Reading, computer use, and other near activities can be difficult for some individuals because of frequent symptoms of asthenopia, perceptual distortions, and reduced comprehension.1–5 In the presence of normal visual acuity, visual discomfort has been associated with disorders of accommodation and vergence.6 Two surveys, one developed by Convergence Insufficiency Treatment Trial Group7–10 and the other developed by Conlon et al.11 can measure the patient’s perception of chronic visual discomfort associated with anomalies of accommodation and vergence.9,12,13 These surveys require the patient to recall the frequency and severity of his or her experience of visual discomfort and then make a rating on a Likert scale. Patients have been found to reliably report symptoms of visual discomfort in both short- and long-term recall paradigms.4,8,9
In contrast to using surveys to measure patient recall of symptoms, research studies have not attempted to elicit symptoms during testing of accommodation or vergence using a survey instrument to aid in the diagnosis or treatment of binocular disorders. Hokoda14 investigated the prevalence of binocular disorders in pre-presbyopic patients presenting to an optometry clinic and used symptoms elicited during testing similar to those reported in the case history as one of the criteria that can be used in diagnostic classification. The study found prevalence rates similar to those reported in the literature for convergence insufficiency and strabismus. However, Hokoda14 did not use a survey scale to quantify the severity and frequency of symptoms and did report the number of patients who had symptoms elicited during the case history but not during tests of accommodation and vergence. It would be of interest for the eye care practitioner to have a greater understanding of chronic symptoms reported in a case history and acute symptoms reported during testing of accommodation and vergence to determine if this information can aid in the diagnosis and treatment of disorders of accommodation and vergence. When the results of a binocular vision (BV) examination are equivocal, clinicians often consider testing-related symptoms to help determine a diagnosis (e-mail from M. Scheiman, email@example.com, April 2013).
Acute symptoms elicited during a binocular examination provide direct support for patient complaints of asthenopia while doing near work, but this method requires considerable time and resources to assess. In addition, acute symptoms are often used when treating accommodation or vergence disorder with lenses or prisms where the practitioner asks the patient whether the lens reduced asthenopia.15,16 Developing a reliable and valid acute symptom scale could also aid the practitioner when making treatment decisions. The purpose of this study was to examine how well measures of chronic visual discomfort symptoms can accurately predict acute visual discomfort symptoms. We applied the survey developed by Conlon et al. and the Campbell Interest and Skill Survey (CISS) to assess reports of chronic symptoms of visual discomfort. To assess acute chronic symptoms, surveys were conducted before, during, and after assessments of accommodation and vergence function. These reports of both chronic and acute visual discomfort symptoms were then compared.
Thirty-nine participants were recruited from the Western University of Health Sciences, a private institution that consists of colleges of osteopathic medicine, allied health professions, pharmacy, graduate nursing, veterinary medicine, dental medicine, optometry, podiatric medicine, and biomedical science. All participants were recruited in a first-year orientation class in which students from all graduate programs attended. All participants signed informed consent approved by the institutional review board at Western University.
Main eligibility criteria for this study included consenting adults between the ages of 18 to 30 years with no history of receiving treatment for a binocular disorder or corneal refractive surgery (LASIK). Participants were not taking medications that would affect accommodative function, including antianxiety drugs, antiarrhythmic agents, anticholinergics, or tricyclic antidepressants. They were screened by questionnaire for ocular disease as well as multiple sclerosis, Graves thyroid disease, myasthenia gravis, diabetes, Parkinson disease, epilepsy, head trauma (including any concussion), deafness, and stuttering. If they had corrected vision, they wore corrective lenses during testing and contact lenses during autorefraction recording. Their visual acuity was 20/25 or better in each eye. Uncorrected refractive error exclusion criteria included (1) hyperopia greater than or equal to 1.25 diopters (D), myopia greater than or equal to 0.50 D, astigmatism or anisometropia greater than 1.00 D. All had stereopsis of 70 seconds of arc or better on the Randot Stereotest. If refractive error had been recently corrected by either glasses or contact lens, the participants were required to be wearing their new correction for at least a month before testing was performed. A total of 39 students completed the surveys and the binocular assessment of accommodation and vergence. There were 12 males and 25 females; sex was not recorded for two participants.
Testing was completed in two visits. At the first, participants were screened to meet eligibility criteria. A binocular examination was performed at the second visit.
