Keratometry Indices Research Articles

Early, Forme Fruste keratoconus and normal thin cornea, evaluation of sensitive parameters by combined Placido Scheimpflug topography.

To determine the sensitive indices distinguishing forme-fruste keratoconus (FFKC) and early keratoconus (early KC) from thin normal corneas, and their cutoff values using Sirius topography. 156 eyes with normal thin corneas < 500 um (group 1), 99 eyes with early KC (group 2) and 41 eyes with FFKC (group 3), were assessed retrospectively for: corneal keratometric indices, pachymetry indices, corneal aberrations, elevation indices; thinnest corneal point elevation, Q value, root mean square (RMS) withRMS/ area (RMS/A); and KC summary indices of front and back surfaces; surface asymmetry index (SIf, SIb), elevation at KC vertex (KVf, KVb), Baiocchi-Calossi-Versaci index (BCVf, BCVb) and summation of its vector (BCV). Cutoff values were calculated. Keratometry indices were significantly different between early KC and thin normal cases (apex front curvature had the highest area-under-the-ROC-curve (AUROC) (0.926) in early KC, while only apex curvature and coordinates were significant in FFKC cases. Pachymetry indices did not show any significance in differentiating either early KC or FFKC from normal thin corneas. KC summary indices were highly significant among the 3 groups. The highest AUROC was observed with KVb in early KC (0.987) and with KVf in FFKC (0.831). Vertical coma and vertical trefoil showed the highest significance of all aberration parameters differentiating the 3 groups. Thinnest point elevation, RMS and RMS/A showed the highest AUROC in differentiating early KC and FFKC cases from thin normal corneas. Comparing early KC and FFKC to thin normal corneas, Sirius provided high precision in prediction.

Evaluation of corneal topography and higher order aberrations of the fellow eye in unilateral keratoconus

Purpose To assess parameters of corneal topography and higher order aberrations (HOAs) data in the apparently normal contralateral eyes of unilateral keratoconus (KC) cases in comparison with normal eyes of healthy individuals. Patients and methods This observational case-control study included 70 eyes divided into two equal groups; group A was the fellow eyes of unilateral keratoconus patients and group B included the normal control eyes. They were examined by Schimpflug camera to extract the study parameters (keratometry indices, the inferior-superior(I-S) difference at 4 mm, posterior elevation (PE), front and back difference, thickness progression index, corneal pachymetry, multimetric D index (D index), topometric indices and Zernike analysis). Results In comparing the study data between Groups A and B, we demonstrated that ISV, IVA, and CKI had no difference between the two groups. But other topometric parameters showed statistically significant differences between the two groups. Assessment of corneal aberrations revealed that the RMS HOA, vertical coma, and spherical aberrations were associated with significant increases in the apparently normal eyes of unilateral KC cases in comparison with healthy individual eyes (P&lt;0.001). Conclusion Fellow eyes of unilateral KC cases seem not to be totally normal. And so, it is recommended to regularly examine these eyes at close intervals to catch up any abnormality and to avoid KC progression.

Clinical Results of Accelerated Iontophoresis-Assisted Epithelium-on Corneal Cross-linking for Progressive Keratoconus in Children.

