Acquired brain injury: part 2 examining the patient with ABI.
Course code C-30936 | Deadline: May 17, 2013
Elicit the detail and relevance of any significant symptoms from patients using a variety of question types (Group 1.1.2)
Be able to access binocular vision status using a variety of objective and subjective techniques and targeted to elicited history and symptoms (Group 8.1.1)
History and symptoms in ABI
Establishing a good history in ABI entails asking the patient highly specific questions in order to identify any symptoms. Cognitive deficits associated with frontal lobe injury ((2) mean that often patients with ABI will interpret your questions literally and give a highly specific answer. For instance, the patient may not relate a question about whether they experience eyestrain when reading a book to whether they have any eyestrain when reading a Kindle, even though both are very similar activities. In fact, patients with ABI might say that they do not do much close work. However, when questioned in more detail, they might say that they have issues when it comes to keeping the text on their mobile phone in focus, or they have problems reading text messages or emails. They might also have a tendency to do such work on portable electronic devices at a closer working distance than normal (3) in order to compensate for accommodative difficulties; in turn this increases demand on accommodative and vergence function. Consequently, patients with ABI do actually experience problems with close work, but do not relate their activities as being close work. Whereas a patient without ABI would tend to volunteer their symptoms, a patient with ABI is more likely not to say anything. In the author's experience, therefore, questions should be divided into specific categories to elicit evidence of possible underlying refractive or binocular vision anomalies, as described below.
Questions relating to accommodation and refractive error
The questions listed in Table 1 relate to possible accommodative anomalies or uncorrected refractive error. Any 'yes' answers might indicate a requirement for a refractive correction or accommodative training in order to reduce these symptoms. An inability to keep images clear at distance can indicate an uncorrected refractive error, as well as perhaps an inability to maintain stable accommodation. An inability to keep print clear at near can indicate accommodative insufficiency and/or accommodative lag, as the patient is not able to 'sustain' their accommodation at near. (4) An inability to focus easily from one distance to another can indicate accommodative infacility and/or accommodative lag, as the patient is not able to alter their accommodation easily from one distance to another. (5)
Questions relating to binocular status
The questions listed in Table 2 relate to possible anomalies of binocular vision. All of these questions investigate if there are difficulties with fusion or vergence function. Any 'yes' answers might indicate a requirement for prismatic correction either using Fresnel prisms or ground prism. Some patients may be receptive to fusional training. A tendency towards intermittent double vision might indicate the presence of a heterophoria which is prone to decompensation and/or the presence of convergence insufficiency. (6) In the case of intermittent double vision, fusional ranges and stereopsis values might also be reduced. Permanent diplopia in one position of gaze is usually related to a muscle paresis following ABI and can be compensated for by use of Fresnel lenses or sectorial patching.
Questions relating to photophobia/light sensitivity
The questions listed in Table 3 (page 60) relate to possible problems with photophobia. Such patients often benefit from the use of highly specific tints in order to reduce these symptoms. Whereas normally a practitioner might choose a tint to suit the colour of the frame the patient has chosen, in ABI the colour and depth of tint has to be highly specific to the requirements of the patient. (7) Also patients might benefit from the use of a broad brimmed hat to help reduce overhead illumination. (8)
Questions relating to oculomotor function
The questions listed in Table 4 relate to possible problems relating to oculomotor function, in terms of the patient performing accurate pursuit and saccadic eye movements. Any 'yes' answers might indicate the possible need for vision training in order to improve the patient's ability to make accurate pursuits and saccades and so improve their reading. (9) Indeed, keeping your place when reading relies on the eyes making a series of fixations and saccades as they move across the page. If these saccades are not accurate, the patient might lose their place when reading, skip words or lines, or might read the same line twice. A coping strategy to help compensate for this might be for the patient to use their finger to keep their place when reading.
