Eye Conditions ( O to Z )

Our list of eye conditions continues here. Look Up makes every effort to ensure the information we provide is correct - however we are not a medical website. We have provided links to other organisations should you need more detailed information about eye health and disease.

Optic atrophy and conditions affecting the optic nerve
The optic nerve carries the nerve fibres from the back of the eye through to the visual cortex of the brain. Conditions that affect the optic nerve from functioning occur when there is damage to the nerve fibres that make up the optic nerve, or when the nerve fibres are diseased, degenerate or waste away.

There are a numbers of reasons why a person may have damage to their optic nerve. It can develop as a result of the optic nerve not developing properly or it may occur as result of injury at birth or as a result of being born prematurely.
Sometimes the optic nerve can be damaged as result of pressure within the eye (such as is caused by Glaucoma) or because of a brain tumour that puts pressure on the optic nerve. It may be an inherited disorder or it may have no known cause.

You may come across the following names for describing the conditions that affect the functioning of the optic nerve:

Optic Atrophy – wasting or degeneration of the optic nerve
Optic Nerve Hypoplasia – underdevelopment of the optic nerve
Optic nerve neuritis – inflammation of the optic nerve
Septo-optic dysplasia – underdevelopment of the optic nerve with additional abnormalities in the brain
Optic neuropathy – any term used to describe any damage to the optic nerve
Leber’s hereditary optic neuropathy – a congenital condition affecting the optic nerve that affect mainly men.
Papilloedema – swelling of the optic nerve where it leaves the eye – associated with an increase of pressure within the brain.

How someone’s sight is affected by optic nerve damage depends in the severity of damage and the type of damage. Optic nerve damage may lead to people having variable vision throughout the day and people may also have areas of their vision where they have no sight at all (visual field losses).

Optic nerve damage may occur in people with learning disabilities or cerebral palsy, and may also occur as part of syndromes such as Lawrence-Moon-Bardet-Biedl Syndrome. To find out more about this syndrome click here

For people with communication difficulties it may be very difficult for them to tell you how they see their world. It requires skilled observation and good knowledge of the person to begin to understand how a person might be seeing their world. A functional vision assessment is an important method of assessing someone’s vision.

For more information about Optic nerve damage click here to visit the Scottish Sensory Centre website


Retinitis Pigmentosa
Retinitis pigmentosa describes a range of conditions that affects the retina. The retina is made of up cone and rod cells. Rod cells are responsible for responding to movement, seeing in low light or darkness, and black and white vision. Cone cells are largely responsible for seeing stationary objects in fine detail and colour. The macular of the retina provides our central vision and is largely compromised of cone cells. The area of the retina around the macular provides is mainly comprised of rod cells.

Our central vision therefore allows us to see colour and detail whilst our peripheral vision helps us see movement and to see in darkness or low light.

Retinitis pigmentosa occurs when the retina becomes diseased. The condition very commonly starts by affecting the peripheral retina meaning that the peripheral or side vision is usually affected. Because this part of the retina contains the rod cells which allows us to see in the dark night-vision is often affected. ‘Night-blindness’ is often one of the early signs of this condition. The disease can be progressive and can lead to a person seeing only centrally (tunnel vision). Later in the disease the cone cells can be affected leading to an eventual total loss of sight.

Retinitis pigmentosa can run in families and there are well documented genetic causes for many types of retinitis pigmentosa. In some cases there is no family history and the disease is thought to be caused by a new mutation (change in a gene). There is currently no cure although with appropriate support and the use of various low vision aids and other devices people with the condition are able to make effective use of their vision.

For more information on Retinitis Pigmentosa click here

Retinitis pigmentosa is sometimes associated with Ushers Syndrome. Ushers syndrome affects up to 6% of those born deaf or partially hearing. The disease usually becomes noticeable in  late teens.  For more information about Ushers Syndrome click here 

For people with communication difficulties it may be very hard for them to tell you how they see their world. It requires skilled observation and good knowledge of the person to begin to understand how a person might be seeing their world. A functional vision assessment is an important method of assessing someone’s vision.


Retinopathy of prematurity
Retinopathy of prematurity (ROP) occurs in children who are born prematurely. A baby born full term will be born with an eye that has developed steadily and healthily. Blood vessels on the retina grow throughout the 40 weeks of a normal pregnancy, those in the peripheral retina developing last. In premature babies because they need help with breathing they are often placed in incubators with high oxygen concentrations. This is necessary as their lungs do not absorb enough oxygen from normal air to allow them to thrive and develop. Unfortunately this high oxygen concentration can also affect the developing blood vessels in the immature retina and cause them to grow in the wrong place or to form scar tissue. This in turn may cause stretching or traction on the developing retina, cause retinal detachments, or even cause a mass of abnormal tissue to form in the eye (retrolental-fibroplasia) preventing normal vision or causing blindness.

