Photo: Eschenbach Optik GmbH
By Paul Graveson
BOptom BA GradCert(Optom) PGCOT
Optometrist, Low Vision Consultant
By definition, vision restoration is not possible for low vision patients. Still, some will believe that if you could only find the right combination of lenses, they would be able to see the way they used to.
It’s important to be clear from the start that low vision aids will not fix their vision. It will be just as blurry as before, but the aim is to make the print so good that they can read it even with their blurry vision. If the patient is still hoping for a return to normal vision, they are unlikely to accept the compromises inherent in any low vision aid.
Acceptance of low vision is a process, and some patients aren’t ready. For them, the best thing you can do is spend time helping them understand what’s going on with their eyes. Even if they reject every aid, it’s useful to schedule a follow-up appointment for six months later; they will eventually reach a point where they are ready to accept the help you can give. Be understanding and compassionate, but avoid giving them hope that new cures might be found, as it just makes it harder for them to reach the point of acceptance.
It’s important not to neglect refractive error though. Many low vision patients will reject their glasses because ‘they don’t work’. What they mean is they don’t fix their vision the way they used to, but often they are still of significant benefit. Partial restoration is better than no restoration. An improvement from 6/120 to 6/60 is just as significant as from 6/12 to 6/6, and having best spectacle correction can let the patient use more convenient lower-powered magnifiers.
Most patients will say ‘I just want to be able to read again.’ It’s important to be clear right from the beginning what they mean by that. Read books? Newspapers? Bills? Price tags? What can they already read even if it’s slow and uncomfortable? Most patients will need more than one magnifier, each one selected to be the best match for the specific task. For instance, a big reading lamp might be best for reading a book at home, but completely useless for taking to the supermarket.
The first type of magnifier to try is not a magnifier. I explained in an earlier article on illumination why I believe the first step should always be to give your patient the best possible light. Most people with low vision, but especially those with AMD, do better with a much higher level of light than we are used to. It can be as simple as sitting near a sunny window, but a well-chosen task lamp is often very helpful. Torches may be the best solution for looking into dim cupboards and sheds, and extra task lighting in the kitchen can preserve independence. Maximise the illumination, but be careful to not cause discomfort from glare.
The simplest way to make print larger is to choose books with larger print, and many patients will already have made that switch by the time they see you. Similarly, some will use photocopiers to enlarge crosswords or sheet music, or family members will copy out favourite recipes and phone numbers in large print with thick black pens. Combined with good illumination, these are very practical solutions for a surprisingly high proportion of low vision patients.
Hand-held magnifiers have the advantage of cultural familiarity for most patients. Most people used magnifying glasses as children, so lower powered hand-held magnifiers seem natural. Large ones from non-specialist shops are usually between +3.50 D and +6.00 D, and can be good, but most patients will prefer lighter magnifiers with better optics, such as those available from major manufacturers like Eschenbach and Schweizer. It’s helpful to wear reading glasses while using a hand-held magnifier, as the patient may still be able to read the headlines with glasses alone, needing the magnifier only for the articles of interest.
Most people think that a larger magnifier means a stronger magnifier. It’s important to explain that stronger lenses have to be made smaller, which means they need to be held closer to the eye to get a decent field of view. Once the lens is close, the page needs to also be brought closer to stay within focal range.
Lower powered hand-held magnifiers tend to have a reasonably high speed limit, as I explained in my article on magnification, but stronger ones can be more difficult to use and are more fatiguing over longer periods. Large, low-powered versions need good arm strength. Stronger powers need a steady hand to keep the text in focus. If the patient has a tremor, the image will jump around, negating much of the benefit of magnification. Because one hand has to hold the magnifier, it can be difficult to hold the book or newspaper with the other, especially if it has to be held close. The magnifier can also cast an annoying shadow on the page.
Reading at a table, perhaps with a reading stand, can help minimise these effects, as can using magnifiers with in-built illumination. Even so, hand-held magnifiers tend to be most suited to spot reading tasks that don’t require prolonged reading. Small folding magnifiers are ideal for putting in the pocket or purse and used for price tags, bus timetables and even text messages on mobile phones. Even though computer operating systems have integrated magnification options, it can be more convenient to keep a hand-held magnifier next to the computer for occasionally looking at small menu items, et cetera.
Stand magnifiers have the advantage of stability because they rest on the page. Lower powered models also need less arm strength, as the document can rest on a table or desk, but higher powered models still need strong arms, as both the magnifier and the text have to be lifted up and held close to the eye. Most stand magnifiers will have a light source, as otherwise the stand puts the text into shade. Some recent models with LED bulbs give excellent illumination while still having the portability advantage of batteries rather than needing mains power.
