A rare eye disease is generally defined as a condition that affects a very small percentage of the population (for instance, fewer than 1 in 2,000 people). While many are genetic and present from childhood, the list of such conditions is vast, with over 900 documented. They are often difficult to diagnose and have limited treatment options, earning them the name “orphan diseases”.
Below is a list of several significant rare eye diseases, categorized for clarity, along with explanations of each.
These conditions affect the retina, the light-sensitive tissue at the back of the eye.
| Disease | Key Characteristics |
|---|---|
| Stargardt Disease | A genetic disorder that causes progressive damage to the macula, leading to central vision loss, often beginning in childhood or adolescence. |
| Retinitis Pigmentosa (RP) | A group of genetic disorders that cause a gradual decline in vision due to the degeneration of rod and cone photoreceptor cells. It typically leads to difficulty seeing at night and a loss of peripheral (tunnel) vision. |
| Usher’s Syndrome | A genetic condition characterized by both hearing loss (often from birth) and progressive vision loss due to retinitis pigmentosa. It is a major cause of deaf-blindness. |
| Birdshot Chorioretinopathy | A rare form of posterior uveitis (inflammation of the uvea) that can cause floaters, blurred vision, and night blindness. It is an autoimmune disease that can be difficult to diagnose early on. |
| Retinoschisis | A rare condition where the retina splits into separate layers, leading to blurry vision and potential vision loss. Juvenile X-linked Retinoschisis is a specific form that causes progressive macular degeneration in children. |
| Bardet-Biedl Syndrome (BBS) | A genetic condition that primarily causes retinal dystrophy (similar to retinitis pigmentosa) leading to vision loss. It is also associated with other symptoms like extra fingers/toes, obesity, and kidney dysfunction |
Complete Guide About How To Test The Eye Diseases For Doctors.
Various alterations of vision may occur:
- Dazzling, or difficulty seeing in bright light may be caused by opacities in cornea or lens.
- Visual field defects may be caused by various disorders in the nerve or visual pathways.
- Photophobia is discomfort caused by bright light. It is usually inflammatory eye disease, especially a corneal ulcer.
- Distortion of shapes usually indicates a disturbance of the retina macular.
- Haloes, or rainbow-coloured rings around lights are caused either by early opacities in the lens, or by corneal oedema. Very small drops of fluid cornea split white light into the colours of the spectrum. Corneal oedema usually indicates a rise in intraocular pressure.
- Spots which ‘float’ in front of the eyes (floaters) are usually opacities in the vitreous body, which cast a shadow on the retina.
Discomfort or pain in the eye
This is usually a symptom of inflammation of the eye, or of the surrounding the eye, or of the structures surrounding the eye.
- The conjunctiva is not very sensitive to pain. Typically, conjunctivitis with discomfort, irritation or prettiness rather than pain.
- The iris and cornea are both very sensitive to pain. Iris, corneal acute glaucoma are three common eye conditions which are characterized moderate or severe pain.
- Inflammation of the choroid (thyroiditis) or optic nerve optic neuritis usually produces a sensation of dull pain behind the eye.
‘Eye strain’ and tiredness of the eyes are common complaints. Sometimes the intraocular muscles of both eyes are not equally balanced, and , strain. However, it is more likely that the cause is psychological rather organic, and means that the patient cannot cope with the stresses of everyday life. Eye strain is very common among students who are having difficult studies. (Many people think that eye strain is caused by refractive errors the patient needs spectacles. However, refractive errors usually cause the vision rather than any specific discomfort or pain.)
Other symptoms
- Discharge, or watering of the eyes is common. It usually indicates conjunctivitis, or an obstruction in the lacrimal passages.
- Diplopia (double vision) is a feature of many types of squint. It will disappear when one eye is shut. Occasionally both the two images come only. This is usually caused by an opacity in the cornea or ler.5. n the light rays from focusing clearly on the retina.
- A headache is a very common symptom, but it is not usually caused by eye disease. However, diseases such as hypertension and intracranial cause headaches and may also produce eye changes.
Testing The Vision
The human eye is an extremely complex organ, and there are many different ways to test the vision. In practice, however, only three types of test are used:-
- Visual acuity, which tests if the patient can see small objects or letters in good light directly ahead.
- The visual field, which tests the overall area of vision for each eye.
- Colour vision, which tests if the patient can discriminate between different colours.
Visual Acuity
It is important to test the visual acuity in each eye separately, if possible. This is usually measured with showing either letters, or pictures for patients who cannot read. If the vision is very poor, other tests are usually appropriate
Unfortunately the method for recording visual acuity is rather complicated. Near each line on the chart is a small number. This number is the distance (in meters) at a person with normal sight should be able to see that line. For example a normal person can see the top letter at 60 metres, the second line at 36 and so on. The patient stands 6 metres away from the chart, and reads as much as he can.If the patient can only see the top letter of the chart, his vision is 6/60. If he can par m the second line, his vision is 6/36, and so on.
Fraction is the distance between the patient and the chart. The bottom number of the smallest line of letters the patient can read.) A normal sight should reach the line which is marked with a 6. This is 6/6 vision.
If the vision is below 6/60 and the patient cannot even see the should come nearer the chart until he can see it. If he can see it a: 21 vision is 2/60. If he can only see it at 1 metre, his vision is 1/60. of testing people with poor vision is to ask the patient to count fingers.The human finger is about the same size as the top letter on the chart, a” and so counting fingers at 6 metres is about equal to 6/60 vision. Counting fingers distance is therefore the same as 1/60.
If the vision is below 1/60, the patient may still be able to detect:: of a hand in front of his eye. If not, the final test is to shine a light There are therefore 3 more categories: –
- HM — Hand movements can be seen in front of the eye.
- PL — Perception of a light shone into the eye.
- NPL — No perception of light, or total blindness.
If there is perception of light, it is also important to test if the patient identify the direction the light is coming from. This is called projection of light. Good projection usually indicates that the retina and optic nerve are| normally. The defect is probably an opacity in the cornea, lens or vitreous body and is treatable. Poor projection of light indicates retinal or opt:: and is probably untreatable.
It is necessary to retest any patient with defective visual activity through a pinhole. If the visual acuity improves when the through a pinhole, it indicates an error of refraction, which spectacles can usually correct. If there is no improvement, then the loss of vision is from eye diseases.
Creating a complete tabular guide for testing various eye diseases involves compiling a structured format that includes several key columns. Here’s an example of how such a table could be structured:
- Disease Name: This column lists the names of various eye diseases.
- Symptoms: Here, you would describe the common symptoms associated with each disease.
- Diagnostic Tests: This column details the tests or examinations used to diagnose each disease.
- Risk Factors: Lists factors that increase the likelihood of developing each disease.
- Preventative Measures: Offers advice on how to possibly prevent each disease.
- Treatment Options: Describes the available treatments for each condition.
- Prognosis: Provides information on the likely course or outcome of the disease.
