Keratorefractive Surgery Research Articles

Intraocular aphakia correction in patients with prior keratorefractive surgery: literature review. Part 1

Introduction. An increasing number of patients with a history of keratorefractive surgeries are presenting to ophthalmologists with complaints of vision loss due to cataracts. Treating this group poses surgeons with a range of unique challenges: high demands for vision quality, complexities in selecting the appropriate intraocular lens (IOL) power calculation formula and IOL model, target refraction, as well as the need to modify cataract extraction techniques and address specific postoperative considerations. Despite advancements in the development of new IOL designs and calculation formulas, clinical and functional outcomes in this group remain inferior to those in patients without prior keratorefractive procedures. A paradigm shift is emerging, advocating for a personalized approach in the diagnosis and management of cataracts in these patients. However, discussing all aspects within a single review proved impractical, leading us to divide it into two parts. The objective of the first part of this study is to assess the specific considerations for aphakia correction in patients who have undergone keratorefractive procedures, based on literature data, while taking into account the long-term complications of refractive surgery. Additionally, this part will address the fundamental principles of the design and functionality of pseudoaccommodating intraocular lenses (IOLs). Materials and methods. A selection of over 200 peer-reviewed publications from resources such as PubMed, eLibrary, CyberLeninka, Science Direct, and Google Scholar over the past 30 years was conducted. The first part of the review includes 49 publications. This work represents an analysis of contemporary literature, reflecting the impact of keratorefractive surgeries on the successful performance of phacoemulsification with IOL implantation. Results. The findings from the first part of the analysis indicate that a detailed medical history of previously performed keratorefractive corrections – specifically their type and potential long-term complications – play a significant role in determining the surgical treatment strategy. Standard examination methods do not always fully reflect the optical characteristics of the cornea in these patients. Extended preoperative assessments, including specialized techniques such as keratotopography and keratotomography, are crucial for identifying corneal irregularities and for the subsequent selection of the type of intraocular lens (IOL) for aphakia correction in patients who have undergone keratorefractive surgeries. Studies show high effectiveness not only in using monofocal lenses but also in the potential application of pseudoaccommodating IOLs, including those with extended depth of focus and multifocal lenses. The selection of optimal formulas for IOL calculation, as well as the clinical aspects influencing refraction in the postoperative period, will be addressed in the second part of the literature review. Conclusion. The increase in the number of refractive surgeries has led to a growing population of patients with cataracts following ametropia correction. This has spurred the development of new IOL variants with extended depth of focus. However, literature data on their effectiveness in patients who have undergone keratorefractive procedures remain limited. Multicenter prospective studies are needed to evaluate new IOL models and to determine the optimal surgical strategies for this category of patients.

The outcomes of first-generation (visumax 500) and second-generation (Visumax 800) keratorefractive lenticule extraction surgeries for astigmatism

To evaluate the efficiency, predictability, and residual astigmatism between first- and second-generation keratorefractive lenticule extraction (KLEx) surgeries in a prominent astigmatism population. A retrospective cohort study was conducted, and individuals who underwent first- and second-generation KLEx surgeries were enrolled. A total of 31 and 35 eyes were categorized into first and second KLEx groups, respectively. Visual acuity, refraction, topographic parameters, and surgical indices were recorded. Independent t tests were used to compare the postoperative uncorrected distance visual acuity (UDVA), spherical equivalent (SE), and residual astigmatism between the two groups. The difference in UDVA was not significant three months after KLEx surgery (P = 0.509), and the SEs three months after surgery also presented similar values between the two groups (P = 0.552). The first KLEx group demonstrated greater residual astigmatism than did the second KLEx group throughout the three-month follow-up period (all P < 0.05). The values of surgically induced astigmatism (SIA), difference vector (DV), magnitude of error (ME) and correction index (CoI) were significantly better in the second KLEx group via vector analysis (all P < 0.05). Old age, high steep keratometry (K), high topographic cylinder, large angle kappa, and a small optic zone were correlated with greater residual astigmatism in the first KLEx group (all P < 0.05), whereas only a small optic zone was significantly correlated with greater residual astigmatism in the second KLEx group (P = 0.047). The second-generation KLEx is correlated with a lower risk of residual astigmatism.

Reply to Letter Regarding: Tomographic Predictors of Ectasia Development After Keratorefractive Surgery.

Reply to Letter Regarding: Tomographic Predictors of Ectasia Development After Keratorefractive Surgery.

