The findings from your initial consultation are as follows: GH: Good, no medicationsPOH: Glasses since teenagerVert: R) -0.50/-1.00x45 L) -0.75/-1.00x60 (Single vision distance gls) VA cc: R) 6/12 L) 6/9Near vision BEO = n5 slowly (takes glasses off to read) Subj Refn: R) -0.77/-1.00x50 = 6/9 pt L) No changeAdd +1.00 = n5 with light, BEO Contrast (Pelli Robson):0.90 log BEO (moderately reduced contrast)Colour vision (CUCVT): non-specific colour vision loss, greater in the tritan zoneVisual field (Humphrey): severely constricted R&L to within 10 degrees from fixation
Key to rehab of pts with peripheral loss is understanding the 3 basic functions of peripheral vision: Organisation of visual scanning Visual warning system Night vision
The peripheral system is integral in helping us to organise our visual scanning. When someone with normal sight looks at a scene or a face, as in this example, they make several saccades to orientate themselves to what they are looking at. Each saccade ends with a fixation which lasts less than a second at each point. The visual system then pieces together each of these fixations to gather an overview of the scene.
The second function of peripheral vision is use of the visual peripheral as a warning system. This is essential when driving, walking through crowds etc.
The other function of peripheral vision is ability to see at night. The peripheral retina is most sensitive under scotopic conditions than photopic so a loss of peripheral vision leads to night blindness and difficulty adapting when lighting conditions change – eg: going from light to dark.
Eye diseases affecting the retina that lead to tunnel vision usually come on gradually. This does give the patient some time to adapt. However, teaching compensatory scanning is essential.
How do we do this? Start with simple scanning of an object on a table. Place an object, for example this simple toy, on an uncluttered table in front of your patient then instruct them to search by moving their eyes to sweep across the table, left, right, up, down, until the locate the object
You can follow up the simple scanning exercise with a more complex task. Just take an A4 sheet of paper and draw up this scanning training exercise shown here. The patient fixates on the word “start” and then follows the line accross to number 1 and so on, to the end.
You can adapt the scanning training for distance too. You just need a bit of wall space and stick some letters on the wall about 1 m apart and the patient scans from letter to the other.
Your next task is to read this article by Peter Herse. After you’ve done that you can answer the questions related to Lionel’s case.
On a final note, the training techniques I’ve mentioned here can also be applied to patients with acquired brain injuries and other neurological problems (things such as Hemianopia resulting from a stroke) and this will be expanded further in a new case study.
Management of peripheral vision loss
Low vision management strategies
for patients with severely
constricted visual fields
Content prepared by
Dr Meri Vukicevic
• Dx with RP age 30
• C/o: decreased
peripheral VA, night
Lionel – Initial consultation
GH: Good, no medications
POH: Glasses since teenager
Vert: R) -0.50/-1.00x45 L) -0.75/-1.00x60
(Single vision distance gls)
VA cc: R) 6/12 L) 6/9
Near vision BEO = n5 slowly (takes glasses
off to read)
Subj Refn: R) -0.75/-1.00x50 = 6/9 pt L)
Add +1.00 = n5 with light, BEO
Contrast (Pelli Robson):0.90 log BEO
(moderately reduced contrast)
Colour vision (CUCVT): non-specific
colour vision loss, greater in the tritan
Visual field (Humphrey): severely
constricted R&L to within 10 degrees from