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PubMed1992

The effect of orthoptic treatment upon the vergence adaptation mechanism.

This paper is a review of the research work that has been carried out over the past few years investigating the ability of the oculomotor system to adapt to prism-induced heterophoria. Our results show that subjects with normal binocular vision can adapt to horizontal and vertical prism-induced heterophorias whether fixating at distance or near. Further studies have shown that subjects with symptomatic abnormal binocular vision have an abnormal adaptation mechanism. Finally, we have found that when orthoptic treatment results in relief from the symptoms, there is an associated improvement in the subjects' ability to adapt to prism-induced heterophoria.

Adaptation, Ocular↗
PubMed1993

Visual symptoms and reading performance.

Clinical observation indicates that visual asthenopic symptoms are frequently associated with reading for long periods of time. We investigated the relation between visual symptoms and standard measures of reading performance in 78 university students. The number of asthenopic complaints increased during the reading phase of the experiment and decreased during the relaxation phase. Overall, a weak but significant negative correlation was found between number of symptoms and reading rate on the Nelson-Denny reading test. The most symptomatic subjects scored lower on vocabulary and comprehension than the least asthenopic subjects. A limited retrospective analysis revealed no reading performance differences between subjects having normal binocular vision and those showing a minimum binocular dysfunction; however, the dysfunctional subjects reported more visual symptoms. This study suggests that visual symptoms are a factor in reducing reading performance, particularly in very symptomatic individuals.

Adult↗
PubMed1998

Vision therapy to reduce abnormal nearwork-induced transient myopia.

After brief periods of nearwork, some younger patients complain of transient distance blur that is correlated with a transient pseudomyopic shift in their distance refraction. This phenomenon has recently been documented objectively. However, there is lack of objective documentation demonstrating the effects of conventional optometric vision therapy in symptomatic individuals manifesting this "abnormal nearwork-induced transient myopia" (ANITM). Five symptomatic subjects received 7 to 10 weeks (5 to 6 sessions) of accommodative facility vision therapy (i.e., lens flippers and Hart chart). Objective recording of their ANITM and its decay were taken before and after the vision therapy, using a Canon R-1 autorefractor. A daily log was maintained, describing qualitatively their nearwork-related symptomatology. After therapy, there was marked reduction of symptoms and considerable improvement in clinical accommodative facility measures, as well as improvement in the objective findings. These results demonstrate multi-faceted positive effects of optometric accommodative vision therapy in this diagnostic group of symptomatic individuals.

Accommodation, Ocular↗
PubMed2002

Performance and comfort on near-eye computer displays.

BACKGROUND: Very small high-resolution displays (SVGA, 800 x 600 pixels) worn near the eye and imaged to create a virtual image have potential as alternatives to traditional computer displays. METHODS: Twenty-two subjects performed text-based tasks on five displays: monocular virtual, binocular head-mounted virtual, hard copy, flat panel, and a small format portable display. Outcome measures included performance speed, symptoms, visual acuity, and heterophoria. In a second experiment, subjects performed a proscribed routine of head and body movements designed to elicit motion-related symptoms. RESULTS: Performance speed on monocular virtual was generally comparable with performances on flat panel and hard copy. Overall, performance speeds on the binocular virtual display were about 5% slower than normalized performances, 6.75% slower compared with the traditional flat panel and hard copy displays. Symptoms of eyestrain and blurry vision were significantly higher on monocular virtual than on other displays. No significant changes in visual acuity or heterophoria occurred with any of the displays. Motion-related symptoms with the head mounted near-eye display were not significantly different than with other displays tested. CONCLUSIONS: Performance and comfort on the near-eye displays in this study was more similar to traditional displays than in many previous studies with head mounted displays. This is likely due to lack of task movement, partial instead of full immersion, better display resolution, and concordance of the accommodative and vergence stimuli.

Adult↗
PubMed2006

Efficacy of a new warm moist air device on tear functions of patients with simple meibomian gland dysfunction.

PURPOSE: To evaluate the safety and efficacy of an original warm moist air device on tear functions and ocular surface of patients with simple meibomian gland dysfunction (MGD). METHODS: Fifteen patients with simple MGD and 20 healthy volunteers were recruited in an initial prospective interventional clinical trial to evaluate the safety and short-term effects of the warm moist air device. The device was applied to the eyes of the subjects for 10 minutes. Temperatures of the eye lids and corneas were measured with an infrared thermometer. Symptoms of ocular fatigue were scored using visual analog scales (VASs). Schirmer test, tear film break-up time (BUT), DR-1 tear film lipid layer interferometry, fluorescein staining, and rose bengal staining were also performed before and after the application of the eye steamer. After the initial study, another 2-week prospective clinical trial was carried out in 10 patients with MGD who received the warm moist air treatment. Ten other patients were also recruited and received warm compress treatment with hot towels for 2 weeks to evaluate the long-term effects of the warm moist air device and the warm compresses on tear film lipid layer thickness and ocular surface health. The warm moist air device and the warm compresses were applied for 10 minutes twice a day. The changes in VAS scores for symptoms, BUT values, fluorescein, and rose bengal staining scores were examined before and after each treatment during the second trial. RESULTS: VAS scores of ocular fatigue improved significantly with short- and long-term applications of the warm moist air device in both studies. The mean corneal surface and eye lid temperatures showed significant elevation within safe limits 10 minutes after the moist air application. The mean BUT prolonged significantly in the patients receiving warm moist air applications but did not change significantly in those treated with warm compresses. DR-1 tear film lipid layer interference showed evidence of lipid expression in the patients and controls, with thickening of the tear film lipid layer after 10 minutes of warm moist air device use. In the 2-week trial, tear film lipid layer thickness increased in both warm moist air device and warm compress groups, with a greater extent of increase in the warm moist air device group. CONCLUSION: Warm moist air device use provided symptomatic relief of ocular fatigue and improvement of tear stability in patients with MGD. The new warm moist air device seems to be a safe and promising alternative in the treatment of MGD.

