Is allergic conjunctivitis associated with changes in retinal nerve fiber layer (RNFL) thickness?

Association Between RNFL and Allergic Conjunctivitis

Allergic conjunctivitis itself does not directly cause RNFL thinning, but two critical mechanisms can lead to RNFL damage in these patients: chronic topical corticosteroid use and vigorous eye rubbing.

Primary Mechanisms of RNFL Changes in Allergic Conjunctivitis Patients

Corticosteroid-Induced RNFL Thinning

Long-term topical corticosteroid therapy in allergic conjunctivitis patients causes significant RNFL thinning, particularly in the superior and inferior quadrants. 1

• VKC patients under chronic topical corticosteroid therapy demonstrate significantly thinner mean global, superior, and inferior RNFL thickness compared to age-matched controls, even after correcting for ocular magnification effects 1
• The duration of topical corticosteroid use shows significant negative correlations with mean global, superior, and temporal RNFL thickness 1
• This RNFL thinning can occur even when IOP measurements remain within normal ranges, making routine IOP monitoring alone insufficient for detecting glaucomatous damage 1

Because visual field testing is difficult to perform reliably in pediatric patients and IOP may be misleadingly normal, RNFL thickness measurements should be incorporated into routine monitoring of VKC patients on chronic topical corticosteroids. 1

Eye Rubbing-Induced Optic Nerve Damage

Vigorous eye rubbing from uncontrolled allergic conjunctivitis can cause mechanical compression and irreversible optic nerve atrophy. 2

• Chronic digital pressure from vigorous itching can lead to optic nerve damage severe enough to cause afferent pupillary defects and permanent vision loss 2
• This mechanism represents a direct mechanical injury rather than glaucomatous damage 2

Clinical Implications and Monitoring Strategy

When to Measure RNFL in Allergic Conjunctivitis Patients

RNFL thickness measurements are indicated in the following scenarios:

• Any VKC or atopic keratoconjunctivitis patient requiring topical corticosteroids for more than 2-3 months 1
• Patients with documented history of vigorous eye rubbing 2
• Baseline measurement before initiating chronic topical corticosteroid therapy 1
• Patients with coexisting risk factors for glaucoma (family history, elevated IOP, myopia) 3

Critical Monitoring Pitfalls to Avoid

Do not rely solely on IOP measurements to screen for corticosteroid-induced glaucomatous damage in allergic conjunctivitis patients, as RNFL thinning can occur with normal IOP. 1

• Visual field testing in pediatric VKC patients is unreliable and should not be the primary screening tool 1
• Baseline and periodic RNFL measurements should be obtained in addition to IOP monitoring and dilated fundus examination for cup-to-disc ratio assessment 3
• Patients using long-term topical corticosteroids require regular IOP checks, but also need stereo disc photography or OCT imaging of the RNFL to detect early optic nerve damage 3

Prevention Strategy

Adequate control of allergic symptoms is essential to prevent both mechanisms of RNFL damage:

• Use dual-action topical agents (olopatadine, ketotifen, epinastine, or azelastine) as first-line treatment to minimize need for corticosteroids 4
• Counsel all patients to avoid eye rubbing, as this is critical to prevent both keratoconus progression and optic nerve compression 3, 4
• Consider topical cyclosporine 0.05% or tacrolimus for severe vernal/atopic conjunctivitis to reduce corticosteroid dependence 3
• Employ general strategies to minimize corticosteroid use, including allergen avoidance, cool compresses, and preservative-free artificial tears 4

Referral Indications

Refer to ophthalmology when:

• Suspected vernal or atopic keratoconjunctivitis requiring chronic corticosteroid therapy 4
• Any vision changes or corneal involvement 4
• Disease uncontrolled with topical medications and oral antihistamines 4
• Documented RNFL thinning on OCT imaging 1