Study
Drills
Rapid-fire practice on the calculations every exam repeats. Pick a set length, a difficulty and an optional time limit per question; build a streak, and every miss shows the worked answer. Answers follow the exam method.
Optical cross
ABO / NCLEPrescription to principal-meridian powers and back.
Not tried yet
Spherical equivalent
ABO / NCLESphere plus half the cylinder, fast.
Not tried yet
Prentice's rule
ABOPrism and base from a decentred optical centre, using the exam meridian table.
Not tried yet
Prism combine and resolve
ABOHorizontal and vertical prism to one resultant, and back.
Not tried yet