A glasses Rx is comprised of 3 numbers in order
Sphere
Reflects the degree of myopia / hyperopia
Can be minus (myopia) or plus (hyperopia)
Cylinder Power
Reflects the degree of astigmatism
At HEA it is always minus
Cylinder Axis
Reflects the axis of astigmatism
Add Power
This is for a reading prescription for older patients only
You will see this only in bifocal/trifocal or progressive glasses
Example
Note: You will see sph in the second place if there is no astigmatism
OD: -3.25 - 1.25 X 80
OS: -4.00 - sph
Single Vision
These are for only one distance (distance, computer, or near)
There are also over the counter (OTC) reading glasses (+2.50 is most common)
Bifocal
Has 2 zones (DV at the top and NV (add) at the bottom)
There is a distinct line separating the 2 zones
Trifocal
Has 3 separated zones (distance, intermediate, and near)
Progressive or PAL (Progressive Addition Lens)
Has distance, intermediate, and near blended together
You can read the add power under the green light by the lensometer
Note
Some glasses have prisms in them. If a person has double- vision due to an eye muscle imbalance, a prism can be put in the lens to realign the sight straight forward
This makes reading the glasses difficult! If the lensometer keeps jumping around, likely there is a prism in the lens
Soft CTLs
Majority of contact lens wearers use soft CTLs
They are convenient and pre-made
They are very comfortable and easy to get used to
Must be constantly replaced though
Hard CTLs
Can offer the best vision possible for high or unique prescriptions
Need to be custom made for the patient
Can be uncomfortable and take some time to get used to them
Can last for years if taken care of properly
Must be removed with a small plunger and use a special solution (Boston)
A CTL Rx will also have the following values for a proper fit
Base Curve (BC)
This is a measurement of the back surface of the CTL needed to properly fit the shape of the cornea
Diameter
The width of the CTL from edge to edge
Scleral Lenses
These are mainly for Keratoconus patients because the cornea is so steep, regular ones will not fit right and will slip off!
These are hard CTLs that rest on the rim of the Sclera and are filled with saline to fill the space in between the cornea and CTL
They must be custom made and fit to the patient's eye and can last for years
This measure the curvature of the cornea
It is similar to astigmatism, mut more precise and helps validate the degree of astigmatism
We get these from our auto refractor, but there are other machines that get them also (topographer/Pentacam)
It is very important for CTL fittings!
What are the numbers found in a glasses Rx?
What is an Add power?
What are progressive glasses?
What are bifocal glasses?
If the first number of my glasses Rx starts with -4.00 and I take my glasses off and look at mountains 10 miles away, how will they look?
What is a reason someone would wear hard CTLs as opposed to soft?
Why does a patient wear scleral lenses?
What are "Ks"?