Factors affecting long-term myopic regression after corneal refractive surgery for civilian pilots in southwest China.

BACKGROUND: The purpose of this study was to analyze myopic regression after corneal refractive surgery (CRS) in civilian pilots and to explore the factors that may cause long-term myopic regression. METHODS: We included civilian pilots who had undergone CRS to correct their myopia and who had at least 5 years of follow-up. We collected retrospective data and completed eye examinations and a questionnaire to assess their eye habits. RESULTS: A total of 236 eyes were evaluated in this study. 211 eyes had Intrastromal ablations (167 eyes had laser in situ keratomileusis, LASIK, 44 eyes had small incision lenticule extraction, SMILE) and 25 eyes had subepithelial ablations (15 eyes had laser epithelial keratomileusis, LASEK and 10 eyes had photorefractive keratectomy, PRK). The mean preoperative spherical equivalent (SE) was - 2.92 ± 1.11 D (range from - 1.00 to -5.00 D). A total of 56 eyes (23.6%) suffered from myopic regression after CRS. Comparisons of individual and eye characteristics between the regression and non-regression groups revealed statistically significant differences in age, cumulative flight time, postoperative SE (at 6 months and current), uncorrected visual acuity (UCVA), accommodative amplitude (AA), positive relative accommodation (PRA), postoperative period, types of CRS and eye habits. Generalized propensity score weighting (GPSW) was used to balance the distribution of covariates among different age levels, types of CRS, cumulative flying time, postoperative period and continuous near-work time. The results of GPS weighted logistic regression demonstrated that the associations between age and myopic regression, types of CRS and myopic regression, continuous near-work time and myopic regression were significant. Cumulative flying time and myopic regression, postoperative period and myopic regression were no significant. Specifically, the odds ratio (OR) for age was 1.151 (P = 0.022), and the OR for type of CRS was 2.769 (P < 0.001). The OR for continuous near-work time was 0.635 with a P value of 0.038. CONCLUSIONS: This is the first report to analyze myopic regression after CRS in civilian pilots. Our study found that for each year increase in age, the risk of civilian pilots experiencing myopic regression was increased. Intrastromal ablations had a lower risk of long-term myopia regression than subepithelial ablations. There is a higher risk of myopic progression with continuous near-work time > 45 min and poor accommodative function may be related factors in this specific population.

Fourier analysis of corneal irregular astigmatism after small-incision lenticule extraction and transepithelial photorefractive keratectomy: A comparative study.

To compare changes in the spherical component, regular astigmatism, and irregular astigmatism of the anterior surface of the cornea after small-incision lenticule extraction (SMILE) and transepithelial photorefractive keratectomy (TransPRK). Fifty-six patients underwent SMILE in 56 eyes, and 68 patients underwet TransPRK in 68 eyes. The right eye was chosen to enter the group. Six months after the procedure, Scheimpflug images were acquired, and Fourier analysis of the anterior surface of patients' corneas was performed using the Pentacam built-in software. Fourier parameters encompass various measurements such as the steepest radius of the curvature and average eccentricity of the spherical components (SphRmin and SphEcc), maximum decentration (MaxDec), central and peripheral regular astigmatism (regular astigmatism at the center [AstC] and regular astigmatism at the periphery [AstP]), and irregularity (Irr). At 6 months postoperatively, SphEcc decreased significantly (P < .001), MaxDec increased significantly (P < .001), and Irr increased insignificantly (P = .254) in the SMILE group. SphEcc decreased significantly (P < .001) and MaxDec and Irr increased significantly (P < .001) in the TransPRK group. TransPRK caused greater changes in SphEcc, MaxDec, and Irr on the anterior corneal surface than SMILE (P < .05). The amount of MaxDec-induced changes in SMILE and TransPRK was significantly correlated with the amount of higher-order aberrations and spherical aberration changes (P < .05). SMILE and TransPRK increase overall irregular astigmatism on the anterior surface of the cornea, more so with TransPRK, where changes in decentration are associated with with increased higher-order aberrations.

Prevention and Treatment of Persistent Epithelial Defects After Common Refractive Surgery Procedures.

