Investigative Ophthalmology and Visual Science (supp), vol 38, No. 4, p. 326

Bước tới: chuyển hướng, tìm kiếm
 Tạp chí Investigative Ophthalmology and Visual Science 1997 ; 4 (38):326
 Tác giả   B. Dumery, Vo Van Toi
 Nơi thực hiện   Department of Biomedical Engineering, Bioengineering Center,Tufts University, 4 Colby Street, Medford, MA 02155
  DOI   URL  [ PDF]


Purpose. To determine how VDT use and the degree of concentration of visual tasks influence blinking rate and ocular discomfort.

Method. Six healthy subjects (4 males and 2 females, age: 26 ± 10 years old) with no eye problems participated in the study. The subjects performed different tasks for a maximum of two hours: (1) relaxing and/or performing work which did not require visual concentration, (2) reading text in print, (3) reading text o n a video display terminal (VDT), (4) editing text on paper, (5) editing text on a computer and (6) playing a computer game. These tasks allowed us to determine the difference between the influence of non-VDT/ VDT use and low/high degrees of visual conce ntration. During the experiments, the subject’s blink rate was monitored using our portable blink rate recorder which provided the number of blinks per minute. Before and after each experiment the subject’s ocular discomfort was evaluated by: (1) determi ning the flicker/fusion sensitivities through establishing the temporal modulation transfer function1 (TMTF) using a visual stimulator2, (2) completing a questionnaire depicting different ocular discomfort symptoms such as soreness, tiredness, itching, and heavy sensations in the eyes, and (3) measuring the visual acuity using a standard visual acuity chart. The results were analyzed statistically.

Results. (1) Tasks requiring a high degree of concentration caused lowe r blink rates than tasks requiring a low degree of concentration (4 vs. 16 bpm). (2) The difference in average blink rates while performing tasks with and without a VDT was not statistically significant. (3) Tasks requiring a high degree of concentratio n caused less fluctuation in blink rates than tasks requiring a low degree of concentration (± 2.5 vs. ± 7.4 bpm). (4) Ocular discomfort was more severe when using a VDT. (5) Ocular discomfort symptoms increased while visual acuity decreased (correlation coefficient: -0.97). (6) The difference between the flicker sensitivity before and after each experime nt was not statistically significant at all flicker frequencies, including the critical flicker frequency (CFF).

Conclusions. (1) Ocular discomfort can be qualified with the following equation: ocular discomfort = (visual concentration + VDT ) / (blink rate). (2) The questionnaire and the visual acuity chart were appropriate in assessing ocular discomfort, by contrast, the TMTF was not. Our investigation contributes to studies concerning whether blink rate is a cause or a consequence of ocul ar discomfort.

Tiếng Việt