To evaluate the clinical characteristics of pediatric patients with progression of keratoconus after accelerated iontophoresis-assisted epithelium-on corneal cross-linking (I-ON CXL) and to assess the efficacy and safety of re-treatment using accelerated epithelium-off CXL (epi-OFF CXL). Sixteen eyes of 16 patients (mean age: 14.6 ± 2.5 years) with keratoconus underwent I-ON CXL. The main outcome measures were uncorrected distance visual acuity, corrected distance visual acuity, maximum keratometry index (Kmax), minimum corneal thickness, elevation front and elevation back measured at the thinnest point, total higher order aberrations root main square (HOA RMS), coma RMS, and spherical aberration. An increment of Kmax greater than 1.00 diopter (D) and a decrease of greater than 20 µm in pachymetry were considered to determine the progression of keratoconus. Patients with progression of keratoconus after I-ON CXL were re-treated using an epi-OFF CXL protocol. Two years after I-ON CXL, 12 patients showed progression of keratoconus, whereas 4 patients were stable. There was significant worsening of Kmax (P = .04) and steepest keratometric reading (P = .01). Furthermore, a significant correlation was documented between progression of keratoconus and age (P = .02). These patients were re-treated using an epi-OFF protocol and after 2 years all patients were stable, and a statistically significant reduction of the mean Kmax (P = .007), HOA RMS (P = .05), and coma RMS (P = 05) was observed. I-ON CXL was ineffective in the treatment of pediatric keratoconus in younger children, whereas it had an efficacy of 2 years in older children. Re-treatment using epi-OFF CXL proved effective to halt progression of keratoconus after I-ON CXL failure. [J Pediatr Ophthalmol Strabismus. 2024;61(1):44-50.].

Scleral Lens Applications Focused on Korean Patients with Various Corneal Disorders.

We aimed to report on the clinical outcomes of scleral lens applications in Korean patients with various corneal disorders. This retrospective review was conducted for 62 eyes of 47 patients who had been fitted with scleral lenses for various corneal disorders. The patients were referred for inadequate spectacle-corrected visual acuity and rigid gas permeable (RGP) or soft contact lens intolerance. Uncorrected visual acuity, habitually corrected visual acuity, best lens-corrected visual acuity, topographic indices, keratometry indices, and lens parameters were evaluated. Twenty-six eyes of 19 patients with keratoconus were enrolled. Other conditions included corneal scar (13 eyes of 12 patients), phlyctenules (three eyes), laceration (four eyes), chemical burn (one eye), keratitis (one eye), Peters' anomaly (one eye), fibrous dysplasia (one eye), ocular graft-versus-host disease (two eyes of one patient), irregular astigmatism (18 eyes of 12 patients), and corneal transplant status (five eyes of four patients). The mean topographic values of the eyes include flat keratometric value (43.0 ± 6.1 diopters [D]), steep keratometric value (48.0 ± 7.4 D), and astigmatism (4.9 ± 3.6 D). Of the eyes fitted with scleral lenses, best lens-corrected visual acuity (0.10 ± 0.22 logarithm of the minimum angle of resolution [logMAR]) was significantly better than the habitually corrected visual acuity (0.59 ± 0.62 logMAR, p < 0.001). Scleral contact lenses are a good alternative for patients with corneal abnormalities and those who are intolerable to RGP contact lenses, resulting in both successful visual outcomes and patient satisfaction, especially concerning keratoconus, corneal scar, and corneal transplant status.

Outcomes of a Single-Segment Intrastromal Corneal Ring in Early Keratoconus and Early Pellucid Marginal Degeneration.

To determine the effect of a single-segment intrastromal corneal ring segment (ICRS; Intacs SK) on early keratoconus (KCN) and pellucid marginal degeneration (PMD). It is a prospective interventional study. One hundred twenty-four eyes (99 patients) with KCN and 36 eyes (26 patients) with PMD at early stage (the maximum keratometric reading less than 55 diopters) were included to ICRS implantation using femtosecond laser at a tertiary university-based hospital and a private outpatient center. The uncorrected distance and spectacle-corrected visual acuity (UDVA and SCDVA), manifest spherical and cylindrical refractions, and keratometry indices were measured preoperatively and postoperatively, 1week, 2 and 6months. One week after surgery, significant improvements were observed in UDVA, SCDVA, cylinder and keratometry readings of both KCN and PMD groups (all P < 0.05) with no significant changes afterward. No significant change occurred in the sphere refraction of PMD group (P = 0.10) in contrast to KCN group (P < 0.001). Corneal irregularity of KCN group in central 3 and 5mm zones increased at 1week (both P < 0.001) and then started to decrease up to 6months. However, the corneal irregularity of PMD group had significant reduction only at 1week in 5-mm zone (P = 0.02) and 2months in 3-mm zone (P = 0.01) postoperatively. The final efficacy indexes were 1.44 ± 0.71 and 0.87 ± 0.40 in KCN and PMD groups, respectively. Visual acuity, refractive errors and keratometry values have been improved after one-segment Intacs SK implantation in early KCN and PMD patients.

