Field of the Invention

[0001] The present invention relates to the measurement of glare and a device for such use.

Background of the Invention

[0002] Glare is a visual experience, defined as difficulty or discomfort seeing in the presence of either bright or reflected natural or artificial light. It can also be described as the ability or inability to recover after the removal of either bright or reflected light. Problems with glare tend to be greater in older individuals, individuals with cataracts, individuals with ocular diseases and after acquired brain injury.

[0003] Glare is an important consideration in functional visual assessments for vision rehabilitation purposes. Glare is also an important consideration when making decisions about medical or surgical management of ocular diseases such as cataracts.

Summary of the Invention

[0004] Forming one aspect of the present invention is a device to aid in the measurement of glare experienced by an individual, the device comprising: a head mount adapted to be releasably mountable on the head of the individual; and one or more light sources secured to the head mount, the one or more light sources being positioned such that, when the head mount is operatively positioned on the head, the light sources shine light simultaneously into both eyes of the individual, the light being adapted to elicit a predetermined Veiling Luminance (Disability Glare Veiling Luminance.) based on the age of the individual

[0005] Other aspects of the present invention are methods and uses of the above noted device to aid in the measuring of glare experienced by an individual.

One method comprises: taking a first baseline visual measurement; shining light into both eyes of the individual simultaneously using the present device to elicit a predetermined veiling luminance based on the age of the individual; taking a second visual measurement; and calculating a glare sensitivity measurement from the first and second visual measurements.

Another method comprises: taking a first baseline visual measurement; shining light into both eyes of the individual simultaneously using the present device to elicit a predetermined veiling luminance based on the age of the individual for a specified period of time; removing the light source and waiting another specified period of time; taking a second visual measurement; and calculating a glare recovery measurement from the first and second visual measurements.

[0006] Other advantages, features and characteristics of the invention will become apparent upon review of the detailed description, with reference to the appended drawings, the latter being briefly described hereinafter. Brief Description of the Drawings

[0007] Figure 1 is a bottom perspective view of a device according to an embodiment of the present invention in an off mode.

[0008] Figure 2 is a side elevational view of the device of Figure 1 in an on mode in use on an individual's head.

[0009] Figure 3 is a flowchart illustrating the steps of a method using the device of Figure 1 according to another embodiment of the present invention.

Detailed Description

Device

[0010] Referring to Figures 1-2, there is shown a device 10 that forms an embodiment of the invention. Device 10 includes a head mount 12, one or more light sources 14 and a bar 28.

[0011] Head mount 12 is adapted to be releasably mountable to the head of an individual. In the depicted embodiment, head mount 12 is a baseball cap 18 with a crown portion 20 and a brim or visor 22 attached thereto. As readily understood by those skilled in the art, baseball cap 18 is adjustable to fit onto different heads with different circumferences. Visor 22 is pliable and pliably secured to crown portion 20. In this manner, the angle at which visor 22 extends from crown portion 20 may be adjusted as desired, and the curvature of visor 22 may be modified as desired. Visor 22 has an underside 24 that is also shown to be opaque.

[0012] The one or more light sources 14 are secured to head mount 12 and are adapted to elicit a predetermined veiling luminance based on the age of the individual. Glare may be referred to as, or measured in, Veiling Luminance or Disability Glare Veiling Luminance. Veiling luminance varies with age as illustrated in Table 1 below. Table 1 sets out the range of veiling luminance produced by device 10 according to age for adults. For example, the minimum veiling luminance produced by the present invention is at least 65 cd/m ² equivalent luminance for a 25-year-old. The veiling luminance indicates the glare which is produced by device 10. It estimates the amount of stray light scattered on top of the retinal image (which causes the glare) and this estimate varies with age (due to age changes in the eye) ¹ . The measurements of glare with the invention show the effect that glare has on the individual, as the effect of glare varies with the individual. Device 10 creates a significant glare source, and the veiling luminance that it actually produces is measured. We estimated the maximum and minimum from the variability of the LEDs that are used. The effect of veiling luminance on the individual can be measured as the ratio or difference of visual function, measured without and with the glare source turned on.

