Ocular Pain Management

Posted by Dr. Hopkin

Eye care practitioners will not infrequently encounter patients in pain. This is most frequently due to disease of or injury to the cornea. The cornea is the most richly innervated tissue in the human body, with an average of 40 times more sensory nerves than tooth pulp and 400 times more than skin. Next time you have a patient in your chair complaining of debilitating pain from dry eye, remember that what they are experiencing could be significantly worse than your typical “toothache.”

Most often the pain we encounter is referred to as nociceptive (resulting from normal neural tissue response to insult) and is also usually acute. Neuropathic pain (resulting from adaptation and abnormal functioning pain receptors subsequent to tissue insult) is typically more chronic, more difficult to treat, and will often require consultation with a pain management specialist.

Prior to initiating treatments to help alleviate pain/discomfort, we should have a good understanding of the underlying condition causing the pain and treat it appropriately. We want to ensure we are treating the problem, not just masking the pain while the underlying problem worsens. As part of the history, we should not only grade the pain (e.g. 0-10 scale) but also have the patient describe the type of pain felt (e.g. sharp, stabbing vs dull, throbbing). As we treat the condition, a very important part of the patient’s recovery is a reduction in their level of discomfort.

A thorough history can identify potential allergens/toxins to which the patient may be exposed – often simply removing the offending agent is sufficient. Ask about contact lens wear-time, solutions used, other topical drops (over-the-counter or otherwise) the patient may be used, make-up and hygiene products, environmental situations, etc. It is also important to obtain a thorough medical history of systemic conditions (including problems with liver or kidneys), medications, and allergies to medications prior to treatment. You do not want to worsen an already frustrating condition by adverse drug interactions or an allergic response.

We can sometimes treat ocular pain with over-the-counter medications or prescription-strength topical medications. For those that experience “breakthrough pain,” stronger, oral, prescription-strength medication may be necessary. Fortunately, most cases of eye pain are acute and last less than 72 hours, so eye doctors do not have to (and truly, should not) handle long-term pain management. A short list of some of these problems may include corneal (or even conjunctival) foreign bodies and/or abrasions, post-surgery (surface debridement, PRK, pterygiumectomy, etc), severe dry eye, bacterial keratitis, severe EKC, herpes simplex keratitis, episcleritis, scleritis, uveitis, and preseptal cellulitis.

A notable exception is herpes zoster ophthalmicus, which can require some longer-term pain management with medications like gabapentin, carbamazepine, or pregabalin. When we are handling the care of a patient recovering from “shingles,” we do them a disservice if we are not addressing their post-herpetic neuralgia. These are good medications to use when co-managing patients with their primary care provider or pain management specialist. Care should be taken to ensure a keen understanding of their side effects, complications, and drug interactions. I do not address these medications specifically in this post.

For some issues of ocular pain, a bandage contact lens or ophthalmic ointments and lubricants may be sufficient to alleviate the patient’s discomfort. If these are insufficient or inappropriate treatments, our first line of pain management is often a topical solution/suspension. Compared to systemic medications, topical drops have the advantage of delivering the medication more directly to the affected area in higher concentrations and also have fewer and milder side effects due to minimal absorption into the bloodstream.

TOPICAL MEDICATIONS

While regular concentration (0.5%) proparacaine wonderfully masks corneal pain, we know that its toxicity and potential for abuse make it a poor choice to send home with patients. We do provide diluted proparicaine (about 0.05%) to patients following PRK during the re-epithelialization process to use no more than 6 times daily for breakthrough pain. This is a low enough amount to only rarely result in toxicity and can make the patient’s recovery much easier. We still caution patients about the potential for overuse and delayed healing if using this drop and to not use it unless there is severe pain.

Topical NSAIDs provide analgesic effects through inhibition of prostaglandin syntheses by blocking COX, which is responsible for the production of prostaglandins and other inflammatory mediators. This analgesic and anti-inflammatory effect can also help prevent pupil constriction, aiding to the overall comfort of the eye. Topical NSAIDs are indicated specifically for post-cataract surgery inflammation, so remember that any other use is off-label.

