What is retina?
The retina is a layer of nerve tissue at the back of the eye which contains photoreceptors. These photoreceptors receive light which is then converted to electrical signals transmitting to the brain via the optic nerve.
What is retinal detachment?
Retinal detachment is when the retina is pulled away from its normal position and separated from the underlying tissues within the eye. The retina will not be able to function normally and blurring of vision will occur. A retinal detachment can progress and result in total retinal detachment, affecting the whole retina.
Causes of Retinal Detachment
- Posterior Vitreous Detachment is an ageing process. The vitreous, a jelly-like substance which gives our eye its shape, shrinks and liquefies causing the vitreous to pull away from the retina. Traction occurs as a result when the vitreous pulls and tugs onto the retina and flashes of light might be noticed at the peripheral of your vision. This could create holes or tears on the retina.
Posterior vitreous detachment
2. Retinal holes and tears are usually caused by posterior vitreous detachment. If treatment is not carried out, fluid from the vitreous will enter these holes or tears accumulating behind the retina. Build-up of fluid behind the retina separates and causes a retinal detachment.
Retinal hole causing fluid to enter behind the retina
Fundus photo of a retinal detachment
Risks of Retinal Detachment
- Serious trauma or injury to the eye or head
- Previous history of retinal detachment in other eye
- Family history of retinal detachment
- Weak areas in the retina
- New floaters
- Flashes of lights
- A shadow noted at the side of your vision
- Sudden blurring of vision
If new floaters or flashes of lights have been noted, it is important to schedule for a dilated retinal check with an Ophthalmologist to rule out any retinal holes or tears or detachment. It is important to address the issue of a retinal hole or tear and especially a retinal detachment to prevent the macula area of the retina from detaching.
Retinal Holes or Tears Surgery
Argon laser treatment is carried out if there are holes or tears in the retina. The laser would be applied around these holes or tears. Scar tissue will be formed around the retinal tear or hole sealing it to prevent fluid from entering them and causing a retinal detachment.
Retinal Detachment Surgery
Scleral buckling treatment is carried out by having a band made out of silicone or plastic around the outer wall of the eye acting as a belt, pressing the eye so that the retinal hole or tear is pushed against the wall of the eye. The surgeon usually drains out the fluid that is behind the retina, allowing the retina to flatten back into place.
Laser treatment may be carried out before this procedure.
A gas bubble is injected directly into the vitreous cavity inside the eye. The gas bubble will push the retina against the back of the eye, placing it back in its position.
Laser treatment may be carried out before this procedure.
Vitrectomy is usually carried out if there is traction when the vitreous is pulling on the retina or when there is bleeding in the vitreous. The jelly of the eye will be removed and replaced, removing this traction in the eye.
Scleral buckling may be performed together with vitrectomy.
Early intervention and treatment for retinal holes, tears and detachment is crucial as retinal detachment is progressive and may advance to loss of some or even all useful vision. Visual outcomes of the surgery are better when the retina is treated before the macula area of the retina is detached. However, the vision may or may not return back to normal.
CENTRAL SEROUS RETINOPATHY (CSR)
Central serous retinopathy (CSR), also known as central serous chorioretinopathy (CSC), is a visual impairment, often temporary, usually in one eye, mostly affecting males in the age group 20 to 50 but which may also affect women. The disorder is characterized by leakage of fluid in the central macula, which results in blurred or distorted vision (metamorphopsia). A blind or gray spot in the central vision is common, along with flashes of light (photopsia).
The diagnosis usually starts with a dilated examination of the retina, followed with confirmation by fluorescein angiography. The angiography test will usually show one or more fluorescent spots with fluid leakage. In 10%-15% of the cases these will appear in a “classic” smoke stack shape. An Amsler grid could be useful in documenting the precise area of the visual field involved.
CSR is a fluid detachment of macula layers from their supporting tissue. This allows choroidal fluid to leak into the subretinal space. The build up of fluid seems to occur because of small breaks in the retinal pigment epithelium.
