Wednesday, 18 November 2015

A Guide to Modern Varifocals

A guide to varifocals

What are varifocals and who needs them?

Whereas a normal single vision lens has one prescription in the lens which generally corrects for either poor distance vision or poor near vision, a varifocal lens (also called a progressive powered lens, or PPL) has more than one focus of clear vision in the same lens. In this regard, the varifocal is similar to a bifocal lens, but the varifocal has the cosmetic advantage of looking no different to a standard single vision lens.

Like the bifocal lens, the varifocal lens is useful to almost everyone over a certain age (typically between 40 and 45) because at around this age, everyone looses accommodation, which is the eye's ability to focus clearly close up. Someone who has lost the ability to accommodate is a called presbyopic.

As well as looking better than a bifocal lens, which typically has an annoying line visible in the lens where the two prescriptions meet, the varifocal is more useful too. Instead of the line between the distance vision part of the lens and the near vision part of the lens that a bifocal has, where the eye jumps straight from one prescription to the other, a varifocal has an additional area of clear vision between the distance and near prescription called the intermediary part.

This allows the wearer to see well at intermediate distances, such as are useful for working on computers, as well as seeing clearly in the distance and close up.

What about the downside?          

Although the varifocal has three prescriptions in one lens and can do the job of three different pairs of glasses, the vision in each part of the lens will not be quite as good as it would be in a single vision lens dedicated to the distance, or intermediate, or near prescription. However, wearing one set of varifocals is much more convenient than carrying up to three different sets of spectacles around! One other potential disadvantage is that some people have difficulty getting used to varifocals because they find it uncomfortable to move their eyes quickly between the different powers of the lens leading to a swimming effect.

Traditionally, around one in ten people found it uncomfortable to use varifocals, which was often due to excessive amounts of blurred vision and distortion in the periphery of the lens because of the poor quality of the design used but today with the most advanced modern lenses adaptation is quick due to a minimum amount of swim. 

Pupillary Distance
Fitting Heights

Another cause of intolerance to varifocals can be the poor fitting of the lenses. To fit a standard varifocal lens some basic measurements are required. In rushed practices where they don't take time to measure this can lead to inaccuracies. If these are only slightly off by half a millimeter it can complicate adapting to varifocals.
Even when precautions are taken to stop intolerances to varifocals some people still can't get away with them. Because a small amount of people still do struggle to adapt to varifocals, Mellis Eyecare offers a three month period of grace, during which varifocals can be exchanged for a pair of bifocals or two pairs of single vision glasses at no extra cost meaning you aren't left with a pair of spectacles you can't use.

Are all varifocals the same?

No, there are many, many different types of varifocals on the market, all of which offer the wearer different levels of improved vision and comfort. Here at Mellis Eyecare, we offer a wide range of lenses to suit every budget, and chosen by our highly qualified Eye Care specialist, specifically for their high quality and up-to-date designs.

And, just like when buying a suit, there are varifocals that can be bought off the shelf, varifocals that are made to measure, and bespoke varifocals that are altered to the precise requirements of the individual. The main difference being that the lens form moves from a one size fits all style, for the more basic lenses, to a more and more precisely tailored fit for the more expensive lenses.

Our off the shelf varifocals come in three different styles, starting with the Hoya Amplitude, a good quality all round basic lens. The Hoya Summit Pro is a good mid-range lens, with improved lens usage. The Hoya Lifestyle lens offers the best off the shelf solution to the requirements of the presbyopia and comes in two different standard versions: the Lifestyle Harmony, which is designed to maximize all round vision, with an equal bias between distance and near vision, and the Lifestyle Clarity, which is designed to favour distance vision and is perfect for people who drive a lot, or play a sport that requires the highest level of hand eye co-ordination.

Back Vertex Distance

The Lifestyle Exact is a made to measure lens that is tailored to the individual spectacle frame and takes into account the back vertex distance, pantoscopic tilt and dihedral angle of the fitted lens.

The back vertex distance is how far the lens sits from the eye ball. 

The pantoscopic tilt is the angle that the lens sits in front of the eye.

The dihedral angle is the curve of the frame on your face. 

Measuring these extra values allows Hoya to maximise the varifocal design for the frame optimising the vision through the distance, intermediate and near.

Pantoscopic Angle
Dihedral Angle

For those that refuse to compromise, the Hoya Mystyle is the last word in individually tailored lenses, and offers the best all round solution to the needs of the presbyope.

This top of the range bespoke lens, is designed precisely for the spectacle choice and vision requirements of the individual, having eleven different customizable design parameters.

Our Hoya varifocal lenses also come with a wide range of water, oil and dirt repellent protective and anti-reflective coatings. The Lifestyle and Mystyle lenses come with the High Vision Long Life anti reflective hard coat - the hardest coat available on the market.

MELLIS eyecare 
Thornaby 01642 751048                                                North Ormesby 01642 225671


Monday, 9 November 2015

Children Sight Tests

Testing Young Children

Because young children can't always answer the optician's questions in the test room, the first eye examination for a baby or toddler has several unique components that are designed to overcome such difficulties. Also, because young children are growing rapidly, there are lots of common conditions that first appear at this age, and which it is important to treat quickly as they become harder to correct the older the child is. 

One such condition is called strabismus, which most people call a squint or a turn. In this condition the eyes do not align properly, and if left untreated it can lead the patient to develop amblyopia, or a 'lazy eye', a condition that makes normal binocular vision (stereopsis) impossible. If the strabismus is treated early enough, however, it can often be corrected, which is why it is so important to test young children. Up until the age of five, a period known as the 'critical period' normal binocular vision can often be preserved with the correct treatment and sometimes it can even be returned once it has been lost. It is also important not to assume that a child without strabismus does not need testing because one in four children without any sign of a squint will nevertheless have some underlying condition that will progressively worsen without treatment. 

To overcome the difficulties in testing children who are too young to answer the optician's questions, there are several tests that the optician carries out that do not rely on verbal answers. Here at Mellis Eyecare, we use the most up-to-date computer based tests to ensure that children engage fully with the eye examination, and the best healthcare outcomes are achieved.  

So if you have any concerns about your child's eyesight, no matter how old they are, why don't you book them in for a sight test today?

MELLIS eyecare 
Thornaby 01642 751048                                                North Ormesby 01642 225671