Stages Of Keratoconus Research Articles

Performance of Corvis ST Parameters Including Updated Stress-Strain Index in Differentiating Between Normal, Forme-Fruste, Subclinical, and Clinical Keratoconic Eyes

PurposeThis study seeks to evaluate the ability of the updated stress strain index (SSIv2) and other Corvis ST biomechanical parameters in distinguishing between keratoconus with different disease stages, and normal eyes. DesignDiagnostic accuracy analysis to distinguish disease stages. Methods1084 eyes were included and divided into groups of normal (199 eyes), forme fruste keratoconus (FFKC, 194 eyes), subclinical keratoconus (SKC, 113 eyes), mild clinical keratoconus (CKC-I, 175 eyes), moderate clinical keratoconus (CKC-II, 204 eyes) and severe clinical keratoconus (CKC-III, 199 eyes). Each eye was subjected to a Corvis ST examination to determine the central corneal thickness (CCT), biomechanically corrected intraocular pressure (bIOP), SSIv2 and other eight Corvis parameters including the SSIv1, SP-A1, A1T, ARTh, IIR, DAM, DARatio2 and CBI. The sensitivity and specificity of these parameters in diagnosing keratoconus were analyzed through receiver operating characteristic curves. ResultsBefore and after correction for CCT and bIOP, SSIv2 and ARTh were significantly higher, and IIR and CBI were significantly lower in the normal group than in the FFKC group, SKC group and the 3 CKC groups (all P<0.05). There were also significant correlations between the values of SSIv2, ARTh, IIR, CBI and the CKC severity (all P<0.05). AUC of SSIv2 was significantly higher than all other Corvis parameters in distinguishing normal eyes from FFKC, followed by IIR, ARTh and CBI. ConclusionCorvis ST's updated SSI demonstrated superior performance in differentiating between normal and keratoconic corneas, and between corneas with different keratoconus stages. Similar, but less pronounced, performance was demonstrated by the IIR, ARTh and CBI.

Dramatic Reduction in Corneal Transplants for Keratoconus 15 Years After the Introduction of Corneal Collagen Crosslinking.

The aim of this study was to investigate the effect of the implementation of corneal collagen crosslinking (CXL) on the frequency of corneal transplants among patients with keratoconus (KC) in the same region. Before the introduction of CXL in 2007, 55 primary corneal transplants had been conducted in patients with KC (2005 and 2006) at the Department of Ophthalmology, Oslo University Hospital, Norway. We collected data from our corneal transplant registry for 2021 and 2022. The primary outcome was the number of corneal transplants performed in patients with KC. Age, sex, visual acuity (logarithm of the minimal angle of resolution), KC stage according to the Amsler-Krumeich classification system, and steepest keratometry reading (maximum keratometry, Pentacam, HR) were recorded. Furthermore, we registered the annual number of CXL treatments conducted from 2007 to 2022. A total of 352 corneal transplants were performed in 2021 and 2022. Among them, 11 (3.1%) were transplants for patients with KC. All included patients were male; further, 90.1% and 9.1% of the patients were graded stages 4 and 3, respectively. The mean maximum keratometry was 79.0 diopter (range 61.0-109). The mean best-corrected visual acuity (logarithm of the minimal angle of resolution) was 1.3 (range 0.2-3.0). In 2021 to 2022, 431 CXL treatments were performed. There was a significant decrease in the number of corneal transplants performed in patients with KC 15 years after the introduction of CXL. This indicates that the availability of CXL treatment over many years may considerably reduce the need for keratoplasties in this group of patients.

