Comparison of Anterior Segment Optical Tomography Parameters Measured Using a Semi-Automatic Software to Standard Clinical Instruments

Abstract

ObjectiveTo compare anterior segment parameters measured using a semi-automatic software (Zhongshan Angle Assessment Program, ZAP) applied to anterior segment optical coherence tomography (AS-OCT) images, with commonly used instruments.MethodsCross-sectional study of a total of 1069 subjects (1069 eyes) from three population-based studies of adults aged 40–80 years. All subjects underwent AS-OCT imaging and ZAP software was applied to determine anterior chamber depth (ACD), central corneal thickness (CCT), anterior and keratometry (K) – readings. These were compared to auto-refraction, keratometry and ocular biometry measured using an IOLMaster, ultrasound pachymeter and auto-refractor respectively. Agreements between AS-OCT (ZAP) and clinical instrument modalities were described using Bland-Altman, 95% limits of agreement (LOA).ResultsThe mean age of our subjects was 56.9±9.5 years and 50.9% were male. The mean AS-OCT (ZAP) parameters of our study cohort were: ACD 3.29±0.35 mm, CCT 560.75±35.07 µm; K-reading 46.79±2.72 D. There was good agreement between the measurements from ZAP analysis and each instrument and no violations in the assumptions of the LOA; albeit with a systematic bias for each comparison: AS-OCT consistently measured a deeper ACD compared to IOLMaster (95% LOA −0.24, 0.55); and a thicker CCT for the AS-OCT compared to ultrasound pachymetry (16.8±0.53 µm 95% LOA −17.3, 50.8). AS-OCT had good agreement with auto-refractor with at least 95% of the measurements within the prediction interval (P value <0.001).ConclusionThis study demonstrates that there is good agreement between the measurements from the AS-OCT (ZAP) and conventional tools. However, small systematic biases remain that suggest that these measurement tools may not be interchanged.

Anterior segment OCT imaging in mucopolysaccharidoses type I, II, and VI

“…For example, the mean ATA values in MPS I (12.55 mm) and MPS II (12.53 mm) were very similar to the mean anterior chamber width found by Goldsmith et al, 5 whereas in MPS VI the value was significantly smaller (11.34 mm). Similarly, previously published values for mean ACD [5][6][7] are much greater than those in our MPS VI patients, but only slightly greater than in MPS I and II. The mean CLR found by Goldsmith et al 5 was roughly equivalent to the mean values in MPS I and II (449 and 380 mm, respectively), but much lower than in MPS VI (737 mm).…”

“…6 A further AS-OCT study of 1069 normal eyes in Singaporean adults (mean age 56.9 ± 9.5 years) found mean ACD to be 3.29 ± 0.35 mm. 7 A Canadian study of 40 normal, adult eyes found the mean nasal angle to be 39.32±3.071. 8 Work conducted in Turkey on 40 normal eyes, using Visante OCT, found the mean nasal and temporal angles to be 31.2±8.71 and 32.1±8.51, respectively.…”

En face optical coherence tomography angiography for corneal neovascularisation

“…The ‘en face’ mode produces C-scans that are orientated to the frontal plane and gives transverse slices of a corneal lesion and neovascularisation—which is more intuitive to untrained operators, as opposed to the traditional cross-sectional OCT ‘B-scans’ that resemble histology slides, and are more useful for studying anterior segment anatomy 26 27. The coronal reconstruction allows for an instant overview of the corneal pathology and changes to the length, calibre and area of corneal neovascularisation, which was previously not possible with B-scan OCT views 28.…”

Optical Coherence Tomography Angiography for Anterior Segment Vasculature Imaging

“…1 It also has been established as a useful tool in providing rapid, noncontact evaluation of the cornea and anterior segment. 2,3 Further technological developments also have increased the imaging capabilities of OCT in terms of speed, image resolution, and, more recently, evaluation of vascular flow. 4 These new OCT imaging techniques have been described for noninvasive evaluation of vessels within the retina and optic disc.…”