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Macular Hole
MACULAR HOLE.
A macular hole occurs when the vitreous gel exerts traction in the area of central vision, the macula. The pulling of the gel on the center of the retina results in the formation of an opening or hole in the central vision. Liquefied gel or fluid may enter this opening and collect under the retina, forming a cuff of fluid around the macular hole. Visual symptoms are caused by the missing retinal tissue in the center of the hole leading to a blind spot, as well as the cuff of fluid which creates distortion and waviness.
Most macular holes present with an opening in the central retina surrounded by a cuff of fluid under the retina. At this stage, patients typically complain of blurred central vision with an associated blind spot and distortion. The degree of visual loss, size of the blind spot, and level of distortion are often related to the duration of the macular hole. Sometimes, the duration of symptoms may be uncertain, as patients can often compensate with their unaffected, better-seeing eye.
Eventually, patients often note a difficulty in depth perception when one eye is affected, and report problems with reading and performing fine motor tasks with that eye.
Diabetic Retinopathy
Diabetic retinopathy is the most common cause of blindness in individuals between 20 and 74 years old. Elevated blood glucose for prolonged periods of time causes damage to the retinal blood vessels (along with the kidneys and nerves). Such damage to the blood supply of the retina can result in abnormal bleeding, swelling of the retina, poor blood flow to the retina, and/or scarring of the retina.
Diabetic retinopathy is subdivided into two forms: non-proliferative diabetic retinopathy (NPDR) and a more severe form, proliferative diabetic retinopathy (PDR).
NPDR starts with damage to the retinal blood vessels from prolonged elevation of blood glucose. The blood vessels develop tiny weak areas called microaneurysms. Over time, these can rupture and leak. This can result in retinal bleeding, or hemorrhage. Fluid from the blood stream can also leak into the retina and cause swelling, a condition called macular edema. Fats and proteins from the blood stream may leak into the retina as well, and are referred to as hard exudates. Macular edema tends to cause central blurring of vision and/or distortion. Over time, poor blood supply can result in death of nerve cells responsible for fine vision (a process called macular ischemia); this can lead to a permanent central blind spot with corresponding untreatable decreased central vision.
After prolonged poor blood flow, the retina produces substances that promote the growth of new abnormal blood vessels (a process called retinal neovascularization). Retinal neovascularization marks the shift from non-proliferative to proliferative diabetic retinopathy (PDR) and is a very serious condition. This development of new blood vessels may appear logical, as the old, original blood vessels are often permanently damaged and poorly functioning. However, the retinal neovascularization process tends to do more harm than good over the long-term. The new blood vessels are fragile and tend to bleed into the vitreous cavity, a condition termed vitreous hemorrhage. A vitreous hemorrhage can cause significant floaters in the vision (from floating blood cells) and may cause transient near-total blindness if the hemorrhage is particularly dense. The new blood vessels may also grow along the surface of the retina, scar, and contract; this can pull on the retina and cause a very serious condition called traction retinal detachment.
he most important aspect in the treatment of diabetic retinopathy is long-term control of blood glucose. Patients should monitor their glucose daily and follow their hemoglobin A1c level with their diabetes doctor. They should also control any coexisting conditions that can worsen retinopathy; these include hypertension and elevated cholesterol/lipids.
Retinal intervention is generally aimed toward preventing visual loss from macular edema and complications of proliferative diabetic retinopathy.
Macular Edema:
Macular edema is frequently treated with laser. Research studies have shown that laser treatment results in 1 the rate of significant visual loss when compared to those who did not receive laser. Unfortunately, most patients treated with laser do not gain significant vision. In an attempt to improve visual outcomes, retinal specialists have been injecting experimental medications into the vitreous cavity to target macular edema (see sections on New Medications & Intravitreal Injection). These medications are currently offered on an off-label basis to patients who may be good candidates after an extensive discussion of risks and potential benefits. Currently, these medications include Kenalog (a corticosteroid) and Avastin (an anti-neovascular agent). In certain cases, vitrectomy surgery may be recommended to treat specific causes of macular edema.
Proliferative Diabetic Retinopathy:
Complications of proliferative diabetic retinopathy result from retinal neovascularization, so this process is the target of most treatments. Untreated retinal neovascularization may result in vitreous hemorrhage and/or traction retinal detachment. The main procedure for attempting to control retinal neovascularization involves the use of laser; this treatment is called panretinal photocoagulation. The peripheral retina is treated extensively with laser to target abnormal blood vessels and prevent complications. Research has shown that an individual with specific characteristics warranting laser will have 1 the risk of significant visual loss compared to those not undergoing laser treatment. Unfortunately, individuals do not typically gain vision after this type of laser treatment.
Vitreous Hemorrhage:
When a vitreous hemorrhage develops, the patient usually experience significant floaters or diffuse blurring (blindness) in one eye. The hemorrhage will often clear on its own over several weeks, so immediate intervention is often unnecessary. However, there are often times when the hemorrhage is slow to clear or new hemorrhages continue to occur. In these cases, vitrectomy surgery is often recommended (see section on Treatment/Vitrectomy). In this procedure, the vitreous gel is removed along with the blood that fills the vitreous cavity. At the time of surgery, laser is usually applied to treat the retinal neovascularization that is suspected to be the source of bleeding.
Traction Retinal Detachment:
With traction retinal detachment vitrectomy surgery is often performed to relieve the traction on the retinal surface caused by scar tissue and allow the retina to lay flat on the back wall of the eye The procedure involves peeling of the scar tissue, or membranes, from the retinal surface using microscopic instruments such as forceps, scissors, and pics.