Your glasses vs contact lens prescription may differ due to the distinct positioning of glasses and contact lenses relative to the eyes, necessitating specific information for each to ensure optimal vision correction and comfort.
Why the difference between glasses vs contact lens prescription?
Glasses are typically positioned approximately 12–14 millimetres away from the eyes whereas contact lenses rest directly on the cornea, eliminating the vertex distance present with glasses.
Vertex distance: The space between glasses and the eyes affects the effective power of the lenses. Contact lenses, sitting directly on the cornea, require adjustments to the prescribed power to account for the absence of this distance.
Fit and material considerations: Contact lenses must match the cornea’s curvature and size to ensure comfort, proper oxygen transmission, and to minimise the risk of complications. Therefore, additional parameters like base curve, diameter, and material are specified.
How do I read my contact lens prescription?
Most people get glasses before they get contact lenses, so you might already be familiar with how to read your glasses prescription 🔗. Similarly yet differently, your contact lens prescription will detail the measurements required of the contact lens in order for it to fit your eye and vision. It should outline the:
- Power of the lenses: Adjusted to account for the lack of vertex distance.
- Base curve: Ensures the lens conforms to the curvature of the cornea for proper fit.
- Diameter: Specifies the overall size of the lens to cover the corneal surface appropriately.
- Lens material: Indicates the composition of the lens, affecting oxygen permeability and comfort.
