Internal Crystalline Lens Structure Imaging using Long Range Optical Coherence Tomography

Abstract

Purpose: : To demonstrate the feasibility of quantifying the internal human crystalline lens structure using Optical Coherence Tomography (OCT).

Methods: : Eight isolated human lenses (31-90 y/o) were imaged with a custom-built time-domain system (Uhlhorn et al, Vis Res 2008) and 3 in vivo human lenses (24-34 y/o) were imaged with a custom-built extended-depth spectral-domain OCT system. The internal structure was analyzed qualitatively to determine if the zones of optical discontinuity that are seen in slit-lamp images can be detected. The nuclear and cortical thickness were measured. The cortical thickness was defined as the combined width of the C3, C2 and C1 zones which were determined by measuring the distance between local minima on the central A-line intensity profile. Optical distances were divided by published values of the average refractive index of the lens to produce true distances (Uhlhorn et al, Vis Res 2008).

Results: : The lens structure is apparent in all isolated and in vivo lenses. The number of discrete zones of optical discontinuity is correlated with the age of the lens. For isolated lenses thicknesses ranged from 0.88-1.67mm for the anterior cortex, 0.72-1.17mm for the posterior cortex and 2.27-2.83mm for the nucleus. In vivo thicknesses ranged from 0.59-0.78mm for the anterior cortex, 0.83-0.90mm for the posterior cortex and 2.07-2.65mm for the nucleus. These values agree with previous in vivo Scheimpflug studies (Dubbelman et al, Vis Res 2003).

Conclusions: : The study demonstrates the feasibility of imaging the zones of optical discontinuity of the in vitro and in vivo lenses using OCT.

Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • anterior segment • optical properties