Corneal Scheimpflug topography values to distinguish between normal eyes, ocular allergy, and keratoconus in children

To identify and compare keratometric, corneal thickness, and elevation parameters and indices among healthy children, ocular allergy, and keratoconus using the OCULUS Pentacam Scheimpflug topography system. This study included healthy children, children with ocular allergy (OA) without keratoconus, and children with keratoconus (KC). The study design consisted of a prospective evaluation and review of medical records from a Brazilian ophthalmology department. The exclusion criteria were inability to undergo the ocular exam, other ocular diseases, contact lens wear, and topographic corneal ectasia. The effect of each corneal parameter was evaluated using univariate and multivariate logistic regression models adjusted for sex and age, and ROC curves were used to assess the ability each variable to discriminate among groups. A total of 182 subjects were included: healthy children (n = 99), children with OA (n = 32), and children with KC (n = 51). Groups differed in terms of sex, with more males in the OA group (73.2%) and the KC group (67.7%) than in the control group (40.9%). All corneal parameters studied differed significantly between the control and KC groups, and between the OA and KC groups; they also differed significantly between the three groups in terms of astigmatism, q-value, CCT, TP, BAD-D, and ARTmax values. We present the first study to describe and compare corneal tomographic parameters in healthy children, OA, and KC. Keratometry indices, ACD, ARTmax, AETP, and PETP were found to be the most useful for differentiating between healthy and KC children.IBR registry number: CAAE 54921916.9.0000.5404.

Keratoconus Diagnostic and Treatment Algorithms Based on Machine-Learning Methods.

The accurate diagnosis of keratoconus, especially in its early stages of development, allows one to utilise timely and proper treatment strategies for slowing the progression of the disease and provide visual rehabilitation. Various keratometry indices and classifications for quantifying the severity of keratoconus have been developed. Today, many of them involve the use of the latest methods of computer processing and data analysis. The main purpose of this work was to develop a machine-learning-based algorithm to precisely determine the stage of keratoconus, allowing optimal management of patients with this disease. A multicentre retrospective study was carried out to obtain a database of patients with keratoconus and to use machine-learning techniques such as principal component analysis and clustering. The created program allows for us to distinguish between a normal state; preclinical keratoconus; and stages 1, 2, 3 and 4 of the disease, with an accuracy in terms of the AUC of 0.95 to 1.00 based on keratotopographer readings, relative to the adapted Amsler–Krumeich algorithm. The predicted stage and additional diagnostic criteria were then used to create a standardised keratoconus management algorithm. We also developed a web-based interface for the algorithm, providing us the opportunity to use the software in a clinical environment.

Десятилетний опыт применения оригинального алгоритма хирургического лечения пациентов с начальными стадиями кератоконуса