If a patient misreads letters or words, they might seem to be making accurate eye movements in terms of fixations, but these fixations are not actually accurate, causing the patient to incorrectly identify a letter. For example, if they are to tell the difference between a letter 'o' and a letter 'c', as they make a fixation movement they have to be able to move their eyes appropriately to find the gap in the letter 'c'. If they are not able to move their eyes accurately, they might miss the gap and misread the letter. This series of fixations and saccades form a 'scan pattern'10 allowing inspection of a letter so helping in its identification. (11) If they misread the letter, they may well misread the word. If they misread the word, the sentence will not necessarily make sense and their comprehension will not be as good as expected. This ability to make accurate pursuits and saccades can be disrupted in ABI. (12)
Assessment of ocular health
Ideally, ocular health should be assessed using indirect binocular ophthalmoscopy methods for the fundus and slit lamp for examining the anterior eye. Where it is not possible to get the patient into a slit lamp, for example because of postural problems, then either direct ophthalmoscopy should be performed or head-mounted binocular indirect ophthalmosocopy, to examine the posterior eye. A tearscope or Burton lamp, in conjunction with fluorescein, can be used for assessment of possible dry eye. (13)
Measuring VA in ABI
Measurement of VA is ideally done with a LogMAR or traditional Snellen chart. It is recommended that patients are instructed to read 'the lowest line you can read easily', because patients with ABI tend to fatigue easily and this makes the measurement as simple as possible. It can also be useful to point to and/ or highlight the letters on the chart, as this will make it easier for the patient to maintain their attention while you are measuring VA. Where the cognitive capacity of the patient is compromised post-injury, Sheridan-Gardner, Lea pictures, Kay Pictures (Figure 1) and preferential looking tests such as the Cardiff Acuity Cards (Figure 2) can be used (see Optometry Today, March 9, 2012 for more details of these charts). (14)
Measurement of cover test movement is best done with a target to which the patient will easily attend. Ideally this is the smallest letter which can be seen at near or at distance by both eyes. However, if the patient is not able to remain attentive, a spotlight target will suffice. As patients with ABI have issues sustaining attention, remember to provide active encouragement and repetition of instruction. Sometimes it is easier to maintain a patient's attention using a flashing light and/or auditory stimulus, and this method has successfully been used in the assessment of some neuro-developmentally delayed populations. (15)
When assessing ocular motility, the instruction given to the patient is to keep their head still and to follow the light from your pentorch with their eyes only. Instruct the patient to tell you if their eye movement is ever painful or if they see two lights in any position of gaze. Before starting ocular motility, note any characteristic head posture, ptosis or anisocoria as key signs of possible neurological damage. Remember to keep your head behind the light so that you are more likely to see any asymmetry of the Hirschberg corneal reflexes in different positions of gaze. (16) Remember that the position of gaze where the corneal reflexes are most asymmetric indicates a possible paresis; the muscle in the paretic eye moves less than the contralateral agonist, which will overact according to Herring's Law of equal innervation. (17)
Measurement of fusion/ binocularity
As mentioned previously, patients with ABI can tend to fatigue easily, so the practitioner should decide on which probes will give the best indication of fusion and binocular stability. When performing a cover test, remember to ask about 'phi movements.' This is where the patient sees the target move, though you do not see any eye movement. This can also be noted in the presence of a deviation and can be used to determine the size of deviation, the direction and the speed and smoothness of recovery. Near point of convergence (NPC) is measured using a RAF rule, although in the author's experience, this can just as effectively be measured using a fixation target such as a pen or a budgie stick. Decide whether you want to take more than one reading, since repeats might cause undue patient fatigue so that you are not able to complete the eye examination.
Binocular stability can be measured using the Mallett unit. (18) Movement or intermittent flashing of the nonius markers indicates binocular instability. Displacement of the nonius markers on the Mallett unit indicates a fixation disparity, and the prism required to align the markers is an indication of the associated phoria. On the Mallett Unit, note that it is not always possible to align the bars perfectly as some fixation disparity curves do not pass through a null point. Also, note that prism is only to be prescribed when it makes a difference to the patient's symptomology, and the author advises that this fact is noted on the patient's record.
