I have a question about prism and vertical imbalance using a patients O.C. ht vs where their eyes sit vs what the seg ht is.


For example: rx o.d. -5.00 -2.00 x 162
o.s -3.00 -3.00 x 097 add +3.00 o.u.

seg ht is 18mm, eyes sit at 25mm and the reading level is 14mm.

I know you have to solve for the lens power at 90degr meridian.

o.d.=-6.81 o.s.=-3.04

Where should I go from here?

Normally I would simply take the reading level and multiply by power at 90degrees and divide by 10.

prism o.d.=(6.81 x 14)/10=9.5 prism bd

prism o.s.=(3.04 x 14)/10=4.3 prism bd

VI=5.2prism

but what about the prism for the eyes sitting higher than the distance o.c., which I figure to be 4mm above seg ht. (18+4=22mm)

So eyes at 25mm and o.c. at 22mm. we have a 3mm difference still.

I hope Darryl is around. Thank you :hammer: