Chapter 6 Ordering and Verification

Standards for spheres up to 6.50

+/- 0.13

ANSI standards for seg height

+/- 1mm

Standards for spheres above 6.50

+/- 2%

Standards for cyl power 2.00 or less

.13

Standards for cyl power b/t 2.00 and 4.50

.15

For 0.00 to 2.75 lenses with horizontal prism, what is the prism tolerance

0.67 total OU

What do you do if PD and current Rx OC's do not match?

1. get a hold of original rx b/c it may be due to a prism 2. If that is not an option, use OC's in original glasses. * If rx is very small, use PD you get b/c prism effect will be very small.

Standards for cyl axis when power is 0.25

14 degrees

Standards for cyl axis when power is 1.75 and above

2 degrees

Near PD should be within

2.5mm

For above 2.75 lenses with unwanted horizontal prism, what is the max distance off PD

2.5mm. It has to be within this range of the ordered, or it fails.

Standards for cyl axis when power is 1.00, 1.25, 1.50

3 degrees

If lens defect is outside ____ circle of MRP or within ____ of lens edge, it's okay

30mm 6mm

Standards for cyl above 4.50 is

4%

Standards for cyl axis when power is 0.75

5 degrees

Standards for cyl axis when power is 0.50

7 degrees

To convert b/t + and - cyl

Add the sphere and cylinder powers. This is the new sphere power. Change the sign of the cylinder from plus to minus or from minus to plus. This is the new cylinder value. Add or subtract 90 from the cylinder axis. This is the new cylinder axis.

Things you can do to existing frames to make them hypoallergenic

Clear coating, or thin shrink tube over temples. Also, do not use glue to hold lenses in frame that contain latex

What do you use to check for strain on a lens

Colmascope

When converting to highest meridian as the sphere, what do you do if the cyl is twice as much as the sphere

Convert to other notation if one is plus and one is minus

How do you measure vertical OC?

From the edge of the bevel to the OC mark. This is the same thing as measuring the MRP(major reference point).

How do you measure segment size

From the widest portion

How to write an Rx so that the highest meridian is the sphere power

If both sphere and cyl signs are the same convert to the other notation. If not, leave as is.

If OC is different b/t lenses for unwanted vertical prism

If prism is greater than 1/3rd prism diopter, respot lens. Then check to see if the marks are 1 mm apart. Must match both criteria to fail.

If a lens has a high cyl, how do you find OC's

Line up sphere in OC, then focus cyl lines and line them up. Keep going back and forth until you no longer need to move the lens

If ordering one lens, must get

MRP OU and if MF match seg heights with old Rx and MRP's

Method 2 for checking if prismatic effect is less than 0.67

Mark OC, find where PD should be, Move lens so that you are going from 0 prism to a higher prism. Stop when you reach 1/3rd. Repeat OS. If distance b/t these new dots does not reach wearers PD, they fail.

Method 1 for checking if prismatic effect is less than 0.67

Mark where OC should be and measure.

How do you determine what a lens material is

Measure the thickness at the OC

What is needed when order one lens for an existing pair

OC

How do you find OC of the second lens measured?

Only line it up horizontally. If it is off vertically make a note of the resulting vertical prism using the circles in the lensometer. Spot it twice, where it is, and where it should be.

When using the auxiliary prism, which base direction should it go

Opposite of the prism base direction in the glasses

Hypoallergenic frame materials

Optyl material,Polyamide/Copolyamide,Titanium, Stainless steel

ANSI for dress wear are _____

Recommendations

ANSI for safety wear are _____

Requirements

Which lines should come into focus first

Skinny (sphere), doesn't matter if you are doing + or - cyl

How to verify prescribed prism

Start with lens that is highest in 90 degree. Put rx in lensometer. Position lens for prescribed prism, spot.

How to get final prism amount with auxiliary prism

Take what you get in glasses and add to the aux lens. Keep the base of the glasses prism

A box o graph is used to measure what

The A dimensions of a lens

What is the C size

The circumference of the lens

What is a base curve?

The front curve of a multi focal lens. Try to keep pt. in same BC if the lens powers did not change to avoid distortion

What to do when measuring large prism

The larger prismatic component is read from the prism compensating device. The smaller prismatic component is read directly from the reticle.

Which lens to you read first?

The one with the highest rx (+ or -) in the vertical meridian. If both are similar and they have a vertical prism, use the one with the highest prism.

How to measure and add

Turn glasses around to get front vertex power of the add and the OC. BUT take measurement above optica center. The add is the difference b/t the two.

What is the prism reference point?

Where the OC's should have been

How to measure segment height

from the bevel to the top of the segment

The farther away you get from the OC the more _____

prism