4. Instruments and tests for glare

#### 4.1. CSV-1000E

levels used during disability glare testing and how that relays to realistic encounters in

Contrast sensitivity performance in photopic conditions do not always correlate with mesopic conditions. Hertenstein et al. compared contrast sensitivity under both photopic and mesopic conditions [37]. Individuals recruited for the research comprised of normal, cataract patients, and glaucoma patients. The study utilized a glare testing device known as the Mesotest for the mesopic condition while using two different visual acuity test, Freiburg Acuity and Contrast Sensitivity Test (FrACT) and the Mars Letter Contrast Sensitivity Test for the photopic condition. Furthermore, the three testing methods were also retested to assure the reliability of the results. Overall, the study demonstrated that high mesopic contrast sensitivity score correlated with high photopic contrast sensitivity score. That correlation was also true when the subjects had low photopic contrast sensitivity score and low mesopic scores. However, high photopic contrast sensitivity score did not show the same predictability because individuals with those scores had various mesopic contrast sensitivity scores [37]. This suggest that to fully understand the visual impairments of disability glare, glare must be tested in different light conditions. Disability glare is present in everyday life at various light settings and so testing in many conditions provides more applicable knowledge of impairments patients face daily. As research has shown, visual performance differs depending on lighting and one condition cannot completely predict the results of another. However, testing under mesopic conditions may provide more information about visual function because a high score correlated to good

In patients with ocular pathologies and older drivers, concerns associated with disability glare often comes from difficulty driving at night. Realistic visual problems cannot always be accurately tested in clinical examination because visual acuity only tests visual function with high contrast and in photopics conditions. A study done by Kimlin and colleagues demonstrates this flaw by assessing the predictability of visual tests on the driving performance of its subjects [38]. These subjects had little to no ocular pathologies but had trouble night time driving. The subjects were put through driving obstacles to monitor their driving performance during night time. The subjects were also tested under photopic conditions for both visual acuity and contrast sensitivity. Then, they were tested under mesopic conditions for visual acuity and contrast sensitivity as well as glare testing. The study revealed that out of all the test results, high contrast visual acuity provided the least information about driving performance. In turn, glare and mesopic conditions were better predictors and accounted for more of the driving variations in the subjects [38]. Thus, a major visual problem like night time driving cannot be captured by typical clinical settings. Visual acuity and photopic conditions cannot provide information adequate in assessing all visual complaints. Thus, proper measurements of disability glare should be done in a lighting condition that most accurately addresses the

In addition, mesopic conditions mimic those of night time illuminance as well as fog. While it has been shown that visual acuity decreases during mesopic conditions, central vision is less important and the ability to discriminate contrast becomes more necessary [39]. Thus, the effects of disability glare on contrast sensitivity during mesopic conditions can be more clini-

everyday situations.

70 Causes and Coping with Visual Impairment and Blindness

vision in both light levels.

visual complaint of interest.

cally valuable and applicable to daily life.

One widely known clinical tool to measure disability glare is the CSV-1000E from Vector Vision. This device measures disability glare using contrast sensitivity at spatial frequencies ranging from low to high. The spatial frequencies are measured using sinusoidal gratings at varying levels of contrast. The CSV-1000E has a backlit illumination of 85 cd/m2 which can be used for glare testing under photopic conditions. The device can measure in mesopic conditions as well with the use of neutral density filters which lowers illuminance to 3 cd/m<sup>2</sup> , the FDA recommended setting for mesopic measurements [40] (Figure 4).

The test consists of eight levels of contrast for each spatial frequency. There are eight columns consisting of two circles each, one which contains the sinusoidal gratings. The subject is tasked with identifying which of the two circles contain the grating for each of the columns. The responses are recorded and converted to a logarithmic scale.

