Post-photorefractive Keratectomy Research Articles

Evaluation of Corneal High Order Aberrations in Post Laser-Assisted in Situ Keratomileusis versus Photorefractive Keratectomy in Myope

Background Aberrations of the eye are the difference between two surfaces: the ideal and the actual wave front. Higher order aberrations are a relatively small component, comprising about 10% of the eye’s total aberrations. High order aberrations increase with age and minor symmetry exists between the right and the left eyes. Aim and objectives To Compare corneal high order aberrations in post laser-assisted in situ keratomileusis with corneal high order aberrations in post Photorefractive keratectomy in myope. Subjects and methods this study was designed as a prospective randomized intervention study that conducted on 40 myopic eyes. The eyes divided into two randomized groups. Group A: 20 myopic eyes corrected with laser-assisted in situ keratomileusis and Group B: 20 myopic eyes corrected with Photorefractive keratectomy. Cases were collected for LASIK and PRK at operative theater in Beni-Suef University Hospital and clear vision laser center in Cairo, from May 2019 till January 2022. Result There was clinically significant difference between pre- and post-operative visual acuity, vertical trefoil and vertical coma of LASIK group and there was clinically significant between pre- and post-operative visual acuity, vertical trefoil and vertical coma of PRK group. But there was no significant difference between LASIK and PRK in visual acuity, spherical aberration, higher order 5 mm and 6 mm, vertical coma and Vertical trefoil. Conclusion There is non-significant increase in higher order aberration and spherical aberration post LASIK and post PRK with lesser amount in PRK.

Changes in Corneal Biomechanical Properties after Laser-Assisted in situ Keratomileusis and Photorefractive Keratectomy in Myopia.

To compare changes in corneal biomechanical properties after laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) in low and moderate myopia by Ocular Response Analyzer. Quasi-experimental study. Place and Duration of the Study: Armed Forces Institute of Ophthalmology (AFIO), Rawalpindi, Pakistan, between September 2020 and April 2022. Myopic correction was done in forty-six eyes of twenty-three patients by PRK, and forty-seven eyes of twenty-four patients by LASIK. Corneal hysteresis (CH) and corneal resistance factor (CRF) were measured using Ocular Response Analyzer (ORA), pre-operatively, and then 1, 3, and 6 months, postoperatively. The relationship between the amount of myopia treated and biomechanical properties was also studied. CRF and CH were decreased significantly after LASIK and PRK. A significantly larger decrease in CRF was observed after LASIK as compared to PRK at 6 months (Mann-Whitney U test: CRF, p = 0.02); however, decrease in CH was not statistically significant between LASIK and PRK at 6 months period (Mann-Whitney U test: CH, p = 0.388). A significant correlation was observed between the changes in biomechanical properties and extent of myopic correction after LASIK and PRK. Biomechanical strength of the cornea was significantly reduced by PRK and LASIK, which was also dependent on the spherical equivalent (SEQ) of myopic correction. A significantly larger change in CRF was observed after LASIK as compared to post PRK. Myopia, Laser in situ keratomileusis, Photorefractive keratectomy, Cornea, Biomechanics.

Management of Corneal Haze After Photorefractive Keratectomy.

Photorefractive keratectomy (PRK) is a safe and popular corneal surgery performed worldwide. Nevertheless, there is potential risk of corneal haze development after surgery. Proper management of post PRK haze is important for good visual outcome. We performed a comprehensive review of the literature on the various risk factors and treatments for PRK haze, searching the PubMed, Google Scholar, SCOPUS, ScienceDirect, and Embase databases using relevant search terms. All articles in English from August 1989 through April 2023 were reviewed for this study, among which 102 articles were chosen to be included in the study. Depending on the characteristics of and examination findings on post PRK haze, different management options may be preferred. In the proposed framework, management of PRK haze should include a full workup that includes patient's subjective complaints and loss of vision as well as visual acuity, biomicroscopy, anterior segment optical coherence tomography, epithelial mapping, and Scheimpflug densitometry. Topical steroid treatment for haze should be stratified based on early- or late-onset haze. Mechanical debridement or superficial phototherapeutic keratectomy (PTK) may be used to treat superficial corneal haze. Deep PTK and/or PRK can be used to treat deep corneal haze. Mitomycin-C and topical steroids are prophylactic post-surgery agents to prevent recurrence of haze.

