Keratectomy Research Articles

Surface ablation laser surgery: Bibliometric and visualized analysis from 2004 to 2023.

Surface ablation laser surgery has resurged in popularity recently because of its safety in correcting myopia and favorable postoperative corneal biomechanical properties. This study aimed to investigate the current focal points and future trends in surface ablation laser surgery over the last 2 decades. The Web of Science Core Collection was used as the primary data source to retrieve literature related to surface ablation laser surgery. All records, including full records and reference details, were exported in plain text format. VOSvivewer, CiteSpace, and Pajek were used to perform the bibliometric and visual analyses of the countries/regions, institutions, authors, journals, and keywords of relevant publications. A total of 3415 articles on surface ablation laser surgery were published in 253 journals. These articles were authored by 9681 individuals from 2751 institutions across 79 countries. The United States leads in terms of productivity and influence in this field. The Tehran University of Medical Sciences and Kymion GD were the most productive institutions and authors, whereas the University of Crete and Randleman JB were the most influential. The Journal of Cataract and Refractive Surgery was the most productive and influential in this area, and citation analysis revealed that the top 10 most-cited references focused primarily on postoperative wound healing and wavefront aberration. The keywords were grouped into the following 5 clusters: clinical effects and complications, special indications, iatrogenic corneal ectasia, haze, and pain management. High-frequency keywords in recent years included transepithelial photorefractive keratectomy, retreatment, transepithelial phototherapeutic keratectomy, and biomechanical properties. This bibliometric analysis examined the development trends, global cooperation, research hotspots, and future directions of surface ablation over the past 20 years.

Effect of Belin-Ambrósio deviation index on 2-year refractive outcomes of PRK.

To assess the effect of preoperative Belin-Ambrósio deviation (BAD-D) index on 2-year visual, refractive, and tomographic outcomes, as well as the efficacy and safety of photorefractive keratectomy (PRK) surgery. Eye clinic, Mashhad, Iran. Prospective cohort study. This study included 66 patients (66 eyes) who underwent PRK surgery, with a minimum follow-up period of 2 years. Participants were divided into 2 groups: preoperative BAD-D ≥1.60 (high BAD-D) and preoperative BAD-D <1.60 (low BAD-D). Preoperative and postoperative visual, refractive, and tomographic parameters were evaluated, and the efficacy and safety of the procedure were compared between groups. 66 patients with a mean age of 35.50 ± 8.21 years (range 22 to 55 years) were included. Postoperatively, the mean spherical equivalent (SE) of refractive error was +0.32 ± 0.65 diopters (D) in the high BAD-D group and +0.18 ± 0.66 D in the low BAD-D group ( P = .40). In addition, at 2 years of follow-up, the mean uncorrected distance visual acuity was 0.98 ± 0.07 in the high BAD-D group and 0.97 ± 0.08 in the low BAD-D group ( P = .905). Among the postoperative tomographic parameters, front elevation thickness, maximum Ambrósio relational thickness, astigmatism, and central corneal thickness were significantly different between the 2 groups (all, P < .05). At the 2-year follow-up, the mean Safety Index was 1.02 ± 0.04, and 1.01 ± 0.04 in high and low BAD-D groups, respectively ( P = .37), and the mean Efficacy Index was 0.99 ± 0.07 and 0.98 ± 0.06 in high and low BAD-D groups, respectively ( P = .40). The preoperative BAD-D index does not predict postoperative visual, refractive, and tomographic outcomes in patients with low-to-moderate myopia. However, in patients with normal preoperative BAD-D values, higher agreement was expected between the attempted and achieved SE.

The visual outcomes and corneal biomechanical properties after PRK and SMILE in low to moderate myopia.

