Why is it so?

A clear lens casts a black shadow. How?



We thought we’d post this picture we took during concept development of our upcoming blue light window display. So why is it that the spectacles and the large lens leaning at top left cast a black shadow but the two lenses at the bottom do not?

The savvy readers will already have figured out that it is due to the wavelength of the light from the globe, what the picture shows is some of our lenses as compared to a more basic offering on the market.

What does this tell us? Well, we used a UV lamp to illuminate the scene and our lenses are the ones that are casting the black shadow. This is because all of our lenses contain UV inhibitors, unlike the ones at the bottom left of the picture. So you can be sure that you are getting all the protection you need, every time.

How much extra does this cost? From us it doesn’t cost one cent more. We put top quality hard coated, UV blocking lenses in every pair of spectacles we make, so you can be assured you are getting the best quality, performance and protection.

At Hannaford Eyewear we know optics. Contact us to discuss your needs today.

Individual Fit, Premium Care, Hannaford Eyewear.

Anti Glare Coats?

Anti Reflection lenses or Anti Glare?

This is a remarkably big topic but we do get asked this a lot so we shall try our best to explain without descending into anything too horrendously complex!

Is there any such thing as an anti glare coat? Not in the sense that some advertising campaigns might have you believe. In fact, many of the coatings that are touted as being anti glare are actually anti reflection (AR) coatings, something quite different indeed!

Reflections and Coatings


The centre of this sheet has had a circle of anti reflection coating applied.

The surface of every lens reflects some light, with this amount varying according to several factors such as materials and even pre existing coatings like hard coats. Typically uncoated or hard coated lens surfaces reflect around 7% of light, which of course means that only 93% of the available light is making it to your eye. For thinner, higher index lenses this number drops to as low as 85%. The result of this is that we now have lenses that not only show reflections, but they are also not allowing all of the light through, impeding better vision.

What can we do about this? The solution to reducing reflections and increasing light transmission is rather ingenious and makes use of  destructive interference. By placing a coating on the surface that makes the reflected light out of phase with the incident light we can get the ‘peaks’ of the incident waves to interact with the troughs of the reflected waves and vice versa causing the reflection to be cancelled. To do this the coat needs to be 1/4 of the wavelength thick, or odd multiples of this number to maintain the out of phase relationship.  Because visible light has a range of wavelengths an average value roughly around yellow is often used, which while not perfect, does allow for optimal results. Modern AR coats will also have multiple layers to reduce the issues caused by the averaging even more, plus there are extra coatings that are added for resilience, hence another name for AR coats is ‘multi-coats’.


Click image for link to original at www.tutorcircle.com

If that sounds excessively complex then think of waves at the beach, sometimes two waves can arrive at the same time, resulting in a bigger wave as their energy combines. Other times a wave will arrive at the same time as a gap in the swell so it is fallen into the ‘gap’ and is cancelled out, it’s this cancelling out effect that we want to achieve.

Now that all of that is out of the way we can think about what it means. When we apply an AR coat to a lens it is actually increasing the transmission of light to effectively reduce the effect of the lens on light transmission. What we want to achieve is a situation where the prescription can do it’s work with as little awareness of a lens being there as possible for the wearer. That’s pretty much the opposite of anti glare!


The glare from these headlights is caused in part by the lens, which is why AR coats can be beneficial for night driving by actually increasing light transmission.

What do you see on an AR coated lens? As a wearer you will get more comfortable vision as the lens will let through as much light as possible. For situations where you need to concentrate for extended periods this is a tremendous advantage. A similar effect is observed driving at night and particularly in the rain, halos from streetlights are reduced and general comfort is increased. For people looking at you there will always be some slight reflection as we cannot cancel every wavelength simultaneously, because of this AR coated lenses will tend to have a slight green or blue reflection which we refer to as the bloom.

A downside to the extra clarity is the fact that AR coated lenses may show dirt and marks more easily. They don’t necessarily get any dirtier or scratch easier than other lenses, in fact they are designed to be tougher than ever, but they do show marks simply as a result of the more refined surface. The good news is that modern coatings are constantly improving and are now easier to clean than uncoated lenses so you can have the best of both worlds.

There are some circumstances in which a lens itself will create reflections but it is important to realise that this is not ‘glare’. These can be troublesome reflections, ghost images or even halos around lights that are a result of light interactions inside the lens. Night driving and driving in the rain is a perfect environment for these kinds of halos (see the image above), thankfully AR coats are very useful in reducing these effects to.

One cosmetic benefit of AR coats is the decreased awareness of the lens when looking at the wearer, meaning that we all get to see your eyes. This is especially useful for film and television where coatings have long been used to eliminate reflections, I often look for the AR coats on actors spectacles in films and try to identify the company that made them. And yes, I realise how nerdy that sounds.

Reducing Glare

If we consider glare as originating from a light source or surfaces like sand or water then we can begin to understand the techniques needed to reduce its impact. Glare by definition is a strong or dazzling light source so when we consider this in the context of AR coats we should readily see that increasing light transmission will do very little to reduce discomfort caused by glare or bright light, if it is performing as intended then it will have no effect on the glare at all.

