A patient's complaint of pain serves as a cornerstone for a diagnostic framework. In this first of a yearlong series, two contributing editors discuss how to differentiate ocular and adnexal pain.

by Joseph W. Sowka, O.D. and Alan G. Kabat, O.D., Contributing Editors

First in a Series

It has long been an axiom of medicine that if you listen hard enough, the patient will always tell you what's wrong. Symptoms are the vocabulary of that message. You need to understand the myriad symptoms that a patient may present and use them as a starting point to construct your diagnostic algorithm. This series aims to help you in that effort. Over the next year we'll try to demystify ocular and adnexal symptoms and trace them to the disorders with which they're commonly associated.

First up: pain. Pain is a great motivating force, prompting patients to seek treatment when they might otherwise overlook the need for eye care. When someone presents with a painful eye, it's up to you develop a framework that will lead to a diagnosis. As you build that framework, start by looking at ocular and adnexal pain from a system level, and then identify those clinical entities associated with each system.

Pain often can be identified from the level at which it occurs. Ocular and adnexal pain occurs primarily due to dysfunction of the cornea, ocular coats (conjunctiva, episclera and sclera), uvea, associated nervous system or oculosystemic systems. Dysfunction of the retina, vitreous, or lens, on the other hand, will not precipitate pain. Thus, you can rule it out in such cases.

Cornea
Due to the high level of innervation of the cornea, even minimal dysfunction or insult can result in significant pain. Patients usually describe corneal pain as "sharp" or "stabbing." It is frequently severe. Associated photophobia, lacrimation, blepharospasm and vision loss are pathognomonic markers for corneal disease. You typically will see limbal vascular engorgement as well, but it may vary depending upon severity and associated factors.

Corneal abrasion will present with a history of recent trauma and typically severe pain. In your slit lamp exam, you'll see a telltale disruption of the epithelium with associated sodium fluorescein staining. Larger abrasions will more likely present with a greater degree of ocular pain due to concurrent secondary anterior uveitis. Recurrent corneal erosion will manifest in a similar fashion biomicroscopically, yet the pain occurs immediately upon awakening.

Corneal foreign bodies present with varying degrees of superficial pain. Small foreign bodies trigger a scratchy feeling that's exacerbated with blinking. Patients often can localize the sensation to a particular region of the cornea—for example nasal or superior. Larger and deeper foreign bodies present with more debilitating pain.

Infectious keratitis shows a disproportionately greater level of pain for the size of the ulcer. A diagnostic accumulation of stromal infiltration will identify an infectious process. The accompanying anterior uveitis contributes to the pain, which can be debilitating.

Punctate keratopathy—such as that seen with UV keratitis, toxic reactions or severe dry eye—can produce moderate to severe ocular pain. Also, the itching and burning that accompanies ocular surface disease and ocular allergies may be interpreted by the patient as pain.

A less common pain-causing condition is filamentary keratitis. Patients experience moderate pain that's exacerbated by blinking. Adhering to the epithelium are small mucous filaments that stain with sodium fluorescein, rose bengal or lissamine green dye. A chronic dry eye precedes filamentary keratitis and predisposes patients to this acute condition.

A clinical trick to differentiate corneal and conjunctival pain from that in deeper structures involves the use of a topical anesthetic. If a drop of proparacaine relieves the pain, then these superficial structures are implicated.

Ocular Coats 
The conjunctiva, episclera and sclera are much less innervated than the cornea. Therefore disorders of these ocular coats will present with less-severe pain than that which presents with corneal dysfunction. The patient's description of pain may vary from a foreign-body sensation to a mild dull ache. Deeper tissues present with a deep, boring pain because of their proximity to the highly innverated uvea. Often there will be vascular engorgement from inflammation, but there's usually no vision loss or lacrimation. Photophobia is also more likely with deeper tissue involvement. 

Conjunctivitis in and of itself is typically painless. However, pain in such cases would indicate associated corneal involvement and possibly a keratoconjunctivitis as a sequela of the infection. Pain can occur with conjunctival abrasions and lacerations, which obviously present with a history of recent trauma. These are far less painful than abrasions and lacerations of the cornea. The pain is typically scratchy and mild.

Inflammation of the underlying episclera can vary from a mild sensitivity to a moderate dull ache. Episcleritis is often sectoral, demonstrating focal vascular engorgement and an occasional overlying nodule in more severe cases. Scleritis brings more discomfort than episcleritis, causing a deep, boring ocular pain that may be severe and incapacitating. The associated vascular involvement in scleritis tends toward a diffuse purplish hue. You may also see inflammatory nodules. Associated secondary uveitis is more the rule than the exception, and peripheral keratitis may also occur with scleritis. 

Uvea 
Uveal dysfunction may present as a severe dull ache with associated photophobia, lacrimation and blepharospasm. This is due to the high level of sensory innervation within the anterior uveal tissues. The choroid, however, is far less innervated, so dysfunctions in this region usually are less painful. 

