Keratometric Parameters Research Articles

Comparison of Ocular Biometry Measurements from Two Swept-Source OCT Devices: Eyestar 900 vs. Anterion.

Advanced swept-source optical coherence tomography (SS-OCT) devices are the current gold standard for the measurement of ocular biometric and keratometric parameters, which are essential for the calculation and selection of intraocular lenses (IOLs). This study compares the agreement of two SS-OCT devices, the Eyestar 900 (Haag-Streit, Köniz, Switzerland) and the Anterion (Heidelberg Engineering, Heidelberg, Germany). All patients undergoing cataract surgery or seeking consultation for corneal abnormalities between January 2024 and May 2024 were eligible for inclusion. Both eyes were included in the final analysis. A sample of 86 eyes from 43 patients was analysed. The mean differences (ES-AN) across all data between the Eyestar 900 (ES) and Anterion (AN) were as follows: anterior chamber depth (ACD) - 0.080 mm (ICC > 0.926), axial length (AL) 0.015 mm (ICC > 0.99), central corneal thickness (CCT) 0.914 µm (ICC > 0.921), corneal curvature along the flat meridian (K1) - 0.024 D (ICC > 0.904), and steep meridian (K2) - 0.210 D (ICC > 0.902), white-to-white corneal diameter (WTW) 0.215 mm (ICC > 0.81). There was excellent agreement for ACD, AL, CCT, K1, K2, and WTW. However, the corneal axis (AX) showed only moderate agreement (ICC > 0.389), with a mean difference of 5.97° and a notable standard deviation of 58.6°. The Eyestar 900 and Anterion demonstrated substantial agreement for all parameters except for the corneal meridian axis. It may be assumed that the inclusion of eyes with irregular corneal topographies may have contributed to this discrepancy. Overall, there was a high level of agreement between the Eyestar 900 and Anterion. It is reasonable to assume that the measurement outcomes provided by both devices are interchangeable for the calculation of target refractive outcomes for intraocular lenses, with no clinically relevant differences.

Repeatability and Agreement of Anterion with Pentacam HR and Orbscan II in Corneal Parameters after Photorefractive Keratectomy

Introduction: This study aimed to evaluate the repeatability and agreement of Anterion with Pentacam HR and Orbscan II in corneal parameters after photorefractive keratectomy (PRK). Methods: This prospective study involved 42 patients (42 eyes) aged between 20 and 40 years undergoing PRK surgery. Corneal measurements were measured two times using Anterion in order to assess the repeatability of this device. Then, the same parameters were measured using Pentacam and Orbscan in order to determine the agreement of Anterion and the other two devices in measuring corneal parameters after PRK. Intraclass correlation coefficient (ICC) checked Anterion’s repeatability. Also, ICC and means of the 95% limits of agreement (LoA) were used to assess the agreement of Anterion results with those of the two other devices. Results: Anterion demonstrated high to moderate repeatability in corneal parameters post-PRK, except for anterior flat keratometry (ICC = 0.73), 4th order root mean square (RMS), and horizontal trefoil (ICC < 0.75). While Anterion and Pentacam showed good agreement in corneal topography and tomography (ICC > 0.90, P < 0.05), they were only interchangeable in keratometric parameters. Additionally, no agreement was observed between Anterion and Pentacam in aberration parameters after PRK. Although Anterion and Orbscan exhibited agreement in anterior average keratometry and central corneal thickness (CCT) (ICC > 0.90, P < 0.05), it was not clinically interchangeable. Conclusion: Anterion demonstrated notable repeatability in most corneal parameters after PRK. Although there was good agreement between Anterion and Pentacam HR in measuring corneal topography and tomography, their interchangeability was limited to other values. Furthermore, Anterion and Orbscan II were not clinically interchangeable.

Интраоперационная профилактика децентрации роговичного кольца в ходе интрастромальной имплантации при центральном кератоконусе

