Purpose:
Anterior eye optical coherence tomography (OCT) is an emergent modality. Despite of its high clinical utility, the application is limited only in structural investigation. Since several anterior disorders are associated with alteration of tissue property, a new modality enabling visualization of the tissue property is required. Polarization sensitive (PS-) OCT is a new modality which visualizes birefringence of tissue. Since the tissue birefringence is originated from cellular- or molecular- level tissue microstructures, PS-OCT may enable visualization of the alteration of tissue properties. This paper aims at demonstrating the clinical utility of a custom-made PS anterior OCT.
Methods:
49 eyes of 26 cases and 11 eyes of 6 normal subjects were involved. The cases include 16 glaucoma eyes (including 5 trabeculectomy blebs), 3 cases of keratoplasty, and 2 eyes of 1 case of necrotizing scleritis. The cases also include ketatohelcosis, cataract, pseudophakic eyes, uveitis, iritis, diabetes, and pituitary adenoma. The eyes were scanned by a custom-built anterior PS-OCT. This OCT possesses a depth resolution of 8.3 um and scanning speed of 30,000 lines/s and acquires a standard volumetric structural OCT and birefringence tomography. The eyes were scanned with volumetric raster scanning protocols of 4 mm to 12 mm square in 2.4 s.
Results:
In 1 of the 5 trabeculectomy blebs, strong birefringence was observed at superior to a fluid pool. This may indicate fibrosis. In all 3 eyes of keratoplasty, strong birefringence was observed at the suture site. This may indicate inflammation or abnormal cross linking of collagen. In the necrotizing scleritis, severe thinning of the sclera was observed. Qualitative observation shows weaker birefringence than normal subjects.
Conclusions:
The birefringence found in cases can be the indicator of tissue abnormality, e.g., inflammation, fibrosis and abnormal collagen cross-linking. PS-OCT could provide new insight of anterior diseases.
Keywords: imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound) • anterior segment • imaging/image analysis: clinical