Corvis Scheimpflug Technology Research Articles

Alterations in Corneal Sensitivity, Staining and Biomechanics of Alopecia Areata Patients: Novel Findings in a Case-Control Study.

Background: A higher prevalence of ophthalmological alterations in systemic inflammatory diseases has been demonstrated. Objectives: Our objectives were to determine anterior segment findings and corneal properties in alopecia areata (AA). Methods: This is a case-control study. Severe AA patients (Severity of Alopecia Tool > 50%) and non-AA subjects underwent a general ophthalmological examination, a Pentacam and Corvis scheimpflug technology examination (Oculus Optikgeräte GmbH, Wetzlar, Germany). Visual acuity, refractive error, corneal aesthesiometry, and biomechanical and topographic variables were registered. Results: In total, 25 AA patients (50 eyes; 50.6 ± 8.1 years) and 29 controls (58 eyes; 49.4 ± 8.6 years) were included. AA patients had decreased corneal sensitivity, more corneal staining, and a more advanced cataract (p ≤ 0.004). The anterior topographic flat meridian, mean anterior keratometry, and maximum keratometric point were increased in AA (p ≤ 0.040), while pachymetry values were thinner (p ≤ 0.001). Keratoconus index and Belin/Ambrosio-enhanced ectasia total deviation display were increased (p ≤ 0.007). Two eyes with a topographic diagnosis of keratoconus and four eyes with subclinical keratoconus were detected in AA. Applanation lengths were smaller in AA (p ≤ 0.029). The Corvis Biomechanical Index was increased in AA (p = 0.022). Conclusions: AA patients have reduced corneal sensitivity and increased corneal staining. Topographic and biomechanical parameters are altered, and there could be a higher risk of keratoconus, thus possibly requiring routine ophthalmological examination.

Intraocular lens power calculation: angle κ and ocular biomechanics

Purpose: To study the effect of ocular biomechanics on the prediction error of intraocular lens (IOL) power calculation. Setting: Centro Hospitalar Universitário do Porto, Porto, Portugal. Design: Prospective longitudinal study. Methods: This study included 67 subjects. Before cataract surgery subjects underwent biometry with IOLMaster 700 and biomechanical analysis with Corvis Scheimpflug technology. The targeted spherical equivalent was calculated with SRK-T and Barrett Universal II. Associations between prediction error (PE), absolute prediction error (AE), and biometric and biomechanical parameters were performed with stepwise multivariate linear correlation analysis. Results: Using the SRKT formula, there was association between PE and Corvis Biomechanical Index (CBI, B = −0.531, P = .011) and between AE and the horizontal offset between the center of the pupil and the visual axis (angle κ, B = −0.274, P = .007). Considering the Barret Universal II formula, PE was independently associated with anterior chamber depth (B = −0.279, P = .021) and CBI (B = −0.520, P = .013) and AE was associated with angle κ (B = −0.370, P = .007). Conclusions: A large angle κ may reduce the predictability of IOL power calculation. Ocular biomechanics likely influence the refractive outcomes after IOL implantation. This study showed that eyes with softer corneal biomechanics had more myopic PE. This may relate to anteriorization of the effective lens position. Dynamic measurements may be the way to progress into future formulas.

Intraocular pressure trend following myopic photorefractive keratectomy.

