Haroon Rasheed, B.S., Shawn Lin, M.D.
Recording surgical videos are important to every ophthalmology resident’s learning experience. Through these videos, a resident can hone their technique, seek advice from mentors and attendings, and share unique and informative cases. Thus, knowing how to record high-quality surgical videos is imperative to a resident’s educational experience. In this article, we illustrate several techniques to perfect your next surgical recording.
Lighting:
Most surgical microscopes have 2 primary lights, a focused red reflex (RR) light and a diffuse full field (FF) light. When performing surgery, you can choose to use the red reflex light or full field light in isolation, or a mix of the 2 in any combination. In general, we recommend utilizing primarily the red reflex lighting over an equally mixed red reflex/full-field lighting for two main reasons:
- The 100% red reflex lighting offers a stronger red reflex and will result in a sharper image for the inside of the eye when compared to mixed red reflex/full field lighting. Images below demonstrate that mixed red reflex/full field lighting reduces the red reflex in favor of lighting the sclera and the lid speculum. This is because cameras attached to surgical scopes cannot see as much contrast as our eyes. When the conjunctiva and field are illuminated, the automatic gain function of the camera decreases the amount of light bouncing back to the scope, which in turn decreases the amount of light bouncing back through the pupil. In reviewing videos of surgical maneuvers, the additional clarity in focused red reflex lighting will allow for an improved analysis of surgical techniques.
- The halo of lighting for focused red reflex is smaller than mixed red reflex/full field lighting. The narrow spotlight forces the surgeon to exercise discipline and centration in keeping the eye in the primary position. It is an excellent way to train us to reduce unnecessary or extreme movement of the eye during surgery.
The below table compares different combinations of microscope illumination and recorded image quality.
| 100% FF/100% RR | 100% RR Only | 100% FF Only |
|---|---|---|
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Microscope Focusing:
Focus can be attained at any zoom setting via the foot pedal. However, the focus is often lost when the zoom setting is changed. Though the surgeon may not notice the loss in focus, the blur will be present on the recording.
The following techniques describe how to achieve the ‘sweet-spot’, a specific diopter setting on the oculars at which the surgeon will be able to move through the entire range of the zoom setting without losing focus. Either of the tests can be used to find the sweet spot.
Zoom Calibration Test:
- Place a target in front of the microscope and focus it with the foot pedal
- Shift zoom to the highest setting and focus again with the foot pedal.
- Shift zoom to the lowest setting. Refocus with eye-piece oculars. Do not use the foot pedal.
Sloping Paper Calibration Test1
The sloping paper calibration test aligns the three planes of interest: the surgeon, assistant, and video camera. While the surgeon and assistant have accommodation, the camera has a fine range of focus and cannot accommodate variations. Thus, the order of calibration for the sloping paper calibration test is the camera, surgeon, then assistant. Can this be done with normal paper instead of graph paper?
- Draw three adjacent rows of dots on paper. Normal paper can be used, but graph paper is best suited given the standard distance between each cell. Note that in the following steps the focus of the camera, surgeon view, or assistant view should be at the central row of dots on the paper at all times.
- Fold it into a slope or a tent-like shape and place it under the microscope. Place the sloping paper on a tray to allow for comfortable viewing through the microscope while sitting.
- Focus the camera by moving the microscope head up and down with the foot pedal until the plane of interest is in perfect focus on the video monitor.
- Once the camera is in focus, focus on the plane of interest through the surgeon’s oculars using only the diopter rings on the eye pieces. Start from the plus side and minus from there to avoid over minusing. Check again to ensure the camera is still in perfect focus.
- If the assistant has a focusing knob, it can be set to a neutral position. If the neutral position doesn’t exist, either dial in the distance refraction or the setting on the surgeons’ oculars.
Note: If the diopter setting on the zoom-calibration test differs from the diopter setting of the sloping paper test there are two possibilities: 1. The tests need to be repeated OR 2. the microscope is not properly aligned and calibrated.
Once you have optimized your lighting and your focus, you are ready to film high-quality surgical videos!
Citations:
- Socea, S. D., Barak, Y., & Blumenthal, E. Z. (2015). Focusing the surgical microscope. Survey of ophthalmology, 60(4), 373-377.
