Abstract
Purpose: :
To analyze the age-related morphological changes of the iridocorneal angle in normal and glaucomatous cases using anterior segment optical coherence tomography (AS-OCT).
Methods: :
Forty eyes of 40 glaucoma cases (27 females and 13 males, mean age: 60.3±13.2 years) and 40 eyes of 40 age-matched normal controls (25 females and 15 males, 62.6±12.3 years) were enrolled in this study. Iridocorneal angle structures were measured by the enhanced high resolution mode, and anterior chamber depth (ACD) by the enhanced anterior segment mode using AS-OCT (Visante OCT, software ver. 2.0.1.88; Carl Zeiss Meditec AG, Jena, Germany). Axial length and refractive error were measured by an IOL Master (Carl Zeiss Meditec AG, Jena, Germany) and auto refracto-keratometer (RKT-7700; Nidek, Gamagori, Japan), respectively. Angle opening distance (AOD500, 750) and angle recess area (ARA500, 750), were calculated in the nasal and temporal lesion on each right eye. When the right eye was not able to be evaluated, the left eye was then utilized. Cases that produced inadequate quality of images, difficulty in detecting the scleral spur, or with previous surgical intervention such as cataract surgery were excluded. A new index which represents the peripheral angle structure was proposed; i.e., peripheral angle frame index (PAFI), defined as (ARA750 - ARA500) / ARA 500.
Results: :
The glaucoma cases, which included 13 primary open angle glaucoma cases and 27 normal tension glaucoma cases, showed significantly different angle structure between the nasal and temporal lesion, while normal controls showed no differences. There were significant differences in refractive error (p=0.0002), axial length (p=0.0004), ACD (p=0.042), and temporal angle structure (p=0.005 - 0.031) between the glaucoma and normal cases. Both ACD and ARA decreased linearly in an age-dependent manner. The new index, PAFI, stayed in relatively constant values throughout the entire age distribution, while outlier values were taken in the cases with plateau iris configuration or iris root thickening.
Conclusions: :
AC-OCT was useful for quantitatively evaluating the age-related changes of peripheral angle structure.
Keywords: imaging/image analysis: clinical • clinical (human) or epidemiologic studies: natural history • aging