The slit lamp is the core instrument of ophthalmology, and you want to be able to quickly master its use in the first month of your residency. We’ve collected the most high yield tips to get you examining like a pro. These are the hard things that all beginners struggle with.
Tip 1: Positioning
- Clean the chinrest, top strap, and handles. These are the parts that patients touch. They will be much more cooperative with your exam. Nobody want’s to put their forehead on a top strap where they see another person’s makeup or dandruff clinging to the plastic!
- I always tell the patient: “Grab these handles like you are riding a motorcycle.” This keeps the slit lamp table super stable and safe for when you are applanating, removing sutures, etc.
- Get your patient positioned correctly: chin in the cup, forehead against the top strap.
- Line the patient’s eyes up with the markings on the side of the patient stabilization frame. This is crucial. Otherwise, you’ll be moving patients around after both of you are already settled.
- Lastly, move the slit lamp table up or down, or the patient’s chair up or down to get the patient’s height correct.
- All of these steps should take you less than 15 seconds when you get fast. These will set you up for success even if you need to do a 15 minute exam. It’s crucial that the patient is comfortable. They are much more likely to be able to keep their eyes open, look in the directions you want them to look, and stay still!
- Get yourself positioned comfortably. I can’t tell you how many residents we see ignore personal ergonomics. You will regret it later when poor habits lead to neck strain, poor exams, and fatigue. We’ve seen many folks who, by the time of fellowship, have neuropathies and back pain.
- Get your chair at the correct height to sit comfortably. Never duck your head, never tilt your head, never use the slit lamp while standing.
- This should take you another 10 seconds. You are now ready to start the exam.
Tip 2: The dilated retinal exam
During your first few days, you’ll feel like you’ll never see the retina. After a week of practice, you’ll wonder why you ever struggled. This is really a matter of practicing to build muscle memory. Each lens has an optimal distance from the eye and slit lamp. The general approach is this:
- Hold the lens about 1 cm from the patient’s eye with your index finger and thumb, with your other 3 fingers braced against the top strap or the patient’s face. Now, swing it out of the way while you position the beam.
- Put the slit lamp beam right over the pupil, with the light source, slit lamp, and patient all aligned. Looking through the slit lamp, you should be able to see the red reflex and the beam should be traveling perfectly through the center of the pupil.
- Push the slit lamp all the way in close to the patient (about 10 cm from the patient’s eye), maintaining visualization of the red reflex the entire way.
- Now, swing the lens into the path of the light, and start backing away in a straight line.
- You’ll see a hazy red glow which should sharpen when you are focused.
- Now, you can move the slit lamp up, down, left and right to explore your view
- Photophobia is your worst enemy. It’s better to use a dimmer illumination compared to having your patient struggle against you. Beam size is important for the perfect exam – wider and shorter is reocmmended when you’re learning the ropes. A wider beam (1.5 mm wide) gives you the ability to really integrate what you’re seeing. A shorter beam (5 to 6 mm tall) helps to decrease photophobia.
- 80% of your patients will be old and have ptosis, be photophobic to any light, or will simply be unable to keep their eyes open. In these patients, you will have to open the lid. You can do this with your 3rd and 4th fingers while you hold the lens with your thumb and index finger. It’s tricky, but it’ll become second nature with practice.
Tip 3: The undilated optic nerve exam
When the dilated slit lamp exam is second nature to you, the undilated exam will be the next step. This exam is crucial for glaucoma patients, as we normally don’t dilate those patients in clinic as it can raise the IOP unnecessarily. Here is the general approach:
- Positioning is key. Have your patient look 15-20° temporally on the eye you are examining. It puts the optic nerve in view when you look in. This is where you hear the phrase “please look at my right ear” for examining left eyes, and vice versa. Another good reference target is the goldmann applanation tip, or the equivalent horizontal part of a teaching side scope.
- Use a smaller beam to reduce glare reflected from the iris. Try a 1.3 mm wide by a 3mm tall beam.
- Follow the same steps as the dilated retinal exam, but realize your view will be the size of the optic nerve head at best, and you will often not have a binocular view.
Tip 4: Checking for cells
The right magnification is key! Use only the 16x mag with an indirect beam. Always use the brightest light in the darkest room! Look for cells over the pupil, it’s the darkest part giving you the greatest contrast. Use the following SUN grading criteria to grade your exam.
SUN Grading Scheme for Anterior Chamber Cells:
Grade Cells in Field
0 < 1
0.5+ 1 – 5
1+ 6 – 15
2+ 16 – 25
3+ 26 – 50
(using 1mm slit beam)
SUN Grading Scheme for Anterior Chamber Flare:
2+ Moderate (iris/lens details clear)
3+ Marked (iris/lens details hazy)
4+ Intense (fibrin/plastic aqueous)
Tip 5: Checking intraocular pressure by applanation
By the end of your first year of residency, you’ll have performed this step at least a few thousand times. Here is how to do it your first time:
- Put a drop of fluorescein dye into your patient’s eyes.
- Clean the applanation tip or use a new tip: follow your institution’s guidelines.
- Rotate the prism until the line you see is horizontal.
- Swing the lamp to about 45 degrees and swing the applanator inline until it click locks.
- Flip your lamp to the blue setting, turn the brightness ALL the way up. This may require increasing both the beam width and the slit lamp power setting.
- Now, look into the oculars to ensure you see that the prism is horizontal.
- Tilt the control stick all the way back. This gives you fine control to push forward and land gently on the cornea! If you don’t do this, you’ll end up jerking the lamp around when you are very close to the cornea. Not only will your patient get scared, but they will start reflexively closing their eyes when you get close!
- Now, with the control stick tilted back, move forward to within 3-5 mm of the cornea.
- Push the control stick forward, using its fine control to move forward and land gently on the corneal surface.
- When you do this successfully, you will see the mires, and you will be able to adjust the dial accordingly.
Tip 6: Gonioscopy
The most advanced skill. Gonioscopy.org has a great set of videos on this, and they explain it well here: http://www.gonioscopy.org/