C37110: Eccentric viewing training

Closing Date: 17/07/2014

Assessment of visual function Standards of practice Low vision

More than 500,000 people are thought to be living with late stage age-related macular degeneration (AMD) (Figure 1) in the UK.1 With 40,000 new cases of wet and 44,000 of dry AMD expected each year, a significant number of your patients will face the news that they are developing signs of macular disease or will already be living with central vision loss.

Figure 1: OCT scan of wet AMD associated with loss of central vision

Figure 1: OCT scan of wet AMD associated with loss of central vision

Functional impact of AMD

The loss of fine detail and reduced colour vision makes everyday activities such as reading, recognising faces, selecting colour co-ordinated clothing, setting temperature dials on appliances, telling the time, shaving and nail cutting very difficult.

In patients with bilateral central vision loss, residual vision training may be a viable tool to help them use what remains of their vision.

Reading, in particular, becomes difficult with macular disease as the learned saccadic reflex is disrupted by a foveal scotoma but the brain still tries to utilise saccades when reading. This results in irregular (scribble-like) eye movements and patients will often describe their experience of reading as ‘words seem to come and go’. This is due to the scotoma covering the word that is being read.

Eccentric viewing, what it is and how it works

Eccentric viewing (EV), also known as eccentric fixation, involves identifying an area of the retina that retains reasonable functionality, and is as close to the fovea as possible in order to maximise detail, and learning to use it effectively. Not everyone with central vision loss will need to eccentrically fixate. It depends on the type and amount of damage or scotoma(s). (See section on the five types of scotoma and whether EV and/or steady eye strategies may be appropriate).

Some people with central vision loss use EV for distance tasks – many find they can see a friend’s face or the television better when they are not looking directly at it. However, not many people adapt this to near tasks without training. The area or direction of gaze that the patient uses for occasional distance tasks is not necessarily the best position to use for near tasks like reading.

Steady eye strategy (SES) is a technique that specifically helps with reading. SES requires the patient to break the saccadic reflex by keeping their gaze still, and scrolling the text right to left, through their functional area of vision. This technique enables the individual to keep their place in the text, and improves their accuracy and reading speed, although not to pre-macular disease levels.

A systematic review of literature evaluating EV and SES training, undertaken by Cardiff University for the Macular Society in August 2012,2 found there was very good evidence that EV training incorporating SES, or eye movement training, improves reading and the ability of participants with central vision loss to perform a wide range of daily living activities. This review also found very good evidence that EV training is more effective than provision of magnifiers alone for improving near visual acuity in individuals with an absolute central scotoma.3 We strongly urge low vision practitioners, optometrists and dispensing opticians to provide or enable access to EV training prior to the dispensation of magnifiers.

Scotoma

There are five types of described scotoma4 (Figures 2 to 6) which are useful to consider when considering eccentric viewing intervention. Individuals may have one or a combination of the following.

  • Ring scotoma (Figure 2). This is when the very centre of the macula is still functioning, but is surrounded by damage. In these cases EV is not appropriate, but SES may assist with reading. Smaller print size may help as the individual will be able to see more of a word within the functioning area. Ring scotomas often close up as the disease progresses, so EV will remain an option to return to if needed in the long term.

Figure 2: Ring Scotoma

Figure 2: Ring Scotoma

 

  • Oedema (Figure 3) occurs when fluid builds up between the retinal layers and often results in wavy lines and distortion (metamorphopsia). If the distortion disrupts reading, EV along with SES may help.

Figure 3: Metamorphosia

Figure 3: Metamorphosia

  • Multiple scotomas (Figure 4). This is often described by patients as ‘patchy vision’, as sight loss has occurred in patches across the macula. These people will tend not to benefit from high levels of magnification – simply making something bigger means less fits into the small area of foveal clarity. However, EV and SES may be of benefit.

Figure 4: Multiple scotoma

Figure 4: Multiple scotoma

  • Relative scotoma is often described by patients as ‘misty’ vision. In these cases the macula is working but at a reduced level. Lighting and magnification may be all that is required to help the individual. However, if the scotoma is significant, it may be beneficial to teach EV and SES.

