What are the treatment options for a patient with keratoconus?

Treatment Options for Keratoconus

Corneal collagen cross-linking (CXL) is the recommended treatment for progressive keratoconus because it stabilizes the cornea and reduces the risk of progressive ectasia, while specialty contact lenses remain the mainstay for visual rehabilitation, and keratoplasty is reserved for advanced cases unresponsive to conservative measures. 1

Initial Management and Visual Rehabilitation

Optical Correction Based on Disease Severity

Early keratoconus:

• Eyeglasses can correct vision in early disease, with 71% of patients achieving 20/40 or better vision 1
• Soft contact lenses (spherical or toric) may provide acceptable vision with greater comfort than rigid lenses in mild cases 1

Moderate to advanced keratoconus:

• Rigid gas-permeable (RGP) contact lenses are the primary treatment for visual rehabilitation, masking corneal irregularities by providing a regular anterior refractive surface 1
• In the Dundee University Scottish Keratoconus Study, 93% of contact lens wearers achieved best-corrected visual acuity of 20/30 or better with RGP lenses 1
• Hybrid contact lenses (rigid center with soft skirt) offer higher oxygen permeability and may improve comfort 1
• Scleral lenses should be trialed prior to keratoplasty and may delay or eliminate the need for corneal transplantation 1

Halting Disease Progression: Corneal Cross-Linking

Indications and Patient Selection

CXL is indicated for documented progressive keratoconus, defined by at least 2 of the following 1, 2:

• Steepening of the anterior corneal surface
• Steepening of the posterior corneal surface
• Thinning and/or increased rate of corneal thickness change from periphery to thinnest point

Documentation of progression requires serial topographic analysis comparing at least two examinations taken 3-6 months apart 2

Treatment Protocol and Efficacy

Standard Dresden protocol (FDA-approved) 3:

• Epithelial removal followed by riboflavin application
• UVA irradiation (370 nm, 3 mW/cm²) for 30 minutes
• Requires minimum corneal stromal thickness of 400 μm at time of UV exposure 4

Clinical outcomes from FDA phase III trials 3:

• Progressive keratoconus: Mean Kmax reduction of 1.4-1.7 diopters at 12 months in CXL-treated eyes versus 0.5-0.6 diopter increase in sham controls
• Post-refractive surgery ectasia: Mean Kmax reduction of 0.5-1.0 diopter versus 0.5-1.0 diopter increase in controls
• CXL stops deterioration and progression in the majority of patients, with long-term studies confirming stability beyond 36 months 1

Special Populations and Modified Protocols

Pediatric patients:

• Keratoconus presents more aggressively in children and requires closer follow-up (especially patients <17 years with Kmax >55D) 1
• Standard CXL is effective in halting progression at one and three years 1, 5

Thin corneas (approaching 400 μm threshold):

• Hypotonic riboflavin can transiently thicken the cornea to reach safety threshold 1, 4
• Sub400 protocols customize UV irradiation time based on corneal thickness 4
• Standard CXL is contraindicated when stromal thickness would fall below 400 μm after epithelial removal due to endothelial damage risk 4

Common Adverse Events

Expected sequelae following epithelial debridement 3:

• Corneal opacity/haze (most common, resolves by 12 months in most cases)
• Punctate keratitis, corneal striae, epithelial defects
• Eye pain, reduced visual acuity, blurred vision (typically resolve within 1-6 months)
• Corneal epithelial defects, edema, and scarring persist in 1-2% at 12 months

Adjunctive Measures to Prevent Progression

Patients must be counseled to refrain from eye rubbing, which is strongly associated with keratoconus progression 1

For patients with comorbid allergic eye disease 6:

• First-line: Cool compresses, preservative-free artificial tears, antihistamines, mast cell stabilizers
• Second-line: Topical cyclosporine 0.05-0.1% for moderate-to-severe allergic conjunctivitis
• Vernal and atopic keratoconjunctivitis should be controlled prior to CXL to decrease sterile keratitis risk 6

Surgical Interventions for Advanced Disease

Intrastromal Corneal Ring Segments (ICRS)

ICRS can be considered for patients with clear central corneas and corneal thickness ≥400 μm 4

• Creates more uniform corneal contour
• Improves uncorrected and corrected visual acuity
• Reduces high-order corneal aberrations and facilitates contact lens fitting 4

Keratoplasty

Penetrating keratoplasty (PK) and deep anterior lamellar keratoplasty (DALK) are reserved for advanced cases 1:

• DALK advantages: No risk of endothelial rejection, lower risk of globe rupture, less progressive endothelial cell loss compared to PK 1
• The long-term stabilizing effect of CXL may be more cost-effective than corneal transplantation 1
• European studies report significant reductions in keratoplasty rates since CXL introduction 1

Treatment Algorithm

1. All patients with suspected keratoconus: Obtain baseline corneal topography/tomography following contact lens abstinence 1

2. Documented progression: Proceed with CXL if corneal thickness adequate (≥400 μm after epithelial removal) 1, 2

3. Borderline thin corneas (400-420 μm): Consider hypotonic riboflavin or modified protocols; refer to specialist experienced in thin cornea CXL 4

4. Stable disease: Optimize visual rehabilitation with appropriate contact lenses (RGP, hybrid, or scleral) 1

5. Contact lens intolerance or advanced disease: Consider ICRS if cornea adequate thickness, or proceed to DALK/PK 1, 4

6. Younger patients (<30 years) or steep corneas (Kmax >55D): Monitor every 3-6 months for progression as these patients are at higher risk 1