Visit 3: Your guide to Competency 4.2.1

Eschenbach's Mobilux-Digital4.2.1 Advises on the use of, and dispenses simple low vision aids including simple hand and stand magnifiers, typoscopes and handheld telescopes.

Compulsory Evidence – Patient Record/s

The indicators for this competency statement include:

  • Identifies which patients would benefit from low vision aids and advice
  • Understands the principles of magnification, field of view and working distance in relation to different aids
  • Provides advice on the advantages and disadvantages of different types of simple low vision aids
  • Understands the mechanisms of prescribing magnification including acuity reserve
  • Gives correct instruction to a patient in the use of various aids, to include:
    • Which specs to use with aid
    • Lighting required
    • Appropriate working distance
  • Provides basic advice on non-optical aids, use of contrast and lighting to enhance visual performance and daily living skills

Identifies which patients would benefit from low vision aids and advice

Have there been any indications during your examination, which could be more appropriately covered within a low vision assessment perhaps? How detailed was your task analysis?

Any patient who is struggling and who would benefit from an increased near addition or advice on lighting qualifies here, however make sure that you are giving them the most appropriate advice according to the presenting condition. Symptoms of a cataract are quite different from the syptoms related to a hemionopic field defect or a positive central scotoma. So, take a run through the most common causes of impairment and make a list of the presenting signs and symptoms of each as your management will alter widely.

Also within this indicator be aware of the World Health Organisation’s International Classification of Impairment, Disability and Health, covered under he ICF Documentation. Links here.  A brief knowledgi will suffice – at least be aware f it existence and why it is there in the first place.

Be aware also of current statistics – what are the most common causes of vision impairment in the UK and according to age. For example, AMD scores highest in the elderly age group, with the wet AMD the most devastating form, typically as a result of a more rapid loss of vision.  What is the most common cause of vision impairment in the working population? And where does POAG fit in? Although less likely to be questioned, but you should still be aware of, are the congetintal causes of vision impairment in the younger age groups but who account for longer number of years accessing services for the visually impaired (congentia cataract, optic atrophy, nystagmus and related conditions.

Understands the principles of magnification, field of view and working

Magnification? We are simply making things bigger. It may sound simple, and really, it is. But it comes with its disadvantages too. From enlarging the patient’s scotoma to reducing working distance and cutting out light.  What I would recommend here is to look at the various methods of making things bigger. Physically, optically, telescopically and electronically.  All are relevant.   With respect to optical magnification, it may be more simple to think of it in this way –  you are simply asking a patient to get closer to the object – the lenses are merely bending the light onto the retina.  So, get a magnifier, and take a look through it. Do you know how to achieve the best effective magnification? Do you know how far away to hold the lens from the object? Can you fry an ant and if so, how?  Dust away some old lecture notes and if yours were poor, get a book.  Magnification and the principles of such should come easy to a trainee who has studied optical lenses and light, (and who was once a child who tried to fry an ant).

Examples –

relative size magnification – making it bigger. E.g. large print books

relative distance magnification – get in closer – using a plus lens to focus

Provides advice on the advantages and disadvantages of different types of simple low vision aids

Under this competency are covered ‘simple’ low vision aids – Hmm, not my categorisation but this is what we work with. Spectacles magnifiers, hand and stand magnifiers and some telescopic magnifiers.  You will need to understand the basic optical principles for each of these categories, patient selection and training and advantages and disadvantages of each under given situations or conditions. Would you prescribe a hand held telescope for shop prices? No, a hand magnifier would be more appropriate, although the hand held telescope may be useful to locate the correct aisle.

To have a good idea of the advantages or disadvantages, pick it up and look through it. Use one for yourself. I like to categorise according to type here. For the sake of the argument I am grouping all aids here, ‘simple’ or otherwise.

  1. Hand magnifiers (variable distance from the object)
  2. Stand Magnifiers (fixed distance from the object)
  3. Spectacle magnifiers (think of a plus lens in the spectacle plane)
  4. Telescopes (not the Brian Cox type) – refractive not reflective or radio..  Distance and Near. Based upon Keplerian and Galilean designs.
  5. Electronic vision aids (video magnifiers, CCTV – a rapidly increasing market (again, distance, intermediate and near).

Remember (please) low vision devices may be called low vision aids and never low visual (there, had to get that one off my chest – as frustrating as the your/you’re argument.

Along with advantages, disadvantages, be able to give examples of use (no moving buses or targets please, we need to be realistic here) – be able to demonstrate how you would instruct a patient to use it and with which spectacles (review vergence here).

Understands the mechanisms of prescribing magnification including acuity reserve

How do you calculate the power of the device? Have a routine. No complex calculations please – they simply don’t work in reality. Yes, by all means be aware of the relationship between your numbers, between 6/60 to 6/6, (10x) between N24 to N6, (4x) but when a patient has a posterior subcapsular cataract, a field defect and a touch of AMD, they don’t go according the rules (and why?).

This indicator also moves on from your understanding and knowledge of what magnification is to how do we assess for magnification and how do we go about prescribing the right magnification for each of the patient’s tasks taking into consideration the relevant acuity and contrast reserves. Yes, contrast is not listed here, I know, I’ve added it in, but the principles are the same, after all, if you are unable to perceive something with reduced contrast, no matter how big you make it, it still wont be visible to you, will it.

