Booklet  Examining People with Learning Disabilities

The Prescription – When And What To Prescribe

If your patient already has glasses, then the decision whether to change the Rx will not differ for a patient with learning disabilities. Deciding whether and what to prescribe for a patient who has not previously had glasses is more difficult. There are no guidelines about what constitutes a significant refractive error but use your experience of what levels of Rx benefit your usual patients as a starting point. A person with learning disabilities has the same right to good vision as the rest of us. When visual acuity is reduced by pathology, it becomes more difficult to determine what level of Rx will produce a noticeable change in acuity, so it is worth trying to measure corrected acuity. Corrected acuity can also be useful to demonstrate to carers why you are prescribing – some carers have a negative attitude to spectacle wear by their clients.

Trial frames severely restrict the visual field and your patient may not be able to carry out an acuity task wearing the Rx in a trial frame. It may be useful to have a selection of glazed frames to hand in common prescriptions, especially for high prescriptions. Demonstrating an improvement in acuity with a partial correction will help you to decide whether to prescribe and help the patient and carer appreciate the benefit.

All spectacle lenses introduce distortions and magnification/minification. Lenses with an appreciable cylindrical component can be particularly difficult to adapt to. In addition, if your patient has had an uncorrected refractive error for some time, a spectacle correction will give them a completely unfamiliar perception of the world, patients sometimes reject spectacle wear for this reason. Use the glazed frames to judge your patient’s tolerance to a prescription and to decide on how much to prescribe. Consider a reduced correction if you suspect that the patient will find difficulty adapting and advise an adaptation programme to build up tolerance. This will mean the patient wearing their spectacles for a short time for a particular activity and gradually increasing the time. Advise the carers that it may take weeks or even months for the patient to tolerate the spectacles for the length of time you expect or for all of the activities you advise. A range of factsheets on spectacles and introducing spectacles to people with learning disabilities can be downloaded from www.lookupinfo.org 

Accommodation

Adults with learning disabilities become presbyopic just like the rest of the population; because many of them don’t read, this simple fact of life rarely occurs to carers, who don’t think that ‘reading glasses’ might also help a client to eat their meals or do crafts and puzzles. In addition to presbyopia, studies have shown that people with Down’s syndrome and cerebral palsy are highly likely to have accommodation problems, even as children. It is therefore essential that near functions form as major a part of the examination as distance ones. Kay Pictures and Lea symbols have near cards among the range of tests, and reduced Snellen charts are available for patients that can name or match letters.

With some patients you will be able to measure amplitude of accommodation, using a push-down rather than push-up technique. Your patient may not understand the concept of ‘blur’. Instead, show them a small row of letters or pictures, or a finely detailed single picture such as we find on a ‘budgie stick’. Hold the target deliberately close to the patient and ask what is on the page or stick. Bring the target further away until your patient can answer your question (do this slowly as your patient may have a long reaction time).

Dynamic retinoscopy is an easy technique that allows objective measurement of accuracy of accommodation. Some text books will argue that the addition of minus lenses allows measurement of amplitude; this is suspect, since many able young adults (optometry students in particular, who are usually the subjects in such studies) are unable to overcome minus lenses by accommodation.

With the distance refractive error corrected (another occasion when glazed frames are helpful), place a detailed target at your patient’s habitual working distance and place the retinoscope alongside. Note the reflex in one meridian of one eye. A ‘with’ movement will indicate a lag, or under-accommodation; move the retinoscope back to find neutral. A lag greater than 0.75D means significant under-accommodation and the patient may benefit from a near correction.

You can now determine the near addition by placing plus lenses before the patient’s eyes to find the least plus that places the neutral point within 0.75D of the target. 

Dispensing

 
Consider the full range of options for spectacles as you would for a conventional patient. People with learning disabilities have the same right to a fashionable well-fitting frame as our other patients (see Figure 10).

Bifocals or varifocals may be as well tolerated as by any other patient except for people with eye movement disorders (see next article) who may find it difficult to access the add. Two separate pairs however, may cause problems for staff in trying to remember which pair is for which activity.

You will need to pay particular attention to the choice and fit of frame, as your patient may not be able to tell you if the spectacles hurt. Be imaginative. A high myope will often choose to look over the top of his/her lenses for near work; you can improve his/her posture by fitting a very shallow frame with a gap below the lens large enough to allow near viewing under rather than over the specs. For near specs, choose a half-eye or shallow frame that can be worn lower on your patient’s nose he/she can leave them in place rather than try to remember to take them off for TV.



Figure 10. A patient choosing frames

A patient with cerebral palsy and uncontrolled head movement may have difficulty keeping spectacles in place. A patient who uses a head rest on a wheelchair may find that the head rest knocks the spectacles out of place. Think about creating loop ends on the frame and using a head band.

Reporting Your Findings

Unless in a family setting, an adult with learning disabilities is likely to be cared for by a number of carers. A family situation may change and siblings may take over the care of your patient as parents age. It is therefore essential that all information you provide is given in written form, so that it can be shared by everyone involved with the patient. Your patient may also attend a day centre or go to work or training, and staff in these places will also need the information about spectacles and vision. Make sure that the patient (or responsible carer) consents to your sharing information with outside agencies.

If you are prescribing, simple but precise advice on spectacle wear is essential. If the spectacles are for near work, then you don’t want staff unthinkingly putting the glasses on your patient for walking around (clear labels on spectacles may be needed). Explain why you are prescribing and what the benefits to the patient will be. Outline the adaptation programme if you are recommending one. Remember the issue of consent; ultimately it has to be the patient’s decision whether to wear spectacles or not; simply allow the patient to make an informed choice.

Describe your findings on acuity and other functions in layman’s terms. ‘Detail vision four times poorer than normal’ can be readily understood: 6/24 cannot. You may want to consider providing a report directly for the patient, in terms he/she can understand. Many adults with learning disability have their own book about themselves with pages for health care issues that you can add to. Some use Augmented and Alternative Communication (AAC) systems, in the form of pictures or symbols. Explore this with the carers; providing advice in the patient’s own medium will expand your own skills and enhance your communication with your patients.

A report has value even if you find good vision and no defects but it has obvious importance if you find visual problems that you cannot solve with spectacles. A post examination form entitled ‘Feedback from the Optometrist about my Eye Test’ can be downloaded from www.lookupinfo.org.

Advice to carers on managing a visual impairment is covered in the next section.

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