CSR is sometimes called idiopathic CSR which means that its cause is unknown. Nevertheless, stress appears to play an important role. An oft-cited but potentially inaccurate conclusion is that persons in stressful occupations, such as airplane pilots, have a higher incidence of CSR. The “type A personality” has also been linked to this condition. However, the statistics may be skewed by the fact that CSR often goes undiagnosed or misdiagnosed; airline pilots and so-called “type A” people are demonstrably exacting, demanding people with (certainly in the case of pilots) better-than-average vision. They are more likely than the general population to notice the sometimes-subtle degradation of vision caused by CSR and insist on a believable diagnosis of it. People who need glasses may assume that the blurriness caused by CSR is simply a change in their prescription, and fail to have the condition assessed by a retinal specialist. These statistic-skewing factors undermine the conclusion that CSR is a condition specific to “type A” people.
CSR has also been associated with cortisol and corticosteroids, and persons with higher levels of cortisol than normal also have a higher propensity to suffer from CSR. Cortisol is a hormone secreted by the adrenal cortex which allows the body to deal with stress, which may explain the CSR-stress association. There is extensive evidence to the effect that corticosteroids (“cortisone”) — commonly used to treat inflammations, allergies, skin conditions and even certain eye conditions — can trigger CSR, aggravate it and cause relapses.
The incidence of CSR in persons with Cushing’s syndrome is 5%. Cushing’s syndrome is characterized by very high cortisol levels.
Recently found evidence has also implicated Helicobacter pylori as playing a role. It would appear that the presence of the bacteria is well correlated with visual acuity and other retinal findings following an attack.
Recent evidence also shows that sufferers of MPGN Type II kidney disease can develop retinal abnormalities including CSR caused by deposits of the same material that originally damaged the glomerular basement membrane in the kidneys.
Normal looking eye
Central Serous Retinopathy: ‘bubble’ on macula
OCT scan: normal macula
OCT scan: Central serous retinopathy
The prognosis for CSR is generally excellent. Over 90% of patients regain 20/30 vision or better within 6 months. Some visual abnormalities can remain even if visual acuity is measured at 20/20. Lasting problems can include decreased night vision, color discrimination problems, and some distortion. Long term complications can include subretinal neovascularization and pigment epitheliopathy.
There is no known effective treatment for the disease. Laser photocoagulation, which effectively burns the leak area shut, is sometimes suggested. In many cases the leak is very near the central macula, where photocoagulation would leave a blind spot. Additionally, a better long term outcome has not been demonstrated with photocoagulation. So more often than not the condition goes untreated.
Transpupillary thermotherapy has been suggested as a lower-risk alternative to laser photocoagulation in cases where the leak is in the central macula.
Any ongoing corticosteroid treatment should be stopped. Additionally, a new anti-microbial treatment will likely be recommended soon in light of recent findings regarding Helicobacter pylori.
CSR sufferers usually find their own ways to manage the condition, which may include stress reduction and changes in nutrition.
Some sufferers have partaken in (double blind placebo) marijuana therapy trials and symptoms have subsided.
What is epiretinal membrane?
Epiretinal membrane is also known as macular pucker. It is a thin sheet of fibrous tissue that can develop on the surface of the macular area of the retina.
The macula normally lies flat against the back of the eye, like film lining the back of a camera. When wrinkles, creases or bulges form on the macula, this is known as epiretinal membrane.
Macular pucker: Folds (wrinkles) are seen near the macula area
OCT Scan showing normal macula
OCT scan showing epiretinal membrane
Due to ageing, the vitreous gel (clear, gel-like substance) in the eye begins to shrink and pull away from the retina. As the vitreous pulls away, scar tissue may develop on the macula. The scar tissue can warp and contract and cause the retina to wrinkle or bulge.
Eye conditions such as vitreous detachment, torn or detachment retina, inflammation inside the eye, severe eye injury or disorders of the blood vessels in the retina can be associated with epiretinal membrane.
