Binocular Vision in full 1 powerpoint.pptx

1. Introductory Lecture Binocular Vision Emma Percy  Indicative Content 8077 Introduction to Binocular Vision General introduction to binocular vision Paediatric vision and amblyopia and the development-plasticity period Monocular and binocular eye movements...

1. Introductory Lecture Binocular Vision Emma Percy  Indicative Content 8077 Introduction to Binocular Vision General introduction to binocular vision Paediatric vision and amblyopia and the development-plasticity period Monocular and binocular eye movements Localisation - monocular and binocular Egocentric localisation and the concept of the cyclopean eye The concept of corresponding points, Panum’s fusional areas, stereopsis, rivalry and the horopter Testing of Normalities and Assessment Case history and observations, paediatric visual acuity testing and refraction Testing for phorias and tropias: cover test, Hirschberg, Krimsky, Bruckner Ocular motility Hess/Lees Screen - results and interpretations Near response – convergence, stereopsis, pupil responses, assessments of accommodation (NRA, PRA, amplitude & facility) Measurement of AC/A and fusional reserves Fixation Disparity, types, and relevance Abnormalities and their Management Prism adaptation Introduction to binocular vision anomalies, identification, and management Assessments Component 1: Practical Examination and VIVA (50%) (Week 13, Semester 2) An OSCE consisting of four stations that will examine your ability to undertake testing of a patient's binocular vision. The examination will last one-hour and will be undertaken in Week 13 of Semester 2. This component assesses the following learning outcomes PT1, PS1, PS2, PS3 (PT Personal and Transferable Skills; PS Professional Skills, Values and Behavior) Component 2: Unseen Examination (50%) (Week 14, Semester 2) A one-hour examination consisting of both multiple choice and short answers questions. The examination will allow the you to demonstrate their underpinning knowledge of binocular vision, its development, and common management strategies. The exam will be taken in Week 14 of Semester 2. This component assesses the following learning outcomes RKC1, RKC2 (Research, Knowledge and Cognitive Skills). Students are required to achieve a 40% pass mark in each component to pass the module. Assessment component 1 This will be a 4 station OSCE – similar in style to Clinical Optometry OSCE in year 1. You will be asked to perform 4 tasks each within 15 minutes. These tasks will be based around mainly the things we have covered in our practicals but will require theoretical knowledge from the lectures. There will be a peer assessed mock OSCE in week 12 in our practical session before the OSCE takes place in week 13 Assessment component 2 This will be a 1 hour written exam that This exam will include SAQs and This exam will be in week 14 with other could cover any of the theoretical or MCQs Sem 2 exams practical knowledge that has been taught  Lecture Titles Binocular vision purpose Diplopia Mechanical Palsies ​ Binocular vision history Suppression Nerve Palsies​ taking Accommodation Additional BV Binocular fusion and convergence Conditions Are their eyes straight? testing +conditions Case study​ Cover test and Corneal AC/A Ratio and fusional Revision session​ reflexes reserves Binocular vision Eye movements development Motility BV development 2 – Hess/Lees screening including amblyopia Amblyopia Phorias Paediatric Vision Tropias Assessment Expectations BV is difficult, there is a whole new vocabulary, a new set of practical skills, requires across optom knowledge; pathology, development, visual perception, neurology and clinical optometry. BV is a build-up module, it might take you until the end to truly understand something from the first lecture. BV can’t just be memorised it includes concepts and ideas that require a deeper understanding BUT You use the skills to help the most vulnerable Can have a huge developmental impact Can have an incredible visual increase And it will help you literally save lives. Quick definition quiz Take a few minute to consider the answer to each of these What is accommodation? What is the near triad? What is convergence? What is divergence? What is vergence? What is binocular vision? Binocular Vision is the ability to use both eyes to create a single percept. Full and complete binocular vision relies on several factors including Our anatomy The ocular movements – The Motor System The brain’s ability to receive and interpret these signals. –The Sensory System 1. Anatomy Two anatomically aligned eyes are required for a binocular percept. This can be disturbed due to developmental issues pre or post birth or due to destructive disease or through trauma or accident.  This is the functioning of the binocular system not working. So even though anatomically everything appears present and correct, its ability to function is somehow lessened. These are often linked to the function near triad – think convergence, accommodation and pupil 2. Motor size. Conditions like convergence insufficiency, System accommodative excess (which we will cover later) all fall into this category. Occasionally urgent medical things cause this system to be disrupted to such as things that could impact the nerve supply like intracranial pressure (ICP) or tissue based tumours. 3. Sensory system This system is based around the eyes receiving equal images in terms or quality, size or location. So this can be disturbed by anisometropia (different prescriptions between eyes) which can lead to aniseikonia (different image size). This is the system we are talking about when we discuss amblyopia This is the system we are often considering incremental changes in binocular for example measuring increases in; Stereopsis (3d imaging) Motor skills at near Visual acuity/ contrast sensitivity improvements. Retinal Disparity Our two eyes work together to view a single perception. During vision we stimulate "retinal corresponding points" that fall on an area known as the horopter. The region over which we perceive single vision is known as "Panum's fusional area". An area outside of this region would give us diplopia.  