Frenzel goggles are a standard tool in vestibular assessment. They allow an examiner to observe nystagmus while preventing the patient from visually fixing on the environment. Because visual fixation can suppress certain types of nystagmus, these goggles make it possible to see eye movements that would otherwise remain hidden. A do it yourself pair of Frenzel goggles can be a useful educational project for students of medicine or anyone interested in how vestibular testing works.

What Are Frenzel Goggles?

Frenzel goggles consist of high-power convex lenses, typically around +20 diopters, mounted in a light-tight frame. The lenses render the wearer effectively unable to focus on anything in the room. Inside the frame, a small light source illuminates the eyes. This setup allows an observer to look through the lenses and see the patient's eye movements clearly, while the patient cannot fixate on anything long enough to suppress nystagmus. The result is a more accurate view of the vestibular system's spontaneous activity.

Why Build Your Own?

Commercial Frenzel goggles are expensive, and for many people they are not worth the cost for occasional use. A do it yourself version can be put together with common materials. It will not match the optical quality of a professional instrument, but it can demonstrate the core principles effectively. Anyone attempting this project should understand that it is for educational and experimental purposes only. It should not be used to diagnose a medical condition, and any suspicion of a vestibular disorder should be referred to a qualified health professional.

Parts Needed for a DIY Build

• A pair of swimming goggles or a similar light-tight frame that covers both eyes comfortably.
• Two high-power convex lenses, roughly +20 diopters, with a diameter that fits the goggle openings. These can sometimes be sourced from magnifying glasses or optics suppliers.
• A small, bright light source, such as an LED with a battery and a switch. The light needs to illuminate the eyes without shining directly into them.
• An inexpensive video camera or a smartphone with a macro-friendly small lens module. Some DIY builders use a tiny endoscope-style camera that can be mounted inside the frame near the brow.

Building the Goggles

Start by removing the original lenses from the swimming goggles. Carefully shape the +20 diopter lenses to fit the openings, or use an adapter ring made from cardboard or a 3D printed mount. Secure the lenses in place so that no outside light enters around the edges. The goal is a seal that keeps the wearer from seeing anything outside the frames.

Next, mount the LED inside the frame, typically above or below each eye, angled so that the light illuminates the sclera without producing a distracting reflection. The battery pack can be taped to the outside of the frame or secured with Velcro. Test the light to ensure both eyes are visible to an outside observer looking through the lenses.

Finally, attach a small video camera. Some builders place a miniature camera between the lenses and the frame, while others mount it on a small arm in front of the goggles. The camera should be positioned to record the eye openings through the lenses. The ability to record a video of the eye movements is one of the main advantages of a DIY system, because it allows the nystagmus to be reviewed frame by frame.

Recording Nystagmus on Video

Nystagmus is a rhythmic, involuntary oscillation of the eyes. It can be horizontal, vertical, or rotary, and it can be an important clue to inner ear or neurological disorders. With Frenzel goggles, the examiner can observe this movement directly. Adding a video recording has several benefits. It creates a permanent record of the eye movement, allows the examiner to view the eyes without distraction, and makes it possible to slow down or repeat the recording to identify subtle patterns.

A simple DIY camera setup can capture a surprising amount of detail. Because the high-power lenses magnify the eyes, even a small sensor can record the pupil position and the visible blood vessels on the sclera, both of which help in tracking the movement. Set the camera to record in good lighting and keep the frame stable. A short video clip of ten to twenty seconds is usually enough to see the nystagmus waveform clearly.

Limitations and Safety Considerations

A do it yourself pair of Frenzel goggles is not a medical device. The optical alignment may be imperfect, the magnification may differ from intended values, and the lighting may be uneven. These factors can change how nystagmus appears. Therefore, any DIY build should be used strictly as a learning tool. If you or someone you know experiences persistent dizziness, vertigo, or unusual eye movements, consult a trained clinician rather than relying on home equipment.

When building the goggles, take care with lenses, adhesives, and cutting tools. Avoid using glass lenses that could shatter near the eyes. Use acrylic or polycarbonate lenses when possible. Also, keep the LED brightness moderate to avoid discomfort for the person wearing the goggles.