Great info, thanks.
I'm a little unclear about whether you're asking about the duration of anti-VEGF treatment, or glaucoma treatment.
Re: duration of anti-VEGF treatment:
Injection are usually given between once per 4 weeks and once per 12 weeks (per eye). A "treat-and-extend" protocol usually determines the duration between visits. Usually, patients continue having anti-VEGF treatment while there is scope for improvement. It is not uncommon for patients to continue having injections for the rest of their life, at 8 week intervals, for instance. If the retina becomes badly atrophic (geographic atrophy) or scarred (subretinal fibrosis) to the point that the damage is so severe that there is little/no possibility the eye will ever have useful vision again, then a decision may be made to stop treatment. Sometimes, the treatment intervals are extended to once per 12 weeks, and even then, it is deemed too frequent, and the patient may simply be monitored for change by their optometrist etc, and return to the ophthalmologist if they experience a worsening of vision in the future.
A lot of the time, this treatment only "preserves" vision whilst treatment is ongoing, thus it continues for life. Eg, some patients turn up to clinic for their 500th left-eye injection, on their 90th birthday, for instance.
Regarding glaucoma treatment:
Quick point of clarification: Raised eye pressure is not the same as glaucoma. "Glaucoma" is damage to the retinal nerve fibre layer manifesting as a permanent/progressive visual field defect, for which IOP is frequently a modifiable risk factor.
'Most' of the time:
- it takes years to develop the visual field defect, thus, it takes years to arrive at the diagnosis of "glaucoma"
- mild chronic elevation of IOP is only treated if there is evidence of glaucoma associated with it (ie, the is evidence of a progressive, longitudinal decline in visual field, in a pattern consistent with raised IOP).
Thus, if a patient is not receiving glaucoma treatment on their first day of anti-VEGF, even if they have underlying glaucoma caused by the medication, it is unlikely that there will be enough evidence to start treatment for glaucoma by 24weeks (and thus, have an adverse event recorded). Glaucoma is typically a chronic condition which requires reassessment at spaced intervals, over time. I suspect that most of the patients who develop glaucoma will be given a diagnosis AFTER the 24week trial has finished.
But this is a hypothetical based on recent discoveries that the aqueous outflow channel (Schlemm's Canal) carries the same receptors that are being targeted in the CNV.
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