Abstract
Purpose: :
To describe the relationship between the newly described GPI in %/year and the MDI in dB/year in glaucoma patients. The GPI eliminates causes of overall depression or elevation of the field and includes a weighting procedure for excentricity. The rate of progression of visual field damage is a new paradigm in the treatment of glaucoma, it is the strongest predictor of further progression. Detection of a high rate of progression is important, it indicates glaucoma treatment should be advanced.
Methods: :
Retrospective chart review of patients with primary open angle glaucoma. Patients who had at least 5 Humphrey Swedish interactive threshold algorithm (SITA) standard visual fields where included in the study. Visual field index (VFI) in percent (%), mean defect in decibels (MD), MDI in dB/year and GPI in %/year were obtained from visual field printouts with the Humphrey Perimeter (Carl Zeiss Meditec, Dublin,California,USA) for each examination and patients respectively. Patients had not been affected significantly by cataract or undergone cataract surgery.
Results: :
We reviewed 55 eyes of 35 patients, 71.4% were female. Mean age was 75.4 years for women and 66.8 for men Patients had a mean of 9.5±3.5 visual fields. Average follow up was 76.9±28.4 months. Mean IOP was 13.6±3.1mmHg. Initial MD was -5.48±4.72dB and final MD was -8.86±5.96dB for this series (p<0.0000). The mean loss per year was 0.5±0.4dB/year for the MDI and 1.51±1.41%/year for the GPI. Correlation between GPI and MDI was highly significant (Spearman correlation coefficient 0.87 p< 0.000000). Best fit for this correlation was linear GPI=-0.1559783+2.703333MDI (r2 0.76).
Conclusions: :
A patient with visual field progression equal to 0.8 dB/year in the MDI, considered a high progressor, corresponds to 2.01%/year in the GPI. Advancement of glaucoma treatment should be considered when GPI rate of progression is equal to or greater then 2%/year in the affected patient.
Keywords: visual fields • clinical (human) or epidemiologic studies: outcomes/complications • clinical (human) or epidemiologic studies: treatment/prevention assessment/controlled clinical trials