Inlays and the cornea.

Presbyopia is a growing problem in view of an aging global population and increasingly patients desire spectacle-free solutions to address this condition. Surgically implanted corneal inlays have been the topic of renewed research efforts in the past several years as a treatment option for presbyopia, with several approaches being used to modify the refractive properties of the cornea and enhance near vision. In this review we discuss historical approaches to corneal inlay surgery, critically appraise the current generation of presbyopia-correcting corneal inlays and their associated complications and consider the future prospects for emerging corneal inlay technologies that aim address the shortcomings of currently available inlays.

A Multicenter Study of the Prevalence of Dry Eye Disease in Chinese Refractive Surgery Candidates.

OBJECTIVE: The aim of this study was to determine the prevalence of preoperative dry eye disease and evaluate tear film function in refractive surgery candidates in China. METHODS: In this prospective noninterventional cross-sectional study, refractive surgical candidates from 13 preselected eye hospitals in China were recruited from July 2015 to February 2016. Patient histories, subjective symptoms, tear film breakup time (TBUT), ocular surface fluorescein staining, and Schirmer I tests (SIT), were assessed to conduct subgroup analysis. RESULTS: A total of 1,849 patients were recruited, 41.4% were diagnosed with dry eye disease (766/1,849) and 44.9% (830/1,849) of subjects had a positive history of contact lens (CL) wear. The overall mean TBUT and SIT values were 7.3 ± 3.7 s and 15.2 ± 8.8 mm, respectively. The total prevalence of ocular surface fluorescein staining was 23.46% (422/1,849); 44.62% of patients had TBUT <5 s and 23.20% of patients had SIT <5 mm. CL wearers were observed to have a higher prevalence of dry eye than non-CL wearers (54.1 vs. 35.2%, OR = 2.17, 95% CI: 1.77-2.65). CONCLUSIONS: In this study, the most common abnormal finding in dry eye disease was tear film instability. A high proportion of refractive surgery candidates have preexisting dry eye disease and a history of CL wear prior to surgery. Careful attention should be given to the evaluation of preoperative dry eye in refractive surgery candidates.

[Radial keratotomy: history and current state]. / Radial'naya keratotomiya: istoriya i real'nost'.

Results of clinical use of the radial keratotomy (RK) surgery are presented in the format of a lecture and a summary. The analysis encompasses the mechanism of changes in corneal refraction, immediate intra- and postoperative complications, so-called secondary symptoms and long-term effects (addition of various pathological processes, influence of corneal changes on the results of diagnostic tests and treatment methods) of the surgery.

Hyperopic laser keratorefractive surgery: Do steep corneas have worse outcomes?

PURPOSE: To report the visual and refractive outcomes of hyperopic patients undergoing laser keratorefractive surgery in preoperatively steep corneas versus a matched control group. METHODS: Retrospective cohort study. All patients underwent photorefractive keratectomy (PRK) or laser-assisted in situ keratomileusis (LASIK) at Care-Vision Laser Centers, Tel-Aviv, Israel, between 1/2000 and 11/2016. Patients were divided into two groups: steep corneas (mean keratometry ≥ 44.00 D) and control group (mean keratometry < 44.00 D). The two study groups were matched by age, gender, sphere and cylinder. Only the right eye of each patient was included. Outcomes included postoperative uncorrected distance visual acuity (UDVA), best-corrected distance visual acuity (CDVA), safety and efficacy indexes, refractive outcomes and retreatment rates. RESULTS: Five hundred and two patients were included. Both groups were similar in demographic data, visual acuity and refraction. Postoperatively, the steep corneas group had a significantly higher mean keratometry as compared to the control group (46.52 ± 1.43 D vs 44.58 ± 1.68 D, p < 0.001), Kmin (46.04 ± 1.50 D vs 44.12 ± 1.76 D, p < 0.001) and Kmax (46.99 ± 1.51 D vs 45.03 ± 1.77 D, p < 0.001). Both groups had similar postoperative UDVA and CDVA and achieved a similar final sphere (0.64 ± 0.19 vs 0.54 ± 1.19, p = 0.44) and cylinder (- 0.89 ± 0.59 vs - 0.86 ± 0.72, p = 0.67). Both groups had a similar efficacy index (0.92 ± 0.22 vs 0.90 ± 0.25, p = 0.33) and similar retreatment rates (4.2% vs 3.5%, p = 0.74). None of the patients in either group underwent more than one retreatment throughout the follow-up period. CONCLUSIONS: Hyperopic patients with steep corneas undergoing laser keratorefractive surgery can achieve adequate visual and refractive outcomes, similar to control group.

