Lexicon of Conditions

December 3, 2020 3:54 pm

Lexicon of Conditions

Research participants can have a variety of (temporary) accessibility needs for various reasons. This could range from people with disabilities, developmental disorders and other kinds of conditions.   

In this lexicon we give an overview of research participants living with conditions that are commonly recruited or not often recruited for in research within the health sector, financial services, and retail.  


According to WHO, over 1 billion people live with some form of disability and the forecast is that this amount will have doubled by 2050. In the UK there are 13.9 million people living with a disability, which can cost them upward of nearly £600 extra and can make them twice as likely to be out of a job. According to the Office of National Statistics, the definition of disability is when a person self-reports on long-standing illness or condition that significantly affects their day-to-day life. 

Vision loss 

Around 2 million people in the UK have vision loss but of this number only 360,000 are registered as blind or partially sighted. People who get a diagnosis of complete or partial vision loss may go through similar phases as those who are grieving due to the loss of a loved one by death. 

There are several types of vision loss and eye conditions (including, but not limited to):   


This is a common condition in which someone struggles to focus their eyes because the cornea or lens of the eye is not in a perfectly rounded shape. This issue can be corrected with glasses and lenses, but not in particular instances where the cornea is curved differently across areas or directions – also known as irregular astigmatism.  

Monocular vision 

We speak of monocular vision when someone only has vision in one eye, partially losing their field of view and experiencing problems with depth perception. Consequently, this affects the ability to accurately judge one’s distance from and the width of objects. Over time this is compensated for by the remaining eye to a certain extent. 

Posterior capsule opacification 

A complication that can occur after cataract surgery is called posterior capsule opacification (PCO). This condition can make your vision cloudy.  About 10 per cent of people that have had cataract surgery will develop PCO.  

Hearing Conditions  

Deafness is described by WHO as the complete loss of the ability to perceive sound from one or both ears. This is also known as a profound hearing loss.  

Just like with blindness, there are different variations and kinds of ways to describe deafness and different types of hearing loss.


Deafened is used to describe people whose hearing was complete upon birth, but have lost most or all of their hearing later in life.

Hard of hearing

This term is used to describe people who have lost some but not all of their hearing.

deaf (lower case ‘d’)

When using the term deaf with lowercase ‘d’, it refers to people who were born with hearing loss or gain hearing loss, but mix in well with people in the hearing world. People who are deaf may communicate verbally as well as through sign language. As such deaf people may not identify with the deaf community. 

Deaf (upper case ‘D’)

People who identify as Deaf usually consider themselves members of the Deaf community and for the most part only use sign language to communicate. 

Hearing impaired

Please note this term is outdated and not preferred as it suggests people with hearing loss are defined by their disability. 
This term was previously used to describe someone with hearing loss of any level. 

Acquired hearing loss

This term refers to people have lost their hearing partially or completely after birth. 

Congenital hearing loss

Congenital hearing loss refers to people who were born with hearing loss. 


This is a condition used to describe the presence of a sound in someone’s ear with the absence of an external source of sound. While most people may think this condition results from (prolonged) exposure to loud volumes of sound, there are many different causes of tinnitus known. 

Motor disabilities 

Any condition that interferes with sensation, coordination or movement, is referred to as a motor disability. A motor disability can be caused by a variety of causes. For example, the cause can be congenital (from birth), due to physical trauma (e.g. car accidents) or illnesses. 

Cerebral Palsy 

A brain injury or abnormality resulting in the loss of muscle control. This condition usually presents itself during pregnancy or early infancy. Problems with the muscles, speech, involuntary movements and spasms are associated with cerebral palsy. 

Muscular dystrophy 

This is a group of muscle diseases that cause skeletal muscles to weaken and break down over time.  

Multiple sclerosis

Multiple sclerosis is a disease of the brain and spinal cord which can cause disability.  

Spina bifida

This condition refers to when the spine and the spinal cord are not properly formed at birth. 