Management of corneal haze and edema post-PRK

Introduction: To present the potential use of serum tears, corneal crosslinking, and phototherapeutic keratectomy in the management of corneal haze and edema post-photorefractive keratectomy (PRK). Patient and Clinical Findings: A patient who underwent PRK and subsequently developed corneal haze and edema was treated using conservative management to achieve moderate improvement. Diagnosis, Intervention, and Outcomes: The combination of serum tears, corneal crosslinking, and phototherapeutic keratectomy was used to treat corneal haze and edema, helping the patient achieve an uncorrected visual acuity of 20/20 in the last follow-up. Conclusions: The use of serum tears, corneal crosslinking, and phototherapeutic keratectomy may provide an additional therapeutic option in the treatment of corneal haze and edema that develops post-PRK.

Post photorefractive keratectomy (PRK) infectious keratitis; six-year experience of a tertiary eye hospital.

As an essential development in the new century, surface ablation procedures have attracted increasing attention. There exists a concern regarding the risk of infectious keratitis. Hence, we aimed to investigate the rate and predisposing factors of infectious keratitis after photorefractive keratectomy (PRK). This retrospective study was designed in two phases. First, the rate of post-PRK keratitis of Farabi Eye Hospital was investigated. In other words, the targeted population was the patients who developed keratitis after performing procedure at Farabi Eye Hospital. In the second phase, all the patients with the diagnosis of post-PRK keratitis were studied regardless of the centre where surgery was performed. Patients with the diagnosis of infectious keratitis between 2014 and 2020 were enrolled and following information was analyzed: demographics, presentation time after surgery, perioperative medications, culture results, risk factors, medical treatment, complications, and final visual acuity. The total number of PRK procedures in our centre was 24,986 (13,253 patients), in which 6 eyes of 5 patients developed keratitis. Beside these 5 patients, 24 referred patients (24 eyes) from the other centres were enrolled. Finally, a total number of 29 patients (30 eyes) were included. Our analysis revealed that manipulation of contact lens, dry eye, and blepharitis were the essential predisposing factors for keratitis development. The overall post-PRK keratitis occurrence rate of our study was 0.02%. Our observation highlighted the importance of preoperative examination and treatment of the lids and dry eye disease.

Dexamethasone-Eluting Contact Lens for the Prevention of Postphotorefractive Keratectomy Scar in a New Zealand White Rabbit Model.

To evaluate the safety and efficacy of an experimental dexamethasone-eluting contact lens (DCL) for the prevention of postphotorefractive keratectomy (PRK) corneal haze in a New Zealand White (NZW) rabbit model. Both eyes of 29 NZW rabbits underwent PRK. The rabbits were randomized to one of the 5 study arms for 4 weeks: tarsorrhaphy only, tarsorrhaphy and bandage contact lens (BCL) replaced weekly, tarsorrhaphy and BCL for 1 week plus topical 0.1% dexamethasone ophthalmic solution (drops) for 4 weeks, tarsorrhaphy and BCL replaced weekly plus topical dexamethasone for 4 weeks, and tarsorrhaphy and DCL changed weekly for 4 weeks. Each week for 4 consecutive weeks postoperatively, the tarsorrhaphies were opened, the eyes underwent evaluation and imaging, and the tarsorrhaphies were replaced. Contact lenses were cultured on removal. Central corneal haze was assessed weekly with corneal densitometry. After 4 weeks, the animals were killed, and the eyes were enucleated for histopathologic analysis. The tarsorrhaphy only group displayed more haze with a greater change in optical densitometry from pre-op compared with the other treatment groups. There was no difference between the DCL group and the groups receiving a BCL and dexamethasone drops in densitometry or histopathology. No NZW rabbits developed clinical signs of infection, and cultures from DCLs and BCLs grew similar organisms. In the post-PRK rabbit model, DCLs worn weekly for 4 weeks were safe and as effective at preventing corneal haze as 0.1% dexamethasone drops applied 4 times a day for 4 weeks.