To compare the corneal biomechanical parameters, visual outcome, and epithelial remodeling after small-incision lenticule extraction (SMILE) and photorefractive keratectomy (PRK) for low to moderate myopia. Prospective, interventional, randomized, comparative study. Eighty eyes of 40 patients undergoing bilateral SMILE or PRK for low to moderate myopia (<-5 D SE) were included. They were divided into two groups based on the planned refractive surgery. Visual acuity, corneal biomechanics using Corvis-ST, epithelial mapping via anterior segment optical coherence tomography, and higher-order aberrations were recorded both preoperatively and postoperatively at 6 months and compared. At 6 months follow-up, the corrected distance visual acuity as well as the postoperative spherical equivalent of both the groups were comparable (P = 0.13 and P = 0.32, respectively). The biomechanical parameters like deformation amplitude ratio (P < 0.01), inverse concave radius (P = 0.006), integrated ratio (P < 0.01), stress-strain index (P < 0.01), Ambrosio's relational thickness (ArTH) (P < 0.01), and corneal biomechanical index-laser vision correction (P = 0.02) were altered more in the SMILE group than in the PRK group, while the biomechanically corrected intraocular pressure (P = 0.16) was comparable. Epithelial remodeling (P = 0.59), higher-order aberrations (P = 0.53), and stromal keratocyte loss (P = 0.16) in both the groups were comparable. Both SMILE and PRK are comparably effective procedures for correction of low to moderate myopia in terms of visual outcomes; however, the corneal biomechanical stability in PRK is superior than that in SMILE.

One-Year Visual and Refractive Outcomes of SmartPulse® Technology in Transepithelial Photorefractive Keratectomy for Myopic and Astigmatic Patients.

Background/Objectives: This study aims to evaluate the efficacy, safety, and predictability of Transepithelial Photorefractive Keratectomy (TPRK) using the SmartPulse® technology excimer laser for the correction of myopia and myopic astigmatism, assessing visual and refractive outcomes over a one-year follow-up period. Methods: This retrospective cohort study analyzed data from patients who underwent TPRK at the Ophthalmology Department-"Victor Babes" University of Medicine and Pharmacy in Timisoara (Romania), between January 2019 and June 2023. The procedure was performed using the SmartPulse® Technology of the SmartSurfACE AMARIS 750S excimer laser (SCHWIND eye-tech-solutions, Kleinostheim, Germany). Preoperative assessments included visual acuity, refraction, and corneal measurements, with postoperative evaluations conducted for up to 12 months. Results: This study included 92 eyes from 46 patients (mean age 29.02 years, 63% male). At 12 months post-op, 100% achieved UDVA 20/25 or better, with an efficacy index of 1.01. Refractive accuracy was 96% within ±0.50 D of the target and astigmatism ≤ 0.50 D in 99% of eyes. The safety index was 1.01. Corneal haze occurred in 8.70% of eyes and was effectively managed with dexamethasone drops. Conclusions: TPRK with the SmartPulse® technology excimer laser demonstrated high efficacy and safety in correcting myopia and myopic astigmatism, achieving stable visual outcomes over one year. The procedure also showed excellent predictability with a low incidence of complications, supporting its use as a reliable refractive surgery option.

Assessing the Role of Artificial Intelligence in the Creation of Patient Educational Videos for Corneal Refractive Surgery.

We aim to assess the ability of artificial intelligence (AI) to generate patient educational videos for various corneal refractive surgeries. Three AI text-to-video platforms (InVideo (San Francisco, CA), ClipTalk (San Francisco, CA), and EasyVid (Los Angeles, CA)) were used to create patient educational videos for laser-assisted in situ keratomileusis (LASIK), photorefractive keratectomy (PRK), and small incision lenticule extraction (SMILE), respectively. Videos for LASIK and PRK from the American Academy of Ophthalmology (AAO) and a SMILE video from Zeiss served as controls for each surgery. A three-point grading system (from zero to three, with zero being the worst and three being the best in each category) was used to compare videos in terms of "image accuracy," "script accuracy," "image clarity," and "script alignment." In terms of image accuracy, the control videos outperformed InVideo, EasyVid, and ClipTalk for LASIK (3 versus 0.667 versus 0 versus 0; p<0.005), PRK (3 versus 1 versus 0.33 versus 0; p<0.05 for InVideo, p<0.005 all), and SMILE (3 versus 0.33 versus 0 versus 0.33; p<0.005), respectively. With a few exceptions, all three AI models performed similarly to the control videos in terms of script accuracy, image clarity, and script alignment. In their current state, AI text-to-video generators can produce surgical educational videos for patients with accurate script narration and high image clarity, although these platforms are not yet capable of producing medically accurate images to go along with these scripts. Further improvements in the medical accuracy of these images must be made to make these videos more appropriate for patient consumption.