The horopter is the points within the visual space that stimulate to corresponding points between the eyes. This is the system that allows us to have single vision. This circle shown in the theoretical horopter of Vieth-Muller Circle. When it is measured experimentally it appears more curve like in nature. The horopter is present in vertical and horizontal planes. The Horopter  Panum’s Fusional Area These are areas consider as part of cortical processing. We call it a retinal area for aid when visualising. They are small horizontally oval areas surrounding any point that means any disparity between images will remain as single percept presuming they stay within Panum’s fusional area. An object outside of Panum’s area stimulate widely disparate retinal points resulting in physiological diplopia. Panum’s fusional area. Uncrossed disparity images Object of fixation Panum’s fusional area. Crossed disparity images Panum’s fusional area Panum’s areas allow for a small amount of deviation between these eyes (around 0.25D). This is an allowance we all have irrespective of binocular vision anomaly. Panum’s fusional area size will change with the size of the object and the eccentricity. The Cyclopean Eye This is an older concept that suggests that during binocular fixation as the eyes are usually pointing in different directions. Yet objects are judged by single direction. The theory is that there is a central location in the head that allows for directional judgements. Anatomical positioning These are only BINOCULAR positionings, for example if someone was to cover one eye and therefore – dissociate the eyes the position of the remaining open eye would likely change. D is the total sum of accommodative convergence, proximal vergence and fusional vergence. Fusional Vergence – The ability to bring the eyes together usually specifically when looking at distance. Proximal Vergence- Focusing on an object depending on where it is in the world Accommodative convergence- The function of the near triad – an accommodative target causing accommodative exertion leading to more convergence.  This definition will get deeper as we move through this module but for Binocular now your understanding of this should be the correct and complete combination of the two images simultaneously provided by our two eyes, fusion allowing us one single percept/image. Binocular vision classification There are lots of words here that will be new to you. Binocular vision is a block-by-block subject and you will find that sometimes you will have to readdress the basics to be able to understand the next element. Typically the position from “active” binocular focus whether at distance or near will change if the eyes are dissociated, this is classed as a heterophoria and small compensated heterophorias are completely normal. In the rare cases where dissociated position is the same as active position this is known as orthophoria another normal binocular finding. If WITHOUT complete dissociation the position of the eye is different between the eyes, meaning binocular fusion is not possible this is then known as strabismus or heterotropia.  Comitant a.k.a concomitant deviation – Same size in every direction at a given distance. Comitance Incomitant- Vary on direction or gaze even at same distance. Can also change depending on “fixing” eye. Incomitant deviations are usually more concerning and if new can link to active pathology requiring urgent treatment. Deviation directions ESO – IN EXO – OUT Hyper – Up Hypo – Down Cyclo – Around. These words can be linked to tropias or phorias for example, I could describe an esophoria which would mean when the eyes are dissociated the eyes are moving in (convergent) One of the issues we have with BV is that there are several ways to name the same thing so for example this is typically called a right or left esotropia which can be written in several ways too. RSOT, RESOT etc. This is even more pressing when we are considering vertical deviations as a right hypotropia and a left hypertropia are technically the same thing and so we must decide how we classify and typically this comes down to the nature of the condition causing the deviation. Heterophoria classification Remember definition – Eyes that when dissociated and not in binocular fusion are deviated. Latent deviation, unmanifest. 1. Direction of deviation – Eso, Exo, Hypo, Hyper, Cyclic 2. Fixation distance – Distance (6m) or near (30-50cm) 3. Compensation – Ability to control this deviation – This is crucial as this is the difference between whether this is a physiological condition with no treatment required or whether this is likely to be symptomatic and problematic to the patient.  This is a term ONLY used for heterophoria. There is NO way to compensate a tropia/strabismus. This related to the patient’s ability to overcome the heterophoria and remain in binocular fusion Compensation This can depend on circumstance and stresses on the system. A decompensated phoria is likely to be symptomatic but may only appear so in certain situations. Heterotropia/Strabismus classification Remember definition – Eyes that are deviated with no or limited binocular fusion without dissociation. Manifest. 1. Direction of deviation – Eso, Exo, Hypo, Hyper, Cyclic 2. Fixation distance – Distance (6m) or near (30-50cm) 3. Constancy – Constant/ Intermittent 4. Eye preference (consider alternating) 5. Accommodative state – (This is something we will address later)  This is a term ONLY used for heterotropia's/strabismus. A phoria by it’s very nature cannot be constant, so it’s constancy does not need to be labelled. Intermittent strabismus occurs when patients have binocular fusion most of the time Constancy Intermittent strabismus will occur when the normally adept visual system is under stress but the visual system still needs to have some underlying issues for this to be present at all. When a strabismus isn’t constant ensure to ask question about duration of intermittent strabismus and what causes the strabismus to become present.  This is a term ONLY used for heterotropia/strabismus. By its nature heterophoria is a binocular condition with both eyes affected Eye Most strabismus have only one eye affected but in certain conditions there is a type of strabismus preference called alternating strabismus in this case it’s important to know which eye is the preference In that condition the preference can change depending on fixation distance, gaze direction or refractive correction. Conclusions This module will cover a range of topics surrounding binocular vision and vision development. This module will be assessed in 2 ways; a practical exam in the form of an OSCE and a written paper. Today we have learnt about some of the basic binocular vision terms and some of the major classifications to consider.  2. Binocular Vision History Taking and early observations Emma Percy  DO NOW Think about heterophoria and heterotropia from last time. What do those words mean again? Heterophoria classification Remember definition – Eyes that when dissociated and not in binocular fusion are deviated. Latent deviation, unmanifest. 1. Direction of deviation – Eso, Exo, Hypo, Hyper, Cyclic 2. Fixation distance – Distance (6m) or near (30-50cm) 3. Compensation – Ability to control this deviation – This is crucial as this is the difference between whether this is a physiological condition with no treatment required or whether this is likely to be symptomatic and problematic to the patient. Heterotropia/Strabismus classification Remember definition – Eyes that are deviated with no or limited binocular fusion without dissociation. Manifest. 