Keratoconus Match Index Research Articles

Implantation of Intracorneal Ring Segments in Keratectasia: Effects on Corneal Biomechanics in 112 Eyes.

The aim of this study was to analyze changes in corneal biomechanical properties after implantation of intracorneal ring segments (ICRSs) in keratectasia. This retrospective single-center study included 112 patient eyes that underwent femtosecond laser-assisted ICRS implantation (Intacs SK; Addition Technology Inc, Des Plaines, IL) for keratectasia. Biomechanical analysis was performed using the Ocular Response Analyzer (ORA; Reichert Inc, Depew, NY), with determination of corneal resistance factor, corneal hysteresis, and Keratoconus Match Index, as well as by Corvis ST (OCULUS, Wetzlar, Germany), with determination of stiffness parameter A1, Ambrosio relational thickness to the horizontal profile (Arth), integrated radius, deformation amplitude ratio, and stress-strain index as well as Corvis Biomechanical Index and Tomographic Biomechanical Index. Data collection was performed preoperatively and 6 months postoperatively for ORA and Corvis ST and additionally after 1 and 2 years for ORA. The corneal resistance factor decreased significantly postoperatively (5.8 ± 1.7 mm Hg) compared with preoperatively (6.75 ± 3.7 mm Hg; P = 0.021) and increased again during follow-up (6.2 ± 1.9 mm Hg; P = 0.024), without regaining preoperative values. Corneal hysteresis and Keratoconus Match Index did not change significantly. Stiffness parameter A1 ( P = 0.045) increased significantly after ICRS implantation and Arth decreased significantly from 181 ± 85 to 150 ± 92 ( P = 0.016). However, there was no significant postoperative change for others Corvis parameters. Corneal biomechanical properties showed inconsistent changes after ICRS implantation. Classical corneal biomechanical parameters (using single central air-puff tonometers) do not seem to be suitable for follow-up after ICRS implantation.

Risk Factors for Keratoconus Progression in Children Compared with Young and Middle-aged Adults.

Abstract Background To investigate the risk factors for keratoconus progression in children (10 – 18 years old; age group 1) compared to young adults (19 – 35 years old; age group 2) and middle-aged adults (36 – 55 years old; age group 3). Patients/Methods Ninety-seven children, 445 young adults, and 342 middle-aged adults underwent total ophthalmic examination including clinical refraction, slit lamp examination, corneal tomography, eye biometry, and biomechanical properties measurements. Comparisons were assessed among three age groups and between progressive and nonprogressive eyes. Logistic regression was applied to determine the potential prognostic factors for keratoconus progression in the three age groups. Results Univariate logistic regression analysis show that the most prominent factors associated with progression were corneal posterior vertical radius (RVP), eye rubbing (RUB), slit lamp corneal thinning (SLT), contact lens use (CL), and central corneal thickness (CCT) in all age groups. Additionally, the anterior chamber volume (ACV) and keratoconus match index (KMI) were associated with progression in age group 1. Location of the thinnest corneal thickness at the vertical axis (TCTy), distance from apex to the thinnest point (BADISTAPEX), scissor reflection in retinoscopy (SKIAREFLEX), and Vogt striae were associated with progression in age group 2, and TCTy, anterior and posterior asphericity (ASPA and ASPP, respectively), BADISTAPEX, SKIAREFLEX, and Vogt striae were associated with progression in age group 3. The multivariate model with the highest predictability indicated RVP, ACV, and SLT as independent determinants of progression in age group 1 (AUC: 90%, sensitivity: 88.9%, specificity: 90.9%), RVP, ACV, SLT, and SKIAREFLEX in group 2 (AUC: 81.6%, sensitivity 88.5%, specificity: 70.3%), and RVP, SLT, Vogt striae, and CL in age group 3 (AUC: 80%, sensitivity 82.8%, specificity: 73%). Conclusion ACV and KMI seem to play a major role in the progression of pediatric KC compared to adults. This is probably due to different anatomical and biomechanical characteristics of a childʼs eye globe.

