Training children in eccentric viewing: a case study.
Eccentric fixation occurs when the eccentric position provides the best-available vision and straight-ahead oculomotor reference. Eccentric viewing occurs when an eccentric position is used to improve vision, with oculomotor orientation remaining referenced to the fovea and the person being aware that he or she is not looking at the object of regard (von Noorden & Mackensen, 1962). When foveal vision is lost because of macula or optic nerve disease and a person looks "beyond" the object of regard to place the image on a viable area of the peripheral retina, it is considered eccentric viewing (Duke-Elder & Wybar, 1973; von Noorden, 1990). The natural development of the use of nonfoveal loci to improve potential sight in the presence of a central scotoma has been well described in the literature, with the anomalous fixation point described as a preferred retinal locus (Crossland, Sims, Galbraith, & Rubin, 2004; Fletcher & Schuchard, 1997; Macedo, Nascimento, Gomes, & Puga, 2007; Reinhard et al., 2007; Schuchard, 1995). Some researchers have described a trained retinal locus, a term that is generally used to indicate that training has been used to modify the position of the naturally selected preferred retinal locus (Deruaz et al., 2006; Nilsson, Frennesson, & Nilsson, 2003; Watson, Schuchard, De l'Aune, & Watkins, 2006). This research has predominantly been with adults with AMD and the use of the trained retinal locus to improve reading performance.
The need for such training has been debated in the literature. Nilsson et al. (1998, 2003) advocated the advantages of providing training in eccentric viewing, whereas other authors have reported that research has not yet supported the use of such training (Fletcher, Schuchard, & Watson, 1999; Schuchard, 2005). There is some support for the use of training an eccentric locus to increase the stability of fixation, but it is not clear whether this training is successful because it raises awareness of the preferred retinal locus or if a new trained retinal locus has been developed (Crossland, Culham, & Rubin, 2004; Schuchard, 2005). Research has demonstrated that there is an exponential decrease in visual acuity with eccentricity from the fovea (Davson, 1990). Logically, the closer an eccentric viewing locus is to the nonfunctional fovea, whether a preferred retinal locus or a trained retinal locus, the better the potential visual outcome. The evidence to date is not clear that the spontaneous development of the preferred retinal locus that is associated with the loss of macula vision inevitably provides the best potential acuity.
Eccentric viewing is predominantly discussed in relation to reading, but some researchers have noted the application of eccentric viewing to enhance the performance of activities of daily living (ADL) (Fitzmaurice et al., 1994; Nilsson & Nilsson, 1994; Schuchard, 2005; Vukicevic & Fitzmaurice, 2005). Although the development of the preferred retinal locus and training in eccentric viewing have been discussed primarily in relation to persons with AMD, children have high visual demands both for education and in their developing lives. It is interesting to speculate if children develop preferred retinal loci and if they develop retinal loci with the best potential for vision. Are the children aware of the preferred retinal locus and, if so, do they apply it when they undertake daily activities?
The following case study developed from a fortuitous association between an orthoptist specializing in vision rehabilitation (the first author) and a teacher of students with visual impairments (the second author). In Australia, children who are visually impaired are encouraged to attend mainstream schools and are supported by itinerant teachers of students with visual impairments who provide additional support in the school environment. It is not general practice in Australia to offer children training in eccentric viewing, since it is assumed that they will develop a preferred retinal locus. The case study provides an interesting example of the incorporation of training in eccentric viewing into an itinerant teacher's regular class activities with the children and, at least, the perceived improvement in visual function as a result.
Student B. Student B is a 10-year-old boy with a visual acuity of 6/24 (20/80) in either eye who read 12-point text with magnification. His vision was tested using a standard Snellen chart, and his reading was tested using a Curpax near-vision test booklet. His field of vision was tested using a 1-meter (about 3-foot, 3-inch) Bjerrum screen and a 3-millimeter (about a 0.118-inch) white target (see Figure 1).
