2-dimethylaminoethyl ( RS )-2-(1-hydroxycyclopentyl)-2-phenylacetate hydrochloride
Cyclopentolate hydrochloride is a chemical that, when dropped into the eyes, causes the pupils to dilate. It is usually found in a solution sold under the names Cyclogyl, Cylate, Pentolair, Ocu-Pentolate, Diopentolate and AK-Pentolate, among others.
The chemical is "an anticholinergic prepared as a sterile borate buffered topical ophthalmic solution". It "blocks the responses of the sphincter muscle of the iris and accomodative muscle of the ciliary body to cholinergic stimulation, producing pupillary dilation (mydriasis) and paralysis of accomodation (cycloplegia)."1
Cyclogil is administered just like any other eye drop. A single drop is enough to completely dilate one eye. The immediate effect of the medication is a burning sensation in the eyes that generally goes away in less than a minute. By five to ten minutes the pupils are completely dialated, leaving the subject with a sensitivity to light, and blurred near vision. This lasts sometimes over 24 hours, but the effects usually weaken in just under six. If you are given Cyclogyl you might want to wear sunglasses when going outside. This will protect your eyes from the light and stop you from completely freaking people out. Affected pupils are more dialated than most people are accustomed to seeing. In fact they're as wide as dinner plates, and are reminiscent of those black contact lenses seen in cheesy rock videos.
An optometrist or ophthalmologist may administer a single dose of Cyclogyl before examining the tissue inside your eye. (Getting the iris out of the way makes it easier to see back there.) Cyclogyl can also be used to prevent damage to the lens in cases where the eye is inflamed and the iris is pushing up against the lens.
Cyclogyl can increase intraocular pressure in some cases. It can also cause psychotic reactions in some children. These include hallucinations and behavioural disturbances. This is probably because their younger bodies cannot cope with the drug as well. Oddly enough, children with blonde hair and blue eyes are more susceptible.
1. From the Cyclogyl product sheet, produced by Alcon Canada Inc.