Other Cholinergic Agents

Acetylcholine

It is used only for intraocular (intracameral route) administration. It produces complete miosis during ocular surgery and Used in cataract surgery, penetrating keratoplasty, peripheral Iridectomy and other anterior segment surgery.

It is available as powder and fresh ophthalmic solution (1:100 acetyl choline chloride). Usually 0.5 - 2 ml of this solution is required to produce good miosis. Solution need not be washed as it has a short duration 10-20 mins.

Carbachol

  1. It is a synthetic derivative of choline.
  2. It is dual action parasympathomimetic which produces direct motor end plates stimulation and at pre synaptic receptors to release acetylcholine. They are longer acting than pilocarpine. Thus greater stabilizing effect on diurnal pressure and myopia fluctuations.
  3. Comes in 0.75% to 3% concentration administered 3 to 4 times a day.
  4. Can be used in patients who are allergic to pilocarpine.

Methacholine

  1. It is also a synthetic derivative rarely used because it is unstable.
  2. It was used in 2% to 10% concentration.

Aceclidine

  1. A synthetic agent directly inhibits cholinesterase.
  2. Acts directly on the muscarinic end plates.
  3. It is weaker than pilocarpine and induces less miosis and accommodation than pilocarpine.

Miotics are contraindicated or avoided in:

Eyes with ocular inflammation.

Patients who are younger than 40.

Patients with central corneal opacities.

Moderate to severe myopia.

Presence of peripheral retinal degenerations.

Eyes with extensive synechial angle closure.

Malignant glaucoma.

Angle recession glaucoma (miotics causes a paradoxical IOP raise by decreasing uveoscleral outflow).

Acute pressure elevation in which the angle closure due to forward displacement of iris lens diaphragm.