BiOptic Driving Network - Fitting a BiOptic

Magnification and location of the BiOptic telescope must be prescribed carefully to ensure its successful use. Determination of the appropriate magnification often entails a goal of having the patient see 20/40 (6/12) or better through the telescope. 

The prescribing and fitting of BiOptic telescopes or BiOptics requires

• calculating the proper telescope power

• selecting a suitable frame.

• determining the appropriate position of the telescope within the spectacle lens

• and the proper angling of the telescope relative to the frame front (mounting angle).

The horizontal and vertical placement of the BiOptic telescope, as well as its mounting angle (MA), should be carefully determined. The horizontal location of the BiOptic telescope will coincide with the monocular inter-pupillary distance (IPD) appropriate for the working distance. The monocular IPD may be measured with a pupillometer, ruler, or other technique and then refined through the use of BiOptic fitting apertures (BFA). BFA's are opaque black rings printed on static cling vinyl, making it possible to place the aperture anywhere on a lens and easily moved. The vertical position of the telescope depends on its proposed use. It is generally placed high in the lens for tasks such as driving, in primary gaze for computer use and low for near use. BFA's may be used to determine and/or refine the vertical placement of the telescope. 

The angle the telescope makes with respect to the spectacle frame is the mounting angle (MA). The result of a proper MA is a telescope that points at the eye's center of rotation, enabling the patient to sight along the telescope-viewing axis. The MA is upward for telescopes high in the lens and downward for telescopes low in the lens. BFA's enable the MA to be measured with ease and accuracy. 

Vertical placement

This patient is using an Ocutech VES Mini 3x. (Keplerian optics) Photo by: K. van der Spek, Leyden University, Netherlands.

For distance, the BiOptic telescope is usually mounted centrally or high in the lens

- Usually as high in the lens as possible, especially for driving or if near tasks will also be performed while wearing a distance BiOptic

- 3mm between the edge of the telescope and frame must remain for lens structural strength.

Horizontal placement

This patient is using an Ocutech VES Mini 3x (Keplerian optics) Photo by: K. van der Spek, Leyden University, Netherlands.

For distance the telescope is placed at the monocular distance inter-pupillary distance (IPD) 

BiOptic Fitting Apertures

See Determining Location and Mounting Angle with BiOptic Fitting Apertures by Dr. Robert B Greer, University of California, Berkeley.  (Microsoft PowerPoint,  1.4 Mb) 

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