ABO NOCE Basic Opticianry Frame Measurements and the Boxing System

Question 1

In the boxing system of frame measurement, what does the 'A' measurement represent?

Accepted Answer

The horizontal width of the lens opening (eye size)

Answer

The vertical height of the lens opening

Answer

The distance between the two lens openings

Answer

The effective diameter of the lens

Question 2

The DBL (Distance Between Lenses) in the boxing system is measured from:

Accepted Answer

The nasal (innermost) edge of one lens opening to the nasal edge of the other

Answer

The geometric center of one lens to the geometric center of the other

Answer

The optical center of one lens to the optical center of the other

Answer

The temporal edge of one lens to the nasal edge of the other

Question 3

Using the boxing system, the frame geometric center distance (frame PD) is calculated as:

Accepted Answer

2A + DBL

Answer

A + DBL

Answer

A + 2(DBL)

Answer

A × DBL

Question 4

What is the 'effective diameter' (ED) of a lens frame, and why does it matter?

Accepted Answer

The diameter of the smallest circle that fully contains the lens shape; used to determine minimum blank size

Answer

The A × B measurement product; used to determine total lens area

Answer

The diagonal of the boxing rectangle; used to verify the lens fits the tracer

Answer

The distance from the boxing center to the optical center; used to calculate induced prism

Question 5

A patient's monocular PDs are 32 mm OD and 31 mm OS. The frame has an A measurement of 52 mm and a DBL of 18 mm. What is the decentration (in mm) required per eye?

Accepted Answer

OD: 3 mm in, OS: 4 mm in

Answer

OD: 0 mm, OS: 0 mm — no decentration needed

Answer

OD: 4 mm in, OS: 5 mm in

Answer

OD: 1 mm out, OS: 2 mm out

Question 6

When a patient's interpupillary distance is SMALLER than the frame's geometric center distance, the optical centers must be decentered in which direction?

Accepted Answer

Nasally (inward), to align with the pupils

Answer

Temporally (outward), to follow the pupils

Answer

Superiorly, to reduce induced vertical prism

Answer

No decentration is required because the power compensates automatically