Original article Intraoperative prevention of corneal ring decentration during intrastromal implantation for central keratoconus A.V. Tereshchenko, E.N. Vishnyakova, I.G. Trifanenkova, S.K. Demyanchenko S. Fyodorov Eye Microsurgery Federal State Institution, Kaluga Branch, Kaluga, Russian Federation Medical Institute of Kaluga Tsiolkovski State University, Kaluga, Russian Federation Purpose. To develop a method for intraoperative prevention of decentration of the corneal ring manufactured by NEP Eye Microsurgery LLC during intrastromal implantation for stage 2 central keratoconus. Material and methods. This work included 5 patients (6 eyes) from 32 to 42 year old diagnosed with stage 2 central keratoconus in combination with high myopia, who required implantation of rings manufactured by NEP Eye Microsurgery LLC from 200–250 microns with an internal diameter of 5 mm. The parameters of the intrastromal ring were calculated using the data from nomograms for MyoRing rings and nomograms for calculating intrastromal segments for the spherical component. A femtosecond laser, Femto LDV Z8 (Ziemer, Switzerland) was used to form an intrastromal channel. Capsulorhexis program for centering on the visual axis was used to perform digital marking of the cornea using the Verion system. Results. In 6 months, in all cases there was an increase in visual acuity, a decrease in the spherical and cylindrical components of refraction, a decrease in keratometry data, and the thickness of the cornea remained stable. All patients had a marked decrease in keratometric parameters. Keratotopography results had a specific appearance, corresponding to the central location of the ring. Not a single case of ring displacement or decentration was identified. Conclusion. Developed technique ensures precision implantation of an intrastromal corneal ring with precise centering along the visual axis, reducing risk of decentration of the ring in the postoperative period. Further studies are needed on larger clinical material and over a longer observation period. Key words: primary corneal ectasia, keratoconus, intrastromal keratoplasty, intrastromal corneal ring

Clinical examples of correct orientation of a toric intraocular lens in patients with postkeratotomic corneal ectasia

BACKGROUND: Surgical treatment of cataract in patients with postkeratotomic corneal ectasia has various features. First, difficulties arise when calculating the optical strength of an intraocular lens and its cylindrical component and determining the location of the main axes of astigmatism for toric intraocular lens implantation. Additionally, not all modern keratotopography installations are able to accurately determine the refractive power of the cornea in such patients owing to pronounced irregular astigmatism and a large difference in keratometric parameters in the main meridians. CLINICAL CASES DESCRIPTION: Two clinical cases of surgical treatment of cataract in combination with postkeratotomic keratectasia are presented. Patients underwent a standard preoperative ophthalmological examination. TMS-4 Tomey keratotopograph was used to accurately determine the refractive power of the cornea. The optical power of toric intraocular lens were calculated using the Holladay 2 formula with amendments for radial keratotomy and the Johnson Johnson VISIC online calculator. SN6AT9 intraocular lens (Alcon) and a Tecnis ZCT800 toric intraocular lens (Johnson Johnson) were implanted in patients. The orientation of the position of the cylinder axis of toric intraocular lens was performed perpendicular to the most flattened meridian, corresponding to the position of the keratectasia zone, determined by the most expanded keratotomy scar. Before surgery, the best corrected visual acuity of patient M was OD=0.2, OS=0.4 and that of patient K was OD=0.4, OS=0.2. After surgery, the best corrected visual acuity of patient M was OD=0.8, OS=0.8 and that of patient K was OD=0.8, OS=0.7. CONCLUSION: This study aimed to familiarize practicing ophthalmologists, clinical residents, and postgraduates with a possible treatment option for cataracts by phacoemulsification with implantation of a toric intraocular lens in patients with postkeratotomic keratectasia. The resulting high visual acuity and subjective satisfaction of patients indicate the accuracy of chosen treatment tactics. A reliable visual guide for choosing the cylinder axis is the meridian of the greatest degree of keratectasia (cornea flattening), which is determined by the maximally expanded keratotomy scar position. The intraocular lens cylinder axis is oriented perpendicular to the keratectasia meridian. Ultrasound phacoemulsification of cataract with implantation of a toric intraocular lens is an effective method for correcting induced ametropia after radial keratotomy against the background of postkeratotomy keratectasia with high astigmatism.

Keratometry Changes Between Year One to Seven After Corneal Cross-Linking in Patients With Keratoconus.

We evaluated the timing at and extent to which midterm to long-term keratometric changes can occur in year 1 to 7 after corneal collagen cross-linking (CXL) in patients with keratoconus. We conducted a subgroup analysis of a retrospective cohort study of all consecutive patients who underwent CXL at our cornea center between 2007 and 2011. The inclusion criteria comprised CXL according to the Dresden protocol and a full set of keratometry parameters collected by Scheimpflug tomography preoperatively and at year 1, 3, 5, and 7 after CXL. In addition, best-corrected visual acuity was evaluated. Sixty-three eyes of 47 patients were enrolled. Mean age was 25.46 years ±7.39 years (80.9% male patients). All relevant keratometric parameters showed significant improvement at year 1 after CXL (except for posterior astigmatism). According to mixed-effects model analysis, they all showed further significant change at different points in time between year 1, 3, 5, and 7 (except for K1). In addition, best-corrected visual acuity improved statistically significant between year 1, 3, 5, and 7. Suspected disease progression was noted in 22.2% of patients, mostly between year 1 and 3 after CXL. After initial improvement 1 year after CXL, keratometric and functional parameters were stable until year 5 after CXL in most cases; further improvement can take place even after up to 7 years post-CXL. By contrast, in case of disease progression, changes seem to occur already between year 1 and 3 after CXL.