Transepithelial Laser versus Alcohol Assisted Photorefractive Keratectomy Safety and Efficacy: 1-Year Follow-up of a Contralateral Eye Study.

PurposeTo 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.MethodsA 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.ResultsEpithelial 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.ConclusionsAlcohol assisted and transepithelial photorefractive keratectomy have comparable results regarding safety and efficacy.

Melhora da qualidade do sono e das atividades diárias pós PRK imediato utilizando codeína com paracetamol: análise secundária de um ensaio clínico randomizado, duplo-cego e placebo-controlado

To determine whether codeine plus acetaminophen after photorefractive keratectomy (PRK) have beneficial effects on sleep quality, activity levels, and food intake, beyond their effect of pain relief. We enrolled 40 patients (80 eyes) in this randomized, double-blind, paired-eye, placebo-controlled, add-on trial. Each eye was treated 2 weeks apart, and the patients were randomly allocated to receive either the placebo or the intervention (30 mg codeine and 500 mg acetaminophen) (4 times a day for 4 days). Outcomes were sleep quality, daily activity level, and food intake within 24-72 h post-photorefractive keratectomy, as measured by the McGill Pain Questionnaire. Sleep quality and daily activity level were inversely associated with pain scores within the first 48 h post-photorefractive keratectomy. During the intervention, patients were significantly more likely to score their sleep quality as good at 24 h (relative risk=2.5; 95% confidence interval 1.48-4.21, p<0.001) and 48 h compared to during placebo (relative risk=1.37; 95% confidence interval: 1.03-1.84, p=0.023). The probability of reporting good daily activity level at 24 and 72 hours post-photorefractive keratectomy was three times higher when patients received the intervention compared to the placebo (relative risk=3.0; 95% confidence interval: 1.49-6.15, p=0.006 and relative risk=1.31; 95% confidence interval: 1.02-1.67, p=0.021, respectively). No difference was observed in food intake. The oral combination of codeine and acetaminophen significantly improves sleep quality and daily activity level within the first 24-72 h post-photorefractive keratectomy compared to a placebo.

Repeatability and agreement of total corneal and sublayer pachymetry with 2 different algorithms of Fourier-domain optical coherence tomography in myopic and postphotorefractive keratectomy eyes.

To investigate repeatability and agreement of total corneal and sublayer pachymetry with 2 different algorithms of Fourier-domain optical coherence tomography (OCT) in myopic and postphotorefractive keratectomy (PRK) eyes. Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran. Prospective observational study. Total corneal, epithelial, and stromal thicknesses were measured using RTVue-XR OCT with Pachymetry + Cpwr (6.0 mm algorithm) and PachymetryWide (9.0 mm algorithm) scan patterns. The repeatability of 25 zones of 9.0 mm map and 17 zones of 6.0 mm map and the agreement between measurements of these 2 algorithms were calculated. Ninety-five myopic and 117 post-PRK patients were evaluated. By the 9.0 mm algorithm, coefficient of variation (CoV) for total cornea was 2.33% or lesser and 2.49% or lesser and for epithelium was 5.14% or lesser and 5.18% or lesser; and by the 6.0 mm algorithm, CoV for total cornea was 1.80% or lesser and 2.59% or lesser and for epithelial thickness was 3.08% or lesser and 4.80% or lesser in myopic and post-PRK eyes, respectively. Bland-Altman mean difference for epithelial thickness was 0.69 or lesser and 1.16 or lesser and 95% limits of agreement for epithelial thickness was 6.81 or lesser and 8.56 or lesser in myopic and post-PRK eyes, respectively. Good repeatability was seen in measurements of total corneal, stromal, and epithelial thicknesses by both algorithms. Agreement of the 2 algorithms in central zone was also good. However, large range of variation in paracentral thickness measurements did not allow us to consider these algorithms as interchangeable.

