Akira Aoyama

Target intraocular pressure for stability of visual field loss progression in normal-tension glaucoma

PurposeTo determine the target intraocular pressure (IOP) level in normal-tension glaucoma (NTG) for visual field (VF) stability following trabeculectomy.MethodsForty eyes of 40 patients who underwent trabeculectomy were enrolled in this study. Progression was determined by a decrease in the Advanced Glaucoma Intervention Study VF defect score of four or more points. The Kaplan-Meier life table method was employed to compare the postoperative VF stability with predetermined IOP levels.ResultsThe mean postoperative follow-up period was 12 years. At the final visit, the IOP was reduced from 15.2 to 9.4 mmHg on average (P < 0.0001). Reductions in IOP of 20% from baseline were achieved in 70.0% of eyes. The cumulative probability of VF stability was 92.7% in patients having an IOP reduction of >20%, whereas all patients in the poorly controlled IOP group showed progression (P < 0.0001). When IOP values of 9, 10, 11, and 12 mmHg were employed as the cutoff, the best VF prognosis was attained in eyes with a postoperative IOP of 10 mmHg.ConclusionsAn IOP reduction of at least 20% from baseline or IOP ≤10 mmHg is recommended as the target postoperative IOP in progressive NTG.

Automated Detection Algorithm for Arteriolar Narrowing on Fundus Images

We have developed a computer-aided diagnosis system (CAD) to detect abnormalities in fundus images. In Japan, ophthalmologists usually detect hypertensive changes by identifying arteriolar narrowing and focal arteriolar narrowing. The purpose of this study is to develop an automated method for detecting arteriolar narrowing and focal arteriolar narrowing on fundus images. The blood vessel candidates were detected by the density analysis method. In blood vessel tracking, a local detection function was used to determine the centerline of the blood vessel. A direction comparison function using three vectors was designed to optimally estimate the next possible location of a blood vessel. After the connectivity of vessel segments was adjusted based on the recognized intersections, the true tree-like structure of the blood vessels was established. The blood vessels were recognized as arteries or veins by hue of HSV color space and their diameters. The arteriolar narrowing was detected by the ratio of diameters (artery vs. vein; A/V ratio). Focal arteriolar narrowing was detected by measuring the diameter of an artery. By applying this method to 100 fundus images, the detection sensitivity for arteriolar narrowing was found to be 76% when the specificity was 91%. Furthermore, by applying this method to 70 other different fundus images, the detection sensitivity for the focal arteriolar narrowing was 75% with 2.9 false positives per image. The number of some false positives is planned to be reduced during the next stage of development. Such an automated detection of abnormal vessels could help ophthalmologists in diagnosing ocular diseases

Long-term Therapeutic Outcome of Acute Primary Angle Closure in Japanese

PurposeTo investigate the long-term clinical course of acute primary angle closure (APAC) and acute primary angle-closure glaucoma (APACG) in Japanese patients.MethodsWe retrospectively reviewed our records of 66 consecutive APAC or APACG eyes observed between February 1992 and December 2003 (mean follow-up, 42.1 months). Immediately after the diagnosis, all patients had received similar medications to halt the acute attack. Subsequently, laser iridotomy or surgical peripheral iridectomy and/or laser iridoplasty were conducted. If intraocular pressure (IOP) control was poor under maximum tolerable ocular hypotensive agents, trabeculectomy with adjunctive mitomycin C (MMC) was undertaken.ResultsAfter laser therapy, the probability of success, defined as an IOP of <21 mmHg with or without medications, was 81.2% ± 6.2%. In the ten eyes that were trabeculectomized, the probability of success based on the same criterion was 40.0% ± 29.7%. Multivariate analysis revealed that the degree of synechial angle closure (P = 0.029) and the preexistence of chronic glaucomatous optic neuropathy (P = 0.015) significantly influenced the need for subsequent filtering surgery.ConclusionsWithout the intervention of filtering surgery, 84.6% of eyes with APAC or APACG maintained IOP control with or without antiglaucoma medications. However, APAC and APACG eyes that eventually received trabeculectomy were predisposed to an uncontrollable IOP, even with the intraoperative application of MMC. The severity of APAC or APACG in Japanese may be affected by an underlying creeping angle closure. Jpn J Ophthalmol 2007;51:353–359

Three-Dimensional Reconstruction of Optic Nerve Head from Stereo Fundus Images and Its Quantitative Estimation

It is important for diagnosis of glaucoma to grasp 3-D structure of an optic nerve head (ONH). The quantitative 3-D reconstruction of the ONH is required for the diagnosis. We propose a technique to obtain the depth value from stereo image pair of a retinal fundus for the 3-D reconstruction of the ONH. Our technique mainly consists of four steps: (1) cutout of the ONH region from the fundus images, (2) registration of the stereo pair, (3) disparity detection, and (4) depth calculation. For quantitative estimation of the depth value measured by using this method, the depth value was compared with the measurement results determined from the Heidelberg Retina Tomograph (HRT), which is a confocal laser-scanning microscope. As a result, the depth value of the ONH obtained using the stereo retinal image pair was in accordance with that obtained using the HRT (r=0.91). These results indicate that the stereo fundus images could be useful for assessing the depth value of the ONH for the diagnosis of glaucoma.