Fitting BiOptic Telescopes: Determining Location and Mounting Angle with BiOptic Fitting Apertures

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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

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BiOptic fitting apertures

• Opaque 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 zone
• Static 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 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
• 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 - distance

• For 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 eyes 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 angle

• Measurement 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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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 angle
Protractor measures frame angle
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Distance mounting angle
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Near mounting angle
Primary gaze - horizontal
Mounting angle
Telescope viewing axis
Patient tilts head backwards and sights a target
at eye level through the aperture
Telescope viewing axis - horizontal
Telescope mounting angle Frame angle
Protractor measures frame angle
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Near mounting angle
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References

• Bailey IL. Centering high-addition spectacle
  lenses. Optometric Monthly. July 197995-100.
• This presentation was downloaded from
  www.BiOpticDriving.org