PURPOSE: To discuss the prevention and treatment of persistent epithelial defects after the most common refractive surgeries-photorefractive keratectomy, laser in situ keratomileusis, or small incision lenticule extraction. METHODS: PubMed was used to search the medical literature. RESULTS: Persistent epithelial defects are infrequent after photorefractive keratectomy, laser in situ keratomileusis, or small incision lenticule extraction. In the authors' opinion, any persistent epithelial defect present at 1 week or beyond after surgery should be treated aggressively with a properly fit bandage contact lens, lubrication with non-preserved artificial tears, and treatment of any eyelid abnormalities, including nocturnal lagophthalmos. Consideration should be given for presumptive treatment for herpes simplex virus or varicella zoster virus infection. If the persistent epithelial defect does not close within 2 weeks, then other measures should be considered, such as autologous serum drops, topical losartan, amniotic membranes, and topical human recombinant nerve growth factor to limit corneal scarring fibrosis and microbial infection. CONCLUSIONS: Persistent epithelial defects are among the most feared complications of refractive surgery. Timely and aggressive treatment should be instituted to close the epithelium prior to the development of scarring fibrosis and/or microbial corneal infection. [J Refract Surg. 2024;40(2):e117-e124.].

Factors Predicting the Need for Re-treatment After Laser Refractive Surgery in Patients With Mixed Astigmatism.

PURPOSE: To identify risk factors that increase the likelihood of re-treatment following refractive surgery in patients with mixed astigmatism. METHODS: This was a retrospective study including patients who underwent either laser in situ keratomileusis (LASIK) or photorefractive keratectomy (PRK) between 2000 and 2019 and had mixed astigmatism (spherical error of +0.50 D or greater and spherical equivalent of less than 0.00 diopters [D]). Patients were divided into two groups according to whether they underwent re-treatments during the study period. RESULTS: Overall, 785 eyes (785 patients) were included. In total, 5.2% of the eyes (n = 41) underwent re-treatment. The re-treatment group was more likely to have preoperative high astigmatism (80.5% vs 48.3%, P < .001), moderate to high hyperopia (36.6% vs 22.3%, P = .035), and to have undergone surgery earlier during the study period (P < .001). They were also more likely to have undergone surgery using the Wave-Light EX200 rather than the EX500 laser platform (Alcon Laboratories, Inc) (P < .001), have a treated optical zone of 6 mm rather than 6.5 mm (P < .001 for both), and their maximum ablation depth was greater (P < .001). There was no difference between the re-treatment and control groups regarding procedure type (PRK vs LASIK). Binary logistic regression found preoperative high astigmatism (odds ratio = 3.97, P < .001) and the type of laser platform used (EX200, odds ratio = 7.78, P < .001) as the only independent factors associated with re-treatment. CONCLUSIONS: Re-treatment rates following correction of mixed astigmatism were 5.2% over 20 years. Use of a sixth-generation laser platform significantly reduced the risk of re-treatment. Presence of high astigmatism is a significant risk factor for re-treatment. There was no difference in retreatment risk between PRK and LASIK. [J Refract Surg. 2024;40(2):e73-e78.].

Refractive results of photorefractive keratectomy comparing trans-PRK and PTK-PRK for correction of myopia and myopic astigmatism.

PURPOSE: To compare refractive outcomes after transepithelial photorefractive keratectomy (tPRK) and combined phototherapeutic keratectomy (PTK-PRK) procedure using two different excimer laser platforms for correction of myopia and myopic astigmatism. METHODS: In this retrospective multicenter study, we compared the results of two different PRK methods. The first group received a tPRK treatment with the Amaris750 excimer laser (Schwind eye-tech solutions). The second group received a combined PTK-PRK treatment with the MEL90 excimer laser (Carl Zeiss). Only healthy eyes with no previous surgery and a spherical equivalent (SE) of -1 to -8 diopters (D) were included. Preoperative spherical equivalent (SE), age, and sex were matched among the two groups. All treatments were performed by the same surgeon in different clinics. This study was approved by the local Ethics Committee (No. 2022-1980). RESULTS: We included 154 eyes of 86 patients in our study. There was no difference in predictability of SE between the two groups. Efficacy and safety indices were equally high in both groups. Similarly, no significant differences were seen in change of higher order aberrations (HOA) between the two groups (p > 0.05). No complications occurred. CONCLUSION: Both investigated methods provide safe and effective refractive results. The combination of PTK with PRK may be a suitable option to the already used one-step tPRK for the correction of myopia.

Corneal pseudoectasia: a case series.

OBJECTIVE: To raise awareness of conditions that can tomographically mimic corneal ectasia and describe the actions required to avoid misdiagnosis. METHODS: We report a retrospective case series of seven patients presenting at two tertiary care centers in Israel with a presumed diagnosis of keratoconus or post-refractive ectasia. Upon further examination, the ectasia diagnosis was reconsidered and eventually ruled out. RESULTS: Included were ten eyes of seven patients. Cases included bilateral diffuse Salzmann's nodular degeneration, ophthalmoplegia with strabismus which precluded proper fixation during the acquisition of tomography images, two cases of incorrect Pentacam parameter settings, a patient with a history of hyperopic laser-assisted in situ keratomileusis (LASIK) treatment in one eye and myopic LASIK in the fellow eye, a case of old post-photorefractive keratectomy (PRK) stromal haze, and a patient with posterior polymorphous corneal dystrophy. CONCLUSIONS: Tomography patterns mimicking corneal ectasia can appear in patients without ectatic pathology. The comprehensive ophthalmologist should be aware of such cases as they may substantially alter the treatment course and prognosis of these patients.

Comparison of refractive surgeries (SMILE, LASIK, and PRK) with and without corneal crosslinking: systematic review and meta-analysis.

Corneal crosslinking (CXL) is used for treating keratoconus and post-laser in situ keratomileusis ectasia. However, refractive surgery is not usually performed with prophylactic CXL. Therefore, we performed a meta-analysis comparing outcomes of refractive surgeries with vs without prophylactic CXL. We systematically searched databases for studies comparing refractive surgeries for myopic correction with vs without prophylactic corneal crosslinking. Review Manager 5.4.1 was used to perform statistical analysis. We included 2820 eyes from 28 studies. Compared with refractive surgery alone, surgery with prophylactic CXL resulted in decreased central corneal thickness, corrected distance visual acuity logMAR, and safety and efficacy indices. There were no significant differences in postoperative uncorrected distance visual acuity of 20/20 or better at ≥12 months and other visual outcomes among both groups. More randomized controlled trials with standard crosslinking protocols are needed to analyze the prophylactic use of crosslinking with refractive surgeries.

Investigation of corneal epithelial thickness and irregularity by optical coherence tomography after transepithelial photorefractive keratectomy.

CLINICAL RELEVANCE: Corneal epithelial healing after refractive surgery is a clinically significant issue, especially for surface ablation procedures, and this can be monitored using optical coherence tomography (OCT). BACKGROUND: The aim of this work is to investigate the corneal epithelial thickness and irregularity by OCT after transepithelial photorefractive keratectomy (t-PRK) and analyse its correlation with visual and refractive outcomes. METHODS: Patients aged ≥18 years with myopia, with or without astigmatism, who underwent t-PRK between May 2020 and August 2021 were included. All participants were subjected to complete ophthalmic examinations and OCT pachymetry at every follow-up visit. Patients were followed up at 1 week and 1, 3, and 6 months postoperatively. RESULTS: A total of 67 patients (126 eyes) were enrolled in this study. One month postoperatively, spherical equivalent refraction and visual acuity achieved preliminary stability. However, central corneal epithelial thickness (CCET) and standard deviation of the corneal epithelial thickness (SDcet) took 3-6 months to progressive recovery. Patients with higher baseline spherical equivalent refraction were associated with slower epithelial recovery. At every follow-up time point, a significant superior-inferior difference in the minimum corneal epithelial thickness area was observed. Higher stromal haze was correlated with higher spherical equivalent refraction (both baseline and residual) but had no relation with visual outcomes. There was a significant correlation between higher CCET with a better uncorrected distance visual acuity and lower corneal epithelial thickness irregularity. CONCLUSIONS: CCET and SDcet measured by OCT seem to be a good auxiliary indicator for reflecting the status of corneal wound recovery after t-PRK surgery. However, a well-designed randomised control study is needed to confirm the study results.

Corneal Irregularity Induced by Transepithelial Photorefractive Keratectomy in a Patient With Partial Limbal Stem Cell Deficiency.

PURPOSE: The aim of this study was to present a case of transepithelial photorefractive keratectomy (trans-PRK) laser ablation in a patient with partial limbal stem cell deficiency (LSCD) that resulted in corneal irregularity. METHODS: A 23-year-old man with bilateral partial LSCD underwent trans-PRK for myopia correction 2 months before presentation to our department. Trans-PRK ablation was performed with a phototherapeutic keratectomy ablation profile set at 60 µm in the OD and 57 µm in the OS and 8 mm zone. At the time of presentation, the patient complained of decreased visual acuity. Corrected distant visual acuity was 20/20 (-3.25, -0.75 × 180 degrees) and 20/50 (-3.00, -3.00 × 180 degrees) in the OD and the OS, respectively. No further ocular history was reported other than prolonged soft contact lens use for myopia. Pre-trans-PRK tomography (WaveLight Oculyzer II diagnostic system, WaveLight GmbH, Germany) revealed bilateral superior steepening with corresponding epithelial thinning as obtained by the epithelial map using Optovue optical coherence tomography (Visionix Luneau technology). Slit-lamp examination showed bilateral superficial neovascularization, suggestive of early-stage LSCD. RESULTS: A nonuniform laser stromal ablation resulting in corneal irregularity and decreased visual acuity was observed 2 months postoperatively. During the 6-month follow-up, corneal tomography was stable with only minimal improvement. At that time, corrected distant visual acuity remained 20/20 (-2.75, -0.75 × 160 degrees) in the OD and 20/50 (-3.00, -3.00 × 180 degrees) in the OS. CONCLUSIONS: Trans-PRK seems to be a contraindication in cases with corneal epithelial irregularities and could lead to abnormal and nonuniform stromal ablation .

Photorefractive keratectomy in flat, normal, and steep corneas.

PURPOSE: To compare photorefractive keratectomy (PRK) outcomes in patients with different corneal steepness. SETTING: Care-Vision Laser Center, Tel-Aviv, Israel. DESIGN: Retrospective comparative chart review. METHODS: Patients included in this study underwent wavefront optimized myopic PRK between January 2013 and December 2019. Patients were divided into 3 groups based on the steepness of the cornea (steep keratometry) (flat: <42 diopters [D], normal: 42 to 46 D and steep: >46 D). One to one matching was performed to verify that baseline parameters (age, preoperative visual acuity and refractive error) were similar between groups. Primary outcome measures were: postoperative corrected/uncorrected distance visual acuity (CDVA/UDVA), efficacy index (postoperative UDVA/preoperative CDVA), safety index (postoperative CDVA/preoperative CDVA), spherical equivalence (SEQ) and cylinder. RESULTS: After matching, 650 eyes were included in each group, which were similar in baseline parameters. There were no significant postoperative differences between flat, normal, and steep corneas in terms of safety index (1.02 vs 1.03 vs 1.03, P = .28), efficacy index (1.01 vs 1.01 vs 1.02, P = .57), logMAR CDVA (0.01 vs 0.02 vs 0.01, P = .76), logMAR UDVA (0.02 vs 0.03 vs 0.02, P = .68), %SEQ within 0.50 D (73.9% vs 74.2% vs 74.6%, P = .95) or 1.00 D of target (91.9% vs 92.5% vs 92.2%, P = .92), %cylinder within 0.50 D (82.8% vs 82.2% vs 81.4%, P = .81) or 1.00 D of target (96.9% vs 97.1% vs 97.2%, P = .95). CONCLUSIONS: No significant differences were found between flat, normal and steep corneas following wavefront-optimized myopic PRK. Thus, this procedure may be safely and effectively performed in both flat and steep corneas.

Intrastromal Corneal Ring Segment Implantation Followed by Simultaneous Topography-Guided Photorefractive Keratectomy and Corneal Cross-Linking for Contact Lens-Intolerant Keratoconus.

PURPOSE: This study aimed to evaluate the efficacy and safety of Keraring implantation followed by simultaneous topography-guided photorefractive keratectomy (TGPRK) and corneal cross-linking (CXL) in the management of keratoconus. METHODS: This is a single-center, private practice, retrospective review. Patients with keratoconus who were intolerant to contact lens wear underwent implantation of the Keraring, followed by TGPRK with CXL from 2 to 36 months after implantation. Main outcome measures were uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), refraction (cylinder and spherical equivalent), keratometry (steep, maximum, and central), and central corneal thickness (CCT). Patients were followed up for 3 to 60 months postoperatively. RESULTS: Fifty-seven eyes from 45 patients were included. The mean time between Keraring and TGPRK/CXL was 6.0 ± 6.0 months. Patients were followed up for a mean of 28.6 ± 20.1 months after Keraring insertion. At 12-month follow-up, there was a statistically significant improvement in mean UDVA (0.94 ± 0.49-0.35 ± 0.23, P < 0.01), CDVA (0.39 ± 0.26-0.17 ± 0.15, P < 0.01), cylinder (-4.97 ± 2.68 to -1.74 ± 1.25, P < 0.01), steep keratometry (51.25 ± 3.37-45.03 ± 2.27, P < 0.01), central keratometry (52.59 ± 4.98-46.99 ± 3.53, P < 0.01), and maximum keratometry (58.78 ± 4.22-50.76 ± 3.42, P < 0.01). These results were sustained at 48-month follow-up. CCT decreased at 12 months after TGPRK (461.84 ± 27.46-418.94 ± 45.62, P < 0.01) and remained stable at 60 months. Postoperatively, 2 eyes (3.51%) had corneal haze, resulting in decrease in CDVA; 1 was treated successfully with repeat PRK; and 1 patient (1.75%) had wound melt due to partial Keraring extrusion, which settled with repositioning. CONCLUSIONS: Keraring implantation followed by simultaneous TGPRK and CXL appears to be effective in the long term in improving UDVA, CDVA, cylinder, CCT, and keratometry in patients with keratoconus who are intolerant to contact lenses.

Ray-Tracing Transepithelial Excimer Laser Central Corneal Remodeling Plus Pachymetry-Guided Accelerated Corneal Crosslinking for Keratoconus.

PURPOSE: The aim of this study was to report the 12 to 96 months results of a tissue-preservation algorithm based on ray-tracing-guided transepithelial excimer laser central corneal ablation (RT t-PRK) combined with individualized pachymetry-guided accelerated crosslinking (M nomogram ACXL) in young adult patients with stable keratoconus (KC). METHODS: This was a prospective interventional study including 38 eyes of 38 young adult patients (stage II KC) with a mean age of 35 years (range 26-46 years) who underwent simultaneous RT with t-PRK plus pachymetry-based ACXL in the worst eye. The treatments were performed using the iViS Suite iRES Excimer Laser (Ligi, Taranto, Italy). Ray-tracing-guided treatments were planned using the customized interactive programmed transepithelial ablation (CIPTA) 2 web software and diagnostic data were assessed by the Precisio 2 tomographer (Ligi, Taranto, Italy) and Sirius tomographer (C.S.O., Florence, Italy). The main outcome measures included uncorrected distance visual acuity, best spectacle-corrected visual acuity, Kmax, high-order aberrations, minimum corneal thickness, and posterior elevation, with a mean follow-up of 52 months (range 12-96 m). RESULTS: The mean UDVA improved + 3.5 ±1.28 Snellen lines (SL); 38% gained ≥ 4 ±1.34 SLs, 35% ≥ 3 ±1.21 SLs, 22% ≥ 2 ±1.12 SLs, and 5% ≥ 1 ±0.75 SLs. The mean best spectacle-corrected visual acuity increased by + 4.3 ±1.3 SL. Sixty-eight percent gained ≥ 4 ±0.88 SLs and 30% ≥ 3 ±0.78 SL. No SLs were lost. CONCLUSIONS: RT t-PRK plus ACXL significantly improved the quality of vision in patients with KC, preventing overcorrection and minimizing tissue consumption.

Evaluation of the effect of artificial tears on corneal epithelial thickness changes after photorefractive keratectomy.

PURPOSE: This study aimed to evaluate the corneal epithelial thickness changes after photorefractive keratectomy (PRK) and the impact of long-term artificial tear usage on epithelial thickness changes in these patients. METHODS: This study was performed on 71 patients (142 eyes) without dry eye disease who received PRK for myopic refractive correction. The corneal epithelial thickness profile was obtained before, one, three, and six months after surgery using anterior segment optical coherence tomography. Patients were randomly divided into two groups: group A, who received preservative-free artificial tears post-surgery, and group B, who did not receive artificial tears. RESULTS: The epithelial thickness decreased universally in the first month and then increased in the 3- and 6-month follow-ups. Group A had a significantly thicker epithelium in central, paracentral, and midperipheral zones compared with group B in the 3-month follow-up. In the 6-month follow-up, no significant differences were detected between groups. At the last follow-up, the central, paracentral, and midperipheral zone epithelial thicknesses in all patients were significantly higher than preoperative values, but peripheral zone thickness only increased to preoperative values. CONCLUSIONS: Patients using artificial tears showed a faster thickening, especially in the central and paracentral zones, but there were no significant differences between the two groups in the final follow-up. Artificial tear usage may increase the rate of the epithelial remodeling process in post-PRK patients without significantly altering the final epithelial thickness profile. Further studies are warranted to evaluate the influence of different factors on epithelial remodeling.

Sequential Customized Therapeutic Keratectomy in Patients With a History of Radial Keratotomy.

