Ocular neuropathic pain

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Ocular neuropathic pain
Other namesCorneal neuralgia, keratoneuralgia, burning eye syndrome, neuropathic dry eye
Specialty Ophthalmology

Ocular neuropathic pain is a spectrum of disorders of ocular pain which are caused by damage or disease affecting the nerves. Ocular neuropathic pain is frequently associated with damaged or dysfunctional corneal nerves, [1] but the condition can also be caused by peripheral or centralized sensitization. [2] The condition shares some characteristics with somatic neuropathic pain [2] in that it is similarly associated with abnormal sensations (dysesthesia) or pain from normally non-painful stimuli (allodynia), but until recent years has been poorly understood by the medical community, and frequently dismissed by ophthalmologists who were not trained to identify neuropathic pain as a source of unexplained eye pain beyond objective findings noted on slit-lamp examination. [1]

Contents

This condition is frequently associated with dry eye disease since sensations of dryness and burning in the eye are a common symptom of both neuropathic eye pain and dry eye, but ocular neuropathic pain should be considered as a disease in its own right. [2] Neuropathic pain patients may have little or no signs of aqueous dry eye, and frequently respond poorly to conventional dry eye treatments. [3] Unlike conventional dry eye disease, there may be little or no sign of ocular surface damage, (the condition is sometimes referred to as "pain without stain" [3] ), however patients may also have symptoms of dry eye but with pain symptoms that are out of proportion to the dry eye presentation. [1]

The experience of painful sensations in this condition can vary widely, reflecting a variety of causal factors such as: types of noxious stimuli causing insult to ocular surface nociceptors, the types of corneal sensory receptors affected, (including cold-sensing thermoreceptors, mechanoreceptors, and polymodal receptors), the extent of the inflammatory responses, and the type or types of disorders and damage affecting the nervous system. [4]

Signs and symptoms

Symptoms of ocular neuropathic pain can range from devastating, unrelenting eye pain and severe sensitivity to light (photophobia) in the worst cases, to mild hyperalgesia or dysesthesia such as a sensation of dryness, stinging, or foreign body in milder cases. Mild neuropathic pain symptoms can appear similar to clinical symptoms of aqueous dry eye which can impede proper diagnosis. Sensations and levels of pain can vary depending on the source or sources of the maladaptive signals (eg. abnormal axonal regeneration, peripheral sensitization, etc). One or both eyes may be affected, with varying degrees of severity.

The sensation of pain has been described by patients as "burning eyes", "terrible, unrelenting pain", a feeling of "a knife in my eye" or "paper cuts". [5] The pain is usually described as being located in and around the eye, but can progress to the surrounding areas of the face and head. A signature characteristic of ocular neuropathic pain is inadequately explained levels of severe, constant pain in relation to little or no sign of ocular surface damage. Providers have reported their patients describing excruciating, consistently high levels of pain, or even requesting surgical removal of the painful eye. [6]

Cases of severe, refractory pain and related symptoms attributed to this condition have been described in medical publications. The severe and constant nature of the pain, as well as the difficulty in effective pain management are characteristics of severe cases. Oxford Academic described a case of a post-Lasik corneal neuralgia patient whose pain was refractory to years of aggressive ophthalmological and pain management treatments, and required surgical intervention to manage the constant, debilitating pain. Prior to surgery, the patient reported daily pain which varied from 6 to 10 on a numerical rating scale (where 0 signifies no pain and 10 the worst imaginable pain), depending on environmental factors. The pain was described as sharp, non-radiating, felt like paper cuts in both eyes, and the pain had persisted for 7 years prior to successful treatment with an implanted intrathecal pain pump. [7]

Comorbid conditions

A number of comorbid conditions have been identified which may predispose the patient to ocular neuropathic pain, including peripheral neuropathic pain, fibromyalgia, and Sjogren's Syndrome. [2]

Causes

Ocular neuropathic pain is a spectrum of disorders, the various clinical expressions of this disease are believed to reflect the complexity of overlapping networks of interactive pathogenetic cascades. [2] One or more causes may be shown to be present in a single patient through clinical examinations.

