GB/T 40230.1-2021Methods of visual fatigue test and evaluation—Part 1: Ophthalmology and optometry (English PDF)

3.1 Visual Fatigue

Visual fatigue refers to symptoms of discomfort when working with eyes for a long time.

NOTE: the symptoms of visual fatigue include blurred vision, headache, dry eyes and diplopia, etc.

3.2 Refraction

In optometry, when light passes from one medium to another medium with a different refractive index, a change of direction will occur.

NOTE: the unit for measuring the size of refraction is diopter (represented by the symbol D and expressed in m-1).

3.3 Accommodation

Accommodation refers to the ability of the human eye to change the ocular refraction in order to clearly see close objects.

3.4 Experimenter; Observer

Experimenter / observer refers to the personnel in charge of the progress of the experiment during the experiment.

NOTE: the task of the experimenter / observer is to give instructions to the test subjects in accordance with the experimental design and guide them to perform experimental procedures in the experiment.

3.5 Subject; Participant

Subject / participant refers to the personnel participating in the experimental process or receiving the experiment during the experiment.

NOTE: subject / participant is also known as receiver or tester.

3.6 Accommodative Response

Accommodative response refers to the actual amount of accommodation generated by the stimulation of the fixating eye to the near-fixed optotype.

3.7 Rapid Serial Visual Presentation; RSVP

Rapid serial visual presentation refers to a visual graphic presentation method that rapidly displays a string of character streams, a string of word (sentence) streams or a picture stream at the same position on the screen in chronological order.

3.8 Accommodative Stimulus

Accommodative stimulus refers to the amount of accommodation required by the eye to see objects at a specific distance.

NOTE: the unit is diopter.

3.9 Lag of Accommodation

Lag of accommodation refers to the situation that the amount of accommodative response is less than the amount of accommodative stimulus.

3.10 Accommodative Microfluctuations

When the eye is fixed on a stationary object, its accommodation is not fixed, and there are constant micro changes around the average accommodative response.

3.17 Tear Film

Tear film refers to a layer of tear fluid that covers the surface of the cornea and conjunctiva between the upper and lower eyelids.

3.18 Tear Film Break-up Time

Tear film break-up time refers to the time when the tear film firstly breaks up without blinking.

4.1 Principles

Considering the constraints in the actual measurement, the principles of the measurement methods involved in this document are mainly direct observation method, minimum change method and adaptive method of psychophysics.

4.2 Test Environment

Temperature: 15 °C ~ 30 °C, preferably 23 °C ~ 28 °C. Humidity: 25% ~ 75%.

Noise: the background noise should be within 25 dB ~ 45 dB.

Illumination: the initial ambient illumination shall be 0 lx; the ambient illumination conditions should be set to be adjustable, and satisfy the environmental conditions required for most equipment test. The specific illumination setting shall be set in accordance with the test equipment and the purpose and task of the experiment.

4.3 Requirements for Subject Selection

Basic requirements: people with normal or corrected-to-normal vision, and without eye diseases shall be recruited as the subjects.

The subjects shall have a clear and unmistakable understanding of the task to be completed during the test.

Different test equipment and test contents may have different requirements for the subjects. For the requirements related to test methods and equipment, see the section of each test method.

The selection basis, sample size, sample selection method, history of eye disease and history of brain disease of the subjects shall be recorded and archived. The archival date shall be based on the retention time of the original data by the laboratory.

4.4 Requirements for Experimenter Qualification

Persons with a background in ophthalmology or optometry, or those engaged in optics, visual sciences, psychology, sociology and biology and other related fields, and have been trained shall be selected as the experimenters.

4.5 Requirements for Instruments and Equipment

The instruments and equipment shall comply with the precision requirements.

4.6 Requirements for Experimental Data Record

The experimental data records shall be complete and clear, and shall include the necessary basic information of the subjects, such as: age, gender, history of eye disease, and whether they have mental or brain diseases, etc.

The retention and destruction of test data shall be carried out in accordance with relevant rules and regulations.

4.7 Requirements for Experimental Data Report

Data in the result presentation shall be rounded to two decimal places.

The data result report shall describe in detail the test subjects, test tools and test procedures, etc., and shall comply with the requirements of Appendix A.

5.1 Accommodative Response

5.1.1 Test equipment

An open infrared automatic refractometer should be adopted. The sampling rate shall be not less than 5 Hz (5 measurements within 1 s, the higher the sampling rate, the shorter the test time); the equipment resolution shall be not greater than 0.01 Hz.

5.1.2 Test environment

When adopting the open infrared automatic refractometer, the test shall be performed in a normal lighting environment; it shall be ensured that the pupil diameter is greater than or equal to 2.3 mm.

Test method: the optotype is a single black Chinese character continuously displayed by the RSVP software in the center of the LCD screen in front of the eye; in accordance with different test subjects (for example, age), choose text content (story, novel or book) with different levels of difficulty. The size of the test window should be 142.24 mm (5.6 inches); the brightness of the display screen should be 40 cd/m2 ~ 170 cd/m2; the resolution should be 1,280 pixel x 800

5.1.6 Result presentation

Mark the accommodative response at different distances:

---right-eye accommodative response: X1 (D);

---left-eye accommodative response: X2 (D).

NOTE: X1 represents the specific value of the accommodative response of the right eye; X2 represents the specific value of the accommodative response of the left eye.

5.2 Accommodative Microfluctuations

5.2.1 Test equipment

The requirements for the equipment are the same as 5.1.1.

5.2.2 Test environment

The requirements for the environment are the same as 5.1.2.

