Ultralong scan depth OCT can measure anterior segment dimensional changes

This study found that ultralong scan depth optical coherence tomography (UL-OCT) can measure dimensional changes in the anterior segment during accommodation with good repeatability and reliability.

The device allows scan depths of more than 11 mm to image the anterior segment extending through the pupil to the posterior surface of the crystalline lens. The authors found that during accommodation, the anterior surface of the lens becomes steeper and moves forward as the anterior chamber shallows. Precise understanding of the dimensional changes in the eye during accommodation should inform the design of future accommodative intraocular lenses.

Forty-one right eyes of healthy subjects with a mean age of 34 years and a mean refraction of -2.5 ± 2.6 diopters were imaged at minimal and maximal accommodation. They used a customized UL-OCT instrument to image from the front surface of the cornea to the back surface of the crystalline lens.

Repeated measurements of each variable within each accommodative state did not differ significantly (P > 0.05). The coefficients of repeatability and intraclass correlation for central corneal thickness, anterior chamber depth and width, lens thickness, lens central position and anterior segment length were excellent. They were higher for pupil diameter and moderate for anterior and posterior surface curvature at minimal and maximal accommodation.

Previous investigation of the posterior lens surface during accommodation has been limited and the results contradictory. In this study, the posterior surface of the lens steepened in accommodation. Interestingly, a recent report using 3-dimensional magnetic resonance imaging also demonstrated an increased curvature of the posterior lens surface with accommodation.

The steepening of anterior lens curvature was greater than that of the posterior curvature, suggesting that the anterior surface has a greater role during accommodation. However, although the magnitude of the posterior surface changes was less than the anterior surface, the changes in posterior curvature may be important, especially in elderly people whose lenses have a relative higher refractive index.