Retina

The macula is an area of the retina located at the back of the eyeball, which specializes in central vision. Conditions affecting the macula are called maculopathies.

Age-related macular degeneration (AMD)

• It affects people over 50 years old. The risk of suffering it increases with age.
• It consists of a slowly-progressing degenerative process that affects the macula, which is the area specialized in central vision.
• The macula is a small area (5 to 6 mm diameter) of the retina located between the temporal vascular arcades.

Causes:

They have not yet been fully clarified. It has a multi factor etiology including hereditary factors (it is important to know whether your parents or grandparents suffered from this condition) and environmental factors, such as lifestyle (poor nutrition, lack of regular exercise and mostly smoking).

Initial symptoms:

• Blurry vision.
• Inability to see or recognize people’s faces at a distance.
• Difficulty transitioning from bright light to dim light settings.
• Need of greater light to read.
• Straight lines are seen as curvy.

Types of AMD:

• 85%-90%: Dry AMD. It affects both eyes, although it usually progresses in one eye first, then in the other. Therefore, it can go initially unnoticed. It evolves slowly through its final state known as geographic atrophy. It implies the progressive loss of the cells that make up the retinal pigment epithelium, generating areas of lack of central vision (scotomas).
• 10%-15%: Wet AMD. Characterized by the presence of blood vessels invading the retina and leaking fluid or blood into the macula. Initial symptoms include sudden impairment of central vision, metamorphopsia (lines that appear deformed and wavy) and eventually the formation of scars.

AMD Diagnosis:

Ophthalmology annual checks. If AMD is diagnosed, the specialist will determine the checks frequency. It is important to know whether you have a family history of AMD and, if so, to communicate it to your attending ophthalmologist.

Treatment:

• • Dry AMD: The treatment for dry maculopathy is photobiostimulation (VALEDA), which should be repeated every 4-5 months. Vitamin intake is also recommended. Patients should undergo periodic ophthalmology checks every 3 months with optical coherence tomography (OCT). During the checks, a checkered grid called the Amsler grid will be handed over to the patient so that they perform weekly self-checks. If from one week to the other you notice any distortion in the checkered grid that was not present in the previous check, you should coordinate a visit before the date scheduled for control. It is essential to make lifestyle changes, such as quitting cigarettes if you smoke, exercising regularly and including plenty of green leafy vegetables in your normal diet.
  • Wet AMD: there is currently a treatment available intended to “dry” the wet macula. It consists of intravitreal injections of an antiangiogenic substance (inside the eye) performed in the operating room, with topical anesthesia, which purpose is to stop the generation of blood vessels leaking fluid and blood into the macula. It is usually done through 3 monthly applications and the evolution of the patient will determine the frequency of the injections required to achieve the purpose. In some cases, applications can be progressively spaced following a protocol called “Treat and Extent”. In other cases, the “PRN” protocol is followed, which consists in performing injections only when necessary. The model to be followed is determined by the specialist on a case-by-case basis, thereby providing individualized treatment.

It can be idiopathic (of unknown cause) or form incidentally to inflammatory processes, traumas, retinal vascular occlusions and intraocular surgery.

Symptoms
In mild cases it can be asymptomatic. In acute cases, when the macular area is affected, it can experience metamorphopsia (deformations and undulations in straight lines), micropsia (a smaller appearance of what is being watched) and monocular diplopia (double vision in the affected eye). Vision impairment is variable.

Treatment
If the vision is good and the patient is asymptomatic or has mild symptoms, observation and periodic checks are recommended. In cases of acute vision impairment or significant symptoms, the membrane can be removed through surgery.

It is a full-thickness hole formed in the macula, generally related to the separation of the vitreous gel from the macular area. It is also related to trauma. In general, it is unilateral.

Symptoms
Variable según la severidad del cuadro. Muchos casos son asintomáticos, y otros presentan disminución importante de visión central, así como también metamorfopsias (deformación y ondulación de líneas rectas).