Biomechanical effect of intracorneal ring segment implantation

AbstractBackground: Previous studies have reported significant differences in corneal biomechanics between keratoconic and healthy corneas. Corvis ST® (CST – OCULUS, Wetzlar, Germany) and Ocular Response Analyser® (ORA – Reichelt Inc., Depew, NY, USA) are two single central air‐puff tonometers and are commonly used to analyse the corneal biomechanics. Implantation of intracorneal ring segments (ICRS) using a femtosecond laser represents a reliable surgical option to widen the spectrum of the stage‐related therapy of keratoconus for selected patients. Our purpose was to analyse the change in corneal biomechanical properties after ICRS implantation in keratectasia.Methods: This retrospective monocentric study included 118 patient eyes that underwent femtosecond laser‐assisted ICRS implantation (INTACS SK®, Addition Technology Inc., Des Plaines, IL, USA) for keratectasia. Biomechanical analysis was performed using both ORA, with determination of Corneal resistance factor (CRF), Corneal hysteresis (CH) and Keratoconus Match Index (KMI), as well as by CST with determination of stiffness parameter A1 (SP‐A1), Ambrosio's related thickness to the horizontal profile (Arth), integrated radius (IR), deformation amplitude‐ratio (DA‐ratio) as well as Corvis Biomechanical Index (CBI) and Tomographical Biomechanical Index (TBI). Data collection was performed preoperatively and after 6 months postoperatively for ORA and CST and additionally after 1 and 2 years for ORA.Results: The CRF decreased significantly postoperatively (5.8 ± 1.7 mmHg) compared to preoperatively (6.8 ± 3.7 mmHg; p < 0.001), and increased again during follow‐up (6.2 ± 1.9 mmHg; p = 0.001), without regaining preoperative values. CH and KMI did not change significantly. SP‐A1, IR and DA‐ratio increased significantly after ICRS implantation (p < 0.001). Arth decreased significantly from 190 ± 88 to 157 ± 108. However, there was no significant postoperative change for CBI and TBI.Conclusions: Corneal biomechanical properties showed inconsistent changes after ICRS implantation. The classical corneal biomechanical parameters (using single central air‐puff tonometers) do not seem to be suitable for follow‐up after ICRS implantation.

Impact of Hypothyroidism on Tomography and Biomechanics in Keratoconus - Cross-Sectional and Longitudinal Assessment within the Homburg Keratoconus Center at the Time of Inclusion and after 1 Year.

The etiology of keratoconus (KC) is probably multifactorial but remains essentially unknown. Previous scientific observations have suggested that hypothyroidism might play a role in the development and progression of KC. The purpose of this study was to analyze the tomographic and biomechanical parameters in KC patients with or without hypothyroidism. Twenty-eight patients with KC and hypothyroidism (HT group) and fifty-six KC patients without thyroid dysfunction (WHT group) with matching gender and age were analyzed. Mean age was 40.3 years (range 14 - 57) in the HT group and 40.3 years (range 14 - 57) in the WHT group. Routine ophthalmic examinations consisted of corneal tomography and biomechanical parameters. We extracted the following KC parameters from the Pentacam (Pentacam HR, Oculus, Wetzlar, Germany): Keratoconus Index (KI), maximum keratometry (Kmax), astigmatism, and thinnest pachymetry (TP). From the ocular response analyzer (ORA, Reichert Ophthalmic Instruments, Depew, NY, USA), we extracted corneal hysteresis (CH), corneal resistance factor (CRF), and KC match index (KMI). The comparison of the tomographic and biomechanical values from cross-sectional and longitudinal analyses showed no significant differences between the HT and WHT groups. The severity of KC based on tomographical and biomechanical parameters does not seem to depend on the presence of hypothyroidism.

