**4.1 Analysis of the colour types for the virtual background design**

Statistical binomial test on five types of colour of virtual background (Table 1) shows that the colour type inflicts the users with eyestrain and blurred vision symptoms. Fig. 2 (a) and

Table 6 shows the result of experiment on the effect of display resolution on the subjects. Three level of resolution were investigated for both the liquid crystal display (LCD) and cathode ray tube (CRT) displays, which are high resolution, medium resolution and low resolution. The result of statistical binomial test at 5% significant level found that the overall level of resolution using either the LCD or CRT displays causes eyestrain symptoms to the users with more than 56% experiencing eyestrain. Others effect such as dry and irritated eyes symptoms were experienced by 56% of users when interacting with medium and low

The result on the effect of contrast ratio to visual symptoms is described in Table 7. There are three kind of contrast ratio investigated. They are -50.83%, +24.58% and 0%. The ratio can vary from 100% (positive) to zero for targets darker than the background, and from zero to minus infinity (-∞) for targets brighter than the background (Grether and Baker, 1972). Statistical binomial test at 5% significant level shows that all contrast ratios causes eyestrain symptoms (75% of users). Blurred vision and dry and irritated eyes symptoms were experienced by 63% and 50% of users at contrast ratios of --50.83% and 0% (or -0.56%)

**Exact Sig.** 

0.633 0.321

0.633 0.114

**(1-tailed) Decision** 

Effect Effect

Effect Effect

**3.6 Effect of resolution of display type to visual symptoms** 

**Observation** 

63

50

variables of the VE that may cause the occurrence of visual symptoms.

**4.1 Analysis of the colour types for the virtual background design** 

**Proportion (%) Symptoms** 

**2.** +24.58% 75 Eyestrain 0.633 Effect

Table 7. Result of Experiment and Binomial Test of Visual Symptoms of Contrast Ratio

One of the parameters of cyber sickness is visual symptoms (Barret, 2004). In his handbook, Anshel, J. (2005) mentioned that visual symptoms can vary but these mostly include eyestrain, headache, blurred vision, dry and irritated eyes, double vision, colour distortion and light sensitivity. The symptom most often occurs when the viewing demand of the task exceeds the visual abilities of the user. The viewing task is influenced by the design of the virtual environment viewed or interacted. This research has identified some attributes or

Statistical binomial test on five types of colour of virtual background (Table 1) shows that the colour type inflicts the users with eyestrain and blurred vision symptoms. Fig. 2 (a) and

Eyestrain Blurred Vision

Eyestrain Dry and Irritated Eyes

resolution CRT display.

respectively.

*p*> 0.05 ; N = 8

**4. Discussion** 

**No. Ratio of** 

**Contrast** 

**1.** -50.83% <sup>75</sup>

**3.** 0% (-0.56%) <sup>75</sup>

**3.7 Effect of contrast ratio** 

(b) exhibit the levels of eyestrain and blurred vision symptoms experienced by users when interacting with the VE. Only the red colour significantly resulted in blurred vision. This might be caused by the red colour causing discomfort to the eyes when a virtual object is in motion. The colour is also quite glaring in such a way that it would be difficult for the eyes

(a)

Fig. 2. (a) Level of eyestrain symptoms (b) Level of blurred vision symptoms

Ergonomics Design Criteria of a Virtual Environment 181

(b)

(c) Fig. 3. (a) Level of eyestrain symptoms (b) Level of Light Sensitivity symptoms (c) Level of

dry and irritated eyes symptoms

to focus on a virtual object. Others types of colours also generally causes eyestrain symptoms. Ergonomics recommendation on background colours stipulates the use of a design that is able to reduce or minimize the incidence of visual symptoms. No strain and no blur level is the target in the design of the background colour. Thus Red, Fuchsia, Dark Sky Blue, Medium Slate Blue and White colours must be changed to a smoother and softer colour type that can alleviate visual symptoms incidence.

#### **4.2 Analysis of the virtual lighting level**

Results of statistical binomial test in Table 2 demonstrated the effect of brightness level of the virtual light on the occurrence of visual symptoms incidence. The level of brightness affects the eyes when tracking virtual objects in the VE. A darker light level (10%) or higher bright level (100%) can induce eyestrain and dry and irritated eyes symptoms as well as light sensitivity symptom. This is because the eyes are forced to focus causing strain to the eyes as well as dryness and irritation and decrease the sensitivity to light. Fig.3 (a), (b) and (c) describes the level of symptoms occurring in the human visual system. No effect (no strained, no dry, no glare) is the best condition of virtual lighting to be considered as one of the attributes in designing a VE.