Purpose. Analyze of the long-term results of treatment of patients with progressive keratoconus initial stages performed according to the developed algorithm. Material and methods. Clinical studies were carried out on the basis of a retrospective analysis of three comparison groups, depending on the tactics of surgery. Group 1 consisted of 843 patients (1186 eyes) with progression of keratoconus who underwent crosslinking. Group 2 consisted of 1185 patients (1343 eyes) who underwent intrastromal keratoplasty with implantation of corneal segments (ISKP with implantation of RS) with a mechanical (1007 eyes) or femtolaser (336 eyes) method. Group 3 consisted of 912 patients (1270 eyes), these patients underwent combined treatment – ISKP+UV crosslinking. The observation was carried out for 10 years. Results. As a result of the observation of patients for 10 years from the moment of UV crosslinking, an increase in UCVA and BCVA was revealed 10 years after surgery by 0.33±0.05 and 0.2±0.04, respectively. There was a significant increase in the central thickness of the cornea, on average by 12.75±0.08µm after 10 years. When analyzing the results of the observation of group 2, an increase in UCVA and BCVA was observed by 3–6 months after MS implantation. Keratometry indices (Kmax) decreased by an average of 3.5±1.3 diopters after 10 years. There was an increase in the central corneal thickness by 19.25±2.2µm after 10 years. As a result of the observation of patients for 15 months after the combined treatment (UV-crosslinking+ISCP), an increase in UCVA and BCVA was revealed by 0.17±0.10 and 0.25±15, respectively. Keratometry indices (Kmax) decreased by an average of 4.1±0.9 diopters after 15 months. There was an increase in the central corneal thickness by an average of 15±6.2µm after 15 months. Conclusion. Our research has shown that after 6 years there is no need to repeat UV crosslinking. With the correct location of the corneal segments, the progression of ectasia stops, and the UCVA and BCVA increase. Differences were revealed in the dynamics of the postoperative course in patients with combined UV crosslinking and implantation of corneal segments, which is obviously associated with their mutual effect on the ectasized cornea. In order to improve the quality of life of patients with the initial stages of keratoconus, these methods of treating keratectasias can be used in wide clinical practice without the threat of a decrease in clinical and functional results over a long period of time. Key words: keratoconus, classification, algorithm, crosslinking, corneal segment

Методика акселерированного кросслинкинга с использованием защитного донорского лоскута роговицы в лечении прогрессирующего кератоконуса на «тонких» роговицах

Purpose. To develop a method of accelerated ultraviolet crosslinking with an initial corneal thickness equal to or less than 400 microns using a protective donor corneal flap. Definition of safety and effectiveness of this method in the treatment of progressive keratoconus. Material and methods. 20 patients (20 eyes) with a diagnosis of progressive keratoconus 2–3 stages were included in the study. The accelerated crosslinking was carried out with an IROC-VX-2000 device (Switzerland). A protective donor corneal flap was cut out by using a Femto LDV Z8 femtosecond laser (Ziemer, Switzerland). The thickness of the protective flap of the donor cornea was determined as the difference between 450 μm and the obtained value of the patient's pachymetry in 30 minutes of saturation with Dextralink in μm. Results. Indicators of uncorrected visual acuity and corrected visual acuity returned to the level of preoperative values and did not tend to decrease until the end of the observation period for 6 months. The average keratometry indices gradually decreased: after 3 months – 50.3 ± 1.5 μm, after 6 months – 48.9 ± 1.8 μm, by 12 months – 46.7 ± 2.1 μm. A decrease in elevation indicators of the anterior and posterior surfaces was marked on elevation maps throughout the observation period. Conclusion. The proposed ultraviolet crosslinking technique using a protective donor corneal flap in patients with corneal thickness 400 μm or less is reproducible. This technique proves its effectiveness and safety and allows to stabilize the condition in patients with progressive keratoconus with adequate visual function. This makes this technique necessary, taking into account the lack of adequate cross-linking technology with a thin cornea. Keywords: progressive keratoconus, thin cornea, ultraviolet crosslinking, protective donor corneal flap.

Topography guided custom ablation treatment for residual refractive error after keratoplasty

To evaluate the efficacy and safety of topography-guided custom ablation photorefractive keratectomy (TCAT) in treating residual refractive error and astigmatism after keratoplasty. Medical records of all patients who underwent TCAT from 2013 to 2017 for residual refractive error and irregular astigmatism after keratoplasty were reviewed. Data were collected on patient demographics, surgical details and preoperative and 6 months postoperative refraction, corrected distance visual acuity (CDVA), uncorrected distance visual acuity (UDVA) and keratometry indices. The procedure was comprised of two stages where stage-1 was aimed at decreasing the irregular astigmatism and stage-2 at correcting the refractive error. Stage 2 was only performed if the corneal parameters including residual stromal bed were within acceptable limits. Forty-six eyes of 46 patients were included. Nineteen eyes underwent stage-1 TCAT treatment only (Group-1). Nine eyes underwent stage-2 TCAT six months after the stage 1 (Group-2) and 18 eyes underwent a simultaneous stage 1 and 2 procedure (Group-3). Six months following TCAT, CDVA improved in 69.6% This success rate was 63.2% in Group-1, 44.4% in Group-2 and 88.9% in Group-3. Median spherical equivalent (SE) decreased from −4.5D preoperatively to −2.5D postoperatively and the median cylinder decreased from 3.25D preoperatively to 2.43D postoperatively. Comparing to Group-2, eyes in Group-3 experienced larger reduction in SE and astigmatism. Treatment of patients with post-keratoplasty residual refractive error and astigmatism with TCAT resulted in successful outcomes with improvements CDVA and UDVA. Performing a simultaneous two-stage TCAT procedure appeared to be more effective in reducing the refractive error.