Tomographically normal partner eye in very asymmetrical corneal ectasia: biomechanical analysis.

To point out the biomechanical changes of the topographically and tomographically normal partner eye (NPE) in patients with very asymmetrical corneal ectasia. Department of Ophthalmology, Saarland University Medical Center in Homburg/Saar, Germany. Retrospective study. The topographical and tomographical results of the NPE were assessed using the Pentacam HR and the biomechanical corneal properties using the Ocular Response Analyzer (keratoconus match index [KMI], corneal hysteresis [CH], and corneal resistance factor [CRF]) and the Corvis ST (topographic biomechanical index [TBI] and Corvis biomechanical index) and compared those results with a normal control group (CG). The clinical records of 26 patients recruited from the Homburg Keratoconus Center diagnosed with a very asymmetrical corneal ectasia were reviewed. The NPE (8.5 ± 1.5 mm Hg) showed a significantly more pathological CH (P < .001) compared with the CG. The CRF was also significantly more pathological (P = .04) for the NPE (8.3 ± 1.5 mm Hg) compared with the CG. The NPE (0.62 ± 0.32) showed a nonsignificant (P = .08) more pathological KMI compared with the CG. Nineteen (73.1%) of 26 NPE had a KMI less than 0.72 and were considered pathological. Compared with the CG, the TBI of the NPE (0.19 ± 0.25) did not differ significantly overall (P = .57). However, 5 (19.2%) of 26 eyes had a TBI more than 0.29 and were considered pathological. Topographically and tomographically NPEs in very asymmetrical corneal ectasia frequently showed biomechanical changes. This should be considered before planning any type of refractive corneal surgery in such patients.

Changes in biomechanical properties of keratoconic corneas following intracorneal ring segment (ICRS) implantation

AbstractPurposeStudies using Corvis ST (CST, Oculus; Wetzlar, Germany) and Ocular Response Analyser (ORA, Reichert, Depew, NY, USA) have reported significant differences between keratoconic and healthy corneas. Implantation of intracorneal ring segments (ICRS) using a femtosecond laser represents a reliable surgical option to widen the spectrum of the stage‐related therapy of keratoconus in patients with contact lens intolerance, post‐LASIK‐keratectasia or pellucid marginal degeneration (PMD). Our aim was to evaluate the ability of the Corvis ST and Ocular Response Analyser to detect the possible stiffening effect after Intacs SK (Addition Technology, Inc.) implantation in patients with keratoconus.Patients and MethodsBetween January 2018 and January 2019, ICRS were implanted in 31 eyes of 27 patients (age 31.9 ± 10.2 years) with clear central cornea. The patients had to fulfill the corneal diagnostic tests required for femtosecond laser‐assisted Intacs SK implantation in 80% depth. The following CST/ORA parameters were recorded: deformation amplitude Ratio (DA Ratio), stiffness parameter at applanation 1 (SP A1), Corvis biomechanical index (CBI), tomographic biomechanical index (TBI), Keratoconus Match Index (KMI), corneal hysteresis (CH) and corneal resistance factor (CRF) preoperatively and 6 months after the ICRS implantation.ResultsDA Ratio (5.43 ± 1.0 vs 5.52 ± 1.1, p = 0.4), SP A1 (58.76 ± 17.5 vs 59.11 ± 17.8, p = 0.4) CBI (0.96 ± 0.1 vs 0.97 ± 0.1, p = 0.3), TBI (0.98 ± 0.0 vs 0.99 ± 0.1, p = 0.3) and KMI (−0.03 ± 0.3 vs −0.17 ± 0.2, p = 0.1) did not change significantly between both time‐points. However, CH (7.96 ± 1.2 vs 7.05 ± 0.9) and CRF (6.33 ± 1.2 vs 5.35 ± 1.2) decreased significantly from preoperative to postoperative measurement time‐point (p = 0.03 for both).ConclusionBoth devices ORA and CST are supposed to analyse the dynamic behavior of the cornea during its temporary deformation by an air puff. The lack of significant changes in the standard parameters of the CST reflects the inability of this device to document the stiffening effect of ICRS in keratoconus patients. In contrast, the standard ORA parameters CH and CRF, but not the KMI, showed a significant decrease 6 month postoperatively. The meaning of those findings in relation to the progression of a keratoconus the disease has to be evaluated further.

