Pointwise linear regression analysis for detection of visual field progression with absolute versus corrected threshold sensitivities

PURPOSE. To compare the performance of point-wise linear regression analysis (PLR) with total deviation (TD) versus corrected or pattern deviation (PD) threshold sensitivities for detection of visual field progression. METHODS. Four hundred two eyes (402 patients) enrolled in the Advanced Glaucoma Intervention Study (AGIS) were selected. Criteria for progression according to PLR were a slope ≤ -1 dB/year with P ≤ 0.01 with ≥2 worsening points within the same Glaucoma Hemifield Test cluster. PLR was performed on TD and PD threshold sensitivities and compared to clinical evaluation. Eyes were classified into three groups based on mean deviation (MD): mild (MD ≥ -6 dB), moderately advanced (-6 dB > MD ≥ -12 dB), and advanced (MD < -12 dB) glaucoma. RESULTS. Visual field progression was observed in 154 (38%), 85 (21%), and 175 (44%) eyes, according to PLR(TD) and PLR(PD), and clinical evaluation. The pair-wise agreement between clinicians and PLR(TD) was significantly greater than that of clinicians and PLR(PD) (κ = 0.48, 95% CI: 0.44-0.52 vs. K = 0.31, 95% CI: 0.27-0.35). Agreement between PLR(TD) and PLR(PD) decreased with increasing glaucoma severity: K (95% CI) = 0.60 (0.52-0.67), 0.41 (0.35-0.47), and 0.33 (0.27-0.40) for mild, moderately advanced, and advanced glaucoma, respectively. CONCLUSIONS. Point-wise linear regression analysis on TD threshold sensitivities performed better than the same analysis on PD when clinical evaluation was used as a reference. Agreement between the two methods was less in moderately advanced and advanced glaucoma.