As a modern independant opticians,our patients have access to the very latest expertise and technology for the examination and maintenance of healthy eyes. The lenses we recommend are the very best available, ensuring that your vision is always our top priority. As a forward-thinking eye-care practice we strive to offer our patients the latest in designer frame choice and optical technology. At S.I.Opticals we understand it's important for people to feel comfortable in their glasses so we source a wide range of quality designer and non-designer frames. Our professionally trained staff can advise on frame suitability and styling as well as guaranteeing expert fitting.

Understanding a prescription

A prescription is legally issued at the end of every sight test. This contains information about the precise measurements carried out by the Optometrist allowing us to provide the most appropriate prescription lenses to give our customers the best vision possible.

Sphere (Sph)

This represents the amount of long or short sight that is present. A + indicates long-sighted (hyperopic), This means that the patient may have difficulty to see things close to them. A – indicates short sightedness (myopic), this means that the patient may have difficulty to see things far away.

The number can be as small as 0.25 to a larger number such as 10.00. The larger the number the stronger the lens required hence the thicker the spectacle lens.

Cylinder (Cyl)

This represents the amount of astigmatism present. Astigmatism is a term to describe the shape of the eye when it is not completely circular (like a football), but more like a rugby ball. This can cause the vision to be distorted for both distance and near objects.

This number can be as small as 0.25 indicating the eye is nearly round or as large as 10.00 showing that the eye is quite oval. If the is no cylinder present a ‘DS’ will be present near the sphere indicating just sphere.


This represents the direction of astigmatism from 0-180 degrees. It is not related to how well you see but allows the lab to know what angle to position the lens in the frame. It is only present if there is a cyl.


Prism (if any) is needed to align the eyes if the muscles in the eyes are not working correctly. These are used to prevent double vision or headaches.


The base is for the lab and tells them where to put the prism in your glasses


This box is mainly used for patients over the age of 45 (presbyopia). This is a reading addition added to the prescription allowing patients to focus at close distances. It is always positive + and indicates a different prescription is needed for distance and reading. We may provide two separate pairs of glasses, Bifocal or Varifocal lenses to help them with this.