#### **4.3 Analysis of the effect Field of View (FOV)**

Table 3 is the result of statistical binomial test of the effect of field of view (FOV) on users. It shows that the degree of visual field can develop incidence of visual disorder especially eyestrain, blurred vision and dry and irritated eyes. Therefore the degree of FOV has to be taken into account when designing a VE. It can be seen that 1200 of FOV causes 50% of the users to suffer eyestrain symptoms as compared to the 850 of FOV. On the other hand, dry

to focus on a virtual object. Others types of colours also generally causes eyestrain symptoms. Ergonomics recommendation on background colours stipulates the use of a design that is able to reduce or minimize the incidence of visual symptoms. No strain and no blur level is the target in the design of the background colour. Thus Red, Fuchsia, Dark Sky Blue, Medium Slate Blue and White colours must be changed to a smoother and softer

Results of statistical binomial test in Table 2 demonstrated the effect of brightness level of the virtual light on the occurrence of visual symptoms incidence. The level of brightness affects the eyes when tracking virtual objects in the VE. A darker light level (10%) or higher bright level (100%) can induce eyestrain and dry and irritated eyes symptoms as well as light sensitivity symptom. This is because the eyes are forced to focus causing strain to the eyes as well as dryness and irritation and decrease the sensitivity to light. Fig.3 (a), (b) and (c) describes the level of symptoms occurring in the human visual system. No effect (no strained, no dry, no glare) is the best condition of virtual lighting to be considered as one of

Table 3 is the result of statistical binomial test of the effect of field of view (FOV) on users. It shows that the degree of visual field can develop incidence of visual disorder especially eyestrain, blurred vision and dry and irritated eyes. Therefore the degree of FOV has to be taken into account when designing a VE. It can be seen that 1200 of FOV causes 50% of the users to suffer eyestrain symptoms as compared to the 850 of FOV. On the other hand, dry

(a)

colour type that can alleviate visual symptoms incidence.

**4.2 Analysis of the virtual lighting level** 

the attributes in designing a VE.

**4.3 Analysis of the effect Field of View (FOV)** 

Fig. 3. (a) Level of eyestrain symptoms (b) Level of Light Sensitivity symptoms (c) Level of dry and irritated eyes symptoms

Ergonomics Design Criteria of a Virtual Environment 183

(b)

(c) Fig. 4. (a) Level of eyestrain symptoms (b) Level of blurred vision symptoms (c) Level of dry

and irritated eyes symptoms

and irritated eyes symptoms were experienced by 63% of the users when using 1200 of FOV higher than they were using 850 of FOV. Thus a wider of FOV or narrower of FOV will cause users to suffer one of the visual symptoms. It is because of both conditions require the eyes to focus. Thus it is essential to determine what FOV is required to reduce these symptoms. Fig.4 (a), (b) and (c) describes the levels of symptoms occurring for eyestrain, blurred vision and dry and irritated eyes symptoms respectively. For the eyestrain symptoms, 120o of FOV is better than 85o because about 50 % users did experience any incidence. On the contrary, 120o of FOV is not acceptable compared to 85o for dry and irritated eyes symptoms. This is because 50% of users did not experience any eye symptoms when using 85o of FOV.

#### **4.4 Analysis of the Flow Rate (FR) of the virtual objects**

Flow rate (FR) is the rate at which subsequent flow of the virtual object can be generated per unit time. Result of statistical binomial test in Table 4 have found that the flow rate of virtual object have the effect on the incidence of eyestrain, blurred vision and dry and irritated eyes symptoms. This is because it affects the ability of the eyes to see the virtual objects as it is being generated so that the eyes experienced strain, blur and also dryness or irritation during that period. Fig. 5 (a), (b), and (c) depict the level of the symptoms experienced by users. The effect can be minimized by designing the appropriate flow rate of the virtual object generated. A flow rate at 5 seconds per piece is better than a flow rate of 10 seconds per piece to avoid blurred vision symptoms. This is because more than 69% of users do not suffer this condition at this flow rate.

