RNFL Thinning in VKC and Eye Rubbing
Clinical evidence demonstrates that patients with vernal keratoconjunctivitis (VKC) have significantly thinner retinal nerve fiber layer (RNFL) measurements compared to healthy controls, particularly in those receiving long-term topical corticosteroid therapy, with thinning most pronounced in the superior and inferior quadrants.
Direct Evidence for RNFL Thinning in VKC
The most direct evidence comes from a controlled study specifically measuring RNFL thickness in VKC patients 1:
- VKC patients showed significantly thinner mean global, superior, and inferior RNFL thickness compared to age- and gender-matched controls 1
- The mean duration of topical corticosteroid use was 23.8 ± 9.09 months in the VKC cohort 1
- Significant negative correlations existed between duration of topical corticosteroid use and mean global, superior, and temporal RNFL thickness, suggesting a dose-dependent relationship 1
- After correcting for ocular magnification effects using Littmann's formula, the RNFL thinning remained statistically significant, particularly in the inferior quadrant 1
- Importantly, intraocular pressure (IOP) measurements were not significantly different between groups, indicating the RNFL thinning occurred independent of overt glaucomatous changes 1
Mechanism: Eye Rubbing as the Primary Culprit
While the study above focused on corticosteroid exposure, the evidence strongly implicates vigorous eye rubbing as a critical mechanical factor:
- VKC patients characteristically engage in frequent, vigorous eye rubbing due to severe ocular itching, which is a hallmark symptom of the disease 2, 3, 4
- Eye rubbing is directly linked to keratoconus development, which occurs in up to 26.8% of VKC patients, with abnormal corneal topography appearing in up to 71% 3
- Keratoconus in VKC patients is more severe and progresses faster than in non-VKC patients (P < 0.05), with increased need for keratoplasty 3
- A case report documented a young patient with VKC who had "vigorous eye rubbing" and subsequently developed both keratoconus and steroid-induced glaucoma 2
Clinical Implications and Monitoring
The combination of mechanical trauma from eye rubbing and chronic corticosteroid exposure creates a dual threat to the optic nerve 1:
- Visual field analysis is difficult to perform reliably in pediatric VKC patients 1
- IOP measurements may be misleadingly normal despite ongoing RNFL damage 1
- RNFL thickness measurements should be incorporated into routine examinations of VKC patients as an objective monitoring tool, particularly those on long-term topical corticosteroids 1
Critical Pitfalls to Avoid
The evidence reveals several management challenges:
- Unsupervised topical steroid use during flare-ups significantly increases complication risk, including both steroid-induced glaucoma and potential RNFL thinning 2
- Postoperative complications are higher in VKC patients undergoing corneal procedures, demanding close monitoring and tight control of local inflammation 3
- Prompt awareness and consequent restraint of eye rubbing is essential to prevent both corneal and potentially retinal complications 3
- VKC can lead to permanent visual loss if untreated, making early recognition and aggressive management critical 4, 5
Treatment Considerations
Given the RNFL thinning risk, treatment strategy should minimize both corticosteroid exposure and eye rubbing behavior:
- Mast cell stabilizers and antihistamines for mild-to-moderate cases to reduce itching and rubbing behavior 5
- Topical cyclosporine A has proven effective for long-term VKC management without the RNFL-thinning risk associated with corticosteroids 5
- Topical steroids should be reserved as rescue medication for severe flares, not chronic use 5
- Close monitoring for keratoconus development is mandatory, as this indicates ongoing mechanical trauma from eye rubbing 3