Dyslexia is not a disease, it is a condition that you are born with. It is a difference in the way the brain works; a difference that will be present throughout your life. Dyslexia mainly affects reading and language skills and the effects can range from mild to very severe. It is a type of ‘Specific Learning Difficulty’. The sooner dyslexia is spotted, the sooner suitable learning and coping strategies can be employed to minimise the effects of the condition.
It is easy to think that dyslexia is primarily a vision problem but it is not. Certain visual problems can be more common in dyslexia but dyslexia can also be present without any visual problems. A dyslexia diagnosis is made by either an educational psychologist or a qualified specialist dyslexia teacher – NOT by an eye care specialist.
Our role as eye care specialists, is to identify and treat any visual problem that may be associated with the dyslexia. It has been suggested that there are higher levels of binocular vision problems and visual stress in people with dyslexia that contribute to their reading difficulties.
Symptoms of both binocular vision problems and visual stress can often overlap. Some examples of symptoms include:
There are many types of binocular problems that can be caused by ocular misalignment or strabismus, ocular motility anomalies, convergence and accommodation deficits. These problems are identified in an orthoptic assessment and can be treated with exercises or with manipulation of the glasses or contact lens prescription.
Pages of print can resemble a visually stressful pattern, print can appear very stripy and can be uncomfortable to look at. This discomfort is defined as visual stress. It is thought that this visual stress is caused by a hyper excitability of neurones in the visual cortex. This means that some of the cells in the part of the brain that deals with processing of visual information work too fast or are over excited and therefore do not respond in the way they should to process information in a normal fashion.
Visual stress is also known as Meares-Irlen syndrome, Irlen syndrome, and Scotopic Sensitivity Syndrome.
Coloured spectacle lenses have been shown in some cases to benefit those with visual stress, headaches, migraines and photosensitive epilepsy. We know that certain cells in the visual cortex are sensitive to specific colour wavelengths, so by placing a colour filter in front of the eyes, the pattern of excitation can be changed. In other words, the colour will help to slow and calm these cells, therefore quietening the pattern and reducing the visual stress. The colour needed to reduce the hyper-excitability is very precise and individual to each person.
In addition, research in the US undertaken recently by a team of neuroscientists, using brain imaging, has shown that those who suffered from migraines had a vast improvement when individually selected precision tinted lenses were worn. Symptoms of other neurological conditions such as Autism, MS, ME and Parkinsons have been shown to reduce with the application of a precise colour.
Visual Stress can be reduced by the use of coloured filters. This works by placing a coloured overlay directly over text, or by wearing coloured lenses in spectacles. The reduction occurs only when the colour is selected to suit the individual.
In order to determine the precise colour tint for glasses to improve symptoms of visual stress, we use the Intuitive Colorimeter. The Intuitive Colorimeter is a machine that allows us to apply different colours upon text whilst adjusting the hue and saturation level until a specific colour is identified that will provide comfort when looking at text.
For those who have debilitating visual stress and require tint correction throughout the day, we can provide Cerium contact lenses. These are soft lenses where the centre is tinted with the specific colour as determined by Colorimetry and can correct your prescription at the same time.
The term vision tracking or eye tracking is used mainly by the education sector to loosely describe the vision assessments that can lead to reading difficulties, i.e binocular vision problems and visual stress. It is not actually a term that is commonly used in the eye care setting.
Strictly speaking, vision tracking is a technique used to assess the various eye movements (such as saccades and smooth pursuit). True problems with eye movements are rare and tend to be neurological in nature. Nevertheless, some practitioners will use software to record eye movements during reading. Whilst this can highlight issues in reading fluency, we do not see enough clinical benefit of performing this task.
Reassured, our combined binocular vision and visual stress assessments will cover the assessment requirements for ‘vision tracking’.
After the initial pre-screening tests such as imaging of the retina, you will firstly have an Orthoptic assessment. This will look at the control of the eyes as a pair, looking at the strength of binocular single vision, including convergence and oculomotor function (eye movements and co-ordination). These assessments are carried out by a highly experienced (HCPC registered) Orthoptist.
Following this, you will be seen by the Optometrist who will perform a refraction to measure the refractive error. They will then combine the results from the orthoptic assessment to check for focussing issues. Further tests will look at other causes of visual discomfort and Visual Stress. They will decide if an overlay assessment or colorimetry is required. Our Optometrist is experienced in Visual Stress assessment and has previously provided ‘specific learning difficulties’ assessment.
Whilst we specialise in identifying and treating visual problems that may be associated with Specific learning difficulties such as Dyslexia, we are clear to state that we are not treating dyslexia or claim to treat learning disabilities, ADHD, and autism.
Behavioural Optometry (BO) is a sub-discipline of optometry that originated in the United States. In the United Kingdom, a small number of optometrists have taken additional courses provided by the British Association of Behavioural Optometrists to be ‘Behavioural Optometrists’. Behavioural optometry is not endorsed by most optometrist, ophthalmology and paediatric associations.
