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9 Articles in Volume 8, Issue #5
Chronic Pain and Substance Abuse
Eye Screening and Intractable Pain Management
Pain and the Brain
Postherpetic Neuralgia Pain and Laser Acupuncture
Prolotherapy for Golfing Injuries and Pain
Proposed Models of Fibromyalgia Sub-types
Realistic Pacing of Pain Patients’ Activities
Safe Analgesic Use in Patients With Renal Dysfunction
Superior Pharyngeal Constrictor Muscle Dysfunction

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.

A daily challenge to the pain physician who treats intractable pain is the proper regulation of serum medication levels. A key routine clinical assessment must be to document whether over-medication is present in order to prevent mental and physical impairments which may interfere with proper driving, climbing stairs, or performing work activities. Does the patient require a higher dose for good pain control? Or is the current dosage adequate? The patient is now on anti-inflammatory agents and states she/he needs something “stronger.” Could this be true? These are routine, common questions that constantly confront the physician who treats pain. A knowledge of how uncontrolled pain and medication levels affect the eye may be extremely helpful in answering the above questions. For example, a patient who has good opioid pain control—and who isn’t overmedicated with sedatives or muscle relaxants—will be able to converge their eyes and not demonstrate nystagmus, conjunctival reddening, or droopy eyelid.1

While the focus of this article will be regulating opioid dosage for intractable pain, it is critical to first assess medications in these patients. Pain patients usually take multiple drugs that may include antidepressants, sedatives, and muscle relaxants. A most unappreciated, pharmacologic fact is the great synergistic and potentiative capacity of benzodiazepines, muscle relaxants, some antidepressants, and some sedatives to interact with opioids and produce neurologic suppression. Although eye signs may not correlate to a specific drug, over-medication can usually be detected by screening for specific ocular signs. In particular, excess sedatives and muscle relaxants may cause these common eye signs:23

Table 1. Components of Rapid Eye Screening
Component Comments
Pupil size Normal is about 3.0 to 5.0mm in diameter.
Reactivity to a penlight challenge Constriction is normal unless there is excess of a muscle relaxant in the body.
Convergence Normally both eyes will converge to the middle and hold their gaze for 5 seconds when the patient tracts your finger or pen from a 1 foot distance.
Droopy Lid Normally the upper eyelid does not droop over the iris and touch the pupil.
Conjunctal reddening Due to blood vessel dilation after severe intoxication.
Nystagmus “Bouncing” of eye when they attempt to track laterally, vertically, or circularly is quite a non-specific test that is normal in some people and caused by numerous conditions other than drugs. Common with all sedatives, alcohol, and muscle relaxants.
Accommodation Pupil size will progressively constrict when the eye attempts to gaze at an object such as a pencil when it is brought close to the nose.
  1. Non-reactive pupil to light and accommodation
  2. Nystagmus
  3. Non-convergence
  4. Droopy upper eyelid
  5. Conjunctival reddening
  6. Watering

Since over-medication with benzodiazepines, muscle relaxants, and anti-depressants—commonly taken by pain patients—cause non-reactivity to a penlight challenge and lack of accommodation of the pupil, such ocular signs detected in a opioid patient may not be caused by the opioid itself. In fact, opioid over-medication in ambulatory pain practice is quite unusual. Why? Only about seven to ten days of opioid administration are required for the patient to become quite tolerant to opioids. Observation of overmedication is, therefore, usually due to benzodiazepines, muscle relaxants, sedatives, or other non-opioid drugs. The classic eye sign of non-opioid over-medication is a normal size pupil that fails to react to a light challenge.2,3 The key point is that only excess opioids routinely constrict the pupil below 3.0mm and simultaneously cause non-reactivity to a penlight challenge.

Proper Technique In Eye Screening

Pupil size and reaction can only be properly done in subdued room light.4,5 The fluorescent lights found in most medical facilities cause considerable pupillary constriction and interferes with a penlight challenge. A second critical point is that elderly patients may not be good candidates for eye screening. Ater about age 70, the pupil may become quite inelastic or even permanently contracted. Consequently, pupil size, accommodation, and light reflex testing may be inaccurate. Thus, as a consequence of the vagaries of room light, age changes in the eye, and multiple drug use, eye screening is not a precise science and should only be used to complement other clinical information rather than used as an absolute measure.

Yet, the pain-treating physician may still find great utility in ocular signs to diagnose over- or under-medication of opioids and other drugs. Components of rapid eye screening are presented in Table 1 and opioid-specific ocular signs in Table 2. With reasonable opioid control of intractable pain, the patient’s pupil remains in its normal range of about 3.0 to 5.0mm in diameter. A challenge with a penlight may give variable results, ranging from slow to non-reactive. A brisk constriction may suggest inadequate dosing or that an opioid is near the end of its therapeutic cycle. Fundamentally, this means the opioid blood level is marginal or too low.

Classic Eye Signs of Uncontrolled Pain

When acute or chronic pain reaches a critical threshold, it produces a profound sympathetic discharge in the autonomic nervous system. A part of the sympathetic discharge is dilation of the pupil. Thenormal diameter of the pupil is about 3.0 to 5.0mm1-6 (see Figure 1). Uncontrolled pain usually dilates the pupil above 5.0mm in diameter (see Figure 2). A dilated pupil, when concomitantly manifested with one or more other signs of sympathetic discharge—such as tachycardia, hypertension, diaphoresis, hyperreflexia, or vasoconstriction (cold hands and feet)—is strong, objective evidence of uncontrolled pain that needs treatment.3 The patient may also express subjective symptoms of chills, fever, insomnia, nausea, and anorexia. Interestingly, opioid withdrawal produces sympathetic discharge and the physical signs are essentially identical to those of uncontrolled pain.6,7

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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