Biomechanical changes of the cornea after orbital decompression in thyroid-associated orbitopathy measured by corvis ST

This study aims to investigate the changes in ocular biomechanical factors in patients with inactive thyroid eye disease (TED) who undergo orbital decompression surgery. This observational prospective study include 46 eyes of 31 patients with inactive TED undergoing orbital decompression at a tertiary university hospital from October 2021 to September 2023. All participants underwent a full ophthalmic examination, and a biomechanical examination was performed using corvis ST at baseline, 1 month, and 3 months postoperatively. The study participants had a mean age of 45 ± 11.6 years, and 58.1% of them were female. The second applanation time (A2T) increased from baseline to postoperative month 1 and continued to increase to postoperative month 3 (P < 0.001). The first applanation velocity (A1V), highest concavity (HC) peak distance, and pachymetry parameters also increased from postoperative month 1 to postoperative month 3 (P = 0.035, P = 0.005, and P = 0.031, respectively). The HC time increased from baseline to postoperative month 3 (P = 0.027). Other changes were statistically insignificant. The P-values were adjusted according to biomechanically corrected intraocular pressure (bIOP). Baseline Hertel significantly influenced A2 time (P < 0.001). Our findings suggest that ocular biomechanical parameters may change following decompression surgery in patients with inactive TED. Specifically, an increase in A2T, A1V, and HC peak distance suggests a decrease in corneal stiffness, although the increased HC time contradicts this. It is recommended to postpone keratorefractive or intraocular lens implantation surgeries until corneal biomechanics stabilize after decompression surgery for optimal results.

Epithelial Remodeling and Epithelial Wavefront Aberrometry after Spherical vs. Cylindrical Myopic Small Incision Lenticule Extraction (SMILE).

Background/Objectives: To compare the epithelial thickness changes and the changes in epithelial wavefront aberrometry following spherical versus astigmatic myopic small incision lenticule extraction (SMILE). Methods: Eighty-six eyes of 86 patients who underwent SMILE were included in this retrospective study. A total of 43 eyes underwent myopic spherical correction (spherical group) and 43 eyes underwent myopic cylindrical correction (cylindrical group). The groups were matched according to the spherical equivalent of surgically corrected refraction. Subjective manifest refraction as well as high-resolution anterior segment optical coherence tomography (MS-39; CSO; Florence, Italy) were obtained preoperatively as well as 3 months postoperatively. The latter was utilized for computing epithelial wavefront aberrometry in addition to epithelial thickness mapping. Results: Epithelial thickness increased significantly in both groups after SMILE (p < 0.01). In the cylindrical group, epithelial thickening was more pronounced on the flat meridian compared to the steep meridian (p = 0.04). In both groups, epithelial wavefront aberrometry showed a significant postoperative increase in the epithelium's spherical refractive power, causing a myopization of -0.24 ± 0.42 diopters (D) in the spherical group (p < 0.01) and -0.41 ± 0.52 D in the cylindrical group (p < 0.0001). While no significant changes in epithelial cylindrical refractive power were observed in the spherical group, a significant increase was noted in the cylindrical group from -0.21 ± 0.24 D to -0.37 ± 0.31 D (p = 0.01). In both groups, epithelial higher-order aberrations increased significantly (p < 0.001). Conclusions: Postoperative epithelial remodeling after SMILE alters lower-order (sphere and cylinder) and higher-order aberrations of the corneal epithelial wavefront and might contribute to refractive undercorrection, especially in astigmatic corrections. Epithelial wavefront aberrometry can be used to quantify the refractive effect of epithelial remodeling processes after keratorefractive surgery.

Tomographic Predictors of Ectasia Development After Keratorefractive Surgery.

Tomographic Predictors of Ectasia Development After Keratorefractive Surgery.

