Quantitative evaluation of trabecular meshwork in normal tension glaucoma using trabecular meshwork analyzing software.

Abstract

PURPOSE This study aimed to investigate histological changes of trabecular meshwork (TM) in normal tension glaucoma (NTG) and determine whether trabeculectomy (TRAB) specimens from NTG patients can serve as normal controls for analyzing other types of high-tension glaucoma using TM analysis software (TMAS) based on light microscopy (LM). DESIGN Prospective comparative case series METHODS: TRAB specimens from 23 NTG patients (65.4±9.2 years-old), including associated clinical data, as well as 12 autopsy eyes (66±11.2 years-old, P=0.8637), were retrospectively analyzed. LM images of TRAB specimens were captured, and TM spaces, TM cellularity, and pigment granules (PG) accumulation in TM were evaluated using TMAS. TMAS1 assessed regional variations in the juxtacanalicular tissue (JCT), corneoscleral meshwork (CSM), and uveal meshwork (UVM) by dividing these regions into anterior, middle, and posterior segments, while TMAS2 measured the total areas of JCT, CSM, and UVM. MAIN OUTCOME MEASURES Intraocular pressure, outflow facility, axial length, periods of topical glaucoma medication, spaces in juxtacanalicular tissue, corneoscleral and uveal meshwork, trabecular meshwork cellularity, pigment granule accumulation RESULTS: NTG patients exhibited features such as myopia (-5.5±4.7 D), long axial length (26±2.5 mm), advanced stage of visual field defect (Aulhorn-Greve classification: stage 4.6±0.9), prolonged use of topical-glaucoma medications (13.0±5.0 Y), and subnormal outflow facility (0.24±0.09 µl/min/mmHg). TM spaces measurements showed no notable differences between TMAS1 and TMAS2 in NTG eyes. However, TMAS2 detected a significantly greater reduction in TM spaces (JCT: P=0.000, CSM: P=0.000) and a lower TM cell count (JCT: P=0.0285, UVM: P=0.0006) in NTG specimens compared to autopsy eyes. CONCLUSION NTG should not be regarded as a normal variant, as structural abnormalities are present despite normal intraocular pressure. These abnormalities may arise from subtle irregularities in the TM, which may be less pronounced than those in high-tension primary open-angle glaucoma, prolonged use of topical glaucoma medications, or other contributing factors such as increased axial length. TMAS2 has proven to be a useful instrument for assessing not only NTG but also a potential means of identifying different types of high-tension glaucoma through the analysis of TRAB specimens.