Figure 5: Relative

Figure 5: Relative

  • Absolute scotoma results in an absence of central vision. EV and SES, using an area of retina which is closest to the macula, might benefit the individual.

Figure 6: Absolute

Figure 6: Absolute

How to identify the preferred retinal locus – tools and techniques

Loss of foveal and macular function results in a patient using a part of the retina outside the area of functional loss in order to see. This eccentric viewing relies upon the patient adopting a new retinal point for fixation and this preferred retinal locus, or PRL, needs to be identified if eccentric viewing training is to be effective. To help identify a patient’s best remaining functioning vision and to support the identification and use of a PRL, various tools have been developed and adapted over the years.

In every case, it is important to start with a conversation where the individual describes their own vision and what they are having difficulty with. This conversation should help you to identify the type of scotoma and whether EV and/or SES are needed.

It is important to ascertain which is the better eye (this isn’t just dependent on acuity but also the type and location of damage), and work with this eye on the following exercises to identify and refine the PRL. Remember, you are looking for the areas of functioning vision, not the damaged areas.

Face to face

Using one eye at a time, ask the patient to look straight at your nose and describe any parts of your face that are clearer or more distinct. From this you should be able to identify a better eye and the clearest area is the vision you will use as a PRL.

Clock-face technique

Ask your patient to imagine a clock around your face. As they do this, ask them to identify which area is clearer by reference to the clock number. This not only helps to identify the vision you will use as a PRL but may help an individual to remember where their PRL is.

Amsler grid

Use an Amsler grid with diagonal lines and a dot in the centre. Working with the better eye and wearing a full aperture reading prescription (bifocals and varifocals will give a false reading), ask the individual to concentrate on the centre of the grid and describe the location of the clearest areas.

Electronic methods

The concept of microperimetry, whereby stimuli may be presented to a patient in close enough (one degree or so) proximity to one another, allows practitioners to assess the residual sensitivity of the macular area in and around areas of damage. Machines have been developed (see page 16, for example) which may help identify a PRL and suggest a possibly more suited point for fixation, a PRL relocation target or PRT.

Eccentric viewing – using the PRL

Once the clearest vision has been identified, a person should be taught how to eccentrically fixate and use their new PRL. If the individual describes the clearest area as being top right, in order to see things which are central they will need to look down to the bottom left. Using the clock-face technique, the clearest area might be reported as number 1, so an individual should look towards number 7 to see the centre.

Using the PRL for reading

When reading, instead of looking straight at the first letter of the text, the patient would need to apply the same principle. For example the patient would need to look down and to the left of the first letter. In this case, SES will also be necessary, so the patient should be instructed to read by keeping their eyes in position (relative to the text) and their head still, and moving the text from right to left, like a typewriter.

The importance of practice

It takes practice to fully utilise EV and SES, and patients will need encouragement to practice several times a day for a few minutes at a time after they leave the clinic. They should practise using everyday things they want to see, for example photographs, letters or watching the TV. For reading it may be useful to start with larger print, such as the headlines, and with practice move on to smaller print, using a magnifier if needed.

Your role

In general, to successfully meet the needs of people with macular disease, optometrists and dispensing opticians require skills in effective inter-professional working, as well as having a good understanding of the services available, whether provided by social or health care, or the voluntary sector.

Timely support and advice means that your patients can adapt better and learn to cope with any reduced functional vision, while maintaining their confidence and independence. In the longer term, this can help to reduce depression, social isolation and the incidence or severity of falls, all caused by their visual impairment.

Optometrists and dispensing opticians, as well as low vision practitioners, are in the ideal position to give:

  • Practical demonstrations and advice on how to use task lighting effectively
  • Advice on counteracting glare and using colour and contrast
  • Information on conditions and adjustable risk factors, such as smoking cessation advice
  • Signposting information to local and national support services that offer both practical and emotional support.

