Low Vision

The care of low-vision patients is termed vision rehabilitation, and optometrists have an essential role to play in the provision of vision rehabilitation services. Ideally, if patients stay with one optometrist or practice, their low-vision care becomes part of a continuum of eye care, from the time when they had normal vision. If progressive vision loss occurs, the role of the optometrist changes from primary eye care only to one of monitoring vision loss and gradually introducing low-vision care, especially magnification and advice on lighting and contrast, in conjunction with other vision rehabilitation professionals.

The performance of a prolonged reading task by students with low vision

Purpose: Students often read for long periods and prolonged reading practice may be important for developing reading skills. For students with low vision, reading at a close working distance imposes high demands on their near visual functions, which might make it difficult to sustain prolonged reading. The aim of this study was to investigate the performance of a prolonged reading task by students with low vision. Method: Forty students with low vision, aged from eight to 20 years and without any intellectual, reading or learning disability, were recruited through the Paediatric Low Vision Clinic, Buranda, Queensland. Following a preliminary vision examination, reading performance measures—critical print size (CPS), maximum oral reading rates (MORR), near text visual acuity— were recorded using the Bailey-Lovie text reading charts before and after a 30-minute prolonged reading task. Results: The mean age of the participants was 13.03 ± 3 years. The distance and near visual acuities ranged between -0.1 to 1.24 logMAR and 0.0 to 1.60 logMAR, respectively. The mean working distance of the participants was 11.2 ± 5.8 cm. Most of the participants (65 per cent) in this study were able to complete the prolonged reading task. Overall, there was no significant change in CPS, MORR and near text visual acuity following the prolonged task (p > 0.05). MORR was significantly correlated to age and near text visual acuity (p < 0.05). Conclusions: In this study, students with low vision were able to maintain their reading performance over a 30-minute prolonged reading task. Overall, there was no significant increase or decrease in reading performance following a prolonged reading task performed at their habitual close working distances but there were wide individual variations within the group.

Can students with low vision maintain sustained reading rates?

Purpose: Students with low vision may be disadvantaged when compared with their normally sighted peers, as they frequently work at very short working distances and need to use low vision devices. The aim of this study was to examine the sustained reading rates of students with low vision and compare them with their peers with normal vision. The effects of visual acuity, acuity reserve and age on reading rate were also examined. Method: Fifty-six students (10 to 16 years of age), 26 with low vision and 30 with normal vision were required to read text continuously for 30 minutes. Their position in the text was recorded at two-minute intervals. Distance and near visual acuity, working distance, cause of low vision, reading rates and reading habits were recorded. Results: A total of 80.7 per cent of the students with low vision maintained a constant reading rate during the 30 minutes of reading, although they read at approximately half the rate (104 wpm) compared with their normally sighted peers (195 wpm). Only four of the low vision subjects could not complete the reading task. Reading rates increased significantly with acuity reserve and distance and near visual acuity but there was no significant relationship between age and sustained reading rate. Conclusions: The majority of students with low vision were able to maintain appropriate reading rates to cope in integrated educational settings. Surprisingly only relatively few subjects (16 per cent) used their prescribed low vision devices even though the average accommodative demand was 9 D and generally, they revealed a greater dislike of reading compared to students with normal vision.

The effect of prolonged reading on visual functions and reading performance in students with low vision

