Abstract
Purpose: :
To develop and test biocompatible contrast enhancing agent for imaging the tears and contact lens with ultra-high resolution optical coherence tomography.
Methods: :
A high-resolution spectral-domain OCT system with a depth resolution of ~3µm in tissue together with advanced scanning optics was built for imaging the anterior segment of the eye. The system is able to acquire high quality 3D images of the cornea in 2.7 seconds with a lateral scanning range of up to 15 mm. Biocompatible optical scattering medium (Intralipid) was used for the first time to enhance the boundaries of the tear meniscus and contact lenses for OCT imaging. The mean and most probable particle diameters of Intralipid-10% are 97 nm and 25 nm, which are much smaller than the depth resolution of the OCT system. The small particle size, biocompatibility, effective scattering, and low absorption make Intralipid a good contrast agent for imaging the tears on the contact lenses.
Results: :
In the OCT image of contact lens with contact lens solution only the central portion of the front and back surfaces can be seen clearly. The lateral drop of the OCT signal at the back surface of the lens is more severe than the front surface. From the OCT images with Intralipid both the front and back surfaces of the lens are highlighted significantly and can be seen clearly in the entire image range. The enhancement of the back surface of the contact lens is even more striking. We also tested the effect of contrast enhancement on a human eye with a contact lens. Artificial tears were applied to the contact lens surface. Without contrast agent the boundary between the artificial tear and the contact lens is clear only at the central portion of the contact lens while the boundary between the tear meniscus and the contact lens is not recognizable. With contrast agent for the same eye the boundaries between the contact lens and the upper and lower tear menisci can be clearly visualized.
Conclusions: :
We have for the first time successfully tested Intralipid as a contrast agent for OCT imaging of the tears on contact lenses. The contrast agent significantly enhanced both the front and back surfaces of a contact lens in OCT image. The contrast agent also successfully enhanced the boundaries of the tear meniscus, which makes the calculation of the volume of tear meniscus possible_an important parameter in the diagnosis and study of dry eye.
Keywords: cornea: tears/tear film/dry eye • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • contact lens