A Review on Different Tonometers for Intraocular Pressure Measurement After Photorefractive Keratectomy or Small Incision Lenticule Extraction.

This paper aims to review different tonometers for intraocular pressure measurement in eyes after photorefractive keratectomy or small incision lenticule extraction. An Entrez Pubmed search was performed on July 19th, 2020. There were 32 eligible articles investigated in the use of tonometers or biomechanical properties of cornea in post photorefractive keratectomy eyes and 11 articles investigated in post small incision lenticule extraction eyes. Corvis ST and dynamic contour tonometry were found to be accurate for intraocular pressure measurement in post photorefractive keratectomy eyes. For post small incision lenticule extraction eyes, Corvis ST was found to be more accurate than other tonometers. Other tonometers such as Goldmann applanation tonometer, noncontact tonometry, Tonopen, ocular response analyzer can also be used in post photorefractive keratectomy or small incision lenticule extraction eyes in clinical practice; however, it is important for ophthalmologists to take note of the chances of discrepancies.

Photorefractive keratectomy (PRK) Prediction, Examination, tReatment, Follow-up, Evaluation, Chronic Treatment (PERFECT) protocol - A new algorithmic approach for managing post PRK haze.

Purpose:The aim of this study was to discuss the possible risk factors predisposing to post photorefractive keratectomy (PRK) haze formation and develop and validate a risk scoring system, so that this could be applied to our clinical practice as an algorithmic approach.Methods:Study was divided into 2 arms, in the retrospective arm we looked at 238 eyes of patients undergoing PRK where certain presumed risk factors from literature and clinical experience were identified and statistical significance of association was studied in the development of corneal haze. The risk scoring system was applied to the 450 eyes in the prospective arm for validation. This was then used to formulate an algorithmic approach to manage post-PRK haze.Results:22 out of 238 eyes in the retrospective arm developed haze where risk factors such as contact lens intolerance, altered tear film break up time, meibomian gland drop out and vitamin d levels were significantly associated with post-PRK haze (p < 0.05) and these factors were identified in the prospective arm. Treatment of these modifiable factors led to a significant reduction in post-PRK haze.Conclusion:Thus identifying and treating risk factors of haze in patients undergoing PRK could improve surgical outcomes and patient satisfaction.

Efficacy of corneal cooling on postoperative pain management after photorefractive keratectomy: A contralateral eye randomized clinical trial

PurposeTo compare chilled and room temperature balanced salt solution (BSS) and bandage contact lens (BCL) on post photorefractive keratectomy (PRK) pain. MethodsIn a prospective, single-masked, controlled eye study, one hundred eyes of fifty patients were divided into two groups which received room temperature or chilled BSS and BCL in each eye, and compared for post-PRK pain. Three different pain evaluation systems were used to evaluate pain between the groups at 1 and 6 h and days 1, 2, 3, 5, and 7, postoperatively. Results15 patients were male (30%), and 35 were female (70%). The mean age was 29 ± 5 (20–40) y/o. The mean spherical equivalent (SE) of preoperative refractive error in both groups was not statistically significantly different (−4.18 ± 1.5 in chilled and −4.19 ± 1.7 in room-temperature groups, respectively; P = 0.94). The mean time of epithelial healing was 6.16 ± 1.7 (3–13) days in the chilled and 6.10 ± 1.59 (3–12) in the room temperature group (P = 0.32). Best corrected visual acuity (BCVA) at 1 month was 0.013 ± 0.03 (0–0.22) logarithm of the minimum angle of resolution (logMAR) in the chilled group and 0.014 ± 0.04 (0–0.22) logMAR in the room temperature group, postoperatively (P = 0.84). No statistically significant difference was found between the two groups by any of the three pain scoring systems. No clinically important corneal haziness was found in the groups during follow-up. ConclusionChilled BSS and BCL do not seem to be superior to room temperature in reducing post-PRK pain.

Targeted AAV5-Smad7 gene therapy inhibits corneal scarring in vivo.

