Learn How to Use a Slit Lamp Like an Experienced Pro

Whether you are an experienced optometrist or are just getting started in optometry school, it's important to continually review and learn new techniques about how to use a slit lamp. With the introduction of new and more robust technology, it's best to ensure you're getting the most from each slit lamp exam.

In either case, you will be unable to to treat or diagnose anyone's problems if you fail to have an in depth understanding of how to use a slit lamp. Continue reading to learn more about how to use a slit lamp and a few best practices for conducting slit lamp exams.

Basic Approach for How to Use a Slit Lamp

When learning how to use a slit lamp, it's important to first take a second to first observe the patient. After the patient is under the microscope, macropathology such as periorbital neoplasms, iris heterochromia, and heterotopias can easily be missed.  

One of the hardest parts of learning how to use a slit lamp is keeping illumination techniques in line. In the very beginning, it can be difficult to understand what each lighting setting is used for. It can also be difficult to remember how to achieve the desired type of illumination. However, hard work and practice will render experience and positive results.

How to Use a Slit Lamp - Lighting Techniques

When it comes to lighting techniques, it's imperative to understand your patient is on the other end of the scope. While amping up the intensity of the light may improve your ability to see, it will undoubtedly be uncomfortable for you patient.

However, if you must increase the intensity of the light, let your patient know and keep it as brief as possible. The general rule of thumb is to lower the beam width and/or height as you increase the brightness of the slit lamp. Some of the most useful and common lighting techniques you may employ are:

Diffuse Illumination

Diffuse illumination explains when you use the open beam at 45°. This particular lighting technique is most effective for surveys of the lashes, lids, eye, surface vessels, sclera, caruncle, and media opacities.

Sclerotic Scatter

The sclerotic scatter uses a wide, tal beam aimed directly at the limbus. This technique scatters light throughout the cornea to display the patient's general pattern of opacities.


In general, there are two common types of retroillumination lighting techniques you may use:

  • Red Reflex Test involves a shorter beam of light being directed through the patient's pupil. The light is reflected off the retina to display iris illumination and reveal lens opacities.
  • Iris Retroillumination involves light being reflected anteriorly off the deeper iris to allow an intuitive study of the guttata and corneal opacities.

How to Use a Slit Lamp - Light Filters

The neutral density is a gray, colorless filter designed to the minimize the illumination for patients with photosensitivity.

  • The red free filters obscures red light to bolster the view of defects in the retinal nerve fiber layer, while helping differentiate pigmented lesions from hemorrhages and blood vessels.  
  • The cobalt blue filters are used to assess tear breakup time, tear lake, corneal lesions, the fitting of contact lenses, and defects. This filter is also used in Seidel testing.
  • The yellow barrier filter bolsters contrast when using the cobalt blue filter and fluorescein.

Tips Optimizing the Slit Lamp Exam

The slit lamp exam utilizes a tool that provides a three-dimensional, magnified view of different parts of the eye. This instrument includes a high-intensity light source focused to shine a thin sheet of light into the eye. It's used with a biomicroscope.

The slit lamp facilitates the exam of the posterior segment and anterior segment of the human eye. During the exam, you will use the slit lamp to examine different parts of the eye, including the cornea, eyelid, conjunctiva, sclera, lens, and the iris. The slit lamp exam also allows you to view the vitreous gel, which fills the large space in the middle of the eye.

A camera can be attached to the slit lamp to take images of the different parts of the eye. This essential tool allows the physician to make anatomical diagnoses for a long list of eye conditions. While everyone may have a different methodology for using a slit lamp, adding the following tips to your routine will ensure you get the most out of every exam:  

  1. Clean up your slit lamp to improve your view.
  2. Adjust the oculars because daily handling can displace the interpupillary distance.
  3. Follow the anatomy by starting with a low magnification and working your way up.
  4. Have a firm understanding on the different illuminations.
  5. Enhance your view with the use of ophthalmic dyes to bolster diagnostic evaluations.
  6. Understand and use filters.
  7. Consider using a continuous magnification drum due to the smoother transition without image loss.
  8. Start the slit lamp exam with the lowest illumination and work your way up.
  9. Adjust the illumination arm to gain different illumination angles to assess different tissues.
  10. Use a graticule or measuring eyepiece to improve measurements.

Contact Keeler Ophthalmic Instruments

At Keeler Ophthalmic Instruments, we offer a long list of cutting edge slit lamps and other vital pieces of equipment. We pride ourselves in offering state-of-the-art equipment with a hyper focus on magnification equipment. Contact Keeler Ophthalmic Instruments today.