So acuity reserve. What does it mean? Well, have some acuity in reserve – don’t allow the patient to work right on their limit of threshold.  For a quick look or a spot check, that’s quit possibly okay – in other words if your patient wants to check  he dial on the cooker (say, N20) and all they can see with their glasses or magnifier is the same size, ie N20, then they are working on the limit of their vision with that device, and there is no acuaity in reserve. If however they want to look at a size of print for any length of time (a column of print for example), then they will be more comfortable if they had a reserve of vision. For example, if they are reading N20 for any length of time, the need a reserve of about 2:1 – i.e. prescribe enough magnification for them to achieve a minimum of N10.  A 2:1 reserve s about right for most tasks that require sustained viewing. But don’t go too high, too much reserve will mean excess prescribed magnification and thus a reduced working distance, field of view, light etc. etc.

Provides basic advice on non-optical aids, use of contrast and lighting to enhance visual performance and daily living skills

Along with the optical aids for low vision, this competency also assesses your knowledge and understanding of non-optical aids for low vision, such as typoscopes, daily living equipment, and additional strategies to enhance performance such as auditory and tactile stimuli.

You will need to have some basic knowledge on advising patients on lighting, glare and contrast; which means taking into consideration their level of vision, the tasks and the underlying condition or factors which are causing the patient’s reduction in visual performance.

For daily living aids, visit the RNIB website here and take a look at the types of devices that are used by visually impaired people.  Better still, make a small donation and have the catalogue in your consulting room (extra Brownie points from the Assessor and me).

Best Form Evidence

Within the practice setting it is expected that you have seen at least one patient with a visual impairment requiring a low vision aid (refer to the Patient Episode Sheets) and therefore, the primary source of evidence will be Patient Records.  Where possible, have at least three records to show to the Assessor.  Don’t groan.

If you have a patient to whom you are considering dispensing an aid, ensure that the following have been addressed sufficiently:

  • A full detailed task analysis, to include the size and working distance of the task or tasks
  • Whether the patient needs something hands free or spectacle mounted
  • Does the patient have the ability to hold their hand steady?
  • Does the task require a flat surface?
  • Is the cosmesis acceptable?
  • Will there be any training required?
  • Will the close working distance be accepted?
  • Is the aid required to be portable?
  • Is additional or integral lighting desired?
  • Is cost a significant factor?

Most Assessors will also ask you questions about the simple hand magnifiers that your practice may have in stock.  So if your practice has some magnifiers on display, make sure that you are familiar with them.

With each type or group of aid you should be able to discuss the following list with the Assessor:

  • Identify type or aid (hand, stand magnifiers etc)
  • Assess magnification and power
  • Materials and casing
  • Lens form
  • Illumination system (mostly LED these days)
  • Advantages or disadvantages
  • Patient selection
  • Examples of use
  • Be able to demonstrate how it is used, to include working distance, FOV, acuity reserve
  • Be aware of the range of magnification available for each category. Can you get a 5x distance Galilean telescope. No? Do you know why? Can you get a 20D hand magnifier? Yes, what s the magnification? At what distance would you advice the patient to hold it if they are using theor reading glasses at the same time?

Your knowledge should be able to address the following issues:

  • Why, for example, is it not possible practical to produce a Galilean design telescope for distance viewing above 3 x magnification?
  • Why is it less successful when prescribing a hand magnifier beyond 20 dioptres say for fluent reading?
  • Why is it necessary to incorporate illumination within a stand magnifier of 20x magnification?

You should also appreciate the basic optical principles of each type of aid, otherwise you will be unable to appreciate why they work or do not work in any given situation.

  • For example why did the uncorrected myope flip his stand magnifier upside down so that he could hold it closer to the page?
  • What could we do to rectify this situation?



Unless you are practicing in Wales, where a significant proportion of low vision aids (LVA’s) are dispensed by locally trained and accredited optometrists within a high street setting, the majority of LVA’s are dispensed to patients through the Hospital Eye Service (HES) or from a service provider commissioned by the Primary Care Trust .  So unless you acquire some hospital experience or make arrangements to visit the service provider, you may find it difficult to come across any suitable patients to evidence this competency adequately.

If you are to be able to advise patients on the use of their aid, it follows that you should also make the opportunity to view and play with some of the hardware.  If the Assessor presents you with a simple hand held magnifier from his or her briefcase then try to look as though you have at least seen one before!

Visit the main suppliers websites:  Take a look as to what is on the market.  There are some great products out there – and most a fraction of the cost of a new pair of spectacles.

As you can see, despite the need to understand the theory – my advice is more focused (sorry for the pun) on the practical. After all, it what the patient goes home with at the end of the day rather than what would work for them theoretically.  However, the the theory can cut out several hours of consultation time and patient dismay, so to recap:

1 Have a routine.

  1. Have structure to your advice and consultation
  2. Understand there are many facets to low vision – be aware of local services and support
  3. Have a good method for follow up.
  4. And have a routine – In other words, similar to all of your other patients.
Click here to go to ABDO Bookshop

Click here to go to ABDO Bookshop


Associated Optical



Eye Essentials Low Vision Assessment

Good luck! Leave me your questions below. .


  1. Thanks Jane for the article. My practice doesn’t have any lvas but we do have some old hand magnifiers. Should I show these to the assessor?

  2. If you show any LVA’s to the assessor then you must be able to talk about them. Hand magnifiers are LVAs and they will come under the ‘simple’ category. (Not that I ever liked that categorisation of them but there you go.

    In addition make sure you have also used them – there is little point talking about something you have not actually used. You should be able to demonstrate that you have shown them to patients inside or outside of the consulting room.

    Ba able tot alk about advantages, disadvantages, give a demonstration on how to get the best use out of them, which spectacles to use etc. If you cover all that then its probably time to move onto the next competency. Give me a shout if there is anything that you are not sure about. Good Luck – Jane

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