Table 1 :

[0013] In the present embodiment, the one or more light sources 14 is a strip of LED lights 26, the strip measuring approximately 10 cm long with 6 LED lights embedded therein, capable of emitting a white light. LED strip 26 is further coupled to a power source 16. As depicted, LED strip 26 is secured transversely to underside 24 of visor

1 R. B. Gibbons and C. J. Edwards, “A review of disability and discomfort glare research and future direction” 18th

Biennial TRB Visibility Symposium, College Station TX, United States, 17-19 April.2007 22. Power source 16 in the depicted embodiment is electrically coupled to LED strip 26 and comprises a battery 30.

[0014] LED strip 26 is mounted on bar 28 and secured on visor 22, which is attached to head mount 12. Bar 28 is secured transversely to visor 22 parallel to LED strip 26 and extends generally perpendicularly from visor 22.

[0015] While a single embodiment of device 10 is described, variations are possible. For example, rather than baseball cap 18, head mount 12 may be a visor with a strap and visor, but without crown portion 20.

[0016] In another example, example device 10 may further include a variable resistor that is operatively coupled to one or more light sources 14. Such a variable resistor may be a rheostat. This would allow lower amounts of glare to be produced than the minima stated in Table 1.

[0017] In yet another example, rather than a portable power source, power source 16 may be a wall outlet.

Method

[0018] Referring to Figure 3, an embodiment of a method 300 is described. In this embodiment of the method, a device 10 as described above and generally as indicated in FIG. 1, but modified by the inclusion of a variable resistor, is used. In that regard, uses of device 10 are also described herein.

[0019] At 302, device 10 is releasably mounted on the head of an individual, with one or more light sources 14 (turned off), i.e. LED strip 26, positioned proximately above both eyes of the individual. When device 10 is baseball cap 18, baseball cap 18 is fitted onto the individual's head with visor 22 and LED strip 26 positioned above the individual's face such that the glare from light source 14 will shine within the field of view of the individual.

[0020] At 303, prior to turning on the light source, a first measurement of the individual's visual function is taken with LED strip 26 off. For example, a measurement of visual acuity without the presence of glare. The first visual measurement may be used as a baseline measure as discussed further below.

[0021] At 304, given the pliable nature of visor 22, LED strip 26 is adjustable relative to the individual's eyes by adjustment of visor 22.

[0022] Method 300 further includes shining light into both eyes of the individual simultaneously at 306. In some cases, measurements may be taken monocularly (one eye at a time) by covering one eye or having the individual close one eye. Since LED strip 26 is positioned above the individual's face, one or more light sources 14 is thus, positioned on head mount 12 to shine light simultaneously into both eyes from above. Bar 28 and visor 22, in turn, help to direct light from LED strip 26 towards both eyes of the individual. With light source 14 being positioned close to the individual's eyes and covered by visor 22 of baseball cap 18, this helps to reduce the impact of variable background illumination on the intensity of veiling luminance being produced by device 10.

[0023] In alternate applications, the light may be shined simultaneously into both eyes from the side or below. In such cases, an opaque visor placed to the sides or below the individual's eye may be used to reduce variable background light from that direction and standardise the glare elicited.

[0024] At 308, depending on the glare measurement to be taken and its purpose, the intensity of one or more light sources 14 may be adjusted. In some applications, the intensity of light may be increased until a decrease in the individual's performance was found. In such a case, the individual characteristic would be that individual's tolerance or threshold for glare. The intensity of the light may be adjusted, for example, using the variable resistor described above. Usually a standard positioning of the device would be used so that consistent illumination would be received by all individuals. Alternately, or additionally, the position of one or more light sources 14 may also be adjusted depending on characteristics of the individual. For example, the light position may be adjusted based on the whether or not the individual wears glasses, or based on his or her face shape or nose bridge.