Results of Accelerated Local Cross-Linking in Keratoconus

Objective of the study. To analyze the effectiveness of accelerated local corneal cross linking in the treatment of keratoconus (KC). Patients and methods. Thirty-four patients (42 eyes) were included in the study: 19 people (24 eyes) with stage II keratoconus, 15 people (18 eyes) with stage III Amsler keratoconus. All patients were examined using the following methods: visometry, refractokeratometry, keratotopography, optical coherence tomography of anterior segment, endothelial cell density calculation before and after surgical treatment in 6 months, 1, 2 and 3 years. Results. Significant increase of uncorrected (UDVA) and corrected (CDVA) distance visual acuity was registered 6 months after operation in KC of the II and III stages. In KC stage II, the NCOZ and EOC were greater, from 0.39 ± 0.14 to 0.61 ± 0.18 by 0.22 ± 0.04 (p &lt; 0.05) and from 0.60 ± 0.15 to 0.77 ± 0.12 by 0.17 ± 0.03 (p &lt; 0.05), respectively, in stage III. — from 0.12 ± 0.03 to 0.23 ± 0.07 by 0.12 ± 0.04 (p &lt; 0.05) and from 0.45 ± 0.10 to 0.53 ± 0.12 by 0.10 ± 0.02 (p &lt; 0.05), due to decreased refractive indices in the central 3.0 mm zone. Refractive indexes of the central corneal zone, UVA and CVA in all patients after one, two and three years, as well as data of minimal corneal thickness and endothelial cell density did not change statistically significantly during the entire observation period.

Биомеханические свойства роговицы в норме и при прогрессирующем кератоконусе

A prospective study of corneal stiffness parameter of 173 eyes of 173 healthy subjects with different refractions as well as 41 eyes with keratoconus was carried out. The study groups were comparable in age and gender composition. Correlation was performed between corneal stiffness parameter (Stiffness Parameter (SP-A1), minimum corneal thickness (MCT) and biomechanically compensated intraocular pressure (bIOP) determined using Pentacam HR and Corvis ST (OCULUS, Germany), as well as the anteroposterior chamber (APC) value and patient age. Based on multivariate regression analysis, the correlation between corneal stiffness index SPA1, minimum corneal thickness (MCT) and biomechanically compensated IOP (bIOP) in healthy subjects (p = 0.00001, p = 0.005, respectively) as well as in patients with keratoconus (p = 0.00000, p = 0.0032, respectively) was established. Using the obtained data, the tables for determination of corneal stiffness in healthy subjects and patients with different stages of keratoconus, depending on the minimal thickness and level of biomechanically compensated intraocular pressure, were compiled. Application of the tables will allow in practical work to quickly analyze corneal stiffness index which can be used as an important diagnostic criterion in patients with keratectasia. Keywords: corneal stiffness index, biomechanically compensated intraocular pressure, correlation dependence.

Сравнительная оценка эффективности хирургического лечения кератоконуса комбинированным методом

Relevance. Keratoconus is a common asymmetric and usually bilateral ectatic corneal disease characterized by progressive corneal protrusion, resulting in reduced visual acuity and deterioration of optical properties. Purpose of the study. To evaluate the effectiveness of surgical treatment of keratoconus with various combined methods. Material and methods. The article presents a comparative analysis of data from patients with II and III stages of keratoconus (52 patients, 66 eyes) after implantation of intrastromal corneal ring segments with femtosecond accompaniment, followed by corneal crosslinking and corneal crosslinking, followed by implantation of intrastromal corneal ring segments with femtosecond accompaniment. Results and conclusion. The refractive result for the spherical and cylindrical components gave the best result in group 2, in which stage 1 was implantation of ICRS, and stage 2 was corneal collagen crosslinking, compared with group 1, in which stage 1 was corneal collagen crosslinking, and stage 2 was implanted ICRS. Progression stopped in 65 cases. Keywords: keratoconus, intrastromal corneal segments, femtosecond laser, corneal crosslinking.

Results of intrastromal corneal ring implantation in advanced keratoconus With the aim of postpoing or avoiding corneal transplantation.