Изучение вязкоэластичных свойств роговицы у пациентов с субклиническим кератоконусом

Abstrakt Corneal viscoelastic properties in patients with subclinical keratoconus I.V. Dutchin, E.L. Sorokin, Yu.V. Kutuzova, Ia.E. Pashentsev Fyodorov Eye Microsurgery Federal State Institution, Khabarovsk Branch, Khabarovsk, Russian Federation Far-Eastern State Medical University, Khabarovsk, Russian Federation Purpose. To evaluate corneal viscoelastic properties in subclinical keratoconus (SKC), analysis of its association with corneal thickness, and degree of risk of iatrogenic corneal ectasia. Material and methods. The main group consisted of 21 patients with signs SKC according to Pentacam (Oculus, Germany). The control group consisted of 21 patients without signs of subclinical SKC. In both groups, moderate myopia prevailed; groups were comparable in age and gender. A comparative statistical analysis of parameters of topography system Pentacam and corneal viscoelastic properties using the Corvis ST (Oculus, Germany) was carried out. Results. In the main group, the values: Corneal Applanation Velocity1, the Deformation Amplitude, and the Tomographic and Biomechanical Index (TBI) were statistically significantly higher compared to the control group. The values of the radius and the corneal central thickness, on the contrary, had statistically significantly lower values than in the control group. According to the values of the TBI (from 0 to 0.28), in the control group there was a «no obvious risk» of postoperative ectasia. In the main group, the average value of the TBI (0.43) was much higher than in the control group, which indicates weakened protective frames of cornea and risk of iatrogenic corneal ectasia in case of refractive surgery. There was no relationship between corneal thickness and TBI in the main group: r= –0.34 (p=0.13). Despite the signs of SKC in the main group, according to Pentacam, in 74% of eyes the corneal viscoelastic properties had sufficient rigidity for keratorefractive surgery. Conclusion. When selecting patients for keratorefractive surgery, along with assessing the parameters of corneal topography, it is also necessary to evaluate the corneal viscoelastic properties. Key words: subclinical keratoconus; fruste keratoconus; corneal viscoelastic properties, corneal biomechanical properties; iatrogenic corneal ectasia

Progressive Paracentral Visual Field Loss at Low Intraocular Pressures Following LASIK.

Intraocular pressure is currently the only known reliable, modifiable risk factor for the development and progression of glaucoma. Other risk factors for glaucoma include increasing age, myopia, decreased central corneal thickness, and low corneal hysteresis (CH) measurements. Photoablative keratorefractive surgery including laser assisted in situ keratomileusis (LASIK) has become a common way to treat refractive error, with over 25 million procedures performed in the United States alone. Though myopic LASIK has been associated with a decrease in CH measurements, relatively little is known about the risk of LASIK on glaucoma onset and progression. Here we present an observational study of 4 consecutive relatively young and otherwise healthy glaucoma patients with a history of myopic LASIK who showed progression of paracentral visual field deficits at intraocular pressures of 12mmHg or less while being carefully monitored. Therefore, these patients required lower targets of intraocular pressure, in the single-digit range, to slow or halt progression. In this cohort, the average corneal hysteresis was more than 2 standard deviations below normal values. This series suggests that additional study into the association of LASIK and glaucoma is warranted, including the potential risk contribution of diminished CH. These studies may be particularly relevant as patients who underwent LASIK procedures in the early 2000s may now be at increased risk of glaucoma due to the risk factor of age.

Postoperative Astigmatism after Keratoplasty: A Systematic Review Meta-Analysis Based on PRISMA.

Background: The number of corneal transplants is rising, with the aim to treat a spectrum of diseases ranging from dystrophies to corneal opacities caused by trauma or chemical burns. Refractive outcomes after this procedure are often impossible to predict and associated with high levels of astigmatism. However, there are many techniques that affect the reduction of astigmatism and improve the quality of life of patients. Objectives: The aim was to compare the improvement in postoperative visual acuity (logMAR) and amount of corneal astigmatism (Diopters) after corneal keratoplasty in patients who additionally underwent a surgical procedure, which affects the reduction in postoperative astigmatism, and to determine the most effective method. Search Methods and Selection Criteria: A thorough search was carried out across online electronic databases including PubMed, Embrase, Ovid MEDLINE, Scopus, and Web of Science, using combinations containing the following phrases: postoperative astigmatism, post-keratoplasty astigmatism, anterior lamellar keratoplasty (ALK), deep anterior lamellar keratoplasty (DALK), posterior lamellar keratoplasty, endothelial keratoplasty (EK), penetrating keratoplasty (PK), corneal transplant, keratoplasty, refractive surgery, kerato-refractive surgery, laser in situ keratomileusis (LASIK), and femtosecond LASIK. This was to determine all English-language publications that discuss refractive operations for postoperative or post-keratoplasty astigmatism. These bibliographies were searched for English-language publications published between 2010 and 2023. We proceeded to review each detected record's reference list. Data Extraction: Study characteristics such as study design, sample size, participant information, operations performed, and clinical outcomes were all extracted. Data Statistical Analyses: The Comprehensive Meta-Analysis software (version 3.3.070, 2014) was used to perform the analysis. The threshold of 0.05 for p-values was considered statistically significant. All effect sizes are reported as standardized differences (Std diff) in means with a 95% confidence interval (CI) and visualized graphically as forest plots. Publication bias is presented as a funnel plot of standard error by Std diff in means. Four methods were used to evaluate the heterogeneity among the studies: Q-value, I2, chi-square (χ2), and tau-squared. Main Results: We included 21 studies that randomized 1539 eyes that underwent corneal transplantation surgery either by PKP, DALK, or DSEAK techniques. The results showed the most significant improvement in the visual acuity and significant decrease in the corneal astigmatism after laser surgery procedures, like femtosecond-assisted keratotomy after DALK and PKP and LASIK after DSEAK.

