Scheimpflug Imaging of the Anterior Eye Segment during Standardized Accommodation Stimulation in Patients with Emmetropia, Myopia and Hypermetropia

Understanding of the biomechanics of the accommodative apparatus in the eyes with different refraction is important for solving the problems of theoretical and practical ophthalmology. Purpose: To determine the changes of anterior eye segment dimensions during accommodation response in normal eyes and in patients with myopia, hypermetropia. Methods and Material: 116 eyes (56 patients aged from 18 to 30 years, refraction from -2.0 to + 2.0 D) were examined. All the patients underwent a full ophthalmological examination. The ocular anterior segment was imaged using a rotational Scheimpflug camera Pentacam HR (Oculus, Wetzlar, Germany) under non- and 3.0 D of accommodative demands. The statistical data were represented as the mean value ± standard deviation (M ± SD). The Shapiro-Wilk test was used to assess the normality distribution. Wilcoxon test was used for comparison. Results: Results showed an increase in the optical density of the crystalline lens, a pupil diameter decrease and changing of the iris profile during accommodation in all patients. An increase in the total corneal aberrations and decrease in the corneal spherical aberration were revealed only in emmetropic eyes. Conclusions: The accommodative response is a multicomponent process. Scheimpflug visualization revealed the differences in the accommodative response in normal and ametropic eyes.

Monitoring of central corneal thickness after phacoemulsification—comparison of statical and rotating Scheimpflug pachymetry,and spectral-domain OCT

AIM:To explore the possibility of deploying three contactless devices(static and rotating Scheimpflug technology,spectral domain optical coherence tomography)for measuring central corneal thickness(CCT)in preoperative and postoperative examinations of cataract patients.METHODS:Totally 72 patients who had undergone surgery without complications were selected.The CCT was measured prior to the operation,as well as on the first,5th-7th and 28th day following the operation using the Nidek NT 530-P,Sirius?,and Topcon OCT-2000 devices.RESULTS:A significant postoperative increase and subsequent decrease in CCT was identified with all three devices.The correlations were highly significant and thus reflect a very good degree of comparability at all times with the exception of the rotating Scheimpflug camera.The postoperative results from the latter differed significantly from the other devices.The correlations were Sirius/Topcon(P=0.010)and Sirius/Nidek(P<0.0005).No statistically significant difference could be identified in the comparison between Topcon and Nidek(P=0.056).CONCLUSION:All three devices are suitable for postoperative monitoring of CCT.The measurement results are only comparable to a limited extent and not interchangeable in the course of treating a single patient.This is due to the different imaging technology used in the devices and the resulting modalities for conducting the measurements.

Fourier analysis of corneal Scheimpflug imaging:clinical use in keratoconus

AIM:To evaluate the clinical use of Fourier analysis of videokeratography data in the diagnosis and follow-up of keratoconus(KC).METHODS:We conducted a chart review of consecutive patients presented to our cornea clinic.A team of two experienced cornea specialists divided the patients into three groups:normal cornea,forme fruste KC(FFKC),and clinical KC.The exclusion criteria were a history of previous ocular surgery,any accompanying corneal pathology other than KC,high myopia(>6.00 diopters),amblyopia,pregnancy,breastfeeding,or any current autoimmune disease.The data of Fourier series harmonic analysis were evaluated for their diagnostic capacity using the receiver operating characteristic(ROC)curve.A binary logistic regression analysis was also conducted to construct a diagnostic model.A total of 259 eyes showed progression in the clinical KC group and underwent a combination of accelerated corneal collagen cross-linking and topographyguided customized treatment with an excimer laser.RESULTS:The study included 1262 eyes(618 normal,530 KC,and 114 FFKC)of 1262 patients.We observed that maximum decentration(MaxDec)was almost as good as maximum keratometry(Kmax)in detecting progressive KC.The area under the curve(AUC)was 0.95 for KC[95%confidence interval(CI):0.93-0.96]and 0.84 for FFKC(95%CI:0.79-0.88).Higher predictive accuracy was obtained using a model combining the spherical component,MaxDec,irregularity,and regular astigmatism in the center of the cornea(AUC:0.97;sensitivity:89%,and specificity:96%).CONCLUSION:Decentration,Kmax,and posterior radii of curvatures from a 3.0-mm optical zone centered on the thinnest point of the cornea provide the highest accuracy with low reproducibility of Kmax.

