Purpose: to establish a clear definition of low-tension glaucoma (LTG) as well as its differential diagnosis with pseudoglaucomas.
Material and Methods: 6,154 consecutive clinical histories from 1963 to 2000 belonging to open-angle glaucomas were retrospectively reviewed. The visual fields of all these cases had been monitored, in the earlier ones by Goldmann perimetry, and as new technologies became available, with automated, computerized Octopus perimetry. The optic nerve was evaluated with ophthalmoscopy as well as with stereoscopic photographs taken with Zeiss retinograph in the earlier cases and then with the Heidelberg Retina Tomograph (HRT) as from 1989. The IOP was monitored by means of single spot-checks as well as by daily pressure curves, which consist of 7 IOP measurements with applanation tonometry, the first one with the patient still in bed at 7 a.m. and the subsequent ones at 9 and 12 a.m. and at 3, 6, 9 and 12 p.m. at the ophthalmologist’s office. The daily mean IOP was calculated by dividing the 7 readings by 7 and the variability, i.e. standard deviation, was also obtained. LTG was defined as an optic nerve and visual field pathology associated with 3 normal consecutive monthly daily pressure curves.
Results: After performing daily pressure curves on all 6,154 cases studied, only 12 ‰ were left and thorough differential diagnosis was thoroughly considered in order to rule out any pseudoglaucoma of neurologic or other origin, resulting in only 5 ‰ cases diagnosed as actual LTGs, of which 75 % were vasospastic ones.