Femtosecond laser-assisted in situ keratomileusis versus small-incision lenticule extraction: current approach based on evidence.

Laser keratorefractive surgery achieves excellent visual outcomes for refractive error correction. With femtosecond laser, small incision lenticule extraction (SMILE) is an increasingly viable alternative to laser-assisted in situ keratomileusis (LASIK). Comparative studies demonstrate similar efficacy and predictability between SMILE and LASIK, making it difficult for clinicians to choose which to use. This review thus compares femtosecond-LASIK (FS-LASK) and SMILE in various scenarios, to assist clinicians in deciding which refractive surgery procedure to recommend. SMILE may be superior for highly myopic eyes due to a smaller decrease in functional optical zone. SMILE further induces less spherical aberration and less overall higher order aberrations in mesopic conditions. SMIILE also has less postoperative dry eye, making it suitable those with preexisting dry eye. For low to moderate myopic astigmatism correction, FS-LASIK has less undercorrection compared to SMILE. Lastly, SMILE has not yet received Food and Drug Administration or Conformité Européenne approval for hyperopic correction, rendering FS-LASIK the choice of procedure for hyperopic correction. Both FS-LASIK and SMILE demonstrate good efficacy and predictability. Understanding specific clinical scenarios where one may be superior to the other will aid clinicians in choosing the most suitable procedure for personalized care.

Современные технологии рефракционной экстракции лентикулы

Purpose. To present modern literature data on the main aspects of refractive lenticular extraction technology. Material and methods. To perform the review, the search for literature sources on PubMed abstract databases was analyzed using the keywords “keratorefractive surgery”, “corneal lenticular”, “femtosecond laser” and data from Russian publications on the topic of the article for the period up to and including 2023. Results. According to the literature data, the strengths and weaknesses of the implementation of each of the existing technologies of keratorefractive surgery have been studied, and the postulates of choosing the optimal method for correcting ametropia have been formulated individually for each patient. Conclusion. Today, keratorefractive surgery is a high-tech industry in ophthalmology and provides a predictable, high-precision and stable refractive result in patients with a wide range of refractive disorders. The analysis of accumulated scientific and clinical experience has shown that one of the most pathogenetically oriented technologies in keratorefractive surgery, minimally affecting the reduction of the biomechanical properties of the cornea, not inducing dry eye syndrome, providing a highly predictable postoperative result in the correction of myopia and myopic astigmatism is refractive lenticular extraction, opening a new era in laser vision correction. Keywords: ametropy, keratorefractive surgery, refractive lenticular extraction

Clinical Evaluation of Corneal Endothelial Parameters following Laser Refractive Surgery in Myopic Eyes: A Review.

Background: The aim of this review was to investigate the influence of various laser refractive surgery methods on the corneal endothelium in myopic patients. The role of the corneal endothelium in laser refractive surgery (LRS) is currently being addressed in the assessment of postoperative corneal edema risk. Methods: Changes in corneal endothelial cell density and morphology after LRS were evaluated based on a systematic review of current studies. The results of a literature search in the PubMed, Science Direct, Google Scholar, and the Web of Science databases, as well as a manual search, were selected for the final review according to the PRISMA 2020 flow diagram. Results: We included 24 prospective clinical trials in the review: surface ablation (twelve), LASIK and FemtoLASIK (two), femtosecond lenticule extraction (two), and comparable studies (eight). Endothelial cell density was determined by specular or in vivo confocal microscopy. In most studies, no statistically significant differences were found between preoperative and postoperative endothelial parameters. In nine studies, the changes were statistically significant, but no vision-threatening complications occurred, and no serious corneal complications developed in any eyes during the follow-up period. Conclusions: Based on collected data, laser keratorefractive surgery appears not to exert a significant effect on the corneal endothelium.