[The effects of a trehalose-based drug used after laser keratorefractive surgeries]. / Rezul'taty primeneniya preparata na osnove Tregalozy posle lazernykh keratorefraktsionnykh operatsii.

PURPOSE: To analyze the effectiveness of artificial tear drops Thealoz (trehalose 3%) in the correction of dry eye syndrome (DES) after ReLEx SMILE and FEMTO LASIK keratorefractive surgeries. MATERIAL AND METHODS: The study included 20 patients (40 eyes) who underwent a keratorefractive surgery and were prescribed instillations of Thealoz artificial tear drops for the correction of dry eye syndrome. Patients were divided into 2 group: the 1st group consisted of 10 patients who underwent ReLEx SMILE surgery, the 2nd group - 10 patients after FEMTO LASIK. The effectiveness of the treatment was evaluated at 1 and 3 months after the surgery using Ocular Surface Disease Index (OSDI), changes in the anterior corneal epithelium (Oxford scale), and tear break-up time (Norn's test). RESULTS: It was found that the use of artificial tear drops Thealoz regardless of the type of keratorefractive surgery helps reduce discomfort based on the OSDI questionnaire from 10.90±4.55 to 10.20±4.07 and 8.89±3.26 points by 1 and 3 months of the follow-up, respectively (p≤0.05). The degree of epitheliopathy according to the Oxford scale decreases from 0.73±0.75 to 0.25±0.43 points 3 months after the surgery (p≤0.05), which is accompanied by a significant increase in tear break-up time (Norn's test) from 11.18±1.19 to 12.43±1.03 and 12.45±1.03 seconds 1 and 3 months after treatment, respectively (p≤0,05). CONCLUSION: Complex evaluation of the ocular surface has proved that artificial tear drops Thealoz is effective in reducing DES manifestations after keratorefractive surgery. The results clearly demonstrate that the drug helps increase stability of the tear break-up time, as well as contributes to the decrease in epitheliopathy and subjective discomfort sensations, giving grounds to widen its use in clinical practice.

[Biomechanical properties of the cornea and tonometry measurements]. / Biomekhanicheskie svoistva rogovitsy i pokazateli tonometrii.

PURPOSE: To study peculiarities of intraocular pressure (IOP) measurement by different methods in patients with changes in corneal biomechanical properties. MATERIAL AND METHODS: The study enrolled 154 patients (290 eyes) divided into 3 groups according to the condition of their corneas in terms of biomechanical properties. Group I consisted of 84 patients (168 eyes) with conditionally 'normal' cornea and corneal thickness ranging from 470 to 660 µm. Group II included 44 patients (70 eyes) with keratokonus. Group III consisted of 26 patients (52 eyes) after LASIK. IOP pressure was measured in each patient by pneumotonometry, Maklakov tonometry, and dynamic bidirectional pneumo-applanation of the cornea. Biomechanical properties were evaluated with dynamic pneumo-impression method. RESULTS: The study revealed that in patients of groups I and III, corneal biomechanics affected indices of corneal compensated IOP and Maklakov's IOP to a lesser extent, as opposed to measurements of Goldman tonometry and pneumotonometry. In group II, Maklakov's tonometry had less IOP measurement inaccuracies in comparison to other evaluated methods due to larger applanation surface. CONCLUSION: Changes in biomechanical properties of the cornea can complicate interpretation of the results of different methods of IOP measurement. Accurate determination of IOP requires consideration of biomechanical properties of the cornea, as well as anamnesis data on past corneal diseases or keratorefractive surgeries.

[Condition of corneal nerve fibers after laser keratorefractive surgery]. / Sostoianie nervnykh volokon rogovitsy posle lazernykh keratorefraktsionnykh operatsii.

