In many cases, no treatment will be necessary, as the eye will eventually heal itself over time and return to normal. However, more direct methods could be necessary in certain circumstances.
Antibiotics/Antifungals
In the event of a particularly aggressive infection, it may become necessary for the vet to prescribe antibiotics. Typically, these will be given to you to administer at home and will take the form of either an eye drop or a pill. Whilst the pill can be mixed in with food, the eye drop can be more difficult to administer. Although a simple reward system can be used to entice the cat to cooperate with treatment, your vet may have specific advice on how best to proceed. Treatment times can vary from several weeks for a course of antibiotics to several months for antifungal drugs to do their work entirely.
Muscarinic Receptor Blockers
If your vet believes that there is a risk of further adhesion, they may decide to prescribe drugs that prevent the muscles that expand and contract the pupil from moving. This is to prevent further 'sticking' of the iris to the tissues of the cornea and lens as it comes into contact with them. These compounds are similar in nature to the drug atropine, which prevents involuntary muscle spasms, and the treatment typically delivered to animals in the form of an eye drop. Recovery times with this treatment will vary with the severity of the injury to the eye, but typically last approximately a month.
Surgery
If severe glaucoma appears, it may be necessary to perform laser surgery to remove the opaque tissue from the eye and remove the areas of the iris and lens/cornea that are adhering to one another. Surgery is the most drastic measure that can be taken, and as such will necessitate a long duration of follow-up visits and checkups to make sure the cat is healing well.
The chances of relapse are minimal when dealing with synechiae. Though if the condition is due to a bacterial infection, your vet may have advice on identifying and removing the threat if it is on your property in order to prevent re-occurrence.