Safety and efficacy of implantable phakic contact lens versus implantable collamer lens in myopia correction.

Phakic intraocular lenses (pIOLs) have proven to be excellent substitutes for excimer laser keratorefractive surgery in certain situations. We aimed to assess the efficacy and safety of two pIOLs, the implantable collamer lens (ICL V4c) versus the implantable phakic contact lens (IPCL V2), for myopic correction. In this prospective randomized clinical trial, we allocated eligible eyes with myopia > - 6 diopters into IPCL or ICL implantation groups, each including 100 eyes of 100 individuals. Preoperative and postoperative assessments at 3, 6, and 12 months included measurements of the spherical equivalent (SE), uncorrected distance visual acuity (UCDVA), best-corrected distance visual acuity (BCDVA), intraocular pressure (IOP), maximum keratometry (K1), minimum keratometry (K2), mean keratometry (Kmean), anterior chamber depth (ACD), anterior chamber angle (ACA), and endothelial cell density (ECD). The groups had comparable demographic characteristics and baseline visual and anatomical values (all P > 0.05). The UCDVA, BCDVA, and SE of the two groups were comparable at baseline and at all postoperative follow-up examinations (all P > 0.05). Both groups experienced significant improvements in UCDVA, BCDVA, and SE at three months postoperatively (all P = 0.001), and measurements remained stable for up to 12 months. Keratometry readings were comparable between the groups over the follow-up period and remained unchanged at all visits (all P > 0.05). The ACA in the ICL group was significantly decreased at three months postoperatively (P = 0.001) and then widened significantly at 6 and 12 months (both P = 0.001). In the IPCL group, the postoperative ACA was significantly decreased at three months (P = 0.001) and was comparable to that in the ICL group (P > 0.01). However, at the 6- and 12-month postoperative visits, the ACA was significantly narrower in the IPCL group than in the ICL group (both P = 0.001). The ACD in both groups was decreased at three months postoperatively (both P = 0.001) and remained stable until the end of the study. The ECD remained comparable between the groups at all postoperative visits (all P > 0.05). We did not observe a significant ECD reduction in either group at any postoperative follow-up visit (all P > 0.05). We encountered no serious complications in either group. ICL and IPCL had comparable safety and efficacy outcomes in terms of anterior chamber morphometrics, visual and refractive results, and corneal parameters. Further multicenter randomized clinical trials with longer follow-up periods, larger sample sizes, and measurement of additional anterior chamber and corneal morphometrics, vault, and other vision parameters are needed to verify these findings.

Tomographic Predictors of Ectasia Development After Keratorefractive Surgery.

The aim of this study was to identify the risk factors for postkeratorefractive surgery ectasia in unsuspicious tomographies and to report a new index coined diameter of peak locations (DPLs). All patients who underwent keratorefractive surgery between 2011 and 2018 at Care-Vision Laser Centers, Israel, and later developed ectasia were included. For each ectasia case, 3 matched controls were selected. Demographic and preoperative, intraoperative, and postoperative data were collected. Multivariate analysis was performed to evaluate the interdependence of the variables. The retrospective study included 19 ectasia and 58 control eyes. There were no significant differences between the groups in ablation depth ( P = 0.73), preoperative spherical equivalent ( P = 0.12), percent tissue altered ( P = 0.71), residual stromal bed ( P = 0.73), and Ectasia Risk Score System ( P = 0.60). The anterior and the posterior symmetry index were significantly higher ( P < 0.001), and DPL was significantly tighter in the ectasia group ( P = 0.01). Binary multiple logistic regression found the symmetry index of the posterior cornea and DPL to be better predictors than age, percent tissue altered, Ectasia Risk Score System, residual stromal bed, and ablation depth. A higher posterior symmetry index and a tighter DPL are predictors of ectasia in patients with otherwise normal tomographies. A tight DPL implies a weak area in the cornea, which is thin and slightly bulging, increasing the risk of this area becoming ectatic.

