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Eye Screening and Intractable Pain Management

Interpreting and using ocular signs, along with other physiologic markers, may be a useful tool in helping to evaluate medication levels in intractable pain patients.
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Clinical Corroboration of Opioid Undertreatment

If the pupil is dilated above about 5.0mm in diameter in subdued lighting conditions, you can be reasonably assured that there isn’t a high enough blood level of opioids to produce adequate pain relief. Undertreatment can commonly be corroborated with a blood pressure and pulse screen. Undercontrolled pain often drives the pulse rate above 88 per minute and/or the blood pressure over 130/90mmHg. Vasoconstriction is also a common component of uncontrolled pain, and this can simply be diagnosed by the presence of cold hands and feet. Diaphoresis may be obvious, or subtle. Excess watering can best be detected by gently rubbing the skin under the patient’s eyes.

Table 2. Opioid Ocular Signs
Situation Sign
Uncontrolled Pain Pupil dilates above 5.0mm in diame
Good Pain Control Pupil is between 3.0 and 5.0mm in diameter. Light reflex reaction is variable.
Excess Opioids in Blood Pupil constricts below 3.0mm in diameter and is non-reactive to a penlight challenge.
Opioid Withdrawal Pupil is dilated above 5.0mm in diameter and reacts briskly to a light challenge. May have photophobia.
Table 3. Drug Classes That May Cause a Slow or Non-Reactive Pupil, Non-Convergence, or
Benzodiazepines Muscle Relaxants
Anti-histamines
Anti-depressants
Anti-seizure agents
Anti-hypertensives

Ocular Signs of Opioid Over-Medication

Excess opioids in the serum that exceeds a patient’s tolerance is quite easy to diagnose. These patients—in contrast to those on sedatives and muscle relaxants—demonstrate simultaneous pupillary constriction below 3.0mm in diameter6,7 (see Figure 3) and non-reactivity of the pupil to a light challenge. When the constriction is about 1.0mm in diameter, it is often referred to as “pinpoint.” Excess opioids will also droop the upper eyelid and cause the pupil to be non-reactive to a penlight challenge and fail to accommodate an object—such as a pencil—when it is brought from a distance to about a foot from the nose.1 Normal accommodation would be progressive constriction of the pupil. Concomitantly, pulse and blood pressure will usually drop below the normal levels of 72 per minute and 120/80mmHg. As mentioned previously, sedatives, anti-depressants, and muscle relaxants, per se, will seldom cause the pupil to constrict below 3.0mm in diameter.

Summary

There is still such a bias against opioids in society that an obviously over-medicated pain patient is automatically assumed to have taken too many opioids. Since an opioid regimen produces tolerance within 24 hours after induction and significant tolerance after one week of administration, an over-medicated pain patient in ambulatory practice should be assumed, instead, to be taking too many non-opioid drugs. Chronic opioid administration, per se, produces little or no sedative or neurologic impairment on physical or mental function unless too many other compounds are concomitantly administered (see Table 3).

Uncontrolled pain, as well as opioid withdrawal, cause the pupillary diameter to dilate above 5.0mm while excess opioid administration above a patient’s tolerance causes the pupil to constrict below 3.0mm in diameter and be non-reactive to a light challenge. This finding is commonly known as “pinpoint.” Proper observation technique requires that room light be subdued.

Although few physicians may be aware of the usefulness of an eye screen, objective eye signs may be a valuable addition to routine opioid patient evaluation. Nevertheless, until one has looked at many eyes of pain patients, do not attempt to assign a diagnosis based only on eye signs. There is an art to the technique of screening for eye signs as well as a science in their interpretation.

Last updated on: March 22, 2011
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