Bleb Height Assesment for Post-Trabeculectomy by Using Stereo Image

摘要

Glaucoma is caused by improper absorption of intraocular fluid into bloodstream so it increase intraocular pressure (IOP) of the eye. In many cases of glaucoma, the drainage channel becomes clogged, so that intraocular fluid cannot drain properly. As a result, the fluid builds up and causes IOP to increase. The common surgery treatment for glaucoma is called trabeculectomy by removing part of the eye's trabecular. After the surgery, a slightly lifted tissue due to passing fluid called bleb will appear. Bleb assesment is necessary to examinate the successful of surgery. One of the standard assesment known as Indiana Bleb Appearance Grading Scale (IBAGS) grade the bleb base on four parameters namely, bleb height, extend, vascularity and leakage. Among those four parameters, bleb height was strongly asscociated with a decrease in IOP but also very hard to assess especially only from a single bleb image. This work proposed an algorithm for bleb height assessment by using a stereo image to get a better depth perception. The proposed algorithm developed base on the disparity pixel of the stereo image using slit light followed by classification to match the IBAGS standard by using threshold method. The result showed an increase of Cohen's kappa coefficient from 0.20 to 0.48 indicating better agreement between inter observer assessment.