Alongside the need for further clinical investigation or intervention when active wet AMD is suspected, it is vital that patients are referred to low vision and rehabilitation services as soon as their condition impacts on their daily activities. This includes signposting to, or the provision of, training on EV and SES for people with bilateral central vision loss, to help them to use their residual vision more effectively.

The Macular Society recognises that during a standard appointment you will not always have time to do more than introduce the concept of EV and direct your patient towards other information. However, the face to face and clock-face techniques could be used in just such a time-pressured situation, and you should signpost your patient to other agencies who provide EV training. Rehabilitation officers for the visually impaired in your local social services may be able to assist.

The Macular Society operates a Skills for Seeing programme which provides free one-to-one coaching in EV and SES through our growing network of volunteer trainers, many of whom have central vision loss themselves. We also hold information about other providers of SES and EV coaching, including providers from the voluntary sector and health and social care. A Skills for Seeing leaflet is available, and your patients can contact the Macular Society Helpline on 0300 3030 111 to learn more. You may also want to register a patient on their behalf.

If you are a low vision practitioner offering EV and SE skills coaching and are happy for us to signpost people to you, please let us know at http://bit.ly/Mglu8z

Keep informed

The Macular Society bi-annual Revision News details the latest EV-related developments and our free professional membership provides easy access to a full range of patient literature and the latest developments in the field, including research updates. If you would like to join as a professional member please register at http://bit.ly/1hByULd

References

1 Owens CG. Jarrar Z, Wormald R, et al. The estimated prevalence and incidence of late stage age related macular degeneration in the UK. Br J Ophthalmol, 2012. doi:10.1136/bjophthalmol-2011-301109.

2 Allannah Gaffney, Tom Margrain, Alison Binns, Cardiff University, Cardiff, Wales Catey Bunce, Moorfields Eye Hospital, London, England A systematic review of literature evaluating eccentric viewing and steady eye training. Prepared for the Macular Society August 2012. Executive Summary: http://bit.ly/1my8nkf.

3 Vukicevic & Fitzmaurice. Rehabilitation strategies used to ameliorate the impact of centre field loss. Visual Impairment Research, 2005; Volume 7 2-3 Pages 79-84.

4 Adapted from Optima Low Vision Services, Training for the Future 2014.

? Amanda Reeves is a low vision practitioner and low vision services manager for the Macular Society where Cleon Hutton is revision programme manager for the eccentric viewing programme

Model answers

(The correct answer is in bold text)

1. Which of the following repoted scotomas might be indicative of fluid build up around the fovea?

A. Absolute

B. Relative

C. Metamorphopsia

D. Ring

2. Which of the following best describes steady eye strategy?

A. Maintaining fixation on a point to the side of that wishing to be seen

B. Maintaining a fixed point of fixation while moving the target relative to this

C. Keeping the target as still as possiblewhile scanning

D. Marking fixed points within text upon which to fixate

3. According to the recent research cited in the article, which of the following might be stated as correct?

A. Eccentric viewing training incorporating steady eye strategy is more effective than provision of magnifiers alone for those with central vision loss

B. Eccentric viewing training incorporating steady eye strategy means magnifier provision is unnecessary

C. Eccentric viewing training has no evidence base as to its effectiveness

D. Eccentric viewing is of benefit to reading only

4. For which of the following is eccentric viewing training unlikely to be of benefit?

A. Relative scotoma if significant in depth

B. Ring scotoma

C. Absolute scotoma

D. Multiple scotoma with macular involvement

5. Which of the following statements about a preferred retinal locus is FALSE?

A. It might be identified using a clock-face technique

B. It is always in the eye with better acuity

C. Electronic methods are available for identification

D. Amsler grids reveal areas of better central vision and aid PRL location assessment

6. What is the PRL relocation target (PRT)?

A. The area the patient prefers to use as a PRL

B. The area to which, over time, the PRL moves as disease progresses

C. A site away from the adopted PRL which has been identified through various means as more appropriate for PRL location

D. A PRL which, having been established over time, is deeply ingrained despite disease progression