The importance of corneal biomechanics in assessing first degree family members of keratoconus patients

Aim: to determine the values of biomechanical parameters (corneal hysteresis - CH, corneal resistance factor - CRF and keratoconus match index - KMI) in patients with keratoconus and their first degree family members. The purpose of the present study was to investigate the importance of assessing corneal biomechanics in subjects at risk of developing the primary ectasia. Materials and methods: 48 participants divided into three groups were analyzed in an observational study after a complete ophthalmological exam with the primary focus on Ocular Response Analyzer. Results: The mean values of CH, CRF, and KMI in the group of relatives were lower compared with the controls but higher when compared with keratoconus patients. We noted significant differences of CH and CRF between all three groups, while in the case of KMI, only the keratoconus group presented statistically significant differences compared with the relatives, respectively with the healthy subjects. Conclusions: the decreased values of CH and CRF may raise the question whether corneal biomechanics could be an adjuvant tool in the screening of a first-degree family member of a keratoconus patient in the attempt of the early detection of a possible forme fruste keratoconus.

Asymmetry between Left and Right Eyes in Keratoconus Patients Increases with the Severity of the Worse Eye

ABSTRACTPurpose: To evaluate whether the inter-eye asymmetry of keratoconus (KC) patients is different from a healthy control group and to investigate how asymmetry changes with increasing severity of the disease.Methods: In this retrospective study, we included both eyes of 350 patients with KC (age 35 ± 13 years) and 68 candidates planned for refractive surgery (control group, age 37 ± 11 years). Inclusion criteria for the KC group were keratoconus in at least one eye with Pentacam Topographical Keratoconus Classification (TKC) of at least 0.5. Patients eligible for refractive surgery in both eyes were included in the control group.Corneal tomography as well as Ocular Response Analyzer measurements were compared between both groups. Subgroup analysis was performed with respect to the TKC staging. Asymmetry was provided as worse eye (defined by higher TKC) minus fellow eye.Results: In the KC group, both eyes showed the same TKC staging in 30.6%, a difference of one stage in 34.0% and of two stages in 24.6% of the patients. The inter-eye asymmetry in the keratoconus group was significantly larger than that in the control group. Corneal power showed an asymmetry of 3.8 ± 4.0 D in keratoconus eyes versus 0.22 ± 0.17 D in the control group. Central corneal thickness (CCT) asymmetry was 34 ± 30 µm versus 6 ± 5 µm, respectively. The Keratoconus Match Index showed an asymmetry of 0.40 ± 0.35 versus 0.15 ± 0.14. The difference between both eyes increased with increasing TKC of the worse eye.Conclusions: Inter-eye asymmetry is larger in keratoconus than in normal eyes, and it increases with keratoconus severity in the worse eye.