The article reviews studies dedicated to evaluation of corneal nerve fibers (CNF) after various laser keratorefractive methods of correcting refractive error based on confocal microscopy. The matter of studying the dynamics of the condition of CNF after laser keratorefractive techniques continues to be relevant and requires further research with regard to the prevalence of refractive errors on the one hand, and the future life of patients who undergo these procedures, on the other. Certain heterogeneity of the research results presented in this review can be partially explained by the subjective nature of the study algorithm (in particular, the need for manual tracing of nerve fibers) and the lack of objective quantitative indicators of CNF condition suitable for statistical processing.

[Artificial tear drops Thealoz in the correction of dry eye syndrome after keratorefractive surgery]. / Primenenie preparata Tealoz v korrektsii sindroma sukhogo glaza posle keratorefraktsionnykh operatsii.

PURPOSE: To analyze the effectiveness of artificial tear drops Thealoz (trehalose 3%) in the correction of dry eye syndrome (DES) after keratorefractive surgery based on instrumental monitoring of the condition of eye surface. MATERIAL AND METHODS: The study included 20 patients (40 eyes) who underwent a keratorefractive surgery and were prescribed instillations of Thealoz artificial tear drops for the correction of dry eye syndrome. Patients were divided into 2 groups: the 1st group consisted of 10 patients who underwent ReLEx SMILE surgery, the 2nd group - 10 patients after FEMTO LASIK. The effectiveness of the treatment was evaluated at 1 and 3 months after the surgery using conventional instrumental monitoring: tear break-up time (Norn's test), tear film osmolarity test and OCT-meniscometry. RESULTS: Regardless of the type of surgery, tear film break-up time has significantly increased from 11.16±0.38 sec to 12.95±0.24 (p≤0.05) and 13.85±0.03 (p≤0.05) by months 1 and 3, respectively; it correlated with progressive decrease of tear film osmolarity from 317.29±1.39 to 308.00±0.79 mOsm/L (p≤0.05) at one month, and by the 3rd month - to 301.75±0.27 mOsm/L (p≤0.05). An improvement in OCT-meniscometry parameters was also observed in the form of a significant increase of the height and depth after 1 and 3 months. CONCLUSION: The use of artificial tear drops Thealoz contributes to the reduction of DES manifestations after keratorefractive surgery: increased stability of the tear film, restoration of the tear meniscus parameters and tear film osmolarity. The use of trehalose ophthalmic solution is advisable in patients after keratorefractive surgery.

[Visual rehabilitation of patients with large post-traumatic defects of the anterior eye segment through iris-lens diaphragm implantation]. / Sistema zritel'noi reabilitatsii patsientov s obshirnymi defektami struktur perednego otrezka glaznogo iabloka na osnove implantatsii iridokhrustalikovoi diafragmy.

The diversity of methodological approaches and lack of pathogenetically reasonable tactics for patients with combined ocular injuries became the basis for the development and systematization of surgical rehabilitation stages of patients, in whom post-traumatic cataract is combined with post-traumatic aniridia and corneal scarring. AIM: to construct a visual rehabilitation approach to patients with post-traumatic defects of the anterior eye segment following optical-reconstructive surgery that involved implantation of an iris-lens diaphragm (ILD). MATERIAL AND METHODS: We have analyzed 80 reconstructive cases with ILD implantation in patients with post-traumatic aniridia and corneal damage. These patients constituted the first study group (Group 1). We have also investigated 58 eyes with residual ametropy and stable visual function 1 year after ILD implantation before and after conducting a laser keratorefractive surgery. These patients were assigned to the second study group (Group 2). RESULTS: Rehabilitation approach to patients after anterior segment injuries that has been proposed allows to achieve high clinical and functional results and reduce the risk of intra- and postoperative complications. CONCLUSION: The proposed approach to patients after optical-reconstructive surgery with iris-lens diaphragm implantation followed by keratorefractive surgery is an effective method of visual rehabilitation of anterior eye segment post-traumatic defects.

Enhancing ectasia screening using advanced AS-OCT: a case series of challenging refractive candidates.

