Low Vision Part IChapter 4.1.1

OverviewThis presentation covers the implications for communication with people who have tunnel vision. It includes:• Ways of measuring and discussing

vision• Tunnel vision (Retinitis Pigmentosa and

Usher Syndrome)• Signing Space modification

Measuring VisionThere are 2 ways to measure vision:1. The first is called field of vision or the

scope of a person’s peripheral vision. This is the ability to see on the side/top/bottom while looking ahead.

2. The second, called acuity, is the clarity or sharpness of a person’s central vision.

FunctionsPeripheral vision:• Is not very good for seeing detail• Is very good for detecting movement

(think of deaf people waving to catch someone’s attention). It warns us of things approaching (like dogs, cars or other people)• It is good for seeing in dim light

(although not good for distinguishing colors)

Functions, cont.Central Vision:• Is good for seeing detail (think of

reading print or seeing minute changes in facial expressions)• Is good for seeing colors

RETINITIS PIGMENTOSA &TUNNEL VISION

Retinitis Pigmentosa (RP)• Most deaf-blind people are deaf and

blind as a result of a syndrome called Usher Syndrome. The Usher genes cause gradual, increasing blindness beginning with diminished peripheral vision.

• The person’s central vision remains clear longer and it is only at the later stages that the central vision too is affected.

RP and Tunnel VisionWhen the peripheral vision is impaired or less functional, the person has what we call ‘tunnel vision’ since it is somewhat like looking down a dark tunnel.1. Without good peripheral vision, the

deaf person begins to trip over things, not see others trying to get their attention, and

RP and Tunnel Vision, cont.2. Has an exceptionally hard time

seeing in dim light, sometimes called ‘night blindness’.

Tunnel Vision = Seeing Part of the Scene

Vision vs. Perception• People with tunnel vision do see, but

unaware of how much they are missing or do not see.

• When they see only part of an object, they may be able to recognize it (perceive it in their mind); it seems as if they ‘see’ the entire thing.

Vision vs. Perception, cont.• It is like “seeing” an object on your desk

sticking out from under a stack of papers; you see just enough of the object to recognize it in context.

Tunnel Vision

Lara

Tunnel Vision and SSPs• It may be useful to identify yourself to

save the person with tunnel vision from having to strain.

• Guiding may be helpful, especially if the area is unfamiliar or there are obstacles to move around.

• You will likely need to adjust your signing.

TUNNEL VISION AND SIGN LANGUAGE

Signing Space • The natural signing space is roughly

mid-chest. This allows the listener to focus on the signer’s face (and expressions) and perceive the general hand-shape and movement of the signs.

• For a person with tunnel vision the signing is done higher, closer to the face.

Signing SpaceKeep your signing within the space of the circle on the right.

Fingerspelling• The natural space for fingerspelling is

slightly higher. Unlike many signs, the hand-shapes are critical in reading fingerspelling (and thus ‘reading fingerspelling’ requires more acuity or central vision).

• For a DB person it may take slightly longer to focus and thus the fingerspelling would need to be done with the same rhythm but slower.

Fingerspelling

Tunnel Vision & Signing Space• Accommodating tunnel vision means

signing somewhat higher up and in a smaller space.

• Signing in front of the face obscures facial expressions or non-manual grammatical signals. At this point it is often better to switch to ‘tracking’ so the DB person can both look at the signer’s face and follow the signs.

Signing Space

Tunnel Vision, Sign Language and Group Conversations

• Tunnel vision interferes with looking back and forth between signers and with focusing quickly.

• It also prevents seeing (with peripheral vision) the beginning signs of the next person to speak, so there are not the same cues where to look.

Tunnel Vision, Sign Language and Group Conversations, cont.

• Thus tunnel vision interferes with participating in group conversations in Sign Language.

Group Conversations• If you are the only person familiar with

tunnel vision, make sure the DB person does not get left out of the conversation.

• In group conversations, the person yielding the floor will point (indicate who is next; who is beginning to talk).

• When it is your turn, put your hands at the ready then wait until the person with tunnel vision has time to focus.

Practice• Try out different simulators (glasses or

blindfolds that simulate tunnel vision).• Work in pairs (one person using

simulators, the other as a guide).• Move about the room, hall, and outdoors.• Try communicating with one another.• What do you notice?• Then switch (15 minutes each person).

Discussion• What did you notice?• Where did you go?• What did you do?• How did you feel?• How will this relate to your work as an

SSP?