To evaluate the safety and efficacy of the surgery of intracorneal ring segment implantation with 320° of arc (320-ICRS) in patients with advanced keratoconus stage IV and maximum keratometry (Kmax) above 60 D. A prospective, interventional case series study evaluating 25 eyes of 19 patients with keratoconus stage IV and Kmax > 60D in which 320-ICRS were implanted using VisuMax® femtosecond. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), keratometric values (mean - mean-K, flat - K1, and steep - K2), maximum keratometry (Kmax), tomographic astigmatism, refractive astigmatism and asphericity (Q) were assessed preoperatively and at 3, 6 and 12 months after the procedure. The UDVA improved from 1.03 ± 0.28 LogMAR (20/200) to 0.54 ± 0.21 LogMAR (20/60), (p < 0.001), the CDVA (with glasses) improved from 0.63 ± 0.29 LogMAR (20/80) to 0.31 ± 0.16 LogMAR (20/40),(p = 0.004), K1 reduced from 54.41 ± 4.46 D to 49.36 ± 4.11 D (p < 0.001), K2 reduced from 61.15 ± 4.37 D to 53.715 ± 4.05 D, (p < 0.001), mean-K reduced from 57.55 ± 4,17 D to 51.44 ± 3,94 D (p < 0.001), Kmax reduced from 69.80 ± 8.20 D to 63.43 ± 6.31 D (p < 0.001) and asphericity (Q) changed from -1.57 ± 0.35 to -0.77 ± 0.56 (p < 0.001). A total of 89.9% patients reached BCVA wearing scleral contact lens 0.2 LogMAR(20/25). 320-ICRS to treat advanced keratoconus appears to be an efficacious and safe procedure, being a surgical alternative to delay or even prevent corneal transplantation.

Contributed Session II: Detecting subclinical keratoconus by mapping corneal biomechanics using wave-based optical coherence elastography.

The detection of subclinical keratoconus in human corneas remains a challenging task. It is hypothesized that the focal reduction in biomechanical properties of the cornea would be the primary initiating event of keratoconus before changes in topography and pachymetry are manifested. We propose to use an air-couple ultrasonic optical coherence elastography system to map the elasticity of the corneas of 15 patients with a clinical diagnosis of keratoconus (KC) in one eye, and subclinical keratoconus (SK) in the fellow eye. The fully non-contact system excites the corneal apex to produce Lamb wave propagation and measures wave speed and average corneal thickness along 16 semi-meridians. Measurements in 30 human healthy subjects (control group: CG, N = 60 corneas) defined a baseline of normal biomechanics in two biomarkers: Spatial Anisotropy of Wave Speed (SAWS < 0.207), and the Speed-Thickness Index (STI > 0). SAWS was significantly higher in KC (0.353, p < 0.001) and SK (0.249, p < 0.001) corneas when compared to the CG. Moreover, STI maps show abnormal elasticity in SK (STI = -1.22) and KC (STI = -0.375) compared to the CG. Our results show important biomechanical differences in SAWS and STI between normal, subclinical, and advanced stages of keratoconus, suggesting those as potential biomarkers to identify "at-risk" corneas before changes in topography and pachymetry become evident.

Prevalence and clinical profile of keratoconus in patients presenting at a provincial hospital in KwaZulu, Natal, South Africa: A case study.

Keratoconus (KC) is a progressive, asymmetrical corneal disease, characterized by stromal thinning that leads to distortion, causing vision loss. The visual loss is secondary to corneal scarring, irregular astigmatism, and myopia. The prevalence of KC has been reported to differ in different parts of the world. The study aimed to determine the prevalence and profile of patients with KC presenting to a provincial hospital in KwaZulu-Natal, South Africa. A retrospective study design was used to review 412 clinical records of patients attending the McCord Provincial Eye Hospital (MPEH) during a five-year period (2016-2020). Data on age, race, refraction, clinical profile, treatment plan, and diagnosis were ascertained. The prevalence of KC in MPEH was found to be 13.7% with a mean age of 24.7±7.94 years. Black African and females had a higher frequency of KC compared to males and other ethnic groups. Most of the patients presented with a severe stage of KC and referral was the most common management. Central corneal thinning and Munson's sign were the most prevalent clinical signs. There was no statistically significant difference between the worse and better eye when comparing the clinical signs. The prevalence and clinical profile of patients with KC in this study was similar to that reported by previous studies and more in Blacks and females. Population based epidemiological studies are needed to determine the prevalence of KC in South Africa to enable early clinical interventions.