1. Direction of deviation – Eso, Exo, Hypo, Hyper, Cyclic 2. Fixation distance – Distance (6m) or near (30-50cm) 3. Constancy – Constant/ Intermittent 4. Eye preference (consider alternating) 5. Accommodative state – (This is something we will address later) Learning Intentions Understand the importance of a thorough binocular vision history in the optometric examination process. Develop skills in eliciting a comprehensive case history being aware of the key differences in a binocular vision history Understand the specific terminology considered with a binocular vision history. Understand basic observations of alignment including tests; Hirschberg, krimsky and Bruckner Exercise You have 3 minutes Write down a bullet point list of everything you ask in a history and symptoms Then circle anything you think could link to binocular vision A good Elicit main and subsequent concerns from the patient history and Gain rapport and trust with patient. Be tailored to patient and patient’s complaints symptoms Be thorough Be open BUT controlled should: Lead to a tentative diagnosis Areas of extra 1. Symptom Check concern in a BV Specific symptoms should be emphasized history and Onset is crucial –Where + When, symptoms 2.Environment 3.Family History 4.Birth History 5. Ocular History 6. General Health Specific conditions and their links to BV  Diplopia Headaches Blurred Vision Asthenopia Poor depth perception 1. Symptom Dizziness Check Monocular eye closure Developmental delays or changes in education  Diplopia is the occurrence of seeing 2 images instead of one, when only one is present in the real world. Diplopia in Binocular vision specifically is examining BINOCULAR DIPLOPIA which is where the images seen are the two Diplopia disparate images from each eye. Meaning if you cover one eye, one of the images disappear. What are some pathologies that give monocular diplopia? Diplopia When asking about diplopia the following elements need to be considered Monocular or Binocular Onset Constancy Direction – Horizontal, Vertical or Diagonal  Common symptom that you discussed in OCPCS1 in 1st term. In BV can link to uncorrected BV problems BV linked headaches tend to worsen as day goes on or occur during specific Headaches activities. For example if near decompensated heterophoria then the headache will occur when reading. Severe headaches can also be linked to more significant BV problems like nerve palsies Blurred Common symptoms of Vision heterophoria even after refractive error has been corrected. (Lasik note) Typically, more noticeable at certain distances or with certain tasks. Can also be a symptom of accommodative or convergence issues. Asthenopia Asthenopia typically considered to be defined as eyestrain but can link to overarching “eye” complaints- pain, tiredness, soreness, headaches. It is an all encompassing symptom. Would usually ask the patient “Do your eyes ever feel tired or strained” Again need to consider the cause of this problem considering onset- When/Where. This can link to BV conditions such as amblyopia, accommodative issues, convergence issues, heterophoria and reading difficulties. So it’s important to question and reiterate, consider rephrasing the question, ensure to link to activities. Poor depth perception Some adults will directly complain of poor depth perception or give examples of such. “Struggling to work out distances when walking” But can also directly ask this question to adults. However often people with longstanding binocular vision issues will not recognise because there are many monocular cues to depth perception. Can also ask parents if child is clumsy or seems to have an incorrect grabbing motion. Often easy way with a child is to get them to demonstrate. Dizziness Dizziness can be a symptom of Reminder Incomitant- Vary on an incomitant heterophoria. direction or gaze even at same Dizziness can also be a symptom distance. Can also change of new onset serious binocular depending on “fixing” eye. vision problems such as nerve palsies or intranuclear ophthalmoplegia. NB: It is also important to consider recent changes of spectacles here especially with anisometropia as this can often result in a dizzy sensation Monocular eye closure Ask parents “Does your child ever seem to close one eye when focusing on things” Or directly ask older children or adult – “Is it sometimes easier for you to see if you close one eye” This can be linked to multiple conditions including; uncorrected refractive error and pathology especially glare inducing pathology e.g cataracts or polycoria. However in terms of BV this can often links to binocular issues such as amblyopia, convergence or accommodation issues or reading issues.  Asking parents “Have they met all their developmental milestones” –In later lectures we will discuss typical milestones and your questioning can be more pointed Developmental based of age of child. delays Some developmental conditions link directly to binocular vision defects. These include; Albinism, Autism, Cerebral Palsy, Down Syndrome, Dyslexia and Fragile X Syndrome  The environment in which someone is in can impact their binocular vision system hugely. For example, lots of optometry students come to university assuming they have normal binocular vision and then they begin working on slit lamps and using other techniques that can dissociate the eyes and find that this causes previously 2. hidden symptoms. Environment This is true in numerous professions and can result in new examinations, diagnosis and treatments. Meaning we should question around any recent changes to profession or hobbies that could disrupt the binocular vision.  2. Environment This is also crucial in terms of education for children. One of THE most common symptoms for children is avoidance. If something becomes uncomfortable for a child, they won’t usually raise the issue but avoid it. For example a child who loved going on their Ipad or reading but suddenly doesn’t. A child will also make natural adaptations to the environment and sometimes things that may see ‘positive’ to parents are signs of negative changes. For example a child who used to sit close to the tv has now moved away unprompted. So, a BV exam needs direct questions about a child’s environment, sometimes these questions may be repetitive in nature but will help to evoke any hidden responses. 