Accommodative and binocular vision dysfunctions in a Portuguese clinical population

Does the subjective response during the measurement of fusional reserves affect the clinical diagnosis?

INTRODUCTION

Fusional reserves differ with the method of measurement. The goal of this study was to compare the subjective and objective responses during the measurement of positive and negative fusional reserves using both step and ramp methods.

METHODS

A haploscopic system was used to measure fusional reserves. Eye movements were recorded using an EyeLink 1000 Plus eye tracker (SR Research). The stimulus disparity was changed to either mimic a prism bar (steps) or a Risley prism (ramp). Subjective responses were obtained by pressing a key on the keyboard, whereas objective break and recovery points were determined offline using a custom algorithm coded in Matlab.

RESULTS

Thirty-three adults participated in this study. For the ramp method, the subjective and objective responses were similar for the negative (break and recovery points (t(32) = -0.82, p = 0.42) and (t(32) = 0.42, p = 0.67), respectively) and positive fusional reserves (break and recovery points (U = -1.34, p = 0.18) and t(19) = -0.25, p = 0.81), respectively). For the step method, no significant differences in positive fusional reserves were observed when measured subjectively and objectively for the break (t(32) = 1.27, p = 0.21) or the recovery point (U = -2.02, Bonferroni-adjusted p = 0.04). For the negative fusional reserve, differences were not significant for either the break or recovery points (U = -0.10, p = 0.92 and t(19) = 1.17, p = 0.26, respectively).

CONCLUSION

Subjective and objective responses exhibited good agreement when measured with the ramp and step methods.

BCLA CLEAR Presbyopia: Epidemiology and impact

The global all-ages prevalence of epidemiologically-measured 'functional' presbyopia was estimated at 24.9% in 2015, affecting 1.8 billion people. This prevalence was projected to stabilise at 24.1% in 2030 due to increasing myopia, but to affect more people (2.1 billion) due to population dynamics. Factors affecting the prevalence of presbyopia include age, geographic location, urban versus rural location, sex, and, to a lesser extent, socioeconomic status, literacy and education, health literacy and inequality. Risk factors for early onset of presbyopia included environmental factors, nutrition, near demands, refractive error, accommodative dysfunction, medications, certain health conditions and sleep. Presbyopia was found to impact on quality-of-life, in particular quality of vision, labour force participation, work productivity and financial burden, mental health, social wellbeing and physical health. Current understanding makes it clear that presbyopia is a very common age-related condition that has significant impacts on both patient-reported outcome measures and economics. However, there are complexities in defining presbyopia for epidemiological and impact studies. Standardisation of definitions will assist future synthesis, pattern analysis and sense-making between studies.

Prevalence of Near-Vision-Related Symptoms in a University Population

The university population has high visual demands. It is therefore important to assess the prevalence of symptoms in these subjects, which may affect their academic performance. In this cross-sectional study, a randomized sample of 252 subjects from a university answered the Convergence Insufficiency Symptom Survey (CISS) questionnaire. In addition, questions were asked about blurred vision during and after near tasks, the number of hours per day spent in near vision, and whether or not they wore glasses. Furthermore, 110 subjects underwent an eye exam, including a refraction and accommodation assessment. The mean age of the subjects was 28.79 ± 11.36 years, 62.3% reported wearing glasses, and on average 7.20 ± 2.92 hours/day was spent in near vision. The mean of the CISS score was 18.69 ± 9.96, and according to its criteria, 38% of the subjects were symptomatic. Some symptoms were significantly (p < 0.05) more frequent in subjects wearing glasses. Accommodative dysfunctions were present in 30.9% of the subjects, the most common being insufficiency of accommodation. We emphasise the importance of assessing symptomatology during the clinical examination in this group of subjects, as they spend many hours a day in near vision, as well as assessing accommodation, binocular vision, and the ergonomic work environment, which may be at the origin of the symptoms, in addition to the need to wear glasses.

Frequency and associated factors of accommodation and non-strabismic binocular vision dysfunction among medical university students

AIM

To investigate the frequency and associated factors of accommodation and non-strabismic binocular vision dysfunction among medical university students.

METHODS

Totally 158 student volunteers underwent routine vision examination in the optometry clinic of Guangxi Medical University. Their data were used to identify the different types of accommodation and non-strabismic binocular vision dysfunction and to determine their frequency. Correlation analysis and logistic regression were used to examine the factors associated with these abnormalities.

RESULTS

The results showed that 36.71% of the subjects had accommodation and non-strabismic binocular vision issues, with 8.86% being attributed to accommodation dysfunction and 27.85% to binocular abnormalities. Convergence insufficiency (CI) was the most common abnormality, accounting for 13.29%. Those with these abnormalities experienced higher levels of eyestrain (χ2=69.518, P<0.001). The linear correlations were observed between the difference of binocular spherical equivalent (SE) and the index of horizontal esotropia at a distance (r=0.231, P=0.004) and the asthenopia survey scale (ASS) score (r=0.346, P<0.001). Furthermore, the right eye's SE was inversely correlated with the convergence of positive and negative fusion images at close range (r=-0.321, P<0.001), the convergence of negative fusion images at close range (r=-0.294, P<0.001), the vergence facility (VF; r=-0.234, P=0.003), and the set of negative fusion images at far range (r=-0.237, P=0.003). Logistic regression analysis indicated that gender, age, and the difference in right and binocular SE did not influence the emergence of these abnormalities.