Characterization of Ocular Biomechanics in Pellucid Marginal Degeneration

This study sought to investigate the diagnostic capacity of corneal biomechanical response parameters in a group of patients with pellucid marginal degeneration (PMD) using the Ocular Response Analyzer (ORA) and Corvis ST devices. In this prospective clinical study, we used the Corvis ST and ORA devices to investigate the ocular biomechanics of patients with PMD. Eighty-one eyes were included, and 2 study groups were formed: the PMD group (the study group, n = 29) and the control group (n = 52). We focused on 13 biomechanical parameters. Statistical analysis was performed using SPSS. Biomechanical parameters for the 2 groups were compared using analysis of covariance. The ORA results demonstrated that the Keratoconus Match Index was significantly lower in the PMD group than in the control group (0.031 ± 0.37 vs. 0.79 ± 0.33; P = 0.001). The 2 groups did not significantly differ with respect to intraocular pressure- and central corneal thickness-adjusted values for corneal hysteresis or corneal resistance factor. Regarding the Corvis parameters, differences between the control and PMD groups were detected for CorWmax amp (control 1.01 ± 0.01, PMD 1.06 ± 0.01; P = 0.020) and CorA2 t (control 21.78 ± 0.03, PMD 21.66 ± 0.04; P = 0.0003). We identified 2 Corvis parameters that could be used to characterize PMD and differentiate PMD corneas from normal corneas. These parameters support the hypothesis that there is significantly less deformation of the central cornea in PMD corneas than in healthy corneas. However, because useful "first-line" diagnostic devices for diagnosing PMD (such as Pentacam and the ORA) exist, the Corvis ST serves as an additional diagnostic tool that can also be used for long-term monitoring after diagnosis confirmation.

Detection of the early keratoconus based on corneal biomechanical properties in the refractive surgery candidates.

Context:Subclinical keratoconus is contraindication to refractive surgery. The currently used methods of preoperative screening do not always allow differentiating between healthy eyes and those with subclinical keratoconus.Aim:To evaluate biomechanical parameters of the cornea, waveform score (WS), and intraocular pressure (IOP) as potentially useful adjuncts to the diagnostic algorithm for precise detection of the early keratoconus stages and selection of refractive surgery candidates.Settings and Design:Department of Ophthalmology and prospective cross-sectional study.Patients and Methods:Patients enrolled in the study were diagnosed with refractive disorders. We assessed parameters of corneal biomechanics such as corneal hysteresis (CH), corneal resistance factor (CRF), Goldman-correlated IOP (IOPg), corneal compensated IOP, WS, and keratoconus match index (KMI). They were classified into one of three groups based on the predefined KMI range: Group 1 (from 0.352 to 0.757) – 45 eyes, Group 2 (from −0.08 to 0.313) – 52 eyes, and Group 0 - control group (from 0.761 to 1.642) – 80 eyes.Results:In both study groups, IOPg, CRF, and CH were decreased when compared to control (P < 0.0001). In control group, there was positive correlation between CH and KMI (P < 0.05), with no correlations in any of the two study groups. CRF correlated positively with KMI in control (P < 0.0001) and in Group 2 (P < 0.05).Conclusions:CH and CRF, together with WS and IOPg, consist a clinically useful adjunct to detect subclinical keratoconus in patients referred for refractive surgery when based on KMI staging.

Ocular response analyzer (ORA) derived parameters compared to Sirius corneal topography in analyzing corneal pathology

Purpose: To evaluate the ability of Ocular Response Analyzer (ORA) to differentiate between normal and abnormal corneas as compared to Sirius corneal topography. Methods: This retrospective study included 302 eyes of 151 patients. All patients underwent evaluation with ORA and Sirius corneal topography. Parameters included disease classification results on both instruments (device software classification), Surface asymmetry index (SAI) on Sirius, Corneal Hysteresis (CH), Corneal Resistant Factor (CRF), Keratoconus Match Index (KMI), Goldmann-correlated intraocular pressure (IOPg), Corneal compensated intraocular pressure (IOPcc) and waveform score (WS) on ORA. Results: On Sirius, 198 eyes (65.6%) were classified as normal. On ORA, 121 eyes (40.1%) were documented as normal. Overall, 105 eyes (34.8%) were classified as normal and 88 eyes (29.1%) with non-normal classification on both Sirius and ORA. Of the 198 eyes classified as normal on Sirius, 53% were classified as normal, 39% as suspect and 8% as mild keratoconus on ORA (47% non-normal). Of the 121 eyes classified as normal on ORA, 87% were classified as normal, 6% as suspect, and 2% as keratoconus compatible on Sirius (13% non-normal). Four percent of the eyes classified as keratoconus compatible on Sirius were classified as normal on ORA. There was a significant difference when comparing normal and non-normal classifications between ORA and Sirius (p < 0.001) with poor agreement (Kappa=0.32). When including only normal and Keratoconus eyes in the analysis, good agreement was found between the two machines (Kappa=0.75). Conclusion: According to our results there seems to be a significant difference between ORA and Sirius in their ability to differentiate between normal and non-normal eyes. As such, we recommend that these devices not to be used interchangeably for assessing patients prior to refractive surgery. Keywords: Cornea; Corneal biomechanics; Keratoconus; Ocular response analyzer; Sirius corneal topo