Effect of refractive surgery on Maklakov tonometry results

The study investigates the influence of changes in keratometric parameters after refractive surgery on the results of Maklakov tonometry. The study examined a total of 61 people (121 eyes). The patients were divided into a control group with no history of surgery (16 people, 31 eyes), a LASIK group (13 people, 26 eyes), a femtosecond-assisted LASIK (FS-LASIK) group (16 people, 32 eyes), and a photorefractive keratectomy (PRK) group (16 people, 32 eyes). The patients underwent standard examination, keratometry (Km), Maklakov tonometry with a 10 g weight, and elastotonometry with 5, 7.5, and 15 g weights. In the LASIK group, the indentation diameter with 5 and 7.5 g weights correlated with Km in the central and near-paracentral zone (r=0.3-0.5). Tonometry with a 10 g weight did not correlate with anything. Tonometry with a 15 g weight inversely correlated with Km in the paracentral points (4 mm) of the strong meridian (r= -0.5 ... -0.7). In the FS-LASIK group, a significant inverse correlation with Km was observed only for the indentation diameter with a 10 g weight in the paracentral (3-4 mm) zone (r= -0.4 ... -0.5). In the PRK group, weak (r<0.4) correlations were found between Km and the indentation diameter of the 7.5 and 10 g weights for the central zone (1-2 mm). No significant correlations were found for 5 and 15 g weights. Tonometry readings with the 10 g weight are the most dependent on Km in different groups, and the readings with the 5 g weight are the least dependent. LASIK is characterized by the largest scatter of dependencies for weights of different masses, FS-LASIK - by the smallest. Tonometry readings with the 5 g weight correlated with Km only in the LASIK group, and this was the only direct correlation. Considering the inverse nature of most correlations, higher Km may be associated with an overestimation of tonometry results, and lower Km - with its underestimation.

Sources of refractive errors in calculating the optical power of intraocular lenses in the treatment of cataract patients

Purpose: Cataract surgery is the most common surgical procedure worldwide, the goal of which is not only to restore the patient’s vision, but to obtain a perfect refractive result that meets the expectations of complete independence from glasses. Unexpected poor refractive outcome after cataract surgery (refractive error) is an unsolved problem, despite increasingly better postoperative outcomes. Improving the postoperative refractive outcome requires an analysis of the sources of refractive errors. This is also the purpose of the present study. Methods: The subject and object of the study were cataract patients with indications for surgical treatment by phacoemulsification (FE) and implantation of an artificial intraocular lens (IOL). The results of the operations of 235 eyes in 160 patients (80 women and 80 men) who underwent surgery in the eye clinic of the Academy of Medical Sciences-Sofia for the period 2018-2020 were analyzed. Results: Of all the measured keratometric parameters, only the value of the cylinder before phacoemulsification is a risk factor, as when it rises above ±1.0D, the risk doubles, and when the value exceeds 2.0D, it becomes 2.4 times greater. The ratio of POC to AL is a statistically significant risk factor for the occurrence of refractive error, with a ratio of POC/AL &lt;0.30, the risk is 2.3 times greater. Conclusion: In the present study, in 62.6% of cases or 2/3 of the eyes, the set Target was successfully met with a minimum permissible refractive error of AE&lt;±0.50D. This determines the effectiveness of the surgical procedure as high.