Corneal sensitization and evaporative hyperalgesia

Corneal sensitization and evaporative hyperalgesia occur as a result of trauma and environmental stress, the cornea has the highest density of nociceptors of any tissue in the body, and can become more sensitive to normal environmental stimuli. Predisposing factors to developing neuropathic pain include refractive surgeries (such as LASIK or LASEK) where it can occur as a result of aberrant nerve regeneration, tear dysfunction, blepharoplasty, excessive UV light exposure, chemical injury, and trigeminal zoster. [3]

Peripheral injuries and central sensitization

Peripheral injuries trigger complex changes in the central nociceptive system which can lead to central sensitization that enhances the sensitivity and responsiveness of the brain regions involved in sensory processing. In some cases, these physiological responses progress to neuropathic centralized pain. [2]

Treatments

Because the nerve damage and inflammation often originates in the ocular surface, conventional dry eye treatments including artificial tears are often the first line of treatment. A nonfenestrated scleral lens such as the Boston Ocular Surface Prosthesis (PROSE) can insulate the corneal surface from unwanted stimuli. Gabapentin and other neuropathic pain medications may be used to blunt sensory nerve stimulation or the perception of nerve stimulation. [1]

Recent publications have shown that neuro-regenerative therapies such as 20% autologous serum eye drops and topical nerve growth factor, and anti-inflammatory agents that minimize nerve injury and sensitization from uncontrolled inflammation (e.g., corticosteroids) can be effective in patients that have not responded to prior treatments. [8] For severe refractory ocular neuropathic pain cases where conservative treatments have proven ineffective, Intrathecal Targeted Drug Delivery with an implanted intrathecal pain pump has been used to successfully treat pain symptoms [7]

Related Research Articles

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Peripheral neuropathy Nervous system disease affecting nerves beyond the brain and spiral cord

Peripheral neuropathy, often shortened to neuropathy, is a general term describing disease affecting the peripheral nerves, meaning nerves beyond the brain and spinal cord. Damage to peripheral nerves may impair sensation, movement, gland, or organ function depending on which nerves are affected; in other words, neuropathy affecting motor, sensory, or autonomic nerves result in different symptoms. More than one type of nerve may be affected simultaneously. Peripheral neuropathy may be acute or chronic, and may be reversible or permanent.

Blepharitis Medical condition

Blepharitis is one of the most common ocular conditions characterized by inflammation, scaling, reddening, and crusting of the eyelid. This condition may also cause swelling, burning, itching, or a grainy sensation when introducing foreign objects or substances to the eye. Although blepharitis by itself is not sight-threatening, it can lead to permanent alterations of the eyelid margin. The primary cause is bacteria and inflammation from congested meibomian oil glands at the base of each eyelash. Other conditions may give rise to blepharitis, whether they be infectious or noninfectious, including, but not limited to, bacterial infections or allergies.

Dry eye syndrome Medical condition

Dry eye syndrome (DES), also known as keratoconjunctivitis sicca (KCS), is the condition of having dry eyes. Other associated symptoms include irritation, redness, discharge, and easily fatigued eyes. Blurred vision may also occur. Symptoms range from mild and occasional to severe and continuous. Scarring of the cornea may occur in untreated cases.

Neuropathic pain is pain caused by damage or disease affecting the somatosensory nervous system. Neuropathic pain may be associated with abnormal sensations called dysesthesia or pain from normally non-painful stimuli (allodynia). It may have continuous and/or episodic (paroxysmal) components. The latter resemble stabbings or electric shocks. Common qualities include burning or coldness, "pins and needles" sensations, numbness and itching.

Neuralgia is pain in the distribution of a nerve or nerves, as in intercostal neuralgia, trigeminal neuralgia, and glossopharyngeal neuralgia.

