MYOPIA MANAGEMENT: Diagnostic Testing
Jessica Liaw OD, FAAO
Refraction
- US Food and Drug Administration (FDA) approval for up to -5.00D to -6.00D (de pending upon the design) myopia. Partial correction may benefit for higher myopia1
- FDA approval for up to -1.50D to -1.75D astigmatism
- With-the-Rule (WTR) astigmatism < -1.50D is easier to fit
- Oblique or Against-the-Rule (ATR) astigmatism likely not a good candidate as the lenses tend to decenter laterally
Keratometry
- Ideal candidates have flat K readings of 40.00-46.00D
Topography
- Limbus-to-limbus astigmatism and sagittal elevation differences guide lens toricity
Horizontal Visible Iris Diameter (HVID)
- Lens diameter is crucial for centration. The overall diameter is typically 10-11mm to allow for 90-95% corneal coverage
Pupil Size
- Treatment zone is typically a diameter of 5-6 mm. Patients with larger pupil sizes may experience diminished vision quality due to increased glare, as the treatment zone may not fully cover their pupil in low-light conditions.
Sources
- Lyu T, Wang L, Zhou L, Qin J, Ma H, Shi M. Regimen Study of High Myopia-Partial Reduction Orthokeratology. Eye Contact Lens. 2020 May;46:141-146.