The Boxing System - Basic Measurements for Eyewear Flashcards
What is the name of the system measures the PD using a corneal reflex?
It is called both a Pupilometer and a PD meter.
What is the geometrical center distance of a frame marked 52/17?
69
True or false: In the boxing system, the effective diameter is the diagonal of the box.
False - the effective diameter is the longest possible diameter of the lens.
The larger the frame difference, the ____ the lens shape
Narrower - the chapter doesn’t discuss it, but the frame difference seems to be the difference between the A and B measurement. If this is incorrect, email me at b.richards.1701@gmail.com so I can correct it.
What is the DBL of a frame and how is it measured?
Distance Between Lenses - also known as bridge size, it is measured on the frame as the distance from the inside nasal eye wire grooves across the bridge area at the narrowest point.
True or false: If lenses are decentered in a frame by 4mm, this will also change the location of the geometrical center distance.
False - it changes the optical center of the lens, but the geometric center remains the same.
Before ordering prescription eyeglasses or even performing a visual examination what measurement must be determined?
The patient’s PD
When taking PD with a ruler, how far away should the optician be from the patient for a distance PD and then for a near PD?
40cm/16in for distance
At the patient’s working distance for near
When using a pupilometer, the cross hairline is adjusted to which point?
The center of the corneal reflex
Using Gerstman’s three-quarter rule, what is the near PD for a patient who has a distance PD of 64 with an rx of OU -1.00 sph, +2.50 add, and is using a working distance of 30cm?
Gerstman’s rule states that for every diopter of dioptric demand, the optical center or bifocal inset should be inset by 0.75mm. The dioptric demand can be found by taking the inverse of the working distance in meters, which is 1/.3 = 3.33. 3.33 x 0.75 = 2.49, or 2.5mm in both eyes. 2.5mm x 2 = 5 mm. 64 - 5 = 59. The near PD is 59.
The distance PD measures out to be 62mm, and the near PD calculates out to be 56mm. What is the seg inset per lens?
3mm
True or false: The limbal edge may be used as a reference point in taking monocular PDs.
False - it can be used to take binocular PDs, but not monocular PDs.
What is the max near working distance that should be measured when the add prescribed is +1.50? What would normally be chosen?
66cm is the max, 40cm is normal
True or false: The major reference point on a lens is also known as the optical center.
True
True or false: The major reference point on a lens is also known as the prism reference point.
True