Staging of Keratoconus Indices Regarding Tomography, Topography, and Biomechanical Measurements

To derive limits of metric keratoconus indices for classification into keratoconus stages. Validity and reliability analysis of diagnostic tools. A total of 126 patients from the keratoconus center of Homburg/Saar were evaluated with respect to Amsler criteria, using Pentacam (Keratoconus Index [KI], Topographic Keratoconus Classification [TKC]), Topographic Modeling System (Smolek/Klyce, Klyce/Maeda), and Ocular Response Analyzer (Keratoconus Match Probability [KMP], Keratoconus Match Index [KMI]). Mean value, standard deviation, 90% confidence interval, and the Youden J index for definition of the thresholds were evaluated. For separation of keratoconus stages 0/1/2/3/4 we derived the following optimum thresholds: for KI 1.05/1.15/1.31/1.49 and for KMI 0.77/0.32/-0.08/-0.3. For Smolek/Klyce and Klyce/Maeda high standard deviations and overlapping confidence intervals were found; therefore no discrete thresholds could be defined. Nevertheless, for them we still found a good sensitivity and specificity in discriminating between healthy (stage 0) and keratoconus (stages 2-4) eyes in comparison with the other indices. We derived thresholds for the metric keratoconus indices KI and KMI, which allow classification of keratoconus stages. These now need to be validated in clinical use. Smolek/Klyce and Klyce/Maeda were not sufficiently sensitive to allow classification into individual stages, but these indices did show a good specificity and sensitivity in discriminating between keratoconus and healthy eyes.

In vivo confocal laser microscopy of morphologic changes after simultaneous LASIK and accelerated collagen crosslinking for myopia: One-year results

To evaluate the safety of corneal collagen crosslinking (CXL) combined with laser in situ keratomileusis (LASIK). Shinagawa LASIK Center, Tokyo, Japan. Case series. Bilateral myopic LASIK patients had unilateral accelerated CXL (KXL System) in the nondominant eye. After LASIK, riboflavin 0.1% was instilled in the residual stromal bed for 60 seconds. After the riboflavin was washed out and the flap placed in its original position, ultraviolet-A light (30 mW/cm(2)) was administered for 60 seconds. The LASIK-CXL eyes and the LASIK-only eyes were compared. The uncorrected (UDVA) and corrected (CDVA) distance visual acuities, manifest refraction spherical equivalent (MRSE), keratometry values, endothelial cell density (ECD), pachymetry, optical coherence tomography (OCT), corneal hysteresis (CH), corneal resistance factor (CRF), keratoconus match index (KMI), and 37 parameters from a dynamic bidirectional applanation device (Ocular Response Analyzer) were analyzed. Morphologic changes were evaluated using confocal microscopy. No significant differences in UDVA, CDVA, MRSE, ECD, dynamic bidirectional applanation readings (eg, CH, CRF, KMI), or 37 additional parameters were found between the 2 groups (P>.05). Increased hyperreflectivity and a demarcation line similar to that seen after CXL were observed in the LASIK-CXL eyes. The demarcation line (mean depth 200.04 μm ± 27.01 [SD]; range 178 to 278 μm) was present in 23 eyes (95.8%); the line was well defined in 2 eyes (8.3%) and faint in 21 eyes (87.5%). Combined LASIK-CXL was safe, causing insignificant corneal biomechanical and morphologic changes similar to those with CXL treatment only. No author has a financial or proprietary interest in any material or method mentioned.

