Retinal detachment is movement of the transparent sensory part of the retinaaway from the outer pigmented layer of the retina. In other words, the portion of the retina pulls away from the outer wall of the eyeball.
There are three layers to the eyeball: The outermost layer is the tough, white sclera; the sclera is lined by the choroid, a thin membrane that supplies nutrients to part of the retina; and the innermost layer is the retina itself--the light-sensitive membrane that receives images through the pupil and transmits them to the brain. The retina is also made up of several layers. One layer contains the photoreceptors--the rods and cones--that send the visual message to the brain. Between this photoreceptor layer (also called the sensorylayer) and the choroid is the pigmented epithelium.
Filling the inner space of the eyeball itself is the vitreous, a clear gel-like substance, which is in contact with the entire retina.
A retinal detachment occurs between the two outermost layers of the retina--the photoreceptor layer and the pigmented epithelium. Because the choroid supplies the photoreceptors with nutrients, retinal detachment can basically starve the photoreceptors. If a detachment is not repaired within 24-72 hours, permanent vision damage may occur.
Several conditions may cause retinal detachment:
- Scarring or shrinkageof the vitreous can pull the retina inward.
- Small tears in the retina allow liquid to seep behind it, forcing it forward.
- Injury to theeye can simply knock the retina loose.
- Bleeding behind the retina,most often due to diabetic retinopathy or injury, can force it forward.
- Retinal detachment may be spontaneous (without apparent cause). This occurs more often in the elderly or those with myopia (nearsightedness).
- Cataract surgery causes retinal detachment 2% of the time.
Retinal detachment will cause a sudden defect in vision. It may look as if acurtain or shadow has just descended before the eye. If most of the retina isdetached, there may be only a small hole of vision remaining. If just a partof the retina is involved, there will be a blind spot that may not even be noticed. It is often associated with floaters--little dark spots that float across the eye and can be mistaken for flies in the room. There may alsobe flashes of light. Anyone experiencing a sudden onset of flashes and/or floaters should contact their eye doctor immediately, as this may signala detachment.
If the eye is clear--that is, if there is no clouding of the liquids inside the eye--the detachment can be seen by the ophthalmologist by looking into theeye with a hand-held instrument called an ophthalmoscope. Other lenses may also be used to examine the back of the eye. In binocular indirect ophthalmoscopy, the physician dilates the patient's pupil with eye drops and then examines the back of the eyes with a hand-held lens. In addition, to evaluate the blood vessels in the retina, a fluorescent dye (fluorescein) may be injected into a vein and photographed with ultraviolet light as it passes through the retina. Further studies may include computed tomography scan (CT scan), magnetic resonance imaging (MRI), or ultrasound study.
Reattaching the retina to the inner surface of the eye requires making a scarthat will hold it in place and then bringing the retina close to the scarredarea. The scar can be made from the outside, through the sclera, using either a laser or a freezing cold probe (cryopexy). Bringing the retina close to the scar can be done in two ways. In one method, a tiny belt tightened aroundthe eyeball will bring the sclera in until it reaches the retina. This procedure is called scleral buckling and may be done under general anesthesia. Using this procedure permits the repair of retinal detachments without entering the eyeball. In the other method, air or gas must be pumped into the eye, forcing the retina outward against the sclera and its scar. This is called pneumatic retinopexy and can generally be done under local anesthesia.
If these methods fail, and especially if there is disease in the vitreous, the vitreous may have to be removed in a procedure called vitrectomy. This canbe done through tiny holes in the eye, through which equally tiny instrumentsare placed to suck out the vitreous and replace it with saline, a salt walter solution. The procedure must maintain pressure inside the eye so that the eye does not collapse. Retinal reattachment has an 80-90% success rate.
In diseases such as diabetes mellitus, which have a high incidence of retinaldisease, routine eye examinations can detect early changes. Early treatmentcan prevent progression to detachment and blindness from other events like hemorrhage. The most common problem is weakness of blood vessels that causes them to break down and bleed. When enough vessels have been damaged, new vessels grow to replace them. These new vessels may grow into the vitreous, producing blind spots and scarring. The scarring can in turn pull the retina loose.Other diseases can cause the tiny holes and tears in the retina through whichfluid can leak. Preventive treatment uses a laser to cauterize (seal with heat) the blood vessels so that they do not bleed, and holes so they do not leak.
Good control of diabetes can help prevent diabetic eye disease. Blood pressure control can prevent hypertension from damaging the retinal blood vessels. Eye protection can prevent direct injury to the eyes. Regular eye exams can detect changes that the patient may not be aware of. This is important for patients with high myopia who may be more prone to detachment.