Short-Term Visual and Refractive Outcomes of Single-Step Transepithelial Photorefractive Keratectomy with Amaris 750S and SmartSurfACE in Myopia and Astigmatism: A 6-Month Follow-Up Study.

Single-step transepithelial photorefractive keratectomy (TPRK) is a modern refractive surgery technique that offers a no-touch approach for correcting myopia and astigmatism. This study aims to evaluate the short-term visual and refractive outcomes of TPRK in patients with myopia and astigmatism over a 6-month follow-up period. This retrospective cohort study included patients who underwent single-step TPRK using the Amaris 750S laser platform with SmartSurfACE and SmartPulse® technologies, targeting a plano refraction. Procedures were performed with aspheric, non-wavefront-guided profiles, and outcomes were assessed postoperatively. 96% of eyes achieved 20/20 or better uncorrected distance visual acuity (UDVA), with 98% reaching 20/25 or better, and 100% achieving 20/32 or better. UDVA was the same or better than preoperative corrected distance visual acuity (CDVA) in 96% of eyes, and no eyes lost two or more Snellen lines. Refractive outcomes showed strong precision, with 93% of eyes within ±1.00 D of the target. Astigmatism correction was accurate, with 100% of eyes having ≤1.00 D of astigmatism, and 80% achieving a precise astigmatism angle of error between -5° and 5°. Single-step TPRK with SmartSurfACE and SmartPulse® technologies provides highly effective and predictable visual and refractive outcomes for myopia and astigmatism. The procedure consistently delivers precise corrections with minimal complications, making it a reliable option for refractive surgery.

Chinese expert consensus on the prevention and treatment of complications of laser corneal refractive surgery (2024)

Laser corneal refractive surgery has been carried out in China for three decades. The safety, efficacy, predictability, and long-term stability of the surgery have been well established. In the past 10 years, with the wide use of small incision lenticule extraction (SMILE) and trans-epithelial photorefractive keratectomy (T-PRK), the number of corneal laser surgeries in China has increased significantly. Although severe postoperative complications are rare, there is still the possibility of complications. Once complications occur and are not treated in time and effectively, the visual acuity and visual quality of patients would be affected. Paying attention to preoperative risk factors, standardization of the surgery procedure, and timely diagnosis and treatment of postoperative complications can minimize the negative effects. Therefore, the Cornea Group of Ophthalmology Branch of Chinese Medical Association has organized experts and scholars in this field to establish a consensus on the prevention and treatment of complications in laser corneal refractive surgery, providing guidance for the related clinical work.

Comparative Analysis of Corneal Wound Healing: Differential Molecular Responses in Tears Following PRK, FS-LASIK, and SMILE Procedures.

In this study, we aimed to analyze the changes in the expression profiles of selected messenger RNAs (mRNAs) and their encoded proteins in the tears of patients undergoing photorefractive keratectomy (PRK), femtosecond-assisted laser in situ keratomileusis (FS-LASIK), and small-incision lenticule extraction (SMILE) procedures. A total of 120 patients were divided into three groups based on the laser vision correction (LVC) procedure: PRK, FS-LASIK, or SMILE. Tear samples were collected preoperatively and at 1, 7, 30, and 180 days postoperatively. The expression levels of selected messenger RNAs (mRNAs) and proteins were analyzed by using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA), respectively. PRK and FS-LASIK elicited significantly stronger biological responses than SMILE. Interleukin-15 (IL-15) expression increased notably in the PRK and FS-LASIK groups, with mRNA levels reaching fold changes of 4.65 ± 0.65 and 4.99 ± 0.28, respectively, on day 1, compared with only 2.09 ± 0.23 in the SMILE group. Vascular endothelial growth factor A (VEGFA) levels were also elevated in the PRK (2.98 ± 0.23 fold change) and FS-LASIK groups (3.45 ± 1.09 fold change) on day 1, while the SMILE group showed minimal fluctuations. The protein concentration analysis based on the ELISA confirmed these trends, with IL-15 levels peaking at 54.2 ± 2.5 pg/mL in the PRK group and 52.8 ± 3.1 pg/mL in the FS-LASIK group, compared with 32.4 ± 1.9 pg/mL in the SMILE group on day 1. Similarly, VEGFA protein concentrations were the highest in the PRK (72.4 ± 4.1 pg/mL) and FS-LASIK patients (69.5 ± 3.8 pg/mL) on day 1 but remained low in the SMILE patients (45.6 ± 2.3 pg/mL). By day 180, gene expression and protein levels in all groups had stabilized, returning to near-preoperative values. PRK and FS-LASIK induced more pronounced molecular and protein-level changes during corneal wound healing than the less invasive SMILE procedure, indicating stronger biological responses. These findings suggest that tailored postoperative care based on the specific procedure could optimize healing and patient outcomes. However, further research with larger sample sizes and longer follow-ups is needed to confirm these observations and develop personalized treatment strategies.

