Booklet  Examining PWLD: Section four:

Pathologies - Detection and Management

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Examining The Health Of The Eye

The instruments used for external and internal examination will be the same for a patient with learning disability as for any other patient. The technique of use may differ a little, taking into account the patient’s lack of understanding.

Bear in mind what an unusual experience an eye examination is. Ophthalmoscopy in particular involves unfamiliar procedures. A complete stranger places his or her head very close to you, in the dark, and shines a bright dazzling light into your eye so that you cannot see what is going on. At the same time, the stranger asks you to look at something in front of you and then puts his or her head in the way so that you cannot see it! When you appreciate the technique from the patient’s point of view, you may find it easier to make changes to the way you carry out the examination.

First of all, explain what you are about to do. Let your patient experience the ophthalmoscope beam with the room lights dimmed rather than off. Tell the patient that you are going to get very close. It is essential that you place your hand between the ophthalmoscope and your patient’s head. Your patient may not understand the importance of keeping still and if he/she suddenly moves forward, the ophthalmoscope must hit your hand and not the patient’s head.

Many patients do not understand the concept of keeping their eyes open. Generally, closing one’s eyes is a positive action, while opening them is done by a relaxation of the muscles. So if you ask a patient to open their eyes, he/she may very well shut them tight. As far as he/she is concerned, they are doing what you asked them, doing something positive with their eyes, which means shutting them! In this case, the more you and the carer insist, the tighter shut the patient’s eyes will be! Instead, ask your patient to look at something. The carer is often the best fixation target. Ask the carer to keep talking; when your head gets in the way, the patient can look towards the voice.

You may need to carry out the examination in short bursts. Most patients can keep still for a few seconds and allowing a lot of breaks will increase the chance of your examination being successful.

Types Of Defects To Expect

As section 1 has made clear, ocular defects are much more common amongst people with learning difficulties than in the general population. The reasons are far from clear but the causes of the high prevalence may include: genetic or developmental deficits, physiological or biochemical deficits, poor diet (including poor absorption of nutrients), trauma (including self-injurious behaviour), and poor hygiene.

Figure 11 lists the ocular defects noted amongst 494 athletes examined at Special Olympics UK games. Ages ranged from 9 to 69 years, with a mean of 27.3 years. Overall, abnormalities were recorded in 195 (39%) athletes. Note that some individuals had more than one abnormality.

Abnormality	Number of subjects (Percentage of the total number examined, 494)
Microphthalmos	1 (0.2%)
Exophthalmos	1 (0.2%)
Blepharitis	77 (15.6%)
No lashes	3 (0.6%)
Meibomiam gland dysfunction	11 (2.2%)
Entropion	1 (0.2%)
Ectropion	2 (0.4%)
Chalazion	1 (0.2%)
Ptosis	1 (0.2%)
Conjunctival hyperaemia	15 (3%)
Conjunctival follicles	4 (0.8%)
Chemosis	1 (0.2%)
Keratoconus	4 (0.8%)
Corneal scarring	3 (0.6%)
Corneal deposits	1 (0.2%)
Desensitised cornea	1 (0.2%)
Corneal infiltrates	1 (0.2%)
Peter’s Anomaly	1 (0.2%)
Corneal graft	1 (0.2%)
Lens opacities - mild	22 (4.5%)
Cataract	22 (4.5%)
IOL	4 (0.8%)
Wide disc cupping	9 (1.8%)
Fundus vessel abnormalities	1 (0.2%)
Fundus scarring	2 (0.4%)
Drusen	1 (0.2%)

Figure 11. Ocular pathologies recorded amongst athletes at Special Olympics


In a study such as that at Special Olympics, some of the defects will be already known to medical practitioners and carers. Only one study has reported ‘referral’ rate following examination of adults with learning disabilities; this was 14%, which is considerably higher than would be expected from examination of unselected members of the general public.

There are no ocular defects that are unique to people with learning disabilities; all occur in the general population but at a much lower prevalence. Certain types of learning disability are associated with even higher prevalence of some ocular defects. For example, adults with Down’s syndrome are at 15% risk of keratoconus (prevalence in the general population is estimated to be 0.05%).

Visual Field Defects

The previous article stressed the difficulties of measuring visual fields in patients with learning disabilities. Notwithstanding the challenges, visual fields are an essential component of the examination. The prevalence of glaucoma amongst adults with learning disabilities is not known; a reasonable assumption is that glaucoma occurs as frequently as in the general population and its detection is equally important. Some medications are associated with an increased risk of field defects; the most well-known is Vigabatrin, which is used for the control of epilepsy. The incidence of field defects associated with Vigabatrin may be as high as 40%. The field defect is characterised by concentric peripheral loss, which remains when the medication is withdrawn.

Patients with conditions associated with brain injury, such as cerebral palsy, will also be at relatively high risk of visual field defects and although in these cases the defect will be non-progressive, it is important that carers are aware of the defect. A field defect in cerebral palsy is likely to be homonymous and may be hemianopic, consistent with the affected side.

Eye Movement Disorders

Nystagmus, which has prevalence in the general population of about 0.1%, is much more common amongst people with learning disabilities; reported prevalence is around 4%. However, the prevalence amongst people with Down’s syndrome may be as high as 15%. The impact of nystagmus is poorly understood by parents and carers and it is reasonable to assume that the condition has the same implications for people with learning disabilities as for members of the general population.

