Retina

What Is the Retina and How Is It Examined?

The retina is the light-sensitive layer of the eye. It lines the entire inner wall of the eye and is made up of nerves and blood vessels that come from the brain.
For a retinal examination, visual acuity is first measured and the patient undergoes a microscopic examination, after which dilating drops are applied to enlarge the pupil.
The pupil dilates over different periods depending on the individual and the disease — this time must be allowed before the examination.
The intra-ocular clear media (the lens and the vitreous) and the retina are then examined in detail using several different instruments.

Which Tests Are Performed to Diagnose Retinal Disease?

• Biomicroscopic and indirect retinal examination.
• Optical Coherence Tomography (OCT)
• Colour Fundus Photography
• Fundus Fluorescein Angiography (FFA)
• Indocyanine Green Angiography (ICGA)

People at risk of age-related macular degeneration are given an Amsler grid and asked to check it at regular intervals. If they notice distortion (waviness) they should come in for examination immediately.

What Are the Symptoms of Retinal Disease?

In retinal disease patients may complain of:

• reduced vision,
• distorted or wavy shapes,
• partial or patchy vision,
• floaters (black specks),
• flashes of light or shadows,
• reduced or absent vision in darkness or in bright light.

What Is Retinal Detachment and What Are Its Symptoms?

Symptoms include flashes of light, floaters and shadowing in the field of vision. High myopia and trauma to the eye are the most important risk factors.

If a retinal tear is diagnosed early, laser treatment can stop it progressing. If diagnosis or treatment is delayed, the tear enlarges and the retinal layer separates from its underlying tissue. Once retinal detachment has occurred, the only treatment is surgery.

What kind of eye problems does diabetes cause?

Diabetes is a systemic disease that causes a number of ocular problems. It accelerates the formation of cataract, can cause refraction (glasses prescription) changes, paralysis of the eye muscles and the resulting double vision.

Most importantly, it causes damage to the retina (the nerve layer of the eye). This condition, called diabetic retinopathy, is characterised by retinal haemorrhages, vascular occlusions, new vessel formation and retinal oedema.

How often should diabetic patients have eye examinations? How is the disease treated?

Patients diagnosed with diabetes whose fundus has not yet shown damage are advised to have an annual eye examination. Patients with established diabetic retinopathy should be followed up every six months.

If the damage has progressed, fundus fluorescein angiography (FFA) and/or optical coherence tomography (OCT) are performed to determine the severity of the diabetic retinopathy. If areas of poor retinal perfusion, new vessel formation or leaking vessels are found, laser treatment is required. In cases where leakage near the macula has become widespread or cystic, intra-ocular drug injection is administered.

In untreated cases, intra-ocular haemorrhages may occur. These patients undergo vitreoretinal surgery during which the blood is cleared. Tractional membranes are also separated, and the laser treatment is completed during surgery.

Treatments for diabetic retinopathy aim to preserve the level of vision present at the time of starting therapy. An improvement in vision is rare. If treatment is neglected, the disease ends in blindness.

What kind of disease is Macular Degeneration (Age-related Macular Degeneration)?

Age-related macular degeneration (AMD) affects approximately one-third of the population over the age of 70. It impairs central vision — especially close reading — and over time causes loss of vision and dark spots in the central field.

Patients initially complain of distorted or wavy vision; in advanced stages vision may decline to the level of counting fingers at a few metres.

Although AMD does not cause complete blindness, vision can drop to the level of legal blindness. Patients can no longer see the point they are looking at — they cannot see the face of a person standing in front of them, but they can see that person’s arms and legs. People with advanced AMD often cannot go out alone. They can usually manage everyday tasks at home, but have to rely on others for some activities. Because they cannot see well, they can no longer read or write.

The disease exists in two forms: dry and wet. The dry form accounts for 80–85% of cases and vision is lost slowly over many years. These patients are advised to take protective antioxidant supplements. In the wet form, haemorrhage and oedema develop at the point of vision, causing a rapid decrease in vision. The patients currently treated in our clinic are those with the wet form of macular degeneration.

Can Macular Degeneration Be Treated?

Until about a decade ago there was very little we could offer these patients. From the early 2000s onward, several treatment methods began to develop. They started with photodynamic therapy (a light-activated drug given intravenously) and progressed to the intra-ocular injections we use today. Recently, new medications that have come to Turkey and that we now have the opportunity to use, together with countless ongoing global studies, mean that the likelihood of blindness from this disease will continue to fall as more effective drugs and methods become available.

The precise cause of AMD remains unknown, but heredity and metabolic disorders are thought to be the most important factors. In the future, examinations carried out at an early age may identify those at risk so that they can be treated — through gene therapy or other means — before the disease becomes manifest.

Who Should Have Regular Eye and Retina Examinations?

• Those with diabetes in themselves or their family,
• Patients with hypertension,
• Those with high cholesterol,
• Those with heart or vascular disease,
• Those with macular degeneration in themselves or their family,
• Those with congenital or acquired vision problems in the family.

What Is Retinopathy of Prematurity (ROP)?

ROP is a disease seen in low birth-weight premature babies that can lead to blindness.

What Are the Risk Factors for ROP?

All babies under 1300 g or born at less than 30 weeks of gestation.
Babies under 1500 g or less than 32 weeks of gestation who require oxygen therapy in intensive care.

Premature babies with recurrent apnoea, sepsis, blood transfusion or exchange transfusion, intracranial haemorrhage, bronchopulmonary dysplasia, respiratory distress syndrome or patent ductus arteriosus, and babies whose mothers had pre-eclampsia or diabetes, are at risk of developing ROP.

How Are ROP Examination and Follow-up Performed?

The ROP examination is performed under topical anaesthesia: the baby’s pupils are dilated and the retinal nerve layer is examined. In premature babies the first ROP examination should be performed 4–6 weeks after birth. Depending on whether the disease is present and on its severity, the examination is then repeated every 1 or 2 weeks until the baby reaches term (the expected birth date).

What Are the Treatment Options for ROP?

The most important step in treating ROP is regular follow-up. Statistically, 80% of cases of ROP regress spontaneously and only about 8% of monitored babies require treatment. Detecting “threshold disease” on time and carrying out urgent (within 3 days) laser treatment is the most important factor in preventing blindness in babies who develop ROP. In cases that are not detected on time and progress despite laser treatment, vitrectomy surgery is performed.

Photodynamic Therapy (PDT)

Photodynamic therapy is used in some patients with age-related macular degeneration, in chronic central serous chorioretinopathy and in polypoidal choroidal vasculopathy.

In photodynamic therapy a light-sensitive chemical is administered intravenously and the target tissue is then exposed to a low-energy light (cold laser) which activates the agent. This destroys the vascular component of the target tissue while sparing the surrounding tissue.

If required, photodynamic therapy can be repeated. If both eyes are affected, your doctor may decide to treat both eyes at the same session.
After treatment, patients are asked to avoid intense light for 48 hours.

You can contact our hospital with any questions about eye health, obtain detailed information about your eye problems and learn about the treatment process.

Prepared by the Editorial Board of Eye Foundation Hospitals.