Bioptic Prescribing Made Easy: A Resource for Eyecare Providers

Introduction:

The primary purpose of prescribing bioptic telescopes for the visually impaired is to enhance their ability to see at a distance. As most modern bioptics are focusable they can also provide magnification at natural near and mid-range working distances. By being attached to conventional eyeglasses they provide convenient, hands-free access to the magnification effect with a simple tilt of the head making them easy to integrate into one’s normal activities.

Why enhance distance vision?

Distance vision is a social sense and is used to make eye contact, read body language and feel connected to the world around us. Reduced distance vision can cause individuals to feel isolated, which has been shown to lead to depression and increased risk of cognitive decline.

Bioptic Prescribing Goal.

Low vision experts seek to attain approximately 20/40 (6/12) through the bioptic telescope. Studies show that at that visual acuity level individuals can see adequately for virtually all visually-guided activities. Prescribing a higher power device to achieve better visual acuity is at the expense of a narrower field of view through the device, which is the major concern of bioptic users.

The Bioptic Experience

When people first look through a bioptic telescope, they often say that objects appear much closer. While this is true, the real benefit is that the telescope allows them to see objects that are farther away. The magnification factor determines how much farther they can see. For example, if someone can only recognize facial features no further than 10 feet away, a 2x telescope will extend their vision to 20 feet, while a 3x telescope will extend it to 30 feet, and a 4x to 40 feet.

Using faces as a testing target

Being able to clearly see a face at a typical social distance of at least 20 feet (6m) is a useful way to assess how effective a bioptic will be for an individual. Choosing a bioptic with enough magnification to make a face clearly visible at this distance can serve as a simple and practical method for determining the appropriate power.

Suggested Demonstration Method.

1. In normal room illumination stand in front of the patient at a distance of 3 feet (~ one meter). Ask them whether they can see your face clearly enough to recognize your features.
   1. If they can, slowly move further away until they can no longer see your facial features clearly. Then, move back to the furthest distance where they can see your face clearly, and note that distance.
   2. If they can’t, move closer until they can see your facial features clearly. Note that distance.
   3. Once you’ve found the furthest distance they can see your face, have them cover one eye at a time to see if one eye sees better than the other. If you’re prescribing a monocular bioptic, we prefer to prescribe it to the dominant and hopefully better-seeing eye if possible.
2. Telescope Power Selection Based on Visual Distance:
   Divide the furthest distance the patient can see your face into 20 feet (6 meters).
   For example:
3. 1. If the patient can see your face clearly at 10 feet, divide 20 by 10 = 2. Start with a 2.2x telescope.
   2. If they can see your face clearly at 5 feet, divide 20 by 5 = 4. Start with a 4x telescope.
   3. If they need to be as close as 3 feet to see your face, start with a 5x or 6x telescope.

Bioptics for near and mid-range applications

Using strong reading glasses or magnifiers to provide magnification for reading and table-top activities can be very challenging for the patient because the hands are needed to hold the materials very close to the face. Bioptics can provide magnification at normal near working distances with the use of reading caps (for the SightScope devices) or by focusing them (VES Devices). Since the bioptic is attached to the eyeglasses the hands are free to be used for the intended activity.

Demonstration hints:

1. First time patients will notice that the field of view of bioptics when looking at near distances is narrow
   and that they may have to move their head more to see everything they want to look at. This gets easier and more natural with practice. However, the benefit of the more natural working distance is usually preferred by patients in addition to their hands being available for the intended activity.
2. Because the field of view in bioptics becomes narrower as objects are viewed at closer distances, holding materials as far away as possible will maximize the field of view.