While earlier formulations of NSAIDs caused significant stinging or burning, the newer formulations are better tolerated and can also be used less frequently. If there is stinging, the patients can be encouraged to refrigerate the drops and/or “buffer” with artificial tears several minutes before using the NSAID. Our NSAID of choice is either Prolensa or Ilevro, depending on the patient’s insurance coverage and how thick we desire the drop (Ilevro is a much thicker drop on the eye). Watch for patients with allergies to or ones that have been instructed to not use other NSAIDs or ASA, as there is the potential for cross-sensitivity. Monitor patients very carefully if using an NSAID in the presence of any epithelial defect of the cornea.

In many cases, other topical agents, such as NSAIDs, corticosteroids, and cycloplegics will be adequate. Over-the-counter, oral acetaminophen and ibuprofen or naproxen can be taken separately or even together to help reduce inflammation and pain, as long as there are no contraindications for the patient to use these agents.

As mentioned, keeping the pupil from constricting can also reduce ocular discomfort. Cycloplegic agents can help relax ciliary spasms, reducing pain and potentially reducing intraocular inflammation as well. Relaxation of the ciliary spasm also stabilizes the blood-aqueous barrier, reducing the release of inflammatory mediators from the vasculature into the anterior chamber. Atropine (0.5%, 1%, or 2%) usually have some cycloplegic effect beyond one week, but usually not more than 10-12 days. Scopolamine 0.25%, homatropine (2% or 5%), and cyclopentolate (0.5%, 1%, or 2%) can be used BID to TID and have shorter duration than atropine. Consider longer-duration cycloplegics for severe iritis and shorter-duration for more acute corneal injuries.

When these topical treatments either fail or are known to be less effective, we can reach for topical corticosteroids. These should be approached less “cavalierly” than NSAIDs as they have a higher side-effect profile. Monitor patients on steroid regularly to ensure no IOP spikes. We all know from personal experience, that of the topical corticosteroids most frequently used, difluprednate 0.05% (Durezol) tends to cause the greatest spike in IOP, followed by prednisolone acetate 1% (PredForte), then fluorometholone, and lastly loteprednol (ester-based steroid available in 0.2%, Alrex, or 0.5%, Lotemax).

When treating a moderate to severe iritis or scleritis, we usually go straight to Durezol QID or even 6x/day until improvement is noted. A mistake often made by eye care practitioners is not using a strong enough steroid dosage to treat uveitis, thereby prolonging the recovery and possibly worsening potential sequelae. Durezol can usually be thought of to be as effective as prednisolone acetate at half the frequency. Usually, if there is true pain associated with inflammation, Durezol or PredForte will be the steroid of choice.

ORAL MEDICATIONS

Prior to initiating pain management with oral agents, ensure a detailed knowledge of other medications (including OTC medications), medication allergies, alcohol use, stomach ulcers, pregnancy/lactation, and the ability to metabolize and clear medications well (kidney or liver disease). Use extreme caution when prescribing medications to patients currently under the care of a cardiologist or psychiatrist – warfarin, digoxin, and many antidepressants often have interactions with a host of other medications.

Due to the lesser effect and over higher side-effect profile, we typically do not prescribe aspirin (acetylsalicylic acid, or ASA). We more frequently encourage patients to use acetaminophen (APAP) or ibuprofen, or sometimes naproxen. APAP is not contraindicated with pregnancy, blood dyscrasias, or in children (unlike ASA). It IS contraindicated, however, for those with liver disease, alcoholism, or hypersensitivity to APAP. When needed, APAP can be used for several days at a time at a maximum daily dose of 4g, though the minimum dosage necessary should be used to obtain pain relief. NSAIDs have the extra benefit of anti-inflammatory control and can be useful in addition to topical steroids for patients with iritis or even scleritis (we typically prefer indomethacin 50mg BID to TID, a stronger NSAID, for scleritis, though concurrent use of a proton pump inhibitor or H2-blocker, like Zantac 150mg BID, is a good idea). Ibuprofen and naproxen should be used at the lowest effective dose as well, at no more than 2400mg/day and 1250mg/day, respectively. Do not use NSAIDs with people that have known GI ulcers, alcoholism, if pregnant, or if hypersensitivity. For extra pain relief, patients may also take alternating APAP and NSAIDs, which anecdotally can have as much pain relief as low-dose hydrocodone, but without the drowsiness.