Fuchs dystrophy Medical condition

Fuchs dystrophy, also referred to as Fuchs endothelial corneal dystrophy (FECD) and Fuchs endothelial dystrophy (FED), is a slowly progressing corneal dystrophy that usually affects both eyes and is slightly more common in women than in men. Although early signs of Fuchs dystrophy are sometimes seen in people in their 30s and 40s, the disease rarely affects vision until people reach their 50s and 60s.

Artificial tears

Artificial tears are lubricating eye drops used to relieve dryness and irritation of the ocular surface. Dry eye syndrome is a common ocular surface disorder and is characterized by disruption of the tear film and increased inflammation.

Corneal ulcers in animals

A corneal ulcer, or ulcerative keratitis, is an inflammatory condition of the cornea involving loss of its outer layer. It is very common in dogs and is sometimes seen in cats. In veterinary medicine, the term corneal ulcer is a generic name for any condition involving the loss of the outer layer of the cornea, and as such is used to describe conditions with both inflammatory and traumatic causes.

Dysesthesia means "abnormal sensation". Its etymology comes from the Greek word "dys," meaning "bad," and "aesthesis," which means "sensation". It is defined as an unpleasant, abnormal sense of touch. It often presents as pain but may also present as an inappropriate, but not discomforting, sensation. It is caused by lesions of the nervous system, peripheral or central, and it involves sensations, whether spontaneous or evoked, such as burning, wetness, itching, electric shock, and pins and needles. Dysesthesia can include sensations in any bodily tissue, including most often the mouth, scalp, skin, or legs.

Corneal ulcer Medical condition

Corneal ulcer is an inflammatory or, more seriously, infective condition of the cornea involving disruption of its epithelial layer with involvement of the corneal stroma. It is a common condition in humans particularly in the tropics and the agrarian societies. In developing countries, children afflicted by Vitamin A deficiency are at high risk for corneal ulcer and may become blind in both eyes, which may persist lifelong. In ophthalmology, a corneal ulcer usually refers to having an infectious cause while the term corneal abrasion refers more to physical abrasions.

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Dejerine–Roussy syndrome or thalamic pain syndrome is a condition developed after a thalamic stroke, a stroke causing damage to the thalamus. Ischemic strokes and hemorrhagic strokes can cause lesioning in the thalamus. As initial stroke symptoms dissipate, an imbalance in sensation causes these later syndromes, characterizing Dejerine–Roussy syndrome. Although some treatments exist, they are often expensive, chemically based, invasive, and only treat patients for some time before they need more treatment, called "refractory treatment".

Nerve compression syndrome Human disease

Nerve compression syndrome or compression neuropathy, is a medical condition caused by direct pressure on a nerve. It is known colloquially as a trapped nerve, though this may also refer to nerve root compression. Its symptoms include pain, tingling, numbness and muscle weakness. The symptoms affect just one particular part of the body, depending on which nerve is affected. Nerve conduction studies help to confirm the diagnosis. In some cases, surgery may help to relieve the pressure on the nerve but this does not always relieve all the symptoms. Nerve injury by a single episode of physical trauma is in one sense a compression neuropathy but is not usually included under this heading.

Chemotherapy-induced peripheral neuropathy (CIPN) is a nerve-damaging side effect of antineoplastic agents in the common cancer treatment, chemotherapy. CIPN afflicts between 30% and 40% of patients undergoing chemotherapy. Antineoplastic agents in chemotherapy are designed to eliminate rapidly dividing cancer cells, but they can also damage healthy structures, including the peripheral nervous system. CIPN involves various symptoms such as tingling, pain, and numbness in the hands and feet. These symptoms can impair activities of daily living, such as typing or dressing, reduce balance, and increase risk of falls and hospitalizations. They can also give cause to reduce or discontinue chemotherapy. Researchers have conducted clinical trials and studies to uncover the various symptoms, causes, pathogenesis, diagnoses, risk factors, and treatments of CIPN.

Herpes simplex keratitis Medical condition

Herpetic simplex keratitis is a form of keratitis caused by recurrent herpes simplex virus (HSV) infection in the cornea.