3. Family History This is a HUGE indicator for certain binocular vision concerns especially strabismus and amblyopia. Direct questioning to patient or carer depending on age/ ability of patient. Do your parents/ siblings wear glasses? When did they start wearing glasses? (Looking for childhood to give indication of specific BV issues) Does anyone in your family have a lazy eye? Do you know of anyone in your family with a turn in their eye? Did anyone have eye surgery as a child in your family? Did anyone wear patches as a child? Familial links Accommodative esotropia 26% have family first degree relative 15% in infantile esotropia 12% in anisometropic esotropia 4% in exotropia 4. Birth History This is a specific set of questions that we ask to or about paediatric patients and also in any case where we are concerned about a suspected binocular vision problem. Were they full term? (Prem babies have higher risk of ocular pathology and hypermetropia, anisometropia and 5x increase of esotropia. Birth weight (links to small weight leading to lower visual function) Any birth trauma or assisted birth? E.g Forceps can interrupt the function of the extraocular muscles and lead to strabismus 5. Ocular history As with typical case histories we need to ask about ocular history but we add a few additional questions similar to family history. Have you ever had any ocular surgery – especially squint correction Have you ever had patching? Have you ever had prisms put in your glasses? Have you ever been given eye exercise to do? Any recent or previous ocular or head trauma? 6. General health As with typical case histories, we ask about overall health issues but with specific focus Diabetes Thyroid issues Neurological conditions e.g. stroke, MS, Parkinsons All of these conditions can impact the risk of nerve damage which can lead to nerve palsies. Diabetes commonly causes third nerve palsy Thyroid issues can lead to proptosis which impacts the muscles causing mechanical restriction Neurological issues can also cause nerve palsies or the visual field damage caused by these conditions can interrupt the binocular vision system. Binocular Vision Testing What tests do we do in binocular vision?  Remember the 3 elements of binocular vision anomalies 1. Vision 2. Visual Acuity 3. Refraction 4. Overall eye alignment (Hirschberg, Krismky, Bruckner) Binocular 5. Cover Test (and it’s variations) 6. Ocular motility vision 7. Convergence a) Near point testing b) Jump 8. Accommodation a) Amplitude b) Facility c) Accuracy 9. Pupil reflexes 10.Stereoacuity 11.Suppression tests (Global/Foveal) 12.Fixation disparity  1. Anatomy 2. Motor System 3. Sensory system Remember each of these systems, each of those Binocular tests will be facilitating one of those systems. Typically, anatomy issues are ruled out in pathology which in a truly “only binocular vision vision exam” IS NOT done but should be initial consideration. Consider orthoptists or optoms examining for BV only in hospital someone else will look at pathology first. Binocular vision tests then check the motor and sensory system. As we go through, we will be discussing  1. Hirschberg Objective- 2. Bruckner 3. Krimsky Preliminary ocular First, we will discuss some methods we use to assess elements of binocularity alignment checks within patients. These are methods that are useful as initial examinations ,especially in children or patients with additional needs may be harder to assess.  Hirschberg AKA corneal reflex test Typically done by health visitor or nurse a basic ocular alignment check. Benefits Can be done from any age Good for patients with poor vision Good for patients with poor fixation Test At 50cm sitting centrally and height aligned with the patient shine a bright ideally circular and complete light at the patient. A bright pen-torch is usually best for this. Both corneas should have a light reflection – readjust if they don’t Observe the reflexes and analyse. Can be done in any lighting condition.  A normal and typical alignment the reflection will appear in the exact Hirschberg same position in each pupil. As shown below. This position will not necessarily be central this will depend on your results position and their focus. Ensure you are not too close to induce excessive convergence or too far to reduce fixation ability. Notice here the patient shows another reflection above the one highlighted- ensure the corneal reflex you are focusing on is from the light you shine and not room lights. Other Hirschberg results This number can vary depending on where you read typically considered roughly 20dioptres per mm but anyway between 15-22 prism dioptres can be seen in literature. What is this? What is this What about this? Krimsky pics This test is an addition to the Patient remains fixated on a bright light at Hirschberg test. Only if manifest a small distance roughly 50cm. squint is observed A prism bar is placed in front of the deviating eye until the reflex is recentred- This involved performing the there are modified versions of this which Hirschberg test and if the corneal split the prism across both eyes or use reflexes are deviated using a the opposing prism on the fixing eye. prism bar to correct the reflex to Presuming typical format placing in front estimate the size of the deviation. of deviating eye use appropriate prism to correct Base in for exo, out for eso, down for hyper, up for hypo. Bruckner This test has a similar procedure but is used to assess the light reflexes from the retina. Instructions Darkened room Using Ophthalmoscope at roughly 1 metre to begin but should be repeated at varying distances. Ask patient to look at light Bruckner Results In normal findings the eyes will shine equally. At SHORT distance (1m) When strabismus is present the fixing eye has a darker reflex than the deviated eye. In this image the left eye is likely to be the amblyopic/deviated one. This test will also allow us to quickly assess the media and give an indication of any opacities in the lens of leukocoria. Bruckner results Bruckner at short distances can test/indicate for cataract (or other This image shows a posterior cataract – pathology), or strabismus while most typical congenital cat further distances allow to assess myopia/hypermetropia. This test can be performed on a sleeping baby/child – Open upper lids with thumb and forefinger and perform the close version as described. At larger distances focusing just on The eyes will reflexively open in a small child if head the brightness the darker reflex is is stabilised and up and down movement is repeated. likely to be the one with the higher prescription (+ or -) Leukocoria This is when one of the pupil reflexes appears white in nature. This is one of the most concerning signs we can see during paediatric assessment as it can indicate retinoblastoma, a serious life threatening paediatric cancer. However it can also be indicative of less concerning conditions such as congenital cataract or toxocariasis but if Leukocoria is ever seen full assessment is required and if not possible or findings indicate significant pathology emergency referral for assessment is required. Conclusions Importance of a thorough binocular vision