People with cerebral palsy are at high risk of disorders of eye movements (which may occur alongside nystagmus), that is, difficulties in making eye movements, and/or in sustaining fixation. The inability to make eye movements must constitute a significant impairment that will hinder learning, concentration and of course, social interactions. As eye care practitioners, we are poor at assessing and describing eye movement difficulties, and this is an area long overdue for study.

Visual Perceptual Deficits

Especially amongst people with brain damage, visual perceptual deficits are relatively common, and, even when acuity is good, form a type of cerebral visual impairment (CVI). On the whole optometrists are poorly trained in the recognition of CVI, which is a field only recently receiving significant attention amongst clinicians and researchers. CVI can exist in people without global cognitive impairment and also of course in people with learning disabilities. The optometrist needs to be aware of the possibility of deficits, even if a precise diagnosis cannot be offered. The primary visual pathway from eyes to brain terminates in the primary visual cortex of V1. From there, information passes to the other visual areas of the cortex, each of which can have quite specific roles in visual processing. The basic division of visual information is into ‘object recognition’ and ‘spatial/movement’ awareness (see Figure 12).


Figure 12. The dorsal stream (green) and ventral stream (purple) are shown.

They originate from a common source in visual cortex.

The ‘object recognition’ or ‘what’ pathway proceeds from V1 along the ventral stream, which incorporates V2, V4 and the temporal lobe. Patients with damage (or retarded development) of the ventral stream may have difficulty in recognising objects (real objects, or photographs and/or representations), identifying faces and interpreting facial expressions.

The spatial / movement or ‘where’ pathway proceeds from V1 along the dorsal stream to the parietal lobe, and involves V5 or the movement centre. Patients with damage to the dorsal stream will have difficulty in appreciating the position of objects and/or their movement, including speed and direction of movement.

Parietal lobe dysfunction can also give rise to visual deficits (and to optic apraxia). Since the parietal lobe co-ordinates information from the different senses, disruption can give rise to difficulties in attending to more than one sense at a time i.e. the patient may be able to listen or look but not both. Simultanagnosia can also be due to parietal lobe dysfunction and is a lack of awareness or more than one item in the visual field or an inability to shift attention from one visual stimulus to another.

Difficulties in mobility can be due to straight forward visual defects such as poor visual acuity, poor contrast sensitivity, visual field defects, or diplopia, but can also be due to parietal lobe dysfunction. In the last case, the problem most commonly manifests as difficulty on stairs (descending being much more difficult than ascending) and mistaking a change in colour or texture of a floor for a step. In most cases the suspicion of CVI will arise because carers describe visual problems shown by the patient and the optometrist excludes other causes (such as reduced acuity) on examination.

Reporting To Carers

The responsibility of an optometrist to refer the patient with an anomalous finding is of course the same for a patient with learning disabilities as for any other patient. In addition, since the patient may not be able to understand the implications of their visual defect, we also have a responsibility to report the results of the examination to the carers, and to other professionals involved with the patient. Even a report that vision is fully normal is useful in removing concerns. The report should include advice on how any visual problems can best be alleviated, and should be written in readily understood terms. You might like to consider a report to the patient as well.

The following aspects relating to the defect should be reported (if known)

• What the condition is and how it might have arisen (congenital, recent onset etc.).
• What the impact of the condition is to the patient (discomfort, reduced detail vision, reduced contrast, glare etc.)..
• Whether the defect is static or progressive. If progressive, what the carers should look out for and what action the carers should take in the event of progression
• Whether you are referring for medical attention and if not, why this is not needed.

The following aspects relating to managing reduced vision should be reported:

• Visual acuity (in layman’s terms) and whether moving the patient closer to the task or enlarging the task will help .
• Contrast sensitivity and whether contrast enhancement will help. Contrast enhancement can include simple modifications such as using a dark tablecloth behind white crockery, or pouring milk into a dark cup. More extensive modifications might include using a bright bold cushion on the patient’s chair to help identify it, using a rug of contrasting colour to the patient’s slippers, or buying slippers of very different colour from the bedroom carpet, highlighting the edges of steps, replacing door and cupboard knobs with contrasting colours.
• Whether glare is likely to be a problem and how it can be alleviated by (for example) positioning the patient’s chair with respect to windows, by wearing a baseball cap outdoors, by staff avoiding standing with their back against a bright window.
• Whether increased or decreased lighting, or spot lighting, will be of benefit.
• Visual fields and the position and extent of any defect. Where the patient should be seated in a group.
• If the patient has nystagmus, allow the use of the null-position and place objects appropriately. What position will be most comfortable for tasks such as viewing TV, using a computer etc.
• If the patient has eye movement difficulties, alert carers to the need to allow time and to provide as distraction-free an environment as possible .
• If the patient appears to have mobility difficulties due to parietal lobe dysfunction, he/she can best cope by using non-visual cues to the terrain. On stairs, he/she should use the banister, or bump down on his/her bottom. When walking, he/she can push a shopping trolley, shopping bag or wheeled cabin luggage; cues from arms can indicate when there is and is not a step. When holding on to an accompanying person, don’t hold hands, as hands bounce up and down, but hold onto an elbow while the arm is firmly held against the body or hold on to a belt.

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