Formulas

Question 1

Minimum amplitude of accommodation

Answer 1

Minimum = 15 - (1/4) age
* fail if 2.00 D or more below

Question 2

Normal NRA

Answer 2

+2.00 (+/- 0.50D)
* negative relative accommodation

Question 3

Accommodative convergence/ accommodation

Answer 3

AC/A ratio = PD + near (near phoria - far phoria)

PD= pupillary distance (centimeters)
Near= near distance (meters)

(-) exo
(+) eso

Question 4

What is the dioptric equivalent of a lens that has a base curve of 8.3mm?

Answer 4

Convert BC from mm to diopters

337.5/8.3 =40.663 40.66 D

Question 5

What is the formula to calculate Seg inset for bifocals?

Answer 5

(Distance PD - near PD)
———————————
2

Question 6

How to calculate vergence demand

Answer 6

Demand = target separation/ training distance

Target separation in cm
Training distance in meters

Example: variable tranaglyphs when separation is 4cm at a distance of 80cm
Demand = 4cm/ 0.80 m =5 PD