history emphasized Enhanced skills in eliciting a comprehensive case history, considering binocular vision nuances Familiarity with specific terminology related to binocular vision Proficiency in basic observations of alignment through tests like Hirschberg, Krimsky, and Bruckner Improved ability to assess binocular vision and eye alignment effectively in optometric examinations  3. Binocular Vision Cover testing and amblyopia introduction. Emma Percy Learning Objectives 9921 Today’s lecture will further our understanding of ocular alignment We will understand the theory behind the multiple versions of cover test and how to quantify the results. We will discuss the expected results based off varying underlying ocular alignment issues. Discuss prism measurement for tropias and phorias Deviation directions ESO – IN EXO – OUT Hyper – Up Hypo – Down Cyclo – Around. These words can be linked to tropias or phorias for example, I could describe an esophoria which would mean when the eyes are dissociated the eyes are moving in (convergent) Cover test This is a mainly objective test that is essential in ALL examinations. This examination is a requirement of ANY NHS or full screening examination and should be performed at multiple times during the eye test. This gives us a crucial measure of the binocular system at varying levels of refractive correction. Allows differential diagnosis between heterophoria and strabismus Cover test types 1. Cover /Uncover – (Think tropia test) 2. Alternating Cover Test 3. Prism Cover test 4. Subjective (Phi) test Cover test set up Lights on – typical lighting Cover test can be performed at different distances – specifically usually D+N. Cover tests can be performed in varying refractive states (with or without glasses) Test Vision or VA of each eye in turn at chosen distance. The target then needs to be one line above worst VA eye (full line read). For example right eye sees 6/7.5 left eye sees 6/6 the target should be on the 6/10 line. If VA of worst eye falls below or equal to 6/36 a spotlight should be used. Cover/Uncover test 1 2 3 4 1.Prepare the patient 2. Cover first eye (In 3. Hold cover for 2-3 4. Repeat on fellow as above – Chosen known strabismus seconds and remove. eye, always looking at refraction for test, cover the non- Repeat 2-3 times the uncovered eye. appropriate target strabismic eye first) – continuing to watch distance, appropriate Watch the uncovered the uncovered eye and target chosen eye as you do this. it’s movement. following VA/ Vision check. 1. In this case in A you can see that right eye is turning inward in natural gaze 2. You begin by covering left eye 3. Watch as the right eye MOVES OUT to take up fixation, when the other eye is covered. 4. When the cover on the left eye is then removed, the right eye then moves back in to take up its natural position. 5. When the right eye is covered the left eye (uncovered) remains straight because it doesn’t need to move to take up fixation. On cover removal the left eye still remains straight. What deviation is this? Right Eye Esotropia/Convergent strabismus Consider for tropias Constancy – Some tropias/strabismus may show intermittently – This can depend on distance, length of cover, refractive correction. Direction of deviation – Which way does the eye move (Can only be (Eso or Exo) AND (Hypo and Hyper). We can have an esotropia WITH a hypotropia but NOT an esotropia WITH an exotropia Eye preference –Consider for alternating which eye the patient prefers to fixate with. Which eye is typically fixating this will be the preferred eye. Degree of deviation – The size of the deviation, we will learn to measure this exactly but in general practice estimation is usually done. Cover/Uncover test We can use this test to look for heterophorias but more difficult to see movement. Repeat this test this time examining the COVERED eye for movement. Do not mix it will confuse you. 1 2 3 4 1.Prepare the patient 2. Cover first eye. Hold 3.Repeat 2-3 times 4. Repeat on fellow as above – Chosen cover for 2-3 seconds watching if there is any eye, always looking at refraction for test, and remove. movement in the eye the COVERED eye. appropriate target Watch the COVERED you are covering. distance, appropriate eye as you remove the target chosen cover following VA/ Vision check. In A these eyes appear straight on primary natural gaze. B -Cover right eye and under the cover it appears to move in. This is showing that when dissociated it prefers inward. C-When the cover is removed it returns to it’s typical position at straight During these movement the left eye remains straight. The left eye may show a small “corrective” pattern on repetition, as the right eye is uncovered and turns back out (for appropriate fixation) the left over corrects to match this movement and then both eyes return to straight positioning. The same movements would be shown when the cover was placed on the left eye What do we think this is? An Esophoria (Notice we don’t consider an eye with this because ESOPHORIA is a binocular movement  Direction of deviation – exophoria, esophoria, hypophoria, hyperphoria. CANNOT have a tropia and a phoria in the same direction. EG cannot have an exophoria AND and Esotropia Degree of deviation – The size of the Consider for deviation, we will learn to measure this exactly but in general practice estimation is usually phorias done. Compensation/Recovery - What was the speed and smoothness of the recovery motion  In general practice most people record phoria recovery simple as Recording smooth and fast or slow and hesitant. recovery of However there are some grading scales out there that you can utilise like this one included that can give you more understanding of what to phorias expect.  This should follow cover/uncover test and is a much more invasive technique that causes more dissociation to allow for total deviation to be measured. The set up is the same as for cover/uncover This test CANNOT always distinguish between Alternating phorias and tropias. cover test This time you transfer the cover from one eye to the other. The cover should be speedily transferred between eyes. Each eye should be covered from for between 3-5 seconds (or longer if deviation is latent) and then swift movement to the other eye. Repeated cover of each eye 3-5 times. 1. 1. To begin with the patient appears straight, then on adding of the cover the COVERED right eye moves outwards. 2. The right eye then moves outwards under the cover. 3. When moving the cover over the right eye then does its compensatory movement to the left, as the left eye returns to fixation. 2. 4. This is then corrected and both eyes fixate as cover is moving between – ideally you move the cover so quickly that fixation in between isn’t possible 5. 5. The left eye then moves outwards under the cover. 