What does absence of limbic (corneal) sparing indicate in a patient with ocular pain?

From the Guidelines

Lack of limbic sparing on eye examination in a patient with eye pain is a significant finding that suggests a more severe or systemic inflammatory condition, and according to the most recent study 1, it may be associated with neuropathic ocular pain (NOP), which can develop after ocular surgeries, postinfection, or as a result of chronic ocular surface abnormalities. The absence of limbic sparing is particularly concerning in cases of anterior uveitis, where it may indicate conditions such as granulomatous disease, sarcoidosis, or autoimmune disorders like rheumatoid arthritis. When examining a patient with this finding, it's essential to perform a thorough systemic evaluation, including laboratory tests for autoimmune markers and possibly imaging studies, as recommended by the study 1. Treatment depends on the underlying cause, but for NOP, topical nerve regenerative therapies, like autologous serum tears, or oral neuromodulators (e.g., pregabalin, gabapentin, duloxetine, amitriptyline, nortriptyline, low-dose naltrexone) may be used, as suggested by the study 1. The limbus contains stem cells crucial for corneal regeneration, so inflammation in this area can potentially lead to long-term corneal complications if not properly managed. Some key points to consider in the evaluation and management of patients with lack of limbic sparing and eye pain include:

• A thorough ocular surface and tear parameter examination to evaluate for nociceptive sources of pain
• Assessment of patients’ symptoms, including the use of questionnaires like the Neuropathic Pain Symptom Inventory (NPSI)-Eye or the Ocular Pain Assessment Survey (OPAS)
• The “anesthetic challenge test” to aid in localizing the pain
• Consideration of complementary therapies such as acupuncture, cognitive behavioral therapy, or hypnosis to address the emotional component of the pain. It is crucial to set up expectations early and encourage patients to continue the treatment even if they don’t feel immediate relief, as the study 1 suggests that all neuromodulators require time to take effect, with about 3 to 4 months at a therapeutic dose, to see a reduction in pain.

From the Research

Examination of Eye in a Patient with Eye Pain

• The term "limbic sparing" refers to the preservation of the limbic system, which is a complex system of nerves and networks in the brain, involving several areas near the edge of the cortex concerned with instinct and mood, and is closely associated with the olfactory senses 2.
• In the context of eye examination, "lack of limbic sparing" is not a direct term used in ophthalmology, but it can be related to the concept of altered intrinsic brain activities in patients with acute eye pain 2.
• A study using the amplitude of low-frequency fluctuation (ALFF) method found that acute eye pain patients had significantly lower ALFF in the left and right precentral/postcentral gyrus and left precuneus, and higher ALFF values in the right and left parahippocampal gyri and left caudate 2.
• The parahippocampal gyri are part of the limbic system, which suggests that the lack of limbic sparing in eye pain patients may be related to abnormal intrinsic brain activities in the limbic system 2.
• However, it is essential to note that the term "limbic sparing" is not directly related to ophthalmological examinations, and more research is needed to understand the relationship between limbic system activity and eye pain 2.

Ophthalmological Conditions

• Other ophthalmological conditions, such as superior limbic keratoconjunctivitis (SLK), can cause eye pain and inflammation 3.
• SLK is characterized by chronic inflammation of the superior limbus and superior bulbar and tarsal conjunctivae, and can be associated with other ocular and non-ocular conditions 3.
• The pathogenesis of SLK is still unknown, but it is thought to be related to mechanical injury, tear film instability, or an autoimmune/inflammatory etiology 3.
• Limbal stem cell deficiency (LSCD) is another condition that can cause eye pain and vision problems 4, 5.
• LSCD can be caused by various factors, including contact lens wear, ocular rosacea, and benzalkonium chloride toxicity 4.
• Treatment options for LSCD include medical therapy, such as topical corticosteroids and cyclosporine, and surgical interventions, such as simple limbal epithelial transplantation (SLET) 4, 5.