Prescribing Bioptic Telescopes

Qualify, Demonstrate, Indoctrinate, Recruit

Henry A. Greene, OD, FAAO

Reading is a solitary activityMost responsive to low vision aids

high contrast controllable environment

Reading is the most easily replaced visual activity

talking books radio, TV sighted support

Distance Vision is a Social Activity

Seeing faces Interpersonal relations

Non-verbal body language Making eye contact

Avoidance of isolationQuality of life

“Before I got the telescope, my world extended to the end of my arms. The

telescope made my arms 4 times longer”

“Visual Radius”Derived from Proximal Magnification

Moving closer makes the retinal image larger

The furthest distance at which one can discern facial features

Under normal illumination

Visual Acuity Correlate 2 feet = 20/200 1 foot = 20/400

The Telescope “Face” Test

A good response to high contrast targets is not prognostic

The face is a convenient low contrast target Seeing a face well through a TS at 8-10 feet is

prognostic of magnification response Poor response associated with edematous maculas

“Visual Radius” and “Social Range” “Social Range”- 3 to 15 feetExpand the “Visual Radius” sufficiently into

the “Social Range”Telescopes extend the visual radius by the

power of the deviceWith a 4x telescope:

2 feet becomes 8 feet 6 inches becomes 24 inches

TS Prescribing Paradigm Summary Identify the furthest distance that a face can be

seen- “Visual Radius” Confirm a favorable response to telescope

magnification- “Face Test” Extend the “Visual Radius” into the “Social Range” Establish realistic goals and expectations

Magnification is not natural.

Constraints of Magnification Working Distance Shallow Dept of Field Narrow Field of View

Constraints on the patient Unnatural working distances Disorientation Inconvenience Fatigue

What are bioptics? Eyeglasses with a miniature built-in telescope Allow use of normal and magnified vision by simply

tilting the head- like “upside down bifocals” Do not interfere with walking Help you see things further away:

Spotting- like the use of rear and side view mirrors Continuous tasks- TV, computer

Best for midrange and beyond Not ideal for reading

Basic Optical Concepts

Galilean vs. Keplerian Larger objective lens:

Brighter image Shallower depth of field

Larger, multi-element eyepiece: wider FOV

Longer eye-relief: Narrower FOV

Characteristics of Bioptics

Galilean Keplerian

Size Small, Very Small Big, Bigger

Shape Std. Tube

Micro

Std. Tube

HLP, BTL

Focusing Fixed, Manual Manual, AF

Powers 1.8 – 8x 3 – 8x

Fields

4x

Narrow

5 deg

Less Narrow

12.5 deg

Optics vs. electronics

Optics Electronics

Image Resolution High Low to moderate

Brightness Inside variable

Outside good

Inside good

Outside poor

FOV- 4x 12.5 deg 40 at 1x; 10 at 4x

Power range Fixed Zoom

Ease of Operation variable variable

Mobility with aid Easy Variable to none

Weight variable Variable to ugh!

How much power?

Enough magnification to achieve the goal Acuity demand:

Average ~20/40 goal High ~20/30 goal

Sporting events? More than 6x is tough to keep stable on the head More than 7x- time for binoculars

How much Field?

What is a degree? How much FOV is enough?

It’s never enough- minimum ~ 5 deg Use comparisons- TV; rear view mirror It gets more natural

Maximize for close distances Let the patient compare using handhelds

4x12 Keplerian vs. 3x Galilean

User issues regarding bioptics Low Vision Device Use Among Veterans

Watson, et.al., OVS, 74:5, May 1997 200 veterans, 740 devices, 130 spectacle TS

Issues: Wider FOV- 83% Autofocus- 79% More power- 78% Brighter image- 49% Less noticeable 16%

When to AF and when to not…

Acuity between 20/70 and 20/200 Room and mid-range activities

Not for >20’

Dexterity issues Tremors, Paresis

Application issues Hands-free activities

Courtesy CNN

Which eye? Or both?

Prescribe for the dominant eye if at all possible Suppression difficulties significantly undermine acceptance

Binocular systems- Challenging to keep aligned- Very stiff frame, Beecher Wider FOV, Acuity and CST summation, no suppression issues,

lessens impact of scotomas Binocular Working distance fixed

Monocular is easier

What position? Types of mountings:

Permanent (glued) vs. adjustable Minimum 3mm above eyepiece to top of lens Align the bottom of eyepiece to top of pupil The higher the eyepiece= the higher the TS angle

the greater the head translation Lower and straighter position for

midrange applications Use a head strap Use wide nosepads

                            

Carrier lens issues Use their habitual distance Rx

Single vision or multifocal Avoid progressives and trifocals

Minimum 10mm between bottom of eyepiece and top of seg Seg high but not too high Low but not too low

Avoid polycarbonate lenses- hi index OK Tough to drill

Qualify the PatientNot all patients are bioptic candidates

Establish a prognosis for likely success The Clinical Evaluation

Address Finances and Appearance This is not cheap-- “Is it worth it to you?” “It looks a little unusual-- will you wear it?”

You’ll have to learn to use it Are you prepared to make the effort?

Qualify the patient:Establish a telescope prognosis Hard Signs

1. VA between 20/70 and 20/300 (faces >2 feet)VA gain with 4x TS? Fluency

2. Response to low contrast targetFaces at 10 feet through 4x12 TS

3. Better eye is dominant Soft Signs

1. Appropriate goals: mid-range and beyond2. Motivation: appearance, enthusiasm3. Dexterity

Test and demonstrate with Handheld Telescopes first

Handheld 4x12- prefocus! Determine the dominant eye

Which eye do they take the TS to?

Evaluate response to faces at ~10 ft Poor response undermines prognosis

Needs brighter image

Show: Narrow FOV- challenges in finding the target Shallow DOF- challenges in keeping clear Need to refocus- challenges in doing the activity

Demonstrate Bioptics next

Get them out of the exam chair Present the concept of the “Magnification Factor”

With a 4x TS- What you see at 2’, you’ll see it at 8’

Realistic experiences= realistic expectations The “Eye Chart” is NOT the “real world” “Grocery Store,” CRT, Pictures on walls Sit in the “living room” (Waiting room) Outside- signs, flowers, faces

Use your assistant Have family accompany

Recruiting the Patient

“We can teach them to ride the bike,

but they have to do the pedaling.” The patient’s job:

To want to improve their vision To make the effort to learn to use it To be frustrated To invest time and $

Training Techniques Sighting through eyepiece

Give them a tour of the device Translation

Switching between carrier and eyepiece Localization

Aiming and Switching Tracking

Moving targets Near localization and hand-eye coordination

Finding the target