PURPOSE: To evaluate the outcome of sequential customized therapeutic keratectomy (SCTK) in reducing higher order aberrations (HOAs) and improving quality of vision in highly aberrated corneas consequent to previous radial keratotomy (RK). METHODS: A retrospective review of patients undergoing SCTK treatment from January 2012 to October 2020 was conducted in the Eye Center, Humanitas Clinical and Research Center (Rozzano, Italy). Indications for treatment in patients who had RK were significantly and/or progressively reduced corrected distance visual acuity (CDVA) combined with visual symptoms critically affecting quality of life. Preoperative and postoperative CDVA, corneal topography and aberrometry, Scheimpflug tomography, and anterior segment optical coherence tomography were registered. RESULTS: Thirty-four patients who underwent RK a mean of 26.62 ± 7.10 years before SCTK treatment were included. SCTK induced a significant improvement of CDVA from 0.44 ± 0.82 logMAR preoperatively to 0.15 ± 0.64 logMAR postoperatively (P < .001). No patient experienced worsening of CDVA, whereas 8 patients (23,50%) gained one line and 23 patients (67.65%) gained two lines or more. A significant decrease in corneal coma, trefoil, and spherical aberrations was also noted (P = .003, .003, and .004, respectively). CONCLUSIONS: SCTK proved to be a safe and effective option to treat highly aberrated eyes following RK. The authors suggest the use of SCTK as a first-line approach for the treatment of HOAs after RK and avoiding more invasive procedures such as corneal transplantation or intraocular lens implantation. [J Refract Surg. 2023;39(12):808-816.].

Late-Onset Chronic Corneal Fistula Following Phototherapeutic Keratectomy: A Case Report and Importance of Early Detection.

BACKGROUND We report a case of late-onset chronic fistula in a decompensated cornea after multiple ocular surgeries and a recent phototherapeutic keratectomy (PTK). CASE REPORT A 73-year-old woman presented to our service with a past ocular history of bilateral chronic angle closure glaucoma and pseudophakic bullous keratopathy in the left eye. Given a history of long-term uncontrolled glaucoma with advanced disc cupping and poor visual potential, the patient underwent multiple palliative procedures, including, most recently, a PTK. Few years later she presented with a spontaneous late onset of slowly appearing corneal leak on fluorescein staining upon routine clinical examination. Corrected distance visual acuity was hand motion and intraocular pressure (IOP) was 40 mmHg in the affected eye. Serial anterior segment optical coherence tomography (AS-OCT) sections were obtained, which aided in understanding the current presentation and revealed distinctive multilayer corneal changes during the healing process. The patient was successfully managed with cyanoacrylate corneal gluing and ocular hypotensive medications, which halted the corneal leak. CONCLUSIONS We report a case of a rare finding of corneal fistula in an eye with multiple previous ocular surgeries, and provide an explanation of the possible etiopathogenesis. We also highlight the pivotal role of AS-OCT for evaluating such cases and stress the importance of early detection of similar subtle leaks in the setting of a formed anterior chamber, which can often be missed, carrying a risk of infection.

Mechanical Epithelial Debridement versus Transepithelial Phototherapeutic Keratectomy Followed by Accelerated Corneal Collagen Crosslinking for Progressive Keratoconus.

OBJECTIVE: To compare the visual and topographic outcomes between mechanical epithelial debridement followed by accelerated corneal collagen cross linking (CXL) vs. transepithelial phototherapeutic keratectomy followed by accelerated CXL for treatment of progressive keratoconus. STUDY DESIGN: Quasi experimental study. Place and Duration of the Study: Armed Forces Institute of Ophthalmology (AFIO), National University of Medical Sciences, Rawalpindi, Pakistan, from December 2020 to December 2021. METHODOLOGY: On the basis of surgical technique used, patients were divided into two groups, Group A comprising of twenty eyes that underwent mechanical epithelial removal followed by accelerated CXL, and Group B comprising of twenty-two eyes that underwent transepithelial phototherapeutic keratectomy (t-PTK) followed by accelerated CXL. All variables were recorded preoperatively and 6 and 12 months postoperatively and included uncorrected visual acuity (UCVA), corrected distance visual acuity (CDVA), MRSE (manifest refraction spherical equivalent), and keratometric indices (flat K, steep K, Kmax , mean K, thinnest pachymetry, KPI, K prob, CLMIaa, and I-S). RESULTS: Forty-two eyes of twenty-nine patients were included in the study and were divided into two groups; Group A (mechanical epithelial removal followed by accelerated CXL) and Group B (t-PTK followed by accelerated CXL). The visual acuity improved in both the groups at 6 and 12 months, with more significant improvement in Group B in both UCVA (p=0.005) and CDVA (p=0.004) parameters. Keratometric outcomes showed significant differences in median values for flat K (p=0.048) and thinnest pachymetry (p=<0.001) in Group A, while significant difference in Kmax (p=0.024) and thinnest pachymetry (p=<0.001) in Group B. At 6 and 12 months, the CLMIaa, PPK, and I-S values were significantly lower in Group B (p=0.002 for all three indices). CONCLUSION: Transepithelial PTK followed by accelerated CXL yielded better outcomes regarding visual acuity and keratomertic indices as compared to mechanical epithelial removal followed by accelerated CXL and did not show any significant decrease in corneal pachymetry. KEY WORDS: Mechanical, Corneal Collagen Crosslinking (CXL), Transepithelial, Phototherapeutic keratectomy, Keratoconus.