The following do not endorse vision therapy for learning or developmental issues: American Academy of Pediatrics (AAP), American Academy of Ophthalmology (AAO), American Association for Pediatric Ophthalmology and Strabismus (AAPOS), American Psychological Association (APA), Royal College of Ophthalmologists (RCOphth), Royal College of Paediatrics and Child Health (RCPCH), College of Optometry in UK.
“Vision problems are not the cause of primary dyslexia or learning disabilities and should not be treated as such.” (AAP Policy Statement, 2009)
Behavioural optometry claims to adopt a holistic approach to vision care—considering the individual and their environment—which aligns with general principles of good clinical practice. However, some of BO encompasses a wide range of diagnostic and therapeutic approaches, some of which diverge significantly from conventional optometric practice. Many BO practitioners prescribe a course of ‘vision therapy’ sessions and spectacles with prism incorporation which are not endorsed by regular Orthoptic, Optometric and Ophthalmic practice and certainly not considered as a treatment option on the NHS in England. Some may even prescribe exercises to address the physical symptoms of dysgraphia which is regarded to be outside of the remit of Optometry and requires specialist input from an Occupational Therapist.
“There is little support in the literature for vision therapy to improve reading ability in children without an identified binocular vision anomaly.” Rowe, F. J. (2017). “Vision therapy and children’s reading: A review.” Clinical and Experimental Optometry, 100(6), 506–517.
At our clinic we take a collaborative approach to visual stress. Our process involves both a detailed Orthoptic evaluation followed by a comprehensive Optometric assessment.
Ruling out binocular anomalies: Many symptoms attributed to visual stress can be caused by binocular vision problems such as poorly controlled heterophorias or convergence problems.
Ruling out refractive errors: Certain refractive errors will affect how we accommodate and so it is important to use objective techniques that obtain an accurate refractive status. Cycloplegic drops may be needed for children to improve accuracy.
We do not prescribe ‘Vision Therapy’ courses. Certain binocular problems can be successfully improved with specifically tailored Orthoptic exercises. A course of Orthoptic exercises will be recommended to do at home after it is demonstrated in clinic. We do not require patients to attend for ‘vision therapy’ sessions.
Connan Tam BSc(Hons)Orthoptic MCOptom DipTp(IP)
Connan is director at Burnett Hodd & Tam Optometry. He has dual qualification in Orthoptics and Optometry.
Shabnam Khan BSc(Hons)Orthoptics
Shabnam is the Head Orthoptist of the Eye unit of Chelsea and Westminster Hospital responsible for delivering the National School Vision Screening Service for Hounslow & Richmond Community Healthcare NHS Trust
Mrs Khan is a highly specialised Orthoptist with almost 20 years experience working in the hospital eye service, private sector and community healthcare.
She is the Head Orthoptist of the Eye unit of Chelsea and Westminster Hospital. She has been involved in research, medical education and specialised in Paediatric care. She has also delivered and continues to maintain the National School Vision Screening Service for Hounslow & Richmond Community Healthcare NHS Trust.
She gained her Orthoptic degree with Honours from The University of Liverpool. Her previous employment includes Great Ormond Street Hospital for Children.
Outside of healthcare, Mrs Khan is dedicated in community work. In 2010, she was awarded the Youth Achievement Award: Celebrating Future Leaders, hosted by the Universal Peace Federation & the Women’s Federation for World Peace at the House of Lords. In 2013, she was nominated and selected for the Queen’s Garden Party for continued community services.
Tejinder Kahlon BSc(Hons) MSc MCOptom DipTp(IP)
Tejinder has over 22 years of experience working as an Optometrist and works as a specialist Optometrist at Moorfields Eye Hospital and at the Institute of Optometry. She was one of the key Optometrists carrying out full visual assessment, including the effect of colour overlay and colorimetry assessments as part of the Specific Learning Difficulty Clinic.
Tejinder graduated with First Class Honours in Optometry from City University in 2001, where she was awarded prestigious honours for Best Clinical Paper and Abnormal Ocular Conditions.
Her pre-registration year provided a broad range of experience, with placements in independent practices, as well as at St George’s Hospital, Central Middlesex Hospital, and the Institute of Optometry. In 2006, Tejinder earned a distinction in her Master’s in Clinical Optometry from City University.
Her dedication to global eye care led her to volunteer with Vision Aid Overseas in remote regions of Ethiopia and Zambia, where she trained nurses in refraction techniques and provided essential eye care to underserved communities. She also worked as the sole optometrist in the Falkland Islands, further expanding her experience in remote areas.
Tejinder has gained valuable experience in the Diabetic Ophthalmology Clinic at Central Middlesex Hospital and, for over 18 years, has worked alongside leading consultant ophthalmologists at Moorfields Eye Hospital, focusing on pre- and post-surgical refraction.
In addition, Tejinder has been part of a Specialist Clinic at the Institute of Optometry for 23 years, bringing a wealth of knowledge and expertise in managing complex eye conditions. She holds WOPEC certifications in Cataract and Minor Eye Conditions.
In 2024, Tejinder completed her Independent Prescribing qualification.
