Why do Optometrists write Rx’s in negative cylinder while Ophthalmologists use positive cylinder?

Last week I came across this question in a forum, which I have always wondered why, and leave it to the Optical Yoda, Van Rue to answer and allowed me to share: Ages ago, Cylinder was ground on the front of all lenses beginning around 1835, with sphere on the back… so Cyl was noted …

Why do Optometrists write Rx’s in negative cylinder while Ophthalmologists use positive cylinder? Read More »