[0025] The visual measurement is then taken at 310 when LED strip is on. For the example above, visual acuity would be measured with the LED glare source turned on. A glare measurement, or a glare sensitivity measurement, may then be calculated from the first (baseline) and second visual measurements. The glare sensitivity measurement may be the difference or ratio of the visual function measurements without and with the LED strip lights on.

[0026] While an embodiment of method 300 is described, variations are possible. For example, rather than a glare sensitivity measurement, a glare recovery measurement may be taken. In order to take the glare recovery measurement, LED strip 26 of device 10 is first turned on for a specified period of time, and then turned off (i.e. the light is removed). After waiting another specified period of time, visual function is measured again after the LED strip is turned off at 310, i.e. a second visual measurement is taken. This second visual measurement is compared to the first visual measurement or baseline taken at 303, and the glare recovery measurement may be calculated from the first and second visual measurements. Additionally or alternatively, the time elapsed for visual function to return to baseline after exposure to glare is measured.

[0027] As noted above, depending on the glare measurement to be taken and its purpose, the intensity of one or more light sources 14 may be adjusted at a different step in method 300. In some applications, the intensity of light may be increased until a decrease in the individual's performance was found as compared to the baseline value.

[0028] In another embodiment of method 300, releasably mounting device 10 to the individual's head is optional. For example, one or more light sources 14 may simply be held above both of the individual's eyes. In yet another embodiment, adjusting the position of light sources 14 relative to the individual's eyes is optional because, for example, such adjustment may be unnecessary if the light source is already optimally positioned relative to the individual's eyes. In yet another embodiment, adjusting the intensity of light sources 14 is also optional because, for example, such adjustment may also be unnecessary. In this embodiment, the adjustment means, that is, the variable resistor or the like, is not required.

[0029] While method 300 is described using device 10, a different device may be used to perform method 300. Device 10 may also be used to help in taking a glare measurement in a method other than that described in method 300.

[0030] The device and method have been tested, as discussed below.

[0031] For the purpose of testing, glare sensitivity and glare recovery were measured using a high-contrast static visual acuity chart as the target (Early Treatment Diabetic Retinopathy Study (ETDRS) or Berkley Rudimentary Vision Test (BRVT) charts). With the device in place on the individual, but with the light source off, baseline visual acuity was first measured. In the present case, the baseline visual acuity measurement was made with the individual wearing present device 10. The presence of visor 22 standardizes the individual's light exposure, as compared to a scenario if no visor were present. In the latter situation glare from other sources e.g. overhead lights might be added to that provided by the invention causing variability in the amount of glare created. [0032] After the baseline measurement of visual acuity without glare was made, and the glare source was applied, measurement of visual acuity in the presence of glare was made. Once the measurement of visual acuity in the presence of glare was complete, the light source was turned off and the test subject was given 1 minute to rest with eyes open under normal light exposure. Visual acuity was again measured 1 minute after the light source was turned off to calculate glare recovery.

[0033] The glare sensitivity measurement used was a measure of how much the presence of glare reduced vision. It was measured by assessing vision in the absence of glare, then assessing vision again in the presence of glare in order to determine how much the glare changed the visual performance of the subject.

[0034] The glare recovery measurement used was a measure of how quickly the vision of the subject returned to normal after exposure to a glare. In the present study, a baseline vision assessment was done, followed by exposure to the light source. The light source was then removed for a period of time before the vision of the subject was re-assessed. Glare recovery was quantified as either how much visual impairment is still present after a fixed recovery period (difference in visual performance from baseline). Glare recovery can also be quantified in terms of how long it takes for the vision of the subject to return to the normal, pre-glare state (time for visual performance recovery).

[0035] Glare sensitivity and glare recovery were measured either as the difference between performance without and with glare, or the ratio of these measures. Glare sensitivity was calculated so that a positive value indicates poorer performance in the presence of glare, or in the case of glare recovery, a positive value indicates poorer performance than at baseline. Depending on the units of the visual function being used, the formula used to calculate glare sensitivity or glare recovery varied slightly, as discussed below. When measuring logMAR. visual acuity, lower visual acuity scores indicated better performance, whereas, when measuring contrast sensitivity, a higher score indicated better performance.