Since the CSV-1000E can test in both photopic and mesopic conditions at various spatial frequencies, it has a variety of useful applications in a clinical setting. Shandiz et al. demonstrated the use of the CSV-1000E in individuals with different types of cataracts and different levels of severity. The CSV-1000E was sensitive enough to display a correlation between the subject's performance on contrast sensitivity and their level of lens opacity [41]. Since the CSV-1000E is a discriminative test that reflect ocular pathologies, it can be valuable in tracking the progression of a disease such as cataracts.

While the CSV-1000E has shown some discriminative ability, one report has shown the device is unreliable. Kelly et al. looked at the repeatability of the CSV-1000E in children and adults. The results indicated that the CSV-1000E has poor reliability. The reliability only improved in

Figure 4. CSV-1000E used for glare testing at varying luminance and contrast sensitivity at different spatial frequencies. Image courtesy of VectorVision [40].

the case of maintaining the same experimenter, but even so the reliability was still low [42]. Some issues with the study was it involved both children and adults and the groups were too small to perform a reliable sub-analysis.

Examining the reliability of the CSV-1000E with a subject of pool of glaucoma patients, the investigators found the device and testing to be reliable. The reliability was calculated as the coefficient of repeatability (COR) which was on average .191 which was lower when compared to another known glare test, the Miller-Nadler Glare Tester (COR = 0.36) [43]. The study tested the effectiveness of a beta-blocker therapy on the contrast sensitivity of open angle glaucoma and looked at the reliability of CSV-1000E. The CSV-1000E was able to detect the changes in visual function from the beta-blocker treatment which can suggest good discriminative sensitivity [43]. Furthermore, based on repeatability the results supported that CSV-1000E can be a clinically reliable tool.

The CSV-1000E is a clinically versatile device as it can measure disability glare in various conditions. The device has also shown discriminative ability in detecting the changes in state of those with cataracts and glaucoma. However, the repeatability of the test remains uncertain and so further assessment of the CSV-1000E with a large sample size will be necessary for understanding its suitability in glare testing.

The halometer showed significant correlation between the visual acuity and the digitized opacity measurements. The results indicate that this glare test can contribute additional knowledge to visual function in relation to cataracts. Furthermore, the repeatability of the halometer was also assessed. The halometer performed with high repeatability of about 0.998 with test and retest occurring 1 week apart [45]. The halometer being both discriminative and

Figure 5. Schematic of the Halometer glare device utilized by Babizhayev and colleagues to measure intraocular light

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Another modification of the halometer utilized an iPad application and an LED point light source. The halometer is known as the Aston Halometer [46] (Figure 6). The study subjects were tested monocularly with the use the Bangerter occlusion foil to induce disability glare. The target, presented at four different Weber contrast levels, was moved from the LED light source in eight different directions. The subject was to identify when the target was just visible from the light source and the distance, being the halo disk radius, was measured and analyzed. The performance of the Halometer was compared to the straylight meter which had been shown to be an accurate measurement of straylight and correlated to the amount of disability glare. The Halometer showed sensitivity to lower contrast letter and had high repeatability during testing which makes for a promising device [46]. However, the device was only tested on normal subjects without ocular pathologies. Therefore, while there is evidence in the Halometer's sensitivity to varying levels of contrast in normal subjects, the study did not provide insight to glare in ocular pathologies such cataract and glaucoma. Since the population of those living with ocular pathologies struggle with disability glare, a glare device needs to demonstrate discriminative ability in disease such as cataracts, glaucoma, and corneal

Another study also used the Aston halometer to measure disability. They did so to evaluate night time driving in older adults with minimal pathologies including cataracts, glaucoma, and corneal pathology [38]. The subjects recruited was put through a driving obstacle to monitor their driving performance. Then mesopic conditions as well as glare testing was measured to see whether the visual testing is an accurate predictor of the subject's driving. While the test showed that the Aston halometer was a better predictor than photopic high contrast visual acuity (HCVA) testing, it was not a better predictor than mesopic high contrast visual acuity testing [38]. This suggest that the Aston halometer may need other improvements to increase sensitivity

and further studies will be necessary to assess the validity of the halometer.

reliable can be a beneficial and useful addition to clinical evaluation of patients.

scatter in subjects with cataracts. Babizhayev et al. [45].

disease.

