Low Vision Part I Chapter 4.1.1 Overview This 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 Vision There are 2 ways to measure vision: 1.The first is called field of vision or the scope of a persons 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 persons central vision. Functions Peripheral vision: Is not very good for seeing detail Is very good for detecting movement (think of deaf people waving to catch someones 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 persons central vision remains clear longer and it is only at the later stages that the central vision too is affected. RP and Tunnel Vision When 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 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. 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 signers 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 Space Keep 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 signers 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. Thus tunnel vision interferes with participating in group conversations in Sign Language. Group Conversations (cont.) 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?