Blink patterns: reading from a computer screen versus hard copy.

PURPOSE: Many subjects experience ocular and visual symptoms during computer use. Previous studies have reported a reduced blink rate during computer operation and suggested that this may account for some of the symptoms, particularly dry eye. However, these earlier investigations failed to include an appropriate control condition. To determine whether it is computer screen viewing that produces the change in blink rate, the present study compared blink patterns when reading from either a desktop computer monitor or a hard copy printed text under equivalent viewing conditions. METHODS: Subjects (N = 25) were required to perform a continuous 20-minute reading task from either a desktop computer screen or a printed hard copy page at a viewing distance of 50 cm. Identical text was used in the two sessions, which was matched for size and contrast. Target viewing angle and luminance were similar for the two conditions. Subjects were videotaped during the task to determine their blink rate and amplitude. Immediately after the task, subjects completed a questionnaire regarding ocular symptoms experienced during the trial. RESULTS: Mean blink rates for the computer and hard copy conditions were 14.9 and 13.6 blinks per minute, respectively (p = 0.58). However, a significantly higher percentage of incomplete blinks was observed for the computer condition (7.02 vs. 4.33%; p = 0.02). No significant correlation was found between the symptom score and the percentage of incomplete blinks. CONCLUSIONS: When compared with an equivalent hard copy control condition, blink rates were not reduced during computer operation. It is proposed that the previously observed differences in blink rate are more likely to be produced by changes in cognitive demand rather than the method of presentation. However, a higher percentage of incomplete blinks was noted during computer operation, which may have been associated with visual fatigue.

Blink rate, incomplete blinks and computer vision syndrome.

PURPOSE: Computer vision syndrome (CVS), a highly prevalent condition, is frequently associated with dry eye disorders. Furthermore, a reduced blink rate has been observed during computer use. The present study examined whether post task ocular and visual symptoms are associated with either a decreased blink rate or a higher prevalence of incomplete blinks. An additional trial tested whether increasing the blink rate would reduce CVS symptoms. METHODS: Subjects (N = 21) were required to perform a continuous 15-minute reading task on a desktop computer at a viewing distance of 50 cm. Subjects were videotaped during the task to determine their blink rate and amplitude. Immediately after the task, subjects completed a questionnaire regarding ocular symptoms experienced during the trial. In a second session, the blink rate was increased by means of an audible tone that sounded every 4 seconds, with subjects being instructed to blink on hearing the tone. RESULTS: The mean blink rate during the task without the audible tone was 11.6 blinks per minute (SD, 7.84). The percentage of blinks deemed incomplete for each subject ranged from 0.9 to 56.5%, with a mean of 16.1% (SD, 15.7). A significant positive correlation was observed between the total symptom score and the percentage of incomplete blinks during the task (p = 0.002). Furthermore, a significant negative correlation was noted between the blink score and symptoms (p = 0.035). Increasing the mean blink rate to 23.5 blinks per minute by means of the audible tone did not produce a significant change in the symptom score. CONCLUSIONS: Whereas CVS symptoms are associated with a reduced blink rate, the completeness of the blink may be equally significant. Because instructing a patient to increase his or her blink rate may be ineffective or impractical, actions to achieve complete corneal coverage during blinking may be more helpful in alleviating symptoms during computer operation.

Computer-related visual symptoms in office workers.

PURPOSE: Many individuals report visual symptoms during office work and specifically computer use. This study determined the prevalence of symptoms in a population of office workers, and examined the association between these symptoms and both dry eye disease and other demographic factors. METHOD: A written questionnaire was used to quantify the prevalence of symptoms in 520 New York City office workers, and to determine the effect of risk factors including gender, ethnicity, age, smoking, type of refractive correction and hours spent doing computer work. The questionnaire also examined the prevalence of ocular surface disease. RESULTS: A significant positive correlation was observed between the symptom score and the number of hours spent working on a computer in a typical day. The most prevalent symptom was tired eyes, which was reported by approximately 40% of subjects as occurring 'at least half the time'. 32% and 31% of subjects reported symptoms of dry eye and eye discomfort, respectively. Symptoms varied significantly with gender (being greater in females), ethnicity (being greater in Hispanics) and the use of rewetting drops. A significant positive correlation was observed between computer-related visual symptoms and the Ocular Surface Disease Index (OSDI), a measure of dry eye. CONCLUSIONS: Visual symptoms associated with computer use occur frequently in the general population producing discomfort for extended periods of time. They are strongly associated with ocular surface disease. Therapeutic regimens need to be developed for this widespread condition.

A comparison of symptoms after viewing text on a computer screen and hardcopy.

PURPOSE: Computer vision syndrome (CVS) is a complex of eye and vision problems experienced during or related to computer use. Ocular symptoms may include asthenopia, accommodative and vergence difficulties and dry eye. CVS occurs in up to 90% of computer workers, and given the almost universal use of these devices, it is important to identify whether these symptoms are specific to computer operation, or are simply a manifestation of performing a sustained near-vision task. METHOD: This study compared ocular symptoms immediately following a sustained near task. 30 young, visually-normal subjects read text aloud either from a desktop computer screen or a printed hardcopy page at a viewing distance of 50 cm for a continuous 20 min period. Identical text was used in the two sessions, which was matched for size and contrast. Target viewing angle and luminance were similar for the two conditions. Immediately following completion of the reading task, subjects completed a written questionnaire asking about their level of ocular discomfort during the task. RESULTS: When comparing the computer and hardcopy conditions, significant differences in median symptom scores were reported with regard to blurred vision during the task (t = 147.0; p = 0.03) and the mean symptom score (t = 102.5; p = 0.04). In both cases, symptoms were higher during computer use. CONCLUSIONS: Symptoms following sustained computer use were significantly worse than those reported after hard copy fixation under similar viewing conditions. A better understanding of the physiology underlying CVS is critical to allow more accurate diagnosis and treatment. This will allow practitioners to optimize visual comfort and efficiency during computer operation.