#### 4.2. Halometer

Disability glare while causing a veil of light over the visual object, can also create an illuminated ring in our viewpoint which is known as a halo. The halo can be quantified by its disk radius and be used as a mean to measure disability glare. In a study conducted by Palomo-Alvarez et al., it was demonstrated that in comparison to straylight and corrected visual distance acuity (CVDA), disk halo radius was more discriminatively sensitive at detecting differences between normal and cataract subjects under glare conditions [44]. Thus, disk halo radius can be a valuable diagnostic tool to measure disability glare in clinics. One of the current tools for measuring halos are halometers. There are several models of halometers which are adopted by researchers to fit their studies. However, the foundational principals of the different halometers for evaluating disability glare are very similar.

The halometer test mainly entails a point light source at the center of the testing screen which varies in intensity depending on the device and study. The optotype used can be illuminated with a green or red light to monitor the effects of wavelength on light scattering. The protocol usually comprises of the subject moving the optotype either away or to the light source until it is just no longer visible or just visible depending on the specific instructions. The distant from the light to the object is then measured and analyzed as the disk radius halo which correlates with the amount of disability glare experienced.

In a study performed by Babizhayev et al., the halometer was used to assess individuals with cataracts [45] (Figure 5). Additionally, the performance of the Halometer was compared to other clinical tools such as visual acuity measurements and digitized opacity representations of the lens to determine the validity of the test. The digitized representations were done with retro-illumination photography that was digitally analyzed for light scattering and absorption.

the case of maintaining the same experimenter, but even so the reliability was still low [42]. Some issues with the study was it involved both children and adults and the groups were too

Examining the reliability of the CSV-1000E with a subject of pool of glaucoma patients, the investigators found the device and testing to be reliable. The reliability was calculated as the coefficient of repeatability (COR) which was on average .191 which was lower when compared to another known glare test, the Miller-Nadler Glare Tester (COR = 0.36) [43]. The study tested the effectiveness of a beta-blocker therapy on the contrast sensitivity of open angle glaucoma and looked at the reliability of CSV-1000E. The CSV-1000E was able to detect the changes in visual function from the beta-blocker treatment which can suggest good discriminative sensitivity [43]. Furthermore, based on repeatability the results supported that CSV-1000E can be a

The CSV-1000E is a clinically versatile device as it can measure disability glare in various conditions. The device has also shown discriminative ability in detecting the changes in state of those with cataracts and glaucoma. However, the repeatability of the test remains uncertain and so further assessment of the CSV-1000E with a large sample size will be necessary for

Disability glare while causing a veil of light over the visual object, can also create an illuminated ring in our viewpoint which is known as a halo. The halo can be quantified by its disk radius and be used as a mean to measure disability glare. In a study conducted by Palomo-Alvarez et al., it was demonstrated that in comparison to straylight and corrected visual distance acuity (CVDA), disk halo radius was more discriminatively sensitive at detecting differences between normal and cataract subjects under glare conditions [44]. Thus, disk halo radius can be a valuable diagnostic tool to measure disability glare in clinics. One of the current tools for measuring halos are halometers. There are several models of halometers which are adopted by researchers to fit their studies. However, the foundational principals of

The halometer test mainly entails a point light source at the center of the testing screen which varies in intensity depending on the device and study. The optotype used can be illuminated with a green or red light to monitor the effects of wavelength on light scattering. The protocol usually comprises of the subject moving the optotype either away or to the light source until it is just no longer visible or just visible depending on the specific instructions. The distant from the light to the object is then measured and analyzed as the disk radius halo which correlates

In a study performed by Babizhayev et al., the halometer was used to assess individuals with cataracts [45] (Figure 5). Additionally, the performance of the Halometer was compared to other clinical tools such as visual acuity measurements and digitized opacity representations of the lens to determine the validity of the test. The digitized representations were done with retro-illumination photography that was digitally analyzed for light scattering and absorption.

the different halometers for evaluating disability glare are very similar.

small to perform a reliable sub-analysis.

