Daleen Slabbert consults to the optometric industry. Her services include: new practice set-up, implementing practice systems, implementing financial check points, staff training, implementing marketing strategies, human resources management, motivating staff, etc. She has amassed an incredible library of information and has vast experience in the running of high performance optometric practices. Daleen offers an on-site service, where she will be at the fore front of implementation of her systems. She has also developed an outstanding online course for optometric staff.


You are about to undergo a visual examination, or you are back to collect your new eyewear. Your optometrist discussed various options with you, of which some may have been unclear. This article will be very helpful in allowing you to understand optical jargon.

Long sightedness – Hypermetropia: This is a condition of the eye in which light is focused behind, instead of on the retina. This results in close objects being blurry, while far objects may appear normal. As the condition worsens, especially in older people, objects at all distances may be blurry. It is caused by either the axial length of the eye being too short or the curvature of the cornea and lens being too flat.

Short sightedness – Myopia: The image of a distant object is focused in front of the retina, because the eye may be too long, or the refractive mechanism is too strong. Short-sighted people will have blurred distance vision, but normally have good near vision, often holding text very close.

Presbyopia: This means that you need glasses for near work. Once we reach our forties, our ability to focus on closer objects declines, requiring correction for near vision. This is very natural, occurring as the lens in your eye loses elasticity over time, making it harder to bend and therefore, to focus.

Astigmatism: There’s no need to worry if you have been diagnosed with astigmatism. It is a common refractive error that causes blurred vision. It occurs when the cornea (the clear front surface of the eye) is irregularly shaped. Sometimes this is caused by irregular curvature of the lens inside the eye. This is corrected for in both distance and near vision and can be built into all types of lenses and contact lenses. This is called ‘cyl’ in your prescription.

Squint: A squint occurs when your eyes don’t line up in the same direction. The movements of the eyes are controlled by muscles that work in pairs. If one muscle is weak, a squint can occur. The most common type of squint is where one eye turns slightly inwards, towards your nose. Sometimes the eye may turn out or, very occasionally, up or down, while the other points straight ahead. A squint can result in double vision and sometimes the brain can suppress one image to overcome this. If a young child has a squint, it is important that he is examined by an Eye Care Professional to help prevent the eye, that does not look straight, from becoming lazy.

Prism: A prism is used in a spectacle lens to make it easier for the eyes to work together as a team. It can correct double vision or just poor alignment, which can cause discomfort. The prism displaces an image in order to do this.

Pupillary distance (PD): This is the distance measured in millimeters between the centres of the pupils of the eyes. This measurement is different from person to person and it is used to ensure that the optical centres of the spectacle lenses line up perfectly with the pupils (visual axis). Monocular PD is the distance from the centre of the bridge of the nose to the centre of the pupil. This measurement is used when fitting multifocal lenses.

Varifocals: Varifocals or Multifocals are lenses designed to correct vision at all distances, from far distance to around 30 cm. These lenses are commonly prescribed for the over-forty age group, because the near focusing mechanism has declined. They are available in different designs, depending on your visual demands. It may take a little time to adjust to, like wearing in a new pair of shoes. If you’ve tried varifocals before with no success, it’s worth trying them again. Modern technology has seen a considerable shift in manufacturing techniques, which made it possible for almost anybody to wear them.
Bifocal: The top section of a bifocal lens is used to focus in the distance while the bottom part is used for reading and other close work. Due to the unsightly line where the lens power changes from distance to near, these lenses are often replaced by varifocal lenses and contact lenses.

Photochromic lenses: These special lenses react to varying levels of ultraviolet light (UV). When they come into contact with sunlight, molecules in the lenses react and become a darker colour, acting as sunglasses. When light levels drop, the molecules go back to their original state and become transparent. Photochromic lenses only react when exposed to UV light, which means that a brightly lit home or office will not cause them to darken. Because most car windows block out UV rays, these lenses are not as effective as sunglasses when driving.

Refractive Index: The refractive index of a lens refers to the lens material’s ability to bend light. The higher the number, the thinner and lighter a lens can be made. Thinner does not always mean better, so it’s best to trust the optometrist to recommend the best option for the prescription and frame selected.

Anti-reflective coating (AR): An AR coating eliminates reflections from the front and back surfaces of spectacle lenses. The AR coating improves vision, reduces eye strain, and makes spectacles look more attractive. With reflections gone, more light passes through the lenses to optimise visual performance. These lenses look nearly invisible and are particularly good for night driving.

Blue Light Blockers: These are specially coated lenses which block out harmful short wavelengths emitted by all digital devices such as computers, tablets and cell phones.

Tints on sunglasses: Various coloured tints are available on sunglass lenses. The choice of colour of the sunglass lenses should be taken into account to best suit the main activity they are used for. For example, brown tints block high amounts of blue light to heighten contrast and visual acuity, useful to improve contrast on grass and against blue skies. Green tints heighten contrast while preserving colour balance. Grey tints reduce overall brightness, while preserving hundred percent normal colour perception.

UV 400: This a label on sunglasses that guarantees it will block out all harmful short wave lengths up to 400 nano meters.

Polaroid lenses: They eliminate glare reflected off horizontal surfaces such as water, snowy hillside, or shiny car bumper. They are excellent for most outdoor activities but beware, they will blur your cell phone screen.

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