Chris Chase

Visual discomfort and objective measures of static accommodation.

Purpose. Accommodation insufficiency and fatigue have been associated with near work visual discomfort symptoms, but clinical measures of accommodation amplitude suggest insufficiency is uncommon and often not weak enough to cause symptoms. However, recent studies show that the clinical push-up test used to measure amplitude overestimates accommodative function. This study uses an open-field autorefractor to measure accommodative stimulus-response functions objectively in college students with and without near work induced discomfort symptoms. Methods. Using a Grand-Seiko WAM 5500 autorefractor, 2 min recordings were made each at five viewing distances (0 to 5 D) to measure an accommodative response function. Visual discomfort symptoms were assessed using the Conlon survey. Results. A strong and positive correlation between accommodative lag and visual discomfort symptoms was found under near work conditions. The prevalence of accommodative insufficiency was much higher than estimated by clinical measures. Conclusions. Accommodative insufficiency and fatigue should be defined and described by objective methods using extended viewing times to assess function.

Accommodation response and visual discomfort

Although visual discomfort symptoms associated with near work have been correlated with clinical measures of accommodation, studies using objective recordings have not found corresponding deficits in accommodative function. One problem with previous studies is that accommodation measures have been too brief to assess accommodative fatigue. This study examined steady state accommodative responses among a college population with visual discomfort, over a 90‐s time period. Thirty‐one participants were grouped into high (n = 15) or low visual discomfort groups (n = 16) based on their scores on the Conlon Visual Discomfort Survey. Using the WAM‐5500 autorefractor, accommodation responses were recorded at 5 Hz for two consecutive minutes at five viewing distances. The results showed a significant interaction between the high and low discomfort groups over time in accommodation response. The high discomfort group showed an increase in accommodative lag, whereas the low discomfort group had a stable response. Our study suggests that the high visual discomfort group is characterized by accommodative fatigue, with a higher lag of accommodation developing at a near viewing distance over time.

Measuring visual discomfort in college students.

Purpose. The purpose of this study was to measure the distribution visual discomfort symptoms in a group of college students using a survey developed by Conlon et al. and to analyze the type and frequency of symptoms in the subjects who display moderate to high amounts of visual discomfort to ascertain if this condition occurs along a single dimension or consists of different subtypes. Methods. Members of the research team administered a survey of visual discomfort developed by Conlon et al. (Conlon et al., Vis Cogn 1999;6:637–666) to 571 college students at the Claremont Colleges University over a 2-year period. The survey for measuring visual discomfort developed by Conlon consists of 23 items with a four-point scale (0 to 3) (see below). Scores on the survey can range from 0 to 69. Results. A Rasch analysis of the survey results showed that a single symptom dimension accounted for 73.5% of the variance. A principle component analysis of the residual variance from the Rasch analysis yielded three factors: factor 1 was associated with text movement and fading; factor 2 was associated with headache and soreness; and factor 3 was associated primarily with blur and diplopia. Conclusions. The survey developed by Conlon is an appropriate measure of visual discomfort. In addition to the single dimension reported by Conlon, we found that some subjects with moderate to high amounts of visual discomfort tended to report particular types of symptoms. These results suggest that there may be multiple etiologies of visual discomfort.

Longitudinal study of visual discomfort symptoms in college students.

Purpose. To determine the variation of visual discomfort symptom reporting in a group of college students over a 1 year period. Methods. Subjects were screened for visual acuity and uncorrected refractive error before participating in the study. A survey of visual discomfort developed by Conlon et al., Vis Cogn 1999;6:637–666, and the Convergence Insufficiency Symptom Survey (CISS) were administered to a group of 23 college students twice with approximately 1 year between administrations. All subjects also completed two clinical assessments of accommodation and vergence. Results. The mean time between administrations of the symptom surveys was 13 months. There was no clinically significant mean difference between the first and second administration of both visual discomfort surveys. The intraclass correlation coefficient was 0.82 for the Conlon et al., Vis Cogn 1999;6:637–666 survey and 0.85 for the CISS. The 95% limits of agreement for the Conlon et al., Vis Cogn 1999;6:637–666 survey was −18.44, 17.92 and for the CISS was −14.36, 13.36. The intraclass correlation coefficient values for the optometric tests ranged from 0.38 to 0.83. Conclusions. Visual discomfort symptoms were found to be stable in the majority of young college students over a 1 year period. However, a minority of students showed large variability between the two administrations of the surveys.