Late approach for LASIK flap striae.

A 24-year-old man was referred for postrefractive surgery evaluation. The patient had a history of uneventful laser in situ keratomileusis (LASIK) in both eyes 3 months previously. According to the surgeon who originally performed the surgery, on slitlamp examination, only microstriae in the left eye was detected on postoperative day 1 and a more conservative follow-up approach was adopted without further immediate intervention. The patient returned only 3 months after surgery, complaining of low vision in the left eye that, according to the patient, had been present since postoperative week 2. The patient was then referred for examination and surgical procedure with a diagnosis of significant postoperative striae. The slitlamp examination revealed a LASIK flap with striae, epithelial filling, and a wrinkled appearance (Figure 1JOURNAL/jcrs/04.03/02158034-202312000-00017/figure1/v/2023-11-20T151558Z/r/image-tiff). There were no signs of infection or inflammation. Originally, the LASIK flap was programmed to be 110 µm. Preoperative manifest refraction in the right eye was -5.25 (20/20) and in the left eye was -5.25 (20/20). Assuming it is a case of late-approach LASIK flap striae, how would you proceed? Would you try to hydrate and lift the flap and just reposition it? Would you avoid lifting and associate phototherapeutic keratectomy (PTK) with excimer laser on top of the flap? Would you consider topo-guided surgery with regularization of the visual axis or even amputation of the flap?

Collagen crosslinking impacts stromal wound healing and haze formation in a rabbit phototherapeutic keratectomy model.

Purpose: The purpose of this study was to evaluate the elastic modulus, keratocyte-fibroblast-myocyte transformation, and haze formation of the corneal stroma following combined phototherapeutic keratectomy (PTK) and epithelium-off UV-A/riboflavin corneal collagen crosslinking (CXL) using an in vivo rabbit model. Methods: Rabbits underwent PTK and CXL, PTK only, or CXL 35 days before PTK. Rebound tonometry, Fourier-domain optical coherence tomography, and ultrasound pachymetry were performed on days 7, 14, 21, 42, 70, and 90 post-operatively. Atomic force microscopy, histologic inflammation, and immunohistochemistry for α-smooth muscle actin (α-SMA) were assessed post-mortem. Results: Stromal haze formation following simultaneous PTK and CXL was significantly greater than in corneas that received PTK only and persisted for more than 90 days. No significant difference in stromal haze was noted between groups receiving simultaneous CXL and PTK and those receiving CXL before PTK. Stromal inflammation did not differ between groups at any time point, although the intensity of α-SMA over the number of nuclei was significantly greater at day 21 between groups receiving simultaneous CXL and PTK and those receiving CXL before PTK. The elastic modulus was significantly greater in corneas receiving simultaneous CXL and PTK compared with those receiving PTK alone. Conclusions: We showed that stromal haze formation and stromal stiffness is significantly increased following CXL, regardless of whether it is performed at or before the time of PTK. Further knowledge of the biophysical cues involved in determining corneal wound healing duration and outcomes will be important for understanding scarring following CXL and for the development of improved therapeutic options.

Evaluation of the efficiency and safety of TransPRK and FS-LASIK refractive procedures on patients with astigmatism and amblyopia.