6. On movement to the next 3. eye we DO NOT see the compensatory movement showing that the right eye 6. is the dominant one. 7. The right eye moves out again when covered. 4. What is this? 7. Exophoria  1. Need eye affected Right/Left/Alternating (with preference) Correct 2. Need Direction Exo/Eso/Hypo/Hyper recording of 3. Need size 20Δ/10Δ 4. Need Test Distance (The size and deviation can change on different Tropia distances) Examples Distance Right SOT 20Δ Near Left HypoT 15Δ Distance Alternating XOT, right eye preference 25Δ  DO NOT SPECIFY EYE- binocular issue Need Test Distance (The size and deviation can change on different distances) Correct Need Direction Exo/Eso/Hypo/Hyper recording of Need size 20Δ/10Δ Need recovery – Good smooth recovery/ Slow hesitant – can use grades Phoria Examples NEAR SOP 10Δ good smooth recovery Distance Small hyperphoria approx 5Δ poor recovery Near XOP 10Δ 1 recovery Prism Cover test A prism cover test should be done following a cover/uncover and an alternating cover test and isn’t always a requirement. As time goes on in your career you will typically estimate these movements but exact measurements are still occasionally required AND to be able to accurately estimate you need to have done many prism cover tests. The process is the same as an alternating cover test however we need to incorporate corrective prism. Prism correction Exo – Base IN Eso – Base OUT Hypo – Base UP Hyper- Base DOWN This is what we use to test the amount of deviation that is present. Prism Cover Test 1 2 3 4 1.Prepare the patient 2 Complete a 3.Repeat Alternating 4. Repeat while Chosen refraction for cover/uncover and cover test using a SLOWLY increasing test, appropriate target alternating test without prism bar with correct the prism bar until the distance, appropriate any prism base on the deviated deviation stops or target chosen eye for tropia or either reverses. Note this following VA/ Vision eye for phoria. number and then bring check. the prism bar down in numbers before removing from patient.  This isn’t a test used often in In convergent (ESO) Subjective practice but is good to help deviations you will see an you understand as “Against” movement. The Phi Test practitioners when being target will appear to move in the opposite way to the tested on. cover. If you moved cover As a patient if you have a right to left the target would strabismus or a phoria you appear to move right. will notice a “Jump” when the cover is being In divergent (EXO) deviations transferred from one eye to you will see a with the other during alternating movement. The target will cover test move towards the movement of the cover. If you moved the cover right to left the target would move left. Cover test top tips -We can see movement even of just 2Δ -Ensure you are fully covering the eye to allow for dissociation. Take time to allow for dissociation ensure you are leaving the cover there for long enough When doing alternating switch quickly between eyes. Cover test quiz https://aao-resources- enformehosting.s3.amazonaws.c om/resources/ Pediatrics_Center/Strabismus- Simulator/index.html Amblyopia introduction Amblyopia is the impairment of vision arising from processing dysfunction. This can be caused by a number of things but is due to some level of retinal image degradation. This is a change that happens in the LGN and visual cortex though there are no visible changes to the eye when amblyopia is present. You may have heard this termed as a “lazy eye” however amblyopia although often unilateral has the potential to be bilateral. 2 Lines of VA difference usually to be considered “true” with associated image degradation. Amblyopia Causes 1. Strabismic amblyopia 2. Stimulus deprivation amblyopia 3. Anisometropic amblyopia 4. High ametropia amblyopia 5. Meridional astigmatic anisometropia amblyopia These are the main considered causes but essentially, we are looking for anything that could degrade the retinal image with the ‘critical period’. This will leave a long-lasting effect on the visual perception of the patient. Critical period The critical period is a period that we refer to in numerous areas of paediatrics. But within Optometry this is the time often stated as the time we consider the plasticity of the visual system to be high enough that large changes to the cortical processing can be made. There are many debates on when the “true” critical period is and lots of the research available has been done on nonhuman subjects due to the nature of the testing. However, a rough guideline you’ll often hear is 8 years of age as a top end. The plasticity of the visual system is at it’s greatest in young ages and is suggested to lose its malleability at around 8 years of age. However, some studies show good levels of plasticity greater than this age range but definitely changes are harder and less likely to be successful after this point. Critical periods In reality different aspects of the visual system mature at different ages, something you’ll discuss in lectures later in this module. So there are some areas of visual adaptation that are possible for longer and some that have less malleability. When considering critical periods we need to consider; visual maturation, the pathways resistance to abnormal visual input, the form of amblyopia we are treating and the treatment option we use.  Very prevalent affects around 2-5% of the population. 1. Strabismic amblyopia Unilateral amblyopia Constant deviation will lead to this, any intermittent deviation much less likely Most common in esotropia (as less likely to be alternating or intermittent) Amblyopia 2. Stimulus deprivation Can be monocular or binocular Usually linked to pathology of some kind, most common is congenital cataracts Rarest form in places like UK with screening examinations readily available. However things like nystagmus with less easy fixes may not be able to be rectified. Or conditions easier to miss (macular damage) or reoccurring problems (ptosis).  3. Anisometropic amblyopia Monocular The eye with the highest prescription is typically the lazy eye Can be spherical or astigmatic differences Most common in hyperopic prescriptions as they may accommodate for the eye with the lesser prescription but not enough for the other eye. Has the potential to be changed for the longest period of time. Critical period appears to be greatest here. Amblyopia 4. Ametropic amblyopia Bilateral Typically, more than +6 if hyperopic, myopic less can be significant given the age. Very difficult to treat 5. Meridional amblyopia Monocular if linked to anisometropia amblyopia Binocularly if linked to ametropic amblyopia Blurring along one axis and clear along the other even with appropriate correction in place. Conclusions Enhanced understanding of ocular alignment Ability to quantify cover test results Analysis of expected results related to ocular alignment issues Insight into prism measurement for tropias and phorias Amblyopia introduction.  