Eye Conditions

RETINITIS PIGMENTOSA

There are many different forms of Retinitis Pigmentosa (RP)

They vary according to the type of inheritance (see genetic causes under research), the age of onset and the specific gene mutation involved. To date more than 60 genes have been associated with RP. Each patient should have a good clinical and genetic diagnosis to fully understand the specific condition in each family. This serves as a general guide only. Retina South Africa can facilitate genetic testing and counselling. Assistive devices and programmes will help patients to manage their lives.

The symptoms of RP include night vision loss, poor contrast vision, slow light-to- dark adaptation times and later loss of side (peripheral) vision. The age of onset and the progression of vision loss is variable and even within a family differs from person to person. The condition is inherited in a Recessive, Dominant or X Linked manner and genetic counselling will help to determine who in the family is at risk or may be carriers of the gene mutation. Central vision is often retained until later years and good nutrition, no smoking and a healthy life style will do much to slow the progression of the disease. Supplements  containing Lutein, Zeaxanthin, Alpha Lipoic acid and L- Glutathione may slow the rate of degeneration. Clinical trials in the fields of gene therapy, stem cells, photoswitches and artificial vision are showing promising results in the RP therapy. Retina South Africa offers counselling and referrals to service providers. We also facilitate genetic testing.

Retinitis Pigmentosa

How people with Retinitis Pigmentosa see

AGE-RELATED MACULAR DEGENERATION [AMD]

The first symptoms of AMD are usually visual distortion of straight lines and difficulties in reading, recognition of faces and other fine-focus visual tasks. Many AMD sufferers are also very sensitive to bright sunlight. Side vision is generally retained.

THERE ARE TWO KINDS OF AMD: WET AND DRY.

  1. The dry form is more common and accounts for about 90% of all AMD. It is sometimes called drusenoid, atrophic or non-exudative. Yellow-white deposits called drusen accumulate in the retinal pigment epithelial (RPE), a layer of “nurse” cells located beneath the photoreceptors.  With age and a genetic predisposition, waste products accumulate in the RPE and interfere with the function of the light-sensitive photoreceptors.  Not everyone with drusen will experience vision loss, and the rate of loss may be quite slow.
  2. Wet AMD is also called choroidal neovascularisation, exudative, or disciform degeneration. Abnormal blood vessels form in the central macula area of the retina. These leak fluid and blood, damaging the retina and the photoreceptor cells. Wet AMD can progress rapidly and cause severe vision loss. It can sometimes be treated with laser, photodynamic therapy (PDT) or anti- angiogenic therapy.  The Amsler Grid is useful in home-testing for rapid changes in vision, which should be reported to your eye specialist immediately.

Risk Factors

Research shows that smokers have a higher risk of developing AMD and this is compounded by genetic factors.  Other factors such as high levels of sunlight, poor diet and genetic predisposition are all thought to play an important role in AMD.  Research into anti- oxidants have suggested that high levels of vitamins, anti-oxidants and trace minerals may offer some protection against AMD.

It is estimated that 18 % of Caucasians over the age of 55 years may be at risk and this risk increases to 30% in people over the age of 74. The WHO has now elevated AMD to the third largest global cause of vision loss, and the single largest cause of blindness in developed  countries.

What can you do to protect your vision:

  • Stop smoking now! Your risks only lessen 10 years after stopping
  • Eat a healthy diet- green, leafy vegetables such as spinach are high in Lutein, a powerful anti- oxidant that is found in the macular part of the retina while yellow vegetables are high in beta carotene, also a good anti-oxidant
  • Control blood pressure, cholesterol and fat intake – they have all been implicated in AMD
  • Wear sunglasses that screen out UVa, UVb and blue light.
  • Have regular eye checks
  • See an eye specialist immediately if you experience the sudden distortion of straight lines or loss of vision
  • Discuss dietary supplements with your eye specialist

JUVENILE CENTRAL VISION LOSS

Central Vision loss

There  a number of conditions causing central vision loss that can affect children as young as  5 years old, but may also be diagnosed in young and older adults. These are the most common forms:

Stargardt Disease

This condition leads to severe central vision loss and the early symptoms include difficulty in reading,writing and the recognition of faces. Side [peripheral] and night vision are most often not affcetd. It is most commonly inherited in an Autosomal Recessive manner where both parents are unknowgly carrying a single copy of a gene mutation. The most common gene mutations associated with Stargardt Disease are in the ABA4 gene. Supplements containing Vitamin A and Betacarotene  may accelerate the rate of waste product build up in the retina nd should be avoided. Sunlight protection is also advised. For more information on Stargardt Disease, genetic testing and clinical trials contact Retina South Africa

Central Vision Loss

How people with central vision loss see

Cone Rod Dystrophy

This condition often start with central vision loss and may be diagnosed as Stargardt Disease. In later years night vision may be affected which would indicate that the rod photorecptors are also involved. Mutations in the ABCA4 gene are often found in Cone Rod Dystrophy. Diet and protective advice is as for Stargardt Disease – above. Contact Retina South Africa for more information.