Treatment

In mild cases, observation could be an option. More advanced phases require the performance of vitrectomy surgery with the placement of gas within the eye as a tamponade. The gas is usually reabsorbed within 60 days and while it lasts inside the eye, vision will be extremely blurry. As it reabsorbs, the patient will begin to see better. Importantly, during the first weeks while the gas remains in the eye, the patient should look downwards as many hours as possible so that the gas may close the hole area.

It is essential to note that the gas has an expansive effect, so while it remains in the eye, traveling by plane is absolutely inadvisable. In many cases additional procedures are required to achieve full closure of the macular hole, using silicon oil as a tamponade which, after some months, should be removed from the eye.

Diabetic retinopathy is the most common diabetic eye disease. It occurs when there are changes in the blood vessels in the retina. Sometimes, these vessels may swell and leak fluid, or even get blocked completely. In other cases, new abnormal blood vessels grow on the surface of the retina.

The retina is a light-sensitive thin tissue layer covering the back of the eyeball. The rays of light focus on the retina, where they are transmitted to the brain and interpreted as images. The macula is a very small area located in the center of the retina. It is responsible for detailed vision and for allowing us to read, sewing or recognizing a face. The part around the retina, called peripheral retina, is responsible for lateral or peripheral vision.

Generally, diabetic retinopathy affects both eyes. People with diabetic retinopathy often do not realize the changes in their vision during the first stages of the disease. But as it advances, diabetic retinopathy usually causes a vision loss that in many cases is irreversible.

There are two types of diabetic retinopathy:

Proliferative or non-proliferative diabetic retinopathy (NPDR).

Non-proliferative diabetic retinopathy (NPDR) is the earliest stage of diabetic retinopathy. When this condition exists, the deteriorated blood vessels allow the leak of blood fluid into the eye. Occasionally, cholesterol deposits or other blood fats may get into the retina.

NPDR may cause changes in the eyes, including:

• Microaneurysms: small protrusions in the blood vessels of the retina which frequently allow fluid leaks.
• Retina hemorrhages: small blood stains entering in the retina.
• Hard exudates: swelling or thickening of the macula due to fluid leaks from the blood vessels into the retina. The macula does not function properly when it swells. Macular edema is the most common cause of vision loss during diabetes.
• Macular exudates: swelling or thickening of the macula due to fluid leaks from the blood vessels into the retina. The macula does not function properly when it swells. Macular edema is the most common cause of vision loss during diabetes.
• Macular ischemia:the small blood (capillary) vessels get closed or blocked. Your vision turns blurry as the macula does not receive enough blood to function properly.Many people with diabetes have mild NPDR, which usually does not affect vision. However, if your vision is affected, this is the result of a macular edema and a macular ischemia.

Proliferative diabetic retinopathy (PDR)

Proliferative diabetic retinopathy (PDR) occurs mainly when many of the blood vessels in the retina get plugged up, thereby blocking the passage of sufficient blood flow. In an attempt to provide blood to the zone where the original vessels got blocked, the retina responds by creating new blood vessels. This process is called revascularization. Nevertheless, the new blood vessels are also abnormal and do not provide the retina with adequate blood flow. Often, the new vessels are accompanied by scarred tissues that may cause the retina to wrinkle or detach. PDR can cause a more severe vision loss than NPDR as it may affect both central and peripheral vision. PDR affects vision as follows:

• Vitreous hemorrhage:  The new and fragile blood vessels bleed inside the vitreous (the gelatinous substance in the center of the eye), thus preventing the rays of light from getting to the retina. If the hemorrhage is small, you may see some new dark and floating spots. A very large hemorrhage can block the vision and only allow you to see the difference between clear and dark. A vitreous hemorrhage does not per se cause permanent vision loss. Whenever the blood disappears, the vision can go back to its previous state, unless the macula has been damaged.
• Retinal traction detachment: When the tissue of a scar caused by revascularization shrinks, the retina wrinkles and may move from its normal position. These macular wrinkles may distort vision. More serious vision losses may occur if the macula or large areas of the retina get detached.
• Neovascular glaucoma: If a series of vessels in the retina gets closed, a revascularization in the iris (the colored part of the eye) may occur. When this happens, the new blood vessels may block the normal flow of liquid into the eye. Pressure in the eye increases causing a particularly serious condition which damages the optical nerve.