Complex therapy of the evaporative form of dry eye syndrome in patients after keratorefractive surgery

Introduction. Meibomian gland dysfunction (MGD) is considered as the leading cause of the evaporative dry eye syndrome (DES). At the same time the standard methods of DES treatment often allow to achieve only a short-term effect and the search of alternative methods to achieve remission for a longer period is required.Aim. To evaluate the effectiveness of a combined treatment of DES with MGD using transdermal Intense Pulsed Light (IPL) method combined with preservative-free sodium hyaluronate 0.18% eyedrops.Materials and methods. The study involved 60 patients (120 eyes) after refractive surgery (femtoLASIK) with DES and MGD aged 20 to 40 years with a follow-up period of 3 months. The patients were divided into two groups: main (30 patients) and control (30 patients). Patients of both groups were administered a preservative-free form of 0.18% sodium hyaluronate four times a day for 3 months. All studied patients underwent standard examination methods, indicators of DES were assessed along with an objective valuation of tear film parameters and the meibomian glands condition by mean of digital biomicroscopy using a MediWorks slit lamp before surgery and 7 days, 1, 2 and 3 months after refractive surgery.Results and discussion. A comparative analysis of therapy effectiveness in the main and control groups showed that OSDI scores (ocular surface disease index), non-invasive tear breakup time (NITBUT) and meibomian gland function improved after treatment in both groups, but in the main group (IPL) positive dynamics of indicators were more pronounced with a cumulative increase of effectiveness after subsequent sessions.Conclusion. A course of IPL therapy in combination with a course of sodium hyaluronate 0.18% for dry eye syndrome due to MGD reduces the time, allows for longer-term results of therapy and promotes earlier elimination of discomfort.

Keratoconus: exploring fundamentals and future perspectives - a comprehensive systematic review.

New developments in artificial intelligence, particularly with promising results in early detection and management of keratoconus, have favorably altered the natural history of the disease over the last few decades. Features of artificial intelligence in different machine such as anterior segment optical coherence tomography, and femtosecond laser technique have improved safety, precision, effectiveness, and predictability of treatment modalities of keratoconus (from contact lenses to keratoplasty techniques). These options ingrained in artificial intelligence are already underway and allow ophthalmologist to approach disease in the most non-invasive way. This study comprehensively describes all of the treatment modalities of keratoconus considering machine learning strategies. A multidimensional comprehensive systematic narrative review. A comprehensive search was done in the five main electronic databases (PubMed, Scopus, Web of Science, Embase, and Cochrane), without language and time or type of study restrictions. Afterward, eligible articles were selected by screening the titles and abstracts based on main mesh keywords. For potentially eligible articles, the full text was also reviewed. Artificial intelligence demonstrates promise in keratoconus diagnosis and clinical management, spanning early detection (especially in subclinical cases), preoperative screening, postoperative ectasia prediction after keratorefractive surgery, and guiding surgical decisions. The majority of studies employed a solitary machine learning algorithm, whereas minor studies assessed multiple algorithms that evaluated the association of various keratoconus staging and management strategies. Last but not least, AI has proven effective in guiding the implantation of intracorneal ring segments in keratoconus corneas and predicting surgical outcomes. The efficient and widespread clinical translation of machine learning models in keratoconus management is a crucial goal of potential future approaches to better visual performance in keratoconus patients. The article has been registered through PROSPERO, an international database of prospectively registered systematic reviews, with the ID: CRD42022319338.

Sterile donor tomography for improvement of refractive results after keratoplasty