A combination solution for routine pupillary dilation.

BACKGROUND: This study investigated the ability of a combination drop containing reduced concentrations of tropicamide and phenylephrine to produce pupillary dilation adequate for routine fundoscopy. METHODS: One eye of each subject (N = 28; age range, 21 to 40 years; median, 23 years) was dilated with 1 drop of a solution containing 0.5% tropicamide and 2.5% phenylephrine (0.5T/2.5P). The other eye was dilated with 1 drop of either of 2 mixtures: 0.5% tropicamide and 1.25% phenylephrine (0.5T/1.25P, N = 15; median age, 23 years), or 0.25% tropicamide and 1.25% phenylephrine (0.25T/1.25P, N = 13; median age, 23 years). A topical anesthetic was administered before instilling the mydriatic agents. Pupil diameter was measured from a flash photograph taken every 15 minutes for 3 hours. There was no significant difference in pupil diameter between eyes dilated with the 0.5T/1.25P test solution and the 0.5T/2.5P control solution for the first 75 minutes after instillation (P = 0.41). All pupils reached their maximum diameter 60 minutes after drop instillation; where no significant difference was observed between the 3 mydriatic solutions (P = 0.81). All pupils were at least 7 mm in diameter 30 minutes after drop instillation, and this size was maintained for at least another 75 minutes for all solutions. CONCLUSIONS: Combination preparations of reduced concentrations of tropicamide and phenylephrine can produce clinically adequate mydriasis.

Does the dynamic cross cylinder test measure the accommodative response accurately?

BACKGROUND: The dynamic cross cylinder (DCC) test is a standard clinical procedure used to assess the accommodative response (AR) subjectively. However, because of potential problems arising from the ambiguous stimulus conditions, it is unclear whether this test provides an accurate measure of the AR. The aim of this study was to compare clinical subjective findings with objective measurements of the AR. METHODS: Subjective findings to a 2.50-diopter (D) accommodative stimulus obtained with the DCC test (without fogging lenses) were compared with objective measurements of the AR obtained with a Grand Seiko WAM 5500 optometer (RyuSyo Industrial Co. Ltd., Kagawa, Japan) in 25 young subjects. As spherical lenses were introduced to quantify the subjective finding, objective measures of the AR were also recorded through these lenses. RESULTS: The mean AR recorded subjectively and objectively was 2.35 and 1.68 D, respectively (P < 0.0001). Of the 10 subjects who demonstrated a lead of accommodation subjectively, only 1 had a lead objectively. For the 8 subjects who showed a lag of accommodation subjectively, all had a lag objectively. Introducing lenses produced a significant change in the mean AR. CONCLUSION: The subjective DCC test as performed here does not provide an accurate measurement of the AR to a near target in a young population. We recommend that alternative techniques such as using an objective, open-field optometer or Cross-Nott retinoscopy be adopted for determining the within-task AR.

Does prior instillation of a topical anaesthetic alter the pupillary mydriasis produced by tropicamide (0.5%)?

PURPOSE: It is common clinical practice to instill a topical anaesthetic prior to the instillation of a mydriatic agent into the eye. The main rationale for using the anaesthetic is to increase corneal permeability, so that more of the mydriatic agent reaches the receptor sites within the anterior chamber. It addition, as mydriatics generally cause stinging, prior use of an anaesthetic should reduce the degree of discomfort. The aim of the present study was to determine whether the efficacy of mydriasis produced by an antimuscarinic agent is enhanced by prior instillation of a topical anaesthetic. METHOD: The study was performed using a double-masked protocol on 20 healthy young subjects. One drop of either proparacaine (proxymetacaine) (0.5%) or isotonic saline was instilled into the eye, followed by one drop of tropicamide (0.5%). Pupil diameter was measured using a customized photographic device at 0, 10, 20, 30 and 60 min following drug instillation. Additionally, subjects were asked to rate the degree of discomfort following the instillation of each drop on a scale from 0 (no discomfort) to 10 (agony). RESULTS: There was no significant difference in either the rate of onset of mydriasis, or the maximum pupil diameter achieved between the two conditions. The mean change in pupil diameter produced by tropicamide after the instillation of saline or proparacaine was 2.31 and 2.28 mm, respectively. The mean discomfort scores following instillation of saline and proparacaine were 1.15 and 1.65, respectively, while mean discomfort scores following the instillation of tropicamide after saline or proparacaine were 4.00 and 0.85, respectively. CONCLUSIONS: Instillation of a topical anaesthetic does significantly reduce the degree of discomfort produced by the instillation of tropicamide. However, it does not produce any significant increase in either the magnitude or rate of onset of mydriasis.

Do progressing myopes show reduced accommodative responses?

Refractive error and accommodative responsivity were monitored at 4-month intervals over a 1-year period to determine whether an increased lag of accommodation either precedes or accompanies the development of myopia. Accommodation was measured for stimulus levels of 2.5, 3, 4, and 5 D, and both the slope of the stimulus-response function and accommodative error were computed. Almost all subjects exhibited accommodative stimulus-response gradients close to unity, although a lower gradient was observed in subjects who were myopic upon entry into the study and whose ametropia remained stable. These stable myopes also exhibited the largest lag of accommodation. These findings do not support the proposal that the development of myopia in young adults is accompanied by a reduced accommodative response during nearwork.