This randomised controlled multi-centre study examined the influence of IOP in Normal Tension Glaucoma. 140 patients with progressing NTG were randomised to (1) treatment arm - aiming for IOP reduction of 30% within 6 months and maintaining for 4 years by surgical and/or medical means or (2) untreated arm. Findings can be summarised as follows:
- Mean IOP in the treatment group was 10.6mm and untreated group was 16.0mm
- Survival analysis showed statistically significant difference in disease progression in the two groups (p<0.0001) - when examining for specifically defined end-point criteria of optic disc appearances and field loss
- Cataracts were more common in the treated group (38% versus 14%) particularly among those treated surgically
- Due to influence of cataract on visual field analysis, authors could only conclude that "therapy that is effective in lowering IOP and free of adverse side effects would be expected to be beneficial in patients who are at risk of disease progression."
- An intention-to-treat analysis in a subsequent paper from the Group (Am J Ophthal 1998; 126:498-505) failed to show any beneficial effect of treatment despite treatment group IOP 10mm versus 16mm for non-treatment.