Melanomas are most frequently located in the choroid and melanomas with more benign prognosis are located in the ciliary body. The five-year survival rate for metastatic melanoma of the ciliary or choroidal body is nearly 30%, as compared to 2%-3% for iris melanoma. They are usually asymptomatic, but should be considered as part of the differential diagnosis in unilateral pigment dispersion glaucoma, chronic iritis, endophthalmitis, non-rhegmatogenous retinal detachment or dense hemovitreous (intraocular masquerade syndrome). They can appear with vision alterations, pain and/or sentinel episcleral vessels. Both A-mode and B-mode ultrasound is useful to confirm biomicroscopic and ophthalmological diagnosis. Echography allows us to assess the size, area and height of the injury. Fluorescein angiography is used to demarcate the injury and its vascularization pattern.

To assess extrascleral extension, RNM is more specific than TAC. And while 98% are not extensive to diagnosis, it is recommended that a general basal exploration be conducted with full physical exploration, blood count, liver markers, chest x-ray and abdominal ultrasound, which will be repeated from time to time upon confirmation of the diagnosis. Differential diagnosis between nevus and melanoma is not always that clear, but is of great importance given the risk of metastatic disease. Growth is believed to be the primary risk factor of metastasis in this type of injuries, as it indicates mitotic activity. Therefore, growth risk signs have been looked for which may allow us to foresee it by determining the malignant potential of the injury at an early state.

Enucleation continues to be the therapy of choice for most large melanomas (>15 mm), which invade the optical nerve or cause serious glaucoma. Radiotherapy (brachytherapy/external beam radiation with activated particles) has demonstrated five-year survival rates comparable with enucleation in medium-sized (10-15 mm) and small-sized (less than 10 mm) tumors.

Other possibilities include observation where a differential diagnosis between nevus and melanoma proves difficult; photocoagulation, transpupillary thermotherapy (TTT), surgical resection; exenteration, where there is massive or orbital extrascleral extension, and chemotherapy if there is metastatic disease. Minor procedures include hyperthermia, photodynamic therapy (FDT) and cryosurgery.

Therapeutic management often entails a combination of several techniques, such as iodine-125 brachytherapy, together with TTT.

A vein occlusion is a blockage in a vein that prevents the drainage of blood carried by the artery to the eye, generating bleeding, swelling and loss of blood flow into the retina. It usually occurs in elder people with a history of high blood pressure and atherosclerosis. In other cases, it may occur incidentally to clotting disorders, vasculitis and has also been associated to the use of oral contraceptives. It may affect a vein branch or the central retinal vein resulting in a more severe case.

Symptoms: sudden and painless vision impairment, generally compromising part of the visual field.

Treatment: Depending on the clinical case, there are diverse treatment alternatives including antiangiogenic therapy, laser on the retina and in specific cases of vasculopathic macular edema refractory to prior treatments, the use of extended-release intravitreal corticoids (OZURDEX). To prevent repetition of this type of vascular events, a general clinical check is essential to assess cardiovascular risk factors contributing to the event (blood pressure, atherosclerosis).

It occurs when the vitreous (the gel that fills and shapes the eye) remains stuck to the macula due to traction.

Symptoms
In mild cases it can be asymptomatic. In acute cases, you may experience metamorphopsias (deformations and undulations of straight lines). Vision impairment is variable.

Treatment
In mild cases, where there is good vision and little symptoms, observation may be an option, as in many cases there is spontaneous separation of such traction. In acute cases, where there is vision impairment and significant symptoms, a vitrectomy can be performed; i.e., removing the vitreous gel to release traction on the macula.

The Novartis division of Alcon laboratory has launched JETREA®, a single-dose pharmacological treatment for selected cases of Vitreomacular Traction. Its active ingredient is OCRIPLASMIN, which is administered through an intravitreal injection that dissolves the fibers responsible for the abnormal traction between the vitreous and the macula.