Are the effects of steroid drops in the eye reversible?

Some are. Steroid induced eye pressure changes usually improve after stopping steroids, steroid induced cataract is not reversible, but can be treated with cataract surgery if causing vision loss.
Depends. Depending on your diagnosis, steroid eye drops used chronically for inflammatory eye disease can cause cataracts, which are reversible. Steroids may also raise intraocular pressure and cause glaucoma which is often not reversible, but treatable. Steroid eye medication can also be used briefly for mild inflammation too, which, when monitored, results in effective treatment without side effects.