Tom's spectacles have a power of -12.00+0.50X 90. What would be the likely soft contact lens prescription for Tom?

To determine Tom's likely soft contact lens prescription based on his spectacle prescription of -12.00 +0.50X 90, it’s essential to understand how glasses prescriptions and contact lens prescriptions differ.

Contact lenses sit directly on the cornea, whereas spectacles are positioned further away from the eye. This distance affects the effective power needed. Typically, a spherical power adjustment is made when converting from glasses to contacts, accounting for the vertex distance.

In this scenario, Tom's spectacle prescription has a high minus component (-12.00). When converting to a contact lens prescription, especially for high myopia, a general rule is to reduce the spherical power slightly to achieve the correct vision correction because the lenses are closer to the eye. In this case, a decrease of around 1.00 to 1.50 diopters from the glasses prescription is typical, but factors such as the specific patient, fitting, and individual needs could adjust this slightly.

Opting for a prescription of -10.50 dpt as the likely soft contact lens prescription reflects a reasonable approximation based on the adjustments for vertex distance while ensuring that Tom still has adequate visual acuity. This adjustment affords a blend of clarity and comfort, making -10.50 dpt a