Diagnostic capacity of biomechanical indices from a dynamic bidirectional applanation device in pellucid marginal degeneration

To evaluate the diagnostic capacity of the keratoconus match index (KMI) and keratoconus match probability (KMP) classification from a dynamic bidirectional applanation device (Ocular Response Analyzer) in eyes with pellucid marginal degeneration (PMD). Department of Ophthalmology, University Clinics Saarland, Homburg, Germany. Cross-sectional study. Pellucid marginal degeneration eligibility was confirmed by inferior peripheral thinning, corneal protrusion, and irregular astigmatism. The KMI and KMP parameters in PMD eyes (study group) were compared with those in normal eyes (control group). The KMI's overall predictive accuracy was assessed operating characteristic (ROC) curves. The relationship between KMI and corneal hysteresis (CH), the corneal resistance factor (CRF), and a series of Scheimpflug camera indices was evaluated with Spearman analysis (r). The mean KMI in the study group (40 eyes) and control group (40 eyes) was 0.34 ± 0.43 (SD) and 0.95 ± 0.30, respectively (P<.001). The KMI correlated significantly with the CH, CRF, and most Scheimpflug camera indices. Regression analysis indicated that the index of height decentration (r = -0.877, P<.001) was the primary determinant of the KMI. Moreover, the KMP index identified 50.0%, 29.16%, and 20.83% of PMD eyes as ectatic, suspect for ectasia, and normal, respectively. The ROC curve analysis of the KMI parameter indicated a predictive accuracy of 94.8% (cutoff point 0.626; sensitivity 85.71%; specificity 90.1%). The KMI seems to be a promising diagnostic index for PMD. In contrast, the KMP index identified a significant percentage of topographically defined PMD eyes as normal, limiting its diagnostic value in PMD. No author has a financial or proprietary interest in any material or method mentioned.

Diagnostic capacity of the keratoconus match index and keratoconus match probability in subclinical keratoconus

To evaluate the diagnostic capacity of the Ocular Response Analyzer's keratoconus match index (KMI) and keratoconus match probability (KMP) classification in keratoconus-suspect eyes. Department of Ophthalmology, University Clinics Saarland, Homburg, Germany. Comparative case series. The KMI and KMP parameters in keratoconus-suspect eyes and normal eyes (control group) were compared. The quantitative keratoconus percentage index was calculated for all suspect eyes. According to the thinnest corneal thickness (TCT), keratoconus-suspect eyes were divided into 2 subgroups: subgroup 1 (TCT <520 μm) and subgroup 2 (TCT >520 μm). The KMI's overall predictive accuracy was assessed using receiver operating characteristic (ROC) curves. The relationship between KMI and a series of Scheimpflug-derived keratoconus-related indices was evaluated using Spearman analysis. The mean KMI was 0.41 ± 0.29 (SD) in the keratoconus-suspect group (50 eyes) and 0.94 ± 0.29 in the control group (50 eyes) (P<.001). Nonsignificant KMI differences were detected between the keratoconus-suspect subgroups (subgroup 1, 27 eyes; subgroup 2, 23 eyes) (P=.059). Nonsignificant correlations were found between Scheimpflug indices and the KMI. The KMP identified 27.65% of control eyes as keratoconus suspect and 10.71%, 28.57%, and 3.57% of keratoconus-suspect eyes as being normal, having mild keratoconus, or having moderate keratoconus, respectively. The ROC analysis for the KMI indicated a predictive accuracy of 94% (cutoff point 0.72). The KMI seems to be a valuable index in the early diagnosis of keratoconus-suspect eyes. The KMP identified a significant percentage of topographically defined keratoconus-suspect eyes as normal or keratoconic. No author has a financial or proprietary interest in any material or method mentioned.