Measuring near-induced transient myopia in college students with visual discomfort.

Purpose. Visual discomfort is a common problem, and our previous research indicated that 17% of college students experience moderate to high levels of discomfort when reading or studying. There have been several visual factors associated with visual discomfort, and in this study, we focused on measuring the near-induced transient myopia response in a group of college students with significant visual discomfort. Methods. Visual discomfort was evaluated with a survey developed by Conlon et al. (Conlon et al., Visual Cogn 1999;6:637–663). Twelve college students with high visual discomfort (scoring 1 SD higher than the mean value) and 12 college students with low visual discomfort (scoring within 0.5 SD of the mean value) participated in the study. All students had 20/25 or better visual acuity, no strabismus, and no significant uncorrected refractive error. All refractive error and accommodative measurements were made with the WAM-5500 autorefractor. A pretask distance refraction at 6 m was taken for 60 s, and then the students read a story for 10 min at 20 cm. After reading the passage, the posttask distance refraction was measured for 2 min at 6 m. Values for the pre- and posttask measures were averaged in 10-s blocks of time. Results. A mixed analysis of variance comparing discomfort group by pre- and postnear work distance refraction showed a significant interaction (p = 0.05). Comparing the means of the pre- and posttask distance refraction indicated that the high discomfort group showed no change in refractive error, but the low discomfort group showed a myopic shift of 0.13 diopter. Conclusions. A near-induced transient myopia response is not associated with high visual discomfort experienced by college students when reading or doing near work.

Behavioral and Emotional Problems Associated With Convergence Insufficiency in Children An Open Trial

Objective: This study investigated behavioral and emotional characteristics of children with convergence insufficiency (CI), before and after treatment with office-based vergence accommodative therapy (OBVAT). Method: Parents of 44 children ages 9 to 17 years with symptomatic CI completed the Conners 3 ADHD Index and the Child Behavior Checklist (CBCL) before and after OBVAT. Pre-treatment scores were compared with normative data and post-treatment scores were compared with baseline using the Wilcoxon sign rank test. Results: Following OBVAT, CI children showed a significant mean improvement (p < .0001, effect size of 0.58) on the Conners 3 ADHD Index with the largest changes occurring in the 23 children who scored the highest at baseline. On the CBCL, anxious/depressed, somatic, and internalizing problems improved significantly (p < .001, effect sizes of −0.36, −1.15, and −0.67, respectively). Conclusion: In an open trial, attention and internalizing problems improved significantly following treatment for CI.

Can chronic visual discomfort measures accurately predict acute symptoms

Purpose Several surveys exist to determine the severity and frequency of chronic symptoms related to visual discomfort. To our knowledge, there are no studies that investigate the potential of chronic visual discomfort ratings to predict acute discomfort symptoms that are experienced after tests of accommodation and vergence. We examined the ability of two measures of chronic visual discomfort symptoms to predict acute symptoms experienced. Methods The Conlon et al. and the convergence insufficiency symptom surveys were administered to 40 participants to assess chronic visual discomfort symptoms. Two measures were used to assess acute symptoms. The first consisted of four Likert-scaled questions relating to comfort level during last test, visual distortions or movement, discomfort caused by overhead lights, and presence of headache symptoms. These questions were asked before and after binocular examination, and the scores were used to generate a postexamination symptom score. The second measure of acute symptoms consisted of participants rating their general discomfort on a four-point Likert scale after each binocular test, and the ratings were summed to produce a General Symptom Score. Participants were then categorized into a high or low Post-exam symptom group and General symptom group. Data were analyzed with a binary logistic regression to determine whether the chronic surveys could predict acute symptom group classification. Results Approximately 75% of predictions were accurate for either chronic symptom survey. Headache, soreness, and eye-related questions were more reliable predictors of symptom acute outcome. Conclusions These data suggest that the Conlon and Convergence Insufficiency Symptom Survey (CISS) surveys are good predictors of acute symptoms induced during a binocular examination and validate the use of chronic symptom surveys as screening tools for symptomatic binocular dysfunction. Further investigation is required to determine predictability of accommodative or vergence performance.