To evaluate the intraocular pressure (IOP) trend and risk factors for IOP rise after myopic photorefractive keratectomy (PRK). One eye of each patient undergone PRK for myopia was randomly assigned to this study. All eyes underwent tonometry by CorVis Scheimpflug Technology (CST) tonometer (Oculus Optikgeräte GmbH, Wetzlar, Germany) 1week, 2weeks, 1month, 2months, 3months and 4months after surgery. The eyes with IOP rise more than 5mmHg and the risk factors were evaluated by Kaplan-Meier graph and multiple Cox regression analysis. A total of 348 eyes of 348 patients were enrolled in this study. Forty-three eyes (12.35%) experienced a steroid-induced IOP rise of more than 5mmHg. Eyes with IOP rise had higher baseline IOP (Median 19mmHg (IQR 18-22) versus Median 15mmHg (IQR 14-16); p < 0.001). Baseline central corneal thickness (CCT) was higher in eyes without IOP rise (Median 520µm (IQR 509-541) versus Median 535µm (IQR 518-547); p = 0.009). In multivariate Cox regression analysis, higher baseline IOP was a risk factor for IOP rise (Hazard Ratio (HR) 1.59 (95% CI 1.43-1.77); p < 0.001) while higher baseline CCT was protective (HR 0.97 (95% CI 0.95-0.98); p < 0.001). Eyes with higher baseline IOP and lower baseline CCT are at increased risk of IOP rise after PRK and should be monitored more frequently.

Correction methods for noncontact intraocular pressure measurement in patients with keratoconus and healthy individuals.

The objective of this study was to investigate the usefulness of four different algorithms to correct noncontact intraocular pressure measurement errors in keratoconus patients and normal individuals. Noncorrected intraocular pressure and corrected intraocular pressures were measured in one eye of 34 patients with keratoconus and 34 age- and gender-matched healthy controls using Corvis Scheimpflug Technology. The correlation of noncorrected intraocular pressure and corrected intraocular pressures with age, axial length, corneal shape, thickness, and biomechanics was calculated. Corrected intraocular pressures were compared with noncorrected intraocular pressure using paired t test and Bland-Altman plots (95% limits of agreement). The noncorrected intraocular pressure correlated with corneal thickness and biomechanical parameters in both groups (all p≤0.047), and front and back mean keratometry in the keratoconus group (r=-0.39, p=0.02, and r=0.39, p=0.02, respectively). After adjustment with different intraocular pressure correction algorithms, biomechanically corrected intraocular pressure showed a minimal correlation with corneal features and a nonsignificant difference with noncorrected intraocular pressure in the healthy group (-0.1 ± 1.1 mmHg, p=0.58; 95% limits of agreement: -2.3 to 2.1 mmHg). Measuring intraocular pressure using noncontact tonometry and its corrected forms with a corneal thickness-based simple linear formula in patients with keratoconus is associated with many errors. Using more complex formulas that take into consideration more corneal stiffness parameters in addition to corneal thickness, such as biomechanically corrected intraocular pressure formula, may be more reliable and beneficial in this group of patients.

Study of corneal biomechanical properties in patients with childhood glaucoma.

To study of corneal biomechanical properties and intraocular pressure (IOP) measured with Corvis Scheimpflug Technology (ST) in patients with childhood glaucoma (CG). Cross-sectional study in which 89 eyes were included 56 of them with CG. Only one eye per patient was included. The following variables were obtained from the clinical history and the ophthalmological examination: age, sex, IOP, number of surgeries, and the cup/disc ratio (CDR). The following parameters were recorded using Corvis ST: corrected by biomechanics IOP (bIOP), not corrected IOP (nctIOP), central corneal thickness (CCT), maximum concavity [radius, peak distance (PD) and deformation amplitude], applanation 1 and 2 (length and velocity). The mean age was 23±14.55 and 33±19.5 years old for the control group and CG group, respectively. Totally 36 were males and 53 were females. In the CG group, 7 patients were controlled only with medical treatment. Sixteen had at least one previous goniotomy, 19 had at least one trabeculectomy, and 11 had an Ahmed implant. A significant and positive intraclass correlation coefficient was found between Goldman IOP and the IOP measured by Corvis in both groups. No differences were found between the IOP measured with Corvis and Goldman using a student t-test. Regarding biomechanical parameters, there were differences in the applanation length 2 (A-L2), in the applanation velocity 2 (A-V2) and in the PD. By sex, only the applanation length 1 (A-L1) was found to be different in control group. A positive and significant Pearson correlation was found between CDR and the A-L1. Corneal biomechanical properties have shown differences between CG and healthy subjects and also between men and women.

