Tinted IOLs protect eyes from harmful visible light
January 30, 2009
Intraocular lenses (IOLs), also called lens implants, are used to replace the eye's natural lens in cataract surgery or refractive lens exchange surgery.
A new study from Japan shows that yellow-tinted IOLs can protect the eye (specifically, the retina) from harmful effects from certain wavelengths of visible light.
Visible light and eye damage
It's generally known that ultraviolet (UV) rays from the sun can be damaging to the eye. UV rays are invisible radiation with shorter wavelengths than visible light. To protect the eye from the sun's harmful UV rays, most IOLs have built-in UV protection.
But recent research suggests certain visible light rays also can damage the retina, which is the inner lining of the back of the eye where light energy is converted into electrical impulses to create visual images. These potentially harmful visible rays are called high-energy visible (HEV) light.
Both UV rays and HEV light can damage retinal tissue through a process called "photo-oxidation." This is the chemical alteration of a tissue caused by exposure to light. A common example of oxidation is the rusting of metal.
(Though these two types of oxidative effects are different, the end result of photo-oxidation of eye tissues and environmental oxidation of metal is similar — a substance is chemically altered and thereby damaged.)
Recent research suggests photo-oxidation of retinal tissue may be associated with a serious eye problem called macular degeneration.
IOL study - Design and methods
In a study conducted in Tochigi, Japan and published in the Japanese Journal of Ophthalmology, researchers compared the light-blocking and photoprotective effects of clear and yellow-tinted IOLs.
They shielded human retinal pigment epithelium (RPE) cells with clear IOLs and yellow-tinted IOLs and then exposed the cells to HEV light for periods up to 48 hours. The RPE cells were then examined and chemical markers for photo-oxidation were measured.
Results: Tinted IOLs provide superior protection
The researchers found that the tinted IOLs provided greater protection from photo-oxidative effects than clear IOLs. All IOLs in the study blocked UV light, but the yellow-tinted IOLs provided superior protection from the effects of HEV light.
The researchers concluded that their findings "suggest that tinted IOLs effectively inhibit tissue damage from visible light."