Slit lamp exam: Uses, procedure, results, and other eye exams

The slit lamp exam usually forms part of a comprehensive eye exam. The individual will sit in a chair facing the slit lamp with their chin and forehead resting on a support.

The doctor can use this instrument to observe the eyes in detail and determine whether or not there are any abnormalities. They will be able to discuss the results with the person immediately.

What does a slit lamp exam show?

Doctors use the slit lamp as part of a complete eye exam to get a better look at the structures within a person’s eyes. These include the following:

• Conjunctiva: The conjunctiva is a thin, clear membrane that covers the white part of the eye. It also includes the membranous surface of the inner eyelids.
• Cornea: The cornea is the transparent covering of the iris and pupil. It protects the eye and also helps to send light through the pupil to the retina at the back of the eye.
• Eyelids: The eyelids help to protect the eyeball from debris or injury. Blinking helps to lubricate the eye and prevent it from drying out.
• Iris: The iris is the colored part of the eye. It controls the amount of light going into the eye by constricting and dilating the pupil.
• Pupil: The pupil is the black dot in the middle of the eye. It allows light to enter the eye and travel to the retina.
• Lens: The lens sits behind the iris and focuses the light onto the retina.
• Sclera: The sclera is the white part of the eye. It consists of relatively tough fibrous tissue that helps to provide structure and protection for the rest of the eye.
• Retina: The retina is the eye tissue containing the cells that sense light. These cells link to nerves that eventually join to form the optic nerve.

A doctor will be able to detect a range of conditions by carrying out a slit lamp exam. Among many others, they may observe abnormalities such as:

• cataracts, which is an opacity or cloudiness of the lens
• corneal injury or disease
• damage to the sclera
• a detachment of the retina
• damage to the retina or the blood vessels that supply it
• macular degeneration, an eye disease that destroys the central vision
• disease or swelling of the middle layer of the eye
• diseases of the optic nerve, such as glaucoma
• bleeding in the eye
• presence of a foreign body in the eye

Risks

A slit lamp exam is generally very safe, although the drugs that dilate the pupils come with a few risks. They can increase eye pressure, which causes nausea and eye pain.

Anyone experiencing these symptoms should let a doctor know immediately.

During a fundus exam, the doctor will use an ophthalmoscope to look into the eye.

Some will use a direct ophthalmoscope, which is a small, handheld instrument with a light on it. However, most doctors will use an indirect ophthalmoscope as they can wear this on their head, and it gives them a wider field of vision for the examination.

They will ask the patient to stare off into the distance while they use the device to examine the inner structures of the eye.

Gonioscopy

For this procedure, the doctor will first administer numbing eye drops. The individual will sit with their head resting in the slit lamp microscope, and the doctor will place a special contact lens directly onto the eyeball.

The test should reveal any signs of increased eye pressure, which may indicate glaucoma.

Outlook

A slit lamp eye exam is a straightforward and painless procedure that doctors use to look closely at the inner structures of a person’s eye.

A doctor will decide whether or not a person needs the test, and for what purpose.

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