How to use a slit lamp?

The slit lamp is the core instrument of ophthalmology, and you hope to quickly master its use in the first month of hospitalization. We have collected tips for the highest yield, so that you can check like a professional. These are the difficulties that all beginners must work hard to overcome. Let’s find how to use the slit lamp.

The following knowledge points are listed below:

Ø  Slit lamp positioning

Ø The dilated retinal exam

Ø The undilated optic nerve exam

Ø Checking intraocular pressure by applanation

1. Positioning

l The doctor’s position

Put yourself in front of the patient. You can raise or lower the patient's chair at any time to get them in place, but if the slit lamp is not at the proper height for you, it is difficult to adjust your own chair. When bad habits cause neck strain, bad exams, and fatigue, you will regret it. Put your chair at a suitable height for you to sit comfortably, and adjust the slit lamp motorized table so that you can sit upright while looking through your eyes. Do not bow your head, do not tilt your head, do not use a slit lamp when standing.

l Patient

When you run  slit lamp fast, the following steps should take less than 15 seconds. Even if you need to take a 15-minute exam, these will make you successful. It is essential that the patient feel comfortable. They are more likely to open their eyes wide, look in the direction you want them to look, and then remain motionless.

Cleaning: Clean the  slit lamp tonometer, torticollis, upper straps and handles. When the patient does not see other people's cosmetics or dandruff sticking to the plastic, they will cooperate more with your inspection!

Adjust the patient's head position: to position the patient correctly, Instruct the patient. Keeps the slit lamp examination table super stable and safe for use when you flatten, remove sutures, etc.

Adjust the patient chair: Move the patient chair up and down to make the patient's height correct.

2. The dilated retinal exam

Adjust your beam of the slit lamp. Photophobia is your worst enemy. It is better to use darker lighting instead of letting your patients fight against you.A shorter beam (5 to 6 mm high) of the slit lamp helps to reduce photophobia, while a wider beam (about 1.5 to 2 mm wide) of the slit lamp helps to integrate what you see.

Hold the lens of the patient's eye about 5-7 mm (depending on the lens) with the index finger and thumb. Place the other 3 fingers against the upper harness or the patient’s face. Now, when you position the beam, set it aside.

Aim the slit lamp beam so that it is perpendicular to the patient’s eye and directly through the pupil. Through the slit lamp, you should be able to see the red reflection, the beam should pass completely through the center of the pupil, and the iris should be the focus.

Now, turn the lens to the path of the light of the slit lamp and start to recede in a straight line.

Professional learning tip: Before you start to back up with the joystick, you can move your head aside to see if your lens is aligned correctly. You should be able to see the patient's eyes through the slit lamp.

When you start to retreat with the slit lamp, you will see a dim red light, which should become sharper when you concentrate. You can also get a clearer image by adjusting the angle of the lens and the distance from the eyes.

Once you see the retina, adjust the slit lamp instead of the lens to explore your field of vision. You can adjust it up, down, left, and right.

80% of patients are elderly, have ptosis, are photophobic to any light, or cannot open their eyes at all when they diagnosed by slit lamp. For these patients, you must open the slit lamp lid. When you hold the slit lamp lens with your thumb and index finger, you can do this with your third and fourth fingers. This is tricky, but after practice it will become second nature.

3. The undilated optic nerve exam

Slit lamp uses a smaller beam to reduce glare from the iris. Try a 1.3 mm wide and 3 mm high beam.

Slit lamp and patient positioning is the key. Ask your patient to temporarily look at your examined eye for 15-20°. When you look inside, it puts the optic nerve in the field of vision. Here you will hear "Please look at my right ear" to check the left eye, and vice versa. Another good reference target is the Goldmann flattening needle tip, or the equivalent part of the teaching side oscilloscope.

4. Checking intraocular pressure by applanation

Put a drop of fluorescein dye into the patient’s eye.

Clean and flatten the patch or use a new patch: follow the guidelines of your institution.

Swing the beam about 45 degrees away from the centerline, and then swing the flattener along a straight line until you feel it click

Adjust the prism (flatten the tip) so that it also faces the center line.

Turn the light of the slit lamp to blue and increase the brightness a bit. This may require increasing the beam width and slit lamp power settings.

Now, take a look at your eyes and make sure you see that the prism is level.

Tilt the slit lamp lever completely back. This allows you to control the push forward and gently land on the cornea! If you don't do this, you will turn the light around when you are very close to the cornea. Not only will your patients be scared, but they will instinctively close their eyes when you approach!

Now, the lever is tilted back and moved forward to within 3-5 mm from the cornea.

Push the slit lamp lever forward and use its fine control to move forward and lightly land on the surface of the cornea.

When you do this successfully, you will see the quagmire and you will be able to adjust the dial accordingly.

So you have known how to use a slit lamp now.