Comparing Visual Outcomes of KLEx, PRK, and LASIK Procedures in the Military Population.

To assess the 6-month visual and refractive outcomes of keratorefractive lenticule extraction (KLEx) as compared to laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) in a military population at a Joint Warfighter Refractive Surgery Center. Joint Warfighter Refractive Surgery Center (JWRSC), Lackland Air Force Base, San Antonio, TX. Retrospective Study. Patients who underwent either KLEx, PRK, or LASIK between 2019-2022 were included. Anonymized data collected included demographics, pre- and post-operative uncorrected and corrected visual acuity, and manifest refraction. Of the 4,466 treated eyes, 737 (16.5%) underwent the KLEx, 2,801 (62.7%) underwent PRK, and 928 (20.8%) underwent LASIK treatment. In terms of efficacy, there was no statistically significant difference at post-operative month (POM)6 between the percentage of eyes reaching an uncorrected distance visual acuity (UDVA) of 20/20 or better between the three procedures. At POM1 (P < 0.001) and POM3 (P < 0.001), there were a greater number of eyes in the KLEx group that achieved the same or 1 line better of distance visual acuity than the PRK group. The efficacy index of KLEx, PRK, and LASIK at POM6 were 1.09, 1.10, and 0.97, respectively. The safety index for KLEx, PRK, and LASIK at POM6 were 0.96, 1.01, and 0.81, respectively. After the initial recovery period, KLEx demonstrates comparable outcomes in terms of efficacy, safety, and accuracy as compared to LASIK and PRK.

Postoperative Pain Comparison Between Alcohol-Assisted and Transepithelial Photorefractive Keratectomy Using Nepafenac Treatment: A Novel Study.

The study aimed to compare postoperative pain between alcohol-assisted and transepithelial photorefractive keratectomy in patients who received the novel analgesic preoperative nepafenac treatment 2days preoperatively and 3days postoperatively. Pain, stinging, tearing, light sensitivity, and stress levels were evaluated. The study included a retrospective analysis of 55 patients divided into two groups: bilateral alcohol-assisted photorefractive keratectomy (aa-PRK) and transepithelial photorefractive keratectomy (transepithelial-PRK). Nepafenac was administered for pain control for all patients, with patients receiving four drops for 2 days before the surgery and 3 days postoperatively per clinical instructions. Patients completed questionnaires on the day of the surgery and for the first 5 days postoperatively. Statistical analysis was performed using XLSTAT (version 2023.1.2). t-Test was used to analyze and compare pain and symptom levels and Fisher's exact test for categorical data. p-Values less than 0.05 were considered statistically significant. The study examined 55 patients (49% female) with a mean age of 25.11 ± 6.81years who had undergone bilateral surface refractive surgery to correct myopic errors. The mean baseline standard error (SE) was -3.16 ± 2.20 D. Among these patients, 27 patients underwent aa-PRK and 28 patients underwent transepithelial-PRK. Higher levels of pain were significant in the aa-PRK group (p = 0.003). However, there was no significant difference between the groups in the average levels of stinging, tearing, or light sensation. Additionally, stress levels decreased over time in both groups, with levels becoming almost equal after 5 days, and there was no significant difference in the average stress levels between the two groups. The study found that patients who underwent the transepithelial-PRK procedure had significantly lower pain levels compared with those who underwent aa-PRK after being treated with nepafenac per protocol. However, there was no significant difference between the two groups in terms of stinging, tearing, light sensation, and stress levels.