and irritated eyes symptoms were experienced by 63% of the users when using 1200 of FOV higher than they were using 850 of FOV. Thus a wider of FOV or narrower of FOV will cause users to suffer one of the visual symptoms. It is because of both conditions require the eyes to focus. Thus it is essential to determine what FOV is required to reduce these symptoms. Fig.4 (a), (b) and (c) describes the levels of symptoms occurring for eyestrain, blurred vision and dry and irritated eyes symptoms respectively. For the eyestrain symptoms, 120o of FOV is better than 85o because about 50 % users did experience any incidence. On the contrary, 120o of FOV is not acceptable compared to 85o for dry and irritated eyes symptoms. This is

because 50% of users did not experience any eye symptoms when using 85o of FOV.

Flow rate (FR) is the rate at which subsequent flow of the virtual object can be generated per unit time. Result of statistical binomial test in Table 4 have found that the flow rate of virtual object have the effect on the incidence of eyestrain, blurred vision and dry and irritated eyes symptoms. This is because it affects the ability of the eyes to see the virtual objects as it is being generated so that the eyes experienced strain, blur and also dryness or irritation during that period. Fig. 5 (a), (b), and (c) depict the level of the symptoms experienced by users. The effect can be minimized by designing the appropriate flow rate of the virtual object generated. A flow rate at 5 seconds per piece is better than a flow rate of 10 seconds per piece to avoid blurred vision symptoms. This is because more than 69% of users do not

(a)

**4.4 Analysis of the Flow Rate (FR) of the virtual objects** 

suffer this condition at this flow rate.

Fig. 4. (a) Level of eyestrain symptoms (b) Level of blurred vision symptoms (c) Level of dry and irritated eyes symptoms

Ergonomics Design Criteria of a Virtual Environment 185

(c) Fig. 5. (a) Level of eyestrain symptom (b) Level of blurred vision symptoms (c) Level of dry

Different speeds of the virtual object motion in the VE were investigated. Statistical binomial test (Table 5) shows that users suffers from eyestrain, blurred vision and dry and irritated eyes when interacting with virtual objects at low and high speed of motion. This is because the eyes are trying to focus on the virtual object in motion which requires good coordination with the hand when performing task. Figures 6 (a), (b) and (c) shows the level of symptoms experienced by the users. It can be seen that the speed of virtual object motion needs to be considered as an attribute in designing of a VE. A higher speed of the virtual object motion is better than a lower speed. This is because at higher speeds there is no effect on users whether for eyestrain symptoms or dry and irritated eyes symptoms compared with lower speeds.

Many research have been conducted and have concluded that working with LCD screen is much more comfortable compared to working with CRT screens (Alstrom, et al, 1992; Saito, et al, 1993; Shieh,K.K., and Lin, C.C., 2000). This is contributed to the luminance contrast and limited viewing angle of LCD screens (Snyder, 1988). Additionally, the TFT-LCD screen seems to be the preferred technology by users for identifying letters on VDTs (Shieh, K.K. and Lin, C.C.,2000). In the current research, statistical binomial test (Table 6) have found that eyestrain and dry and irritated symptoms were experienced by users at three different resolution (high, medium and low resolution) whilst dry and irritated eyes incidence were experienced by users

and irritated eyes symptoms

**4.5 Analysis of the speed of the virtual objects motion** 

**4.6 Analysis of the resolution of display** 

(a)

(b)

Fig. 5. (a) Level of eyestrain symptom (b) Level of blurred vision symptoms (c) Level of dry and irritated eyes symptoms

## **4.5 Analysis of the speed of the virtual objects motion**

Different speeds of the virtual object motion in the VE were investigated. Statistical binomial test (Table 5) shows that users suffers from eyestrain, blurred vision and dry and irritated eyes when interacting with virtual objects at low and high speed of motion. This is because the eyes are trying to focus on the virtual object in motion which requires good coordination with the hand when performing task. Figures 6 (a), (b) and (c) shows the level of symptoms experienced by the users. It can be seen that the speed of virtual object motion needs to be considered as an attribute in designing of a VE. A higher speed of the virtual object motion is better than a lower speed. This is because at higher speeds there is no effect on users whether for eyestrain symptoms or dry and irritated eyes symptoms compared with lower speeds.
