The retina is a thin layer of tissue that lines the back of the eye on the inside. It is located near the optic nerve. The purpose of the retina is to receive light that the lens has focused, convert the light into neural signals, and send these signals on to the brain for visual recognition.
The retina processes light through a layer of photoreceptor cells. These are essentially light-sensitive cells, responsible for detecting qualities such as color and light-intensity. The retina processes the information gathered by the photoreceptor cells and sends this information to the brain via the optic nerve. Basically, the retina processes a picture from the focused light, and the brain is left to decide what the picture is.
Due to the retina’s vital role in vision, damage to it can cause permanent blindness. Conditions such as retinal detachment, where the retina is abnormally detached from its usual position, can prevent the retina from receiving or processing light. This prevents the brain from receiving this information, thus leading to blindness.
Types of Retinal Disorders (Retinopathy)
- Age-related macular degeneration
- Retinal detachment
- Diabetic retinopathy
- Diabetic maculopathy
- Inherited retinal disease
- Macular hole/pucker
- Retinitis Pigmentosa
- Stargardt disease
Causes of Retinal Disorders
Though many retinal disorders are inherited, some are caused by the adverse effects of medications or by infections.
Retinopathy of Prematurity (ROP) is a condition that occurs in premature infants, which results in problems with blood vessels that grow out of control along the retina. Some retinal disorders are related to illness, such as diabetes, while others can be caused by medications, such as seizure medications or chemotherapy which can have a toxic effect on the retina.
Most retinal conditions fall into two broad categories: stationary and progressive. Even within these two groups there is a diverse mix of symptoms and severity of visual impairment. While stationary retinal diseases are present at birth, the level of vision loss remains the same over time. Examples of stationary conditions include Leber Congenital Amaurosis, which causes severe visual impairment, and congenital stationary night blindness, which results in decreased night vision. Progressive conditions may not be apparent at birth, but as time passes vision decreases. An example of this is Retinitis Pigmentosa, which results in a wide range of decreased vision.
Examination for Retinal Disorders (Retinopathy)
To diagnose retinal detachment, your doctor will ask you questions about your symptoms, past eye problems, and risk factors. The doctor will also test your near and distance vision (visual acuity) and side (peripheral) vision. These routine vision tests do not detect retinal detachment, but they can find problems that could lead to or result from retinal detachment.
A doctor can usually see a retinal tear or detachment while examining the retina using ophthalmoscopy. This test allows the doctor to see inside the back of the eye using a magnifying instrument with a light.
If a retinal tear or detachment involves blood vessels in the retina, you may have bleeding in the middle of the eye. In these cases, your doctor can view the retina using ultrasound, a test that uses sound waves to form an image of the retina on a computer screen.
It’s important to have routine eye exams so that your eye doctor can look for retinal tears or other eye problems that could lead to retinal detachment. If you have a condition that puts you at high risk for retinal detachment-such as nearsightedness, recent cataract surgery, diabetes, a family history of retinal detachment, or a prior retinal detachment in your other eye, talk to your doctor about having more frequent exams to detect problems in their early stages.
If you notice floaters or flashes of light, let your doctor know about it right away. These symptoms could be a warning sign of a retinal tear that can lead to detachment.
More about the different types of retinal disorders
- Age-related macular degeneration (AMD) is the most common cause of blindness in people over 65 in Industrialised countries.
- Research into the causes is ongoing, but factors such as genetic make-up, smoking, cardiovascular problems and diet are related to this condition.
AMD affects the central part of the retina, called the macula. This part is responsible for the fine sight which is also the central field of vision. The main symptom is a progressive loss of vision, affecting the central part of the visual field.
There are 2 main types of AMD:
- Dry or atrophic AMD
The most common type. It causes a slow, progressive loss of vision. There is no treatment for this condition and only a change of diet and use of vitamin complexes appear to slow progression.
- Wet or neovascular AMD
Less common. Progresses faster than atrophic AMD, sometimes within days, causing macular haemorrhages. The growth of small vessels within the retina in the macular area is the main problem. There are new treatments that can be tried with this type of AMD.
Retinal detachment is a very serious eye condition that happens when the retina separates from the tissue around it. Since the retina can’t work properly under these conditions, you could permanently lose vision if the detached retina isn’t repaired promptly.
Diabetic retinopathy is one of the most common causes of blindness in industrialised countries, affecting the retina of diabetic patients.
Diabetic retinopathy is related to the duration of the diabetes and the metabolic control of the patients; patients that control their diabetes poorly can develop retinopathy within a few years whilst patients that control their diabetes well may not develop retinopathy at all.
Diabetic retinopathy refers to the effect of diabetes on the retina. Sugar within the blood can have a damaging effect on the fine blood vessels of the retina. This can lead to leakage of blood and fatty deposits into the retina. Blurred vision can develop if this leakage occurs in the central part of the retina known as the macula. This process is known as diabetic maculopathy or Diabetic Macular Oedema (DMO).
Diabetic maculopathy is one of the leading causes of blindness in the Western working population and early treatment can now reverse visual loss.
Inherited retinal disease
Inherited retinal disorders most commonly present from birth/early infancy to the second/third decades. Inherited retinal conditions now represent the commonest cause of severe visual loss in the working age population and the second commonest in childhood in the UK.
They are a very variable group of conditions, which require specialist retinal expertise to establish an accurate timely diagnosis with appropriate examination and investigations, in order to provide reliable advice, information on prognosis and offer appropriate genetic counselling.
In many instances these disorders may be complicated by other eye conditions including cataract, glaucoma, macular oedema or choroidal neovascularisation – for which treatments are available.
The majority of inherited retinal conditions are isolated problems with no general health concerns, however, some are associated with other disorders such as hearing loss or diabetes.
There are multiple avenues of research being explored including gene therapy, stem cell therapy, artificial vision and pharmacological approaches, with several on-going clinical trials and many more planned in the immediate future. There is cautious optimism that some of these will likely result in meaningful treatments.
A macular hole is a small break in the macula, located in the center of the eye’s light-sensitive tissue called the retina. The macula provides the sharp, central vision we need for reading, driving, and seeing fine detail.
A macular hole can cause blurred and distorted central vision. Macular holes are related to ageing and usually occur in people over age 60.
Retinoblastoma is a cancer that starts in the retina, the very back part of the eye. It is the most common type of eye cancer in children. Rarely, children can have other kinds of eye cancer, such as medulloepithelioma, which is described briefly below, or melanoma.
Retinitis pigmentosa (RP) is the name given to a group of inherited diseases of the retina that all lead to a gradual progressive reduction in vision. RP affects approximately 1 in 3,500 to 4,000 people.
Difficulties with night vision and peripheral vision are the first things that are noticed. Later, reading vision (detailed vision) and colour vision are affected. The age at which symptoms start is variable and may vary with the different genetic types. The rate at which vision deteriorates is also variable but is generally very slow with changes occurring over years rather than months.
In approximately half of all cases (50 to 60%) there are other family members with RP. There are three main inheritance patterns, autosomal recessive, autosomal dominant and X-linked inheritance, depending on the genetic cause.
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