T. Hain, MD
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Frenzel goggles are extremely useful in evaluation of patients with vestibular disorders. In essence, they consist of the combination of magnifying glasses (+20 lenses placed in front of the patient), and a lighting system. When Frenzel's goggles are placed on the patient, and the room lights darkened, nystagmus can easily be seen because the patients eyes are well illuminated and magnified, and because fixation is removed as the patient can hardly focus through magnifying glasses on a dark room.
Frenzel, a German physician, should not be confused with Fresnel, a German physicist. Although I am sure you could use Fresnel lenses in Frenzel's goggles, to my knowledge, nobody has yet done this.
Note that video-eye movement recording systems (see picture to right), such as those sold by Micromedical Technology (Chatham IL, USA, 217-483-2122) are usually preferable to Frenzel goggles. Video systems provide a mechanism of recording the examination and also are more educational for patients, spouses and students. Video goggles eliminate vision entirely, compared to Frenzel goggles which merely obscure vision. In the author's view, this is a very important advantage. They cost considerably more (about $4000).
The best of all worlds is to have a portable Frenzel goggle that one carries around for consults, and a fixed video Frenzel goggle for the clinic.
Anyway, there are four sources of the real Frenzel glasses that I am aware of which are discussed below:
Most people use the Baxter or Storz glasses.
Baxter (cat # Au5050). Baxter often doesn't even seem to know that they sell these things so use the catalog #. Their goggles are actually made in Germany, and are lightweight and sturdy. The bulbs are expensive, about $20, and are the same ones used by Storz, but they don't blow out that frequently. One disadvantage is that you must purchase a power supply to go with them. They work well with a 4-volt supply. Too much and they get hot and the bulbs blow. Too little and you can't see. The bulbs blowing thing is a safety issue as glass shards can be produced. So, we do not recommend using anything but a fixed voltage 4-volt supply. These glasses are not UL approved.
I got mine from Ilean at the V. Mueller Division (800-323-9088). Another contact # is 708-948-3756. The price in 1996 was $477 for the glasses, but Storz sells them for $100 less (see below). These goggles need a 4 volt power supply. Bome sells an inexpensive one that can be modified to produce 4 volts. Bome's number is 716-436-6584. Storz also sells a power supply.
ICS's Frenzel's goggles are a new player on the block. Personally, I prefer the Baxter goggles, but ICS's goggles aren't bad. They are made of plastic rather than composite like the Baxter and Nagashima brand goggles, and their lighting is a bit dim compared to either. They are priced similarly to the Baxter/Storz goggles.
ICS is located in 2227 Hammond Drive, in Schaumberg, Illinois, 60173. The contact person is Del Bloem. 708-397-2150. ICS has a distributer network in the US for selling ENG equipment, and you should also be able to get these goggles through them. They can also be reached through the Internet.
The Nagashima Frenzel's goggles are the best on the market (excepting the video system), but they are somewhat expensive (>$1200 last priced). They are nicer than the others because of their bright lighting, wide field of view, and relative comfort (for the patient). In my opinion, they are really not worth $1200 -- maybe $600, but if you have lots of money to spend, hey, why not go for the best. On the other hand, if you have lots of money to spend, it might be a better idea to get a video system. I am told (but am not entirely sure) that the Nagashima goggles are the only ones that are UL approved. This may be important if you are planning to use them in a hospital. Nagashima's rep. in the US is Kelleher Medical, Inc. They are located at 2824 Anwell Drive, PO Box 3894, Richmond VA. 23235. Their phone is 804-323-4040, or 1-800-222-7577. Kelleher Medical has a poor return policy, and in our opinion, most people might do better with a less expensive pair of goggles from a larger vendor that has a better return policy, or just get a set of video goggles.
Storz sells the same goggles as does Baxter. Prices as of 4/8/97 for the goggle is 375.00. The power supply (S1910A) is 124.00. Storz is located at 3365 Tree Court Industrial Blvd St. Louis MO 63122. Phone: 1-800-325-9500. Fax: 314-225-7203