Corneal scarring is due to aberrant activity of the transforming growth factor β (TGFβ) signaling pathway following traumatic, mechanical, infectious, or surgical injury. Altered TGFβ signaling cascade leads to downstream Smad (Suppressor of mothers against decapentaplegic) protein-mediated signaling events that regulate expression of extracellular matrix and myogenic proteins. These events lead to transdifferentiation of keratocytes into myofibroblasts through fibroblasts and often results in permanent corneal scarring. Hence, therapeutic targets that reduce transdifferentiation of fibroblasts into myofibroblasts may provide a clinically relevant approach to treat corneal fibrosis and improve long-term visual outcomes. Smad7 protein regulates the functional effects of TGFβ signaling during corneal wound healing. We tested that targeted delivery of Smad7 using recombinant adeno-associated virus serotype 5 (AAV5-Smad7) delivered to the corneal stroma can inhibit corneal haze post photorefractive keratectomy (PRK) in vivo in a rabbit corneal injury model. We demonstrate that a single topical application of AAV5-Smad7 in rabbit cornea post-PRK led to a significant decrease in corneal haze and corneal fibrosis. Further, histopathology revealed lack of immune cell infiltration following AAV5-Smad7 gene transfer into the corneal stroma. Our data demonstrates that AAV5-Smad7 gene therapy is relatively safe with significant potential for the treatment of corneal disease currently resulting in fibrosis and impaired vision.

Validity of Tono-pachymetry for Measuring Corrected Intraocular Pressure in Non-surgical and Post-photorefractive Keratectomy Eyes.

PurposeTo assess the validity of central corneal thickness (CCT) and corrected intraocular pressure (IOP) values obtained by tono-pachymetry in non-surgical and post-photorefractive keratectomy (PRK) eyes.MethodsFor the study, 108 young healthy participants and 108 patients who had PRK were enrolled. Measurements were randomly performed by tono-pachymetry, ultrasonic (US) pachymetry, and Goldmann applanation tonometry (GAT). CCT measurement by tono-pachymetry was compared to that of US pachymetry. The corrected IOP value obtained by tono-pachymetry was compared to that obtained by US pachymetry and GAT. The corrected IOP from US pachymetry and GAT was calculated using the identical compensation formula built into the tono-pachymetry. Bland-Altman plot and paired t-test were conducted to evaluate the between-method agreements.ResultsThe mean CCT measurement using tono-pachymetry was significantly greater by 7.3 µm in non-surgical eyes (p < 0.001) and 17.8 µm in post-PRK eyes (p < 0.001) compared with US pachymetry. Differences were significant in both Bland-Altman plotand paired t-test. The mean difference of corrected IOP values obtained by tono-pachymetry and calculated from measurements by US pachymetry and GAT was 0.33 ± 0.87 mmHg in non-surgical eyes and 0.57 ± 1.08 mmHg in post-PRK eyes. The differences in the Bland-Altman plot were not significant.ConclusionsThe CCT measurement determined using tono-pachymetrywas significantly thicker than that of US pachymetry. The difference in CCT was greater in post-PRK eyes than in non-surgical eyes. However, the corrected IOP value obtained by tono-pachymetry showed reasonable agreement with that calculated from US pachymetry and GAT measurements.

Post-photorefractive Keratectomy Pain and Corneal Sub-basal Nerve Density.

