A soft lens patient with a spectacle correction of +8.50D at a vertex of 12mm would have the most appropriate sphere power of?

To determine the most appropriate sphere power for a soft lens patient, it is essential to consider the effect of the vertex distance on the prescription. In this scenario, the spectacle correction is +8.50D at a vertex distance of 12mm. When fitting contact lenses, the prescription often needs to be adjusted to account for the closer fitting of the contact lens to the eye, as contact lenses sit directly on the cornea, which can alter the effective power required.

In general, as the vertex distance decreases, the power required in a contact lens increases for hyperopic prescriptions. A prescription of +8.50D at 12mm suggests that when correcting vision without the lenses, there is a need for a higher plus power due to the vertex distance being considerably greater than that of contact lenses.

To find the appropriate sphere power, an adjustment is typically made. For each millimeter of vertex distance, the power will adjust approximately 0.25D. With the vertex distance of 12mm, the effective power when switching to contact lenses requires calculating this adjustment.

Considering the specifications given, a power of +9.50D would be the necessary adjustment to achieve optimal vision with soft contact lenses based on the degree of hyperopia