These days in well run neo-natal units premature babies are screened and treated for ROP reducing the impact on visual development. In very premature babies or those with complex support needs the balance of oxygen needed to support life and the concentrations causing ROP can be difficult to manage so some problems may still occur. Historically this was a much greater problem and there are many individuals with ROP alive now due to these issues.

The impact upon the individual’s sight depends on where this damage takes place within the eye. If the damage is to the central retina the impact will be more severe than if the damage has occurred to the periphery of the retina.

People with ROP may also have other secondary eye problems, such as microphthalmia, nystagmus, high myopia and strabismus.
Due to the effects on normal development of the brain caused by the complications of premature birth people born with ROP may also have accompanying learning disabilities or physical disabilities such as cerebral palsy.

For people with communication difficulties it may be very hard for them to tell you how they see their world. It requires skilled observation and good knowledge of the person to begin to understand how a person might be seeing their world. A functional vision assessment is an important method of assessing someone’s vision.

For more information on Retinopathy of Prematurity visit the RNIB website here.


Rubella Syndrome
Congenital rubella syndrome (CRS) a very rare condition caused when women contract rubella when pregnant. The condition affects the development of the unborn baby, and depending on the time during the pregnancy when the infection occurs the risks to the unborn child vary. If rubella is caught within the first three months of the pregnancy, it can cause damage in 90% of unborn babies, including:

•eye problems, such as cataracts (cloudy patches on the lens of the eye) and abnormalities in the retina.
•deafness
•heart abnormalities
•brain damage

The MMR vaccine has led to CRS very rarely occurring now although due to concerns a number of years ago into the effects of the MMR vaccine, and consequent reduction in numbers of girls immunised, there has been a recent rise in numbers of children being born with this condition.

For people with communication difficulties it may be very difficult for them to tell you how they see their world. It requires skilled observation and good knowledge of the person to begin to understand how a person might be seeing their world. A functional vision assessment is an important method of assessing someone’s vision.

For more information about Rubella Syndrome visit the SENSE website here.

Strabismus
Strabismus is sometimes referred to as a squint. For us to use both our eyes together our eyes need to move in unison. In strabismus one or both eyes are unable to move together. Using both eyes in unison enables us to see in greater detail and in three dimensions - for example to judge distances, size and compare the distance and relationship between near and far objects. This process is called binocular vision. People with strabismus will have difficulty with binocular vision. It is thought that Strabismus is caused by difficulties in how the brain 'communicates' with the affected eye muscles. It may also be caused by injuries to the muscles or nerves supplying them, abnormalities in the vision or visual pathway, or other developmental abnormalities such as the eye socket (orbit) being mal-formed, or the eye muscles themselves not forming properly.
Strabismus may cause the affected eye to turn in (convergent squint or esotropia), or turn out (divergent squint or exotropia). Squint may be present in all directions of gaze (concomitant), or just in a particular direction of gaze (incomitant). Sometimes squint will only be present when looking in the distance or just when looking at near objects.

Intervention for Strabismus is commonly provided to children with the condition before the age of 6. This might include providing support from an orthoptist. An orthoptist is an eye care worker that specialises in the diagnosis and management of defective eye movement and eye muscles. Intervention may take the form of wearing spectacles, performing eye exercises, or patching an eye for short periods. Surgery might also be required to correct the condition or later in life for ‘cosmetic’ purposes.

Children who receive successful intervention may not experience any further difficulties. People whose intervention is not successful, or whose strabismus became apparent in later childhood may experience more complex visual difficulties, such as double vision. Very often the brain is able to suppress the information from the affected eye and this can reduce double vision. People may also be prescribed spectacles to help reduce the impact of strabismus.
Many people with severe learning disabilities, or people with Cerebral Palsy might have strabismus.

If a squint develops in someone where it has not been present before then this may be due to a serious condition and advice should be sought from an eye-care professional or doctor as soon as possible.
Many people with severe learning disabilities, or people with Cerebral Palsy might have strabismus. People with Fragile X syndrome are more prone to having strabismus. Fragile X Syndrome. Fragile X is the most common form of inherited learning disability.  If a 'squint' appears in later life then it might indicate a more serious problem and medical attention should be sought immediately.

For people with communication difficulties it may be very difficult for them to tell you how they see their world. It requires skilled observation and good knowledge of the person to begin to understand how a person might be seeing their world. A functional vision assessment is an important method of assessing someone’s vision.

For more information on squint click here to visit the NHS choices website