Purpose:The perceived and reported pain of patients receiving photorefractive keratectomy (PRK) widely varies. We assessed the potential role of the subbasal nerve plexus density as a predictor of postoperative pain level. Consecutive patients scheduled to undergo PRK at the Refractive Surgery Clinic of Farabi Eye Hospital, Tehran, were approached.Methods:Forty-nine myopic left eyes from 49 patients who consented to undergo scanning slit confocal microscopy assessments preoperatively were included. ImageJ (1.48v) was used to measure the captured subbasal nerve length. Postoperative pain intensity was assessed by the Visual Analog Scale (VAS) (score range: 0 for no pain to 10 for the maximum possible) on the next day of surgery.Results:The mean age of the patients was 27.55 (range: 19–40) years. The median reported pain level was 5. Approximately 32.7% of the subjects reported a pain score of 6 or higher. Mean nerve density was 19.54 (range: 14.34–24.73) mm/mm2. Nerve density was not correlated with the reported intensity of pain (P = 0.172). However, pain was correlated with the reported ocular discomfort, i.e., a pooled index of foreign body sensation, photophobia, burning sensation, and tearing (P < 0.001), and also with the pooled index of ocular inflammatory signs (conjunctival injection and eyelid edema) (P = 0.027).Conclusion:Crude density of corneal nerves may not be a good predictor of post-PRK pain while wearing bandage contact lenses. The predominant pain mechanism appears to be of an inflammatory nature (not nociceptive or neuropathic).

Current trends in pain management after photorefractive and phototherapeutic keratectomy

Since the introduction of photoablative procedures, postoperative pain management has been a major challenge for both the patient and the surgeon. Over the years, significant advances have been made in our ability to overcome this challenge. The purpose of this article is to discuss the most current strategies for pain control after photorefractive keratectomy and phototherapeutic keratectomy. Methods for pain control can be targeted locally or systemically and can be pharmacological or nonpharmalogical. Options include anesthetics, NSAIDs, opiates, and anticonvulsants, as well as bandage contact lenses and corneal cooling. Literature and experience provide insight on the efficacy and safety of the many options for post-photorefractive keratectomy pain control. Generally, refractive surgeons are using a combination approach to achieve pain control with excellent results.

Surgical technique for graft exchange after big-bubble deep anterior lamellar keratoplasty.

The aim of this study was to describe a surgical technique for repeat deep anterior lamellar keratoplasty (DALK) by baring Descemet membrane again in eyes affected by stromal opacity of the donor lamella. Repeat DALK was performed in 5 eyes of 5 patients affected by central stromal opacity not involving the endothelium; indications for repeat surgery were postbacterial or postherpetic corneal scars (n = 3), postphotorefractive keratectomy haze (n = 1), and recurrence of granular dystrophy (n = 1). The surgical procedure consisted of the following: (1) superficial trephination, 250 μm in depth, on the original peripheral scar; (2) blunt detachment of the donor graft completed by means of corneal forceps; (3) apposition of the new lamella. Best spectacle-corrected visual acuity, topographic astigmatism, and endothelial cell density were evaluated preoperatively, as well as 3, 6, 9, 12, and 18 months after surgery. At the latest follow-up examination, with all sutures removed from all eyes, the best spectacle-corrected visual acuity was 20/30 or better in all cases with 3 eyes achieving 20/20. Postoperative refractive astigmatism averaged 3.0 ± 1.2 diopters (mean ± SD); endothelial cell density was not significantly affected by surgery. Repeat DALK is effective in removing diseased corneal stroma while keeping the recipient endothelium unaffected; the procedure is simple and does not require pneumatic dissection, thus eliminating the most challenging surgical step; postoperative visual recovery does not differ from that experienced after primary DALK.

Reliability of corneal dynamic scheimpflug analyser measurements in virgin and post-PRK eyes.

PurposeTo determine the measurement reliability of CorVis ST, a dynamic Scheimpflug analyser, in virgin and post-photorefractive keratectomy (PRK) eyes and compare the results between these two groups.MethodsForty virgin eyes and 42 post-PRK eyes underwent CorVis ST measurements performed by two technicians. Repeatability was evaluated by comparing three consecutive measurements by technician A. Reproducibility was determined by comparing the first measurement by technician A with one performed by technician B. Intraobserver and interobserver intraclass correlation coefficients (ICCs) were calculated. Univariate analysis of covariance (ANCOVA) was used to compare measured parameters between virgin and post-PRK eyes.ResultsThe intraocular pressure (IOP), central corneal thickness (CCT) and 1st applanation time demonstrated good intraobserver repeatability and interobserver reproducibility (ICC≧0.90) in virgin and post-PRK eyes. The deformation amplitude showed a good or close to good repeatability and reproducibility in both groups (ICC≧0.88). The CCT correlated positively with 1st applanation time (r = 0.437 and 0.483, respectively, p<0.05) and negatively with deformation amplitude (r = −0.384 and −0.375, respectively, p<0.05) in both groups. Compared to post-PRK eyes, virgin eyes showed longer 1st applanation time (7.29±0.21 vs. 6.96±0.17 ms, p<0.05) and lower deformation amplitude (1.06±0.07 vs. 1.17±0.08 mm, p<0.05).ConclusionsCorVis ST demonstrated reliable measurements for CCT, IOP, and 1st applanation time, as well as relatively reliable measurement for deformation amplitude in both virgin and post-PRK eyes. There were differences in 1st applanation time and deformation amplitude between virgin and post-PRK eyes, which may reflect corneal biomechanical changes occurring after the surgery in the latter.

