The ‘sph’ box represents ‘sphere’ and is the amount of myopia or hypermetropia present. Plus lenses correct hypermetropia and minus lenses correct myopia. The higher the number, the stronger the lenses need to be. As spectacles lenses increase in strength, they become heavier and thicker – the dispensing optician may then recommend high index lenses to make the spectacles more comfortable to wear and cosmetically more attractive.

The ‘cyl’ stands for cylinder and represents the amount of astigmatism present. The cylinder is usually recorded as a minus number, regardless of whether the sphere is plus or minus.

The ‘axis’ shows the angle at which the cylinder is set into the frame (0 -180 degrees)

Together the sphere, cylinder and axis make up the distance spectacle prescription.

If a ‘prism’ is included in the prescription, it is usually because there are symptoms that indicate the eyes are not working well together. These may include eyestrain or blurring after concentrated work. A prism helps to align the eyes by bending the light.

‘Inter’ shows the additional positive power required to focus for intermediate tasks e.g VDU or reading music.

‘Near’ shows the additional positive power required for close work.

The inter or near boxes are filled in for those people who are presbyopic and need a separate prescription for reading or intermediate tasks. This can be either a separate pair of reading spectacles if there is no significant distance prescription, or bifocals or varifocals.

Eye Conditions  The ‘Normal’ Eye The cornea and lens need to refract (bend) light rays that are reflected from an object by a precise amount in order to focus light directly on the retina. In this way, the retina receives a clear image. Myopia Also known as short-sightedness, this occurs when light entering the eye focuses in front of the retina rather than directly on it. This is due to a cornea that is steeper, or an eye that is longer, than a ‘normal eye’. Myopic people see well close up, but have trouble seeing further away. Myopia is corrected by lenses that focus light precisely on the retina, forming a clear image - this can mean spectacles, contact lenses or even orthokeratology. Depending on the degree of myopia, spectacles or contact lenses may only need to be worn for certain activities that require clear distance vision such as TV, cinema or driving. Myopia commonly occurs in school age children who report difficulty reading the board at school or seeing the television clearly. Often the degree of myopia increases rapidly whilst the body is growing, and then levels off in adulthood. During the teenage years, therefore, frequent changes in prescription may be needed to maintain clear vision.

Hypermetropia
Hypermetropia, or long-sightedness, occurs when light entering the eye focuses behind the retina rather than directly on it. This is due to a cornea that is flatter or an eye that is shorter than normal.
Young people with mild to moderate hypermetropia can focus their eyes to obtain clear vision at distance (as you would focus a camera), and then have to focus with greater effort to see clearly up close. The higher the degree of hypermetropia, the harder it is to focus. The ability to focus at different distances is called accommodation and is due to the lens being flexible enough to change its shape for different working distances.

Because children and young people are readily able to accommodate, mild to moderate hypermetropia is usually unproblematic. Often, children outgrow hypermetropia as their eyes grow. Some young people with a greater degree of hypermetropia may complain of symptoms such as eye strain, headaches and blurred vision after concentrated visual tasks. In these cases, corrective lenses that focus light on the retina - and therefore reduce the amount of accommodation required – are prescribed. The ability to accommodate is gradually lost after the mid to late forties and then hypermetropia is more of a problem. This can result in blurred vision for distance and near and headaches or eyestrain as the eyes can no longer focus. Corrective spectacles or contact lenses are then prescribed for distance and near tasks. Spectacles can take the form of separate pairs for distance and near, or bifocals or varifocals.

Astigmatism
For normal undistorted vision, the cornea needs to be smooth and equally curved in all directions – like a football. When astigmatism is present, the cornea is shaped more like a rugby ball, having two different curvatures – one steeper than the other. This means that rays of light entering the eye focus at two different points and therefore a clear image is not attained. Astigmatism can also occur due to unequal bending of light by the lens inside the eye.

Astigmatism can occur by itself, but often is found in conjunction with myopia or hypermetropia.

Many people have some degree of astigmatism, but those with a greater degree will require corrective lenses. Uncorrected astigmatism can lead to blurred vision, headaches or eyestrain after prolonged visual tasks. Astigmatism can be corrected by spectacles or contact lenses.

Presbyopia
Presbyopia is the term used to describe an eye condition in which the lens can no longer accommodate. Accommodation describes the ability of the lens to change its shape to focus at different distances. To focus close up, the lens needs to thicken – this requires the lens to be flexible. The lens loses this flexibility after the early to mid forties and therefore focusing on close objects becomes increasingly difficult. Although it can seem that this occurs suddenly, the loss of flexibility takes place over a number of years.

Presbyopia is part of the eye’s natural ageing process. It happens to everyone regardless of whether they already need spectacles, and it cannot be prevented. One of the first signs of presbyopia is needing to hold reading material further away to see it clearly – a common complaint is ‘my arms aren’t long enough!’ Other symptoms include blurred vision for reading, or eyestrain and headaches when doing close work. Early on, simply holding close material further away helps but eventually a near vision correction in the form of spectacles or contact lenses is required. Some myopic people can delay needing a near vision correction by removing their glasses for reading and close work.

The type of near vision correction appropriate is dependent on an individual’s lifestyle, occupation and hobbies. If you have good distance vision and only have difficulty seeing close up, a separate pair of near spectacles is often the easiest solution. For others, needing separate prescriptions for distance and near means two sets of spectacles and this can prove frustrating. In these cases, bifocal or varifocal spectacles may be more appropriate. There are now a wide range of contact lens options for presbyopia.