Photocoagulation is a procedure in which light is used to coagulate or congeal hemorrhages.
Photocoagulation is used routinely in ophthalmological therapy and as an alternative to surgery. Light was first used in the 1950s to coagulate retinal detachments. The procedure used a German device that produced a powerful beam of light from a xenon arc.
In the 1960s lasers were introduced and became the instrument of choice for photocoagulation because they generate less heat and can be focused more precisely. The low energy, finely concentrated light of the laser is directed into the eye where it is absorbed by the tissue. The energy converts to heat, which forms a burn. The burn develops into scar tissue, which congeals the hemorrhage.
Photocoagulation is used to treat diabetic retinopathy. An argon laser is directed into the eye where the light is absorbed into the pigmented layer of the retina.
The surgeon makes several “burns” around each leaking vessel of the retina. The resulting scar tissue stops the leakage. Unhealthy tissue that is generating neovascularization (new, weak vessel growth) is treated with the laser to destroy it and to prevent the cycle of new growth.
In much the same manner, photocoagulation is used to treat subretinal neovascularization, a complication of age-related maculopathy. A break in the pigment epithelial layer beneath the retina causes the underlying vessels to bleed into the retina and causes scarring which destroys vision in the macula.
This treatment utilizes a laser, which is absorbed only in the deepest layers of the retina where such damage occurs. The light passes through the upper, unaffected layers and treats only the targeted areas below.
Photocoagulation may be used in some instances to treat glaucoma. A laser may be used to create a series of burns that develop into scars and form openings in the meshwork of drainage channels that allow fluid to flow more easily from the eye. Photocoagulation is generally a painless procedure and usually performed without anesthesia.
The patient sits in front of a slit lamp or biomicroscope in a dimmed room. Topical anesthetic drops, dilating drops, or a contact lens may be placed in the eye. The surgeon administers from fifty to several hundred rapid bursts of energy to the affected areas. The patient may see flashing lights and may experience slight discomfort or brief, painful moments. The procedure may last from five to thirty minutes, and the patient is usually able to walk or drive home afterward. Follow-up treatments may be necessary.
Although photocoagulation may improve vision in some cases, it is not always a cure. Frequently, it cannot restore lost vision and may only stop or impede the progression of a disease or disorder.
Just as in focal laser treatment, scatter photocoagulation is performed with a slit lamp microscope, using a contact lens to stabilize the eye and to facilitate the surgery.
After placement of the lens, between 1,000 and 2,000 burns are made, usually placed in the periphery of the retina. This operation is less delicate than focal laser phtocoagulation and takes about thirty minutes to an hour. The majority of patients do not feel any pain, only mild discomfort akin to a sharp sensation.
Usually this is felt if burns are placed close to a nerve. If this discomfort is felt, the ophthalmologist should be told so that another area farther away from the nerves can be treated. Occasionally, patients feel more pain than they can tolerate. In these cases, the ophthalmologist will inject a numbing substance behind the eyes. This injection is called a retrobulbar block, which is generally safe but can cause complications.