Nomi Optical Guide
How to Read Your Optical Prescription
Demystifying your vision parameters for a tailored, flawless visual experience.
Navigating Your Prescription Grid
Optometrists record vision corrections using standardized optical codes. Below is an example of a typical prescription slip showing where key values are positioned:
Right Eye
Short for Oculus Dexter (Latin for Right Eye). Values on this row apply to your right lens.
Left Eye
Short for Oculus Sinister (Latin for Left Eye). Values on this row apply to your left lens.
Sphere (SPH)
The core focal power needed to correct shortsightedness (-ve) or longsightedness (+ve), measured in Diopters (D).
Cylinder (CYL) & Axis
The correction needed for astigmatism (CYL), and the exact degree angle (Axis, 1° to 180°) of this correction.
Reading Addition (ADD)
The magnification power required for reading or near vision, which is usually equal in both eyes.
Prism & Base Direction
Prismatic power (Prism \(\Delta\)) and directional orientation (Base In, Out, Up, Down) prescribed to correct eye alignment or double vision (strabismus/diplopia).
Transposing Plus (+) Cylinder to Minus (-) Cylinder
Ophthalmologists sometimes write prescriptions in Plus Cylinder format. Nomi uses standard optical Minus Cylinder format. To convert your prescription:
2. New CYL = - (CYL)
3. New Axis = (Axis + 90°) % 180° (if > 180, subtract 180)
Example: SPH +1.00, CYL +0.75, Axis 80° → Transposes to SPH +1.75, CYL -0.75, Axis 170°.
More Information on Sphere Values
Shortsightedness (Myopia)
Negative Sphere Values mean that you are short sighted (myopia). Close objects are clear, but the further the distance objects are, the blurrier they become.
The higher the negative number (away from 0.00 / Plano), the stronger the correction needed (e.g. -4.00 is stronger than -1.25).
Longsightedness (Hyperopia)
Positive Sphere values mean you are long sighted (hyperopia). Distance objects are clearer, but close up objects, reading, or screens can be blurry or cause eye strain.
The higher the positive number (away from 0.00 / Plano), the stronger the correction required (e.g. +3.50 is stronger than +1.00).
What is Plano (0.00 / PL)? Plano indicates zero distance sphere correction is needed. If your SPH column says Plano or 0.00, your distance vision does not require spherical power.
Prescription Precision & Validity
Peak Manufacturing Precision
Our lenses are manufactured with peak optical precision in full compliance with Australian Standards (AS/NZS ISO 21987), ensuring your glasses are crafted accurately to your exact prescription specifications.
Prescription Expiry & Patient Rights
Under Australian professional standards, prescriptions are valid for 1 to 2 years from eye test date. Your registered optometrist is legally obligated to provide a copy of your prescription upon request.