A guide to prescription lenses

A guide to prescription lenses

The first question that you might be asking, is how do I know which lens type to choose?

Which lenses you need will depend on your prescription.

There are broadly four different types of optical lenses:

Single vision lenses are the most common, and provide correction for one field of vision. For most people this will either be distance, or near (reading).
Ready readers provide simple magnification power for reading. No prescription is required.
Non-prescription clear lenses are ready to wear and can be changed by a local optician if required. These are also known as ‘plano’ lenses.
If you need to correct more than one field of vision - for example both distance and near vision - we also offer progressives, otherwise known as varifocals. These also allow you to see the intermediate areas in between clearly such as your computer and car dashboard.

Cubitts offers comprehensive eye examinations, both for prescriptions and general eye health

If you wear glasses, you've probably seen that piece of paper with a series of numbers and abbreviations that your optometrist hands you after your eye exam. Understanding your glasses prescription is crucial for ensuring you get the right lenses to correct your vision. In this article, we'll provide a comprehensive guide on how to read your glasses prescription, breaking down the numbers and terminology so you can confidently choose the perfect pair of glasses.

Understanding your prescription.

OD and OS - Right and Left Eyes: Your prescription is typically divided into two parts, with the right eye labeled as "OD" (oculus dexter) and the left eye as "OS" (oculus sinister). Sometimes, you may also see "R" and "L" instead of OD and OS. Occasionally, if the prescription is the same for both eyes, you'll find "OU" (oculus uterque) or "BOTH."
Sphere (SPH): The sphere, or SPH, indicates the main lens power needed to correct your vision. A positive number (+) signifies farsightedness (hyperopia), and a negative number (-) represents nearsightedness (myopia). The higher the number, the stronger the prescription.
Cylinder (CYL): If you have astigmatism, your prescription will include a cylinder value (CYL). This measures the degree of astigmatism and is written as a negative or positive number.
Axis (AXIS): The axis indicates the angle in degrees at which the cylinder power should be oriented to correct astigmatism.
Addition (ADD): The addition value (ADD) is relevant for bifocals or progressive lenses and represents the additional power required for reading or close-up tasks. This is usually a positive number.
Prism and Base (PRISM and BASE): Prism and base values are specified if you have eye alignment issues, such as double vision. The prism value indicates the displacement of the image, and the base tells the direction of the displacement (up, down, in, or out).
Pupillary Distance (PD): The PD is the distance between the centers of your pupils and is crucial for ensuring that your lenses are correctly centred in your frames.

Example Glasses Prescription:

OD (Right Eye): -2.00 SPH, -0.75 CYL, 75 AXIS

OS (Left Eye): -1.75 SPH, -1.25 CYL, 110 AXIS

ADD: +2.25

A vintage illustration of the eye's many layers

Another question that might arise, is how do I know which thickness of lens to choose at checkout?

As well as the type of lens, you can choose the ‘index’ of lens. Your lens index refers to how thin the lens will be when cut for your frames. There are a few things to consider when choosing the right lens index for your new spectacles.

Firstly. take a look at your prescription and check the numbers under SPH and CYL. If the number under CYL is higher than 1.5 or is written in a + format rather than a - format, it’s best to get in touch with our Customer Experience or Store teams, who can help you out.

Each prescription is unique and the lens you should choose depends on how big the lens is in the frame style you’ve chosen.

The general rule here is that if the SPH number is around +/- 3.75, or 2.5 in a large or super lightweight frame the standard thinning we include in the price of our frame will work for you.

When this SPH number goes above +/- 4, or 3.5 in a large or super lightweight frame, consider the second level of thinning. That’s a 1.67 index.

If you have a SPH +/- 6 or higher this likely means you’ll need to come into one of our stores to have extra measurements taken and opt for the thinnest lenses, which are a 1.74 index.

Each and every prescription is glazed to size using the MEI edging machine

Digital eye strain can be an issue, although there's no scientific evidence that blue filter lenses can help with this. Indeed, we get more exposure to blue light from the sun than we do from computers and smartphones. It's not the blue light that's making your eyes feel bad, it's staring at the screen for hours without a break.

