Slit Lamp Exam: Uses, Procedure, and Advantages

What is a Slit Lamp Exam?

A slit-lamp exam is a procedure performed in a standard eye test that assists optometrists in examining all parts of the eye and further inside the eye using a machine. Before a slit-lamp examination, the optometrist may need to dilate a patient's pupils to look closer at the back of the eye.  A slit-lamp eye exam is performed using a microscope with a bright light and, according to the American Academy of Ophthalmology, is used to produce three-dimensional measurements and visualisation of the eye. A slit-lamp examination is used to assess overall eye health and observe the eyes for eye diseases and abnormalities such as cataracts, glaucoma and macular degeneration. According to HealthLink BC, a slit lamp exam typically takes between 5 and 10 minutes.

How is a Slit Lamp Exam Performed?

The steps to perform a slit lamp exam, as described by the American Academy of Ophthalmology, includes positioning the patient, positioning the operator, focusing, illumination and magnification. These general steps and their definitions are listed below.

• Positioning the patient: The first step in a slit lamp exam is to ensure the patient is positioned properly. This involves making sure the patient is appropriately situated with their forehead and chin resting on the machine and that the surfaces have been thoroughly sanitised. 
• Positioning the operator: The positioning of the operator involves having their dominant hand on the carriage and joysticks, with the other hand on the slit width adjustment knob. It is standard practice to examine the patient’s right eye first, then the left eye. 
• Focusing: In the focusing stage, a light beam will be aimed at a point on the patient’s skin for coarse focusing and the operator will then slowly slide the carriage forward toward the patient. 
• Illumination: Next, the eye care professional will adjust the intensity of the beam of light to ensure there is enough light to examine the patient but not too bright as to make them uncomfortable. Both the beam width and height can be adjusted to make measurements during the exam.
• Magnification: Magnification is controlled by a knob on the slit lamp machine. Lower power magnification is used for general examination and high power for the examination of fine structures of the eye.

What Conditions and Eye Disorders Can a Slit Lamp Exam Diagnose?

A slit lamp exam is a key part in the diagnosis of many eye conditions and disorders. The eye conditions that an optometrist can check for in a slit lamp exam include cataracts, glaucoma, corneal abrasions and dry eyes. These conditions and their definitions are listed below.

• Cataracts: Cataracts are a clumping of protein in the eye’s lens which causes the lens to become cloudy instead of clear. In a slit lamp exam, the optometrist will look at the patient’s lens in order to diagnose cataracts. 
• Glaucoma: Glaucoma is a term for a group of eye conditions or diseases in which damage to the optic nerve causes vision loss. A slit lamp exam gives an optometrist a detailed view of the optic nerve to diagnose glaucoma. 
• Corneal abrasion: A corneal abrasion is a type of eye injury where the cornea sustains trauma which may be a scratch or tear. A slit lamp exam can allow the optometrist to check the eye for any damage to the cornea. 
• Dry eyes: Dry eye is a common eye condition that can be described as a lack of tears produced or an inadequate quality of tears in the eyes. Examination of the cornea in a slit lamp exam can be used to identify dry eyes. 

What are the Advantages of a Slit Lamp Examination in Eye Healthcare?

The advantages of a slit lamp exam in eye care include detecting eye diseases and examining the overall health of the patient’s eye. According to Medical News Today, a slit lamp exam can detect eye conditions and abnormalities such as cataracts, retinal detachment, macular degeneration, glaucoma, bleeding in the eye and damage to the sclera.