Photorefractive Keratectomy: Technical Evolution, Refractive Outcomes, Corneal Wound Healing Response, and Complications.

Photorefractive keratectomy (PRK) was the first excimer laser procedure developed to treat refractive errors. The safety and efficacy of PRK established it as one of the most performed corneal refractive procedures worldwide. With the introduction of laser in situ keratomileusis (LASIK), and more recently keratorefractive lenticule extraction (KLEx) procedures, many corneal surgeons favor these newer corneal procedures as the first choice due to faster visual rehabilitation and less discomfort during the early postoperative period. Importantly, however, PRK remains a viable alternative for most corneal refractive candidates and there are many situations in which PRK remains the refractive procedure of choice. This review addresses the technical evolution of PRK-mechanical epithelial debridement versus alcohol-assisted epithelial removal versus excimer laser-assisted epithelial debridement (transepithelial) PRK-and reports the PRK refractive outcomes compared to other keratorefractive laser procedures. The corneal wound response associated with each PRK technique and the indications, limitations, and complications of PRK are reviewed to aid refractive surgeons to best position PRK in their overall practice. [J Refract Surg. 2024;40(10):e754-e767.].

Evaluation of corneal biomechanical changes in moderate myopia after different techniques of corneal refractive surgeries

Background The most prevalent refractive error, which accounts for between 15 and 49% of cases worldwide, is myopia. Refractive surgery can fix refractive problems and lessen reliance on glasses or contact lenses. Aim This study aims to assess corneal biomechanical alterations following photorefractive keratectomy (PRK) and femtosecond laser small incision lenticule extraction (F-SMILE) in moderate myopic patients using CORVIS-ST (CST). Patients and methods This prospective, comparative, nonrandomized study was conducted on 40 patients’ eyes. with moderate myopia in a private center from January 2020 to December 2020, these eyes were subdivided into two groups: (a) The first group included 20 eyes that will receive PRK (b) The second group included 20 eyes that will receive F-SMILE. All participants will undergo operative (History taking, and examinations), preoperative (PRK, and F-SMILE), and postoperative (medications and Follow-up examinations) evaluations. Results Significant differences existed among the two groups in postoperative follow-up after 1 month and 6 months regarding deformation amplitude, radius, corvis biomechanical index, and intraocular pressure corrected biomechanically but There were insignificant differences among the two groups in terms of SPA in the same periods postoperatively. Conclusion Laser refractive surgery has a major impact on corneal biomechanical properties, as evidenced by significant changes in Corvis ST ocular biomechanical measures following PRK and F-SMILE procedures in myopic patients. The alterations resulting from F-SMILE are more substantial compared with PRK.

Topical nonsteroidal anti-inflammatory drugs for management of pain after PRK: systematic review and network meta-analysis.

Topical nonsteroidal anti-inflammatory drugs (NSAIDs) for management of pain in patients after photorefractive keratectomy (PRK). Pain after PRK is a major concern for both patients and surgeons. Although evidence supports the use of NSAIDs postoperatively, no consensus exists regarding the preferred regimen. The study aimed to compare the efficacy and safety of different topical NSAIDs. This study was prospectively registered with PROSPERO (ID: CRD42023417651). A systematic search of electronic databases was performed, for randomized controlled trials reporting topical NSAIDs' outcomes of corneal re-epithelization, rescue analgesics intake, and pain in days 0 to 3 after PRK (postoperative days [PODs] 0 to 3). Studies were graded for risk of bias. Data were extracted, and standardized mean differences (SMDs) were evaluated in a network meta-analysis in accordance with the Cochrane's guidelines, to which a frequentist approach model was fitted. Transitivity was assessed using the net split method. Treatment effectiveness was ranked using forest plots based on comparison with placebo. P-scores (P) and league tables were used to examine combined direct and indirect comparisons. Of 1540 studies identified, 27 were included. These encompassed 2286 patients across 11 countries, evaluating 7 distinct topical NSAIDs. At POD0, ketorolac (P 0.764), flurbiprofen (P 0.763), and bromfenac (P 0.717) were the most efficient drugs overall and displayed significantly lower pain scores than placebo. Other than that, flurbiprofen held the highest rank for reported pain throughout, significantly outperforming placebo on POD1 (P 0.874, SMD -1.19, 95% CI -1.86 to -0.52), POD2 (P 0.882, SMD -1.05, 95% CI -1.82 to -0.27), and POD3 (P 0.939, SMD -1.14, 95% CI -2.1 to -0.18). Other NSAIDs were significantly better than placebo only on POD1 and POD0. Rescue analgesic intake analysis favored indomethacin (P 0.834, SMD -0.8, 95% CI -1.33 to -0.27), ketorolac, and diclofenac. Compared with placebo, re-epithelization was slowed to different significances with all NSAIDs but flurbiprofen (P 0.991, SMD -0.7, 95% CI -1.38 to -0.03). Flurbiprofen was favorable in pain scores on typically painful postoperative days and re-epithelization times. However, analgesics intake, a more objective outcome, suggested superiority of other NSAIDs. Inconsistencies may be explained by the small sample size. For clinical interpretation, NSAID effect sizes should be taken into consideration.