Transplantation of the Bowman’s layer in cases of biomechanical instability of the cornea after radial keratotomy

Late complications of radial keratotomy (RK), are as a rule caused by a change in the biomechanical properties of the cornea.Purpose: to study the long-term stabilizing effect of the Bowman’s layer (BL) transplantation after RK.Material and methods. In a limited, prospective, monocentric pilot study we operated 2 male patients (2 eyes) aged 60 and 55. The radial incisions had been performed 34 and 38 years ago. The indications for surgery were progressive biomechanical instability of the cornea and functional refractive visual fluctuations. Within 12 months after the operation, complications, corrected visual acuity, keratometric parameters, biomicroscopic transparency of the cornea, and patient satisfaction were assessed.Results. No complications were noted during the follow-up period, the cornea and graft retained transparency. The average thickness of the BS graft was 20±2.1 µm. The average visual acuity corrected by contact lenses increased from 0.4±0.3 to 0.65±0.1, the average indicator of keratometric astigmatism changed from 1.9±1.6 to 3.0 D, these indicators remained after 6, 9 and 12 months, which indicates that biomechanical stability of the cornea was achieved and that the refractive-visual fluctuations are absent.Conclusion. In late term RK complications, BS transplantation partially restores the normal anatomy of the anterior surface of the cornea and ensures its biomechanical stability during a 12-month follow-up period. For the conclusions to be maximally objective, more clinical cases should be studied within a longer observation period.

Rate of fractional change in corneal tomography parameters in keratoconus using a combination of predictive parameters

BackgroundTo compare the rate of fractional change for multiple corneal tomographic factors in progressive keratoconus (KC).MethodsIn this retrospective case series, 40 eyes (40 patients) with progressive KC (increase in central keratometry of 1.00 D or maximum keratometry of 1.50 D on two visits at least six months apart) were included. Cases with previous history of ocular surgery, poor scans, corneal scars, severe dry eyes, post-excimer ectasia, pellucid marginal degeneration were excluded. Medical records, corneal tomography and anterior corneal wavefront (8 mm) (Scheimpflug tomography, Pentacam, Oculus, Germany) were analyzed. Rate of fractional change (Rx = (x1 − x0)/(|x0|tm)); where, x1 = value at follow-up, x0 = value at initial visit and tm = time in months, was measured.ResultsThe mean age of the patients was 30.0 ± 8.4 years. The mean follow-up duration was 8.9 ± 4.2 months. Coma (0.076 ± 1.4) had the largest rate of fractional change (P = 1.7 × 10−14, Kruskal–Wallis test). The rate of fractional change was higher for aberrometric parameters (anterior corneal higher-order aberrations root mean square and anterior coma) compared to pachymetric and keratometric parameters (P values ranging from 1.4 × 10−4 to 7.4 × 10−10, Mann–Whitney test, effect size ranging from 0.4–0.7). The rate of fractional change was comparable between pachymetric and keratometric factors (P > 0.05 for all comparisons, Mann–Whitney test).ConclusionsAnterior corneal wavefront, especially anterior coma, were noted to have higher rate of fractional change compared to single point keratometric and pachymetric indices in progressive KC. This information can be used for decision-making when monitoring patients with KC.

Accelerated corneal cross-linking (18mW/cm2 for 5 min) with HPMC-riboflavin in progressive keratoconus – 5 years follow-up

PurposeTo evaluate long-term results of accelerated corneal cross-linking (ACXL) in patients with progressive keratoconus, seventy-four eyes of 53 patients with progressive keratoconus (documented Kmax progression > 1D/a) who underwent ACXL (18mW/cm2 for 5 min) were included in a retrospective observational clinical study. The investigation focused on tomographic and keratometric parameters, refractive data, and visual outcomes at 5 years follow-ups.MethodsCorrected distance visual acuity (CDVA), slit lamp, and Pentacam® examinations were conducted, including assessments of thinnest corneal point (TP), minimum radius (Rmin), corneal astigmatism, and maximum anterior keratometry (Kmax). These examinations were performed two weeks before the surgery and, on average, 56 months after the surgery. In a subgroup of 24 eyes, Pentacam® examination data from an intermediate visit at 12 months until the final visit was evaluated to confirm continuous stability.The ACXL protocol included corneal abrasion, hydroxypropylmethylcellulose (HPMC)-riboflavin eye drops administered every 5 min for a total duration of 30 min, and irradiation with 18mW/cm2 for 5 min using riboflavin eye drops applied every minute during the irradiation process. Intraoperatively, minimal corneal pachymetry of > 400 µm was ensured in every patient.ResultsAfter 56 months, all values exhibited statistically significant changes (paired t-test; CDVA p = 0.002; Kmax p < 0.001; Rmin p < 0.001; astigmatism p = 0.03; TP p < 0.001).In the subgroup analysis of 24 eyes, which included tomographical and keratometric parameters, no statistically significant changes were observed during the last 12 months of observation (paired t-test; Kmax p = 0.72; Rmin p = 0.67; astigmatism p = 0.72).Treatment failure was strictly defined as an increase in Kmax (> 1D) during the 5-year follow-up and was observed in only 3 eyes (4%).ConclusionsACXL is an effective and safe treatment for patients with progressive keratoconus. Our results demonstrate improvements in functional and tomographical outcomes even after high-energy ACXL (18mW/cm2 for 5 min) over a long-term period of 56 months. Our analysis indicates stable conditions in previously progressive keratoconus, particularly during the final year of the observation period. The treatment failure rate was 4%.