This study is the first to investigate the effect of prolonged reading on reading performance and visual functions in students with low vision. The study focuses on one of the most common modes of achieving adequate magnification for reading by students with low vision, their close reading distance (proximal or relative distance magnification). Close reading distances impose high demands on near visual functions, such as accommodation and convergence. Previous research on accommodation in children with low vision shows that their accommodative responses are reduced compared to normal vision. In addition, there is an increased lag of accommodation for higher stimulus levels as may occur at close reading distance. Reduced accommodative responses in low vision and higher lag of accommodation at close reading distances together could impact on reading performance of students with low vision especially during prolonged reading tasks. The presence of convergence anomalies could further affect reading performance. Therefore, the aims of the present study were 1) To investigate the effect of prolonged reading on reading performance in students with low vision 2) To investigate the effect of prolonged reading on visual functions in students with low vision. This study was conducted as cross-sectional research on 42 students with low vision and a comparison group of 20 students with normal vision, aged 7 to 20 years. The students with low vision had vision impairments arising from a range of causes and represented a typical group of students with low vision, with no significant developmental delays, attending school in Brisbane, Australia. All participants underwent a battery of clinical tests before and after a prolonged reading task. An initial reading-specific history and pre-task measurements that included Bailey-Lovie distance and near visual acuities, Pelli-Robson contrast sensitivity, ocular deviations, sensory fusion, ocular motility, near point of accommodation (pull-away method), accuracy of accommodation (Monocular Estimation Method (MEM)) retinoscopy and Near Point of Convergence (NPC) (push-up method) were recorded for all participants. Reading performance measures were Maximum Oral Reading Rates (MORR), Near Text Visual Acuity (NTVA) and acuity reserves using Bailey-Lovie text charts. Symptoms of visual fatigue were assessed using the Convergence Insufficiency Symptom Survey (CISS) for all participants. Pre-task measurements of reading performance and accuracy of accommodation and NPC were compared with post-task measurements, to test for any effects of prolonged reading. The prolonged reading task involved reading a storybook silently for at least 30 minutes. The task was controlled for print size, contrast, difficulty level and content of the reading material. Silent Reading Rate (SRR) was recorded every 2 minutes during prolonged reading. Symptom scores and visual fatigue scores were also obtained for all participants. A visual fatigue analogue scale (VAS) was used to assess visual fatigue during the task, once at the beginning, once at the middle and once at the end of the task. In addition to the subjective assessments of visual fatigue, tonic accommodation was monitored using a photorefractor (PlusoptiX CR03™) every 6 minutes during the task, as an objective assessment of visual fatigue. Reading measures were done at the habitual reading distance of students with low vision and at 25 cms for students with normal vision. The initial history showed that the students with low vision read for significantly shorter periods at home compared to the students with normal vision. The working distances of participants with low vision ranged from 3-25 cms and half of them were not using any optical devices for magnification. Nearly half of the participants with low vision were able to resolve 8-point print (1M) at 25 cms. Half of the participants in the low vision group had ocular deviations and suppression at near. Reading rates were significantly reduced in students with low vision compared to those of students with normal vision. In addition, there were a significantly larger number of participants in the low vision group who could not sustain the 30-minute task compared to the normal vision group. However, there were no significant changes in reading rates during or following prolonged reading in either the low vision or normal vision groups. Individual changes in reading rates were independent of their baseline reading rates, indicating that the changes in reading rates during prolonged reading cannot be predicted from a typical clinical assessment of reading using brief reading tasks. Contrary to previous reports the silent reading rates of the students with low vision were significantly lower than their oral reading rates, although oral and silent reading was assessed using different methods. Although the visual acuity, contrast sensitivity, near point of convergence and accuracy of accommodation were significantly poorer for the low vision group compared to those of the normal vision group, there were no significant changes in any of these visual functions following prolonged reading in either group. Interestingly, a few students with low vision (n =10) were found to be reading at a distance closer than their near point of accommodation. This suggests a decreased sensitivity to blur. Further evaluation revealed that the equivalent intrinsic refractive errors (an estimate of the spherical dioptirc defocus which would be expected to yield a patient’s visual acuity in normal subjects) were significantly larger for the low vision group compared to those of the normal vision group. As expected, accommodative responses were significantly reduced for the low vision group compared to the expected norms, which is consistent with their close reading distances, reduced visual acuity and contrast sensitivity. For those in the low vision group who had an accommodative error exceeding their equivalent intrinsic refractive errors, a significant decrease in MORR was found following prolonged reading. The silent reading rates however were not significantly affected by accommodative errors in the present study. Suppression also had a significant impact on the changes in reading rates during prolonged reading. The participants who did not have suppression at near showed significant decreases in silent reading rates during and following prolonged reading. This impact of binocular vision at near on prolonged reading was possibly due to the high demands on convergence. The significant predictors of MORR in the low vision group were age, NTVA, reading interest and reading comprehension, accounting for 61.7% of the variances in MORR. SRR was not significantly influenced by any factors, except for the duration of the reading task sustained; participants with higher reading rates were able to sustain a longer reading duration. In students with normal vision, age was the only predictor of MORR. Participants with low vision also reported significantly greater visual fatigue compared to the normal vision group. Measures of tonic accommodation however were little influenced by visual fatigue in the present study. Visual fatigue analogue scores were found to be significantly associated with reading rates in students with low vision and normal vision. However, the patterns of association between visual fatigue and reading rates were different for SRR and MORR. The participants with low vision with higher symptom scores had lower SRRs and participants with higher visual fatigue had lower MORRs. As hypothesized, visual functions such as accuracy of accommodation and convergence did have an impact on prolonged reading in students with low vision, for students whose accommodative errors were greater than their equivalent intrinsic refractive errors, and for those who did not suppress one eye. Those students with low vision who have accommodative errors higher than their equivalent intrinsic refractive errors might significantly benefit from reading glasses. Similarly, considering prisms or occlusion for those without suppression might reduce the convergence demands in these students while using their close reading distances. The impact of these prescriptions on reading rates, reading interest and visual fatigue is an area of promising future research. Most importantly, it is evident from the present study that a combination of factors such as accommodative errors, near point of convergence and suppression should be considered when prescribing reading devices for students with low vision. Considering these factors would also assist rehabilitation specialists in identifying those students who are likely to experience difficulty in prolonged reading, which is otherwise not reflected during typical clinical reading assessments.