Fusional ranges can be measured using a prism bar or phoropter head. It is recommended that the blur point, break point and recovery point are measured at both distance and near and that measurements are taken for each with the same method; prism bar measurements are not directly comparable with measurements taken in a phoropter as a prism bar uses step prism measurement of fusional ranges, while a phoropter uses rotary prisms.
Stereopsis can be measured using the Titmus fly, Randot Butterfly, TNO and modified Frisby test. (19) Note that the Titmus and Randot tests are a measure of 'local' stereopsis while the TNO test (20) is a measure of 'global' stereopsis. Local stereopsis tests are easier for a patient as they only have to fuse images over a small area of visual field. Global tests are more challenging as the patient has to fuse images over a much larger area of visual field. However, in patients with ABI, the most important element is obtaining some measure of stereoacuity. (21)
Measuring accommodation in ABI
Where appropriate for age, measurement of accommodation in patients with ABI can be done using a RAF rule, although, in the author's experience, accommodation can be just as effectively be measured using N5 print or an appropriate size of print, which can be seen clearly in a book or paragraph of text. Ask the patient to look at one word, and then, as you bring the print closer to them, ask them to tell you when that word becomes blurred. Measure the near point of accommodation (NPA) in centimetres, noting the size of print used. Make a decision as to whether you want to repeat the test three times or whether one measurement is enough depending on patient fatigue.
It is important to assess all aspects of accommodation clinically, (22) since, if only amplitude of accommodation is assessed, it is possible that other accommodative dysfunctions are missed. (5) Accommodative facility is a measure of the patient's ability to focus easily from one distance to another. Accommodative facility can be measured using a [+ or -]2.00DS flipper, with the patient reading N5 print at 40cm and counting the number of flips the patient can make within a minute, each time being asked to keep the print clearly in focus before making the next flip. This is performed for each eye individually and if appropriate with both eyes together, again with consideration to conditions of fatigue. If the patient is not able to clear a [+ or -]2.00DS flipper, a [+ or -]1.50DS flipper or a [+ or -]1.00DS flipper can be used instead. If the patient is not able to perform the test for a minute, the author suggests scaling down the time they do the activity to 30 seconds or 15 seconds. If you do not have access to an accommodative flipper, placing a +2.00DS lens and then -2.00DS lens in turn on top of the subjective refraction is an alternative option. Ensure that you note the method you have used, and the lens power, for later comparisons with future measurements.
Accommodative lag can be measured using a number of near retinoscopy techniques (23) although the author tends to favour the use of monocular estimation method (MEM) retinoscopy. Near retinoscopy cards can be used and technological apps on electronic devices are also now available, for example 'Baby-view' for the iPad and iPhone. (24)
Pursuit-saccadic eye movements
Whereas ocular motility testing measures the ability of the extra-ocular muscles to move in the different positions of gaze, the pursuits-accadic eye movements required in reading can be measured by using the Northern State University College of Optometry (NSUCO) test. This test measures the patient's ability to perform pursuits and saccades while standing, by assessing whether the patient is able to keep their head and body still while performing a specific task involving pursuits and saccades. (25)
Neuro-developmental approach to binocular vision assessment
Whereas the orthoptic approach to binocular vision assessment is to have pass/ fail criteria for each measure of function, a neuro-developmental approach looks at the functioning of the binocular vision system as a whole. So for example, in a patient with ABI, a reduction in amplitude of accommodation to just below normal values, together with phi movements on cover test and a NPC of 7cm, might indicate a binocular vision anomaly which gives rise to symptoms that wouldn't necessarily occur in a patient without ABI. Primarily this is because the binocular vision system is more fragile in such patients, and it is the overall performance across the whole of the binocular vision system which is of greater significance than individual results. (26)
Measurement of visual field
Automated perimetry is the testing method of choice. However, if the patient does not have the cognitive capacity to cope with this test, confrontation testing can be used and a hierarchy of targets can be implemented depending on the patient's ability, including hand motion, finger motion, finger counting and matching, saccades to moving fingers/ targets and a colour brightness comparison of a red target, either moving across all four midlines or detecting four red targets in each quadrant equidistant from fixation. (27)
Patients with ABI require comprehensive assessment of visual function, which includes a highly specific and tailored history to elicit symptoms and problems that the patient might be experiencing. Many assessment techniques are similar to that performed in routine examinations, with adaptations required, so be mindful of induced patient fatigue. However, results should be considered collectively instead of individually. This forms the foundation for directing patient management, which will be discussed in the next part of this series.