Most epiretinal membranes are mild and have little or no effect on vision. However, in some cases, the epiretinal membrane may slowly grow and begin to cause mechanical distortion (“wrinkling”) in the macula. This may lead to blurred or distorted vision, which may slowly worsen over time. An epiretinal membrane does not make an eye go completely blind. It typically affects only the center area of vision and does not cause a loss of the peripheral (side) vision.
For mild epiretinal membrane, no treatment is necessary. Changing glasses prescription may improve vision sometimes. Eyedrops, medicines or laser surgery do not improve vision.
For severe epiretinal membrane, a surgery called vitrectomy is recommended. It is usually performed as an outpatient procedure. The surgeon will remove the wrinkled tissue on the macula and the macula will flatten and vision will slowly improve, though it usually does not return all the way to normal.
Retinal Vein Occlusion
The retina is the layer of tissue at the back of the inner eye that converts light images to nerve signals and sends them to the brain. Retinal vein occlusion is a blockage of the small veins that carry blood away from the retina. Haemorrhages (bleeding) and leakage of fluid can occur from the areas of blockage.
Types of Retinal Vein Occlusion
There are 2 different types of retinal vein occlusion:
1. Central retinal vein occlusion (CRVO): Blockage at main vein of the eye located at optic nerve
2. Branch retinal vein occlusion (BRVO): Blockage at one of the smaller branches of vessels attached to the main vein
Central Retinal Vein Occlusion
Branch Retinal Vein Occlusion
Retinal vein occlusion is most often caused by hardening of the arteries (atherosclerosis) and the formation of a blood clot.
Risk factors of retinal vein occlusion include atherosclerosis, diabetes, glaucoma, hypertension (high blood pressure), high cholesterol and age-related vascular disease or blood disorders.
Because the risk of these disorders increases with age, retinal vein occlusion most often affects older people.
If a branch retinal vein occlusion occurs in one eye, there is an increased chance (about 10%) that a branch or central vein occlusion will occur in the eye in the future.
1. Central retinal vein occlusion (CRVO)
Central retinal vein occlusion (CRVO) is associated with painless unilateral (one eye) loss of vision. In some cases, this loss of vision is subtle in character, with intermittent episodes of blurred vision. In other cases, it may be sudden and dramatic.
CRVO can be sub-divided into non-ischaemic and ischaemic CRVO. The non-ischaemic type is often the more subtle of the two, while the ischaemic type is prone to the more acute clinical presentations.
- Non-ischaemic CRVO – Subtle, intermittent visual loss; painless; mild-to-moderate visual loss
- Ischaemic CRVO – Acute visual loss; pain may be present; marked visual loss
2. Branch retinal vein occlusion (BRVO)
Symptoms of Branch retinal vein occlusion (BRVO) are similar to CRVO. BRVO is often noted with an onset of blurred vision or visual field defect. Vision loss may be subtle. Patients with small occlusions of a branch retinal vein may often be asymptomatic. However, if larger obstructions are present, visual loss can be significant.
Complications of retinal vein occlusion
Complications include partial or complete loss of vision in the affected eye, macular edema (swelling of the macula), neovascularisation (abnormal vessel growth) or glaucoma. In severe cases of CRVO, a blocked vein causes abnormal blood vessel growth on the iris and drainage channels in the front of the eye, leading to painful pressure in the eye (neovascular glaucoma).
Many people will regain vision, even without treatment. However, vision rarely returns to normal. There is no way to reverse or open the blockage.
In some cases, treatment for the complications of retinal vein occlusion may be given including:
- Intraocular injections of anti-vascular endothelial growth factor (anti-VEGF) drugs into the eye. These drugs may block the growth of new blood vessels that can cause glaucoma. This treatment is still being studied.
- Focal laser treatment to treat macular edema
- Laser treatment to prevent the growth of new, abnormal blood vessels (neovascularisation) that leads to glaucoma
You may be able to prevent retinal vein occlusion from occurring again by properly managing any health conditions or associated risk factors such as diabetes, hypertension, high cholesterol or glaucoma.