72 Causes and Coping with Visual Impairment and Blindness

understanding its suitability in glare testing.

with the amount of disability glare experienced.

clinically reliable tool.

4.2. Halometer

Figure 5. Schematic of the Halometer glare device utilized by Babizhayev and colleagues to measure intraocular light scatter in subjects with cataracts. Babizhayev et al. [45].

The halometer showed significant correlation between the visual acuity and the digitized opacity measurements. The results indicate that this glare test can contribute additional knowledge to visual function in relation to cataracts. Furthermore, the repeatability of the halometer was also assessed. The halometer performed with high repeatability of about 0.998 with test and retest occurring 1 week apart [45]. The halometer being both discriminative and reliable can be a beneficial and useful addition to clinical evaluation of patients.

Another modification of the halometer utilized an iPad application and an LED point light source. The halometer is known as the Aston Halometer [46] (Figure 6). The study subjects were tested monocularly with the use the Bangerter occlusion foil to induce disability glare. The target, presented at four different Weber contrast levels, was moved from the LED light source in eight different directions. The subject was to identify when the target was just visible from the light source and the distance, being the halo disk radius, was measured and analyzed. The performance of the Halometer was compared to the straylight meter which had been shown to be an accurate measurement of straylight and correlated to the amount of disability glare. The Halometer showed sensitivity to lower contrast letter and had high repeatability during testing which makes for a promising device [46]. However, the device was only tested on normal subjects without ocular pathologies. Therefore, while there is evidence in the Halometer's sensitivity to varying levels of contrast in normal subjects, the study did not provide insight to glare in ocular pathologies such cataract and glaucoma. Since the population of those living with ocular pathologies struggle with disability glare, a glare device needs to demonstrate discriminative ability in disease such as cataracts, glaucoma, and corneal disease.

Another study also used the Aston halometer to measure disability. They did so to evaluate night time driving in older adults with minimal pathologies including cataracts, glaucoma, and corneal pathology [38]. The subjects recruited was put through a driving obstacle to monitor their driving performance. Then mesopic conditions as well as glare testing was measured to see whether the visual testing is an accurate predictor of the subject's driving. While the test showed that the Aston halometer was a better predictor than photopic high contrast visual acuity (HCVA) testing, it was not a better predictor than mesopic high contrast visual acuity testing [38]. This suggest that the Aston halometer may need other improvements to increase sensitivity and further studies will be necessary to assess the validity of the halometer.

over visual acuity in the case of the Berkeley Glare Test to produce more sensitive and accurate results. Furthermore, the Berkeley Glare Test also presented versatility as a glare device because the charts can be changed to test a wider range of visual function. This is potentially helpful in ocular diseases such as cataracts to evaluate different visual impairments in various settings. The Berkeley Glare Test also presented good discriminative ability as it can differen-

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Further evaluation of the validity of the Berkeley Glare Test was done by Elliot and colleagues in a study where different glare tests were also observed [28]. The test was utilized with a low contrast (Weber 15%) Bailey-Lovie chart with a back illumination of 80 cd/m2 and the glare setting was set to 750 cd/m<sup>2</sup> illumination. The Berkeley Glare Test displayed good repeatability but did not perform as well as the Regan chart and BAT (Brightness Acuity Test) as the glare source in reliability. The Berkeley Glare Test also exhibited good discriminative ability between normal and cataract patients. However, the study did disclaim that the subjects were referred to the ophthalmologist's office due to discrepancies in visual acuity. Since visual acuity in these subjects were already low, it can be expected that visual impairments were apparent enough to be easily detected by most tests. And so, these results did not further support the discriminative ability of the Berkeley Glare Test. The Berkeley Glare Test also fulfilled the three criteria of a vision test outlined by the American Academy of Ophthalmology (AAO). The criteria include: a force-choice protocol, test target follows a uniform logarithmic progression, multiple trials should be done at each level of acuity or contrast [28]. The Berkeley Glare Test's performance as outlined by the AAO criteria is both reliable and discriminative test. Therefore, the Berkeley Glare test can potentially be a strong