Effect of Keratoconus Stage and Classification Parameters on Deep Anterior Lamellar Keratoplasty Outcomes.

The aim of this study was to investigate the effect of the keratoconus (KC) stage according to the Amsler-Krumeich classification system and the parameters used in this classification on deep anterior lamellar keratoplasty outcomes. The preoperative KC stage was determined, and the presence of corneal scarring was noted. The preoperative and postoperative best-corrected visual acuity (BCVA), refractive error, mean central keratometry (K mean ) readings, topographic astigmatism, and minimum corneal thickness (CT) values were recorded. Intraoperative and postoperative complications were also noted. One hundred thirty-seven eyes (54 eyes in stage 3-83 eyes in stage 4) were included in the study. The mean follow-up period was 42.20 ± 24.36 months. There was no statistically significant difference between stage 3 and 4 KC groups for postoperative BCVA, K mean , CT, spherical equivalent, and topographic astigmatism values (each P value >0.05). The effect of preoperative BCVA, K mean , CT, and refractive error values on postoperative BCVA could not be demonstrated ( P = 0.264). In addition, no statistically significant correlation was found between postoperative and preoperative values (each P value > 0.05). Although intraoperative Descemet membrane perforation and postoperative early suture loosening were observed more frequently in stage 4 KC than in stage 3 KC, the 2 groups were statistically similar for these and other complications (each P value >0.05). The preoperative KC stage and the parameters used in classification are not useful in predicting postoperative deep anterior lamellar keratoplasty outcomes. The timing of the surgery should be planned with the awareness that the progression of the disease will not have a negative effect on outcomes.

Baseline Characteristics of 1976 Patients With Ectatic Corneal Disorders at a Single Center From 2010 to 2021: A Cross-Sectional Study of the Homburg Keratoconus Center.

The study objective was to analyze the baseline characteristics of keratoconus (KC) patients at the Homburg Keratoconus Center from 2010 to 2021. This cross-sectional study included 3,674 eyes, with analysis of demographics, clinical findings, visual function, endothelial measurements, and topographic, tomographic, and corneal biomechanical data from the first visit. Mean patient age was 36.3±13.8 years. The mean uncorrected distance visual acuity in log of minimal angle of resolution was 0.60 (20/80, Snellen equivalent), and the corrected mean was 0.3 (20/40). Of 1976 patients, 48.9% reported eye rubbing. Mean values (ranges) were 49.4±6.3 (36.3-78.0) D for steep keratometry, 462.4±66.0 (48.0-659.0) μm for thinnest corneal thickness, 9.7±8.7 (-0.5 to 88.8) for Belin/Ambrósio enhanced ectasia total deviation, 0.8±0.4 (0.0-1.0) for the Corvis biomechanical index, 0.9±0.2 (0.0-1.0) for the tomographic biomechanical index, 0.1±0.5 (-0.9 to 2.0) for the KC match index, 8.3±1.8 (2.2-17.7) mm Hg for corneal hysteresis, 7.1±2.2 (0.0-17.0) mm Hg for corneal resistance factor, and 2,562.9±326.3 (1,011-3,937) cells/mm2 for endothelial cell density. The average ABCDE KC stage was A2B3C1D1E2. Distance-corrected visual acuity correlated strongly with topometric, tomographic, and biomechanical data ( P <0.001). This comprehensive description of baseline features of KC patients at a tertiary center provides a reference for further longitudinal and international multicentric studies.

Analysis of Corneal Biomechanical Properties in Different Keratotopographic Patterns of Keratoconus.