Aged↗
PubMed2005

The development of a symptom questionnaire for assessing virtual reality viewing using a head-mounted display.

PURPOSE: Virtual reality devices, including virtual reality head-mounted displays, are becoming increasingly accessible to the general public as technological advances lead to reduced costs. However, there are numerous reports that adverse effects such as ocular discomfort and headache are associated with these devices. To investigate these adverse effects, questionnaires that have been specifically designed for other purposes such as investigating motion sickness have often been used. The primary purpose of this study was to develop a standard questionnaire for use in investigating symptoms that result from virtual reality viewing. In addition, symptom duration and whether priming subjects elevates symptom ratings were also investigated. METHODS: A list of the most frequently reported symptoms following virtual reality viewing was determined from previously published studies and used as the basis for a pilot questionnaire. The pilot questionnaire, which consisted of 12 nonocular and 11 ocular symptoms, was administered to two groups of eight subjects. One group was primed by having them complete the questionnaire before immersion; the other group completed the questionnaire postviewing only. Postviewing testing was carried out immediately after viewing and then at 2-min intervals for a further 10 min. RESULTS: Priming subjects did not elevate symptom ratings; therefore, the data were pooled and 16 symptoms were found to increase significantly. The majority of symptoms dissipated rapidly, within 6 min after viewing. Frequency of endorsement data showed that approximately half of the symptoms on the pilot questionnaire could be discarded because <20% of subjects experienced them. CONCLUSIONS: Symptom questionnaires to investigate virtual reality viewing can be administered before viewing, without biasing the findings, allowing calculation of the amount of change from pre- to postviewing. However, symptoms dissipate rapidly and assessment of symptoms needs to occur in the first 5 min postviewing. Thirteen symptom questions, eight nonocular and five ocular, were determined to be useful for a questionnaire specifically related to virtual reality viewing using a head-mounted display.

Adult↗
PubMed2006

Susceptibility to induced visual discomfort during the menstrual cycle while viewing a visual display unit.

PURPOSE: Consistent variations in reports of visual discomfort during the female menstrual cycle are found when virtual reality headsets are used to display moving images. Because little is known about the influence of this cycle on susceptibility to visual discomfort in other situations, we performed a laboratory study using an intensive visual task. METHODS: Twelve female participants, with normal-length menstrual cycles, completed the study. This required them to play a computer game for 30 minutes while viewing the screen through -2.00-D lenses. Questionnaires were used to record symptom changes; visual acuity and near points of accommodation (NPA) and convergence (NPC) were also recorded both before and after the game. The participants performed this task on designated days (5, 12, 19, and 26) of their menstrual cycle chosen because they fall in line with peaks and troughs of ovarian hormone levels. Cycle phase was confirmed by the measurement of salivary estradiol and progesterone levels. RESULTS: The task performed produced clear changes in all metrics examined. Visual discomfort first increased, on average, after 6 minutes; VA declined on average by 0.02 logarithm of the minimum angle of resolution and NPC and NPA both receded by just over 1 cm. However, none of these changes differed significantly at any stage of the menstrual cycle. CONCLUSIONS: We conclude that visual discomfort, generated by providing increased accommodative demand while viewing a visual display unit, does not vary significantly during the menstrual cycle.

Accommodation, Ocular↗
PubMed2006

Short-term adaptation to vertical yoked prisms.

PURPOSE: The purpose of this study was to investigate short-term adaptation to vertical yoked prisms in visually normal subjects as well as to develop normative data for future comparative purposes in patients with acquired brain injury. METHODS: A full-body enclosure containing a calibrated laser pointer was used to assess egocentric localization (i.e., one's perceived sense of "straight ahead") in total darkness. Fourteen visually normal subjects were tested in a counterbalanced manner under both experimental (20 pd base-down) and control (plano or zero power) test conditions with each test condition lasting 1 hour. A rating scale questionnaire was also administered to assess quantitatively subjective adaptation to the yoked prisms. RESULTS: Group mean egocentric localization showed approximately 50% adaptation during the 1-hour test period. Subjective adaptation results were similar. CONCLUSION: The findings suggest that rapid perceptually driven, sensorimotor adaptation occurred as assessed both objectively and subjectively in response to vertical yoked prisms. These results are similar to those found in other experiments involving short-term adaptation to optical rearrangements.