In another instance, a research study utilized the Berkley Glare Test to evaluate nighttime driving and disability glare. The study compared the Berkeley Glare Test to the Aston Glare Test in predicting night time driving performance. The Berkeley Glare Test did not show any significant correlation in driving performance while the Aston Glare Test displayed significant correlations [38]. This may suggest that while the Berkeley Glare Test can produce valid results, newer glare devices are surpassing it in sensitivity and leaves room for improvement

In another glare test, known as the EpiGlare tester, the inventors developed a glare testing device that has the validity and discriminative disability to detect vision loss caused by glare. Epitropoulos and colleagues assessed the changes in corrected distance visual acuity (CDVA) in cataract and normal subjects under glare conditions [48]. The EpiGlare tester is a LED light emitting device that can be attached to a phoropter. There are four LED lights placed evenly around the aperture of the device. Under induced glare conditions, the subjects are asked to read off an EDTRS chart to assess their CDVA. The study also incorporated a Functional Vision Questionnaire that assessed the subjects driving and glare experiences. An additional question was asked after glare testing on how closely the test resembled their glare problems while

tiate between those with early signs of nuclear sclerosis and normal subjects.

foundation as both a research and clinical tool.

in the test itself.

4.4. EpiGlare tester

nighttime driving (Figure 7).

Figure 6. Schematic of the Aston Halometer designed on the iPad with an LED light source and target optotype controlled by iPhone. Buckhurst et al. [46].

#### 4.3. Berkeley glare test

The Berkeley Glare Test has long been used for glare testing in clinic and research. The Berkeley Glare test measures visual acuity optotypes and different contrast levels under glare conditions [47]. A chart of varying levels of contrast is placed in the device, behind the opal Plexiglas screen which has a back illumination of 85 cd/m2 . The device has three levels of glare, being 300, 800, and 3000 cd/m<sup>2</sup> . The creators of the Berkeley Glare test, Bailey and Bullimore, tested the technique on young and older ocular healthy adults [47]. Older adults were categorized as healthy if no ocular pathologies were present and their nuclear sclerosis score was grade 1 and under. The subjects were tested under four conditions which were no glare, and the three glare illuminations mentioned earlier. The chart used in the Berkeley Glare Test can vary and be chosen to meet specific needs. Visual function at high contrast was measured using the Bailey-Lovie Chart, a letter chart that assessed visual acuity. Low contrast visual function was also measured by using a letter chart that was at a Michaelson 10% contrast. The subjects were scored on a basis of a disability glare index (DGI) which was the difference in the number of letters the subject can see in the no glare versus glare conditions. Bailey and Bullimore's testing results showed that subjects with early nuclear sclerosis had a higher reduction in disability glare in comparison to visual acuity. The data also reflected subtle changes in lens opacity in the subject's DGI score before those changes could be detected by visual acuity testing [47]. The significant difference between DGI scores suggested that the Berkeley Glare test was more sensitive to physiological changes when assessing for contrast sensitivity than visual acuity [47]. This also noted the importance of using contrast sensitivity over visual acuity in the case of the Berkeley Glare Test to produce more sensitive and accurate results. Furthermore, the Berkeley Glare Test also presented versatility as a glare device because the charts can be changed to test a wider range of visual function. This is potentially helpful in ocular diseases such as cataracts to evaluate different visual impairments in various settings. The Berkeley Glare Test also presented good discriminative ability as it can differentiate between those with early signs of nuclear sclerosis and normal subjects.