Chronic Symptom Assessment
The survey administered was based on the questionnaire developed by Conlon et al.11 and consists of 23 items with a four-point scale: 0, event never occurs; 1, occasionally, a couple of times a year; 2, often, every few weeks; and 3, almost always (Table 1). The CISS7–10 consists of 15 items with a five-point scale: 0, never; 1, not very often, infrequently; 2, sometimes; 3, fairly often; 4, always (Table 2). From a Rasch item analysis, Borsting et al.17 found four symptom clusters in the Conlon et al.11 survey that related to movement/fading, blur/diplopia, headache/soreness, and reading performance (Table 1). A recent study divided the CISS items into performance (items 4 to 6, 9, 14, and 15) and eye related (items 1 to 3, 7, 8, and 10 to 13).18
The Conlon et al.11 survey was administered during recruitment before participant screening. The CISS was administered at the first visit. The time between the chronic symptom assessment at the screening visit and the acute symptom assessment at the binocular examination visit averaged 14.5 days (SD, 14.6), with 75% of the sample completed both visits in a 2-week period.
Acute Symptom Assessment
Two measures were used to assess acute symptoms: a questionnaire of overall symptoms before and after binocular examination (Pre- and Following-exam Symptom Survey) and general discomfort after each evaluation during binocular examination (General Discomfort Survey).
After a control accommodation facility test with ±0.12 D lenses and before binocular examination measuring accommodation and vergence function, participants were asked four questions to establish a baseline level of discomfort. These questions addressed (1) comfort level during the last test; (2) visual distortions or movement; (3) discomfort caused by overhead lights; and (4) presence of headache symptoms (Fig. 1 to view survey), and participants were required to rate their level of discomfort on a five-point scale, with 1 corresponding to no symptom and 5 corresponding to severe symptoms. Participants’ ratings were summed across all four questions to produce an initial Pre-exam score. These questions were repeated at the end of the session, and the scores were summed to determine a Following-exam symptom score. The difference between the Pre-exam score and the Following-exam score was calculated as a postexamination score.
The General Discomfort Survey involved participants rating their general discomfort on a four-point Likert scale (0, no discomfort; 1, mild discomfort; 2, moderate discomfort; 3, severe discomfort) after each binocular test. An overall General Symptom Score was calculated by summing a participant’s discomfort ratings after measurements of vergence base-in, vergence base-out, near point of convergence, vergence facility, amplitude of accommodation, accommodation facility, and amplitude-scaled accommodation facility during binocular examination.
Each student received an evaluation of accommodation and vergence conducted by two of the researchers (C.L. and E.C.).15 Tests were performed in the following sequence. Vergence was evaluated with five tests: (1) a cover test at 6 m and 40 cm with prism neutralization to assess phoria; (2) prism bar negative fusional vergence (NFV) and positive fusional vergence (PFV) at 40 cm; (3) near point of convergence using an Aston Rule with reduced Snellen letters (NPC); (4) vergence facility at 40 cm (12 BO/3 BI); and (5) fixation disparity using Saladin card at 40 cm. Accommodation was evaluated with four tests: (1) posture of accommodation using the monocular estimation method (MEM); (2) amplitude of accommodation (push-up method) OD, OS, OU; (3) monocular and binocular accommodative facility (AF) using ±2.00 flippers at 40 cm for 1 minute OD, OS, OU; and (4) amplitude-scaled facility that is a binocular test where the test distance and flipper power are based on the amplitude of accommodation.19
At the beginning of the binocular examination, the participant performed the AF test with ±0.12-D lenses. Baseline symptoms were assessed after this control test.
We analyzed the data using Likert scaling and binary logistic regression. These approaches allowed us to examine how accurately items on the chronic symptom surveys predicted the outcome on assessments of acute symptoms. Participants were categorized as being in either a High or Low Post-exam symptom group based on postexamination symptom scores. The cutoff value was one SD above the mean at the preexamination symptom assessment. Participants were categorized as being in either the High or Low General symptom group based on the mean split of the General Symptom Score.
Rating consistency was assessed by comparing questions from the two acute symptom surveys. The first question from the four-item Pre- and Following-Exam Symptom Survey asked about comfort level and is similar to the General Symptom item. Responses to both items were made at the beginning and end of the binocular examination. Spearman rank correlations between items were used rather than reliability coefficients because ratings were made on different ordinal scales, one with a four-point and the other a five-point rating.
Tables 3 and 4 present the acute and chronic symptom scores for the sample. The highest average symptom scores from the Conlon survey related to reading performance. The questions with the highest average from the CISS pertained to eye-related symptoms.
Participant responses to similar items from the two acute symptom questionnaires were compared in a Spearman rank correlation. Ratings were significantly correlated at both baseline (Rho = 0.59, p = 0.0003) and after the examination (Rho = 0.36, p = 0.03), suggesting participants responded consistently.