Neurotrophic keratitis (NK) is a degenerative disease of the cornea caused by damage of the trigeminal nerve, which results in impairment of corneal sensitivity, spontaneous corneal epithelium breakdown, poor corneal healing and development of corneal ulceration, melting and perforation. This is because, in addition to the primary sensory role, the nerve also plays a role maintaining the integrity of the cornea by supplying it with trophic factors and regulating tissue metabolism.

Peripheral mononeuropathy is a nerve related disease where a single nerve, that is used to transport messages from the brain to the peripheral body, is diseased or damaged. Peripheral neuropathy is a general term that indicates any disorder of the peripheral nervous system. The name of the disorder itself can be broken down in order to understand this better; peripheral: in regard to peripheral neuropathy, refers to outside of the brain and spinal cord; neuro: means nerve related; -pathy; means disease. Peripheral mononeuropathy is a disorder that links to Peripheral Neuropathy, as it only effects a single peripheral nerve rather than several damaged or diseased nerves throughout the body. Healthy peripheral nerves are able to “carry messages from the brain and spinal cord to muscles, organs, and other body tissues”.

Exposure keratopathy is medical condition affecting the cornea of eyes. It can lead to corneal ulceration and permanent loss of vision due to corneal opacity.

Peripheral Ulcerative Keratitis (PUK) is a group of destructive inflammatory diseases involving the peripheral cornea in human eyes. The symptoms of PUK include pain, redness of the eyeball, photophobia, and decreased vision accompanied by distinctive signs of crescent-shaped damage of the cornea. The causes of this disease are broad, ranging from injuries, contamination of contact lenses, to association with other systemic conditions. PUK is associated with different ocular and systemic diseases. Mooren's ulcer is a common form of PUK. The majority of PUK is mediated by local or systemic immunological processes, which can lead to inflammation and eventually tissue damage. Standard PUK diagnostic test involves reviewing the medical history and a completing physical examinations. Two major treatments are the use of medications such as corticosteroids or other immunosuppressive agents and surgical resection of the conjunctiva. The prognosis of PUK is unclear with one study providing potential complications. PUK is a rare condition with an estimated incidence of 3 per million annually.

References

  1. 1 2 3 4 "Addressing the Pain of Corneal Neuropathy". American Academy of Ophthalmology. July 2010. Retrieved 2018-04-16.
  2. 1 2 3 4 5 6 Rosenthal, Perry; Borsook, David (2016). "Ocular neuropathic pain". British Journal of Ophthalmology. 100 (1): 128–134. doi:10.1136/bjophthalmol-2014-306280. PMC   4717373 . PMID   25943558.
  3. 1 2 3 "Pain without stain poses diagnostic and therapeutic dilemma" . Retrieved 2018-04-16.
  4. ↑ Kalangara, Jerry P.; Galor, Anat; Levitt, Roy C.; Felix, Elizabeth R.; Alegret, Ramon; Sarantopoulos, Constantine D. (2015). "Burning Eye Syndrome: Do Neuropathic Pain Mechanisms Underlie Chronic Dry Eye?". Pain Medicine. pp. 746–755. doi:10.1093/pm/pnv070. PMC   6281056 . PMID   26814296.Missing or empty |url= (help)
  5. ↑ "A Closer Look at Unexplained Eye Pain". Boston Eye Pain Foundation.
  6. ↑ "Addressing the Pain of Corneal Neuropathy". American Academy of Ophthalmology. July 2010.
  7. 1 2 Hayek, Salim M.; Sweet, Jennifer A.; Miller, Jonathan P.; Sayegh, Rony R. (2016). "Successful Management of Corneal Neuropathic Pain with Intrathecal Targeted Drug Delivery". Pain Medicine. pp. 1302–1307. doi:10.1093/pm/pnv058. PMID   26814286.Missing or empty |url= (help)
  8. ↑ "Neuropathic dry eye: When serum defeats tears". Ophthalmology Times. Retrieved 2018-05-02.
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