If there is a greater amount of anisocoria in the bright light, and the larger pupil is not constricting like it should, you are likely dealing with a parasympathetic pupil problem. If the amount of anisocoria is the same in both the bright light and the dark, then the anisocoria is physiologic. How do you know if the anisocoria is a problem?Īnd, if it is problematic, is it the bigger pupil or the smaller pupil that you need to be worried about? In order to differentiate physiologic anisocoria from a pathologic or pharmacologic cause, pupil sizes should be re-measured in bright and dark lighting conditions, isolating the parasympathetic and sympathetic pathways. 2 Pupils should be within 1 mm in size of each other.Īny difference in pupil size between the two eyes is known as anisocoria and can be physiologic (which occurs in approximately 20 percent of normal patients), pharmacologic, or pathologic in nature. Under normal illumination, the average adult’s pupil size measures around 3.5 mm but can range from 1.0 mm to 10 mm and decreases as one ages due to senile miosis. In either situation, it is imperative that both pupils be illuminated equally and simultaneously. In addition, the ophthalmoscope can also be used as a dim flashlight to measure pupils while looking from outside the instrument.
If needed, the clinician can view the patient’s pupils through the direct ophthalmoscope, and measure the size of the red reflex. It can be particularly challenging to accurately measure the size of a patient’s pupils if his irises are dark. To avoid stimulating the accommodative response and consequential constriction, the ruler should be held away from the visual axis of the patient. Measurement of pupil size should occur under normal lighting conditions to the nearest 0.5 mm using a millimeter ruler or pupillary gauge while the patient fixates on a distant, non-accommodative target. Other gross observations for abnormalities could include evidence of corectopia (displaced pupil), polycoria (multiple pupils), leukocoria (white pupil, which can be an ominous sign of a serious ocular form of cancer known as retinoblastoma), or iris heterochromia (difference in iris colors between the two eyes).Īlthough pupil testing provides gross observations in these areas, the slit lamp can be used to examine the pupil and iris in more detail. Non-round pupillary shape can occur as a result of a surgical complication, posterior synechia from intraocular inflammation, or iris atrophy from age, ischemia, inflammation, or trauma. The red reflex provided when viewing through the direct ophthalmoscope can be helpful when comparing the two eyes. Observing pupil shape, location, and sizeĪ normal patient’s pupils should be round, symmetrical, and centered within the iris.
The equipment required to perform pupil testing is minimal: all you need is a millimeter ruler or pupillary gauge and a transilluminator (which is preferred over a disposable penlight due to the intensity of the light). If the patient is unable to see the 20/400 E, the red/green filter can be utilized over the optotype, and the patient should be instructed to fixate on the colors.Ī target that is too small for the patient might result in accommodation, with associated with pupillary constriction, which you will want to avoid when testing pupils. This article will focus on the proper procedure for testing pupils as well as point out some of the more commonly encountered pupil abnormalities.īefore testing pupils, the patient should be instructed to remove her spectacle correction.Ī distant, non-accommodative target two to three lines larger than the patient’s uncorrected visual acuity should be utilized. This procedure should be included as a component of every comprehensive examination or any time a patient needs to be dilated-in addition to any problem-focused visit involving eye health, such as a red eye visit, ocular emergency, or intraocular pressure (IOP) check.
Because of its potential to reveal serious retinal, neurologic or other disease, pupil testing is a crucial part of the ophthalmic examination and requires astute observation.
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