A comparison of the corneal biomechanics in pseudoexfoliation syndrome, pseudoexfoliation glaucoma, and healthy controls using Corvis® Scheimpflug Technology.

Purpose:To compare the corneal biomechanical parameters among pseudoexfoliation syndrome (PXF), pseudoexfoliation glaucoma (PXG), and healthy controls using Corvis Scheimpflug Technology (ST).Methods:A prospective, cross-sectional study of 141 treatment-naïve eyes that underwent Corvis ST was conducted. These included 42 eyes with PXF, 17 eyes of PXF with ocular hypertension (PXF + OHT) defined as intraocular pressure (IOP) >21 mmHg without disc/field changes, 37 eyes with PXG, and 45 healthy controls. Corneal biomechanical parameters, which included corneal velocities, length of corneal applanated surface, deformation amplitude (DA), peak distance, and radius of curvature, were compared among the groups using analysis of variance models.Results:The four groups were demographically similar. The mean IOP was lower in the controls (15.6 ± 3 mmHg) and PXF group (16.0 ± 3 mmHg) compared to the other two groups (>24 mmHg). Corneal pachymetry was similar across the four groups. Mean DA was significantly lower (P < 0.0001) in the PXG group (0.91 ± 0.18 mm) and the PXF + OHT group (0.94 ± 0.13 mm) when compared to the PXF (1.10 ± 0.11 mm) and control groups (1.12 ± 0.14 mm). Corneal velocities were also found to be statistically significantly lower in PXG and PXF + OHT compared to the PXF and control groups. However, after adjusting for age and IOP, there was no difference in any of the biomechanical parameters among the four groups.Conclusion:Corneal biomechanical parameters measured on Corvis ST are not different between healthy controls and eyes with PXF and PXG. Since PXG is a high-pressure glaucoma, corneal biomechanics may not play an important role in its diagnosis and pathogenesis.

Evaluation of Biomechanically Corrected Intraocular Pressure Measurements in Keratoconus and Forme Fruste Keratoconus

Introduction: Although biomechanically corrected intraocular pressure (bIOP) is available, the effectiveness of intraocular pressure (IOP) correction in keratoconus and forme fruste keratoconus (FFK) eyes has not been investigated. Objective: Evaluation of bIOP measurements in eyes with keratoconus and FFK. Methods: Forty-two eyes in 21 patients with keratoconus in one eye and FFK in the fellow eye were examined (KC/FFK group; mean age 24.62 ± 8.6 years; 16 males and 5 females). The control group consisted of 62 eyes in 31 unaffected subjects (mean age 26.26 ± 3.64 years; 15 males and 16 females). The bIOP was determined using a Scheimpflug-based tonometer (Corvis Scheimpflug Technology [Corvis ST®]) after measuring the IOP with a conventional non-contact tonometer (NIOP). The agreement between NIOP and bIOP values was examined using the Bland-Altman plot. The difference between NIOP and bIOP (bIOP correction amount) was compared between keratoconus and FFK eyes. Results: In the control group, there were no significant differences between right and left eyes in both NIOP and bIOP values (p = 0.975 and p = 0.224, respectively). In the KC/FFK group, NIOP values were significantly lower in the keratoconus eyes (9.93 ± 1.96 mm Hg) than in the FFK eyes (12.23 ± 3.03 mm Hg; p = 0.0003). There was no significant difference in bIOP values between the right and left eyes of the KC/FFK group (p = 0.168). The bIOP correction amount was significantly increased in keratoconus eyes (3.58 ± 2.12 mm Hg) compared to in FFK eyes (1.80 ± 3.32 mm Hg; p = 0.011). Conclusions: For eyes with keratoconus and FFK, the bIOP method is effective to adjust IOP measurements based on corneal biomechanical properties.