Eccentric viewing for Student B is complicated by the doughnut-shaped area of vision in his left eye. The preferred area for eccentric viewing based on potential acuity is between the area of loss of foveal vision and the outer ring; however, this will reduce the field of vision available for use. Viewing outside the ring will provide a greater field but will significantly reduce his potential acuity; in fact, the potential level of acuity will be similar to that available in the right eye. On the basis of this field assessment, Student B was instructed to use the inner ring, looking 3 degrees to the right for reading and, beyond the outer ring, looking 8 degrees above for larger objects. At this initial assessment using EccVue eccentric viewing training software (Fitzmaurice et al., 1994) and following the instructions to look directly at the word to make it "disappear" into the scotoma and then to move his eyes slowly to the right until the word became visible, Student B read 16-point New Times Roman type without magnification.
Student C. Student C (Student B's brother), is a 12-year-old boy with a visual acuity of 6/60 (20/200) in either eye, who read 12-point type with magnification (see Figure 2). Eccentric viewing for Student C is more straightforward, since he looks approximately 5 degrees above the target using his right eye. At the initial assessment using EccVue software, Student C reduced the size of print he was reading from 24-point to 12-point New Times Roman type without magnification following instructions that were similar to those given to Student B.
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The assessment of the two boys was done by the orthoptist; this clinical assessment of the area of visual field loss involved a measured localization of the best potential retinal locus for eccentric viewing. The clinical assessment also enabled baseline measures, such as acuity and print size, to be accurately assessed. The orthoptist trained the teacher of students with visual impairments in the use of EccVue software and the principles of eccentric viewing training. The presence of a preferred retinal locus was not assessed for either boy, but baseline vision and reading assessments were done, allowing the boys to place their eyes into the fixation position they would normally use. Both boys reported being aware of seeing better by moving their eyes around a target, suggesting that both were using one or more preferred retinal loci. Both boys indicated they were not certain how to find these better areas of vision at will but moved their eyes around until they could see (note the students' comments presented later).
The EccVue software was delivered using the teacher's laptop. The software provides four training modules. The first two modules provide a structured approach to the two underlying concepts of eccentric viewing--awareness and quality of vision using eccentric viewing--and a guided method of learning the direction and distance of the refixation movement that are needed to align the eccentric locus with the object of interest. The complexity of the tasks increases from Module 1 to Module 2. Module 3 presents exercises that encourage the client to apply eccentric viewing in the broader daily-living context using photographs of common indoor and outdoor scenes. The client is encouraged to scan the image for an overall impression to identify the scene and then use the eccentric viewing technique to identify components of and details in the photographs. Module 4 introduces text reading to provide exercises for the client to apply the eccentric viewing techniques that were learned in Modules 1 and 2 to lines of text, combined with the basics of text reading, such as scanning and changing lines.
Before the boys started eccentric viewing training, their reading speeds and font sizes were determined without any instruction in moving their eyes to an eccentric position but allowing them to fixate the image to be seen as they would normally. A sighted, age and intellectually matched, student was assessed for comparative reading speeds and font sizes.
Student B had 13 sessions with EccVue over an eight-month period. After 9 sessions, he experienced difficulty with words merging and became despondent about the training. The orthoptist was consulted and determined that Student B was not actually looking to the fight of the object of interest as had been recommended. She reminded Student B of the basic steps to realign his vision; following these steps overcame the problem of the merging print and reduced the frustration that Student B was experiencing. Both the teacher and Student B considered typing and eccentric viewing his two major successes for the year; unfortunately, his print size and reading speed were not reassessed.
Student C had 11 sessions with EccVue over a 7-month period. At the start of the program, he was reading 24-point print at a speed of 97 words per minute; at the end of the program, he was reading 12-point print at a reading speed of 108 words per minute and 14-point print at a reading speed of 128 words per minute.