3. Binocular Vision Accommodation and Convergence Emma Percy Learning Intentions 6615 To reintroduce the concept of the near triad Understand the mechanism of accommodation and the different ways to measure it To understand convergence and the varying tests to measure. To be able to understand the complex relationship between accommodation and convergence. To have an awareness of the conditions that are caused when accommodation and convergence aren’t optimal.  The Near Triad Miosis – Constriction of the pupil Accommodation – Focusing using change in crystalline lens shape Convergence – inward movement of the eyes. Purpose of near triad To allow for a binocular near focussed image Miosis- To avoid excess light and stimulation Convergence – To allow images to be matched and equal between eyes Accommodation – To allow depth of focus allow for near sustained tasks. All controlled by Cranial Nerve 3 –Oculomotor nerve What are some tests you already know that you use to test the near triad? Accommodation definition The curvature and thickness of the crystalline lens changes due to constriction of the ciliary muscle (innervated by the 3rd nerve). Accommodation is present from birth but typically very inaccurate in first few months This occurs due to a range of stimuli and is limited by numerous factors including; The near and far point of accommodation. The ability of the eyes to recognise a blurred image The innervation strength of the 3rd nerve The curvature of the lens. The flexibility of the lens. Types of accommodation 1. Tonic accommodation– This is the resting state of accommodation i.e. no stimulus, this is between 0-2D 2. Reflex accommodation – This is the automatic response of accommodation initiated to maintain a clear retinal image. The stimulus is just small amounts of retinal blur (5 usually 3D aniso Correct spherical component according to age + consider reduced Rx for aniso (e.g. 1D less than full difference) 1-3.5 y/o, 1-3D aniso Monitor 4-6/12, if aniso persists Rx as per (1) Aniso 3.5+y/o: May be amblyogenic at this age, Rx as per (1). If no amblyopia, begin monitoring a. >1D hypermetropic b. >2D myopic c. >1.5DC Refractive error Flitcroft. 2014 Hypermetropia remains from birth or develops in childhood resulting from a failure of emmetropisation. Myopia develops later from emmetropia so is no considered failed emmetropisation (Near work / low outdoor time) Astigmatism appears to be failed emmetropisation but the mechanism for which is not certain. Myopia The prevalence is increasing over time (McCullough et al. 2016) Advise parents emmetropia can progress to myopia. Encourage: - Time outdoors. - Time away from screens. - Regular eye examination. Myopia Logan et al. 2011 Examined refractive error of school aged children in Birmingham. (Asian and Black children were 2nd or 3rd generation British. - Incidence of myopia highest in South Asians, lowest in White Europeans - Hypermetropia highest in White Europeans, lowest in Afro-Caribbeans Myopia French et al. 2012 Compared refractive error between European Caucasian children in Northern Ireland and Sydney Australia. Refractive error in special needs. Typically, between 5-10% school age children in the UK require refractive correction. Comparatively, correction is required in 60% of Individuals with Down’s syndrome. (Woodhouse et al. 1997) Refractive error in special needs. Individuals with visual impairment are more likely to have refractive error. (Du et al. 2005) Abnormal development and strabismus There are strong associations between Hypermetropia and esotropia in childhood The likelihood of an SOT increases with increasing hypermetropia. Amblyopia Most common cause of monocular vision loss in children and young adults (1 – 3.5%) in the developed world. Defined as: ‘Diminished visual acuity in one or both eyes despite correction of refractive error and the removal of pathological obstacles’ Amblyopia. Results from abnormal stimulation of the brain during the critical period of visual development Causes are from one/combination of: 1. Light deprivation 2. Form deprivation 3. Abnormal binocular interaction Amblyopia – Light deprivation Full absence of stimulation to the retina, as in no light reaches retina. Very uncommon even in the presence of dense cataract. Ptosis? Cause of deep amblyopia. Amblyopia – Form deprivation Some light is able to reach the retina but remains defocused. Media opacity – congenital cataract, corneal opacity Uncorrected refractive error Amblyopia – Abnormal binocular interaction Incompatible images formed on each fundus resulting in formation of 2 separate images An example of this could result from strabismus. Amblyopia – Broken down further… Stimulus deprivation – (light and form deprivation) Lack of adequate visual stimulation in early development to either/both eyes. No/limited light can enter the eye due to ptosis or media opacities. Amblyopia – Broken down further… Strabismic amblyopia Constant unilateral strabismus with onset in childhood. Latent/intermittent deviations may break down SO>XO. Individuals with should be monitored more frequently in childhood. Those with alternating strabismus are at lower risk. Amblyopia – Broken down further… Ametropic amblyopia Bilateral refractive error, spherical or astigmatic, in each eye may lead to blurred vision at all distances E.g. very high myopia Amblyopia – Broken down further… Meridional amblyopia Uncorrected astigmatism I one/both eyes give clearer vision in the least ametropic meridian. A blurred image received in the more ametropic meridian. Amblyopia – Broken down further… Anisometropic amblyopia Significant difference in refractive error between the 2 eyes. One eye has a visual advantage. E.g. 1 eye must accommodate less to produce a clear retinal image. As such, V1 only receives the ‘best’ input and preferentially develops to favour the image from the better eye. Amblyopia – Broken down further… Idiopathic amblyopia No obvious cause known Critical period Neural plasticity is a state where the links between the neurons in the brain can change and reform. The critical period is the time frame in which we have neural plasticity, and the brain can adapt and reform as a response to changing input. Within this time the development of the visual cortex is vulnerable to abnormal development due to atypical input. Amblyopia risk, critical period – Epelbaum et al. 0-4/12 there appears to be no risk of amblyopia The most improvement to strabismic amblyopia is made if corrected in the 1st 3 years. Vision may still improve but to a reduced extent right up until 12 years old. Amblyopia risk, critical period Previous studies have suggested anisometropic amblyopia could be successfully treated right up until 8 years old. More