What are the treatment options for corneal aberrations?

Treatment Options for Corneal Aberrations

Corneal aberrations should be treated with a targeted approach based on the depth and type of aberration, with phototherapeutic keratectomy (PTK) being the most effective treatment for anterior corneal aberrations and rigid gas-permeable contact lenses for managing irregular astigmatism. 1

Non-Surgical Management Options

• Rigid Gas-Permeable (RGP) Contact Lenses: First-line treatment for corneal aberrations causing irregular astigmatism, as they mask corneal irregularities by providing a regular anterior refractive surface. A trial fitting with spectacle overcorrection can be performed in-office to demonstrate potential improvement. 1

• Hybrid Contact Lenses: Contain a rigid gas-permeable center with a soft skirt, providing comfort while correcting aberrations. Useful when greater stability is needed. 1

• Scleral Contact Lenses: Particularly beneficial in severe cases with advanced aberrations or scarring where soft or RGP lenses are difficult to fit due to irregular corneal surface. These lenses can also help assess visual potential in severe cases. 1

• Painted Contact Lenses: Available with a clear pupillary zone and opaque periphery for patients with peripheral opacities when visual potential is poor. 1

Surgical Management Options Based on Depth of Aberration

For Epithelial and Subepithelial Aberrations

• Epithelial Debridement: Effective for lesions anterior to Bowman's layer (e.g., epithelial basement membrane dystrophy, recurrent erosions). Complete epithelial removal is performed until the smooth Bowman's layer is exposed, followed by application of a bandage contact lens and prophylactic antibiotics. 1

• Management of Subepithelial Fibrosis: For conditions like Salzmann nodular degeneration, a corneal burr and/or PTK can be used to smooth the surface and reduce optical aberrations. 1

For Anterior Stromal Aberrations

• Phototherapeutic Keratectomy (PTK): Most beneficial for corneal opacities limited to the anterior 10-15% of stromal thickness. Can improve epithelial stability and visual acuity in conditions such as:

  • Epithelial basement membrane dystrophy
  • Bullous keratopathy
  • Anterior stromal scarring
  • Residual subepithelial haze after removal of band keratopathy or Salzmann nodular degeneration
  • Corneal dystrophies (Reis-Bücklers, granular, lattice) 1

• Topography-Guided Custom Ablation Treatment (TCAT): Effective for regularizing corneal surfaces and reducing higher-order aberrations in post-traumatic corneal irregularities. Can be combined with mitomycin C application to prevent haze. 2

• Mitomycin-C Application: Used as an adjunct to PTK to diminish recurrent scar tissue or stromal deposits. Applied on a circular sponge to the corneal stroma after laser treatment, followed by copious irrigation to reduce toxicity risk. 1

For Deeper Stromal Aberrations

• Anterior Lamellar Keratoplasty (ALK): For deeper stromal aberrations, ALK performed using a microkeratome or femtosecond laser can achieve a smoother bed than freehand dissections. 1

• Superficial Corneal Flaps with Excimer Laser Ablation: Can be performed to remove anterior-to-mid-stromal opacity when the overlying stroma is clear. 1

Special Considerations

• Masking Agent Technique for PTK: When treating irregular surfaces with PTK, a masking agent (methylcellulose or sodium hyaluronate) should be used to fill valleys so peaks can be ablated first, preventing etching of surface topography into underlying layers. 1

• Post-PTK Complications: Be aware of potential hyperopic shift and posttreatment surface irregularity. Treatment to deeper levels is associated with higher-order aberrations and irregular astigmatism. 1

• Corneal Tattooing: For cosmetically objectionable corneal leukomas, creation of a lamellar pocket or flap into which pigment is instilled can be considered. 1

Treatment Algorithm

1. Assess depth and type of aberration:

   • Superficial (epithelial/subepithelial): Consider epithelial debridement or PTK
   • Anterior stromal (10-15% depth): Consider PTK with or without mitomycin C
   • Deeper stromal: Consider ALK or lamellar keratoplasty 1

2. For irregular astigmatism without significant opacity:

   • Start with RGP or scleral contact lenses for visual rehabilitation 1
   • If contact lens intolerance develops, consider PTK or TCAT 2

3. For aberrations with opacity:

   • Determine depth with AS-OCT, UBM, or confocal microscopy
   • Choose appropriate surgical technique based on depth 1
   • Consider mitomycin C application for cases with high risk of recurrent haze 1

4. Post-treatment management:

   • Monitor for recurrence of underlying disease process
   • Address any hyperopic shift or irregular astigmatism
   • Consider bandage contact lens and prophylactic antibiotics 1

Key Pitfalls to Avoid

• Overtreatment with PTK: Can lead to significant hyperopic shift and irregular astigmatism. Limit treatment to anterior 10-15% of stromal thickness when possible. 1

• Inadequate Mitomycin C Management: Improper use can lead to stromal melt and ocular surface toxicity. Ensure copious irrigation after application. 1

• Ignoring Biomechanical Impact: Deeper treatments may affect corneal biomechanics, potentially leading to progressive ectasia. Consider corneal thickness and topography before treatment. 1

• Neglecting Higher-Order Aberrations: Vertical coma is the most elevated higher-order aberration across all irregular cornea types and should be specifically addressed in treatment planning. 3