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If your pupillary distance (PD) isn't on your prescription, please specify below.
SPH (Sphere)
Lens strength needed to correct your vision. Negative (-) means nearsighted, Positive (+) means farsighted.
CYL (Cylinder)
The degree of astigmatism in your eyes, as well as an axis number that indicates the orientation of the astigmatism.
Axis
The degree of astigmatism in your eyes, as well as an axis number that indicates the orientation of the astigmatism.
Pupil Distance
Pupillary distance, commonly abbreviated as PD, is the measurement in millimeters between the centers of the pupils of your eyes. This measurement is crucial for ensuring that the lenses of your glasses correctly align with your pupils, providing optimal vision clarity.
Add
ADD stands for the additional correction that you need for reading. It’s used for multifocal lenses and readers.
Prism
An eye prism in a prescription (Rx) is a special lens that helps correct visual alignment problems, such as double vision or eye strain. It works by bending light before it enters the eye, helping the eyes focus on the same object together, reducing issues like binocular vision disorders. Prism lenses are often prescribed for conditions like strabismus or convergence insufficiency.
Vertical prism
Vertical prism in an eyeglass prescription corrects vertical misalignment of the eyes, where one eye may drift higher (hypertropia) or lower (hypotropia) than the other. The prism shifts the image up or down, helping the eyes focus on the same point, reducing double vision and eye strain caused by the misalignment.
Direction Up/Down
Prism direction "up" (base up) and "down" (base down) refer to the vertical orientation of the prism in eyeglass lenses, used to correct vertical eye alignment problems:
These prisms help bring both eyes into proper vertical alignment, reducing double vision and eye strain.
Horizontal prism
Horizontal prism in an eyeglass prescription is used to correct eye alignment issues that cause the eyes to drift inward (esotropia) or outward (exotropia). The prism shifts the image left or right, depending on the prescription, helping the eyes work together to focus on the same point. This reduces double vision and improves binocular vision.
Direction In/Out
Prism direction "in" (base in) and "out" (base out) refer to the orientation of the prism in the eyeglass lenses, used to correct horizontal eye alignment issues:
The prism direction is tailored to each person's specific misalignment to help the eyes work together more effectively.
