Pupillary Dilation

Pupillary Dilation Is Used For

Pupillary Dilation is a procedure through which the specialized health care professionals (ophthalmologists) induce the enlargement of the pupil (a condition also known under the medical name of mydriasis) in order to better examine the retina. The retina is a photosensitive tissue found on the inner surface at the back of the eye. Light and visual stimuli trigger complex processes which ultimately result in the transmission of nerve impulses through the optic nerve fibers into the brain’s visual centers.

Pupillary Dilation allows the ophthalmologist to detect a number of retinal disorders. Diabetic retinopathy is a complication caused by diabetes, and it may have severe impact on the patient’s vision; it typically weakens the small blood vessels in the retina, in some cases leaks may appear. Leaking may lead to other severe complications; for example, scar tissue may form on the retina, the blood supply may decrease or blood may leak into the vitreous humor. All these may affect the patient’s vision – blurring, cloudiness and partial or total loss of vision are possible in untreated cases.

Macular degeneration is another retinal disorder, more common in elderly patients; this condition is characterized by the degeneration of the photosensitive receptors in the macula (the retinal central region) which causes a decrease in the patient’s ability to see faces or read as this area of the retina is primarily responsible for straight-ahead focused vision.

Retinal detachment is a medical condition typically caused by trauma or disease. This condition appears when a portion of the retina separates from the eye wall, and requires immediate treatment as it can rapidly result in blindness.

Vitreous disorders may also be observed; usually characterized by cloudy vision, these are most commonly caused by the presence of solid particles or “floaters” in the vitreous, partially blocking the light from reaching the retina. In some cases, these particles form before birth, however it is common for such floaters to form as the individual ages. In situations where numerous particles appear suddenly, immediate ophthalmologic examination is required as this may be a sign of a severe ocular disorder.

All these and other ophthalmologic conditions may be detected through retinal observation, which requires the application of Pupillary Dilation procedures.

Pupillary Dilation Description

Pupillary Dilation is usually induced through application of dilation drops – substances which either cause a stimulation of the dilator muscle controlling the opening of the iris, or block the action of sphincter muscle which closes the pupil. Once the dilator substance takes effect, the ophthalmologist is able to better observe the interior and the back of the eye (retina, optic nerve and the associated blood vessels). Pupillary Dilation is a very common procedure in modern ophthalmologic examinations – the vast majority of eye examination procedures will start with mydriasis induction.

The dilation of the pupil may help the specialized health care professionals determine the nature of certain affections of the eye or may assist the ophthalmologist in making more accurate observations. In certain situations, previously undetected systemic diseases such as diabetes or hypertension may be discovered during eye examinations. Also, in some cases – especially in the case of younger patients, such as children and young adults – the accommodation of the eyes needs to be blocked as it may prevent the specialized health care professional from obtaining an accurate assessment of the patient’s refraction and thus may interfere with determining the correct prescription for glasses. As such, the dilation is performed in order to obtain a “wet” refraction which will allow the ophthalmologist to correctly evaluate the patient’s condition.

After the eye exam is complete, the patient may still feel the effects of the Pupillary Dilation procedure for several hours. During this time, they may remain extremely sensitive to sunlight and generally to any bright light, and their vision may be blurred. It is advised that the patient uses protective sunglasses and avoids exposure to bright lights for a few hours after the examination, until their pupil mobility returns to normal; also, it is recommended that they avoid driving, operating machinery and other operations which require attention and coordination.

Pupillary Dilation Related Medication

There are several types of substances which are employed as agents inducing Pupillary Dilation. In most cases, they are saline-containing compounds for direct administration in the eye. They may be based on steroids (such as Dexamethasone or Mydriatics), on antihistamines, beta receptor blockers, sympathomimetic substances, parasympathomimetics (for example Pilocarpine), parasympatholytic medication (Atropine or Tropicamide), prostaglandins, NSAIDs (non-steroidal anti-inflammatory drugs) or several topical anesthetics.

Atropine is one of the most commonly used eye drops for Pupillary Dilation. It is both used as a cycloplegic agent, to block the eye accommodation reflex, as well as a mydriatic agent (for actually dilating the pupil). The degradation time for this substance is of 7 to 14 days, which makes it a better choice for therapeutic Pupillary Dilation; its effects are inferior to those of Penylephrine or Tropicamide as an aid for regular ophthalmic examination. Atropine induces the dilation of the pupil through its effect on the papillary sphincter muscle; the medicine blocks the contraction of the muscle but has no effect on the dilator muscle. Once the medicine has taken effect, the dilator muscle is able to dilate the pupil, and it remains open due to the lack of action from the sphincter muscle.

As a cycloplegic agent, Atropine paralyzes the ciliary muscle, effectively paralyzing the eye accommodation and allowing the proper assessment of  their refraction; also, it relieves pain in the case of patients affected by iridocyclitis, and may also be used as a therapeutic agent in the treatment of malignant glaucoma. Atropine is not recommended in the case of patients susceptible to developing narrow angle glaucoma.

There are several possible side effects associated with the use of mydriatic eye drops. The most common of these is an increased photosensitivity, which may last for several days after the application of the mydriatic agents. Also, natural tear production may be inhibited by abusing eye drop applications – in situations where excessive quantities have been used or when the applications are performed too often, an addictive response has been observed – the eyes are no longer able to produce tears naturally, relying on the eye drop applications to fulfill the functional role of the tears.