Purpose: Ectasia screening in candidates for laser refractive surgery is mandatory during preoperative evaluation. Despite the availability of modern imaging techniques, refractive surgeons often face borderline decisions when patients present with suspicious tomographic findings. This case series presents refractive candidates with suspicious tomographic findings and demonstrates how to interpret them using Scheimpflug imaging and additional anterior segment optical coherence tomography (AS-OCT). Setting: Department of Ophthalmology, University Hospital, LMU Munich. Case series: This case series examines six potential candidates for refractive surgery with a mean age of 29.2 ± 3.9 years, whose corneal assessments using Scheimpflug imaging raised suspicion for ectasia. Each candidate was additionally examined with AS-OCT and reevaluated. The mean manifest subjective spherical equivalent was -3.67 ± 1.8 diopters. The total corneal thickness measured 537 µm ± 30 µm at its thinnest point. None of the candidates had any reported underlying corneal or ophthalmic diseases, and slit lamp examinations revealed no abnormal morphological findings. Conclusions: Both Scheimpflug imaging and AS-OCT are appropriate tools for screening refractive candidates for ectasia. While topographic and elevation analyses yielded comparable results regarding corneal structure, the epithelial mapping provided by AS-OCT played a critical role in decision-making for cases with borderline tomographic findings. Establishing a global consensus on the use of epithelial mapping in ectasia screening is necessary.

Comparison of total corneal power measurements obtained with different devices after myopic keratorefractive surgery.

AIM: To analyze the differences, agreements, and correlation among total corneal power parameters generated by different instruments after myopic keratorefractive surgery. METHODS: The prospective cross-sectional study included patients who underwent myopic keratorefractive surgery and received measurements of corneal power 3mo after surgery. Automated keratometer was used for the measurement of simulated keratometry (SimK), swept-source optical coherence tomography (SS-OCT) based biometer for total keratometry (TK), anterior segment-OCT for real keratometry (RK), and Scheimpflug keratometer for the true net power (TNP), the total corneal refractive power (TCRP) and equivalent K-readings (EKR). The differences among these parameters were analyzed, and the agreements and correlation between SimK and other total corneal power parameters were investigated. RESULTS: A total of 70 eyes of 70 patients after myopic keratorefractive surgery were included. The evaluated corneal power parameters were as follows: SimK 38.32±1.93 D, TK 37.54±2.12 D, RK 36.64±2.09 D, TNP 36.56±1.97 D, TCRP 36.70±2.01 D, and EKR 37.55±2.00 D. Pairwise comparison showed that there were significant differences (P<0.001) among all parameters except for between TK and EKR, RK and TNP, RK and TCRP (P=1.000, 1.000, 1.000, respectively). The limits of agreement between SimK and TK, RK, TNP, TCPR, and EKR were 1.08, 1.08, 1.43, 1.48, and 1.73 D, respectively. All parameters showed good correlation with SimK, and the correlation coefficients were 0.995, 0.994, 0.983, 0.982, and 0.975. CONCLUSION: Among the corneal power parameters after myopic keratorefractive surgery, the value of SimK is the largest, followed by TK and EKR, with TCRP, RK, and TNP being the smallest. The differences among the parameters may be attributable to the different calculation principles. Correct understanding and evaluation of corneal power parameters can provide a theoretical basis for taking advantage of the total corneal power to improve the accuracy of intraocular lens calculation after keratorefractive surgery.

Photorefractive keratectomy after DMEK for corneal decompensation by phakic IOL.

PURPOSE: To provide the first description of photorefractive keratectomy (PRK) for the correction of mild residual refractive error after Descemet membrane endothelial keratoplasty (DMEK). METHODS: Case report. RESULTS: A 45 year-old woman presenting with phakic intraocular lens (PIOL)-related corneal decompensation underwent staged DMEK surgery following PIOL explantation and cataract surgery. Eighteen months after DMEK, uncorrected distance visual acuity (UDVA) was 20/60 and best-corrected visual acuity (BCVA) was 20/22, with a stable refraction. The patient requested refractive surgery to decrease spectacle dependance, and wavefront-optimized PRK was performed. At last follow-up observation thirty-three months after PRK (54 months after DMEK surgery), UDVA was 20/20, the cornea remained clear without signs of rejection or endothelial failure, and the endothelial cell loss rate was not accelerated after PRK. CONCLUSION: Since long-term visual and refractive stability can be expected after DMEK, PRK may be a particular safe and effective approach for the correction of mild residual refractive errors after DMEK. However, we consider that surgeons must exercise caution when considering keratorefractive surgery in these eyes due to postoperative changes in corneal curvature and thickness, and further studies are encouraged.

Progress of corneal morphological examination combined with biomechanical examination in preoperative screening for keratorefractive surgery.

