We read with great interest the article by Kim and associates, which addresses an important topic on preperimetric open-angle glaucoma that helps in treatment decision making. The authors have made a good attempt to study the impact of intraocular pressure (IOP)-lowering treatment. However, the natural course of this stage of disease could be more accurately assessed if there were a control group with no treatment.
Though the authors state that the study included preperimetric open-angle glaucoma, the mean baseline IOPs, demographic characteristics stated to be associated with progression (female sex, self-reported cold hands and feet), and association of disc hemorrhages indicate that the cohort predominantly consisted of patients with normal tension glaucoma.
Optic disc and retinal nerve fiber layer changes were analyzed to establish structural progression. The exact cut-off for defining significant change or progression in each parameter needs to be defined to validate the measurements. It is unclear which parameters of structural progression were evaluated for agreement by kappa statistics. Besides, the use of kappa statistics has several disadvantages, which can be smoothened by use of intra-class correlation coefficient.
The rate of mean deviation (MD) change was −0.03 ± 0.24 dB/year in nonprogressors and −0.66 ± 0.6 dB/year in progressors. Yet a relook into Figure 3 shows that only a minimal fraction experienced MD change >−2 dB (defined as progression in EMGT ), while the majority had 0–1 dB change over 5 years in this cohort of preperimetric glaucoma; the clinical significance of such a change is unclear.
Lack of association between disc hemorrhage and functional progression may be attributable to time lag for functional deficits to appear or might have been owing to rescue of retinal ganglion cells by aggressive treatment. The impact of disc hemorrhages would be more accurately understood if there were a control group to derive the number needed to treat.
More prospective studies with a control group are needed to understand the natural course of preperimetric glaucoma among all racial groups across the world. This study is definitely a good effort on this path.