Further evaluation of the validity of the Berkeley Glare Test was done by Elliot and colleagues in a study where different glare tests were also observed [28]. The test was utilized with a low contrast (Weber 15%) Bailey-Lovie chart with a back illumination of 80 cd/m2 and the glare setting was set to 750 cd/m<sup>2</sup> illumination. The Berkeley Glare Test displayed good repeatability but did not perform as well as the Regan chart and BAT (Brightness Acuity Test) as the glare source in reliability. The Berkeley Glare Test also exhibited good discriminative ability between normal and cataract patients. However, the study did disclaim that the subjects were referred to the ophthalmologist's office due to discrepancies in visual acuity. Since visual acuity in these subjects were already low, it can be expected that visual impairments were apparent enough to be easily detected by most tests. And so, these results did not further support the discriminative ability of the Berkeley Glare Test. The Berkeley Glare Test also fulfilled the three criteria of a vision test outlined by the American Academy of Ophthalmology (AAO). The criteria include: a force-choice protocol, test target follows a uniform logarithmic progression, multiple trials should be done at each level of acuity or contrast [28]. The Berkeley Glare Test's performance as outlined by the AAO criteria is both reliable and discriminative test. Therefore, the Berkeley Glare test can potentially be a strong foundation as both a research and clinical tool.

In another instance, a research study utilized the Berkley Glare Test to evaluate nighttime driving and disability glare. The study compared the Berkeley Glare Test to the Aston Glare Test in predicting night time driving performance. The Berkeley Glare Test did not show any significant correlation in driving performance while the Aston Glare Test displayed significant correlations [38]. This may suggest that while the Berkeley Glare Test can produce valid results, newer glare devices are surpassing it in sensitivity and leaves room for improvement in the test itself.

#### 4.4. EpiGlare tester

4.3. Berkeley glare test

being 300, 800, and 3000 cd/m<sup>2</sup>

controlled by iPhone. Buckhurst et al. [46].

74 Causes and Coping with Visual Impairment and Blindness

The Berkeley Glare Test has long been used for glare testing in clinic and research. The Berkeley Glare test measures visual acuity optotypes and different contrast levels under glare conditions [47]. A chart of varying levels of contrast is placed in the device, behind the opal

Figure 6. Schematic of the Aston Halometer designed on the iPad with an LED light source and target optotype

tested the technique on young and older ocular healthy adults [47]. Older adults were categorized as healthy if no ocular pathologies were present and their nuclear sclerosis score was grade 1 and under. The subjects were tested under four conditions which were no glare, and the three glare illuminations mentioned earlier. The chart used in the Berkeley Glare Test can vary and be chosen to meet specific needs. Visual function at high contrast was measured using the Bailey-Lovie Chart, a letter chart that assessed visual acuity. Low contrast visual function was also measured by using a letter chart that was at a Michaelson 10% contrast. The subjects were scored on a basis of a disability glare index (DGI) which was the difference in the number of letters the subject can see in the no glare versus glare conditions. Bailey and Bullimore's testing results showed that subjects with early nuclear sclerosis had a higher reduction in disability glare in comparison to visual acuity. The data also reflected subtle changes in lens opacity in the subject's DGI score before those changes could be detected by visual acuity testing [47]. The significant difference between DGI scores suggested that the Berkeley Glare test was more sensitive to physiological changes when assessing for contrast sensitivity than visual acuity [47]. This also noted the importance of using contrast sensitivity

. The device has three levels of glare,

. The creators of the Berkeley Glare test, Bailey and Bullimore,

Plexiglas screen which has a back illumination of 85 cd/m2

In another glare test, known as the EpiGlare tester, the inventors developed a glare testing device that has the validity and discriminative disability to detect vision loss caused by glare. Epitropoulos and colleagues assessed the changes in corrected distance visual acuity (CDVA) in cataract and normal subjects under glare conditions [48]. The EpiGlare tester is a LED light emitting device that can be attached to a phoropter. There are four LED lights placed evenly around the aperture of the device. Under induced glare conditions, the subjects are asked to read off an EDTRS chart to assess their CDVA. The study also incorporated a Functional Vision Questionnaire that assessed the subjects driving and glare experiences. An additional question was asked after glare testing on how closely the test resembled their glare problems while nighttime driving (Figure 7).