ALS (Amyotrophic lateral sclerosis) / Lou Gehrig’s disease 

ALS is otherwise also known as a motor neurone disease. This disease causes the death of neurons which control voluntary muscles.  


Arthritis is a musculoskeletal condition that affects the muscles, bones and joints. The often presents itself as the swelling and tenderness of one or more joints in the body.  

Parkinson’s disease 

This condition is a brain disorder which leads to involuntary shaking, stiffness, and difficulty with walking, balance, and coordination. It is also called a degenerative and progressive disorder as this disease usually begins gradually and gets worse over time. 

Essential tremor

Essential tremor is a disorder of the nervous system that causes involuntary and rhythmic shaking. This is a condition that can affect any part of the body but usually occurs in the hands when executing daily tasks like drinking or tying shoelaces.  


Neurodiversity has come to mean “a variation in neurocognitive functioning“. It is a term coined in 1998 by Judith Singer, a sociologist with autism. Neurodiversity could also otherwise be explained as a concept where neurological differences are to be recognised and respected as any other human variation. Advocates of neurodiversity are opposed to viewing neurodivergent as a disorder or mental illness. 


When someone is described as neurodivergent, one typically means someone who is not neurologically typical. 


Neurotypical is the opposite of neurodivergent and refers to someone being neurologically typical. 

Specific Learning Difficulties 

People with a specific learning difficulty (SpLD) are said to be neurodivergent according to neurodiversity advocates. In the medical world SpLDs are classed as a type of neurodevelopmental disorder. Specific learning difficulties are not linked to intelligence but can make learning difficult for individuals. Individuals may also have a specific learning difficulty to varying degrees.


Note: While autism on its own is not a specific learning difficulty, significantly more people with autism have a learning disability than do people without autism – at a ratio of 40:1.

Aside from autism being a spectrum of developmental conditions, autism can affect people’s ability to learn which makes it challenging for to adjust to (educational) systems that are not catered to their varying and complex needs.  


Dyslexia is a specific learning difficulty that affects the way information is being learned and processed. Literacy skills, such as writing, reading, and spelling are therefore negatively impacted by dyslexia.  


Dyscalculia affects the ability to do mathematics.


Dyspraxia refers to a condition where one’s organisation of movement is restricted.


Dysgraphia describes a deficiency in the ability to write, primarily in handwriting, but also coherence.  


Attention deficit hyperactivity disorder (ADHD) is a condition that affects how people pay attention. A person with ADHD can seem inattentive and restless, amongst other things.


ADD is officially described in the DSM-IV as “ADHD of the predominantly inattentive type”, however ADD is more appropriate to use. 
ADD, an acronym for Attention Deficit Disorder is a term to describe people who struggle with concentration, but do not have symptoms such as being hyperactive or excessively impulsive like children tend to have. 

Other neurodivergent conditions  


Obsessive compulsive disorder (OCD) is a mental disorder in which a person feels the need to perform tasks/routines repeatedly or has certain thoughts repeatedly to the point of obsession


Synesthesia is a neurological condition in which information meant to stimulate one of your senses, stimulates several of your senses. As a result, the normal separation between senses is broken down. 

Brain Injury: Acquired Brain Injury & Traumatic Brain Injury

In essence, acquired brain injury (ABI) is an injury acquired after birth and is associated with pressure on the brain.  Traumatic brain injury (TBI) refers to when an external force causes the brain to move or damages the skull, because of which damage occurs. In both cases this can lead to a short attention span and difficulty processing information. 

Meares-Irlen Syndrome

This syndrome is a kind of visual stress or a perceptual processing disorder, which mains that the brain is unable to process visual information in a normal way


Hyperlexia is defined as exceptional reading ability at an early age without age-appropriate language and speech skills. According to experts this condition occurs in people on the Autism spectrum.

Tourette Syndrome

Tourette Syndrome (pronounced too-ret) is a common neurodevelopmental disorder that begins in childhood or adolescence and is characterized by chronic vocal and motor tics.  

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