Smith Knowledge Turbo OTG Fan Goggle Review

Smith Knowledge OTG Turbo Goggle

The Smith Knowledge OTG Turbo Fan Goggle is the best option for those who wear glasses on the mountain. If you don’t have perfect vision, then it’s recommended to wear contacts while on the mountain. It’s a lot less hassle and you can wear any goggle you desire. However, there are some of us who can’t wear contacts or don’t get on well with them for whatever reason.

For those of us who wear glasses under our goggles, the options for goggles are much more limited. What is needed is a large goggle with room enough to fit lenses and frames underneath without smashing the glasses onto your face. The ventilation is key because the glasses will want to fog up easily under the goggles regardless of the anti-fog properties of your goggle lens. The best lens tech in the world is quite worthless if you can’t see because your glasses are fogged up underneath.

Find out more in my Smith review below:

Knowledge Turbo Fan OTG Fit/Performance

I’ve tried several options in OTG (over-the-glasses) goggles but always had issues. The Smith Optics Knowledge OTG with Turbo Fan, while not perfect, is the best option I’ve found to date. I’ve been using these for almost 2 months now, so I feel I’ve used them enough in varying conditions to give a review of their performance. First off, these goggles are huge. There’s plenty of room for practically any type of glasses and lens size.

They incorporate a number of features which make them comfortable to wear over glasses, including a multi-piece nose bridge that helps to alleviate pressure where your glasses and goggles rest. There’s also a large volume of air in between your face and the goggles to assist with anti-fogging. The peripheral vision is obviously great due to their large size. They’re so big I wouldn’t recommend wearing these if you don’t wear a helmet, as they look quite ridiculous, even if you have a large head. They are best when used with a helmet and work particularly well with the Smith Vantage helmet.

Smith Optics

The features of this goggle are all fairly standard for a high end goggle, but appreciated nonetheless. Scratch resistant mirrored lenses, dual lens tech to decrease fogging, articulating lens straps to ensure proper fit with different helmets and head shapes, silicone backed strap to prevent slipping on helmets, strap clip buckle for easy removal, dual layer moisture wicking face foam, and of course Smith’s proprietary anti-fogging features.

Note this goggle uses a cylindrical lens and not a spherical lens. I won’t get into the technical details of each type here, but generally the new preference is for spherical lenses for optimum vision. Smith claims the Knowledge lenses still use their TLT optics to prevent refraction of light and deliver distortion-free viewing. I can’t dispute this, as I found the tapered cylindrical lens used in the Knowledge to provide exceptional clarity and detail without distortion.

What’s this Turbo Fan thing?

You can’t talk about the Turbo Fan version without mentioning the fan. It is a small fan at the top of the goggle frame that helps to keep fresh air flowing and exhaust moisture from inside the goggle. It uses 1 AAA battery and has a small switch on the side of the goggle which is attached to the goggle strap. Once you get the hang of it, it’s easy to operate even with gloves on. Due to the large air chamber and ample airflow, I actually don’t have to use it that often. It’s really nice to have when needed though. The goggle lens itself has never had fogging issues. I’ve only had a few issues with my glasses fogging in rare circumstances. Typically this is stopping after working hard or breathing hard while using a face mask.

In these cases turning the fan to the high setting will help to clear the fog from my glasses after a few moments. On warm or really cold days, running the fan consistently on its low setting prevents most potential glasses fogging issues. In use I found the fan to be surprisingly quiet in either setting. I hardly noticed it was on most of the time. I’ve been quite pleased with the battery life. I don’t really change it all that often. Make sure your helmet does not obstruct the fan or it will not work as effectively. I’m using mine with a Smith Vantage helmet and the 2 work together great. There is no system that is perfect for keeping glasses fog-free under goggles. You’re always going to experience some problems now and again. Currently, this is about the best you’re going to get if you wear glasses.

Lens Types

The ones I purchased came with Smith’s Ignitor Mirror lens, which Smith lists as a good lens for most all around conditions. They’re listed as 35% light transmission. In practice I found them to be better for the brighter days. They worked well in most conditions, but I found myself having problems seeing in some of the shadowy sections and late afternoon/early evening. On overcast days I could still see, but making out any details in terrain was somewhat difficult. I ended up ordering the Sensor Mirror lens from Smith’s website, which I found to be just about perfect for low and flat light conditions.

It is a 70% light transmission lens. The tint seemed to bring out terrain detail and improved contrast in areas where the sun wasn’t directly shining. This will probably be my go-to lens unless it’s a bright bluebird day, then I’ll pull out the Ignitor lenses again. Lens changing was surprisingly easy for a goggle that doesn’t employ a quick-change system like Smith’s IO. You simply separate the top of the goggle frame from the lens and disengage all tabs, then pull the lens out from the bottom of the goggle frame. Installing a new lens is the reverse. You just push the lens into the bottom of the frame then pull the top over the lens and make sure all tabs are fully engaged. I was able to make the lens change in about 2 minutes the first time I tried it. Both the mirror lenses look good, and help to not show your glasses behind your goggles.


The Smith Knowledge Turbo Fan OTC Google is a great option for people who need to wear glasses under goggles. Not perfect at preventing glasses fogging under goggles, but currently the best option I’ve found. Large goggle with large fit. Excellent vision and optics despite not being a spherical lens. Works best with Smith helmets that do not obstruct fan exhaust.



Put your glasses and goggles on inside the lodge or gondola and never remove your goggles on the mountain. Once you allow the lenses of your glasses get too cold, it’s going to be really difficult to keep them fog free when you put your goggles on over them. If you have fogging problems on the mountain, use the fan for a minute and let it exhaust the moisture. You’ll be fine, especially once you get moving again. Removing your goggles to wipe your glasses off will only make it worse.

Smith Knowledge
4.5 / 5 RATING      

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