To analyze the frequency of main keratotopographic patterns at the 1st, 2nd, and 3rd stages of keratoconus and investigate corneal biomechanical properties across different patterns. The study comprised two stages. The first stage was computational-experimental, where we utilized COMSOL Multiphysics® software (COMSOL AB, Stockholm, Sweden) to mathematically model corneal mechanical behavior under intraocular pressure and pulsed air jet action in both normal and keratoconic conditions. The second stage was the clinical phase, during which we retrospectively analyzed the examination results of both healthy subjects and patients with keratoconus. In total, the study included 256 eyes (256 subjects). Among them, 174 eyes (174 healthy individuals) had normal corneas with different refractions, and 82 eyes (82 individuals) had stages 1, 2, and 3 of keratoconus based on Amsler-Krumeich classification. The keratotopographic characteristics of the participants were assessed using Sirius (Schwind, Germany) and Pentacam AXL (OCULUS Optikgeräte GmbH, Germany) keratotomographs, while the corneal biomechanical properties were studied using noncontact tonometry with the Corvis ST device (OCULUS Optikgeräte GmbH, Germany). The study focused on evaluating corneal stiffness index values in the central optical zone under various keratotopographic patterns. In addition, it compared the elastic coefficient values c1, c2, and c3 for the model of hyperelastic behavior of corneal material outside the keratoconus zone. Furthermore, the study examined the values of reduced stiffness zone characteristics, including the stiffness reduction factor ψmax, effective radius Rk, and the ratio of maximum and minimum strain intensity in keratoconus of different stages. The mean age of the patients in the study was 30.16 ± 8.31 years, with 166 men and 90 women participating. The study revealed typical keratotopographic patterns in the examined keratoconus stages, as well as their occurrence frequency. In the 1st stage of keratoconus, the pattern of asymmetric astigmatism was noted more frequently (in 75% of cases). In the 2nd stage, the pattern with an ectasia zone in the lower cornea was observed in 80% of cases, and in the 3rd stage, a centrally located keratotopographic ectasia pattern was found in 42% of cases. Comparative analysis showed that the greatest decrease in stiffness parameter (SpA1) and stress-strain index occurred in the central pattern (by 64% and 46%, respectively), while the least decrease was observed in local corneal radius reduction in the lower cornea (by 42% and 33%, respectively). The decrease in strength properties in keratoconus occurs in a local area, the size and degree of which are determined by the disease stage. The indicated biomechanical parameters are consistent regardless of the shape and localization of keratotopographic patterns but are relevant to diagnostic specifications using the Corvis ST pneumotonometer, which assesses corneal properties in the apical zone.

Клинико-функциональные результаты модифицированной фемтолазерной рефракционной аутокератопластики у пациентов с кератоконусом

Purpose. To analyze the clinical and functional results of modified femtolaser refractive autokeratoplasty and evaluate its effectiveness in patients with keratoconus during a follow-up period of 36 months. Material and methods. The study included 24 patients (13 men and 11 women) diagnosed with stage 2 keratoconus according to the Amsler, 1998 classification. The age of the patients ranged from 25 to 37 years (mean 31±6 years). Taking into account the initial parameters of the spherical and cylindrical components, as well as biometric parameters, which indicated the deliberate ineffectiveness of intrastromal keratoplasty (ISKP) in this group, all patients were performed femtolaser refractive autokeratoplasty (FRAK) according to a modified technique using a Femto LDV Z8 femtolaser unit (Ziemer, Switzerland). Results. An analysis of the clinical and functional results of the modified FRAK technique for topographically centrally located keratoconus showed that this technology provides a stable refractive effect in patients with stage 2 keratoconus during a follow-up period of 36 months. Performing personalized FRAK according to indications provides an increase in corrected visual acuity already in the early postoperative period with a tendency to further increase an average up to 0,46±0,08 by 36 months after surgery, as well as stable state of the ecstatic process throughout the entire follow-up. Conclusion. The modified FRAK technology is effective and can be successfully used in the early stages of keratoconus in cases with initial low visual acuity and axial myopia. Key words: keratoconus, femtolaser refractive autokeratoplasty

The Biomechanical E-Staging: In Vivo Biomechanics in Keratoconus.

