GP lens eye Rounds

KERATOCONUS: Scleral Lens Standard Design Case

Emily Gottschalk OD, FAAO

History

• 29 y/o white male with a history of high myopia and astigmatism corrected with corneal gas permeable (GP) lenses with a wearing time of 10 hours/day x one month. He has been wearing spectacles since age two and has been a previous soft contact lens wear since age 12.
• CC: distorted vision including ghosting, glare with headlights, and blurred vision for 10 years. Significant improvement in quality of vision with corneal GP lenses without complete resolution of ghosting. Secondary CC: discomfort and irritation with current GP lenses.
• MHx: anxiety, depression, headaches, seasonal allergies. She quit smoking five years ago. Daily use of a nicotine vape.
• Medications: aripiprazole, trazodone, sertraline, hydroxyzine to treat anxiety and depression, and ibuprofen and sumatriptan to treat migraines.

Examination

• Entering visual acuities (VAs) with habitual corneal GP lenses
  • OD 20/30
  • OS 20/40
  • OU 20/30 NVA: OU 20/30
• Habitual corneal GP (keratoconic design) lens assessment OU:
  • Over-refraction plano OD and OS
  • SLE: OD: Inferiorly decentered interpalpebral flat fit with central bearing, fluorescein pooling surrounding area of bearing, excessive mid-peripheral bearing, and adequate edge lift 360 (Figure 1a).
    OS: Inferiorly decentered inter-palpebral flat fit with a central band of bearing, fluorescein pooling greater above than below the area of bearing, excessive mid-peripheral bearing, and adequate edge lift 360 (Figure 1b).
    Excessively flat fit bearing on cone apex OU

Figure 1: Fluorescein pattern of habitual corneal GP lens a) OD and b) OS.

• • Refraction:

OD -8.25 -9.25 x 163, 20/40+
OS -7.25 -8.75 x 011, 20/30-

• • Slit Lamp Examination OU:

• • Pentacam Corneal Tomography OD, OS (Figure 2)

• • Interpretation:
    • Front surface axial map: inferior corneal steepening
    • Elevation greater on the posterior float compared to the anterior float corresponding with the area of steepening.
    • Pachymetry map: thin area of less than 500um corresponding to the inferior elevated area.
  • Diagnosis:
    • The patient was diagnosed with bilateral keratoconus more advanced OD than OS.
  • Treatment and Management: Patient referred for corneal collagen crosslinking to decrease progression of corneal thinning. Scleral lenses were advised for improved comfort, lower risk of corneal scarring, and better corneal stabilization.

Fitting and Evaluation

• • Scleral lens diagnostic fitting with toric peripheral curve
    • Initial diagnostic lens selection:

• • • Diagnostic lens assessment:

• • Ordered lens parameters: Peripheral corneal zone was steepened by 100um to increase central clearance by 100um. The over-refraction was vertexed and incorporated into the new power.
  • Dispense visit:

Figure 3: Cross section showing central corneal vault of the scleral lens fit OD (a) and OS (b) with fluorescein.

The patient reported good comfort, excellent quality of vision, and no obvious ghosting or distortion.

Clinical Pearls

• • Complete a comprehensive evaluation for patients with unknown history. Early keratoconus diagnosis is crucial to allow for a prompt referral for crosslinking to slow progression of the disease.
  • Don’t hesitate to attempt a new lens design when there is an issue with another design. This patient was re-fit from a corneal GP to a scleral design for increased stability and comfort.
  • Initiating a lens fit prior to crosslinking may be needed to improve vision and, in this case, corneal health. The lens fit typically remains stable following crosslinking; however, educate the patient that modifications may be needed.