Have you ever looked at your glasses prescription and wondered what it all means? It’s random numbers and a few letters here and there. You’ve been wearing the glasses prescribed by your optometrist in Canberra, and perhaps now is the time to understand what it all means.
OD and OS: It’s All Greek to Me!
- OD stands for “Oculus Dexter” – This is your right eye…in Latin
- OS means “Oculus Sinister” – This is your left eye.
- OU is “Oculus Uterque” – This means both eyes.
Sph (Sphere)
This number shows how strong the lenses are to correct your myopia (near-sightedness) or hypermetropia (farsightedness). These are measured in dioptres (D) and 0.25 increments.
- A plus (+) sign is a hyperopic correction
- A minus (-) sign is a myopic correction
The higher the number, the stronger the prescription.
CYL (Cylinder) and Axis
These two always come in pairs.
- CYL is the power of astigmatism that is corrected. Astigmatism is when your cornea is oval compared to round (think a rugby ball compared to a soccer ball). This number is also measured in dioptres in 0.25D increments.
- Axis is 0 to 180, showing where that astigmatism correction is. If you think of your eye as a clockface, the axis is the position of the astigmatism correction on the clock.
Suppose your optical prescription has a high CYL value or a constantly changing axis. In that case, regularly seeing your optometrist in Canberra is essential to eliminate any corneal diseases that may significantly change the overall astigmatism value.
ADD
This refers to the additional lens power we need to read (generally as we get older). In multifocal lenses, for example, this is the extra power required at the bottom of the lens to enable us to read clearly. Over-the-counter “chemist” glasses generally use this value only, without considering any other values that comprise the part of your optical prescription. Although the chemist glasses are still better at assisting you with the ability to read, patients often find them uncomfortable if they are used after a long period.
PRISM
Sometimes, a prism is needed to ensure people see a single image. Sometimes, patients with misaligned eyes experience doubling, such as a turned eye or a squint. This is relevant in children, who need well-aligned eyes for their vision development. When prisms do not fully correct the issue, your optometrist in Canberra may refer you to an eye specialist for consideration of strabismus surgery. The prism relates to the amount necessary and the prism base’s direction (the prism’s thickest part). Base-up (BU), Base-down (BD), Base-out (BO), Base-In (BI).
Your optometrist may also write additional notes on the prescription specific to you and your glasses, such as the lens type they recommend.
Pupillary Distance
This measurement often relates to how far apart your eyes are or the distance between the centre of your pupils. This measurement allows your optician or the preferred optical laboratory used by your optometrist in Canberra to centre your lenses correctly. The lens centration is essential to ensure your new glasses are comfortable.
We do not advocate taking this measurement yourself since, depending on your optical prescription, being 0.1mm out could cause issues adapting to your new glasses or the overall comfort of vision.
The Bottom Line
Your optical prescription is unique to you. Hence, the new spectacles you ordered through your optometrist in Canberra are unique to you. Therefore, swapping glasses with your colleagues, although they may seem like they work at first, could lead to uncomfortable vision and eye strain after a prolonged period. There are many more measurements outside your prescription to consider when we make a pair of new glasses for you.
We understand the importance of taking these measurements accurately. Thereby, at Capital Eye, we have invested in technology such as our optical dispensing CR Tower to ensure your glasses are fitted correctly.
If it has been a while since you’ve updated your prescription, consider visiting your optometrist in Canberra. You would be amazed at what you can achieve with your vision, even with a slight tweak to your optical prescription.