Belin's ABCD keratoconus classification system allows keratoconus staging based on the criteria of anterior (A) and posterior (B) corneal curvature, thinnest corneal thickness (C), and best spectacle-corrected visual acuity (D). These parameters also provide a progression assessment, but do not take corneal biomechanics into account. The analysis of corneal biomechanics by the Corvis ST (Oculus, Wetzlar, Germany) allows for separation of healthy and keratoconus corneas, based on the Corvis Biomechanical Index (CBI) and the Tomographic Biomechanical Index (TBI). As Corvis ST measurements are highly reliable and are independent of keratoconus severity, a biomechanical parameter was developed for keratoconus corneas based on the linear term of the CBI. This provides biomechanical keratoconus staging. The Corvis Biomechanical Factor (CBiF) is the basis for the introduction of the biomechanical E-staging, which augments the ABCD classification to the ABCDE classification, thus including the cornerstone of corneal biomechanics. This article highlights strengths and limitations of the ABCDE classification. "Unilateral keratoconus" supposedly turns out to be mostly a snapshot of a highly asymmetric keratectasia. Regular astigmatism is sometimes an important differential diagnosis to keratectasia and may be difficult to differentiate from it. Furthermore, the use of the biomechanical E-staging in daily practice for progression assessment of keratoconus and after its treatment by corneal cross-linking or implantation of intracorneal ring segments will be demonstrated and discussed.

Comparison of Hybrid Contact Lenses and Rigid Gas-Permeable Contact Lenses in Moderate and Advanced Keratoconus.

We aimed to compare the clinical results and topographic data of the new generation hybrid contact lens (HCL) and rigid gas-permeable contact lens (RGPCL) in patients with moderate and advanced keratoconus. In this prospective study, HCL users comprised group 1 and RGPCL users comprised group 2. Snellen uncorrected visual acuity (UCVA), best corrected visual acuity (BCVA), and lens-corrected visual acuity (LCVA); manifest spherical-cylindrical values; corneal topography measurements (flat keratometry [K1], vertical keratometry [K2], mean K, maximum K [Kmax], central corneal thickness [CCT], and thinnest corneal thickness [TCT]); and cone location were recorded. The study included 83 eyes of 51 patients in group 1 and 61 eyes of 40 patients in group 2. The groups were similar in age and gender (p>0.05). Mean LCVA (logMAR) was significantly lower than BCVA in both groups (p<0.001). The mean visual gain with contact lenses (Snellen chart) was 3.4±1.8 lines in group 1 and 4.0±2.1 lines in group 2. There was no significant difference between the two groups in BCVA, LCVA, or lines gained (p>0.05). There was also no significant difference between the two groups in terms of keratoconus stages, mean Kmax, CCT, TCT, or cone location (p>0.05), while mean UCVA (logMAR) and mean K were higher in group 2 (p<0.05). In both groups, the visual gain with lenses was higher in eyes with central cones, and there was significantly greater visual increase in group 2 (p=0.039). In moderate and advanced keratoconus, HCLs improved vision as much as RGPCLs and both lenses were more effective for central cones. Nevertheless, longer term of follow-up and larger numbers of patients are needed for long term follow-up results of HCL.

Эффективность имплантации интрастромальных роговичных сегментов при кератоконусе с иррегулярным ассиметричным парацентральным астигматизмом