A Novel Procedure for Treating Radial Keratotomy (RK) Induced Corneal Irregularity Utilizing Treatment of Epithelial Compensation of Higher-Order Aberrations and Topographic Guided Ablation-The CREATE Protocol.

To present the outcomes of a retrospective study of treatment of radial keratotomy-induced corneal irregularity with topographic guided ablation and a trans-epithelial approach based on epithelial compensation. Sixty eyes of 31 patients were treated for radial keratotomy-induced corneal irregularity utilizing a customized trans-epithelial topographic guided ablation photorefractive keratectomy (PRK) for treatment of corneal higher-order aberrations and lower-order astigmatism. Three-month results were analyzed via measurement of vision, refraction, residual higher-order aberrations (HOAs), residual lower-order and higher-order aberrations, as well as for loss or gains of lines of best corrected visual acuity. Higher-order aberrations (HOA) were reduced by 69%, with an 80% reduction of higher-order aberrations grouped with lower-order aberrations (Grouped). Most (95%) of eyes achieved 20/40 vision or better, 50% of eyes gained 1-9 lines of best corrected vision, and no eyes had loss of best corrected vision. Use of the CREATE protocol to treat RK-induced corneal irregularity resulted in a significant decrease in HOA, as well as a significant improvement in corrected distance visual acuity.

A 6-Month Follow-Up Comparative Study of Single-Step Transepithelial Photorefractive Keratectomy (Trans-PRK) Using the StreamLight Software with and without Epithelial Thickness Customization.

To compare corneal aberrometry, densitometry, and refractive outcomes of single-step Transepithelial Photorefractive Keratectomy (Trans-PRK) with and without epithelial thickness customization. This was a prospective, interventional, randomized controlled study. Patients undergoing Trans-PRK using the WaveLight EX500 laser with StreamLight software (Alcon Laboratories, Forth Worth, TX, USA) were randomly assigned to control (55µm standard epithelial thickness) or customized (thinnest point of epithelial thickness for each patient) groups. MS-39 (CSO, Italy) anterior segment optical coherence tomography was used to measure the epithelial thickness. Inclusion criteria were spherical equivalent <6 diopters (D), astigmatism <4D, and CDVA 20/25 or better. The assessments were at baseline and 6 months post-op: visual acuity, refraction, aberrometry, and corneal densitometry. 108 eyes were enrolled, [control group (n=56) and customized group (n=52)]. Mean epithelial ablation thickness in the customized group was 54.81±3.56µm (p=0.470 vs control group). Both groups experienced significant postoperative increases in higher-order aberrations (HOA) and spherical aberrations, with no significant intergroup differences. Mean HOA RMS (µm) of the frontal cornea and total cornea increased by 0.27, and 0.29, respectively, in the control group, and 0.26 and 0.28, respectively, in the customized group (p<0.001 for all). Mean change in spherical aberrations in the frontal cornea and total cornea was 0.23µm (p<0.001) and 0.25µm (p<0.001), in the control group, and 0.19µm (p<0.001) and 0.20µm (p<0.001), in the customized group. Mean corneal densitometry in anterior cornea decreased by 0.63GSU (p=0.021) and 1.18GSU (p<0.001) in the control and customized groups. In the posterior cornea, it increased by 1.67GSU (p=0.004) and 0.38GSU (p=0.006). No significant differences in refractive and aberrometry outcomes between control and customized Trans-PRK groups, with corneal densitometry changes not affecting visual acuity.

