Category Archive for: ‘Clinical’

An Amsler Grid used to detect macular distortion and losses

RTE Nationwide

The RTE One programme Nationwide this evening was visiting the Waterford Institute of Technology, highlighting the research into, and importance of Macular Degeneration, particularly its early detection and treatment. It was an interesting programme, and obviously the team in Waterford are leading specialists, for sure in Ireland, but perhaps worldwide.

The programme can be viewed on the RTE.ie website – there seems to be a limit of the last ten episodes.

One thing I do think is worth a mention- virtually everyone interviewed decided to have their eyes checked because they had noticed that they were having problems – they felt their glasses were not sufficient, or noticed distortion. Recently the Royal National Institute for the Blind in the UK was campaigning to highlight the problem with symptom led eye examinations- they were imploring Optometrists to stress the importance of regular eye tests – ones where there were no symptoms!

Many problems can be detected before symptoms are noticed by the individual, though this may not necessarily be the case in Wet AMD. Anyone concerned about Wet AMD should put an Amsler grid on their fridge or noticeboard and check their vision weekly. An Amsler grid can be downloaded here.

Guy Wearing Glasses

Myopia Control with Contact Lenses!

Guy wearing glassesMyopic Deterioration can be slowed with multifocal contact lenses.

A recent study has found that young myopic (shortsighted) contact lens wearers who were fitted with a specific type of multifocal contact lenses progressed at a slower rate than age matched peers. Although it was a small study, the results were still found to be statistically significant, meaning that there is very little likelihood that the results were different by chance alone. They found that the shortsight developed at half the rate of the control group.

This is a very interesting finding – 50% is quite a lot! at last there may be a way to slow down those children who seem to get worse, more shortsighted, at every visit.

Researchers believe that by making the peripheral vision slightly blurred using bifocal contact lenses (initially designer to help older people read with their lenses), the eye somehow knows to stop growing. This peripheral blurring will not affect the wearer’s vision significantly- peripheral vision is really only useful for movement detection.

Another study from a couple of years ago, in Australia used a lens design which was later licenced to CibaVision. Though Ciba have not yet released a contact lens specifically aimed at myopia control, there is mounting evidence that it can be effective at slowing those patients who seem to be constantly slipping.

A still from a video simulating driving with Glaucoma

Driving Vision and Glaucoma

Yesterday was the annual AGM of the Association of Optometrists, and also a study day- all Optometrists have to undertake a certain amount of Continuous Education and Training. At the moment this is voluntary, but will probably become compulsory in due course.

One of the lectures at the study day was about driving and vision, a subject that has become very topical of late. Particularly interesting I thought were a couple of videos which tracked the eye movements of Glaucoma patients when tested in a Hazard Perception Test. It had always been assumed that people who have a visual field deficiency will scan around, and move their head more to compensate for their problem, but as is mentioned here, the issue is that they may not even realise that they have a problem, and even if they are aware of an issue, they do not see the problem. If you don’t see something, you don’t think “I didn’t see that” – you just don’t see it.

The Hazard Perception test used eye tracking to follow the “Point of Regard” of normals and Glaucoma patients, also measured were reaction times – when would they hit the brakes?  The study found that people with Glaucoma do not scan around more than normals – indeed one of the videos below show that they remain fixed almost exclusively on the car ahead, failing to notice the hazard of a car pulling out ahead, until the car they are following reacts to the threat.

Video Number 2 shows the Glaucoma patient’s Point of Regard in Blue, the normals are shown in red, it is quite noticeable how little the Glaucoma patient looks at other aspects of the driving scene – they completley fail to look at the pedestrian with the buggy, something all the normals are obviously worried about.

Video number 3 has superimposed onto it a representation of the patients field of vision-  the more dense the areas of field loss, the darker the overlay. (It moves around because its position is relative to the fixation point, the blue dot. Remember that a Glaucoma patient will not see this blackness, they will just have blank areas, their brain will fill in the details as best it can.