Purpose. To evaluate the efficacy and safety of implantation of intrastromal corneal ring segments ICRS (IRS NEP MNTC) in patients with keratoconus with irregular asymmetric paracentral astigmatism. Material and methods. 14 patients (16 eyes) with keratoconus stage II–III with irregular asymmetric paracentral astigmatism were evaluated before and after ICRS (IRS NEP MNTC). The tunnels for ICRS implantation were created with a femtosecond laser. ICRSThe effectiveness was assessed on the basis of an increase in uncorrected and corrected visual acuity in the postoperative period, as well as the absence of keratectasia progression in the period from 10 to 18 months after ICRS implantation. Results. All ICRS were implanted in 16 eyes without intra and postoperative complications. Uncorrected distance visual acuity (UDVA) increased from 0.16 ± 0.12 preoperatively to 0.54 ± 0.24 at the 6th month of postoperative follow-up. Corrected distance visual acuity (CDVA) increased from 0.38 ± 0.2 to 0.72 ± 0.34 at the 6th month of postoperative follow-up. The refractive index decreased from preoperative mean –3.56 ± 2.4 D to –2.02 ± 1.4D at the 6th month of postoperative follow-up. The average maximum value of the K index decreased from the preoperative 54.60 ± 3.25 D (in the range from 46.25 to 64.50 D) to the 6-month postoperative value of 45.54 ± 2.72D. Conclusions. The implantation of OCRS in eyes with keratoconus stage II-III with irregular asymmetric paracentral astigmatism is an effective and safe method of increasing visual acuity and reducing refractive errors. Keywords: keratoconus, intrastromal corneal ring segments

Случаи отсутствия лечебного эффекта кросслинкинга при лечении кератоконуса

Purpose. Study of changes in morphometric parameters of cornea in keratoconus before and after corneal collagen crosslinking (CXL). Material and methods. 35 patients (35 eyes) with progressive keratoconus stages 1–3. The indexes of photokeratoscopy were studied in depth (topographer Pentacam (Oculus, Germany). CXL was performed according to the Dresden protocol. A corneal lenticule was used in 6 eyes. The analysis of the studied parameters was carried out initially and after 12 months. Results. By the end of the observation, in all patients, the average values of maximum keratometry (Kmax) decreased statistically significantly from 54.5 to 53.1 diopters, which indicated positive trend. Most indices of keratoconus according to topographer data (ISV, IVA, KI, CKI, IHA, Rmin), as well as the central corneal thickness, on average, significantly decreased. But in 5 patients (all men, mean age 25 years), the Kmax exceeded initial values (from 61.7 to 64.5 diopters), which indicated further progression of keratoconus. The initial values of Kmax in 3 out of 5 of these patients exceeded 57 diopters, which is risk of further progression of keratoconus. Conclusion. With a follow-up period of one year, it was found that CXL in 5 patients (14 %) with keratoconus stages 2-3 turned out to be ineffective. Keywords: keratoconus, photokeratoscopy, corneal collagen crosslinking

Keratoconus and the Impact of Treatment on Patients' Quality of Life: A Qualitative Study.

Keratoconus has a significant impact on patients' quality of life (QoL), from diagnosis to the advanced stages of the disease. The aim of this research was to identify domains of QoL affected by this disease and its treatment. Phone interviews were conducted using a semi-structured interview guide, with patients with keratoconus stratified according to their current treatment. A board of keratoconus experts helped identify the guide's main themes. Thirty-five patients (rigid contact lenses, n = 9; cross-linking, n = 9; corneal ring implants, n = 8; and corneal transplantation, n = 9) were interviewed by qualitative researchers. Phone interviews revealed several QoL domains affected by the disease and its treatments: "psychological", "social life", "professional life", "financial costs" and "student life". All domains were impacted, independently of the treatment history. Few differences were found between treatment regimens and keratoconus stages. Qualitative analysis enabled the development of a conceptual framework based on Wilson and Cleary's model for patient outcomes common to all patients. This conceptual model describes the relationship between patients' characteristics, their symptoms, their environment, their functional visual impairment and the impact on their QoL. These qualitative findings supported the generation of a questionnaire to evaluate the impact of keratoconus and its treatment on patients' QoL. Cognitive debriefings confirmed its content validity. The questionnaire is applicable for all stages of keratoconus and treatments and may help tracking change over time in regular clinical settings. Psychometric validation is yet to be performed before its use in research and clinical practices.