Analysis of the outcomes of three different cross-linking protocols for treatment of paediatric keratoconus: A multicentre randomized controlled trial.

To analyse long-term outcomes of standard cross-linking (SCXL), accelerated cross-linking (ACXL) and transepithelial cross-linking (TCXL) in the treatment of progressive paediatric keratoconus regarding stability, safety and efficacy. This prospective multicentre randomized controlled trial included 97 eyes of 97 paediatric patients with stages I-III ABCD keratoconus grading system, who were randomized into three groups; SCXL group (control group, n = 32; 3 mW/cm2 × 30 min/5.4 J/cm2 ), ACXL (n = 33; 18 mW/cm2 × 5 min/5.4 J/cm2 ) and TCXL (n = 32; 18 mW/cm2 × 5 min/5.4 J/cm2 ). Subjective refraction, uncorrected and corrected visual acuity, keratometry and pachymetry measurements using corneal topography were recorded preoperatively and 1, 2 and 3 years postoperatively. SCXL group exhibited significant successive improvements in the mean visual, refractive and keratometric parameters throughout the entire postoperative 3 years while ACXL group exhibited significant improvements in visual and keratometric parameters in the first postoperative year that remained stable in second and third postoperative years. TCXL group exhibited significant progressive deterioration in all mean parameters compared to SCXL and ACXL (p < 0.0001). Both SCXL and ACXL revealed final 100% success rate with good stability while TCXL revealed final 22% failure rate with keratoconus progression (p < 0.0001). SCXL and ACXL were comparable in halting keratoconus progression and achieved good stability and safety; however, SCXL was more efficient than ACXL as it yielded greater significant postoperative mean visual, refractive and keratometric improvements achieving smoother corneal remodelling. Both SCXL and ACXL were much superior to TCXL. SCXL is the best CXL treatment option for paediatric keratoconus while ACXL is a good and effective alternative.

Progressive Flattening after Corneal Collagen Crosslinking: A 10-Year Follow-Up

Purpose: This study aimed to demonstrate the importance of long-term follow-up after corneal collagen crosslinking. Methods: This case report showed an intense progressive flattening of keratometric parameters in a patient without risk factors such as high maximum keratometry, thin cornea, uncontrolled ocular allergy, collagen, or rheumatologic diseases. Even with significant haze formation and progressive flattening, the patient exhibited progression after a long follow-up period. Results: The patient presented with grade 2 haze associated with progressive flattening of approximately 10 D in keratometric parameters (Kmax, K1, K2, and Kmean) during the first 5 years after surgery. Corneal opacity altered the minimum pachymetry reading on Pentacam to 265 microns. Anterior corneal follow-up optical coherence tomography revealed a thickness of 453 microns. The patient developed low visual acuity while wearing glasses. The scleral lens was fitted, allowing a visual acuity of 20/30, with satisfactory visual quality. Keratometric stability was observed between the fifth and tenth year. In the tenth year, the patient maintained haze, but there was a progression of 1.7 D in the Pentacam comparative map. Conclusions: Long-term monitoring after corneal crosslinking should be performed. Eyes with haze and intense progressive flattening may fail after a long period.