Cone Dystrophy

It is not easy to differentiate between Cone and Cone Rod Dystrophy. One of the main clinical differences is the later age of onset in cone dystrophy. An Electro Retina Gram[ ERG] will help your diagnosing eye specialist detect if there is Rod involvement. Cone Dystrophy may be inherted in an X linked pattern. ABCA4 gene mutations are less common in Cone Dystrophy and genetic testing may help to find a definite diagnosis.

Best Disease

This is also known as Vitelliform macular dystrophy and causes central vision loss due to a build-up of fatty yellow pigment (lipofuscin) in the RPE, which lies underneath the photoreceptor layer. Affected patients do not typically lose side (peripheral) vision or the ability to see at night.

The two forms have similar features, but the early-onset form (known as Best Disease) usually appears in childhood but the onset of symptoms and the severity of vision loss vary widely. The adult-onset form begins later, usually in mid-adulthood, and tends to cause vision loss that worsens slowly over time. The two forms of Vitelliform macular dystrophy each have characteristic changes in the macula that can be detected during an eye examination.

In some cases, Best Disease does not progress far enough to cause significant central vision loss.  However, retinal specialists can still detect the disease using sophisticated diagnostic tests that measure the function of the RPE and the retina.  Individuals with Best Disease are also often farsighted and this can be corrected with spectacles.  People with Best Disease do not usually require mobility assistance as their peripheral vision usually remains unaffected.

Best Disease is usually inherited as an autosomal dominant trait. Genetic testing is available for Best Disease.

 

USHER SYNDROME

This is an inherited condition characterized by hearing impairment and progressive vision loss. The vision loss is due to Retinitis Pigmentosa (RP), a degenerative condition of the retina, and usually appears during adolescence or early adulthood. Balance may also be affected. Symptoms vary from person to person and progress at different rates.  Researchers are studying causes and potential treatments for Usher Syndrome and other retinal degenerative diseases. Excellent progress in research has been made recently and several clinical trials are in progress.

There are at least three different forms of Usher Syndrome. People with Usher Syndrome Type 1 (USH1) are usually born with severe hearing loss and experience problems with balance. The first signs of RP — night blindness and loss of peripheral vision — usually appear in early adolescence.

In Usher Syndrome Type 2 (USH2), new-born children have moderate to severe hearing impairment. Symptoms of RP typically start shortly after adolescence. Visual problems progress less rapidly than in Usher Type 1 and hearing loss usually remains stable.

In the more rare third type of Usher Syndrome (USH3) children are usually born with good or only mild impairment of hearing. Their hearing and vision loss is progressive, starting around puberty.  Balance may also be affected.

Hearing loss in Usher Syndrome is due to a genetic mutation (alteration) affecting nerve cells in the cochlea, a sound-transmitting structure of the inner ear. The same genetic defect also adversely affects photoreceptor cells in the retina, leading to vision loss.

Usher Syndrome is passed from parents to their offspring through an autosomal recessive inheritance trait or condition.  In this type of inheritance, two copies of a mutated [changed] gene, one from each parent, are required for the child to be affected. A person with only one copy of the gene is a “carrier” and rarely has any symptoms.

Worldwide, it is the leading cause of combined deafness and blindness. Genetic testing is available through Retina South Africa to help people define their condition and the risk of other family members or future offspring being affected.

DIABETIC RETINOPATHY

Diabetes Related Sight Loss – Diabetic Retinopathy  

Diabetes is a disease that occurs when the pancreas does not secrete enough insulin or the body is unable to process it properly. Insulin is the hormone that regulates the level of sugar (glucose) in the blood.

The effect of diabetes on the eye is called diabetic retinopathy. DR is a common complication of diabetes, it may not have any symptoms or may not affect sight in the early stages but, as the condition progresses, eventually the sight will be affected. When the condition is caught early, treatment is effective at reducing or preventing damage to sight.

