We thank Rao and associates for their interest in our article. First, we would like to address their comments regarding our study population. We agree that including an untreated control group would be more beneficial for a fair comparison. However, this was not a prospective, randomized clinical trial, and our goal was to investigate the long-term outcome in treated preperimetric open-angle glaucoma (OAG) patients. Therefore, we believe that our retrospective cohort closely represented the patients we observe in a clinical setting. Second, as Rao and associates mentioned, the majority of our patients had low baseline intraocular pressure (IOP), which may have affected our results (eg, associated factors, progression rates). Thus, as stated in our article, these factors should be considered when interpreting our results.

Rao and associates questioned our structural progression parameters, which have been previously used in many relevant articles. In our study, 2 masked observers independently evaluated the photographs according to our clearly stated criteria. This evaluation was based on the clinicians’ subjective evaluating system, since clinicians define “progression” by noting the presence of structural change rather than by applying cut-off values. We used kappa statistics because we assessed the inter-observer agreement for determining structural progression, and this method is widely applied for assessing agreement.

The definition of functional progression in glaucoma varies among studies, depending on the index (eg, mean deviation [MD], visual field index), statistical method, and study design. In our article, MD rates were presented to show the treatment outcome and not to define the progression. Additionally, Rao and associates questioned the clinical significance of the functional change in our patients, since only a small proportion of patients showed a fast progression rate. However, the clinical relevance of our investigation is not only for the determination of the progression rate and the associated factors, but also for early identification of patients who will most likely benefit from intensified treatment to prevent loss of vision-related quality of life. Moreover, in previous reports, most glaucoma patients under routine glaucoma treatment demonstrated slow functional progression, exhibiting rates similar to ours.

Our study showed that disc hemorrhage was closely associated with structural progression, and we proposed 2 possible reasons for this: a larger proportion of preperimetric OAG patients with low baseline IOP and insufficient follow-up time to show functional progression. We partly agree with Rao and associates that patients with disc hemorrhage might not have shown functional progression because they received more intensive IOP-lowering treatment. However, a number of patients with disc hemorrhage showed insufficient IOP reduction percentage. Additionally, their comment is based on the assumption that structural change precedes functional change, which remains a subject of debate. Prospective studies with a population with greater ethnic and characteristic diversity, an untreated arm, and a longer follow-up period would be helpful for understanding the natural clinical outcome of preperimetric OAG patients.