The utility of measures of anterior segment parameters of a Pentacam Scheimpflug tomographer in discriminating high myopic astigmatism from keratoconus

The study aimed to evaluate and compare anterior segment parameters between keratoconic eyes and eyes with high myopic astigmatism using Pentacam Scheimpflug tomography. This was a retrospective cross-sectional study that included sixty keratoconic eyes (thirty-two persons) and seventy-three eyes (forty-six persons) with high myopic astigmatism with mean ages 24.72 ± 11.65years and 26.60 ± 10.69years, respectively. Twenty-three parameters from the topographic map and fifteen parameters from the Belin-Ambrosió enhanced ectasia display map of the printouts of a Scheimpflug principle-based Pentacam tomographer were evaluated for their diagnostic accuracy using Receiver Operating Characteristic (ROC) curve. All parameters except cornea volume, anterior chamber volume, and anterior chamber angle indicated a significant difference between high myopic astigmatism and keratoconic eyes. The area under the receiver operating characteristic (AUROC) of eighteen Pentacam parameters was excellent (0.9–1.0) in discriminating keratoconus from high myopic astigmatism, out of which four {anterior minimum sagittal curvature (ant. Rmin), posterior minimum sagittal curvature (post. Rmin), maximum Ambrosió relational thickness (ART max) and total deviation value (D)} indicated excellent (>90%) sensitivity and specificity in addition to the excellent AUROC values. Topographic and Belin-Ambrosió enhanced ectasia display (BAD) maps of a Scheimpflug principle-based Pentacam tomographer are useful in enhancing the diagnosis of keratoconus and may also provide valuable information in effectively screening for keratoconus cases among refractive surgery candidates with high myopic astigmatism.

Biometric Indicators of Anterior Segment Parameters Before and After Laser Peripheral Iridotomy by Swept-Source Optical Coherent Tomography

Background Primary angle closure glaucoma (PACG) is the most common type of glaucoma in China. Laser peripheral iridotomy (LPI) is the primary choice to treat PAC. We aim to evaluate the changes and to find the biometric indicators of anterior segment parameters before and after laser peripheral iridotomy (LPI) in primary angle closure (PAC) eyes using swept-source optical coherent tomography (OCT). Methods LPI was performed in 52 PAC eyes of 28 participants. The change of intraocular pressure and anterior segment parameters, including angle opening distance (AOD500), AOD500 area, trabecular iris space area (TISA500), TISA500 volume, trabecular iris angle (TIA500), iridotrabecular contact (ITC) index, ITC area, anterior chamber volume (ACV), anterior chamber depth (ACD), lens vault (LV) and lens thickness (LT) before and 1 week after LPI were measured by Tomey CASIA2 anterior segment OCT. We also estimate and analyze potential contributing factors possibly affecting the change of anterior chamber angle parameters. Results No post-laser complications were found. The LV and LT did not change significantly 1 week after LPI. AOD500, AOD500 area, TISA500, TISA500 volume, TIA500, ACV and ACD increased significantly after LPI. There was significant decrease in ITC index and ITC area. LT was positively correlated to the change of ITC index (r=0.411, p=0.002) and ITC area (r=0.384, p=0.005). ACD was negatively correlated to the change of ITC index (r=0.292, p=0.036). Conclusions The anterior segment architecture significantly changed after LPI in PAC spectrum eyes. Crystalline lens measurements remained unchanged before and after LPI. AS-OCT can be used to follow anterior chamber parameter changes in PAC spectrum eyes. Pre-treatment LT and ACD affect the therapeutic effect of LPI.

Association of peripheral anterior synechiae with anterior segment parameters in eyes with primary angle closure glaucoma

To investigate the association of peripheral anterior synechiae (PAS) with intraocular pressure (IOP) and anterior-segment parameters in subjects with primary angle-closure glaucoma (PACG). A total of 267 subjects with PACG were recruited and underwent gonioscopy and anterior-segment optical coherence tomography (ASOCT). Customized software was used to measure ASOCT parameters, including angle opening distance (AOD750) and trabecular-iris-space-area (TISA750) at 750 µm from the scleral spur, anterior chamber depth, width, area and volume (ACD, ACW, ACA, ACV), iris thickness (IT750), iris area (IAREA), and lens vault (LV). Presenting IOP was defined as the first IOP reading before the initiation of IOP-lowering treatment. The mean age of the 267 subjects was 67.0 ± 8.9 years, 140 (52.4%) were male, and 246 (92.1%) were of Chinese ethnicity. PAS was present in 122 (45.7%) subjects, and was most frequently found in the superior quadrant (79.5%). Subjects with PAS had greater presenting IOP (28.7 ± 12.9 vs 22.4 ± 9.7 mmHg, p < 0.001), narrower AOD750 (p < 0.001), smaller TISA750 (p < 0.001), ACD (p = 0.04), ACA (p = 0.02), ACV (p = 0.01) and larger LV (p = 0.01) compared to PACG eyes without PAS. No significant differences were noted for iris parameters. A multivariate logistic regression analysis showed that higher presenting IOP (β = 0.20, p < 0.001), worse visual field mean deviation (β = − 0.20, p = 0.01) and narrower AOD750 (β = − 0.25, p = 0.03) were the only parameters that significantly correlated with the extent of PAS in clock hours. Almost one-half of the subjects with PACG demonstrated PAS; these eyes were associated with higher presenting IOP, smaller anterior segment dimensions and more severe disease.

Analysis of Anterior Segment Parameters and Wavefront Aberrations of the Myopic Eyes Using Two Scheimpflug-based Devices: The Pentacam vs Sirius

Purpose: To measurements, comparisons, and agreement of the anterior segment parameters and wavefront aberrations of the myopic eyes through the Pentacam and Sirius tomography systems. Methods: The Pentacam and Sirius were used to measure the corneal anterior segment tomography and wavefront aberrations of the myopic eyes with a mean age of 25.66±3.77 (range from 19 to 31 years).Various parameters such as the anterior keratometric reading of the flattest meridian K1, anterior K2, thinnest corneal thickness, corneal surface asphericity Q-value, anterior chamber depth, Root mean square (RMS) of higher-order aberrations, RMS of lower-order aberrations, and RMS of total aberrations were analyzed. Also, the agreement between the Pentacam and Sirius was assessed by calculating 95% limits of agreement and plotting the Bland–Altman graphs.Results: One eye of 99 myopic subjects (49 men, 50 women) aged 19 to 31 years was randomized and evaluated. All measured parameters of the Pentacam and Sirius tomography systems were statistically significant (p<0.001) in comparison with each other expect the mean values of K1, K2, and thinnest corneal thickness (p>0.05). The thinnest corneal thickness findings showed the poorest agreement (95 %limit of agreement from -8.71 to 24.21) and the greatest difference (mean difference: 7.75).Conclusions: The differences between the gained measurement results of the devices suggests that they should not be used interchangeably for corneal tomography imaging in clinical practice and surgery decision.