Although corneal refractive surgery has been proven to be excellent in terms of safety and effectiveness, the reduction of postoperative corneal ectasia remains one of the most concerned topics for surgeons. Forme fruste keratoconus (FFKC) is the most important factor that leads to postoperative corneal ectasia, and common preoperative screenings of the condition include corneal morphology examination and corneal biomechanical examination. However, there are limitations to the single morphological examination or biomechanical examination, and the advantages of the combination of the two have been gradually emerging. The combined examination is more accurate in the diagnosis of FFKC and can provide a basis for determining suspected keratoconus. It allows one to measure the true intraocular pressure (IOP) before and after surgery and is recommended for older patients and those with allergic conjunctivitis. This article aims to discuss the application, advantages, and disadvantages of single examination and combined examination in the preoperative screening of refractive surgery, so as to provide a certain reference value for choosing suitable patients for surgery, improving surgical safety, and reducing the risk of postoperative ectasia.

Exposure of Ophthalmology Residents to Cornea and Keratorefractive Surgeries in the United States.

Purpose To describe the cornea and keratorefractive surgeries experience of U.S. ophthalmology residents. Methods Deidentified case logs of residents graduating in 2018 were collected from ophthalmology residency program directors in the United States. Using Current Procedure Terminology codes, case logs were reviewed in the categories of cornea and keratorefractive surgeries. Accreditation Council for Graduate Medical Education national graduating resident surgical case logs on cornea procedures published from 2010 to 2020 were also analyzed. Results Case logs were received for 152/488 (31.1%) residents from 36/115 (31.3%) ophthalmology residency programs. The most common procedures logged by residents as primary surgeons were pterygium removal (4.3 ± 4.2) and keratorefractive surgeries (3.6 ± 6.2). Residents logged an average of 2.4 keratoplasties as primary surgeon, performing an average of 1.4 penetrating keratoplasties (PKs) and 0.8 endothelial keratoplasties (EKs). As assistants, the most common procedures logged were keratorefractive surgeries (6.1 ± 4.9), EKs (3.8 ± 3.3), and PKs (3.5 ± 2.3). Medium or large residency class size was associated with higher cornea procedural volumes (odds ratio: 8.9; 95% confidence interval: 1.1-75.6; p < 0.05). Conclusion The most common cornea surgeries performed by residents include keratoplasty, keratorefractive, and pterygium procedures. Larger program size was associated with greater relative cornea surgery volume. More specific guidelines for logging of procedures could provide a more accurate assessment of resident exposure to critical techniques such as suturing as well as reflect trends in current practice such as the overall increase in EKs.

Vector analysis of astigmatic correction after single-step transepithelial photorefractive keratectomy and femtosecond-assisted laser in-situ keratomileusis for low to moderate myopic astigmatism.

Purpose: This study aimed to evaluate the outcomes of astigmatic correction by single-step transepithelial photorefractive keratectomy (TransPRK) and femtosecond-assisted laser in-situ keratomileusis (Femto-LASIK) surgeries. Methods: A total of 218 subjects received TransPRK or Femto-LASIK surgery for the treatment of myopia and astigmatism (-2.25 to -0.25 D). Refraction errors and uncorrected (UDVA) and corrected distance visual acuity (CDVA) were examined before and at 3 months after surgery. Astigmatism changes were assessed by vector analysis. Results: Preoperative parameters of the TransPRK group were similar to the Femto-LASIK group. UDVA and CDVA at 3 months were similar between both groups. Manifest refraction (MR) spherical equivalent in the TransPRK group (0 ± 0.20 D) was slightly lower compared with the Femto-LASIK group at 3 months (0.11 ± 0.25 D, P = 0.001). MR cylinder was -0.06 ± 0.19 D in the TransPRK group and -0.02 ± 0.15 D in the Femto-LASIK group at 3 months (P = 0.135). The index of success (IS) was 0.15 ± 0.36 in the TransPRK group and 0.06 ± 0.17 in the Femto-LASIK group (P = 0.125). The correction index (CI) was 1.03 ± 0.19 in the TransPRK group and 1.01 ± 0.11 in the Femto-LASIK group (P = 0.815). Conclusion: For low to moderate myopic astigmatism, TransPRK provided a comparable astigmatic treatment effect as Femto-LASIK. Myopic astigmatism was both slightly overcorrected after TransPRK and Femto-LASIK surgeries.