DR is thought to be the most common form of blindness in people of working age in the developed world. In about 10% of cases, diabetic macular oedema (DME) may occur where blood vessels leak their contents into the macular region of the retina and this may cause a more rapid form of vision loss.

The earliest phase of diabetic retinopathy is known as ‘background diabetic retinopathy’. Often there are no symptoms in the early stages of the disease, nor is there any pain. In this phase, the arteries in the retina become weakened and leak, forming small haemorrhages. These leaking vessels often lead to swelling or oedema in the retina. As the disease progresses, some blood vessels that nourish the retina become blocked, over time worsening and depriving several areas of the retina with their blood supply.

In advanced DR the signals sent by the retina for nourishment trigger the growth of new blood vessels. This condition is called proliferative retinopathy. These new blood vessels are abnormal and fragile. They grow along the retina and along the surface of the clear gel that fills the inside of the eye. By themselves, these blood vessels do not cause symptoms or vision loss. However, they have thin, fragile walls. If they leak blood, severe vision loss and even blindness can result.

A condition known as diabetic macular oedema occurs when blood leaks into the centre of the retina, known as the macula, the part of the eye where sharp, straight-ahead vision occurs. The fluid makes the macula swell, blurring vision. This can occur at any stage of DR although it is more likely to occur as the disease progresses.

Prevention of diabetic retinopathy is the most important step to take for anyone with diabetes. Researchers have found that diabetic patients who are able to maintain appropriate blood sugar and blood pressure levels have fewer eye problems than those with poor control. Diet and exercise play important roles in the overall health of people with diabetes.

People with diabetes can also greatly reduce the possibilities of eye complications by going for regular examinations with an eye doctor.

Diabetic retinopathy is treated in many ways depending on the stage of the disease and the specific problem that requires attention. The doctor relies on several tests to monitor the progression of the disease and to make decisions for the appropriate treatment. Laser eye surgery called pan retinal photocoagulation (PRP) is one treatment choice to prevent the blood vessels from leaking, or to get rid of the growth of abnormal, fragile vessels. A new class of drugs have recently become available to treat macular oedema and they are often used in conjunction with the laser therapy. These are anti-VEGF (Vascular Endothelial Growth Factor) drugs and they target the substance in the body which is responsible for the development of blood vessels. In diabetic macular oedema, too much VEGF is produced in the eye, and these drugs block the production of these new, abnormal vessels.

Vitrectomy is another surgery commonly needed for diabetic patients who suffer a vitreous haemorrhage (bleeding in the gel-like substance that fills the centre of the eye). During a vitrectomy, the retina surgeon carefully removes blood, fibrous tissue and vitreous from the eye, relieving traction on the retina and preventing retinal detachment. If retinal detachments or tears occur, they are often sealed with laser surgery. Retinal detachment requires surgical treatment to re-attach the retina to the back of the eye. The prognosis for visual recovery is dependent on the severity of the detachment.

See your eye specialist often and urgently in the case of sudden vison loss.

RARE CONDITIONS

Achromatopsia

This is a rare disorder which affects around 1 person in 33,000. There are complete and incomplete forms of achromatopsia. Persons with complete achromatopsia have no cone vision and so rely on their “rod vision.”  Rods are located mostly at the periphery of the retina. Therefore patients are not able to adapt normally to higher levels of illumination. Rods do not provide colour vision or good detail vision. Therefore, persons with achromatopsia are either totally colour-blind or almost totally colour-blind, and they have poor visual acuity. The type of vision loss is varies considerably. There are complete rod monochromats, incomplete rod monochromats, and blue cone monochromats. Complete rod monochromats have the most severely impaired vision of all achromats. Blue cone monochromacy is much rarer than rod monochromacy and has entirely different inheritance factors.

Sometimes a patient with rod monochromacy may be diagnosed as having cone dystrophy Congenital achromatopsia is not progressive, and it does not lead to blindness. Some doctors refer to it as “stationary cone dystrophy.”

Nystagmus (involuntary movement of the eyes) is a symptom of achromatopsia, one that is especially noticeable during infancy and childhood, but having this symptom is not the same as having the medical eye condition which is known as “congenital nystagmus.”Patients are very uncomfortable in full sunlight outdoors or in very bright indoor spaces, so almost all achromats use very dark tinted lenses.