Effect of topical diclofenac on postoperative photorefractive keratectomy pain: a randomized, controlled trial

A major disadvantage of photorefractive keratectomy is postoperative pain and discomfort. This study aims to evaluate whether topical diclofenac 0.1% therapy adds any extra benefit to systemic diclofenac in controlling pain after photorefractive keratectomy. Prospective randomized, double-masked clinical trial applied in the Khatam-al-Anbia Eye Hospital, Mashhad University of Medical Sciences, Mashhad, Iran. Sixty-eight individuals (age range, 18-35 years) having bilateral photorefractive keratectomy for myopic correction with or without astigmatism. All patients received 100 mg of extended-release oral diclofenac two times (12-h interval) before photorefractive keratectomy surgery. Postoperatively, patients were randomized into the case and control groups. Case group was administered the diclofenac 0.1% drop, one drop 2 h preoperatively and four times daily postoperatively for 3 days, whereas the control group was given artificial tears instead. Pain level, photophobia and functional activity were evaluated by the patient after operation. Two days after surgery, no statistically significant difference in pain level was noted between both groups. In addition, photophobia and functional activity was not different between the case and control groups. Eyelid oedema and conjunctival injection levels were significantly higher in the control group (P < 0.001). Administration of topical diclofenac to a standardized postoperative pain regime did not alleviate post-photorefractive keratectomy pain, although it is effective in local signs like eyelid oedema and conjunctival injection. It can be concluded that oral diclofenac is sufficient in the management of post-photorefractive keratectomy pain and addition of the topical diclofenac is unnecessary.

Pregabalin and Gabapentin for Post-Photorefractive Keratectomy Pain: A Randomized Controlled Trial

To evaluate the efficacy of pregabalin and gabapentin for reducing post-photorefractive keratectomy (PRK) pain. In this randomized clinical trial, 150 subjects undergoing PRK were allocated into 3 groups. In addition to the routine regimen, pregabalin 75 mg, gabapentin 300 mg, and placebo were administered 3 times daily for 3 days, in groups 1, 2, and 3, respectively. Subjects could take acetaminophen-codeine 300/10 mg tablets every 4 hours as needed. Patients completed a pain assessment survey (visual analogue scale ranging from 0 = no pain to 10 = most severe pain) 7 times in the first 3 days following PRK and also recorded the number of consumed acetaminophen-codeine tablets. Age, sex, refractive error, ablation depth, and mitomycin-C (MMC) application were similar in the 3 study groups (all p values>0.05). Overall pain scores in the placebo group were 0.9 and 1 unit higher than the pregabalin (p=0.029) and gabapentin (p=0.023) groups, respectively. Severe pain (score >7) was more frequent in the placebo group on the morning of the first postoperative day (p=0.043). The difference in the number of consumed acetaminophen-codeine tablets was statistically borderline (p=0.061) and less in the pregabalin (7.9 ± 5.2) and gabapentin (9.0 ± 4.1) groups in comparison to the placebo group (10.3 ± 5.6). Pregabalin and gabapentin seem to be helpful in alleviating post-PRK pain when combined with other measures. Depending on availability, either compound can be used as an adjuvant for pain control in this setting.