To reduce glare we need to reduce the amount of light reaching the eye. This can be in the form of a tint, polarisation or very specific lenses like the new blue control types of lens. In any event what we see for glare reduction is an attenuation or blocking effect. Lenses with this in place will not look as clear as an AR coated lens, (obviously in the case of sunglasses!) but even the new generation of blue control lenses will have a light tint to them.

Screen Shot 2016-12-19 at 12.10.11 pmYellow tints have been cited anecdotally as reducing glare at night but their actual effect is somewhat more complex that this. By design yellow filters will reduce some effects of glare by blocking a percentage of the blue light from headlights for example. However, the trade off is that a percentage of the overall light level has been blocked in the process, so we have a reduction in glare but also a reduction in transmitted light. Consider the effect of that at night when driving where it is generally desirable that we get more rather than less light to the eye, if only for the sake of safety. Because of this tints for night time driving are rarely recommended.

What should I use?

So know you know the difference between reducing reflections and reducing glare the big question is ‘what do I want to actually achieve?’. Consider your symptoms and what may be causing them. Is it fatigue or glare? Do you want to increase or decrease the amount of light coming through the lens?

The easiest way to work out your requirements is to talk to a qualified professional like those at Hannaford Eyewear. Why not contact us today?

Christmas opening hours


Christmas Clinic Hours

Merry Christmas!

We would like to extend our best wishes for the season to everyone in the Highlands.

As always we will only be closed for the public holidays to ensure that we are available to serve you but if you do need urgent attention please  use the contact page and we will get in touch as soon as possible.

Saturday 24/12/16        9:00am-12:00pm

Sunday 25/12/16           (Christmas) Closed

Monday 26/12/16         (Boxing Day) Closed

Tuesday 27/12 /16        (Public holiday) Closed

Wednesday 28/12/16   9:00am-5:00pm

Thursday 29/12/16       9:00am-5:30pm

Friday 30/12/16            9:00am-5:00pm

Saturday 31/12/16        9:00am-12:00pm

Sunday 1/1/17               New Years Day Closed

Monday 2/1/17             Public Holiday Closed

Tuesday 3/1/17             9:00am-5:00pm

After this our normal hours resume.


High powered spectacles

How high is a high prescription?

How long is a piece of string? The highest powered spectacles that we have ever made at our practice were a set of -35.00 diopter lenses for a worker at a Mongolian orphanage. This is certainly well above the normal power range 0f around 0.00 to 4.00 diopters but shows that limits are made to be pushed! How did they look? They were very thick indeed but the patient was happy to report that the trees outside their window now had leaves and they could function in their role at the orphanage, so they got the job done.

One of our more recent efforts was a -22.00D lens that we made for a patient. Again our patient was happy with the resultant vision and this time we managed to get some photos of the finished job too.

What did we do?


Power compensation

First and foremost the power of the prescription as written is examined. In this case we were able to determine that the test was performed with the frame at one distance from the eye but the new spectacle frame was sitting much closer. This results in a need for compensated powers to ensure that the prescription in the new spectacles is the same as that experienced in the eye test. By doing this we can ensure that the patient is getting exactly what the doctor ordered.

In some cases this can result in a remarkable change in powers so it is vital that these things are considered, not just for extremely high powers but even for prescriptions that may not seem overly strong at first glance.

We also made sure that the lenses made use of an appropriate material and lens design that balanced thickness reduction with the visual requirements of the patient. By making use of our in house design facilities it was possible to gain visual acuities and visual fields that enabled this patient to retain their drivers license, something they had previously been told was impossible.



Asymmetric prescriptions

Various eye conditions can result in a patient having asymmetric powers (i.e. one eye needing a much stronger prescription that the other). Lenses made for these patients will give different image sizes and rates of image movement, the effects for the patient can range from mild discomfort to extreme visual distress and nausea. Patients who have had one cataract removed and are waiting on the other to be operated on will often experience this condition known as anisometropia (unequal refractive power).

In many cases it is possible to overcome the difference in powers by manipulating the relative curvatures of the lens surfaces as well as several other factors. Lenses made to correct this condition are known as iseikonic lenses and can look a little interesting with various curves and thicknesses, but if the end result is clear, comfortable vision these are small considerations.


Many people are unaware of what prism actually is, but those who do need it are very aware as it enables them to get one clear image of the world rather than double vision. The causes of prismatic prescriptions are varied but can include issues with the muscles of the eye or even traumatic injuries to facial bones.

We use prism to help a patient ‘fuse’ the two images received by the eyes and the amounts required to do this will vary according to each case. Most patients who need it will have somewhere between 0.50D and 2.00D, the highest we have seen was 26.00D which was one of the most challenging cases we have experienced.

In some cases the amount of prism required will vary between distance and near vision. These require special solutions as we need to bring many disparate elements together in one pair of spectacles. One of the best solutions for these is actually one of the oldest lens designs, the ‘Franklin Split Bifocal’. At Hannaford Eyewear we are proud to manufacture our own Franklin Split Bifocals on site which means that you can be sure that we are working with you to reach your optimal vision.

So even if you have been told that your prescription is too high or too hard to make up, contact us or come and see our team, you might be surprised at what we can achieve for you.