What is a Corneal Cyst?
A corneal cyst is a fluid-filled cavity within the corneal tissue, typically lined by epithelial cells, that can occur in various corneal layers and may cause progressive visual impairment through opacity or irregular astigmatism.
Types and Location
Corneal cysts can be classified based on their anatomical location:
- Intrastromal epithelial cysts: These occur within the corneal stroma and are lined by epithelial cells with features similar to limbal corneal epithelium 1
- Corneoscleral cysts: These span both corneal and scleral tissue at the limbal region, often with a communication between the two components 2, 3
Etiology
The origin of corneal cysts varies:
- Traumatic: Most commonly develop after relatively minor ocular trauma, with epithelial cells becoming implanted into the corneal stroma 1
- Iatrogenic: Can result from surgical seeding of limbal corneal epithelium during procedures such as strabismus surgery 4
- Developmental: Some corneoscleral cysts contain ectopic lacrimal tissue elements, suggesting a congenital developmental origin 3
Clinical Presentation
Corneal cysts typically present with characteristic features:
- Appearance: Opalescent or translucent lesions that may demonstrate a fluid level within the cavity 1
- Progression: Slowly progressive disorder developing over many years, particularly in younger patients 1
- Visual symptoms: Decreased best-corrected visual acuity when the cyst encroaches on the visual axis 4, 5
- Inflammation: The eye typically shows no signs of inflammation 1
Diagnostic Evaluation
Diagnosis relies on clinical examination and imaging:
- Slit-lamp biomicroscopy: Essential for identifying the cyst location, size, and characteristics 5
- Anterior segment OCT: Provides high-definition cross-sectional imaging to determine the depth and extent of the cyst 5
- Cytologic analysis: Confirms the diagnosis by demonstrating intact and degenerated epithelial cells within the cyst contents 4
Treatment Approach
Surgical intervention is indicated when the cyst causes documented visual impairment or demonstrates progressive growth toward the visual axis 4, 5:
- Minimally invasive drainage: A partial-thickness clear corneal incision allows cyst incision, debridement, and wall scraping 4
- Distilled water irrigation: Injection of distilled water into the cyst cavity (left for 5 minutes then aspirated) destroys residual epithelial cells and reduces recurrence risk 2, 5
- Chemical ablation: Application of 20% trichloroacetic acid to the cyst lining epithelium provides effective epithelial destruction 3
- Lamellar keratosclerectomy: For corneoscleral cysts, excision of the limbal epithelial nest with lamellar corneal grafting prevents recurrence 5
Prognosis and Outcomes
Treatment outcomes are generally favorable:
- Visual improvement: Best-corrected visual acuity typically improves significantly after surgical treatment, with cases improving from 20/100 to 20/30 5
- Recurrence: Proper epithelial cell destruction minimizes recurrence risk, with stable results documented at follow-up periods ranging from 12 to 21 months 2, 4, 5
- Complications: Small white granular opacities (epithelial cell nests) may persist at the interface of the collapsed cyst cavity but do not typically affect visual function 2
Key Clinical Pitfalls
Watch for these important considerations:
- Incomplete epithelial removal: Failure to completely destroy or remove the epithelial lining leads to cyst recurrence 1, 5
- Central corneal involvement: Cysts approaching the visual axis require prompt intervention to prevent irreversible amblyopia in pediatric patients 4, 5
- Endothelial damage: Surgical techniques should minimize risk to the corneal endothelium, with distilled water irrigation showing no significant change in central endothelial cell density 2