Light in the Eyes
Much of three point lighting really deals with targeting the eyes as a focus of the key light. The key light is intended to reflect in the eyes of the subject, adding a spark to the pupils. This is presented with a concrete issue when the subject is wearing glasses, which cause a complicated reflection in the glasses and will appear distracting and unattractive to the audience. There are a few ways that lighting can be altered so that it is able to deal with this situation, or at least to make it passable.
With or Without Glasses
The best solution for video lighting for eye glasses is going to be the removal of the glasses altogether, but only as long as this is acceptable for the subject. Even if a subject is able to tolerate the discomfort of having their glasses take from them, if they have dramatic issues with their sight this will be a problem on camera. Their eyes will not be fixed on an object, they will likely squint and shift perspective, and they will often have less grounding in the situation that is being recorded. Discuss the issue with them ahead of time, see how easy it is for them to go without altogether, and see if there are alternatives that they use like contact lenses.
Lighting Over Them
The first thing that must be arranged with the video lighting for eye glasses is to make the direction of the light miss the area of the glasses that
is going to reflect into the lens of the camera. To do this you start by pedestaling up the key light a few feet and tilting it down on the subject. You will then match this by bringing the light stand a foot or two toward the subject so that you will see the light peer onto the top of the glasses. You want it to shine down on top of them, allowing it to bypass the glasses for the most part. You may need to change the position of the fill light along with this, as well as the intensity. In general, you are going to need to adjust the aperture settings to go along with this. You may also need to bring the camera closer to the subject since the light will also be brought near. The backlight will not change unless it becomes too strong or the source enter the frame.
Instead of trying to bypass the glasses you may want to simply utilize the actual light reflection in the glasses, especially if you want to maintain your lighting set up and do not want the exposure and shadow sacrificing you will have to endure when bringing the light closer and above the subject. Instead, you want to minimize the appearance of the actual light in the reflection because a larger light surface will be more noticeable in the reflection of the glasses and will look less natural. This form of video lighting for eye glasses will require you to do a little testing and repositioning, trying to adjust the exact position in relation to the edges of the frames. This can also be negotiated against the reflection you may now see in the pupils, as well as any movement they may have. If you are going to deal with the reflection in the lenses then you should start at a smaller light size and work your way forward.
Photos: Royalty Free Images
Studio Umbrella Light: https://www.sxc.hu/pic/m/t/tp/tpacific/644739_studio_light.jpg
Personal Eyeglasses: https://www.sxc.hu/pic/m/a/af/afullmer/1327605_eyeglasses.jpg
Woman With Glasses: https://www.sxc.hu/pic/m/d/do/dolar/1305034_g_glasses.jpg