References Visit www.optometry.co.uk/clinical, click on the article title and then on 'references' to download.
Exam questions Under the new enhanced CET rules of the GOC, MCQs for this exam appear online at www.optometry.co.uk/cet/exams. Please complete online by midnight on May 17, 2013. You will be unable to submit exams after this date. Answers will be published on www.optometry. co.uk/cet/exam-archive and CET points will be uploaded to the GOC on May 27, 2013. You will then need to log into your CET portfolio by clicking on "MyGOC" on the GOC website (www.optical.org) to confirm your points.
Reflective learning Having completed this CET exam, consider whether you feel more confident in your clinical skills--how will you change the way you practice? How will you use this information to improve your work for patient benefit?
Mark Menezes is an optometrist in private practice. He teaches paediatrics and binocular vision clinics at the University of Aston, as well as teaching a module on Visual Aspects of Brain Injury Rehabilitation as part of the MSc course at the University of Birmingham, since 2010. Previously he was part of a team which set up a binocular vision anomalies clinic dealing with visual aspects of dyslexia at the University of Manchester. Prior to this, he gained Fellowship of the Australian College of Behavioural Optometrists in 1992. He is a founder member of the British Association of Behavioural Optometrists. He has lectured both nationally and internationally on the subjects of Visual Aspects of Dyslexia and Visual Aspects of Brain Injury Rehabilitation. He is also a member of the Neuro Optometric Rehabilitation Association, and is in the process of working towards his Fellowship. The author would like to credit Professor Ken Ciuffreda, Dr Ivan Wood, Curt Baxstrom OD, Penelope Suter OD, Bob Edwards OD and Stephen Leslie for their help and guidance.
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Table 1 Elicit problems relating to accommodation and refractive error Types of questions to ask to elicit problems relating to accommodation and refractive error When looking far away or when watching TV, is your vision always clear or is it sometimes or always blurry? When looking close up, such as when reading or using a computer, is your vision always clear or it is sometimes or always blurry? When using your mobile phone, iPad, DS or any other electronic device close up, is your vision always clear or is it sometimes or always blurry? When looking from one distance to another, such as when looking from your mobile to the TV, do things always come clear straight away or do they sometimes take a while to come clear? When looking from one distance to another, such as when looking from reading or the computer to far away, do things always come clear straight away or do they sometimes take a while to come clear? Table 2 Elicit problems relating to binocular status Types of questions to ask to elicit problems relating to binocular status Is your vision always single or does it sometimes become double? Do you ever get double vision when looking in a particular direction, such as to the left or to the right? Do you ever experience dizziness or vertigo, or problems with your balance, particularly when walking on uneven surfaces? Do words ever become double when you are reading or looking at texts or using on the computer? Table 3 Elicit problems relating to photophobia Types of questions to ask to elicit problems relating to photophobia Are you troubled by bright light, such as in the mornings on sunny days? Are you troubled by bright light, such as when shopping in super markets or shopping centres? Are you troubled by room lighting, which is too bright, or by fluorescent lighting? Are you troubled by strobe effects of light, such as when light passes through trees or fast moving lights such as you would get if on the London Underground? Are you troubled by car headlights at night? Table 4 elicit problems relating to oculomotor function Types of questions to ask to elicit problems relating to oculomotor function Do you ever lose your place when reading? Do you ever skip lines when reading or read the same line twice? Do you ever use your finger to keep your place when reading? Do you ever misread letters or words? Do you ever read something and then are not able to remember what you have read? Do you ever have issues keeping your place when reading text messages or composing text messages or emails?
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|Title Annotation:||CET: 1 CET POINT|
|Date:||Apr 19, 2013|
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