RNFL Thinning in Children with Allergic Conjunctivitis
The primary explanation for RNFL thinning in children with allergic conjunctivitis is long-term topical corticosteroid use, which shows a significant negative correlation with RNFL thickness independent of ocular magnification effects.
Primary Mechanism: Corticosteroid-Induced Thinning
The most direct evidence comes from children with vernal keratoconjunctivitis (a severe form of allergic conjunctivitis) who require chronic topical corticosteroid therapy. Children using topical corticosteroids for an average of 23.8 months demonstrated 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 corticosteroid exposure matters critically:
- Significant negative correlations exist between duration of topical corticosteroid use and mean global, superior, and temporal RNFL thickness 1
- This thinning occurs even when intraocular pressure remains normal, making it an insidious process that cannot be detected by IOP monitoring alone 1
Contributing Anatomical Factors
Beyond medication effects, children with allergic conjunctivitis often have associated refractive changes that independently contribute to RNFL measurements:
Myopic shift and axial length elongation are common confounders:
- Greater axial length is associated with thinner RNFL measurements 2, 3
- More myopic spherical equivalents correlate with reduced RNFL thickness (r = 0.5, P < 0.0001) 3
- Myopic children show RNFL thickness of 95.7 ± 10.3 μm compared to 102.5 ± 9.2 μm in emmetropic children 3
Children with vernal keratoconjunctivitis specifically demonstrate greater spherical equivalent and longer axial length compared to controls 1, which compounds the corticosteroid effect.
Clinical Implications and Monitoring
A critical pitfall is relying solely on IOP measurements, as RNFL thinning from chronic corticosteroid use can occur without elevated IOP 1. Visual field testing is unreliable in pediatric populations, making OCT-based RNFL monitoring essential 1.
The clinician should:
- Obtain baseline OCT RNFL measurements before initiating long-term topical corticosteroids in children with allergic conjunctivitis 1
- Monitor RNFL thickness serially during chronic corticosteroid therapy, particularly in the superior and inferior quadrants where thinning is most pronounced 1
- Account for age-related changes, as younger children naturally have thicker RNFL measurements 3
- Correct for axial length using Littmann's formula to avoid misinterpreting magnification artifacts as true RNFL changes 1
The inferior quadrant RNFL thickness difference persists even after magnification correction, making it a particularly reliable indicator of corticosteroid-induced damage 1.