5.2.3 Test procedures

Taking the infrared automatic refractometer as an example, the test procedures are as follows:

a) After wearing the equivalent spherical lenses in accordance with the binocular diopter of the subjects, ensure that the corrected visual acuity of one eye is greater than or equal to 1.0. Before measurement, let the eyes relax for at least 5 min.

b) Instruction setting: inform the subjects of a short text that will be presented in the form of RSVP in front of them, and ask them to silently read the Chinese characters presented in front of them and understand the short text. After the experiment is over, instruct them to repeat the summary of the short text.

c) Measurement of accommodative response: accommodate the subjects' line of sight and the position of the optotype on the screen, so that the subjects' visual axis, the measurement optical axis of the automatic refractometer and the accommodated optotype are at the same level. Continuously measure the accommodative response of one eye of the subjects, which should be greater than or equal to 1 min. When calculating the accommodative response, relatively stable values in the middle of the whole measurement process should be taken.

d) Adopt the same method to continuously measure the accommodative response of one eye of the subjects.

5.2.4 Result calculation

Data screening and conversion: select the relatively stable accommodative response values in the middle of the measurement; after eliminating the obvious abnormal values caused by factors like blinking or tear film break-up, select the data within the range of twice the standard deviation of all the measured accommodative response values as the experimental data (more than 100 values); calculate the standard deviation of the experimental data, which is the accommodative microfluctuations.

5.2.5 Result presentation

Mark the accommodative microfluctuations at different distances:

---right-eye accommodative microfluctuations: X1 (D);

---left-eye accommodative microfluctuations: X2 (D).

NOTE: X1 represents the specific value of the accommodative microfluctuations of the right eye; X2 represents the specific value of the accommodative microfluctuations of the left eye.

5.3 Near Point of Accommodation

5.3.1 Test equipment

For the accommodation of the optotypes (letter optotypes or other small optotypes), the smallest single optotype that can always be clearly seen in the eye chart should be used.

5.3.2 Test environment

The test shall be carried out in a close-range reading lighting environment, and the illuminance should be set to 500 lx ~ 700 lx.

5.3.3 Test procedures

The test procedures are as follows:

a) The subjects are completely corrected for refractive errors; under normal lighting, cover the non-detected eye. Place the near optotype 40 cm in front of the subjects' eyes;

b) Instruct the subjects to look at the optotype on the upper line of the best vision. At a speed of about 2 cm/s, the near optotype should be moved closer to the subjects, until it is reported by the subjects that the optotype is persistently blurred, then, return to the final position, where the optotype remains clear; measure the distance between the optotype and the plane of the subjects' glasses at this moment, which is the near point of accommodation.

5.3.4 Result calculation

Measure the distance between the optotype and the plane of the subjects' glasses at the end

5.4 CA / C Ratio

5.4.5 Result presentation

CA / C ratio: X (D/6Delta).

NOTE: X represents the specific value of CA / C ratio; D/6Delta represents the change in convergence accommodation caused by the convergence change of 6Delta.

5.5 AC /A Ratio

5.5.1 Test equipment

Comprehensive refractometer, near vision card.

5.5.2 Test procedures

The test procedures are as follows:

a) The subjects are completely corrected for refractive errors. Place the near optotype 40 cm in front of the subjects' eyes.

b) Place Risley prism in front of the subjects' eyes; place a 12Delta with the bottom facing inward in front of the right eye; place a 6Delta with the bottom facing upward in front of the left eye. Instruct the subjects to look at the smallest single optotype that has been clearly seen in the near vision chart. At this moment, the subjects will see two optotypes: one at the lower left and the other at the upper right. Instruct the subjects to look at the optotype at the lower left, while looking at the optotype at the upper right with the peripheral vision. Then, at a speed of 2Delta/s, move the right optotype, until the upper and lower optotypes are aligned in the vertical direction; record the direction and power of the prism base at this time.

c) Meanwhile, do not pause, continue to turn the prism in the same direction, until the subjects see two more optotypes: one at the lower right and the other at the upper left. Then, turn the prism in the opposite direction, until it is reported by the subjects that the two optotypes are aligned in the vertical direction again; record the direction and power of the prism base at this time. The data difference between the two vertical alignments needs to be less than 3Delta. The result shall take the average value of the prismatic power of the two alignments.

d) On the basis of distance refractive correction, simultaneously add +1.00 D in front of both eyes. Then, repeat Step 2 and Step 3 to obtain the measured values of two phoria.

5.5.3 Result calculation

The absolute value of the difference between the measured values of two phoria is the AC / A ratio, which shall be calculated in accordance with Formula (3). Where, P---AC / C ratio;

P1---the average value of the prismatic power measured through Step c) in 5.5.2;

P2---the average value of the prismatic power measured through Step d) in 5.5.2.

5.5.4 Result presentation

AC / A ratio: X (Delta/D).

NOTE: X represents the specific value of AC / A ratio.

5.6 Tear Film Break-up Time

5.6.1 Test equipment

Fluorescein test strips.

5.6.2 Test environment

The test should be performed indoor. There are no special requirements.

5.6.3 Requirements for subject selection

Except for patients with corneal diseases, for example, corneal ulcers, it is advisable to select all groups of people who can cooperate with the examination.

5.6.4 Test method

Gently place the moistened fluorescein test strip on the subjects' lower fornix, then, take it out.

Instruct the subjects to blink several times, then, open their eyes and look ahead. The examiner adopts cobalt blue light examination to measure the time from the beginning of eye opening to the occurrence of the first dark spot on the cornea, which is the tear film break-up time. Conduct the measurement for 3 times and take the average value. A tear film break-up time of less than 10 s is deemed as unstable tear film.

5.6.5 Result calculation

Conduct the measurement for 3 times and take the average value.

5.6.6 Result presentation

Tear film break-up time: X (s).

NOTE: X represents the specific time value of tear film break-up. […]