Интраокулярная коррекция пресбиопии после лазерной кераторефракционной хирургии

Purpose. To present the results of research on modern aspects of intraocular correction of presbyopia after laser keratorefractive surgery. Material and methods. A literature search was performed to identify studies on databases eLibrary, PubMed and Scopus, using the keywords «calculation of multifocal lenses», «multifocal IOLs after refractive surgery», «correction of presbyopia after refractive surgery» (in the eLibrary database), «multifocal IOL» and «multifocal lenses calculation» (in the PubMed and Scopus databases). Thirty related articles were identified. In addition, seven clinical studies in which different groups of patients with a history of refractive surgery underwent correction of presbyopia with multifocal intraocular lenses (IOL) were identified. Results. In this article, there are examples of recent research of information about the intricacies of calculating refractive power of multifocal lenses after refractive surgery. Every year the number of people with a history of laser vision correction is growing, which means that for surgeons arises question about correct calculation of keratometric parameters. To date, the calculation of the value of the optical power of an implantable multifocal IOL after laser refractive surgery is complex and individual for each patient. Most people in this category are still not ready to wear glasses. Recent studies confirm the success of calculating implantable multifocal IOL, and ways to minimize inaccuracies in hitting the refraction of the target lie both in the approach to calculating the optical power of an implanted multifocal lens, and in choosing the optimal method for assessing artificially modified cornea keratometry. Conclusion. The results of clinical studies presented in the review allow us to conclude that the results of calculating the optical power of implanted multifocal IOLs are quite successful and, in turn, clinical and functional results in patients with a history of laser refractive surgery. However, further research is required. Key words: presbyopia correction, multifocal IOL, IOL calculation formulas, laser correction, LASIK, FemtoLASIK, SMILE.

Corneal cross-linking in patients with keratoconus: up to 13years of follow-up.

To evaluate long-term safety and efficacy of corneal collagen cross-linking (CXL) in patients with keratoconus up to 13years. In this mono-centre exploratory study, we included all consecutive patients who underwent CXL in our cornea centre from 01/01/2007 to 12/30/2011 and met the inclusion criteria. CXL was performed in all patients according to the Dresden protocol. Evaluation included best-corrected visual acuity (BCVA), topographic keratometry by Scheimpflug corneal tomography and endothelial cell count (ECC). Follow-up measurements were taken up to 13years after treatment were compared with baseline values. The study enrolled 168 eyes. The mean age of our patients was 26.3years ± 7.8years. A complete topographic dataset was available 1year postoperatively for 142 eyes, 5years postoperatively for 105 eyes, 10years postoperatively for 61 eyes and 13years postoperatively for 9 eyes. BCVA increased statistically significant after 1year, 5years and 10years and non-significantly after 13years. All keratometric parameters with exception of posterior astigmatism showed a statistically significant decrease after 1year, 5years and 10years. After 13years, the decrease was statistically significant only in Kmax, K2 and thinnest cornea. No significant changes in ECC were detected. Three eyes received Re-CXL, none of the eyes received penetrating keratoplasty and no infections occurred in this cohort. CXL can slow down or even stop the progression of keratoconus in the majority of cases. The effect is long-lasting with excellent safety.

Динамика кератотопографических и биомеханических параметров роговицы после проведения акселерированного ультрафиолетового кросслинкинга с использованием защитного лоскута донорской роговицы в лечении прогрессирующего кератоконуса при «тонкой роговице»

Purpose. To analyze changes in the biomechanical and topographic parameters of the patient's cornea using the Corvis st (OCULUS, Germany) and Pentacam (OCULUS, Germany) device before and after accelerated ultraviolet crosslinking of the cornea using a donor cornea protective flap in the treatment of progressive keratoconus with "thin cornea" and compare the obtained data with the results after classical accelerated crosslinking. Material and methods. According to the proposed technology, 26 patients (26 eyes) were operated on with a diagnosis of progressive keratoconus 2nd stage with corneal pachymetry less than 400 µm, mean value 390 ± 40 µm. Comparison group – patients diagnosed with progressive keratoconus 2nd stage with corneal pachymetry over 400 µm, mean value 450 ± 40 µm, comparable in age and gender, being operated on using the technology of classical accelerated crosslinking. In addition to standard research methods, before and after surgery, patients underwent an assessment of the biomechanical and topographic parameters of the patient's cornea using the Corvis st (OCULUS, Germany) and Pentacam (OCULUS, Germany) devices. Results. The results obtained in both groups were comparable in all parameters: there was a decrease in keratometric parameters in the first months after the operation, with their further stabilization during the entire period of observation. The pachymetry value remained stable, no significant changes in UCVA and Correctable Visual Acuity were detected. Evaluation of specific keratotopographic indices (ISV, IVA, KI, CKI, IHD) showed their decrease both in the main and control groups, and Rmin tended to increase. The value of the inscribed radius tended to decrease, which indicates an increase in the stiffness of the cornea after classical accelerated crosslinking and crosslinking of the proposed technology. Conclusion. Application of the technology of accelerated ultraviolet crosslinking using a protective flap of the donor cornea in the treatment of progressive keratoconus with "thin cornea" leads to an increase in the rigidity of the cornea and stabilization of the ectatic process of the cornea in the postoperative period, just as with the classical technology of accelerated crosslinking. Keywords: progressive keratoconus, "thin cornea", accelerated ultraviolet crosslinking using a donor cornea protective flap, keratopotographic parameters of the cornea, biomechanical parameters of the cornea.

