Marseille, France-Anterior chamber OCT (Visante, Carl Zeiss Meditec) is new and powerful technology with important applications in research and clinical practice, said Georges D. Baikoff, MD.
Dr. Baikoff presented his experience using anterior chamber OCT for the in vivo study of accommodation in human eyes and findings from investigations in eyes with phakic IOLs implanted. In addition, he provided a glimpse into the future of this technology with the development of three-dimensional reconstruction of OCT-acquired images.
"I am currently using this device routinely in daily practice, but with the advent of three-dimensional imaging, it will become an even more important research and clinical tool," said Dr. Baikoff, Clinique Monticelli, Marseille, France.
Measurements made from the OCT images in younger subjects with maximum accommodative potential showed the crystalline lens anterior pole shifted forward during accommodation by about 30 µm per 1-D change in accommodation. It was also noted that the shape of the anterior lens surface changed during accommodation, with a steepening of the surface as accommodation increased. For 10 D of accommodation, the radius of curvature decreased by about 5 mm and the lens thickness increased by about 700 µm. Pupil diameter also decreased during accommodation by an average of 1.5 mm per 10 D.
Effects of aging
However, the ability of the lens to deform and move forward during accommodation decreased with increasing age and the lens itself thickened and became steeper.
"This in vivo imaging technology provides a unique opportunity to study modifications of the anterior chamber during accommodation," Dr. Baikoff said. "The findings are consistent with the theory of accommodation put forth by Helmholtz more than 100 years ago."
Although the infrared light of the anterior segment OCT device is not transmitted through iris pigment, imaging of an eye in an albino patient allowed more complete characterization of changes in lens shape during accommodation.
The studies showed the anterior lens surface was completely spherical when accommodation was at rest, but varied in curvature during accommodation when both forward movement of the anterior pole and posterior movement of the posterior pole were observed, according to Dr. Baikoff.
Consistent with the observation of lens thickening with age, studies in eyes with anterior chamber phakic IOLs implanted show the development of contact between the crystalline lens and the implant over time. Studies in a series of patients with the iris-fixated phakic IOL (Artisan, Ophtec) implanted were helpful for providing insight into criteria to reduce the risk for pigment dispersion with implantation of that device.
"Comparing eyes with and without pigment dispersion, we found that complication was nearly restricted to eyes with a crystalline lens rise greater than 600 µm and an anterior chamber depth less than 3.2 mm," he said.
In eyes with a posterior chamber phakic IOL, images acquired with anterior chamber OCT demonstrated contact between the implant and the crystalline lens during accommodation, especially in hyperopia.