Although a stand magnifier gives a steady image, it can be awkward to slide around on pages that aren’t completely flat, such as books and magazines, so they tend to have slower speed limits. They are better suited to reading the narrow columns in a newspaper. In most cases they need to be used on a flat supportive surface, which doesn’t work well when patients want to keep reading in their comfortable chair or in bed. Leaning over to look through a stand magnifier can be hard on the back, so a reading stand can help keep posture more comfortable.
Most stand magnifiers are designed with the assumption that reading glasses are being worn. Different adds may be appropriate for use with different stand magnifiers, with little consistency. If the patient keeps lifting the magnifier off the page, it usually means they need a stronger add. If the image appears blurry, it may be that the patient needs a lower add. It’s easy to check by putting plus or minus 1.00 D lenses in front of their glasses while using the magnifier resting on the page. Eschenbach stand magnifiers are particularly well designed because they are all designed for a patient with a +2.50 D add.
Stand magnifiers are generally more bulky than the equivalent hand-held magnifier and aren’t so easy to fit in the purse or pocket; however, they can be excellent for general reading tasks around the home, including the newspaper. Determined patients can use them for books, although fatigue will usually mean they need to read in short bursts.
Magnifying lamps are particularly useful and I prescribe them a lot. They can be used as simple lamps for scanning larger print such as headlines and then the magnifier positioned for reading smaller print. Both hands are free to hold the book steady, and the lamp provides excellent low-glare illumination across the page. Along with the fact they can be set up next to a favourite chair, these factors mean they have a high speed limit and a high ease of use. They are often the best choice for prolonged leisure reading, as long as the magnification is sufficient.
Other than reading, the hands-free feature also makes magnifier lamps ideal for diabetic patients who need help to see their insulin syringes or their glucose testing apparatus, or for patients who want help with craftwork or practical fix-it tasks. A small magnifier lamp is very helpful in the kitchen, providing light over the work preparation surface and magnification for package labels and recipes.
Magnifier lamps are an excellent choice for many patients who want to read in comfort. They are not so suitable for patients who need moderate to higher levels of magnification, although some will still do well using the combination of a magnifier lamp with large print books. Most will also need a different magnifier for when they are away from the house.
The problem with magnification lamps is the process of supplying them, as they are bulky and not the sort of thing most optometrists want to keep in stock. In my article on illumination, I suggested a way of partnering with a local lighting shop, so you need only a demonstration unit in the practice. For DVA patients, you could arrange to have the lighting shop send the bill to your practice, then claim reimbursement from DVA (item OP97).
Most patients initially just want stronger glasses. It’s important to carefully explain to patients that the glasses themselves don’t magnify. It’s bringing things closer that makes the image bigger, and the glasses simply keep the text in focus at the closer position.
Many patients resist the abnormally close working distance, and some have physical difficulty holding things so close, but for those who don’t mind, strong adds can be good solutions for more prolonged reading. They have high speed limits because they provide excellent field of view, and having both hands to hold the book improves ease of use and stamina. Unfortunately, the image flow when using much stronger powers can induce motion sickness in some patients.
Beyond about +4.00 D you need to start adding base in prism to keep convergence relaxed. Above +10.00 D it gets tricky to maintain binocularity even with prism, so you need to switch to just one eye. Ready-made reading glasses are available with powers as high as +48.00 D, at which point the length of the nose may be the limiting factor. At very close distances it’s hard to avoid putting the page into shadow, so patients need to carefully position a reading lamp above their head, or sit near a sunny window at just the right angle.
Strong adds should usually be dispensed as a supplementary task-specific pair of glasses. For general wear, patients still need a more usual add for day to day activities, such as preparing meals or shopping.
If your patient really needs a spectacle-mounted solution but can’t manage the closer working distance, such as when reading music while playing an instrument, you need a near telescopic system. There are few options. The Eschenbach Max Detail is a ready-made low power binocular system which is designed for a 40 cm working distance. Other than that there are several excellent quality miniature telescopes designed for use as bioptics which can be fitted in primary position for near use, but they are expensive and need to be prescribed and fitted very precisely, so are best handled by a low vision clinic.
LOW VISION: Part 1. Understanding
LOW VISION: Part 2. Illumination
LOW VISION: Part 3. Magnification
LOW VISION: Part 4. Contrast
LOW VISION: Part 6. More about aids
This series of articles has been prepared with the support of the Tasmanian Optometric Foundation. Contact Paul Graveson at email@example.com.