There are four common types of refractive error and they affect your sight in different ways. All of them can usually be corrected with glasses or contact lenses and do not necessarily mean your eyes are unhealthy.

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MYOPIA:

Myopia, or short-sightedness, happens when light is focused in front of, rather than on, the retina. This makes distant objects blurry, but close objects are clearer.

The most common way to treat this is with MINUS LENSES (-)

HYPERMETROPIA:

Hypermetropia, sometimes called hyperopia or long-sightedness, happens when light is brought to a focus behind the retina. This makes close objects blurry while objects in the distance appear clearer.

The most common way to treat this is with PLUS LENSES (+)

ASTIGMATISM:

Astigmatism happens when light is not brought to a single focus on the retina. The light is focused unevenly. This causes blurring of both far and near vision.

The most common way to treat this is with a combination of MINUS (-) & PLUS LENSES (+)

PRESBYOPIA:

Presbyopia is a normal age-related change, which happens in your early forties and gets progressively worse as the lens in your eye loses more of its flexibility.

The lens in your eye is flexible and able to adjust its focus when you look at objects at different distances. As you get older, the lens in your eye becomes stiffer and your ability to change focus reduces. This makes it harder to focus on close objects, such as when reading small print, particularly in poor light.

The most common way to treat this is with READING GLASSES, BIFOCALS, and PROGRESSIVE LENSES

 

UNDERSTANDING YOUR SPECTACLE PRESCRIPTION:

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Spherical error (SPH)

SPH stands for the spherical error and shows whether you have myopia (with a minus sign), or hypermetropia (with a plus sign).

The number shows the strength of the lens you need.

A smaller number means the condition is milder. PL is short for Plano and means there is no refractive error in that eye.

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Cylinder (CYL) and Axis

CYL stands for cylinder and shows the severity of any astigmatism. The axis shows the angle that the cylindrical power in your lenses must be set at to correct it.

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Near ADD and Intermediate ADD

This refers to the additional correction you may need to focus on at short distances and is more common over the age of 40.

The intermediate ADD refers to the additional strength of lenses you may need to bring a ‘mid-range’ distance in focus (usually the distance to a computer screen you are viewing) and the near ADD is usually for close tasks such as reading.

This number is added to the spherical error part of the prescription to give the actual near or intermediate prescription.

Not all prescriptions will have a section for the intermediate ADD, instead, it may be written in by hand if needed.