Following the training period, the boys and their parents agreed to a group interview with the orthoptist to discuss their impressions of the training and the impact, if any, on their visual function. The boys were asked if they were aware of the eccentric viewing strategy before they received training. They both indicated that they were aware of a "better" viewing area, but neither could find it regularly or at will; since the training, however, they used it automatically. As Student B noted: "I kept moving my eyes around trying to find the best place.... Now they automatically go there."
With regard to the situations in which they would use an eccentric viewing strategy, Student B indicated that he used it when watching television, writing, cooking, and finding things in the garden. Student C's comment summed up their responses "Yeah, you do sorta use it everywhere." When asked to give a bit more detail, Student C stated that he used eccentric viewing when he participated in activities of the Junior Country Fire Authority (a voluntary firefighting service in rural Victoria) and when using his MP3 player.
When the boys were asked if they used eccentric viewing at school, Student B said that he used the strategy particularly in math and English classes and that it helped him use his closed-circuit television because it made the images easier to find and increased his fluency. He also noted that eccentric viewing helped him play sports, particularly when throwing and catching, since he can now explain to his teammates where the ball needs to be for him to see it. In relation to other leisure activities, Student B said, "[Eccentric viewing] helps with cooking. I can see measurements more clearly ... and ... with video games ... it quickens my reaction times." Student C indicated that eccentric viewing helps him at school when he uses his laptop and ZoomText because magnification can be reduced and helps with reading and class worksheets. He also indicated that it helped him to cope if his teachers forgot to enlarge work--something he could not do before. As he put it, "it [eccentric viewing] helps to do pretty much everything as you are just using your vision better."
The boys' mother said that both boys were more confident at home and school, but especially Student C because he had moved from primary (elementary) to secondary school during that time. She noted that the boys can now do without Talking Books and that the font size required by each has decreased.
Both the orthoptist and the teacher perceived a number of benefits to using this approach to eccentric viewing. The use of EccVue made the teacher more aware of the letter and word confusions that the boys experienced. In particular, Student B had difficulty with letters above the line like "t" and "h" but not below the line, such as "j" and "y." Although the boys' ability to see better was not formally tested, the teacher thought that the boys' ability to see had improved and that the boys could now find target information more quickly. The combination of expertise provided the boys with an understanding of eccentric viewing that was based on appropriate assessment, rather than on experimentation, and ongoing support to allow them to become familiar with the technique gradually, thus embedding this strategy into their everyday pattern of visual function.
In conclusion, the two boys were intelligent and capable, and formal training in the eccentric viewing strategy apparently resulted in improved function. The boys' comments suggest that children may not automatically use eccentric viewing efficiently. Although the case study did not reveal whether training raised the boys' awareness of an existing preferred retinal locus and stabilized fixation or if a new trained retinal locus was developed, Student C's reading ability clearly improved, and the posttraining interview indicated that both boys perceived that their use of vision had improved. This case study supports the role of eccentric viewing as a vision rehabilitation strategy that enhances a range of daily activities beyond reading. In this case, incorporating training into an existing educational program appeared to be an efficient use of time and expertise of all concerned. The case study raises the question: Are there benefits to teaching an eccentric viewing strategy to children with macular vision loss?
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Kerry Fitzmaurice, Ph.D., associate professor and department head, Department of Clinical Vision Sciences, Faculty of Health Sciences, La Trobe University, Melbourne, Victoria, Australia 3086; e-mail: <email@example.com>. Lee Clarke, B.Ed., teacher of students who are visually impaired, Monterey Secondary College, Silvertop Street, Frankston North. Victoria. Australia 3200; e-mail: <firstname.lastname@example.org>.
Dr. Fitzmaurice is one of the designers and developers of EccVue. Although not actively marketed, the software is available for a fee. Contact the author for further information. The authors thank Students B and C and their parents for giving up their time to be interviewed and giving us permission to publish their experience and comments as a case study.
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|Title Annotation:||Practice Report|
|Author:||Fitzmaurice, Kerry; Clarke, Lee|
|Publication:||Journal of Visual Impairment & Blindness|
|Article Type:||Case study|
|Date:||Mar 1, 2008|
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