Eye disease - Retinal detachment (2 of 3)

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Eye disease - Retinal detachment (2 of 3):

What are retinal detachment causes and risk factors?

Studies have shown that the incidence of retinal detachments caused by tears in the retina is fairly low, affecting approximately one in 10,000 people each year. Many retinal tears do not progress to retinal detachment. Nevertheless, many risk factors for developing retinal detachments are recognized, including certain diseases of the eyes (discussed below), cataract surgery, and trauma to the eye. Retinal detachments can occur at any age but are most common in adults 40 years and older who are highly nearsighted (myopic) and in older people following cataractsurgery.

Which diseases of the eyes predispose to the development of a retinal detachment?

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• Lattice degeneration of the retina is a type of thinning of the outside edges of the retina, which occurs in 7% to 10% of the general population. The lattice degeneration, so-called because the thinned retina resembles the crisscross pattern of a lattice, often contains small holes. Lattice degeneration is more common in people withnearsightedness (myopia). This tendency to lattice degeneration occurs because myopic eyes are larger than normal eyes and, therefore, the peripheral retina is stretched more thinly. Fortunately, only about 1% of patients with lattice degeneration go on to develop a retinal detachment.
• High myopia (greater than 5 or 6 diopters of nearsightedness) increases the risk of a retinal detachment. In fact, the risk increases to 2.4% as compared to a 0.06% risk for a normal eye at 60 years of age. (Diopters are units of measurement that indicate the power of the lens to focus rays of light.) Cataract surgery or other operations of the eye can further increase this risk in those with high myopia.
• People taking certain kinds of eyedrops have an increased risk of developing a retinal detachment. Pilocarpine(Salagen), which for many years was a mainstay of therapy for glaucoma, has long been associated with retinal detachment. Moreover, by constricting the pupil, pilocarpine makes the diagnostic exam of the peripheral retina more difficult, possibly leading to a delay in the diagnosis.
• Individuals with chronic inflammation of the eye (uveitis) are at increased risk of developing retinal detachment.

How does cataract surgery lead to a retinal detachment?

Cataract surgery, especially, if the operation has complications involving the vitreous, increases the risk of a retinal detachment. Cataracts create a cloudiness (opacity) within the lens. In cataract surgery today, the goal is to leave much of the capsule of the natural lens in place. Phacoemulsification, the most common procedure, utilizes a very high speed ultrasonic instrument to break up and suck out the clouded lens material inside the capsule. The new intraocular lens (IOL) is then placed within the capsule. The IOL and intact capsule help to support the vitreous gel which fills the back of the eye. Movement of the vitreous gel is a key factor in retinal detachments because the vitreous movement can place traction on the retina and lead to a hole or tear which can be the start of a detachment. Although cataract surgery does increase the chance of retinal detachment, the risk is low, that is less than 2 % over 20 years; and the benefits of cataract surgery ordinarily far outweigh the risk of retinal detachment.

What other factors are associated with a retinal detachment?

• Blunt trauma, as from a tennis ball or fist, or a penetrating injury by a sharp object to the eye can lead to a retinal detachment.
• A family history of a detached retina that is non-traumatic in nature seems to indicate a genetic (inherited) tendency for developing retinal detachments.
• In a few patients with a non-traumatic retinal detachment of one eye, a detachment subsequently occurs in the other eye. Accordingly, the second eye of a patient with a retinal detachment must be examined thoroughly and followed closely, both by the patient and the ophthalmologist.
• Diabetes can lead to a type of retinal detachment that is caused by pulling on the retina (traction) alone, without a tear. Because of abnormal blood vessels and scar tissue on the retinal surface in some people withdiabetes, the retina can be lifted off (detached) from the back of the eye. In addition, the blood vessels may bleed into the vitreous gel. This detachment may involve either the periphery or central area of the retina.

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