Visual field size criteria for mobility rehabilitation referral

Purpose. To investigate evidence-based visual field size criteria for referral of low-vision (LV) patients for mobility rehabilitation. Methods. One hundred and nine participants with LV and 41 age-matched participants with normal sight (NS) were recruited. The LV group was heterogeneous with diverse causes of visual impairment. We measured binocular kinetic visual fields with the Humphrey Field Analyzer and mobility performance on an obstacle-rich, indoor course. Mobility was assessed as percent preferred walking speed (PPWS) and number of obstacle-contact errors. The weighted kappa coefficient of association (κr) was used to discriminate LV participants with both unsafe and inefficient mobility from those with adequate mobility on the basis of their visual field size for the full sample and for subgroups according to type of visual field loss and whether or not the participants had previously received orientation and mobility training. Results. LV participants with both PPWS <38% and errors >6 on our course were classified as having inadequate (inefficient and unsafe) mobility compared with NS participants. Mobility appeared to be first compromised when the visual field was less than about 1.2 steradians (sr; solid angle of a circular visual field of about 70° diameter). Visual fields <0.23 and 0.63 sr (31 to 52° diameter) discriminated patients with at-risk mobility for the full sample and across the two subgroups. A visual field of 0.05 sr (15° diameter) discriminated those with critical mobility. Conclusions. Our study suggests that: practitioners should be alert to potential mobility difficulties when the visual field is less than about 1.2 sr (70° diameter); assessment for mobility rehabilitation may be warranted when the visual field is constricted to about 0.23 to 0.63 sr (31 to 52° diameter) depending on the nature of their visual field loss and previous history (at risk); and mobility rehabilitation should be conducted before the visual field is constricted to 0.05 sr (15° diameter; critical).

Diversity in action : minority group media and social change

My thesis consists of a creative work plus an exegesis. This exegesis uses case study research to investigate three Brisbane-based media organisations and the role they play in encouraging social inclusion and other positive social change for specific disadvantaged and stigmatised minority groups. Bailey, Cammaerts and Carpentier’s theoretical approach to alternative media forms the basis of this research. Bailey et al. (2008, p. 156) view alternative media organisations as having four important roles, two media-centred and two society-centred, which must all be considered to best understand them: • serving their communities • acting as an alternative to mainstream media discourses • promoting and advocating democratisation in the media and through the media in society • functioning as a crossroads in civil society. The first case study, about community radio station 4RPH (Radio for the Print Handicapped), centres on promoting social inclusion for people with a print disability through access to printed materials (primarily mainstream print media) in an audio format. The station also provides important opportunities for members of this group to produce media and, to a lesser extent, provides disability-specific information and discussions. The second case study, about gay print and online magazine Queensland Pride, focuses on promoting social inclusion and combating the discrimination and repression of people who identify as lesbian, gay, bisexual or transgender. Central issues include the representation (including sexualised representation) of a subculture and niche target market, and the impact of commercialisation on this free publication. The third case study, about community radio station 98.9FM, explores the promotion of social inclusion for peoples whose identity, cultures, issues, politics and contributions are often absent or misrepresented in the mainstream media. This radio station provides “a first level of service” (Meadows & van Vuuren, 1998, p. 104) to these people, but also informs and entertains those in the majority society. The findings of this research suggest that there are two key mechanisms that help these media organisations to effect social change: first, strengthening the minority community and serving its needs, and second, fostering connections with the broader society.