Anterior uveitis is one of the most painful ocular conditions. Significant photophobia strongly indicates this condition. Patients report a dull, boring pain that often radiates from the eye to the brow and temporal areas. Circumlimbal flush and an anterior chamber reaction of cells and flare are the hallmark signs of anterior uveitis. Posterior synechiae, hypopyon, keratic precipitates and peripheral anterior synechiae may accompany the presentation. Tonometry may reveal lowered or elevated pressures. By contrast, posterior uveitis is usually painless or minimally painful, although it's more likely to bring acute vision loss.

Acute primary angle closure presents with a classic clinical picture of a mid-dilated pupil, iris bombé, steamy corneal edema and a markedly elevated intraocular pressure. A dull and throbbing pain radiates throughout the head. It may be associated with nausea and even vomiting. The genesis of the pain entails disruption of the corneal nerves due to acute corneal edema. It bears mention that ocular pain is much more frequently encountered in these instances of abrupt IOP elevation. While similarly high pressures can happen in primary open angle glaucoma, the eye's compensatory mechanisms allow it to adapt to slowly elevating IOP, ruling out sequelae such as corneal edema.

Neovascular glaucoma presents with a dull ocular ache resulting from both ocular ischemia and rapidly elevating intraocular pressure. Associated iris and angle neovascularization are invariably present. Diabetes, retinal vascular occlusion and ocular ischemic syndrome are the most common etiologies underlying neovascular glaucoma.

Associated Nervous System
Pain-sensitive meningeal structures can contribute to ocular and adnexal pain. When the nervous system is involved in this way, patients experience a dull, boring and often-debilitating pain. Eye movements may initiate or exacerbate this pain. Patients often perceive it as a pain either within or behind the eye. Associated symptoms may include head pain, vision loss and diplopia.

Demyelinating optic neuropathy, sometimes referred to as optic neuritis, is most commonly associated with retrobulbar pain on eye movement. This is associated with multiple sclerosis. Here, the pain- sensitive dural meninges surrounding the optic nerve become inflamed. These tissues stretch with eye movement, causing significant ocular pain. Most of these patients report pain on eye movement as their chief complaint. Other associated findings include progressive vision loss, dyschromatopsia, visual field loss and a relative afferent pupillary defect in the affected eye.

Nerve palsies resulting from intracranial aneurysm typically affect the third cranial nerve. The patient will demonstrate exotropia, hypotropia and ptosis in the involved eye. The ipsilateral pupil will be dilated and unreactive to light. Because the aneurysm also impinges on pain-sensitive dural meninges, the patient will report a near-debilitating pain in the eye and head.

Also consider idiopathic inflammatory orbital pseudotumor and Tolosa-Hunt syndrome, two clinically similar conditions that can cause significant retro-orbital pain associated with ophthalmoplegia and diplopia. Chemosis, ocular congestion and proptosis commonly accompany these presentations. So readily do these conditions respond to oral steroids that you can consider a course of prednisone to be diagnostic.

Oculosystemics
Certain oculosystemic conditions can render pain in various tissues throughout the eye. The cause may not be obvious in all cases, but in those with multifocal pain, oculosystemic disease is often the etiology. The pain usually centers deep within the eye, but also radiates to the ipsilateral adnexa and face. 

Pain in the temporal region that seems to emanate from the eye is a frequent manifestation of giant cell arteritis, commonly seen in elderly patients. The patient typically has a constellation of systemic findings including (but not limited to) weight loss and anorexia, pain while chewing, scalp ulcers, night sweats and chronic flu-like illness with pharyngitis. There may or may not be vision loss on the involved side. If there is vision loss, it will typically be devastating and secondary to an anterior ischemic optic neuropathy.

One of the more confounding clinical presentations involves the prodrome of herpes zoster ophthalmicus. In this condition, patients may report a tingling or swelling sensation prior to the onset of the skin lesions. Once the herpetic vesicles erupt at the terminal points of sensory innervation, the pain becomes more severe and radiates from the eye to the face and head. It's crucial that these patients receive prompt diagnosis and treatment with oral antiviral medications to prevent post-herpetic neuralgia. This condition is extremely painful, often debilitating, and can be exceedingly difficult to control.

Finally, patients with ocular ischemic syndrome commonly manifest orbital pain, often describing it as deep and boring. The cause of pain is either neovascular glaucoma, ocular angina or dural ischemia. OIS, resulting from chronic insufficient blood flow to the eye due to carotid artery stenosis, may also manifest with iris neovascularization, cataract, anterior chamber reaction and mid-peripheral hemorrhages.

The site, duration and quality of ocular and adnexal pain are key criteria of clinical distinction. The patient's description of pain provides valuable diagnostic data. Listen closely and ask the right questions, and you're well on the way to the diagnosis.

Next month: red eye.

Drs. Kabat and Sowka are on faculty at the Nova Southeastern University College of Optometry, Ft. Lauderdale, Fla.