modern research suggests treatment may still yield positive results even beyond this period. Amblyopia – animal studies Mainly performed on monkeys and kittens animal studies were useful analogues to develop an understanding on cortical development and amblyopia. Amblyopia was induced by way of: - Lid suturing - Induced unilateral strabismus - High powered convex lenses - Restricting visual stimulus to stripes with only one orientation Amblyopia – animal studies Unsurprisingly given what we’ve learnt so far, the more significant the deprivation the more severe the resulting amblyopia Visual deprivation syndrome Crawford used this expression to describe unilateral amblyopia in 1978. Comprising of: - Decreased VA in deprived eye - Loss of binocular summation and by extension, stereopsis - Reduced cortical neurones receiving input from deprived eye and reduced binocularly driven cells - Decreased cell size in relevant layers of the LGN Reversing amblyopia Blakemore showed effects of deprivation could be reversed (removing suturing from animal’s lids) if done within the critical period. After the reversed suturing LGN cells for affected eye regained their size. Post-mortem humans Van Noorden found shrinkage in the layers of LGN dedicated to the amblyopic eye during post-mortem examination of individuals with known amblyopia. These findings are consistent with those changes in seen in the visual system of the animal studies. Treating amblyopia Before beginning tx we must ensure no pathological cause exists and we have corrected significant refractive error. In many cases refractive correction is enough to treat amblyopia. (Moseley et al. ‘02) In those instances where it’s not we can use: - Occlusion - Cyclopegia - Optical penalisation Treating amblyopia - Occlusion Total occlusion - removal of light and form by way of occlusion (sticky patch) of the better eye. Total occlusion, excluding form - frosting a lens to allow light but no form resolution. Partial occlusion – some form but reduced VA (bangerter form/sectoral occlusion eg inferior portion of the lens) Treating amblyopia - Occlusion Total occlusion - removal of light and form by way of occlusion (sticky patch) of the better eye. Total occlusion, excluding form - frosting a lens to allow light but no form resolution. Partial occlusion – some form but reduced VA (bangerter form/sectoral occlusion eg inferior portion of the lens) Treating amblyopia - Cycloplegia Blurring of the better eye by use of cycloplegic agents, usually atropine. Can either be done on alternate days or weekends Atropine has potential for systemic side effects – must occlude puncta to prevent leakage. Treating amblyopia – Optical penalisation Refractive blur induced by way of lens power to the better eye. Optical penalisation can be tuned to effect distance vision, near or both. Can also be used in conjunction with cycloplegia. Treating amblyopia – Choosing a treatment Age of child – younger = more rapid response to treatment (can still improve older children) General health – consider systemic condition, E.G. deaf? Rely on lip reading. Eczema/allergies? Social factors – Attendance to hospital. Appearance of glasses/patching Compliance – will a child understand why/comply? will the parent/teacher enforce etc? Nystagmus – latent component to their nystagmus may become manifest if better eye occluded. Considerations when treating PEDIG reviewed experimental trials and proposed the following points: Treatment for both strabismic and anisometropic amblyopia is successful – around 75% of children under seven years of age achieved resolution of amblyopia with either patching or atropine Best optical correction is essential to successful treatment Patching and atropine are equally effective for treating moderate amblyopia If one treatment modality fails, an alternative method can be initiated Younger age is associated with better final acuity, but treatment should be attempted in older children VA needs to be monitored closely on cessation of treatment to identify any regression Amblyopia treatment has a significant social and physical impact on the child and the family. Initial correction Provide spectacles for constant wear, fully correcting any anisometropia (where strabismus is present or suspected fully correct hyperopia as well). Refer strabismic patients who retain a manifest strabismus following full correction of their refractive error for orthoptic assessment and management. Monitor monocular visual acuity using a robust test at two monthly intervals. Refer for Orthoptic assessment when… Interocular acuity difference is greater than 0.5 LogMAR after two months of spectacle wear. Visual acuity fails to improve by 0.1 LogMAR or more on consecutive visits. Amblyopia persists beyond 16-22 weeks of spectacle wear. N.B. Know the referral pathways and waiting times for your local orthoptic department to factor this into any management plan. Paediatric examination Overview Testing protocol for children follows similar patterns to that of an adult examination (H&S, OMB, Refraction, Health…) we some important adaptations Type of test used The manner we present the test The manner we present ourselves VA development with age At birth, a child’s VA is around 2.0 LogMAR (6/600) which improves rapidly and reaches adult levels by age 6. Visual acuity Ideal test - Same no of letters each line - Same space b/w and lines (relative to letter size) - Change size between lines in log steps - At any distance - Repeatable - Known inter ocular diff - Published norms Visual acuity Picture of bailey lovie Is it appropriate for kids? Boring Frustrating Visual acuity – optotypes - Tumbling E - Broken wheel - Kay pictures - Leas symbols - Letters Visual acuity – child appropriate Naming/matching letters – Sonksen/Keeler - Crowded letters - Logarithmic progression between lines - Published normative data - Calibrated for 3m Visual acuity – Sonksen Sonksen Wade Proffitt et al, 2008. Appropriate to test 2yr9m to 7 yr 9mo. Chart presented 1 line at a time, crowded and comes with matching chart. Crowded letters LogMAR Keeler Sonksen Visual acuity – child appropriate Naming/matching pictures – Kay pictures/Lea symbols - Crowded pictures - Logarithmic progression in size - Also available uncrowded (Becker Hubsch Graff, 2002) Lea Symbols also give a very precise end point as once you get beyond an individual's end point, all the symbols begin to look very similar Crowded pictures LogMAR Lea symbols Kay pictures Measuring VA with recognition tests Explain what you are going to do – establish if able to name/match. Start up close to check their understanding. Once established move to 3m. Progress through the chart. Try and end on a good note. Preferential looking tests – CAT/Teller Teller cards comprise of grey card with 1 blank side and 1 side with a grating. (