[0036] The equations of glare sensitivity and glare recovery calculations for logMAR visual acuity and contrast sensitivity used in the study are given below. In both cases, it was calculated so that a positive value indicated worse performance due to glare.

Glare sensitivity for logMAR visual acuity:

Glare Sensitivity = [-1] * [Vision Performance Baseline - Vision Performance Glare]

[0037] If the presence of glare reduced vision, the glare performance value was more positive than the baseline vision performance value, and glare sensitivity was a positive value. If the presence of glare improved vision, glare performance value was more negative than the baseline vision performance value, and glare sensitivity was negative.

Glare recovery for logMAR visual acuity (for a fixed recovery period):

Glare Recovery = [-1] * [Vision Performance Baseline - Vision Performance Recovery]

[0038] If vision returned to normal in the time allowed, then glare recovery equaled zero (no difference). If performance improved in the time allowed after glare was removed (visual acuity score was lower than baseline), then glare recovery score was negative. If vision did not return to normal, then the visual acuity score after glare was removed was higher, and the glare recovery score was a positive value.

Glare sensitivity for contrast sensitivity:

Glare Sensitivity = [Vision Performance Baseline - Vision Performance Glare]

[0039] If the presence of glare reduced vision, the glare performance value was less positive than the baseline vision performance value, and glare sensitivity was a positive value. If the presence of glare improved vision, glare performance value was more positive than the baseline vision performance value, and glare sensitivity was negative.

Glare recovery for contrast sensitivity (for a fixed recovery period):

Glare Recovery = [Vision Performance Baseline - Vision Performance Recovery]

[0040] If vision returned to normal in the time allowed after glare removal, then glare recovery equaled to zero (no difference). If performance improved after glare removal (contrast sensitivity score was higher than baseline), glare recovery score was negative. If vision did not return to normal, then the contrast sensitivity score after glare removal was lower, and the glare recovery score was a positive value.

Studies

Low Vision vs. Controls

[0041] Glare sensitivity and glare recovery were measured in 34 individuals with vision impairment (age 26.2 ± 9.21 years (range 10 to 58 years)) and 18 controls of similar age (27.8 ± 8.21 years (range 10 to 44) with normal vision. Glare sensitivity and glare recovery measurements were made using the ETDRS visual acuity charts in controls. The individuals with vision impairment who participated in this study had a wide range of different types of vision impairments, including types of vision loss that affected visual acuity, contrast sensitivity, and visual field extent. Due to the wide range of vision loss in the group with vision impairment, one type of visual acuity chart could not be used for all participants. Both the ETDRS and BRVT visual acuity charts were used in the individuals with vision impairment. The results are shown in Table 2. Table 2: Baseline (logMAR), glare sensitivity (AlogMAR Baseiine-Giare), and glare recovery (AlogMAR Baseiine-Giare) values for individuals with vision impairment and age matched controls. indicates va ues that were significantly different from baseline visual acuity at p<0.001

[0042] It was found that visual acuity significantly decreased (p<0.01) in the presence of glare in both controls and individuals with vision impairment. However, as expected, the reduction in visual acuity was much larger for the individuals with vision impairment. The difference between groups was statistically significant for glare sensitivity (p<0.001) and glare recovery (p=0.035).

[0043] These results suggest that the present invention is capable of producing a binocular glare stimulus that has a negative impact on visual acuity.

[0044] As two different visual acuity charts were used to measure visual acuity in the low vision group (ETDRS and BRVT), it was also found that the present device and method worked with both types of charts and could be used for individuals with different visual abilities. The individuals with different visual abilities are the low vision individuals, who 1) had a wide range of visual abilities within this group, and 2) were different than the normal vision group. In addition, these results suggest that the impact of bright light on visual function has much greater impact in individuals with vision impairment compared to individuals with normal vision.

