[Managing treatment side effects: the respective roles of the active ingredient and the preservative]

The side effects of glaucoma hypotensive treatments usually remain moderate and limited to local side effects - conjunctival hyperemia, itching, discomfort after instillation - but are very often a leading source of poor compliance to treatment and thereby may decrease its efficacy. Moreover, these symptoms usually reflect progressive and irreversible major ocular surface changes. These ocular surface changes induced by glaucoma eyedrops may include subconjunctival fibrosis, increasing the risk of failure of a further glaucoma surgery. All the components of the hypotensive eye drops, including the active ingredient, the preservatives, and the excipients, may be involved in the occurrence of these side effects. It is therefore important to identify the agents involved and the mechanisms of these side effects, in order to choose a treatment minimizing their risk and the discomfort felt by patients, and therefore increasing the likelihood of good compliance. When available, preservative-free solutions should be considered.