Relationship between corneal deformation amplitude and optic nerve head structure in primary open-angle glaucoma.

The purpose of the study was to investigate the relationship between corneal deformation amplitude (DA), which is the amount of corneal displacement at highest degree of concavity measured by Corvis Scheimpflug Technology (ST), and various optic nerve head parameters in patients with primary open-angle glaucoma (POAG).Fifty-eight POAG patients were included in this observational study. For each patient, DA with Corvis ST, color optic disc photography, and optic nerve head imaging by enhanced depth imaging with a Heidelberg spectralis optical coherence tomography (OCT), Cirrus OCT, and Heidelberg retina tomograph (HRT) were obtained. Pearson correlation was used to analyze the relationship between DA and optic nerve head parameters before and after adjusting for age, intraocular pressure, central corneal thickness, and axial length.Corneal DA was negatively associated with lamina cribrosa (LC) depth (r = −0.390, P = .003) after adjusting for confounders. It showed positive relationship with parapapillary atrophy (PPA) area (r = 0.321, P = .046). In addition, the corneal DA was negatively correlated with cup volume (r = −0.351, P = .017) and mean cup depth (r = −0.409, P = .005) measured by HRT.Corneal DA is related with optic nerve head parameters in patients with POAG. Patients with lower corneal DA showed greater LC depth, greater cup area, deeper cup, and smaller PPA than those with higher corneal DA.

Comparison of different devices to measure the intraocular pressure in thyroid-associated orbitopathy.

To evaluate the correlation of the intraocular pressure measurements (IOP) with non-contact tonometer Corvis Scheimpflug technology (Corvis ST), Goldmann applanation tonometry (GAT), ocular response analyzer (ORA), and iCARE rebound tonometer in patients with thyroid-associated orbitopathy (TAO) and eye-healthy subjects (control group). Twenty-nine consecutive patients with TAO (79% female) and 30 eye-healthy subjects (60% female) were included in this prospective, age- and sex-matched study. The IOP measurement with Corvis, ORA, GAT, iCARE, and central corneal thickness (CCT) with Corvis was obtained from all study participants. The mean age of the patients was 51 ± 10years in patients with TAO and 56 ± 13years in the control group. The mean IOP measurements with GAT, Corvis, ORA, and iCARE were 15.93 ± 4.42mmHg, 18.10 ± 7.54mmHg, 18.40 ± 7.93mmHg, and 16.61 ± 7.96mmHg in patients with TAO and 14.52 ± 3.02mmHg, 14.48 ± 3.38mmHg, 15.29 ± 4.64mmHg, and 14.13 ± 3.85mmHg in the control group (P = 0.157, P = 0.004, P = 0.017, and P = 0.176 respectively). The mean CCT was 547.5 ± 39.2μm in patients with TAO and 560.8 ± 49.8μm in the control group ( P= 0.261). The data collected shows an agreement between the iCARE and GAT IOP measurements in TAO patients and in eye-healthy patients. However, the mean value of IOP measurements with Corvis and ORA was significantly higher in patients with TAO in comparison with the control group (P = 0.044 and P = 0.029 respectively).

Corneal Biomechanics in Unilateral Keratoconus and Fellow Eyes with a Scheimpflug-based Tonometer.