Prevalence of chronic ocular diseases in a genetic isolate : the Norfolk Island Eye Study (NIES)

Purpose: Over 40% of the permanent population of Norfolk Island possesses a unique genetic admixture dating to Pitcairn Island in the late 18 th century, with descendents having varying degrees of combined Polynesian and European ancestry. We conducted a population-based study to determine the prevalence and causes of blindness and low vision on Norfolk Island. Methods: All permanent residents of Norfolk Island aged ≥ 15 years were invited to participate. Participants completed a structured questionnaire/interview and underwent a comprehensive ophthalmic examination including slit-lamp biomicroscopy. Results: We recruited 781 people aged ≥ 15, equal to 62% of the permanent population, 44% of whom could trace their ancestry to Pitcairn Island. No one was bilaterally blind. Prevalence of unilateral blindness (visual acuity [VA] < 6/60) in those aged ≥ 40 was 1.5%. Blindness was more common in females (P=0.049) and less common in people with Pitcairn Island ancestry (P<0.001). The most common causes of unilateral blindness were age-related macular degeneration (AMD), amblyopia, and glaucoma. Five people had low vision (Best-Corrected VA < 6/18 in better eye), with 4 (80%) due to AMD. People with Pitcairn Island ancestry had a lower prevalence of AMD (P<0.001) but a similar prevalence of glaucoma to those without Pitcairn Island ancestry. Conclusions: The prevalence of blindness and visual impairment in this isolated Australian territory is low, especially amongst those with Pitcairn Island ancestry. AMD was the most common cause of unilateral blindness and low vision. The distribution of chronic ocular diseases on Norfolk Island is similar to mainland Australian estimates.

Visually impaired drivers who use bioptic telescopes : self-assessed driving skills and agreement with on-road driving evaluation

Purpose. To compare self-assessed driving habits and skills of licensed drivers with central visual loss who use bioptic telescopes to those of age-matched normally sighted drivers, and to examine the association between bioptic drivers' impressions of the quality of their driving and ratings by a “backseat” evaluator. Methods. Participants were licensed bioptic drivers (n = 23) and age-matched normally sighted drivers (n = 23). A questionnaire was administered addressing driving difficulty, space, quality, exposure, and, for bioptic drivers, whether the telescope was helpful in on-road situations. Visual acuity and contrast sensitivity were assessed. Information on ocular diagnosis, telescope characteristics, and bioptic driving experience was collected from the medical record or in interview. On-road driving performance in regular traffic conditions was rated independently by two evaluators. Results. Like normally sighted drivers, bioptic drivers reported no or little difficulty in many driving situations (e.g., left turns, rush hour), but reported more difficulty under poor visibility conditions and in unfamiliar areas (P < 0.05). Driving exposure was reduced in bioptic drivers (driving 250 miles per week on average vs. 410 miles per week for normally sighted drivers, P = 0.02), but driving space was similar to that of normally sighted drivers (P = 0.29). All but one bioptic driver used the telescope in at least one driving task, and 56% used the telescope in three or more tasks. Bioptic drivers' judgments about the quality of their driving were very similar to backseat evaluators' ratings. Conclusions. Bioptic drivers show insight into the overall quality of their driving and areas in which they experience driving difficulty. They report using the bioptic telescope while driving, contrary to previous claims that it is primarily used to pass the vision screening test at licensure.