[Visual field change and risk factors for progression of visual field damage in low tension glaucoma]

The authors carried out a prospective study in an attempt to determine the possible effect of intraocular pressure (IOP) and some clinical factors on the clinical course of low tension glaucoma (LTG). During the study period all the patients were followed without any antiglaucoma medication. The enrollment criteria for the study were reproducible, mild to moderate field loss as defined as a mean defect (MD) of greater than 2 dB and less than 10 dB or corrected loss variance (CLV) of greater than 7 dB revealed by the Octopus 201, G1 program. Forty-two consecutive patients (56 eyes) who fulfilled this criteria were enrolled. Baseline and follow-up examinations included applanation tonometry, perimetry with G1 program, blood pressure and pulse rate. When the MD increased by 4 dB or more on two consecutive perimetry examinations, the field defect was judged as "progressed". During the follow-up period (6-51 months, 25.1 +/- 12.5 months), the field defect progressed in 14 eyes of 12 patients. The life-table analysis (Kaplan-Meier) revealed that the rate of nonprogression of visual field defects was 55.5% at 48 months. The rate of nonprogression was significantly lower in 16 eyes with a mean IOP equal to or higher than 15 mmHg as opposed to 40 eyes with that lower than 15 mmHg (34.3% and 67.2% respectively, p less than 0.05). The results seem to indicate that IOP is likely to be responsible for the aggravation of visual fields in LTG. Canonical discriminant analysis revealed that the discriminant function containing four variables gives the best separation between the "progressed" and "nonprogressed" group (discriminant efficacy: 83.9%).