Before the appearance of evident keratoconus, corneal biomechanical changes may be detectable. Here, these properties are analyzed to detect any difference that could help in the early recognition of keratoconus to allow patients to benefit from early treatments and to avoid refractive procedures in these corneas. The purpose of this study was to compare corneal biomechanical characteristics as determined by Corvis Scheimpflug Technology tonometry between normal eyes and asymmetric keratoconic eyes. Retrospective data from normal eyes (n = 100), keratoconic eyes (n = 18), and their topographically normal fellow eyes (n = 18) were analyzed. Differences in the variables among the groups were determined. For the parameters that showed significant differences, the receiver operating characteristic curve and the area under the curve (AUC) were used to assess the diagnostic accuracy of each variable. The optimal cutoff points were determined when comparing normal and fellow eyes. Also, a new linear combination of variables was performed to obtain better discriminative values. The following variables differed significantly between normal and fellow eyes: length of the flattened cornea in the second applanation, peak distance, curvature radius at highest concavity, and central corneal thickness. When each variable was independently considered, AUCs, sensitivity, and specificity were insufficiently high for good discrimination between the two groups. However, using a linear combination of variables, an optimal cutoff point (0.157) was obtained with an AUC of 0.78, sensitivity of 0.84, and specificity of 0.69. A best predictive linear combination of corneal biomechanical variables was tested including diameter of the flattened cornea in the second applanation and central corneal thickness. This combination was considered as the best in terms of its prediction capacity, simplicity and clinical application. This formula may be useful in clinical practice to discriminate between normal eyes and incipient keratoconus.

Changes in intraocular pressure values measured with noncontact tonometer (NCT), ocular response analyzer (ORA) and corvis scheimpflug technology tonometer (CST) in the early phase after small incision lenticule extraction (SMILE).

BackgroundCorneal biomechanical properties are always compromised after corneal refractive surgeries thus leading to underestimated intraocular pressure (IOP) that complicates the management of IOP. We investigated the changes in postoperative baseline of IOP values measured with noncontact tonometer (NCT), ocular response analyzer (ORA) and corvis scheimpflug technology (CST) in the early phase after small incision lenticule extraction (SMILE).MethodsTwenty-two eyes (−6.76 ± 1.39D) of 22 moderate and high myopes, (28.36 ± 7.14 years, 12 male and 10 female) were involved in this prospective study. IOP values were measured using a non-contact tomometer (NCT-IOP), an ocular response analyzer (corneal-compensated IOP, IOPcc and Goldmann-correlated IOP, IOPg) and a Corvis scheimpflug technology tonometer (CST-IOP) preoperatively, at 20 min and 24 h, postoperatively. Repeated measures analysis of variance (RM-ANOVA), Pearson’s correlation analysis and multiple linear regression models (stepwise) were performed. Cut-off P values were 0.05.ResultsExcept for IOPcc, NCT-IOP, IOPg, and CST-IOP values significantly decreased after SMILE procedure (All P values <0.05). ΔCCT, as well as ΔMRSE and ΔKm, did not significantly correlated with ΔNCT-IOP, ΔIOPcc, ΔIOPg or ΔCST-IOP, (all P values >0.05). Multiple linear regression models (stepwise) showed that the practical post-operative IOP value was the main predictor of the theoretical post-operative NCT-IOP, IOPcc and IOPg values (all P values <0.001). The postoperative applanation time 1 (AT1) value (B = 8.079, t = 4.866, P < 0.001), preoperative central corneal thickness (CCT) value (B = 0.035, t = 2.732, P = 0.014) and postoperative peak distance (PD) value (B = 0.515, t = 2.176, P = 0.043) were the main predictors of the theoretical post-operative CST-IOP value.ConclusionsIOP values are underestimated when assessed after SMILE by using NCT-IOP, IOPg and CST-IOP. The practical postoperative IOPcc value and theoretical post-operative CST-IOP value may be more preferable for IOP assessment in the early phase after SMILE.Trial registrationCurrent Controlled Trials ChiCTRONRC13003114. Retrospectively registered 17 March 2013

Évaluation des propriétés biomécaniques de la cornée de patients glaucomateux et témoins par la technologie dynamique Scheimpflug de visualisation cornéenne