When these medications are thought to be insufficient to lessen patients’ discomfort, narcotics can be used with caution. In Texas, where we practice, optometrists can prescribe up to Schedule III narcotics for up to 72 hours to control pain. (Optometrists in Texas are also permitted the use of one Schedule II narcotic, but this is only for topical, diagnostic use and NOT for pain management.) The most useful for pain control within this scope are codeine and hydrocodone (read below for recent changes to hydrocodone scheduling). Consider also recommending docusate sodium (Colace) or another stool softener for patients that experience constipation while taking narcotics.

Sometimes patients report allergies to codeine when they may be only experiencing normal side-effects of the drug, which can include nausea, vomiting, and constipation (which can be reduced by taking with food and using a stool softener). Also, many report itching, flushing, and hives, which is another side effect of codeine (and its derivatives), which initiate a histamine release. True allergy or hypersensitivity to this medication would likely include trouble breathing, swelling of the lips or tongue, and/or hypotension.

For Rx-strength pain medication, some steps should be taken to further secure the Rx. Take some time to not only write in the number of tablets/capsules but also spell it out to prevent tampering. Refills should very clearly state “zero.” If you are handwriting the Rx, make sure sufficient patient information is of the Rx to prevent it being used for someone else. Do not hesitate to refer to other optometrists, ophthalmologists, or pain management specialists if you are uncomfortable working with these medications.

Codeine is the naturally occurring opioid and is less potent and causes more drowsiness than its semisynthetic derivative, hydrocodone, so it can be useful for mild to moderate pain relief, especially when sleep is desired as well. I rarely write for this medication, but when I have it has always been for Tylenol w/ Codeine #3, which is 30mg codeine with 300mg APAP. Patients can take 1-2 tablets every 4-6 hours, not to exceed 360mg/day of codeine (see above for maximum APAP dosage). Codeine is also available with ASA, but I never write prescriptions for this combination.

As I said, I rarely write for T #3. Many patients who need more pain management than OTC APAP and/or NSAIDs will also appreciate the increased pain relief that comes with hydrocodone. So when more pain control is needed for up to 72 hours, I have prescribed Vicodin. My practice of doing this, however, will need to change very soon due to a reclassification of hydrocodone as a schedule II narcotic.

A recent (10/24/2013) statement from Janet Woodcock, MD (Director, Center for Drug Evaluation and Research, FDA), stated, “By early December, FDA plans to submit our formal recommendation package to HHS to reclassify hydrocodone combination products into Schedule II. We anticipate that the National Institute on Drug Abuse (NIDA) will concur with our recommendation. This will begin a process that will lead to a final decision by the DEA on the appropriate scheduling of these products.” Though this may not go into effect for a longer period, I suggest that optometrists in Texas stop writing Rx for hydrocodone starting January 1, 2014. Therefore, for patients that would require oral medication stronger than those available OTC, I will either write for more Tylenol #3 or ask the ophthalmologists with whom I work to assist in the patient’s care.

Some states, including Kentucky, Arkansas, and Georgia, with Illinois pending, have taken steps to help pass laws that extend authority to prescribe hydrocodone combination drugs without regard to its schedule, allowing those that previously prescribed hydrocodone to continue to do so even following the schedule change. I am not aware of any current efforts by Texas optometrists to do the same.

Do not hesitate to refer to pain management specialists or trusted ophthalmologists for the use of stronger medications. Some patients truly do need superior pain relief available with oxycodone (Percocet or Percodan). Even though ophthalmologists can legally Rx these medications for longer than a 72-hour period, my experience is that most do not feel comfortable doing so without consulting with a pain management specialist. Especially oral medications must be approached cautiously, recognizing the potential not only for abuse but for interactions with other medications and exacerbation of medical problems. Advise those to whom you prescribe narcotics (and possibly even tramadol) to not drive or operate heavy machinery and also to not consume alcohol. Often the best solution involves the use of oral and topical medication together to help your patient feel better. We should also advise our patients that pain medication will help control pain, but likely not completely eliminate it. Most patients just need the reassurance and reduced anxiety that comes from some mild pain relief and the knowledge that their eyes will be okay.