Purpose: Any corneal microsurgeon may have inadvertently transplanted a donor corneal tissue with (subclinical) keratoconus or prior keratorefractive surgery, which typically leads to postoperative refractive surprises and cannot always be detected in the eye bank with only slit lamp. Given the increased number of keratorefractive procedures performed in the last decades, eye banks will soon have to face this problem more intensively. Thus, the efficiency and reliability of anterior segment optical coherence tomography (AS‐OCT) as a non‐invasive and sterile screening method in the eye bank to detect corneal grafts with curvature and/or thickness abnormalities was assessed.Methods: 1315 donor corneal tissues mounted in sterile tissue cultivation flasks were imaged using an AS‐OCT. The corneal tissues were preserved in organ culture medium I and transferred into organ culture medium II (containing dextran T‐500 6%) for deswelling at least 24 h prior to measurement and keratoplasty. Depth raster scans were performed through the posterior surface of the corneal tissues within a 7 mm central zone to create 3D volume data. The volume data set was preprocessed to eliminate flask reflections artefacts and to define the region of interest (ROI). Subsequently, the adaptation of a sphero‐cylindrical surface model was carried out with raytracing. Thus, the radii of curvature for the front and back surfaces can be determined and a corneal thickness map is generated.Results: The mean steep/flat front surface radius was 7.46 ± 0.29 (5.07–9.29)/7.69 ± 0.24 (6.70–9.50) mm, the corresponding values for the back surface being 6.47 ± 0.32 (5.00–8.00)/6.80 ± 0.31 (5.81–8.00) mm and the mean central thickness was 610 ± 84 (379–1457) μm. Abnormalities (beyond ±2 or ± 3 SD) were found in 140 or 34 corneas (10.6% or 2.6%) for anterior surface curvature, 120 or 38 corneas (9.1% or 2.9%) for the posterior surface, and 55 or 16 corneas (4.2% or 1.2%) for thickness.Conclusions: The AS‐OCT provides an objective, sterile and semi‐automated screening method to identify corneal morphological and refractive alterations (e.g. keratoconus, status post PRK/LASIK) and further optimize corneal donor selection in the eye bank. Corneal donors with curvature or thickness abnormalities ±3 SD do not have to be discarded but can be used for posterior lamellar keratoplasty or tectonic keratoplasty.

Clinical History Method versus Corneal Tomographers in Estimating Corneal Power after.

To investigate the concordance between the corneal power determined by various approaches with two tomographers (MS-39® and Galilei G6®) and the clinical history method (CHM) in patients undergoing photorefractive surgery with excimer laser for myopic errors. Prospective cohort study. Patients undergoing keratorefractive surgery, and having pre- and postoperative keratometries, and tomographies, were included. In 90 eyes, the differences in the power estimated by the CHM and the one determined by four approaches with the corneal tomographers, which included measurements of the posterior cornea, did not show statistically significant differences in their averages. However, the 95% limits of agreement were very wide. After obtaining regression formulas to adjust the values of these four variables, the results of the agreement analysis were similar. Although certain values either directly determined or derived from measurements with the Galilei® and MS-39®corneal tomographers, approximated the estimated value of postoperative corneal power according to the CHM, due to the amplitude of their limits of agreement, these calculations must be taken with care, because they may not be accurate in a given eye.

A Case of Bilateral Implantation of Diffraction IOL with Extended Depth of Focus in a Patient with a History of Keratorefractive Excimer Laser Surgery

A clinical case of bilateral implantation of EDOF IOL in a patient after LASIK is presented. The standards for assessing visual acuity at an intermediate distance are indicated. A modified version of the test table for the intermediate distance is presented. The obtained functional result corresponds to theoretical ideas about the potential of IOL with a prolonged focus. When calculating the IOL after LASIK, a sufficient degree of accuracy was provided by the formulas Haigis-L, Barrett True-K. The use of data on the total refractive power of the cornea is promising.

Dry Eye Syndrome in Refractive Patients. Literature Review

Dry eye syndrome is a multifactorial disease of the ocular surface, which is based on the development of hyperosmolarity, inflammation and sensorineural disorders in the imbalance of the structural components of the tear film. The main complaints of refractive patients after keratorefractive surgery are a feeling of dryness in the eyes, a foreign body, redness, blurring of the image, which is due to the clinical manifestations of post-refractive dry eye syndrome. There are factors that contribute to the development of postrefractive dry eye syndrome, such as: neurotrophic epitheliopathy, postoperative inflammation, damage to goblet cells, toxic corneal epitheliopathy caused by preservatives contained in eye drops, leading to inadequate restoration of the tear film. In clinical practice, to assess the stability of the tear film, a method is used to determine the tear film rupture time using invasive and non-invasive methods. Invasive methods include: staining of the ocular surface with a solution of fluorescein during the Norn test. To date, laboratory diagnostics expands the understanding of the pathogenesis, etiology and mechanisms underlying the xerosis of the ocular surface at the molecular level, and also facilitates the diagnosis and prognosis of dry eye syndrome. Laboratory methods of the ocular surface include the study of biomarkers of lacrimal fluid, conducting impression cytology with an assessment of the condition of goblet cells. In this regard, it is necessary to have a deep understanding of the main etiopathogenetic links of dry eye syndrome, a wide range of diagnostics of the condition of the ocular surface before and after the surgical stage of patient management, which will determine the success of keratorefractive surgery and a stable course of the postoperative period.