Skip to main content
  • Slit Lamp 101: 3 Tips to See Clearly


    If you are a medical student, a new resident or an early-career ophthalmologist, this review of the slit lamp is for you.

    If you are a seasoned ophthalmologist, a refresher never hurts anyone. The slit lamp is an essential tool that allows eye doctors to directly visualize pathology. We make so many of our diagnosis just from pure physical exam.

    Know Your Slit Lamp

    Every slit lamp is different, but here are the key parts.

    Important components of a slit lamp
    Important components of a slit lamp.
    • Light source. This is where the light bulb is located to create the slit lamp light.
    • Vertical light control. This can be used to measure structures and can rotate in different directions. Measure the height and width of a specific lesion like a corneal ulcer.
      • Cobalt blue filter. Learn to switch from white light to blue light. This is different on each slit lamp. The blue filter is helpful when you apply fluorescein to the eye to look at the cornea.
    • Spend time adjusting your oculars. Match the oculars to your pupillary distance, and make sure the scope is “zeroed” out if you’re wearing your own correction. If the right eyepiece is on a -3 and the left is on a 0, you are not going to have a fun time.
    • Horizontal light control. For corneas, I tend to prefer a very thin beam. You can make your slit-lamp beam wider or narrower here.
    • Articulating arm. Rotate your slit lamp on axis.
    • Thumb wheel/decoupler. Decouple where the light is in relation to the ocular focus.
    • Joystick. Think of it as the fine focus of your microscope. Most slit-lamp joysticks twist clockwise and counterclockwise and move horizontally right and left and up and down. Always keep your hand on the joystick. To see something deeper in the eye, move the slit lamp toward the patient. To see something more anterior, move it away from the patient.
    • Lastly, the slit-lamp lock. This locks the slit lamp. Don’t forget about it (both locking and unlocking).
    Patient positioning
    Always start with ensuring good patient positioning.

    Focus on Your Ergonomics

    Many ophthalmologists have bad neck issues because we often force our bodies into bad positions. Here are some things I do to avoid strain:

    First, I get the patient into the chair. I slightly raise the patient’s chair so I don’t bump my wheels into the foot rest.

    Second, if the patient has a short torso or large body habitus, I have the patient slide up in the chair. The patient can drop the knees and allow me to get the slit lamp closer.

    You need to ensure three things:

    1. The patient’s eye is at the level of the back line.
    2. The patient’s chin is on the rest.
    3. The patient’s forehead touches the strap.

    Third, focus on you. You are the most important part of this equation. Why? Because you will be doing this exam thousands of times in your career. If the patient has to be uncomfortable for less than a minute, yes, that’s not ideal. However, it’s better than you having to strain your neck 50 to 60 times a day, five days a week, 52 weeks a year, for 40 years.

    Here are my essential ergonomics tips:

    Good vs. bad posture
    Always check your ergonomics. Many eyecare professionals experience neck pain.
    • Focus on sitting up right — no
    • Keep your neck up and shoulders

    Be Systematic

    If you start jumping around, you will miss things. I always follow the flow of the standard clinic note. Meaning, I always check the following:

    • External. Eyelids, eyelashes, meibomian glands, palpebral conjunctiva, upper lid and then lower lid.
    • Conjunctiva and sclera. Ask the patient to look in all directions so you can examine all parts of the anterior globe. Don’t forget to flip the eyelids to look for papillae.
    • Cornea. Start with diffuse light, and then bring the light directly in front of the eye for a red reflex. This will highlight irregularities in the cornea and lens and will show transillumination defects in the iris. Now, narrow your beam. I like rotating my slit lamp about 45 degrees away. This allows you to look at a slice of the cornea. Examine the epithelium, then the stroma and then the endothelium.
    • Anterior chamber (AC). Look for cell/flare. First, focus on the iris. Next, center your slit lamp, focusing right over the pupil, and then move toward you. This will move the focus of the slit lamp to be more anterior so you can look directly at the anterior chamber. Reduce the size of your beam by 1 mm and use increased magnification. I also recommend turning the room lights down. Lastly, ensure that the AC is deep — if shallow, don’t apply dilating drops.
    • Iris. Look for neovascularization and nevi.
    • Lens. Repeat the red reflex if necessary. Look at the anterior lens, posterior lens and nucleus.
    • Anterior vitreous. In patients with floaters, look for pigment in the vitreous, which is a sign of retinal detachments/tears (Schafer’s sign).

    Phew, that was all for one eye. I always do the RIGHT eye first, and then I move to the LEFT eye. Be methodical.

    Best of luck with your slit-lamp adventures.


    Jeffrey M. Tran, MDJeffrey M. Tran, MD, is a comprehensive ophthalmologist in Atlanta and joined the Academy in 2017. He completed his internship at Emory University School of Medicine and his residency at Baylor College of Medicine in Houston.