CONCLUSION

Binocular vision abnormalities are more prevalent than accommodation dysfunction, with CI being the most frequent type. Greater binocular refractive disparity leads to more severe eyestrain symptoms.

Accommodative Facility and Response Time before and after Computer Task of Varying Durations in Young Adults

Aim

To investigate the changes in near accommodative facility and response time in young adults following computer work of 30 minutes and 1 hour in duration.

Methods

A total of 50 young adults (37 females, 13 males) with mean age of 20.68 ± 1.33 years were included in this experimental study. Monocular near accommodative facility was measured using ±2.00 Dioptre Sphere (DS) flipper at 40 cm using the N6 (the smallest print size that can be read by an individual with normal visual acuity) target before and after two reading tasks. Both pre- and post-task measurements were video recorded using a smart phone and the number of cycles per minute, positive response time (time taken to stimulate accommodation), and negative response time (time taken to relax accommodation) were calculated from the video recording. Data were analysed using SPSS Version 22.0.

Results

Out of the 50 participants, 29 were emmetropes (Mean SER: 0.16 ± 0.29 D), and 21 were myopes (Mean SER: -1.89 ± 1.16 D). The mean pre-task accommodative facility was 6.79 ± 3.52 cycles per minute, and the post-task accommodative facility was 6.25 ± 3.65 cycles per minute (p = 0.10) for the 30-minutes task and 5.76 ± 3.89 cycles per minute (p = 0.01) for 1-hour task. The mean pre-task positive response time was 2.87 ± 1.55 seconds, and the post-task positive response times for 30 minutes and 1 hour were 2.86 ± 1.67 seconds (p = 0.88) and 2.98 ± 2.33 seconds (p = 0.42), respectively. The mean pre-task negative response time was 8.77 ± 8.83 seconds, and the post-task negative response times for 30 minutes and 1 hour task were 11.83 ± 14.28 seconds (p = 0.16) and 14.72 ± 17.32 seconds (p = 0.03), respectively.

Conclusion

Monocular near accommodative facility was significantly reduced, and negative response time was delayed following 1 hour of computer work.

Vision Quality of Life with Time Survey: Normative Data and Repeatability

Purpose

To develop a novel Vision Quality of Life (QoL) survey that emphasizes the amount of time a visual activity can be performed before symptoms occur.

Methods

The Vision Quality of Life with Time (VisQuaL-T) survey was developed with 10 daily activities and a list of common visual symptoms. Participants were recruited from a university campus. Participants were not excluded based on binocular impairments to obtain a normative dataset. Participants were instructed to denote when they first experience symptoms within certain time ranges. If participants did not engage in one of the 10 activities, they were instructed to denote "N/A". A composite score (range 0-3) was determined by only accounting for the questions that were answered.

Results

The normative data cohort had a sample size of 376 participants and the repeatability cohort had 54 participants. The normative, test, and retest datasets had a mean composite score of 2.47±0.54, 2.69±0.42, and 2.67±0.49 and 95% confidence interval of 2.38-2.71, 2.58-2.81, 2.54-2.80, respectively. There was good reliability and high correlation between the test and retest timepoints with an ICC of 0.825 and a Pearson correlation coefficient of 0.839 in the repeatability cohort. The normative data cohort showed good internal consistency with a Cronbach's alpha value of 0.803. Test and retest timepoints showed no statistical significance among the individual questions (p > 0.1).

Conclusion

A lower bound score of 2.4 can potentially be used to differentiate visually normal and symptomatic participants. Statistical analysis showed the survey is repeatable and reliable. Using time as a metric for assessing symptomology could be a useful method for identifying patients with QoL issues and for assessing effectiveness of binocular vision, accommodative, and eye movement treatments.

Feasibility of measuring fusional vergence amplitudes objectively

Two tests to measure fusional vergence amplitudes objectively were developed and validated against the two conventional clinical tests. Forty-nine adults participated in the study. Participants' negative (BI, base in) and positive (BO, base out) fusional vergence amplitudes at near were measured objectively in an haploscopic set-up by recording eye movements with an EyeLink 1000 Plus (SR Research). Stimulus disparity changed in steps or smoothly mimicking a prim bar and a Risley prism, respectively. Break and recovery points were determined offline using a custom Matlab algorithm for the analysis of eye movements. Fusional vergence amplitudes were also measured with two clinical tests using a Risley prism and a prism bar. A better agreement between tests was found for the measurement of BI than for BO fusional vergence amplitudes. The means ± SD of the differences between the BI break and recovery points measured with the two objective tests were -1.74 ± 3.35 PD and -1.97 ± 2.60 PD, respectively, which were comparable to those obtained for the subjective tests. For the BO break and recovery points, although the means of the differences between the two objective tests were small, high variability between subjects was found (0.31 ± 6.44 PD and -2.84 ± 7.01 PD, respectively). This study showed the feasibility to measure fusional vergence amplitudes objectively and overcome limitations of the conventional subjective tests. However, these tests cannot be used interchangeably due to their poor agreement.