atropine

[anonym]

Hello, dear iblindness community,

Can someone explain to me what is (and what is the purpose of) atropine that the so-called eye doctors put it in our eyes to "paralyze our accommodation" when they test our vision?

Never again, Catherine

[otis]

Dear Catherine,

Atropine is a poison.

There are two purposes of this poision.

1.  Open of the iris so that the retina can be examed easily.
Fair enough.  (Cyclogel can also be used for the same purpose.)

2.  Freeze the eye, paralyize accommodation, make the eye
"dead", so that an so-called "objective" measurement
can be made.  Not fair!

As far as I am concerned, the correct way to measure
refractive STATE is with a Snellen and a trial-lens
kit.  (Standard for the last 100 years.)

These two methods yield contradictory results.

Otis

[apavel]

Otis pretty much covered it,
atropine is a competitive antagonist of the acetylcholine receptors in the muscles controlled by the parasympathetic nervous system.  In other words it is sort of a "sympathetic promoter" by paralyzing various involuntary muscles.  In terms of opthamology, it is used to block the contraction of the pupillary sphincter allowing your pupil to dilate completely.  This allows the optometrist to examine your retina for any defects or damage. 

I dont' think atropine is used in opthalmology much anymore because it degrades slowly and the effects can last for weeks.  They use other drugs that degrade within hours.  Also, I'm not 100% sure, but I believe the accommodation shutdown is a side effect.  Ophthalmologists do not actually intend to subdue your accommodation.  However, according to Bates it doesn't  :-\. 

It is also used during surgery to reduce the corneal swelling and inflammation.

Paul

[anonym]

Hello, dear Otis and Paul,

Your interesting and educative responses are much appreciated!

Warm regards, Catherine