Adaptation, Ocular↗
PubMed2006

The effect of colored lenses on the visual evoked response in children with visual stress.

PURPOSE: Some children with visual stress and/or headaches have fewer symptoms when wearing colored lenses. Although subjective reports of improved perception exist, few objective correlates of these effects have been established. METHODS: In a pilot study, 10 children who wore Intuitive Colorimeter lenses, and claimed benefit, and two asymptomatic children were tested. Steady-state potentials were measured in response to low contrast patterns modulating at a frequency of 12 Hz. Four viewing conditions were compared: 1) no lens; 2) Colorimeter lens; 3) lens of complementary color; and 4) spectrally neutral lens with similar photopic transmission. RESULTS: The asymptomatic children showed little or no difference between the lens and no lens conditions. When all the symptomatic children were tested together, a similar result was found. However, when the symptomatic children were divided into two groups depending on their symptoms, an interaction emerged. Children with visual stress but no headaches showed the largest amplitude visual evoked potential response in the no lens condition, whereas those children whose symptoms included severe headaches or migraine showed the largest amplitude visual evoked potential response when wearing their prescribed lens. CONCLUSIONS: The results suggest that it is possible to measure objective correlates of the beneficial subjective perceptual effects of colored lenses, at least in some children who have a history of migraine or severe headaches.

Adolescent↗
PubMed1991

A tint to reduce eye-strain from fluorescent lighting? Preliminary observations.

The rapid modulation of light from fluorescent lamps is responsible for eye-strain and headaches. The modulation is greater at certain wavelengths than at others, and it can therefore be reduced by wearing tinted spectacles. A tint was designed: (1) to minimize the luminous pulsation of light from conventional halophosphate fluorescent lamps; (2) to avoid as much as possible any concomitant increase in the pulsation from triphosphor lamps; (3) to interfere with colour perception as little as possible; and (4) to have a cosmetically acceptable colour appearance. The four design criteria conflict. A compromise design is described, together with case histories of patients who appear to have benefited from the use of the tint.

Adult↗
PubMed2004

The optometric correlates of migraine.

Migraine is a common, chronic, multi-factorial, neuro-vascular disorder typically characterised by recurrent attacks of unilateral, pulsating headache and autonomic nervous system dysfunction. Migraine may additionally be associated with aura; those focal neurological symptoms that may precede or sometimes accompany the headache. This review describes the optometric aspects of migraine headache. There have been claims of a relationship between migraine headaches and errors of refraction, binocular vision anomalies, pupil anomalies, visual field changes and pattern glare. The quality of the evidence for a relationship between errors of refraction and binocular vision and migraine is poor. The quality of the evidence to suggest a relationship between migraine headache and pupil anomalies, visual field defects and pattern glare is stronger. In particular the link between migraine headache and pattern glare is striking. The therapeutic use of precision-tinted spectacles to reduce pattern glare (visual stress) and to help some migraine sufferers is described.

Asthenopia↗
PubMed2004

Clinical characteristics of unilateral myopic anisometropia in a juvenile optometric practice population.

PURPOSE: A retrospective study of longitudinal case histories, undertaken to establish the clinical and statistical characteristics of unilateral myopic anisometropia (UMA) amongst the juvenile and adolescent population at an optometric practice, is reported. UMA was defined as that specific refractive state where an unequivocally myopic eye is paired with a 'plano' [spherical equivalent refraction, (SER) = +/-0.25 Dioptres (D)] companion eye. METHODS: The clinical records of all patients aged <19 years on file at an established independent optometric practice were categorised as 'myopic' (SER < or =-0.50 D), 'hypermetropic' (> or =+0.75 D) or 'emmetropic' (> or =-0.37< or =+0.62 D). Subsequently all juvenile patients matching the UMA criterion, together with a case-matched group of bilaterally myopic individuals, were selected as the comparative study populations. RESULTS: A total of 14.4% (n = 21 of 146) of the juvenile myopic case histories were identified as cases of UMA. More than half of these UMA cases emerged between the ages of 11.5 and 13.5 years. There was a marked female gender bias. The linear gradient of the age-related mean refractive trend in the myopic eye of the UMA population was not statistically significantly different (p > 0.1) to that fitted to the ametropic progression recorded in either eye of the case-matched population of young bilateral myopes; uniquely the slope associated with the companion eye of UMA cases was statistically significantly (p < 0.025) less steep. Compared with bilateral myopes fewer cases of UMA required a refractive correction to relieve visual or asthenopic symptoms, and this initial correction was dispensed on average 1 year later (at age 12.7 years) in UMA patients. CONCLUSIONS: Individuals identified as demonstrating clinically-defined UMA can be considered as distinct but functionally normal cases on the continuum of human refractive error. However, any unilaterally-acting determining factor(s) underlying the genesis of the condition remain obscure.

Adolescent↗