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The Glaucoma losses featured in Video 2 and 3 are mild to moderate – according to UK standards (where this study was done), this patient would still be legal to drive.

This shows that even if you do not feel that you have a problem, you should have your eyes regularly checked!

 

The full articles are available to read at these two links;

Obstacle Avoidance, Visual Detection Performance, and Eye-Scanning Behavior of Glaucoma Patients in a Driving Simulator: A Preliminary Study

Exploring Eye Movements in Patients with Glaucoma When Viewing a Driving Scene

A child wearing a patch

Squints, turns and lazy eyes.

I had a young boy in for an eye exam today, booked in because he had failed his school vision screening. When his mother booked the appointment, I got the impression that she thought that his eyes were fine, except for the fact that he has a squint, “but he has always had a squint.”

Any optometrist’s immediate thought would be that a squint would be an obvious fail on a school screening, as squints are not normal. Some squints might not be easily detected at a screening- sometimes squints can be very difficult to detect without experience, but what is detected is the lazy eye which usually results from the squint- if a child learns that they can see better with one eye than both together (as two misaligned eyes cause double vision, and confusion- an inability to tell which object is in the straight ahead position), eventually the brain might habitually ignore one eye, and it will become “lazy”.

A squint is not the only possible cause of a lazy eye – if there is a significant difference between the sharpness of the eyes, again the brain might ignore the blurred eye. This is less common than a squint as the cause of a weakness, but often there is no way the parents could possibly suspect that there might be an issue.

Lazy eyes need to be detected as young as possible (ideally they should be prevented)- even if the bad eye cannot be improved to the same standard as its fellow, any improvement which can be gained (usually quite quickly – as a young child) may prevent months or years of difficulty as an adult, who may be unable to work or drive if the good eye was damaged by accident or disease. Lazy eye treatment may also remove restrictions which might be imposed in certain career choices, such as those requiring Class 2 driving licences, and many of the forces.

I had reason to contact Meath County clinic about this young chap, and was informed that there was an approximate waiting list of at least 12, probably more like 18 months before he could be seen –  this is unacceptable, as a problem like this will be much more difficult to fix by an age of seven. He will be 6 to 6 1/2 when he is eventually seen. There is no point in screening the vision of school children if there is no sensible referral pathway available for those who fail.

This post is just to mention to parents that even if you THINK you see your child’s eye turning (perhaps it may be more obvious when they are tired) or you suspect one eye is poorer than the other, you should get this checked out as soon as possible – it is not normal, it will not go away on it’s own, and it will almost always result in a poor eye if nothing is done to intervene. Children rarely complain about visual difficulty – they have no reference to know that having a poor eye is not normal.

Parents – it is up you you!

Blue Laser

The danger of handheld lasers

Recent reports suggest that there is an increase in the number of young people attending hospital with ocular damage caused by handheld laser pointer devices. One recent report details the treatments required on fourteen patients who had an average age of 17. Approximately 70% of the patients required surgery, half of them had haemorrhaging inside the eye, and 4 of them had full thickness macular holes (a hole in the retina at the back of the eye, in the area where best vision is usually achieved).

All patients showed an improvement in visual acuity compared to that at presentation, but the mean acuity initially was approximately 6/90 – that means that what a normal eye should see at 90 metres, they could see at 6 metres -quite poor. Average vision achieved after recovery was 6/12- the eye required things to be twice as big or half as far away as normal.

There have been reports for years about pilots and police officers being dazzled by laser pointer pens, but these new lasers are much more powerful, and are a shorter wavelength of light- laser pointers used in presentations are usually red, but these new ones are blue, with a wavelength of 450nm. This colour is better absorbed by back of the eye, resulting in more damage than a red coloured laser. There are even posted methods on YouTube on how to increase the power output of a handheld pocket laser, though some available online are hugely powerful to begin with. They may look a bit like a light sabre from StarWars, but there could be serious consequences of playing a prank with one of these devices.

Experts predict that, if left unregulated, handheld lasers purchased online could cause an epidemic of ocular injuries.

Parents be warned- don’t let your children have one of these!

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