Bowman layer transplantation in eyes with progressive advanced keratoconus

Purpose:to study the efficiency of Bowman layer transplantation (BLT) in corneal stroma for the treatment of progressive keratoconus (KC).Material and methods.30 patients (30 eyes) with progressive KC stages III to IV (according to Amsler — Krumeich classification), underwent BLT into a mid-stromal pocket. At the time of surgery, the patients were 14 to 37 (averagely 26.6 ± 6.2 years). Before and after the surgery, the maximum keratometry index (Kmax) and the corneal thinnest point (CTP) values were determined. Also, we evaluated visual acuity before and after surgery in scleral contact lenses, endothelial cells density (ECD) and the depth of graft location. The indication for surgery was the refusal of corneal transplantation, progression of KC, contraindications for ultraviolet crosslinking or implantation of intracorneal ring segments based on the CTP and Kmax values. The follow-up continued 6 to 36 months (averagely, 26.6 ± 6.0 months).Results.Throughout the observation period, no intra or postoperative complications associated with BLT or deterioration of CTP, Kmax or best corrected visual acuity (BCVA) in scleral lenses were noted.Conclusions.Kmax, CTP and ECD values remaining stable during the follow-up is the evidence of a stabilizing BLT effect on the KC progression. The absence of BCVA decrease in scleral lenses indicates a functional safety of BLT.

Keratoconus after 40years of age: a longitudinal comparative population-based study.

To determine 5-year changes in keratoconus indices and corrected distance visual acuity in 40-64-year-old keratoconus compared with normal subjects. In this prospective population-based cohort study, 5-year changes in Belin grading system indices including the average radii of curvature in the 3mm zone surrounding the thinnest point in the anterior (ARC-3mm) and posterior (PRC-3mm) cornea, corrected distance visual acuity, minimum corneal thickness, maximum Ambrosio's relational thickness (ART-max), and maximum anterior keratometry indices centered on steepest point in the central 3mm (Kmax-3mm), 4mm (Kmax-4mm), and 5mm (Kmax-5mm) zones were compared between keratoconus and normal participants. In the analysis, comparisons were made between all keratoconus eyes and the right eyes of normal participants. The mean age in the keratoconus (n = 16 eyes) and normal (n = 1986 eyes) groups (48.31 ± 4.78, 49.37 ± 5.79years, respectively) was not statistically different (P = 0.327). The two groups differed in terms of changes in PRC-3mm (- 0.07 ± 0.15 vs. + 0.001 ± 0.14mm, respectively, P = 0.042) and ART-max (- 6.28 ± 25.19 vs. + 15.8 ± 72.7μm, respectively, P = 0.003). There were significant correlations between the reduction in PRC-3mm and its baseline value (β = - 0.20, P < 0.001) and keratoconus (β = - 0.26, P < 0.001). The reduction in ART-max significantly correlated with its baseline value (β = - 0.43, P < 0.001) and keratoconus (β = - 111.74, P < 0.001). According to these findings, posterior corneal steepening and thinning in keratoconus patients continue after the age of 40years, but it is clinically negligible. The changes are independent of normal age-related changes and appear to be slower in cases with steeper and thinner corneas.