Keratoconus: Evaluation and Treatment Approach
For keratoconus management, start with corneal topography/tomography for diagnosis, use eyeglasses or contact lenses for visual correction based on disease severity, and perform corneal cross-linking (CXL) when progression is documented to prevent vision loss—this is the only treatment that halts disease progression and should be prioritized in younger patients. 1
Diagnostic Evaluation
Essential Imaging Studies
Document keratoconus using corneal topography and tomography to assess:
- Anterior corneal surface steepening
- Posterior corneal surface steepening
- Corneal thickness changes (thinning patterns)
- Best spectacle-corrected distance visual acuity 1
The ABCD classification system (integrated into Scheimpflug imaging) provides standardized staging from 0-4 for each parameter and tracks progression effectively 1.
Documenting Progression
Progression requires at least 2 of the following:
- Steepening of anterior corneal surface
- Steepening of posterior corneal surface
- Progressive thinning or increased rate of thickness change from periphery to thinnest point 1
Critical caveat: Younger patients progress faster—early detection and treatment are crucial in this age group 1. Monitor every 3-6 months rather than annually, especially in younger patients 1.
Treatment Algorithm by Disease Severity
Early/Mild Keratoconus
Start with eyeglasses: 58-71% of patients achieve 20/40 or better vision with spectacle correction 1. If vision deteriorates below 20/30, advance to contact lenses.
Moderate Keratoconus
Rigid gas-permeable (RGP) contact lenses are the mainstay: 93% of patients achieve 20/30 or better corrected vision 1. Use steep-fitting rather than flat-fitting lenses for superior visual outcomes 1.
Alternative contact lens options when RGP fails:
- Hybrid lenses: 87% success rate in RGP-intolerant patients, combining rigid center with soft skirt 1
- Scleral lenses: Increasingly used with advances in design 1
- Soft contact lenses: Only for very mild cases with minimal irregular astigmatism 1
Common pitfall: 71% of contact lens wearers experience discomfort; don't abandon contact lens fitting prematurely—try alternative designs before proceeding to surgery 1.
Corneal Cross-Linking: The Disease-Modifying Treatment
When to Perform CXL
Perform CXL when progression is documented to halt disease advancement—this is FDA-approved and the only treatment that stops keratoconus progression 1.
Key evidence: Phase III FDA trial showed maximum keratometry decreased by 1.6 ± 4.2 D in treated eyes versus continued progression in controls, with improved corrected distance visual acuity 1.
Special Consideration for Pediatric Patients
In children/adolescents (ages 10-16), consider CXL as first-line treatment when progressive disease is confirmed 1. The KERALINK study demonstrated CXL stopped progression in the majority of young patients at 18 months 1. While some propose immediate treatment without awaiting progression documentation, it remains reasonable to confirm progression first to avoid unnecessary treatment and satisfy insurance requirements 1.
CXL Technique
FDA-approved Dresden protocol:
- Remove corneal epithelium
- Apply topical riboflavin every 2 minutes for 30 minutes
- UV-A light treatment for 30 minutes with continued riboflavin application 1
Contraindication: Corneal stromal thickness <400 μm at UV exposure (risk of endothelial damage) 1. Hypotonic riboflavin can transiently thicken corneas below this threshold.
Emerging alternatives: Transepithelial ("epithelium-on") techniques reduce complications from epithelial removal but may decrease efficacy—evidence is still evolving 1.
CXL Outcomes
- Halts progression (primary goal achieved) 1
- Corneal flattening of 1.0-2.5 D 1
- Improved uncorrected and corrected vision 1
- Reduced need for corneal transplantation 1
- Transient endothelial cell count reduction (normalizes by 6 months) 1
Surgical Intervention for Advanced Disease
Indications for Keratoplasty
Proceed to corneal transplantation when:
- Functional vision cannot be achieved with eyeglasses and contact lenses
- Persistent corneal edema following hydrops
- Deep stromal scarring with contact lens intolerance 1
Technique options:
- Deep anterior lamellar keratoplasty (DALK): Lower rejection rate than penetrating keratoplasty (PK) (OR = 0.28), similar graft failure rates 1
- Penetrating keratoplasty: Preferred for deep stromal scarring where perforation risk is high during lamellar dissection 1
Follow-Up Strategy
Monitor every 3-6 months (not annually) to detect progression early, especially in younger patients 1. Each visit should include:
- Visual acuity measurement
- Slit-lamp biomicroscopy
- Corneal topography and tomography for contour/thickness assessment 1
The goal is identifying progression before significant vision loss occurs, enabling timely CXL intervention to preserve vision and quality of life 1.