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?

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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.

 

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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.

Prism

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.

Novelty Contact Lenses & Halloween

At some point in the past decade Halloween has popularised itself across Australia. While I was growing up Halloween was always an American ‘thing’. It was something we saw in American movies and a part of American culture. Halloween was an eve celebration of the feast of All Hallow’s Day: a three day observance of Allhallowtide dedicated to remembering the dead including saints (hallows), martyrs and all the faithful departed.

With the rise of popularity of Halloween in Australia, interest in novelty or decorated contact lenses as part of a Halloween costume has also increased. While these may add that ‘wow’ factor to your costume, non-prescription accessory lenses can be dangerous and lead to significant, long-term eye damage. This is particularly true when they have not been fitted by an optometrist.

Best practice is to ensure not only optimal vision but also comfort and correct fitting in order to maintain ocular health. The cornea (the tissue layer in front of the iris) where the contact lens sits on is a delicate tissue. A compromised contact lens could potentially introduce unwelcomed bacteria to the corneal surface and cause mild infections to sight threatening conditions causing scarring and blindness. Furthermore, an optometrist is able to correctly advise the best method to remove, insert and clean contact lenses and the appropriate products to use to minimise the potential for scratched corneas and allergic reactions to solutions.

A recent study has found that cosmetic contact lenses available online circumvent regulation from safety agencies such as the Therapeutic Goods Administration (TGA) and can contain harmful chemicals such as chlorine, which can seep from the colourants in the lens to cause toxicity problems for the eyes. (i)

So even though you may only wear these contact lenses as a one off, they still require the same high level of care to be worn safely. The following is recommended for all contact lens wearers:

  • Have contact lenses properly fitted at an optometrist who will also instruct you on correct insertion, removal and cleaning of lenses.
  • Always wash hands before touching contacts and never store or clean contacts with tap water.
  • Don’t sleep in contact lenses unless advised it is safe to do so by your optometrist.
  • If your eyes become red, sensitive to light, painful, gunky or your vision becomes blurred remove lenses and see an optometrist ASAP. (ii)

(i) http://Scanning Electron Microscopy Findings with Energy-Dispersive X-ray Investigations of Cosmetically Tinted Contact Lenses, Eye & Contact Lens, Sept. 2015

(ii) Recommendations from Optometry Australia

Image is from www.allaboutvision.com

Screen time and blue light

Screen Time & Blue Light – ‘Getting the Blues’

Blue light

Technology has delivered an astounding array of developments over recent decades. Computers have moved from room sized arrays to, quite literally, the palm of our hands and the interface between the device and us, the screen, is becoming the source of greater scrutiny.

In order to deliver better results for clarity and brightness, technology developers have created screens and lighting that produces a ‘whiter’ or ‘cooler’ light. Consequently we are experiencing a somewhat greater level of blue light from our devices than previously and at greater intensities.

While there is evidence that blue light wavelengths are valuable for increasing our attention span and alertness, it seems counterintuitive to want this effect at night when we are preparing for bed. Yet this is the time when many people tuck themselves in to catch up on emails, surf the web or wander through social media. Put in context, we have now started stimulating our brains at the very point when we would traditionally be winding down for sleep.

Screen time

In Australia there has been considerable interest in how blue light works with the human eye[i]. Recent debate has centred on the role of blue light in macular degeneration and damage to the retina with limited results available thus far. Early indications are that, like UV exposure, the effect of blue light on the eye may be cumulative so damage may appear as a result of a lifetime of exposure rather than from brief periods. When considered in the context of extended screen usage in the evenings as well as all day at work then it is possible to see the source of concern among researchers and industry.

Melatonin & sleep

Research from Harvard Medical School has suggested another link between excessive blue light exposure at night and adverse health effects[ii]. By exposing subjects to light it is possible to change the production of melatonin in the body, which in turn can influence the circadian rhythms (or sleep patterns). The Harvard studies indicate that blue light specifically has a greater effect than other wavelengths or even white light. By comparing blue and green light they found that blue light changed sleep patterns by twice as much (3 hours vs 1.5 hours shift in sleep pattern).

While the dose of blue light from a screen pales when compared to natural sources like the sun there is the timing of the exposure to consider, we have shifted our exposure to include all hours of the day and night rather than just daylight hours. In light of this it appears that prudence is the order of the day so the following tips may prove useful:

  • Use features such as “Night Shift” or “f.lux” which change the type of light (also known as temperature) to a warmer light at night.
  • Consider using warm colour light globes.
  • Many lens manufacturers are offering lens coatings that are specifically designed for screen users such as the Solitaire Protect Balance. These coatings can give relief for people using screens for extended periods.

[i]Blue Light Guidelines Coming’, Optometry Australia News, Helen Carter, June 20, 2016

[ii] ‘Blue Light Has A Dark Side’, Harvard Health Letter, September 2, 2015

Facial Measurements & Online Spectacles

Some years ago there was a rush by website developers to offer online spectacles and we often get asked why we don’t have an online spectacle shop as well. The answer is quite simple, one of the most fundamental parts of getting accurate spectacles made is the facial measurements and we can’t get those via an online shop. Our primary concern is the accuracy and suitability of your spectacles so that you maintain good ophthalmic health and functional vision.

In order to make a functional pair of spectacles there are several key components:

  • Prescription
  • Lens design
  • Frame
  • Facial measurements
  • Fitting compensations

No matter how sophisticated the system may be for a website they will never be able to deal with the last two points, most websites claim that they can deal with the frame fitting as well, but this is really only something that can be done ‘face to face’. In fact, even the lens design is nearly impossible to get perfect without having a detailed discussion with the patient, so let’s be frank, all an online seller of spectacles will be able to do is make something that duplicates your prescription without any regard to usage or appropriateness (we’ve checked, and they even have a disclaimer saying that their spectacles are not guaranteed to be usable!).

In order to correctly select and fit a spectacle lens to a frame we need to know the dimensions of the patients face and relative eye positions, and no, that is not just the ‘PD’. There are also heights, vertex distance, tilt, working distance and so on. What they determine, indeed what is most important, is the centre of rotation of the eye. This is vital to position the lens correctly so that the patient does not experience unwanted aberrations. It is also impossible to obtain these various measurements without either a great deal of skill or specialised equipment. None of these measurements are possible via an app and most certainly can’t be obtained in the absence of the frame!

Once this information has been determined the practitioner will make compensations to the measurements to ensure that the lenses present precisely the same powers to the eye as were measured by your Optometrist in the eye test. Patients are often amazed by the large impact that a tilt or shift in centration can have on their perception of the world and it is this role that your practitioner plays almost unseen to the public, the interpretation of the prescription.

This is why many practitioners decline to offer facial measurements to their patients when asked, it is not meant as an insult, rather it is an indicator of their level of concern for your ongoing optical health.

With ever greater advances in lens design these measurements become increasingly vital, in some cases an error of even 1mm will render your lenses effectively useless. Going online means that you may be getting far less than you paid for.

For further information on public policy on this and other issues relating to Optometry please visit the following sites from Optometry Australia

http://www.optometry.org.au/your-eyes/glasses/prescriptions.aspx

80276-3073239