Impact of Degraded Optics on Monocular and Binocular Vision: Lessons from Recent Advances in Highly-Aberrated Eyes.

PURPOSE: Optical imperfections of the eye, characterized by higher-order wavefront aberrations, are exaggerated in corneal disease (e.g., keratoconus) and iatrogeny (e.g., keratorefractive surgery for myopia correction, keratoplasty for optical clarity restoration). This article reviews the recent advances on this topic for a comprehensive understanding of how optical degradations in disease models impact retinal image quality and monocular and binocular visual performance. METHODS: Published literature over the last decade on retinal image quality and/or monocular and binocular visual functions with corneal irregularity was reviewed based on their relevance to the current topic, study population and strength of study design. The literature was summarized into four themes: 1) wavefront errors and retinal image quality of highly aberrated eyes, 2) monocular and binocular vision loss consequent to degraded optics and visual strategies to optimize performance, 3) impact of optical correction modalities on visual performance and 4) implications for clinical management of patients. RESULTS: Across the 46 articles reviewed, the results clearly indicated that an increase in higher-order aberrations across these conditions had a significant negative impact on the patient's retinal image quality, and monocular and binocular visual functions. Interocular differences in retinal image quality deteriorated visual performance more than an overall worsening of image quality bilaterally. Minimizing optical degradation using rigid contact lenses and adaptive optics technology significantly improves retinal image quality and monocular and binocular vision, but performance remains sub-optimal relative to age-similar healthy controls. CONCLUSION: Corneal disease and iatrogeny are useful models to understand the impact of optical degradation on retinal image quality and visual performance. Clinical management will greatly benefit from equalizing retinal image quality of both eyes of these patients. Future studies that deepen our understanding of the structure-function relation in these conditions are desirable for advancing vision science in this area and for developing novel clinical management strategies.

Duration of contact lens removal before myopic refractive surgery.

PURPOSE: To compare refractive surgery outcomes in patients with different periods without contact lenses prior laser surgery. MATERIALS AND METHODS: Patients included in this study underwent myopic keratorefractive laser surgery between January 2005 and December 2014. Patients were divided into three groups based on the duration of time passed free of soft contact lens wearing prior to final preoperative evaluation and surgery (<24 h, 1-3 days or >3 days). Spectacle wearers served as a control group. Postoperative safety index, efficacy index and % of eyes within 0.5 D of the four groups were compared. A general linear model was used to compare main outcomes while adjusting for age, gender, preoperative measurements, and procedure type (LASIK vs PRK). RESULTS: Overall, 19,747 eyes were included. Soft contact lenses were worn by 42.3% (<24 h: 4.8%, 1-3 days: 18.5% and >3 days: 19.0%) and spectacles by 57.7% prior to surgery. In the PRK group, after adjusting for differences in baseline variables, the <24-h group had a significantly lower efficacy index than all the other groups. There were no significant differences between groups in terms of % eyes within ±0.5 D of intended correction (p = 0.55) or safety index (0.20). In the LASIK group, after adjusting for differences in baseline variables, there were no significant differences between groups in all primary outcomes. CONCLUSION: Soft contact lenses should be removed at least 24 h prior to final preoperative evaluation and refractive surgery, especially for patients undergoing PRK.

Causes for Rejection of Keratorefractive Surgery in a Central Indian Population.

Aim To identify the reasons for refusing refractive surgery in patients visiting for spectacle-free vision. Methodology Medical records of 296 patients who presented for keratorefractive surgery (KRS) from June 2017 to April 2020 at a tertiary eye care center in central India (Government Medical College and Hospital, Nagpur, Maharashtra, India) were reviewed. Demographic details of all the patients and parameters obtained during workup of a case presented for KRSs were captured in an Excel® sheet and analyzed statistically. Results Of the 296 patients who presented for KRS during the study period, 86 (29.1%) patients were denied KRS. The mean pachymetry in the right eye was 505 µm ± 10 µm (range 520-485 µm) and 502 µm ± 7 µm (511-490 µm) in the left eye. Suboptimal corneal thickness (n = 28, 32.6%) was the most common reason for rejection. Other reasons for not recommending the procedure were high myopia (n = 20, 23.3%), spectacle not stable (n = 16, 18.6%), and keratoconus (n = 11, 12.8%). Collagen vascular diseases (n = 3, 3.5%) and anxiety about the procedure (n = 2, 2.3%) were causes unrelated to the procedure. No correlation was observed between corneal thickness and degree of myopia (r = 0.014, p = 0.66). Conclusion Patients presenting for KRS exhibit various problems. Meticulous preoperative evaluation is most important for long-term visual outcome. Suboptimal corneal thickness, high myopia, unstable spectacle correction, and keratoconus were the common reasons for not performing KRS in the study population.

