Purpose: To analyze age-related morphological changes of the iridocorneal angle in normal subjects and glaucomatous cases, using anterior segment optical coherence tomography (AS-OCT).
Methods: This study involved 58 eyes of 58 open-angle glaucoma cases and 72 eyes of 72 age-matched normal-open-angle control subjects. Iridocorneal angle structures in nasal and temporal regions and anterior chamber depth (ACD) were measured using AS-OCT. Axial length and refractive error were measured by use of an ocular biometer and auto refractor keratometer. Angle opening distance (AOD), angle recess area (ARA), and trabecular-iris space area (TISA), measured at 500 μm (TISA500) and 750 μm (TISA750) distant from the scleral spur, were calculated, in the nasal and temporal regions. A new index, the peripheral angle frame index (PAFI), which represents the peripheral angle structure, was proposed, and was defined as (TISA750-TISA500)/TISA500.
Results: Refractive power in the glaucoma cases was less than in control cases (P<0.0001). Axial length (P<0.0001) and ACD (P=0.0004) were longer and deeper, respectively, in the glaucoma cases, compared with the control cases. In both control and glaucoma groups, ACD, AOD, ARA, and TISA decreased linearly in an age-dependent manner, while PAFI stayed at relatively constant values throughout the age distribution. AOD in the glaucoma group was longer than in the control group, in both the temporal and nasal regions; ARA and TISA were larger in the glaucoma than in the control group. However, no significant differences in nasal or temporal PAFI were found between the glaucoma and control groups.
Conclusion: The findings of this study show that AS-OCT is useful for the quantitative evaluation of age-related changes in peripheral angle structure in glaucoma and control cases.
Keywords: AS-OCT; PAFI; anterior segment optical coherence tomography; iridocorneal angle structures; peripheral angle frame index.