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Fitting BiOptic Telescopes: Determining Location and Mounting Angle with BiOptic Fitting Apertures. Robert B. Greer, O.D., F.A.A.O. University of California, Berkeley School of Optometry. BiOptic fitting apertures. Opaque black rings Varying outside diameters - PowerPoint PPT Presentation
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Fitting BiOptic Telescopes: Fitting BiOptic Telescopes: Determining Location and Determining Location and
Mounting Angle with BiOptic Mounting Angle with BiOptic Fitting AperturesFitting Apertures
Robert B. Greer, O.D., F.A.A.O.University of California, Berkeley
School of Optometry
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BiOptic fitting aperturesOpaque black rings
Varying outside diameters– Outside diameter noted in the corner of the
aperture– 14, 16, 19, 22, 24, 27 and 33mm
Central 3mm clear zoneStatic cling vinyl
Easily positioned on the lens
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BiOptic fitting apertures - benefits Confirmation of vertical and horizontal
placement of BiOptic telescopes Direct measurement of the telescope mounting
angle Allows patient and doctor to see where the
telescope will be located Shows how much of the lens will be occupied
by the telescope Enables the patient/doctor to see what head
movement is needed to access the telescope
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BiOptic fitting apertures
Outside diameter, in mm, is noted in the upper left corner of each aperture
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Vertical placement For distance, the BiOptic telescope is usually
mounted centrally or high in the lensUsually as high in the lens as possible, especially for driving or if near tasks will also be performed while wearing a distance BiOptic3mm between the edge of the telescope and frame must remain for lens structural strength
For near, the BiOptic telescope is mounted centrally or low in the lens
Central location may work best for computer use
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Vertical placement
Aperture high on the lens for distance use
Aperture low on the lens for near use
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Horizontal placement - distanceFor distance the telescope is placed at
the monocular distance inter-pupillary distance (IPD)
The IPD is often measured using traditional techniques such as rulers or corneal reflection pupillometers
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Horizontal placement - near For near the telescope is placed at the
monocular near PD appropriate for that working distance
Ian Bailey created a “rule of thumb” for calculating the near IPD:
Near IPD = Distance IPD - 1.5(working distance)– The working distance is expressed in diopters
Example– A patient with a 65 mm distance IPD wants to work at 25
cm which is a working distance of 4 diopters– Near IPD = 65 - 1.5 (4) = 59 mm
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Mounting angle The telescope must be angled so that its
viewing axis points towards the eye’s center of rotation
BiOptic fitting apertures allow for a direct measurement of the mounting angle
Mounting angle is referenced to the frame front
A telescope mounted perpendicular to the frame would have a mounting angle of zero degrees
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Mounting angleMeasurement of the
mounting angle requires a simple protractor with a plumb line
The plumb line may be a straightened paper clip or any other straight piece of metal
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Primary gaze - horizontal
Telescope viewing axis
Mounting angle
Distance mounting angle
Patient tilts head forward and sights a target at eye level through the aperture
Telescope viewing axis - horizontal
Telescope mounting angle = Frame angleTelescope mounting angle = Frame angleProtractor measures frame angle
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Primary gaze - horizontal
Telescope viewing axis
Mounting angle
Patient tilts head backwards and sights a target at eye level through the aperture
Telescope viewing axis - horizontal
Protractor measures frame angle
Telescope mounting angle = Frame angleTelescope mounting angle = Frame angle
Near mounting angle
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ReferencesBailey IL. Centering high-addition
spectacle lenses. Optometric Monthly. July 1979;95-100.
This presentation was downloaded from www.BiOpticDriving.org