Factors Predicting Slow Visual Recovery Following Myopic Photorefractive Keratectomy.

To identify factors predicting slow visual recovery following photorefractive keratectomy (PRK). This retrospective study included consecutive patients who underwent PRK between January 2005 and December 2019 at Care Vision Laser Center, Tel Aviv, Israel. Myopic patients were divided into 2 groups according to whether they experienced normal recovery of visual acuity (within 60 days) or slow visual recovery (>60 days). Visual recovery was defined as achieving an efficacy index of 0.9 or greater. Efficacy index was calculated as postoperative uncorrected visual acuity/preoperative best corrected visual acuity. A comparison of baseline and intraoperative parameters was performed. Binary logistic regression was performed to identify potential predictors of slow visual recovery. Overall, 4868 eyes were included. The mean age was 25.9 ± 7.7 years, and 53.9% were male. The slow visual recovery group (39.3%, n = 1911/4868) was older (P < 0.001) and had greater refractive astigmatism (P < 0.001) with a larger proportion of recent contact lens wearers (P = 0.002). The slow recovery group had larger optic zone treatments (P < 0.001), alcohol-assisted PRK (vs. transepithelial PRK) (P < 0.001), and greater maximum ablation depth (P < 0.001). In binary logistic regression, older age (P < 0.001), higher refractive astigmatism (P = 0.01), recent contact lens wear (P = 0.01), greater optic zone treatment (P = 0.001), and alcohol-assisted PRK (P < 0.001) remained significant predictors of slow visual recovery. Slow visual recovery was observed in ∼40% of patients following myopic PRK. Older age, greater refractive astigmatism, recent contact lens wear, greater optic zone treatment, and alcohol-assisted PRK were associated with slow visual recovery.

Activating transcription factor 3 (ATF3) and calcitonin gene-related peptide (CGRP) increase in trigeminal ganglion neurons in female rats after photorefractive keratectomy (PRK)-like corneal abrasion

Photorefractive keratectomy (PRK) is a type of eye surgery that involves removal of the corneal epithelium and its associated nerves, which causes intense acute pain in most people. We used a rat model of corneal epithelium removal (corneal abrasion) to examine underlying cellular and molecular mechanisms. In this study, we used immunohistochemistry of trigeminal ganglion (TG) to assess neuronal content of CGRP and ATF3, as well as orbital tightening (OT) to assess spontaneous pain behaviors. CGRP is an important neuropeptide in pain modulation and ATF3 is often used as a nerve injury marker. We found dynamic changes in CGRP and ATF3 in TG; both increased significantly at 24 h following corneal abrasion and females had a more pronounced increase at 24 h compared to males. Interestingly, there was no sex difference in OT behaviors. Additionally, the number of cells containing either CGRP or ATF3 in each animal correlate significantly with their OT behavior at the assessed timepoint. Since CGRP increased most in females, we tested the effectiveness of Olcegepant, a CGRP antagonist, at reducing OT behaviors following corneal abrasion in female rats. Olcegepant (1 mg/kg) was given prior to and again at 24 h after abrasion but did not change OT behaviors at any time over a 1-week period. Examination of CGRP and ATF3 together in TG showed that they rarely colocalized, indicating that the cells with upregulated CGRP are distinct from those responding to epithelial nerve injury. The studies also show that underlying molecular responses may be sex specific.