The influence of different factors on corneal biomechanical properties in norm and in progressive keratoconus

A prospective study of corneal stiffness parameter of 174 eyes of 174 healthy subjects with different refractions as well as 56 eyes with keratoconus was carried out. The study groups were comparable in age and gender composition. Correlation was performed between corneal stiffness parameter (Stiffness Parameter (SP-A1), minimum corneal thickness (MCT) and biomechanically compensated intraocular pressure (bIOP) determined using Pentacam HR and Corvis ST (OCULUS, Germany), as well as the anteroposterior chamber (APC) value and patient age. Based on multivariate regression analysis, the correlation between corneal stiffness index SPA1, minimum corneal thickness (MCT) and biomechanically compensated IOP (bIOP) in healthy subjects (p = 0.00001, p = 0.005, respectively) as well as in patients with keratoconus (p = 0.00000, p = 0.0032, respectively) was established. Using the obtained data, the tables for determination of corneal stiffness in healthy subjects and patients with different stages of keratoconus, depending on the minimal thickness and level of biomechanically compensated intraocular pressure, were compiled. Application of the tables will allow in practical work to quickly analyze corneal stiffness index which can be used as an important diagnostic criterion in patients with keratectasia.

Measuring the agreement of keratometry readings of four devices in eyes with keratoconus.

To determine the keratometry measurement agreement using Sirius corneal topography and Scheimpflug camera, Tomey corneal topography, Topcon autokeratorefractometer, and Tomey OA-2000 optical biometry in eyes with different severity of keratoconus. In this retrospective study 115 eyes in different stages of keratoconus were divided into 2 groups of mild (stage 1), and moderate to severe keratoconus (stages 2, 3), according to the Amsler-Krumeich classification. Keratometry measurements were obtained using Sirius corneal topography and Scheimpflug camera (phoenix V3.7.01.08), Tomey corneal topography (Tms SW22C-200S-200), Topcon autokeratorefractometer (KR8900), and Tomey optical biometry (OA-2000 Opt-Meas V.4E). In group 1 All devices demonstrated fair agreement in average keratometry values (95% LoA range > 1 D). However, it was poorer for group 2 (95% LOA range > 3 D). In group 1 Bonferroni test revealed statistically significant difference in average K readings among (Topcon autokeratorefractometer 8900 and Tomey OA-2000 biometry, p < 0.01), and between (Tomey topography and Topcon autokeratorefractometer, p < 0.05). Also in group 2 significant difference was observed in the average keratometry of the most instruments (p < 0.01) except for the (Tomey topography and Topcon autokeratorefractometer) and (Tomey topography and Tomey OA-2000 biometry. According to our investigation in mild, moderate and severe keratoconus the agreement in K reading between Topcon autokeratorefractometer, OA-2000 optical biometry, Sirius topography and Tomey topography was poor. The agreement declines especially in the steep meridian and it was not acceptable clinically. These devices should not be applied interchangeably.

Antioxidant and Anti-Inflammatory Effects of Oral Supplementation with a Highly-Concentrated Docosahexaenoic Acid (DHA) Triglyceride in Patients with Keratoconus: A Randomized Controlled Preliminary Study.

A prospective, randomized, single-center preliminary study was performed in patients with keratoconus stages I-III (Amsler-Krumeich), who received a high rich docosahexaenoic acid (DHA) (1000 mg/day) supplement for 3 months versus untreated patients. One eye per patient was evaluated. Thirty-four patients were recruited (75% men, mean age 31 years), with 15 randomized to the control group and 19 to the DHA-treated group. Corneal topography variables and plasma biomarkers of oxidative stress and inflammatory status were evaluated. A panel of fatty acids in blood samples was also assessed. There were significant between-group differences in the astigmatism axis, asphericity coefficient, and intraocular pressure in favor of the DHA group. Additionally, between-group significant differences in total antioxidant capacity (TAC), malondialdehyde (MDA), free glutathione (GSH) and GSH/GSSG ratio, as well as reduced values of inflammatory markers, including interleukin (IL)-4, IL-6, and vascular endothelial growth factor (VEGF-A) were found. These preliminary findings support the usefulness of the antioxidant and anti-inflammatory effects of DHA supplementation for targeting underlying pathophysiological mechanisms of keratoconus. Prolonged duration of DHA supplementation may be needed to detect more noticeable clinical changes in corneal topography.