Older Individuals

[0045] 40 individuals (ages 45 to 73 years) without vision impairment were recruited to participate in this study. Older individuals were recruited because glare is expected to increase with age. The aims of this study were to: 1) measure glare sensitivity and glare recovery in order individuals using the present device and method, 2) to measure glare sensitivity and glare recovery on a variety of clinical measures, 3) to compare measurements of glare sensitivity and glare recovery with glare related symptoms, and 4) to assess test-retest repeatability of glare sensitivity and glare recovery measurements taken using the present device and method.

[0046] All participants attended a single study visit where static visual acuity (ETDR.S chart), contrast sensitivity (Peli-Robson chart), low contrast static visual acuity (moV&, V&mp Vision Suite), and dynamic visual acuity (moV&, V&mp Vision Suite) were measured. Additionally, 20 individuals were randomly selected to complete a second study visit (60 study visits total).

[0047] Baseline visual function measurements without glare were taken for all visual functions. Glare sensitivity and glare recovery were then measured for each of the visual functions in turn. The order of the visual functions for which glare sensitivity and glare recovery were measured was randomized between participants. Glare recovery was measured 1 minute after the glare source was turned off to calculate glare recovery. [0048] Preliminary analysis indicates that glare sensitivity and glare recovery measures could be made on all individuals on all four clinical tests chosen, using the present device and method. Non-parametric Spearman correlations were used to look at the relationship between baseline visual functions, glare sensitivity, and glare recovery with both age and glare symptoms. A Wilcoxon Signed Rank Test was used to compare the visit one and visit two data.

[0049] Baseline static visual acuity (r = 0.260, p = 0.044) and low contrast visual acuity (r = 0.296, p = 0.022) demonstrated significant positive correlations with age (i.e. as participants got older, static visual acuity and low contrast visual acuity increased or got worse). Glare sensitivity on the contrast sensitivity test demonstrated a significant positive correlation with age (r = 0.265, p = 0.040) which means that as participants got older, the presence of glare reduced their contrast sensitivity more (i.e. their glare sensitivity on this task was greater).

[0050] In addition, glare recovery on the contrast sensitivity task demonstrated a significant positive correlation with symptoms of glare (r = 0.255, p = 0.050), as did glare sensitivity measured on the dynamic visual acuity task (r = 0.321, p = 0.012). These findings suggest that increased symptoms of glare are correlated with more glare sensitivity and poorer glare recovery in challenging visual conditions (i.e. low contrast or movement).

[0051] Baseline, glare sensitivity, and glare recovery values were not significantly different between visit one and visit two for any of the visual functions measured (p-value range: 0.055 to 0.964) i.e. repeatability is good.

[0052] The mean difference between the first and second visits and the 95% limits of agreement (1.96*SD of the differences) were calculated for each of the measures and are shown in Table 3 below. Table 3: Repeatability. Mean differences and 95% limits of agreement between 2 visits.

[0053] The data all show very little mean difference between the first and second visit. The limits of agreement for static visual acuity were similar to the limits of agreement reported in the literature, see Lovie-Kitchin, J.E., Brown, B. "Repeatability and Intercorrelations of Standard vision tests as a function of age", Optom Vis Sci , 412-420 (2000).

[0054] The other measures show slightly higher limits of agreement than in the literature, see also Dougherty, B.E., Flom R.E., Bullimore, M.A. "An evaluation of the Mars Letter Contrast Sensitivity Test", Optom Vis Sci, 82, 970-975 (2005). However, this is expected, since the limits of agreement in the literature are for single measures of visual acuity or contrast sensitivity, while the measure for glare sensitivity and recovery rely on the difference of two measures which would increase the variability.

[0055] The limits of agreement for dynamic visual acuity are higher on the glare recovery task only. This test includes the additional factor of eye movements and is a more difficult task than static visual acuity. Test-retest repeatability on the dynamic visual acuity task has also been shown to be poorer in more difficult task conditions (i.e worse with low contrast targets than high contrast black targets) ² - ³ ' ⁴ . Therefore, the increased difficulty of the dynamic visual acuity task relative to the other static charts used, may account for this increase in variability. Overall, the results indicate good repeatability for the present device and method.