This issue of ACTA, printed and electronic

This issue of <i>ACTA</i>, printed and electronic

Biomechanical diagnosis of keratoconus: evaluation of the keratoconus match index and the keratoconus match probability

To evaluate the diagnostic capacity of the Ocular Response Analyser's keratoconus match index (KMI) and keratoconus match probability (KMP) classification in a sample of keratoconus (KC) patients. Keratoconus match index and KMP from 114 KC eyes, randomly selected from 114 patients with bilateral keratoconus (KCG), were compared with the corresponding ones from 109 normal eyes (CG). Keratoconus match index's predictive accuracy was assessed by receiver operating curves (ROC). Keratoconus match probability level of agreement was evaluated at the different KC stages of the Amsler-Krumeich classification. Correlations were estimated with topographic keratoconus classification (TKC), keratoconus index (KI), index of surface variance (ISV), vertical asymmetry (IVA), height asymmetry (IHA), height decentration (IHD), minimal radius (Rmin), central corneal thickness (CCT), thinnest corneal thickness (TCT) mean keratometry (Km) and intraocular pressure (IOPg). Mean KMI in KCG and CG was 0.20 ± 0.38 and 0.98 ± 0.25, respectively (p < 0.01). Significant KMI differences (p < 0.01) were detected in different KC groups [range: 0.62 ± 0.38 (KC 1), -0.62 ± 0.04 (KC 4)]. Significant correlation was detected between KC staging and KMI (r = -0.56, p < 0.0001). Keratoconus match probability identified 22.03% of the CG eyes as suspect. Moreover, KMP identified 7.01% and 23.68% of the KCG eyes as normal and suspect, respectively. Receiver operating curves analysis for KMI parameter indicated a predictive accuracy of 97.7% (cut-off point: 0.512, sensitivity: 91.18%, specificity: 94.34%). Keratoconus match index seems to be a reliable index in keratoconus diagnosis and staging. Keratoconus match probability identifies a significant percentage of topographically defined KC and CG eyes as suspect. Diagnostic capacity of these novel indexes needs to be further explored.

Ability of keratoconus match index and keratoconus match probability in the differenciation of forme fruste keratoconus and healthy corneas

AbstractPurpose To compare Keratoconus Match Index (KMI) and Keratoconus Match Probability (KMP) of the Ocular Response Analyser (ORA) between forme fruste keratoconus and normal corneas and estimate the sensitivity and the specificity of KMI in discriminating forme fruste keratoconus from healthy corneas.Methods The study population of this retrospective comparative case series was divided into 2 groups: 8 forme fruste keratoconic eyes (FFKCN) and 36 healthy eyes. Every patient underwent a corneal topography, and a biomechanical evaluation with the Ocular Response Analyser. KMI and KMP were compared between the 2 groups. KMI and KMP results from an individual eye are compared to average values from 5 clinically classified populations in a normative database: Normal, Suspect KCN, Mild KCN, Moderate KCN, and Severe KCN. The software determines which population the measurement result best fits.Results The mean KMI 0.67 for FFKCN and 0.928 for control eyes. There was a statistically significant difference between the 2 groups (P = 0.05). For a threshold of 0,8, KMI had a sensitivity of 63% with a specificity of 72%. For a threshold of 10,7mmHg, the CH had a sensitivity of 75% and a specificity of 66,7%. According to the KMP, corneas of the control group match best with the normal group in 64% of the cases. According to the KMP, corneas of the FFKCN group match best with the normal group in 34% of the cases, with the suspect group in 35% of the cases, with the mild, moderate or severe group in 31% of the cases.Conclusion Sensitivity and specificity of the KMI is not greater than those of CH and CRF. The classification proposed by the KMP is not accurate and does not allows the screening of FFKCN.