Repeatability and agreement of white-to-white measurements between slit-scanning tomography, infrared biometry, dual rotating Scheimpflug camera/Placido disc tomography, and swept source anterior segment optical coherence tomography

Purpose To assess the agreement and repeatability of horizontal visible iris diameter (HVID) or white-to-white (WTW) measurements between four imaging modalities; combination slit scanning elevation/Placido tomography, infrared biometry, dual rotating scheimpflug camera/Placido tomography, and swept source anterior segment optical coherence tomography (AS-OCT). Methods A prospective study of 35 right eyes of healthy volunteers were evaluated using the Orbscan IIz, IOL Master 700, Galilei G2, and DRI Triton OCT devices. The inter-device agreement and repeatability of HVID/WTW measurements for each device were analysed. Results Mean HVID/WTW values obtained by the Orbscan IIz, IOL Master 700, Galilei G2 and DRI Triton OCT were 11.77 ± 0.40 mm, 12.40 ± 0.43 mm, 12.25 ± 0.42 mm, and 12.42 ± 0.47 mm, respectively. All pairwise comparisons revealed statistically significant differences in mean HVID/WTW measurements (p = <0.01) except for the IOL Master 700—DRI OCT Triton pair (p = 0.56). Mean differences showed that the DRI Triton OCT produced the highest HVID/WTW values, followed by the IOL Master 700, Galilei G2 and Orbscan IIz, respectively. The limits of agreement were large on all device pairs. There was high repeatability for all devices (ICC ≥ 0.980). The highest repeatability was seen in the Galilei G2 (ICC = 0.995) and lowest in the Orbscan IIz (ICC = 0.980). Conclusions The four devices exhibit high repeatability, but should not be used interchangeably for HVID/WTW measurements in clinical practice.

Visualization and assessment of the anterior surface of the cornea by corneal topography (Part II)

Goal. To introduce ophthalmologists and optometrists to the basics of corneal topography. Corneal topography is the main method for assessing corneal surface regularity, the violation of which leads to a deterioration in its refractive properties and a decrease in the quality of vision. The first part of the workshop (The EYE GLAZ. 2020 (22), № 2) presented the main types of topography maps and keratometry data. In the second part, considerations are made regarding mastering the skills of capturing high-quality images and choice of color maps for analysis. Topography patterns as well as topographic signs of keratoconus are also discussed. Conclusion. Placido-based corneal topographers are a useful tool for evaluating the anterior corneal surface, fitting contact lenses and diagnosing keratoconus. Slit-scanning topographers, additionally, are capable of corneal pachymetry and analyzing the posterior surface of the cornea, which allows for carrying out a more detailed assessment and diagnosing keratoconus at preclinical stage.

Crystalline lens imaging during accommodation with a slit-scanning tomography system: preliminary results

A slit-scanning tomography system previously developed in the Centre of Physics of University of Minho allows to capture images of the eye and posteriorly calculus of the biometric (thickness and curvature) and optical (wavefront aberrations) properties of the corneal and crystalline lens surfaces. It is intended to optimise the system for an accurate computing of these properties of the crystalline lens in the relaxed state and during ocular accommodation. In this study, preliminary experimental results of the crystalline lens imaging of a subject during accommodation are presented.

Origin of Hot Bubble in NGC 6822 Hubble V Star-Forming Region

We observed a bright H II complex, Hubble V in NGC 6822, using the high-resolution near-infrared spectrograph IGRINS (R = 45,000) attached on the 2.7 m telescope at the McDonald Observatory. We carried out a spectral mapping over a 15″ × 18″ region in the H and K bands using a slit-scanning technique. The emission lines Brγ and He i from ionized regions as well as molecular hydrogen lines from photo-dissociation regions (PDRs), were detected. We show three-dimensional maps of the emission lines and discuss the possibility of an expanding hot bubble structure within which many ionized components are around the central stellar cluster.