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Bifocal and multifocal contact lenses - what's the difference?

Posted on 02 November 2016

As we age the lens inside our eye starts to sclerose or harden resulting in a condition called presbyopia. This lens, called the crystalline lens, has to change shape to become more fat or convex to see up close. After the age of 40 to 45 the lens is unable to become so convex leading to a deterioration of our reading vision. This then means that most of us require bifocal or multifocal corrections in the form of spectacles or contact lenses.

So what are the different types of contact lenses to correct presbyopia and what is the difference between multifocal and bifocal contact lenses? Bifocal and multifocal contact lenses are available in either a hard or soft material. In both materials there are several different design philosophies enabling the wearer to see in the distance and at close while wearing the contact lens.

Bifocal contact lenses

Bifocal contact lenses

  • Translating bifocal contact lenses. These contact lenses have two areas of vision in the one lens and the lens is specifically designed to not rotate. The top of the lens has the distance correction and the bottom half of the lens has the reading correction. As the wearer goes to read they drop their eye to look downwards, which results in the bottom eyelid pushing the contact lens up so that the reading portion of the lens is in front of the pupil. This 'alternating vision" means that you are able to see up close. This type of contact lens often has less flare than other bifocal contact lenses however they are not particularly suitable for use with computers unless they are prescribed with an element of mono vision. This is where one contact lens is prescribed full strength for close work and the other contact lens is prescribed weaker for more an intermediate working distance. Translating bifocal contact lenses are generally found in a hard gas permeable contact lens material.
  • Concentric design. This type of contact lens design is the most common form of bifocal contact lens and is found in both hard and soft materials. The contact lens is designed in a bull's-eye pattern with the centre of the bull's-eye being a reading prescription with a concentric area of distance vision circling this. Some designs have alternating concentric circles of distance and reading prescription. Other designs have the distance vision in the centre with the reading vision encircling it. Some brands of concentric design bifocal contact lenses have the near portion in the centre of the contact lens on your dominant eye and the distance portion in the centre of the lens on your non-dominant eye. Concentric design bifocal contact lenses rely on simultaneous vision whereby the eye will see the distance and the reading simultaneously. This results in some glare and flare around objects and can take a week or so for adaptation. There is about a 70% success rate with this form of bifocal contact lens.

Multifocal contact lenses

  • Aspheric contact lenses. This type of multifocal contact lens relies on aspheric optics with the distance correction in the centre of the lens. The lens then has a change in curvature towards the edges resulting in the lens slowly increasing in power towards the periphery of the lens. Aspheric multifocal contact lenses rely on simultaneous vision to enable the wearer to see in the distance and at close. This will initially result in some flare. 

Multifocal and bifocal contact lenses for astigmatism

A limited range of contact lenses are available to correct long sightedness, shortsightedness, astigmatism and presbyopia simultaneously. The most successful contact lenses in this form are the gas permeable range of lenses such as Menifocal which is an aspheric design. There are also a more limited range of soft contact lenses to correct astigmatism and presbyopia such as the Proclear Multifocal Toric

If you're considering multifocal or bifocal contact lenses it is essential to be fitted correctly and accurately by your eye care practitioner. It is not unusual to have to trial several different brands before you find one that gives you adequate vision.