To compare corneal biomechanical properties measured with Corvis Scheimpflug technology (Corvis ST) between a group of patients with chronic open-angle glaucoma and a group of control patients. Prospective observational case-control study. This study enrolled 56 right eyes of 56 patients (G1 [chronic open-angle glaucoma] n=37/G2 [control] n=19). Each patient underwent measurement of corneal biomechanical properties by dynamic Scheimpflug (Corvis ST) camera and the Ocular Response Analyser (ORA), then a measurement of intraocular pressure (IOP) by Goldmann applanation tonometry (GAT) and measurement of central corneal thickness (CCT) by optical coherence tomography during the same visit, by a single clinician. The parameters determined by Corvis ST are: Corvis IOP (IOP Corvis ST), the corneal deformation amplitude (CDA), corneal velocity, the time at highest concavity (TIME CONCAV), the lengths of applanation and their corresponding applanation time. Those studied by ORA are: compensated IOP (IOPcc), non-compensated IOL (IOPg), corneal hysteresis (CH) and corneal resistance factor (CRF). IOP measured on all patients by Corvis ST was positively correlated to GAT (Spearman r=0.569, P<0.001) and PIOcc (Spearman r=0.531, P<0.001). After adjusting for age effect, CCT and GAT, the CDA was significantly lower in G1 than in G2, respectively 1.10 ± 0.12 mm and 1.15 ± 0.10mm (P<0.001). The TIME CONCAV is significantly shorter in G1 than in G2, respectively 16.88 ± 0.63 ms and 17.11 ± 0.29 ms, P=0.029. CH was significantly lower in G1 (G1: 9.58 ± 1.94 than G2: 10.89 ± 2.16, P=0.026). This study showed differences in corneal biomechanical properties between glaucoma and control patients. The cornea of glaucoma patients appears less deformable.

Changes in corneal deformation parameters after lenticule creation and extraction during small incision lenticule extraction (SMILE) procedure.

PurposeTo investigate the effects of lenticule creation and subsequent corneal lenticule extraction on corneal deformation parameters during small incision lenticule extraction (SMILE) procedure.Materials and MethodsIn this prospective study, 18 eyes of 10 patients (27.90±7.11 years, −5.64±2.45 diopters) scheduled for SMILE procedure were enrolled. Changes in the corneal deformation parameters, including deformation amplitude (DA), applanation time(AT1 and AT2), applanation length(AL1 and AL2), corneal velocity(CV1 and CV2), peak distance(P.Dist.), radius and intraocular pressure values were measured preoperatively, immediately after lenticule creation and subsequent to corneal lenticule extraction in all eyes with the Corvis Scheimpflug Technology (Corvis ST, OCULUS, Wetzlar, Germany). Repeated measures analysis of variance (ANOVA) with bonferroni-adjusted post hoc comparisons was performed to investigate changes following each step of the procedure.ResultsAll surgical procedures were uneventful. A significant difference was detected among the three time points (pre-operation, post-lenticule creation and post lenticule extraction) for AT1 (P<0.001), AT2 (P = 0.001), DA(P<0.001), and IOP(P = 0.002). Bonferroni-adjusted post hoc comparisons indicated that there was no significant change in AT1, AT2, DA, or IOP after lenticule creation (post hoc P>0.05), but there was a significant change in these parameters following subsequent corneal lenticule extraction (post hoc P<0.01), when compared to values obtained pre-operatively. The scheimpflug camera of the Corvis ST demonstrated the intralamellar small gas bubbles formed from the vaporisation of tissue after lenticule creation and a gray zone was observed between the cap and the residual stromal bed after lenticule extraction.ConclusionsThere is a significant change in corneal deformation parameters following SMILE procedure. The changes may be caused predominantly by stromal lenticule extraction, while lenticule creation with femtosecond laser may not have an obvious effect on corneal deformation properties.

Evaluation of a novel Scheimpflug-based non-contact tonometer in healthy subjects and patients with ocular hypertension and glaucoma

BackgroundTo evaluate the agreement of intraocular pressure (IOP) and central corneal thickness (CCT) measurements obtained with the non-contact tonometer Corvis Scheimpflug Technology (Corvis ST, OCULUS, Wetzlar, Germany) versus Goldmann applanation...