Figure 7. EpiGlare tester designed by Dr. Alice Epitropoulos can be easily attached to phoropter for clinical use. Image courtesy of good-Lite. Epitropoulos et al. [48].

From the data of 40 subjects with cataracts and 49 ocular healthy subjects, EpiGlare tester demonstrated that cataract subjects are more impaired by disability glare than normal subjects [43]. These findings support the discriminative ability of the EpiGlare tester to distinguish the visual loss between pathology and healthy vision. Furthermore, the questions asked during the testing provides additional evidence to the validity of the device. From all the subjects, 83% of the cataract subjects reported the device accurately simulated their difficulties nighttime driving [48]. The device was easy to utilize and incorporate in clinical settings. The attachment to phoropter increases repeatability of the glare tester because the device setup will be consistent. The study did not directly examine its reliability and thus further evaluation of the device is still necessary. However, the EpiGlare tester simple use can be advantageous in clinical settings with its discriminative sensitivity and convenience.

#### 4.5. Ophthimus glare tester versus contrast sensitivity function glare test

While there can be many variations among glare devices, the core of what is required in glare testing is the same. Therefore, there are several present methods and devices that share similar set ups. Two of which are the Ophthimus Glare Tester (Hightech Vision) and the contrast sensitivity function (CSF) glare tester created by Abrahamsson and his colleagues [21, 49]. Both these models examine cataract and normal subjects as well as monitoring their visual performance with contrast sensitivity under glare conditions (Figures 8 and 9).

These devices employed similar setups by using a ring fluorescent tube as the glare source with the optotype presented in the middle. Both assessed contrast sensitivity; however, the Ophthimus Glare Test utilized the Landolt C with varying levels of contrast as its optotype [21]. The CSF Glare Tester, on the other hand, used sinusoidal gratings to measure contrast sensitivity with different contrast levels and spatial frequencies [49]. Furthermore, the type of glare sources differed, and the intensity of both glare sources were not disclosed. Hence, there is no basis to compare the two on illuminance.

When using the Landolt C, the protocol normally ensued a force choice answer. In the case of Ophthimus Glare Tester, the subjects were asked to report which direction the gap of the Landolt C was facing. This was done until the subject reached the lowest contrast in which the direction of the Landolt C could still be answered correctly [21]. This resembled the procedure of the CSF tester as the sinusoidal gratings were gradually increased to the contrast that was

Figure 9. Schematic of Abrahamsson and Sjostrand glare device with a ring light as the glare source and sine wave

contrast sensitivity in the center. Abrahamsson and Sjostrond [21].

Figure 8. Schematic of the Ophthimus glare test with the ring light as the glare source and Landolt C at the center. Martin

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[49].

Figure 8. Schematic of the Ophthimus glare test with the ring light as the glare source and Landolt C at the center. Martin [49].

From the data of 40 subjects with cataracts and 49 ocular healthy subjects, EpiGlare tester demonstrated that cataract subjects are more impaired by disability glare than normal subjects [43]. These findings support the discriminative ability of the EpiGlare tester to distinguish the visual loss between pathology and healthy vision. Furthermore, the questions asked during the testing provides additional evidence to the validity of the device. From all the subjects, 83% of the cataract subjects reported the device accurately simulated their difficulties nighttime driving [48]. The device was easy to utilize and incorporate in clinical settings. The attachment to phoropter increases repeatability of the glare tester because the device setup will be consistent. The study did not directly examine its reliability and thus further evaluation of the device is still necessary. However, the EpiGlare tester simple use can be advantageous in clinical

Figure 7. EpiGlare tester designed by Dr. Alice Epitropoulos can be easily attached to phoropter for clinical use. Image