A logistic regression was performed to examine how items on the Conlon questionnaire predicted postexamination classification (High or Low). The model included 37 participants, with one case missing because of failure to complete the Following-exam questionnaire and one participant failing to complete the Conlon questionnaire (Table 5). The model sufficiently fit the data, with good agreement between the observed and predicted outcomes (Hosmer and Lemeshow test, χ 2 7 = 7.075, p = 0.421) and significantly predicted postexamination classification (omnibus χ 2 5 = 13.039, p = 0.023). The model accounts for between 29.7% and 40.1% of the variance in postexamination performance, with 81.8% of the Low postexamination symptoms and 66.7% of the High postexamination symptoms successfully predicted. Overall, 75.7% of predictions were accurate. Table 6 gives the coefficients and Wald statistic for each of the predictor variables. Examination of the predictor variable indicated that only the Conlon questions pertaining to headaches and soreness reliably predicted the Post-exam symptom group (Wald = 5.586, df = 1, p = 0.018).
A similar logistic regression was performed, investigating how well the Conlon questionnaire predicts General symptom classification (High or Low). The model included 36 cases; two were missing because of patients not completing the General symptom questions and one participant failed to complete the Conlon questionnaire (Table 5). This model did not significantly predict general symptom groups (omnibus χ 2 5 = 7.274, p = n.s.).
Logistic regression analyses were similarly performed with the CISS questions. In the analysis of how well CISS items can predict postexamination symptom category, 38 cases were included, with one participant failing to complete the postexamination survey (Table 5). The full model was found to sufficiently fit the data (Hosmer and Lemeshow test, χ 2 8 = 12.262, p = 0.140) and significantly predicted postexamination classification (omnibus χ 2 2 = 10.271, p = 0.006). The model accounts for between 23.7% and 31.8% of the variance in postexamination performance, with 81.8% of the Low postexamination symptoms and 62.5% of the High postexamination symptoms successfully predicted and 73.7% of predictions being accurate. Examination of the predictor variables revealed that only the CISS questions in the eye symptom category reliably predicted the Post-exam symptom group (Wald = 5.194, df = 1, p = 0.023). Table 7 gives the coefficients and the Wald statistic for the two predictor variables.
The logistic regression model for CISS questions as predictors of General symptom categories included 37 cases (two participants did not complete the general symptom questionnaire; Table 5). The model sufficiently fit the data (Hosmer and Lemeshow test, χ 2 7 = 7.278, p = 0.400). The model significantly predicted the general symptom classification (omnibus χ 2 2 = 7.350, p = 0.025) and accounted for between 18.0% and 24.1% of the variance in the general symptom performance. The model indicated that 70.0% of Low general symptoms and 58.8% of High general symptoms were successfully predicted, with 64.9% of overall predictions being accurate. Only the CISS questions relating to eye discomfort symptoms (Table 2) reliably predicted the general symptom group (Wald = 4.802, df = 1, p = 0.028). Coefficients and the corresponding Wald statistics can be found in Table 8.
This study found that the Conlon and the CISS assessment tools are able to accurately predict about 75% of the participants’ postexamination symptom classification. Examination of the survey items reveals that questions on the Conlon survey pertaining to headache and soreness symptoms and those on the CISS pertaining to eye-related symptoms reliably predict the Post-exam symptom group. However, only the CISS was able to accurately predict the General symptom group categorization, with items addressing eye-related symptoms reliably predicting High or Low symptom groups.
To our knowledge, this is the first study that has compared acute with chronic symptoms in individuals with a broad range of symptoms. The strengths of our study would be the novel research design and the prospective design. The limitations of our study would be using only postgraduate college students and a limited sample size.
Only chronic symptom survey items pertaining to headache, soreness, and eye-related symptoms were predictive of acute symptoms of visual discomfort experienced by patients. Although items related to text distortion, diplopia, glare, and near work performance were not good correlates of acute symptoms, they may have a predictive value for specific accommodation or vergence functions. For example, Chase et al.12 found that amplitude-scaled facility performance correlated with soreness and headaches, diplopia, and text distortions.
Another consideration is that symptoms associated with text distortion do not occur as often as symptoms of soreness and headaches17,18 Symptoms that occur with greater frequency are more likely to be elicited during testing. In addition, reading performance–related symptoms would be unlikely to be elicited during testing because the tests of accommodation and vergence do not require extended reading of text. Thus, our initial results suggest that patients with chronic symptoms of headaches and soreness would be more likely to have acute symptoms during an evaluation of accommodation and vergence.
This study supports the continued use of chronic symptom surveys as a screening tool to identify young adults at risk for symptomatic binocular dysfunction. Further work is needed to determine the degree to which chronic symptom surveys can predict accommodation or vergence performance.
Stefanie A. Drew
California State University, Northridge
18111 Nordhoff St
Northridge, CA 91330
This research was supported by grant number R15EY015922 from the National Eye Institute, National Institutes of Health.
Received January 5, 2013; accepted May 20, 2013.
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Keywords:© 2013 American Academy of Optometry
visual discomfort; asthenopia; symptom survey CISS; convergence; symptoms