Objective study of accommodation in keratoconus

Background. Keratoconus (KC) is the most commonly diagnosed corneal ectasia among young adults today. The asymmetric process of progression of the KС determines the occurrence of anisometropia, which in a compartment with increased audience and the absence of proper optical correction leads to a violation of the accommodation function that has not previously studied with this pathology.Purpose: to study the work of accommodation using an objective method of computer accommodation in young people with newly diagnosed keratoconus (КC).Material and methods. Thirty (60 eyes) people were included in the study, of which 15 people (30 eyes) formed the main group and 15 (30 eyes) formed the control group. The main group consisted of patients with newly diagnosed bilateral KC: 15 eyes – stage 1, 13 eyes – stage 2, 2 eyes – stage 3 of the disease). Patients of the control group had a history of mild myopic astigmatism of the direct type. The average age of the patients was 23.5 ± 3.1 years. All patients underwent standard ophthalmological examination: autorefkeratometry, visometry and biomicroscopy. In addition, the main keratometric parameters of the cornea were examined using the Scheimpflug analyzer Pentacam. An objective assessment of the indicators of the accommodative ability of the eye was carried out using computer accommodation on the Righton Speedy-I device. The statistical processing was carried out in the IBM SPSS Statistics 23 program.Results. The results of the analysis of accommodograms in both groups demonstrate the predominance of disorders of the ciliary muscle, which manifested themselves in the form of habitual-excessive accommodation tension (HEAT) and accommodative asthenopia of a spasmodic nature. In the control group, in 76% of cases, there was a pattern of excessive accommodative response by the type of HEAT. The state of accommodation in the group with KC in 68% of cases was characterized by an excessive and unbalanced accommodative response, with an unstable course of the curve. The average indicator and the curve of the accommodogram significantly exceeded the indicators of the control group, which proves an unstable state of accommodation in KC. In comparison with the control group, a decrease in coefficient of growth of the accommodogram (CR) by 37% (p &lt; 0.05) was recorded, confirming the absence of a smooth and increasing course of the accommodative response following the stimulus. Analysis of high-frequency the coefficient of microfluctuation (CMF) demonstrated a 10% increase in the work of the ciliary muscle (p &lt; 0.001). The correlative dependence of these parameters with visometry and autorefractometry data has been established.Conclusion. The objective method of accommodation assessment revealed abnormalities of ciliary muscle functioning in patients with a first-time diagnosis of KC, which correspond to the phenomena of spasmodic accommodative asthenopia. The established correlation between CR and CMF with the data of visometry and autorefractometry suggests a potential improvement of accommodation functioning under conditions of optical correction with contact lenses.

Transepithelial Corneal Cross-linking with Supplemental Oxygen in Keratoconus Treatment - Corneal Stromal Demarcation Line and Safety

Purpose: To evaluate the corneal stromal demarcation line and safety of transepithelial corneal cross-linking (CXL) with supplemental oxygen in progressive keratoconus treatment. Methods: This is a retrospective review of 25 patients with progressive keratoconus who underwent epithelial-on CXL with supplemental oxygen from December 2019 to February 2022. Outcomes measured include corneal stromal demarcation line depth, volume of cornea treated, endothelial cell count, best-corrected visual acuity, keratometric parameters and post-treatment adverse events. Results: 25 eyes of 25 patients were included and mean age was 28.3 years. Mean follow-up period was 11.5 ± 1.39 months. Pre-operatively, mean ± standard deviation (SD) of K1, K2, Kmax and minimal corneal thickness were 45.9D ± 3.79D, 50.2D ± 4.83D, 57.5D ± 6.98D and 482.3um ± 36.8um respectively. There is no significant difference between pre and post-treatment corneal topographic parameters. There was improvement in BCVA post-treatment. The mean post-treatment corneal stromal demarcation line depth was 367.3 ± 89.8um. The volume of treated cornea including the central corneal epithelial thickness was 73.3 ± 4.39%. There was no reduction in endothelial cell count (ECC) post-procedure (pre-treatment mean ECC±SD: 2695.4 ± 224.5 cells/mm2, post-treatment ECC 2730.1 ± 252.0 cells/mm2, p-value = 0.33). Post-treatment corneal haze was mild and seen in 8 patients postoperatively. One patient developed a non-visual axis involving stromal infiltrate that resolved with topical broad-spectrum anti-microbials. Conclusion: Trans-epithelial CXL with supplemental oxygen for keratoconus treatment achieved comparable corneal stromal demarcation line depth comparable to that of conventional epithelial-off corneal cross-linking and had a similar safety profile.