Anterior segment parameters associated with extramuscular manifestations in polymyositis and dermatomyositis

AIM:To evaluate detailed anterior segment parameters of patients with idiopathic inflammatory myopathies(IIM),including polymyositis(PM),and dermatomyositis(DM),and to clarify the associations between these data and clinical variables of IIM.METHODS:Totally 57 PM,41 DM patients and 62 controls were enrolled in this cross-sectional,observational,case-control study.All study participants underwent Pentacam evaluation.Laboratory investigations consisted of different antibody assays,while extramuscular clinical assessments included Raynaud’s phenomenon,dysphagia,interstitial lung disease,arthritis/arthralgia,and weight loss.Objective signs and subjective symptoms of dry eye disease(DED)were also evaluated.RESULTS:All pachymetric parameters[center,apex,thinnest and maximal keratometry(Kmax)]and corneal volume(CV)of both sides of PM patients proved to be significantly lower.Some pachymetric data were also noticed as significantly decreased compared to those of controls.Several significant differences were traced between anterior segment values and extramuscular manifestations of myositis,largely in case of arthritis/arthralgia and weight loss,whereas associations between anterior segment parameters and antibodies were weak.Objective clinical tests of DED were also significantly decreased in IIM patients.CONCLUSION:The results suggest that all IIM patients have thinner corneas compared with those of controls,and decreased corneal parameters are significantly associated with the occurrence of some extramuscular manifestations.In addition,IIM patients tend to develop objective signs of DED.

The precision and agreement of corneal thickness and keratometry measurements with SS-OCT versus Scheimpflug imaging

Purpose:To assess the repeatability and reproducibility of swept-source optical coherence tomography(SS-OCT)and Scheimpflug system and evaluate the agreement between the two systems in measuring multiple corneal regions in children.Methods:Pachymetric and keratometric maps for both systems were evaluated.Central,midperipheral and peripheral corneal thickness(CT),keratometry and astigmatism power vectors were recorded.The three outcomes yielded by the same observer were used to assess intraobserver repeatability.The differences in the mean values provided by each observer were used to evaluate interobserver reproducibility.Within-subject standard deviation,test-retest repeatability(TRT)and coefficient of variation(CoV)were used to analyze the intraobserver repeatability and interobserver reproducibility.Paired T-test and Bland-Altman were used to appraise interdevice agreement.Results:Seventy-eight eyes of 78 children were included.The CoV was≤2.12 and 1.10%,respectively,for repeatability and reproducibility.TRT and CoV were lower for central and paracentral CT measurements than for peripheral measurements.The SS-OCT device generated higher precision when acquiring CT data,whereas Scheimpflug system showed higher reliability when measuring corneal keratometry.Although the CT readings measured using SS-OCT were significantly thinner than Scheimpflug device(P<0.001),the central and thinnest CT values were still of high agreement.The interdevice agreement of keratometry measurement was high for the central corneal region and moderate for the paracentral and peripheral areas.Conclusions:The precision of CT measurements by SS-OCT was higher,while the reliability of keratometry measurements by the Scheimpflug system was higher in children.Apart from the measured values in the central corneal region,the thickness and keratometry readings should not be considered interchangeable between the two systems.

The precision and agreement of corneal thickness and keratometry measurements with SS-OCT versus Scheimpflug imaging

Purpose:To assess the repeatability and reproducibility of swept-source optical coherence tomography(SS-OCT)and Scheimpflug system and evaluate the agreement between the two systems in measuring multiple corneal regions in children.Methods:Pachymetric and keratometric maps for both systems were evaluated.Central,midperipheral and peripheral corneal thickness(CT),keratometry and astigmatism power vectors were recorded.The three outcomes yielded by the same observer were used to assess intraobserver repeatability.The differences in the mean values provided by each observer were used to evaluate interobserver reproducibility.Within-subject standard deviation,test-retest repeatability(TRT)and coefficient of variation(CoV)were used to analyze the intraobserver repeatability and interobserver reproducibility.Paired T-test and Bland-Altman were used to appraise interdevice agreement.Results:Seventy-eight eyes of 78 children were included.The CoV was≤2.12 and 1.10%,respectively,for repeatability and reproducibility.TRT and CoV were lower for central and paracentral CT measurements than for peripheral measurements.The SS-OCT device generated higher precision when acquiring CT data,whereas Scheimpflug system showed higher reliability when measuring corneal keratometry.Although the CT readings measured using SS-OCT were significantly thinner than Scheimpflug device(P<0.001),the central and thinnest CT values were still of high agreement.The interdevice agreement of keratometry measurement was high for the central corneal region and moderate for the paracentral and peripheral areas.Conclusions:The precision of CT measurements by SS-OCT was higher,while the reliability of keratometry measurements by the Scheimpflug system was higher in children.Apart from the measured values in the central corneal region,the thickness and keratometry readings should not be considered interchangeable between the two systems.