prism decentraion of astigmatic lens

[trace0526]

RE: +6.50/-4.00 *130
LE: +7.50/-5.00 *45

How to calculate the expected phoria at a near visual point 2mm in and 20mm down in both eye.

[Darryl Meister]

The mathematics are a bit tedious. It would be easier to use OptiCampus.com - Induced Prism or, since you are specifically interested in vertical imbalance at near, OptiCampus.com - Vertical Imbalance. According to the vertical imbalance calculator, these lenses require a net vertical prism compensation of 0.41 prism diopters base up, right eye, at 20 mm down and 2 mm in.

This would be the amount to order for a slab-off, although vertical imbalance compensation is really not necessary for this particular job.

Best regards,
Darryl

[chip anderson]

SV patients seldom if ever need a slab off or any sort of prism compensation. Especially vertically.