Findings

[0056] The present device and method can be used in repeatable ways to measure glare sensitivity and glare recovery using different clinical measures, such as static visual acuity, contrast sensitivity, low contrast visual acuity, and dynamic visual acuity. In addition, the present analysis suggests that glare sensitivity and glare recovery measured with the present device and method get worse with age (when using a contrast sensitivity chart) and that symptoms of glare are associated with worse glare sensitivity and glare recovery on visual function tasks such as dynamic visual acuity and contrast sensitivity. The findings of this study also suggest that the present device and method can be used to measure glare sensitivity and glare recovery on a number of different tasks and that measurements of glare sensitivity and glare recovery using the present device and method are repeatable.

[0057] Persons of ordinary skill will readily appreciate that the above described device 10 and method 300 are useful for a variety of reasons, can be used to measure any visual function, and provide a number of advantages over known glare

2 High contrast Dynamic VA vs. Static VA test-retest: Hirano M, Hutchings N, Simpson T, and Dalton K. Validity and repeatability of a novel dynamic VA system. Optometry and Vision Science, 2017; 94(5): 616-25.

3 Dynamic VA low contrast / colour worse than high contrast: 1) Hirano M, Hutchings N, Simpson T, Dalton K. The effect of optotype contrast and chromaticity on dynamic visual acuity. Optom Vis Sci 2017; 94: E-abstract 170084. [Paper]; 2) Hirano M, Hutchings N, Simpson T, Dalton K. Investigation of the repeatability of the low contrast and chromatic functions of a novel dynamic visual acuity test. Optom Vis Sci 2017; 94: E-abstract 175182. [Poster]

4 Hirano M. The validation of a novel dynamic visual acuity test, and examination of the effects of different factors on dynamic visual acuity. MSc thesis, published in UW Space at: http://hdl.handle.net/10012/13336 measurement devices and methods. For example, testing with both eyes open allows for a relatively natural test environment and may provide a more accurate idea of how glare sensitivity will impact a subject in day to day living.

[0058] The subject may use his or her own spectacles or tints or other visual aid, or lenses in a trial frame when using device 10 or performing method 300, thereby providing the potential for a more accurate representation of glare impact.

[0059] Device 10 and method 300 may be used with visual targets of any size, thereby to permit assessment of subjects with both normal and very poor vision. Device 10 and method 300 may also be used with any chosen measure of vision (i.e. it is not restricted to static letter charts) or vision function (i.e. in a driving simulator).

[0060] With the use of LED lights, the same light level may be applied to all individuals. LED lights also allow relatively bright light to be generated near the eyes that has relatively low levels of heat production (making it both safe and comfortable) and relatively constant brightness and colour.

[0061] Device 10 and method 300 may be used with a wide range of background illumination. Since the glare source sits close to the eye, light producing glare is less affected by that background illumination. Moreover, visor 22 helps eliminate environmental stray light, allowing for a more consistent veiling luminance. Device 10 also does not detrimentally decrease the functional field of view of the wearer.

[0062] Device 10 and method 300 may be used with any desired target (e.g. letters, numbers, contrast sensitivity gratings) of any size and can measure glare binocularly or monocularly (e.g. with a patch over the non-testing eye).This allows for a consistent amount of veiling luminance to be produced for each target viewed. [0063] Device 10 and method 300 allow the individual being tested to move around and/or perform tasks with both hands while the glare test is being conducted. Thus, testing may be performed outdoors, or the wearer may have their hands free for engaging driving simulators or control panels, for example. The device 10 also allows the LED lights to remain in a constant position, even with head or body movement.

[0064] It will be apparent to persons of ordinary skill in the art that various modifications and adaptation of the structure and method described above are possible, as are modifications and adaption of the measurements of glare sensitivity and glare recovery. Accordingly, the invention should be understood to be limited only by the appended claims, purposively construed.