One of the main causes of eye strain is actually glare, so it's important you have lenses with an anti-reflective coating. Thankfully all Cubitts’ lenses come with this as standard. Blue filter lenses can potentially be useful at night when blue light from screens can disrupt natural sleep patterns. Our bodies associate blue light with daytime, so being exposed to it when you're trying to go to sleep can push our internal clocks later, meaning it's harder to doze off. Our advice is that if you have trouble sleeping it might be worth trying blue filter lenses, this isn't dissimilar to ‘Night Mode’ on an iPhone, so we do suggest trying that first. Or even trying (brace yourselves) to reduce your screen time before you go to sleep. We use ZEISS Blueguard lenses (+£50) which filters up to 40% of blue light whilst offering full UV protection. The blue light filtering technology is built into the lens as opposed to a coating on the surface, resulting in fewer blue reflections for a more aesthetically pleasing look.

Blue light filter is available online, and in store for +£50.

Polarised lenses have a built-in filter to reduce glare caused by horizontal light. They’re ideal for activities around water, where light reflection causes glare. So worth considering if you’re into activities such as fishing, surfing, sailing, or levitating on water.

They are also a great option for driving, you'll experience greater visual clarity and contrast, less glare, and more relaxed vision.

Polarising lenses can sometimes affect the viewing of LCDs, so something to bear in mind when wearing them.

Polarisation is available online, and in store for +£50.

Light reactive lenses (also known as Transitional lenses) contain photochromic dyes that cause the lens to activate, or darken, when exposed to ultraviolet rays from sunlight. This means that your lenses automatically become ‘sunglasses’ when you’re out and about. Light reactive lenses offer the convenience of sunglasses without having to switch between the two.

We use ZEISS Photofusion X, the latest generation of photochromic lenses from Zeiss. Much faster than previous lighht reactive lenses, they are perfectly clear indoors and dark outdoors, providing sunglass level UV protection and a unique level of blue light blocking.

Photochromic lenses do not react inside cars as UV protection is already built into the windshield. If you're looking for a dark lens for driving, you will need a separate sunglass pair or a clip on.

Light Reactive lenses are available online and in store in Grey, Green, or Brown up to 1.67 index for +£100.

Bifocals have two distinct optical powers in a single lens. They are designed to provide clear vision for both near and far distances, making them particularly useful for individuals with presbyopia, a common age-related vision condition.

The two main components of bifocal lenses are:

Distance Vision Area: The upper part of the lens is prescribed for distance vision. This part helps individuals see clearly when looking at objects in the distance, such as road signs or the board in a classroom.

Near Vision Area: The lower part of the lens is prescribed for near vision. This segment assists with tasks like reading, sewing, or using a computer, addressing the effects of presbyopia.

The transition between the two prescription areas is typically marked by a visible line across the lens.

Bifocal lenses are available in store for +£100.

Occupational lenses, also known as computer lenses or office lenses, are specialized lenses designed to provide clear vision at intermediate distances, and are typically used for tasks at arm's length. These lenses are beneficial for individuals who spend a significant amount of time working on computers or performing other tasks in an office or workplace environment.

This type of lens is recommended for add powers of +1.00 and above and the typically age 40+.

They can be used for other professions or hobbies that require glasses for close work at different ranges, such as musicians, painters, or seamstresses.

For occupational lenses, we use Zeiss Office Lens Plus, with Duravision Platinum Coating as standard.

Occupational lenses are available in store up to a 1.74 index for +£175.

Digital lenses, also known as anti fatigue lenses feature a large distance zone with a small near vision boost at the bottom of the lens. This lens is ideal for customers who often use digital and mobile devices, and start experiencing near vision discomfort for the first time. The small near boost helps the eyes to relax at near vision tasks and alleviates symptoms of digital eye strain.

Digital lenses are typically recommended for customers in their late 20's-40 with an add power up to +1.00

For digital lenses, we use ZEISS Smartlife Digital Lenses.

Digital lenses are available in store for +£175.

ZEISS DriveSafe Lenses are everyday lenses specifically designed to meet the visual needs of drivers. Design features and technologies enhance the wearer’s vision experience during the day or night while driving. Thanks to the DuraVision DriveSafe Coating, the lenses help to reduce perceived reflections and glare, especially at night.

DriveSafe Single Vision lenses are available in store for +£225. Drivesafe Varifocal Design lenses are also available in store for +£375