medwireNews: Spanish researchers have validated the use of two instruments for determining anterior chamber depth in teenagers and published normative data for the techniques.
Writing in the Journal of Optometry, they say that partial coherence interferometry and anterior segment optical coherence tomography show good agreement overall, but that small differences between the instruments ought to be taken into account.
Measurement of anterior chamber depth is important for calculating the power of intraocular lenses as well as screening for glaucoma risk. The most common method is ultrasound biometry, but this can give false results due to indentation of the cornea.
To evaluate alternative methods, Inmaculada Bueno-Gimenoa (University of Valencia) and colleagues studied 68 eyes of 34 healthy emmetropic patients (18 girls). They were aged between 13 and 17 years, with a mean age of 14.45 years. All patients had anterior chamber depth measured using two different non-contact optical devices.
The first was the "IOLMaster" technique, which uses the partial coherence interferometry principle to measure the axial length. The anterior chamber depth is determined by calculating the distance along the visual axis from the corneal epithelium to the anterior crystalline lens.
The second was the anterior segment optical coherence tomography technique using the "Visante-OCT." This is a non-contact, high-resolution tomographic and biomicroscopic device that provides cross-sectional images of the anterior segment of the eye. This technique uses infrared radiation to provide real-time images of the anterior segment.
The mean anterior chamber depth was 3.56 mm with the IOLMaster and 3.65 mm with the Visante-OCT, a nonsignificant difference, the researchers report.
Considering all data, measurements with Visante-OCT were 0.12 mm lower than those with the IOLMaster, they add.
Anterior chamber depth decreased with advancing age, whether measured with the IOLMaster (from a mean of 3.59 mm at age 13 years to 3.49 mm at age 17 years) or with the Visante-OCT (from 3.73 to 3.59 mm).
The researchers note that while each of the techniques has advantages and disadvantages, accuracy remains "an essential factor when selecting a device."
They conclude that there are "small but significant differences" between the Visante-OCT and IOLMaster devices and advise clinicians to take this into consideration when measuring anterior chamber depth.
"Although the absolute differences are quite small they should be taken into account in order to calculate the power on intraocular lens," write Bueno-Gimenoa et al. "The findings are interesting, as they provide more normative date for this age group."
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By Joanna Lyford, Senior medwireNews Reporter