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Iman Goharian, David Greenfield, Mitra Sehi; Cluster-Based Trend Analysis of Visual Field Progression in Low Tension and High Tension Open-Angle Glaucoma. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3934.
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To investigate cluster-based characteristics of visual field progression in low tension glaucoma (LTG) and high tension open-angle glaucoma (HTG) using 2 trend-based analysis methods.
Records of glaucoma patients with ≥30 months of follow-up and ≥6 standard automated perimetry (SAP) tests were reviewed. Inclusion required age ≥40 years, visual acuity ≥20/40 and reliable SAP. LTG was defined as untreated IOP ≤21mmHg, no history of IOP >21mmHg, open iridocorneal angles, reproducible glaucomatous SAP abnormality and corresponding optic nerve damage. The 2 groups were matched for age, follow-up time and baseline MD. SAP test locations were grouped into 10 clusters based on the topographic distribution of the RNFL. Progression was determined using: A) Corrected Cluster Trend Analysis (CCTA; EyeSuite, Haag-Streit, Switzerland), defined as progression rate (dB/yr) in mean pattern deviation (PD) values of each cluster at p<0.01; B) Pointwise Linear Regression Analysis (PLR; ProgressorTM, UK) defined as pointwise progression rate at p<0.01 in ≥1 location in each cluster. Random effect models, ANOVA, and regression analyses were performed.
70 eyes (35 LTG, 35 HTG) were enrolled. Patients with LTG and HTG had similar age (71.5±8.9; 72.0±9.0yrs; p=0.79), follow-up time (60.9±22.4; 64.3±29.2mos; p=0.58), treated IOP (14.4±2.9; 14.6±3.9mmHg; p=0.78), baseline MD ( 4.5±4.0; -4.4±4.0dB; p=0.91), and rate of loss in MD ( 0.33±0.57; -0.15±0.72 dB/yr; p=0.27). The rate of loss in square root of loss variance (sLV) was worse in LTG (0.27±0.38dB; p=0.01) vs HTG (0.03±0.39dB). More LTG eyes were classified as progressors compared with HTG eyes using CCTA (26 vs 17; p=0.048) and PLR (27 vs 16;p=0.01). The number of progressing LTG eyes in inferior arcuate cluster was higher than the number of progressing HTG eyes (12 vs 4; p=0.03) but was similar (p>0.05) in all other clusters using CCTA. The cluster-based rates of loss were steeper in LTG in inferior arcuate ( 0.17±0.43dB/yr; p=0.03) and inferior paracentral clusters ( 0.33±0.62dB/yr; p=0.02) vs HTG ( 0.01±0.28 and -0.04±0.67dB/yr) using CCTA. Both methods agreed on 25 LTG and 16 HTG progressors, and 2 LTG and 0 HTG non-progressors (kappa=0.40;p=0.01).
Paracentral and arcuate clusters progress faster and more frequently in LTG compared with HTG and should be monitored more closely.
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