Anterior chamber width measurement by high-speed optical coherence tomography

Abstract

Objective: To measure anterior chamber (AC) width and other dimensions relevant to the sizing of phakic intraocular lenses (IOLs) with a high-speed optical coherence tomography (OCT) system. Design:Cross-sectional observational study. Participants: Both eyes of 20 normal volunteers.Methods: A novel high-speed (4000 axial scans/second) OCT prototype was developed for anterior segment scanning. The system uses long wavelength (1310 nm) for deeper angle penetration, rectangular scanning for undistorted imaging, and short image acquisition time (0.125 seconds) to reduce motion error. Three horizontal cross-sectional OCT images (15.5 mm wide and 6 mm deep) of the anterior segment were obtained from each eye with real-time image display to guide centration on the corneal apex. Image processing software was developed to correct for image warping resulting from index transitions. Anterior chamber dimensions were measured using computer calipers by 3 expert raters (ophthalmologists). Analysis of variance was used to determine interrater, interimage, right versus left eye, and intersubject standard deviation (SD) of OCT measurements. Main Outcome Measures:Anterior chamber width (recess to recess), AC depth, and crystalline lens vault as measured by OCT; external white-to-white (WTW) corneal diameter (CD) as measured by Holladay-Godwin gauge. Results:The mean AC width was 12.53±0.47 mm (intereye SD), and the mean corneal diameter was 11.78±0.57 mm. Optical coherence tomography measurement of AC width has good repeatability from image to image (SD, 0.134 mm), but there was significant difference between raters (SD, 0.215 mm). Estimation of AC width from WTW CD by linear regression was relatively inaccurate (residual SD, 0.41 mm). The mean AC depth was 2.99±0.323 mm (intereye SD), with

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

“…10 Although it is likely that age will affect the parameters, some interesting comparisons can still be made between these normal adult values and our study of children with MPS. 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.…”

“…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).…”

“…One of the earliest studies of AS-OCT, with measurements made manually using computer callipers, found a mean anterior chamber width of 12.53 ± 0.47 mm, mean ACD of 2.99 ± 0.323 mm, and mean CLR of 0.39 ± 0.27 mm. 5 A prospective study of 497 normal, phakic eyes of adults aged 450 years compared Visante AS-OCT, IOLMaster (Carl Zeiss Meditec AG), and scanning peripheral anterior chamber depth analyser (SPAC, Takagi, Japan) measurements, and the AS-OCT mean ACD was 3.14 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.…”

Comparison of Visante and slit-lamp anterior segment optical coherence tomography in imaging the anterior chamber angle

“…After acquisition, the scanned images were processed using customised software ('dewarping' software), which compensates for index of refraction transition at the air-tear interface and for the different group indices in air, cornea, and aqueous to correct the physical dimensions of the images. 9 Of note, a low-intensity narrow light beam from the slit-lamp was kept on during the SL-OCT scan acquisition to facilitate gross adjustment of the OCT scanning beam location, as the scanning beam scans structures along the same line as the slit-lamp beam.…”

Avaliação de lente intra-ocular fácica para a correção da presbiopia

“…A maioria das complicações encontradas como a ovalização pupilar, a rotação da lente, a queixa de diplopia e as queixas subjetivas da visão de halos relacionam-se à escolha do diâ-metro inadequado da lente. Novos aparelhos de medidas utilizando novas tecnologias parecem estar mais acurados nas mensurações da biometria da câmara anterior (16)(17) , mas novos estudos são necessários para sua validação.…”