Slit lamp: examination of the eye

The examination with the slit lamp (also slit lamp microscope) is one of the most important diagnostic procedures in ophthalmology. The slit lamp produces a slit-shaped, bundled beam of light that ophthalmologists and opticians can use to illuminate the various transparent tissue layers of the eye and view them through a microscope.

Unlike ophthalmoscopy, which is used to examine the back of the eye, the slit lamp microscope can also be used to examine the front and middle sections of the eye. This will reveal changes in different parts of the eye, such as:

• conjunctiva
• cornea
• dermis
• lens
• Chamber angle (where the cornea and iris meet)
• iris
• vitreous
• tear film

When is a slit lamp examination performed?

A slit lamp can be used to detect various eye diseases. Among other things, the slit lamp is used when there is a suspicion of:

• injuries to the cornea
• Clouding of the lens of the eye ( cataracts )
• conjunctivitis
• malformations of the eye

The slit lamp is also used as an examination device to check that contact lenses are correctly seated.

The slit lamp is often combined with other devices.

In combination with other tools, the slit lamp microscope has even more application areas. By holding an additional magnifying glass (contact glass) in front of you, ophthalmologists can also examine the fundus of the eye using the slit lamp microscope, for example. Then the retina and the optic nerve head can also be examined. When measuring intraocular pressure, also known as tonometry, the measuring device, the tonometer, is placed on the eye during a slit lamp examination.

How does the slit lamp examination work?

For the examination, the forehead and chin are leaned against a support so that the head is kept very still. Slight head movements can also disturb the examination. The doctor sitting opposite looks you in the eye through the slit lamp. Now the desired degree of enlargement can be set. The outer sections of the eye and lids are viewed with a magnification of around six times, higher magnifications of 16 to 40 times are used when viewing the other areas of the eye such as the cornea, lens and vitreous humor.

During the examination, the light beam is moved slowly over the eye. The shape and diameter of the light gap can be adjusted according to requirements. The color of the light beam used to illuminate the eye can also be changed using color filters that can be pivoted into the beam path.

Local anesthesia for eye pressure examination

For a slit lamp examination of the anterior sections of the eye, no special preparations usually have to be made. However, if the back of the eye is to be examined, for example the back of the eye, eye drops are administered to dilate the pupil.

Since the effect usually lasts longer, people cannot drive on the road for around three hours after the examination. The dilation of the pupils impairs sharp vision. Reading or working on the screen is also impossible for the first time after the examination.

If the intraocular pressure is also to be determined, the cornea is usually anesthetized locally before the examination since the measuring device is placed directly on it. The anesthetic prevents involuntary eyelid closure when touched by the tonometer.

Slit lamp: risks and side effects

The slit lamp examination is a relatively simple, painless and largely risk-free examination method. Only the drugs, some of which are used for the examination, can in some cases cause side effects in patients. Above all, local anesthetics should be mentioned here, which are used in the slit lamp examination in combination with tonometry. Among other things, they can cause itching or burning in the eyes , as well as increased tear flow and reddened conjunctiva. In rare cases, allergic reactions can also occur

What is a slit lamp? A slit lamp (also slit lamp microscope) is one of the most important diagnostic tools in ophthalmology. It is used to examine the front and middle sections of the eye. The slit lamp can be used to detect defects in the cornea, conjunctiva or vitreous body.

Is the slit lamp examination painful? The slit lamp examination is usually not painful. In some cases, a local anesthetic is put into the eye to prevent pain and blinking during the exam.