[Biometry of the anterior segment using optical coherence tomography : Evaluation of different devices and analysis programs].
BACKGROUND
Digital visualisation of the anterior eye segment is becoming more and more important. Two commercially available optical coherence tomographs (OCTs) - Visante OCT (Carl-Zeiss Meditec Jena) and Slit Lamp-OCT (SL-OCT. Heidelberg Engineering) - were evaluated. Additionally, a manual and a semiautomatic analysis mode for the anterior segment biometry were compared using the SL-OCT.


METHODS
Fifty eyes were examined by three ophthalmologists with complete eye status in a standardised fashion. Three anterior segment scans (horizontal and vertical) were performed using the Visante OCT and the SL-OCT. The manual integrated analysis mode of the Visante OCT was used. The best centred SL-OCT scan was analysed with a manual (EyelabGlobal/4Optics) and a semiautomatic procedure (HEYEX). Central corneal thickness (CCT), anterior chamber depth (ACD), pupillary diameter (PD) and chamber angle-angle distance (CAAD) were compared.


RESULTS
Comparison of Visante OCT and SL-OCT: The horizontal CAAD was 11.65+/-0.47 mm for the Visante-OCT and 12.0+/-0.57 mm for the SL-OCT (p=0,002), vertical scans were comparable in 10 eyes only. The CCT was 568+/-61 microm with the Visante-OCT and 581+/-48 microm with the SL-OCT (n=35, p=0.03) in horizontal scans and 565+/-62 microm with the Visante-OCT and 568+/-51 microm with the SL-OCT in vertical scans (n=27, not significant). Deviation of the two measurement methods varied between -54.7 and 80.8 microm in horizontal scans and between -84.9 and 91.1 microm in vertical scans from the mean difference of the two methods. Comparison of the analysis programs: Horizontal scans: Manual analysis correlated with semiautomatic analysis in CCT as 581+/-51 microm vs. 572+/-53 microm (r=0.903), ACD 2.89+/-0.74 mm vs. 2.08+/-0.72 mm (r=0.98), PD 5.22+/-2.12 mm vs. 5.14+/-1.91 mm (r=0.917) and CAAD 11.59+/-1.02 mm vs. 11.79+/-0.6 mm (r=0.47). The manual and a semiautomatic analysis modes for CCT and ACD differed significantly (p<0.026). Vertical scan: Manual versus semiautomatic analysis modes correlated in CCT as 578+/-65 microm vs. 573+/-63 microm (r=0.593), ACD with 3.04+/-0.83 mm vs. 3.03+/-0.75 mm (r=0.92), PD with 5.28+/-1.99 mm vs. 5.45+/-2.00 mm (r=0.899) and CAAD with 11.75+/-0.66 mm vs. 11.82+/-0.6 mm (r=0.537).


CONCLUSIONS
A near complete investigation of the cornea-anterior-chamber-iris segment is provided by the horizontal scan compared with the vertical scan. The noncontact OCT method is an easily handled tool for visualisation and biometry of the anterior eye segment. The investigated OCTs show a limited comparability. A complete analysis was possible in all eyes with the EyelabGlobal system in contrast to the HEYEX analysis software. Both analysis programs provided comparable measurements of the anterior eye segment. The semiautomatic biometrical mode may reduce the analysis time in qualitative excellent and well-centred scans to 10%.
Viestenz
A
A
Augenklinik mit Poliklinik der Otto-von-Guericke-Universität, Magdeburg, Deutschland. anja.viestenz@med.ovgu.de
Vogt
S
S
Langenbucher
A
A
Walter
S
S
Behrens-Baumann
W
W
D000368:Aged; D000465:Algorithms; D001699:Biometry / Q000295:instrumentation* / Q000379:methods*; D019781:Corneal Topography / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012984:Software; D041623:Tomography, Optical Coherence / Q000295:instrumentation* / Q000379:methods*