**Distance Between Lenses** (DBL) – The shortest distance between the nasal edges of each lens or the distance between boxes. DBL is also commonly referred to as bridge size.

How do you measure the DBL of a box?

- Hold
**the**ruler over**the**frame front and sight an imaginary line from**the**farthest edge of a box touching**the**left temporal lens edge of**the**right eye to**the**right edge of**the**box. That’s**the**A dimension. Next, measure**the DBL**or “bridge” size.

## What is DBL measurement?

DBL ( distance between lenses ) is the horizontal linear measurement between the innermost edge of the right lens and the innermost edge of the left lens while glazed in a frame.

## How is DBL frame measured?

Hold the ruler over the frame front and sight an imaginary line from the farthest edge of a box touching the left temporal lens edge of the right eye to the right edge of the box. That’s the A dimension. Next, measure the DBL or “bridge” size.

## What is DBL for glasses?

The number on the right hand side of the square box is the “Bridge Size” and is sometimes referred to as the “DBL” ( distance between lenses ). This is the distance between the two lenses measured in millimetres (see DBL in the diagram below).

## What is the SEG drop?

The distance from 1 to 3 — the midline of the lens to the top of the segment — is called seg drop. It equals the (seg height) – B/2. The distance from 2 to 4 — the widest points of the seg — is called seg width.

## What does 53 16 on glasses mean?

A first number is a two-digit number that is 53, which represents the eye size. It is the horizontal width of the lenses. If you take a look at your eyeglass frame, you will see that the first number will be from 40 mm to 62 mm. A second number is also a two-digit number that is 16, which represents the bridge size.

## What’s the difference between 52 and 54 glasses?

Lens width is measured from left to right at the widest point in the lens. Between a 52 and 54 eyesize, the 54 will have a wider lens so the whole frame will be wider too. The lens will also be a little taller to preserve the shape. The bridge and temple measurements will usually remain the same.

## What does 51mm mean in glasses?

The first two numbers represent the width of the lens (51 means a lens width of 51 mm.) The second two numbers are the distance be- tween the bridge, the area between the two lenses that arches over the nose (17 means a DBL of 17 mm.) The last four numbers of the order number (3011) are the color.

## What is GCD in lenses?

Geometric Center Distance (GCD) The distance between the two geometric centers of the lenses is known as the geometric center distance (GCD). Or the geometric center distance can be calculated by simply adding the eye size to the DBL.

## What is Eye Bridge Temple?

Bridge Size – measurement is the distance in millimeters between the two lenses. It is measured between the two closest points of the two lenses. Temple Size – is measured along the length of the temple, from one end to the other, including the bend.

## What is frame PD?

The “frame PD” is the A box measurement plus the DBL measurement. This is equal to the distance from the center of the left lens opening to the center of the right lens opening, on a horizontal line.

## What is a box o graph used for?

Box-O-Graph: A tool used in labs to measure lenses and frames.

## What is major reference point?

MRP stands for the Major Reference Point. It is the point in the lens giving the exact prescription called for. For non-prism prescriptions, the MRP and the optical center (OC) of the lens are the same.