RETINA
Retina is the light sensitive layer at the back of your eye. The retina can get diseased in a variety of conditions leading to visual loss which can sometimes be severe and irreversible. Some of the common retinal diseases are
1) Diabetic Retinopathy:
India has surpassed China as the diabetic capital of the world. Diabetes affects the small blood vessels in the retina which can lead to leakage, swelling, bleeding and detachment of the retina.
NO WARNING SYMPTOMS: In early stages of diabetic retinopathy, the vision is frequently normal hence there is no red flag symptom that can alert the patient about the presence of diabetic retinopathy. Symptoms appear when retinopathy has fairly progressed and include blurring of vision, difficulty in reading, seeing floaters/black spots, sudden loss of vision etc.
Stages of diabetic retinopathy:
- Non proliferative: This stage has presence of small dot haemorrhages and cotton wool spots with or without retinal swelling. Cases with no swelling usually have no symptoms.
- Proliferative: This is advanced form of retinopathy where the blood supply of the retina is so compromised that it leads to formation of abnormal and brittle new blood vessels which can bleed, pull and detach the retina or cause glaucoma. This stage is reached usually when the blood sugar is highly uncontrolled with a long duration of diabetes.
- Diabetic Macular Edema: Swelling in the most sensitive part of retina can develop in both nonproliferative and proliferative stages, and cause reduction in vision.
Other risk factors associated with Diabetic Retinopathy
- Hypertension/ High blood pressure
- Hyperlipidemia/ High cholesterol
- Anemia / Low haemoglobin
- Pregnancy
- Diabetic nephropathy/ Kidney damage due to diabetes
2)Retinal Detachment:
Symptoms
- Sudden visual loss
- Curtain falling in front of eyes
- Flashes and floaters
Types of Retinal Detachment
- Rhegmatogenous RD:This type of detachment occurs due to formation of a hole/tear in the retina which allows liquid vitreous to seep in and detach it. It is the commonest form of RD. The hole/tear forms due to abnormal vitreous pull, or degenerative changes in a weak spot in the retina like lattice degeneration.
- Tractional RD:Tractional RD occurs due to abnormal membranes and vitreous jelly that mechanically pull and detach the retina. It is seen in proliferative diabetic retinopathy, retinopathies due to vein occlusions, ROP and some uveitic and congenital diseases.
- Exudative RD:Sometimes overproduction of fluid inside the eye due to a tumor or certain uveitic diseases can lead to fluid accumulation underneath the retina leading to its detachment.
Treatment of Retianl Detachment
Early cases of rhegmatogenous RD can be treated by sealing the hole/tear responsible with laser or cryotherapy. Cases with larger detachments usually need surgery in the form of pneumatic retinopexy, scleral buckling or vitrectomy.
Tractional RD requires vitrectomy surgery wherein all the responsible membranes and anomalous vitreous is removed to reattach the retina.
Treatment of exudative RD involves treatment of the underlying cause.
3)Age Related Macular Degeneration (AMD)
As age advances, degenerative changes can set in the most sensitive portion of your retina i.e the macula. AMD is generally of two types: Dry and Wet.
Dry AMD:
The degenerative changes involve deposition of yellow material called drusen in the outer layers of the retina and oxidative stress related changes that damage the retinal pigment epithelium and photoreceptors. Early stages have no symptoms but advanced disease is associated with significant visual loss due to atrophy of the layers of the retina at the macula.
Dry AMD cannot be cured, but the progression can be slowed by use of antioxidants
Wet AMD:
This is characterized by development of abnormal new blood vessels, that grow from underneath the retina through the diseased outer layers leading to bleeding and swelling and consequent visual loss. Visual loss, especially in this type of AMD can be severe.
Wet AMD can be controlled by the application of intravitreal injection of Anti Vascular Endothelial Growth Factor (Anti-VEGF) agents, that shrink these abnormal vessels. It requires retreatment at frequent intervals until the disease settles.
4)Retinal Vein or Artery Occlusion:
This can occur usually secondary to systemic diseases like hypertension and diabetes. Occlusion of the blood supply leads to either swelling or permanent damage to the retina. Treatment involves intravitreal Anti VEGF injections, laser and surgery.
5)Macular hole and Epiretinal Membranes:
The vitreous jelly can become abnormal in some patients and lead to formation of a membrane or a hole at the macula. Treatment usually involves surgery.
UVEITIS
The eye is a privileged organ, where in not everything that enters our bloodstream enters it. This is achieved by the presence of a blood-ocular barrier that prevents antigens from entering the eye and inciting inflammation.
However, the integrity of the blood ocular barrier is lost in certain infections and autoimmune diseases and inflammation in the structures of the eye lead to vision loss. This condition is termed uveitis.
Uveitis can occur in any part of the eye. In India, Tuberculosis is a common cause of uveitis. Apart from infectious diseases likeTB, autoimmune conditions like Ankylosing spondylitis, Psoriasis, Juvenile Rheumatoid Arthritis, Behcet’s disease etc are common diseases causing ocular inflammation.
Treatment of uveitis is challenging and prolonged. It involves suppression of inflammation using local/systemic steroids and immunosuppression. The most important factor is to treat the underlying disease.