Analysis of corneal remodeling post-myopic photorefractive keratectomy with the WaveLight® EX500 excimer laser

Refractive error is becoming a significant public health issue. Photorefractive Keratectomy (PRK) is a corneal surface surgical technique that removes the corneal epithelium before stromal photoablation by ultraviolet radiation from the Excimer laser. We designed a retrospective study to characterize corneal remodeling after myopic Photorefractive Keratectomy and assess the accuracy of laser-predicted ablation depth (AD). This study took place in 15–20 National Ophthalmology Hospital, Paris, France. 150 eyes with preoperative manifest spherical equivalent between − 10.00D and − 0.25D and cylinder < 3D, treated with the WaveLight® EX500 laser between 01/2019 and 01/2023, were followed for at least three months. The main outcome measurements were postoperative changes in epithelial (ET) and stromal (ST) thicknesses measured with spectral domain optical coherence tomography and mean simulated keratometry (SimK) assessed with corneal topography. The central ET significantly decreased at M1, increased over the preoperative value from M1 to M6, and stabilized after M6. The increase in central ET after M1 was associated with an increase in mean SimK (r = 0.34). The achieved AD was 7.9 ± 8.0 µm greater than the laser-predicted AD. Stromal over-ablation was significantly and independently associated with myopia > 6D preoperative mean SimK > 44D and transepithelial procedures.

TRPV1 corneal neuralgia mutation: Enhanced pH response, bradykinin sensitization, and capsaicin desensitization

The factors that contribute to pain after nerve injury remain incompletely understood. Laser-assisted in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK) are common surgical techniques to correct refractive errors. After LASIK or PRK, a subset of patients suffers intense and persistent pain, of unknown origin, described by patients as feeling like shards of glass in their eye. Here, we evaluated a TRPV1 variant, p.V527M, found in a 49-y-old woman who developed corneal pain after LASIK and subsequent PRK enhancement, reporting an Ocular Surface Disease Index score of 100. Using patch-clamp and Ca2+ imaging, we found that the V527M mutation enhances the response to acidic pH. Increasing proton concentration induced a stronger leftward shift in the activation curve of V527M compared to WT, resulting in channel activity of the mutant in acidic pH at more physiological membrane potentials. Finally, comparing the responses to consecutive applications of different agonists, we found in V527M channels a reduced capsaicin-induced desensitization and increased sensitization by the arachidonic acid metabolite 12-hydroxyeicosatetraenoic acid (12-HETE). We hypothesize that the increased response in V527M channels to protons and enhanced sensitization by 12-HETE, two inflammatory mediators released in the cornea after tissue damage, may contribute to the pathogenesis of corneal neuralgia after refractive surgery.

Nominal and achieved stromal ablation depth after myopic transepithelial photorefractive keratectomy: implications for residual stromal thickness calculation

BackgroundThe primary objective of this investigation was to compare the nominal central ablation depth with the achieved central corneal stromal ablation depth after StreamLight transepithelial photorefractive keratectomy (tPRK) for myopia with WaveLight® laser by Alcon Laboratories, TX, USA.MethodsThis ambispective study encompassed a retrospective analysis of 40 eyes who underwent treatment for myopia and astigmatism, followed by a prospective examination conducted 6–9 months postoperatively. Pre- and postoperative Avanti spectral-domain optical coherence tomography (SD-OCT; Optovue Inc., CA, USA) provided stromal and epithelial thickness maps. The difference between pre- and postoperative central stromal thicknesses at the corneal vertex was used to calculate the achieved stromal thickness ablation depth. This value was then compared with the corresponding central nominal depth on the laser ablation planning map.ResultsA total of 40 eyes (OD/OS:18/22) of 40 patients (31.4 ± 9.2 years) were available for evaluation. The mean treated spherical equivalent was − 2.98 ± 1.46 D. The mean nominal and achieved central stromal ablation depths were 51.22 µm and 59.67 μm, respectively, showing a mean stromal excessive ablation of 16.50%. The mean pre- and postoperative central epithelial thicknesses were 53.74 μm and 59.31 μm, respectively, showing a mean postoperative thickness increase of 10.46%. This increase in the epithelial thickness rendered the mean postoperative pachymetry reduction to 54.11 μm, only 2.33% greater than the mean nominal ablation depth.ConclusionsThe study revealed a central stromal ablation 16.50% greater than the nominal ablation depth. This excessive stromal removal was largely compensated for by the increase in epithelial thickness, resulting in a mean difference between the nominal ablation depth and the achieved central corneal pachymetry reduction of only 2.33%. This significant excessive central stromal ablation must be taken into consideration in the calculation of the residual stromal thickness.