ERGs and psychophysical thresholds in students with reading discomfort.

Purpose. Symptoms of reading discomfort include unpleasant somatic and perceptual effects, such as eye-strain, headache, and blurred text, despite normal visual acuity. Reading discomfort has been proposed to be the result of increased noise in the visual system. Several studies have suggested that the symptoms can be minimized by having the subject wear colored filters. Thus, there may be abnormal neural processing in the cone pathways. This study measured L- and M-cone isolating (1) ERGs and (2) psychophysical thresholds in normal and reading discomfort subjects to determine if cone processing was abnormal in the reading discomfort population. Methods. Twenty-two normal and nineteen reading discomfort college students took part in this study. The normal subjects had Conlon survey scores within 0.5 SD of the mean and the reading discomfort subjects had scores >1.5 SD above the mean. ERGs were determined for a range (5 to 15%) of L- and M-cone contrasts. Slopes were determined for the L- and M-cone ERG amplitudes for each subject. Psychophysical thresholds were determined with a 2AFC technique combined with a 3-up and 1-down staircase procedure that terminated after 18 reversals occurred. The threshold was calculated as the average of the last 8 reversals. Results. The average ERG slopes were not significantly different between the normal and reading discomfort groups (L-Cone, p = 0.086; M-Cone, p = 0.47). The L/M cone ratios for the slopes were not significantly different (p = 0.55). The log of the color contrast thresholds were not significantly different between the normal and reading discomfort groups (L-Cone, p = 0.97; M-Cone, p = 0.92). Conclusions. L- and M- cone ERG contrast gains and psychophysical estimates of color contrast thresholds were not significantly different. These results do not support the noisy visual system hypothesis of reading discomfort.

Tonic accommodation predicts closed-loop accommodation responses

The purpose of this study is to examine the potential relationship between tonic accommodation (TA), near work induced TA-adaptation and the steady state closed-loop accommodation response (AR). Forty-two graduate students participated in the study. Various aspects of their accommodation system were objectively measured using an open-field infrared auto-refractor (Grand Seiko WAM-5500). Tonic accommodation was assessed in a completely dark environment. The association between TA and closed-loop AR was assessed using linear regression correlations and t-test comparisons. Initial mean baseline TA was 1.84diopter (D) (SD±1.29D) with a wide distribution range (-0.43D to 5.14D). For monocular visual tasks, baseline TA was significantly correlated with the closed-loop AR. The slope of the best fit line indicated that closed-loop AR varied by approximately 0.3D for every 1D change in TA. This ratio was consistent across a variety of viewing distances and different near work tasks, including both static targets and continuous reading. Binocular reading conditions weakened the correlation between baseline TA and AR, although results remained statistically significant. The 10min near reading task with a 3D demand did not reveal significant near work induced TA-adaptation for either monocular or binocular conditions. Consistently, the TA-adaptation did not show any correlation with AR during reading. This study found a strong association between open-loop TA and closed-loop AR across a variety of viewing distances and different near work tasks. Difference between the correlations under monocular and binocular reading condition suggests a potential role for vergence compensation during binocular closed-loop AR.

Effect of treatment of symptomatic convergence insufficiency on reading in children: a pilot study: Treating convergence insufficiency

To evaluate the impact of treatment of symptomatic convergence insufficiency using office‐based vergence/accommodative therapy on reading skills in children.