but not different at 1 month after surgery (P = .90). In the PRK without MMC group, nerves regenerated at 2 months (P < .0001) but did not return to the normal preoperative level of innervation until 3 months after surgery (P = .05). However, the morphology of the regenerating nerves was abnormal-with more tortuosity and aberrant innervation compared to the preoperative controls-even at 6 months after surgery.
CONCLUSIONS
PRK negatively impacts the corneal nerves, but they are partially regenerated by 3 months after surgery in rabbits. Nerve loss after PRK extended peripherally to the excimer laser ablated zone, indicating that there was retrograde degeneration of nerves after PRK. MMC had a small additive toxic effect on the corneal nerves when combined with PRK that was only significant prior to 1 month after surgery. [J Refract Surg. 2018;34(12):790-798.].
Topics: Acetylcholinesterase; Alkylating Agents; Animals; Cornea; Debridement; Epithelium, Corneal; Female; Lasers, Excimer; Microscopy, Confocal; Mitomycin; Models, Animal; Nerve Regeneration; Photorefractive Keratectomy; Rabbits; Trigeminal Nerve; Wound Healing
PubMed: 30540361
DOI: 10.3928/1081597X-20181112-01 -
International Journal of Ophthalmology 2017To investigate quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy (TransPRK) in high myopia.
AIM
To investigate quantitative and qualitative optical outcomes of single-step transepithelial photorefractive keratectomy (TransPRK) in high myopia.
METHODS
In a prospective interventional case-series, 30 eyes with high myopia (-6.00 to -8.75 D) with (up to -3.00 D) or without astigmatism were enrolled from Bina Eye Hospital, Tehran, Iran. One-step TransPRK was performed with aberration-free aspherical optimized profile and SCHWIND AMARIS 500 laser. One-year follow-up results for refraction, visual acuities, vector analysis, ocular wave-front (OWF) and corneal wave-front (CWF) higher order aberrations (HOA), contrast sensitivity (CS), and post-operative haze were assessed.
RESULTS
After the surgery, both photopic and mesopic CSs significantly improved (both <0.001). We detected significant induction of OWF coma and trefoil (<0.001 for both) HOAs; CWF coma (=0.002), spherical (<0.001), and tetrafoil (=0.003) HOAs in 6 mm analysis diameter; and CWF trefoil (=0.04) HOA in 4 mm analysis diameter. The range of mean induction observed for various HOAs was 0.005-0.11 µm. The 86.7% of eyes reached an uncorrected distance visual acuity of 20/20 or better; 96.7% of eyes were within ±0.5 D of targeted spherical refraction. In vector analysis, mean correction index value was 1.03 and mean index of success was 0.22. By 12mo after the operation, no eye lost any number of corrected distance visual acuity lines. We detected no corneal haze greater than 1 throughout the follow-up.
CONCLUSION
Our findings show promising effects of single-step TransPRK on quality of vision in high myopic eyes. It also improves refraction and visual acuity.
PubMed: 28393038
DOI: 10.18240/ijo.2017.03.19 -
Turkish Journal of Ophthalmology Jun 2020To compare the asphericity and higher-order aberration (HOA) outcomes of single-step transepithelial photorefractive keratectomy (tPRK) and conventional alcohol-assisted... (Comparative Study)
Comparative Study
OBJECTIVES
To compare the asphericity and higher-order aberration (HOA) outcomes of single-step transepithelial photorefractive keratectomy (tPRK) and conventional alcohol-assisted PRK (aaPRK) in patients with myopia and myopic astigmatism.
MATERIALS AND METHODS
Of the 108 eyes of 54 patients enrolled in the study, tPRK was performed on 54 (50%) eyes and aaPRK was performed on 54 (50%) eyes. The following parameters were compared: corrected distance visual acuity (CDVA), spherical equivalent (SE), flat and steep keratometry, intraocular pressure, central corneal thickness, asphericity, and HOAs including horizontal and vertical coma, horizontal and vertical trefoil, spherical aberration, second-order vertical coma, and aberration coefficient.
RESULTS
The demographic and baseline characteristics were similar between the two groups (p>0.05, for all). The aberration coefficient value was significantly lower in patients treated with aaPRK compared to patients treated with tPRK at postoperative 3 months, 6 months, and 1 year (p=0.022, p=0.019, and p=0.017, respectively). Differences in the other variables were statistically insignificant (p>0.05 for all).
CONCLUSION
Both tPRK and aaPRK procedures obtain similar postoperative CDVA, SE, asphericity, and HOA outcomes, except the aberration coefficient value.
Topics: Adolescent; Adult; Corneal Topography; Corneal Wavefront Aberration; Epithelium, Corneal; Ethanol; Female; Follow-Up Studies; Humans; Lasers, Excimer; Male; Middle Aged; Photorefractive Keratectomy; Refraction, Ocular; Retrospective Studies; Visual Acuity; Young Adult
PubMed: 32630998
DOI: 10.4274/tjo.galenos.2019.14554