A novel analysis of Scheimpflug total corneal refractive power following corneal cross-linking in mild to moderate keratoconus.

To detect an earlier improvement in mild to moderate keratoconus following corneal cross-linking (CXL) with total corneal refractive power (TCRP) using ray tracing method. A total of 40 eyes of 30 consecutive patients who underwent CXL for progressive keratoconus were retrospectively enrolled. The following keratometric parameters provided by Pentacam HR, including maximum keratometry (Kmax), steepest keratometry (Ksteep), 3 mm zonal TCRP centered over corneal apex (TCRPapex,zone 3 mm), zonal mean keratometry and TCRP centered over corneal cone (Kmcone,zone and TCRPcone,zone 1, 2, 3 mm) were evaluated preoperatively and 1, 3, 6, and 12mo postoperatively. Groups 1 and 2 were defined based on Kmax at postoperative 1mo as improved (the initial improvement group) or worsen (the initial deterioration group) compared to the preoperative level. In the overall group, only keratometric parameters based on ray tracing method displayed significant improvement early at 3mo postoperatively, in which TCRPcone,zone 1 mm and 2 mm exhibited the largest flattening (0.57 D and 0.53 D, respectively). In Group 1, only Kmax, Kmcone,zone 2 mm and TCRPcone,zone 2 mm showed significant improvement initially at 1mo postoperatively, in which Kmax exhibited the largest improvement (1.05 D), followed by TCRPcone,zone 2 mm (0.82 D). In Group 2, only keratometric parameters based on ray tracing method and Kmcone,zone 3 mm showed slight but not significant improvement early at 3mo, in which TCRPcone,zone 3 mm displayed the most improvement (0.19 D), followed by TCRPcone,zone 2 mm (0.15 D). The findings indicate that a 2 mm zonal TCRP centered over Kmax could earlier detect keratometric improvement by CXL compared to other commonly used parameters in mild to moderate keratoconic eyes.

Errors in IOL Power Calculation in Rare Clinical Cases. Literature Review

The postoperative result is determined not only by technique of a surgeon, the availability of modern innovative equipment, but also due to the accurate diagnostics and skilled interpretation of biometric, keratometric parameters; the use of modern formulas of IV, V generations to calculate the optical power of the intraocular lens (IOL), allowing to predict the correct position of the IOL, through the use of predictive variables that determine the postoperative lens position. The variety of modern research methods and continuous improvement of formulas for lens calculation allows us to get the closest results to emmetropia.

The Impact of Learning Curve on Flap Thickness Outcome in Femtosecond Laser-assisted Laser In Situ Keratomileusis Performed with New LenSx Dual Platform.

PurposeTo evaluate the effect of learning curve on flap thickness (FT) outcome in femtosecond (FS) laser-assisted laser in situ keratomileusis (LASIK) operation for myopia performed with recently introduced LenSx dual platform using curved applanation cone.MethodsSeventy eyes of 36 patients with myopia or myopic astigmatism operated with FS laser-assisted LASIK with recently introduced LenSx dual platform were evaluated in this retrospective study. Operations were divided into two groups: first 20 operations (20 eyes of 10 patients) and next 50 operations (50 eyes of 26 patients). Data on patient demographics, preoperative and postoperative keratometric and aberrometric parameters, and FT related outcome, including mean central FT, mean total FT, intra-FT range, and FT homogeneity were compared in study groups.ResultsExcept for significantly lower preoperative steepest keratometry values in the next 50 operations versus first 20 operations (p = 0.033), no significant difference was noted between study groups in terms of preoperative and postoperative parameters. When compared to first 20 operations, next 50 operations were associated with significantly higher values for mean central FT (median, 123 μm vs. 114 μm; p = 0.007) and mean total FT (median, 123 μm vs. 113 μm; p = 0.015), whereas significantly lower intra-FT range (median, 4.0 μm vs. 4.5 μm; p = 0.003).ConclusionsIn conclusion, our findings related to FS laser-assisted LASIK surgery for myopia with new LenSx dual platform using curved applanation cone revealed significant impact of learning curve on the corneal FT outcome in terms of closer FT to the intended value and lower intra-flap range.