[Biometry of the anterior segment using optical coherence tomography : Evaluation of different devices and analysis programs]

Slit-lamp-adapted fourier-domain OCT for anterior and posterior segments: preliminary results and comparison to time-domain OCT

PURPOSE

To evaluate the diagnostic potential of a slit-lamp (SL)-adapted Fourier-domain (= spectral radar, SR) optical coherence tomography (OCT)-SL-SR-OCT-instrument as an in vivo imaging device for use in examinations of the anterior and posterior segments.

MATERIALS AND METHODS

In a pilot study, 88 eyes from 70 healthy volunteers and patients were examined using a prototype Fourier-domain SL-SR-OCT system. Results were compared to those from the following commercially available systems: the 1310-nm SL-OCT (Heidelberg Engineering, Heidelberg, Germany) for anterior segment and the Stratus OCT (Zeiss Meditec, Jena, Germany) for posterior segment imaging. Our SL-SR-OCT provides 1025 axial scans, 5000 Hz line-scan frequency, scan length of up to 8 mm, axial depth in air of 3.5 mm, and resolution of 9 mum. For posterior visualization, a hand-held 78-diopter ophthalmoscopic lens was used.

RESULTS

Our SL-SR-OCT system allowed simultaneous scanning with direct biomicroscopic and SL imaging of anterior and posterior segment structures. Anatomical structures and pathological changes were displayed with high resolution and excellent contrast. Measurements of corneal and retinal thickness were possible. In comparison to images obtained by the SL-OCT, our SL-SR-OCT boasted a higher resolution, thus providing more clinically relevant details of the corneal epithelium, internal structure of filtering blebs, etc. Complete imaging of the chamber angle was limited, however, due to the backscattering properties of the sclera at 830 nm. For posterior segment imaging, excellent delineation of the macula and optic nerve head details, with a distinct portrayal of macular pathology and retinal edema, was possible with SL-SR-OCT.

CONCLUSION

SL-SR-OCT enables detailed imaging of physiological and pathological anterior and posterior segment structures. As a multi-purpose device, it offers a wide spectrum of applications, with high-quality OCT-imaging, in a comfortable setting without the need to move the patient.

Intra-examiner repeatability and agreement of corneal pachymetry map measurement by time-domain and Fourier-domain optical coherence tomography

BACKGROUND

To assess the intra-examiner repeatability and agreement of corneal pachymetry maps measured by time-domain (Visante OCT) and Fourier-domain optical coherence tomography (RTVue OCT).

METHODS

This observational cross-sectional study enrolled 72 eyes from 72 volunteers. Only one eye of each patient was chosen randomly to receive repeated scanning with both devices by the same examiner, in order to test the intra-observer repeatability. The first scan by each device from all enrolled eyes was used to analyze the difference and agreement between the two devices. The agreement between the two devices was analyzed by the Bland-Altman method. Intra-observer repeatability of each OCT device was analyzed by intra-class correlation (ICC).

RESULTS

The mean corneal thickness of the central 2 mm zone was 524.3 ± 35.7 µm and 525.4 ± 35.3 µm by the Visante OCT and the RTVue OCT respectively (p = 0.089). The intra-observer repeatability of the RTVue OCT (ICC = 0.994) was superior to that of the Visante OCT (ICC = 0.989) in the central 2 mm zone. However, the intra-observer repeatability of the RTVue OCT in the pericentral 2 to 5 mm zone was not superior to that of the Visante OCT. Both OCT devices had similar repeatability in the pericentral 2 to 5 mm zone [ICC of the Visante OCT = 0.991; 95% confidence interval (CI) 0.986-0.995), ICC of the RTVue OCT = 0.991; 95% CI 0.985-0.994)).

CONCLUSIONS

The difference in CCT measurement by the Visante OCT and the RTVue OCT is probably too small to influence clinical decision making for refractive surgery and glaucoma management. The RTVue OCT demonstrated better intra-observer repeatability in the central 2 mm zone, which probably was related to its rapid image acquisition capability.