Local Mydriatics

1- Parasympatholytic Mydriatics ; It abolishes the action of acetylcholine and, thus causes mydriasis by making it impossible for the sphincter muscle to contract e.g.atropine 1%, homatropine 1-2%, cyclopentolate0.5-1%, and tropicamide 0.5- 1%.

2- Sympathomimetic Mydriatics ; Directly acts on dilator pupillae to produce mydriasis e.g. adrenaline (1 in 10,000) as intra cameral injection (into A/C), phenylephrine drop (2.5-10%) and cocaine hydrochloride.

Phenylephrine has little effect on ciliary muscles and therefore , should not be considered as cycloplegic.But other parasympatholytic drugs are called cycloplegics .Among these ,atropine is the strongest cycloplegic agent, and the effect lasts for 10-14 days. Homatropine is moderately effective and its effect lasts for 48-72 hours.

Cyclopentolate and tropicamide are very rapidly acting drugs , and their cycloplegic effects usually last for 12-24 hours.

Phenylephrine (Drosyn) is also a rapidly acting drugs , the effect of which lasts only for 12-14 hours.

Uses of Mydriatics in mydriasis

1- Fundus (retinal ) examination.
2- During ECCE or posterior segment surgery .
3- To test any posterior synechia is present or not.
4- To break posterior synechiae(along with cycloplegics).

Uses of Cycloplegics in mydriasis.

1- For refraction in children, hypermetropic subjects and in squints.
2- Refraction in case where the pupil is very small.
3- In cases of Iridocyclitis ,Keratitis and endophthalmitis.
4- In accommodative convergent squint.
5- In case of accommodative spasm.
6- As “penalization” treatment in amblyopia.

Indomethacin, fluriprofen or diclofenac eye drop is used along with mydriatics for prolonging the mydriatic effect during intra-ocular surgery.

Combination of mydriatic-cycloplegic is always better except in refraction e.g.Homatropine and phenylephrine (Sunephrine- H), Tropicamide and phenylephrine(Tropicacyl plus), etc.

Mydriatics should not be used in angle closure glaucoma, or very shallow anterior chamber , and in case of operated anterior chamber or iris fixation I.O.L.