Dilating drops are useful tools for examining the eye. A dilated pupil exam provides direct visualization and is the best way to examine the retina and is second to none. The dilating drops are annoying, but are necessary. Any and every time your doctor needs to look at your retina (or other structures such as the optic nerve), your pupils should be dilated.
Dilating drops cause mydriasis (pupillary dilation) and cycloplegia (see below). They really have no medicinal purpose, though in certain types of inflammation, they may relieve pain. Atropine, or bella donna, was used in ancient times to dilate the pupil as a way to accentuate beauty. In modern times, atropine, or atropine-like medicines, are used to facilitate retinal examination, paralyze focusing ability and allow intraocular surgery.-
Retinal examination for conditions such as diabetic retinopathy and macular degeneration should be performed regularly. The best, cheapest and most efficient way to exam treat these disease is by looking directly at the retina. Two types of drops are usually used to effectively dilate the pupil. Actually, the “pupil” is the opening in the iris. One drop activates a muscle (alpha-adrenergic muscles) that runs radially (like spokes on a wheel) on the iris. A second drop, inhibits constriction of a circular muscle (it closes the pupil like a purse-string) on the edge of the iris, thereby allowing dilation to occur, that is, in normally opposes the action of the radial muscle.
With a widely dilated pupil, a cataract can be properly identified, the optic nerve inspected for disease such as glaucoma, the retinal veins and arteries are revealed, not to mention detailed examination of the macula and peripheral retina.
Paralysis of Focusing Muscles is a secondary effect of complete dilation. This is called “cycloplegia.” The muscles that contract to reshape our natural lens allowing focusing for reading (and focusing at distance for far-sighted people) are paralyzed. This wipes out close range focusing and distance focusing (for far-sighted people only).
For children, who are usually farsighted at a young age, this is an important step in properly measuring for glasses. As the eye gets bigger, we become more near-sighted (or less far-sighted). Thus, most average kids are farsighted and don’t need glasses in most cases. To properly measure far-sightedness, however, especially in a kid, the muscles need to be paralyzed.
For adults, this a very annoying part of the dilated exam – there is too much light entering the pupil and everything is fuzzy!
In most cases of intraocular surgery, such as cataract surgery and retinal surgery (aka vitrectomy), the pupil must be widely dilated to see and operate. Pre-operatively, the same drops are given to dilate the iris/pupil at the operating room as used in the office. The dilation can last for hours which should be enough time to get the operation done.
What Does This Mean? Dilating the eye is important because the most important structures of the eye; lens, optic nerve and retina, can only be examined by looking directly at them. Every time a retinal examination is anticipated you should dilated. Some docs are using non-mydriatic (aka non-dilating) equipment to see in the eye, but these devices are designed for screening purposes and are not considered detailed enough to allow a diagnostic exam. The point is…get dilated.
There used to be drops that reverse dilation, but I haven’t seen them in a few years. They are expensive to use and are uncomfortable for the patient.
Randall V. Wong, M.D.
Retina Specialist, Ophthalmologist