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Anterior segment OCT accurately measures lens thickness in clear or opacified lenses
Invest Ophthalmol Vis Sci. 2009;50(1):290-294.
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Anterior segment optical coherence tomography proved accurate and predictable in measuring lens thickness in most eyes with clear or opacified lenses.
A-scan ultrasonography and Scheimpflug imaging are the most commonly used methods for measuring lens thickness in vivo.
"This newly available anterior segment technique offers a new noncontact method for the quantification of [lens thickness] that may help research on myopia and angle closure," the study authors said.
The study included 66 phakic eyes of 48 elderly patients who had a mean age of 65.4 years, and 56 eyes of 56 young patients who had a mean age 27.7 years. Two masked observers took three anterior segment OCT measurements and three A-scan ultrasonography measurements.
In elderly patients, anterior segment OCT had a failure rate of 9.1% and A-scan ultrasonography had a failure rate of 7.6%. All measurements were successful in young patients. Anterior segment OCT yielded markedly higher lens thickness values than A-scan ultrasonography. Agreement between observers' anterior segment OCT measurements was slightly higher than between observers' A-scan ultrasonography measurements.
According to the authors, this is the first attempt to measure the relative accuracy of anterior segment optical coherence tomography and A-scan ultrasound for the estimation of lens thickness. The study evaluated two subsets, those lenses with cataractous changes and those that were clear. The results demonstrate similar findings with both biometric techniques. The user friendliness and greater measurement reproducibility favored the light interferometry over the sonic method.
Imaging continues to grow in importance as a way to assess ocular anatomy. In the case of anterior segment OCT and lens thickness measurements, the authors hope we can gain a better understanding of the pathophysiology of angle closure glaucoma and identify those eyes at risk of this sight threatening condition.
– R. Bruce Wallace III, MD
OSN Cataract Surgery Board Member