While there can be many variations among glare devices, the core of what is required in glare testing is the same. Therefore, there are several present methods and devices that share similar set ups. Two of which are the Ophthimus Glare Tester (Hightech Vision) and the contrast sensitivity function (CSF) glare tester created by Abrahamsson and his colleagues [21, 49]. Both these models examine cataract and normal subjects as well as monitoring their visual

These devices employed similar setups by using a ring fluorescent tube as the glare source with the optotype presented in the middle. Both assessed contrast sensitivity; however, the Ophthimus Glare Test utilized the Landolt C with varying levels of contrast as its optotype [21]. The CSF Glare Tester, on the other hand, used sinusoidal gratings to measure contrast sensitivity with different contrast levels and spatial frequencies [49]. Furthermore, the type of glare sources differed, and the intensity of both glare sources were not disclosed. Hence, there

settings with its discriminative sensitivity and convenience.

courtesy of good-Lite. Epitropoulos et al. [48].

76 Causes and Coping with Visual Impairment and Blindness

is no basis to compare the two on illuminance.

4.5. Ophthimus glare tester versus contrast sensitivity function glare test

performance with contrast sensitivity under glare conditions (Figures 8 and 9).

Figure 9. Schematic of Abrahamsson and Sjostrand glare device with a ring light as the glare source and sine wave contrast sensitivity in the center. Abrahamsson and Sjostrond [21].

When using the Landolt C, the protocol normally ensued a force choice answer. In the case of Ophthimus Glare Tester, the subjects were asked to report which direction the gap of the Landolt C was facing. This was done until the subject reached the lowest contrast in which the direction of the Landolt C could still be answered correctly [21]. This resembled the procedure of the CSF tester as the sinusoidal gratings were gradually increased to the contrast that was barely visible to the subject under glare conditions. The task was done at all spatial frequencies [49]. Both glare test measured the lowest contrast level visible by the subject to determine their contrast sensitivity. These results were both used to calculate a glare score which was used to understand the visual function of the cataract subjects and ocular healthy subjects.

Author details

Pomona CA, USA

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1 Western University of Health Sciences, College of Osteopathic Medicine of the Pacific,

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[11] Mäntyjärvi M, Laitinen T. Normal values for the Pelli-Robson contrast sensitivity test. Journal of Cataract & Refractive Surgery. 2001;27(2):261-266. DOI: 10.1016/s0886-3350(00)

2 Western University of Health Sciences, College of Optometry, Pomona CA, USA

Their shared similarities in testing methods also yielded the same results where both glare tests displayed discriminative ability between cataract subjects and age-matched ocular healthy subjects. However, each study correlated their glare score with different measurements and so each drew their own specific inferences from their results. The Ophthimus Glare Tester study looked at cataract patients in preparation for cataract surgery. These individuals had normal visual acuity, but the results of the study showed their disability glare score to be significantly lower and they also reported visual complaints associated with glare. After the surgery, 24 out of 25 subjects had no self-reported glare problems but some of the subjects still displayed elevated glare sensitivity [21]. This supported the discriminative ability of the Ophthimus Glare Tester that the glare test could still distinguish between cataracts and ocular healthy individuals even after surgery when visual function improved. The validity of the Ophthimus Glare Tester's performance was supported by being relevant to the subjective visual complaints of the subjects as well as with the results of preoperative and postoperative surgery. The CSF glare tester, on the other hand, measured their scores against opacity levels of the cataract subjects. They demonstrated a correlation between the glare scores and the current pathology of each subject [49]. Hence, the validity that the CSF glare tester was based more so on physiological progress of the disease rather than subjective experiences. Both these glare tests exhibited strong discriminative findings but because the studies that utilized the tests based their results on different foundations, the information yielded by each glare testing device was distinctive. This also applied to the information each study provided about the effects of glare on cataracts even though the glare tests shared a number of similarities. And so more testing should be conducted to assess the comparative validity of these glare tests.