Purpose: To compare the outcomes of transepithelial photorefractive keratectomy (transPRK) with femtosecond laser assisted in situ keratomileusis (FS-LASIK) for the correction of astigmatism on amblyopic eyes. Methods: The design was a retrospective interventional study on 37 eyes with hyperopic or mixed astigmatism and refractive amblyopia, which underwent transPRK or FS-LASIK. The patients were distributed into 2 groups according to the technique used. Data was collected from patient files and comparison between groups was performed. The main outcomes measured were corrected distance visual acuity (CDVA), sphere, cylinder, spherical equivalent (SEQ), efficiency and safety indexes. Results: In the transPRK group, SEQ improved significantly after 1 month, from 2.08 ± 2.02D (p<0.01) to 0.125 ± 0.86D and at the 12 month visit to -0.04 ± 0.62D (p>0.05), sphere improved from 4.03 ± 1.44D preoperatively to 0.67 ± 0.9D at 1 month (p<0.05) and further to 0.44 ± 0.71 at 12 months (p<0.05). CDVA improved from 0.194 ± 0.11 logMAR to 0.115 ± 0.1 logMAR at the 1-year visit. Safety index after 1 month was 1.09 ± 0.2 and 1.12 ± 0.35 at the 1-year visit. Efficiency index was 0.95 ± 0.22 at 1 month and 1.03 ± 0.34 after 1 year. In FS-LASIK group, SEQ improved after 1 month, from 2.28 ± 3.04 to -0.79 ± 0.73D (p<0.01), and further to -0.49 ± 0.79 (p>0.05) at the 12 month visit, sphere improved from 4.11 ± 2.35D preoperatively to -0.42 ± 0.66D at 1 month (p<0.05) and further to -0.08 ± 0.75D at 12 months (p<0.05). CDVA also improved from 0.191 ± 0.1 logMAR to 0.140 ± 0.1 logMAR at 1 year. Safety index after 1 month was 1.1 ± 0.2 and 1.16 ± 0.21 at the 1-year visit. Efficiency index was 0.98 ± 0.27 at 1 month and 1.06 ± 0.23 after 1 year. Conclusion: Both procedures were safe and efficient in improving visual acuity for patients with mixed and hyperopic astigmatism and refractive amblyopia. Abbreviations: transPRK = transepithelial photorefractive keratectomy, FS-LASIK = femtosecond laser in situ keratomileusis, logMAR = logarithm of the Minimum Angle of Resolution, BCVA = best corrected distance visual acuity, CDVA = corrected distance visual acuity.

Intraocular pressure after combined photorefractive keratectomy and corneal collagen cross-linking for keratoconus.

PURPOSE: The purpose of this prospective study was to evaluate the effect of combined photorefractive keratectomy (PRK) and corneal collagen cross-linking (CXL) on intraocular pressure (IOP) in patients with keratoconus (KC). METHODS: We included 64 eyes of 34 patients (19 males and 15 females; age: 19-40y) with stages 1-2 keratoconus which had undergone combined wavefront-optimized photorefractive keratectomy and corneal collagen cross linking. Two other groups of patients were added as controls: the PRK group including 110 eyes of 57 patients (23 males and 34 females; age: 18-44y) which had undergone wavefront-optimized photorefractive keratectomy for myopic refractive errors, and the CXL group including 36 eyes of 23 patients (14 males and 9 females; age: 12-38y) with keratoconus, not filling the inclusion criteria for combined PRK and CXL, which had undergone corneal collagen cross-linking. IOP was recorded preoperatively and postoperatively at 3, 6 and 12 months follow-up visits. RESULTS: Preoperative IOP in both CXL (12.1 ± 2.53 mmHg) and PRK + CXL (13.2 ± 2.50 mmHg) groups was significantly lower than PRK group (15.8 ± 3.10 mmHg) (F = 30.505, p < 0.001). At 3 months postoperatively, IOP showed no statistically significant difference between the three studied groups (F = 1.821, p = 0.164). At 6 months postoperatively, IOP in the CXL group (14.6 ± 2.64 mmHg) was significantly higher than both PRK (13.4 ± 2.27 mmHg) and PRK + CXL (13.3 ± 2.62 mmHg) groups (F = 3.721, p = 0.026). At 12 months postoperatively, IOP in the CXL group (14.3 ± 2.69 mmHg) was significantly higher than the PRK group (13.2 ± 2.23 mmHg) and was higher than PRK + CXL group (13.3 ± 2.59 mmHg) although not statistically significant (F = 3.393, p = 0.035). Regarding the percent of change from preoperative IOP, a statistically significant difference between the three studied groups was detected at 3, 6 and 12 months postoperatively (H = 117.459, 109.303, 122.694 respectively, p < 0.001). The median percent of change from preoperative IOP in the PRK group was -16.7%, -15%, and -16.7%, in the CXL group was + 14.3%, + 19.4%, and + 19.1%, while in PRK + CXL group was 0% at 3, 6 and 12 months postoperatively. (Post-hoc power analysis 75%). CONCLUSIONS: Combined PRK and CXL in patients with KC shows no significant effect on IOP, in contrast to either procedure performed separately.