Choroideremia

Choroideremia is a retinal degeneration that begins with reduction of night vision and gradually progresses to blindness by middle age. The appearance of the fundus in sufferers is recognizable by the characteristic pale colour caused by the loss of the outer retina, retinal-pigmented epithelium, and choroidal vessels, leading to exposure of the underlying sclera. Choroideremia is inherited in an X linked recessive way.  The CHM gene encodes for the Rab escort protein 1 (REP1). Research towards establishing a clinical trial is under way.

Gyrate Atrophy

This rare condition causes atrophy of the choroid and the retina. Affected patients usually develop night blindness during the first decade of life and experience progressive loss of visual field and visual acuity later in the disease course. The vision loss is progressive and as yet untreatable. It is inherited in an autosomal recessive pattern.

The gene mutation is found on chromosome 10 which encodes for an enzyme called ornithine ketoacid aminotransferase (OAT). Different mutations in OAT cause differences in the severity of symptoms of the disease. It is known that reduction of the amino acid arginine in the diet has a beneficial effect on most patients,  but the diet is very difficult to maintain and must be monitored by pediatricians with experience in metabolic diseases. Vitamin B6 treatment lowers the plasma ornithine levels in a small percentage of gyrate atrophy patients. Whether such a reduction improves the long-term visual outcome is unknown, but, unlike arginine restriction, vitamin supplementation is relatively easy to administer. Long-term vitamin therapy should be considered only for patients whose ornithine levels can be shown to drop in response to treatment.

 

Leber Congenital Amaurosis

LCA is an inherited retinal degenerative disease characterized by severe loss of vision at birth. A variety of other eye-related abnormalities including roving eye movements, deep-set eyes, and sensitivity to bright light also occur with this disease. Some patients with LCA also experience central nervous system abnormalities.

Eye examinations of infants with LCA reveal normal appearing retinas. However, electroretinography (ERG) tests, which measure visual function, detect little if any activity in the retina. A low level of retinal activity, measured by ERG, indicates very little visual function. ERG tests are key to establishing a diagnosis of LCA.  By early adolescence, various changes in the retinas of patients with LCA become readily apparent. Blood vessels often become narrow and constricted. A variety of pigmentary changes can also occur in the retinal pigment epithelium (RPE), the supportive tissue underlying the retina. Sometimes, pigmentary changes are similar to another retinal degenerative disease known as retinitis pigmentosa. Although the appearance of the retina undergoes marked changes with age, vision usually remains fairly stable through young adult life.  Some patients are also extremely sensitive to light (photophobia). Patients with remaining vision are often extremely farsighted.

LCA is genetically passed through families by the autosomal recessive pattern of inheritance. In this type of inheritance, both parents are carriers of a single copy of a gene mutation.  To date more than 15 genes have been associated with LCA. Gene replacement for the RPE65 form has been in gene replacement clinical trials for many years and will soon become commercially available.  See also the information on genetics and research on this website. Call Retina South Africa to find out about genetic testing.

Retinoschisis

This is a genetic disorder that causes splitting through the layers of the retina, the light-sensitive neural tissue in the back of the eye. The disorder is characterized by a slow, progressive loss of parts of the field of vision corresponding to the areas of the retina that have become split. It may be associated with the development of saclike blisters (cysts) in the retina. Patients will have a reduction in visual acuity and there may also be a loss of peripheral vision. Very few people become totally blind but it may result in very poor vision in later years.  Vision loss usually starts by early grade school age and slowly worsens over the next several decades as cells in the retina lose function and die. The gene mutations are carried on the X chromosome and thus inherited from mother to child. Typically only males develop symptoms. The causative gene is Retinoschisin 1 (RS1) which codes for the retinoschisin protein, which normally works like double-sided tape, providing lateral adhesion that holds retinal cells together. RS1 gene mutations alter the protein and thereby interfere with the ability of cells to maintain proper structure of the retina. The first- ever human gene therapy trial for XLRS is in progress.  Retina South Africa is working with the University of Cape Town to bring promising clinical trials and therapies to South Africa.

Information on other rare retinal conditions is available from Retina South Africa :

  • Fundus albipunctatis
  • Familial exudative vitreoretinopathy
  • Kearns-Sayre syndrome
  • Lawrence Moon  and Bardet-Biedl syndrome
  • Dominant drusen
  • Macular pattern dystrophy
  • Sorsby’s  Fundus  Dystrophy
  • Refsum disease
  • Atypical RP [ punctata albescens, rp+ ex. Vas.etc]
  • Pseudoxanthoma elasticum
  • Stationary nightblindness

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