The Role of Corneal Biomechanics in the Assessment of Ectasia Susceptibility Before Laser Vision Correction.

PURPOSE: To describe the tomographic and corneal biomechanical status of a sample of eyes excluded from LVC and to present the differences in biomechanical behavior in relation to cutoffs of clinical- and tomography-based screening methods used in clinical practice. PATIENTS AND METHODS: Observational cross-sectional study including 61 eyes from 32 consecutive patients who were excluded from LVC in our department. Clinical and demographic data were collected from the patients' clinical records. Tomographic data was assessed with a Scheimpflug camera (Pentacam, OCULUS®). Ablation depth (µm) and residual stromal bed (µm) were calculated by the WaveLight® EX500 laser system software (Alcon, EUA). The corneal biomechanical assessment was made through ultra-high speed Scheimpflug imaging during noncontact tonometry (Corvis ST, OCULUS®). Several ectasia risk scores were analyzed. RESULTS: Mean age was 31.0±6 years old and mean manifest spherical equivalent was -2.01 ± 2.3D. Belin-Ambrósio deviation index was the tomographic parameter with higher proportion of eyes within the ectasia high risk interval. In the biomechanical assessment, more than 95% of eyes met the criteria for ectasia susceptibility in four of the first generation and in two of the second generation parameters. In a cutoff based comparative analysis, eyes with Kmax ≥45.5 D, eyes with VCOMA <0 and eyes with ARTmax ≤350 presented significantly softer corneal biomechanical behavior. CONCLUSION: The majority of eyes excluded from LVC in the present study met the criteria for ectasia susceptibility in several biomechanical parameters, validating the clinical and tomographic based screening prior to LVC in our center. Differences found in the biomechanical assessment regarding cutoffs used in clinical practice highlight its differential role in characterizing risk profile of these patients. Tomography should not be overlooked and the integration of all data, including treatment-related parameters, can be the future of risk ectasia screening prior LVC.

Ectasia after keratorefractive surgery: Analysis of risk factors and treatment outcomes in the Indian population.

Purpose: To analyze the risk factors in eyes developing ectasia following keratorefractive procedures. In addition, the study assessed visual outcomes following various treatment modalities for ectasia. Methods: In this retrospective study, data of patients who underwent keratorefractive procedures, presenting to the refractive services of a tertiary eye care hospital in South India between January 2016 and May 2019 was analyzed. Of these, the eyes that developed ectasia were noted and the possible risk factors were determined. Visual outcomes following treatment with corneal collagen crosslinking (CXL) with or without intracorneal ring segment implantation (ICRS) or topography-guided corneal ablation (T-PRK) were analyzed. Results: Forty eyes of 26 patients developed ectasia following keratorefractive procedures, with a mean interval of 73.1± 45.4 months between primary procedure and ectasia development. Of these, 14 patients had bilateral presentation. Identifiable risk factors included ablation depth > 75 µm (59.25%), percentage of tissue altered (PTA) > 40% (48.14%), residual stromal bed < 300 µm (22.22%), mean refractive spherical equivalent > 8 D (25.92%), inferior-superior (I-S) asymmetry > 1.4D (7.40%), central corneal thickness (CCT) < 500 µm (7.40%), Belin Ambrosio Display (BAD) > 2.5 (7.40%), posterior float elevation maximum ≥18 µm (3.70%), and pellucid marginal degeneration (PMD; 3.70%). Conclusion: Our study shows that only 70% of the eyes demonstrated an identifiable risk factor for the development of ectasia. Ablation depth of > 75 µm and the PTA > 40% were the most common risk factors. Treatment following CXL with ICRS or T-PRK demonstrated significantly better visual outcomes in comparison with CXL alone.