A New Color Vision Test to Differentiate Congenital and Acquired Color Vision Defects

Dyschromatopsia and contrast sensitivity changes in COVID-19 patients

PURPOSE

To evaluate the alterations in the psycho-physical tests, contrast sensitivity (CS) and hue discrimination (total estimation score, TES) in COVID-19 patients.

METHODS

A prospective case-control study was undertaken in 2021-22 to look at CS and TES among COVID-19 patients and RT-PCR negative normal subjects by a mobile app "smart optometry" and X-Rite's free online version of Farnsworth-Munsell 100 hue test. Strict visual acuity (minimum of 6/9 equivalent on Snellen) and other clinical parameters were used as exclusion criteria to filter potentially confounding pre-receptoral co-morbid conditions. The effect of mismatch in recruiting age and sex matched controls during the pandemic were analyzed by multivariate linear regression.

RESULT

One-way ANOVA ruled out any influence of gender on CS and TES; however, there was significant difference in the TES on Mann Whitney U test (TES- 2.95 +/- 3.8 for cases; 0.30 +/- 1.1 for controls; p <0.001) and it persisted after accounting for age. Six controls with breakthrough infections had a significant deterioration in TES (Mean scores -3.0; 95% CI = -5.89 to -0.11; p = 0.04) on paired t test. Qualitative analysis showed that S-cone mediated deficiencies outnumber those affecting M-L cone mediated deficiencies. Among 53 subjects exhibiting three sensory features, anosmia, loss of taste and dyschromatopsia, nine (16.98%) had all features concurrently.

CONCLUSION

The study demonstrates that COVID-19 infection leads to altered TES representing dyschromatopsia -an ocular counterpart of anosmia, with little difference on CS.

Evaluating the level of visual acuity to minimise false-positives in different colour vision tests

CLINICAL RELEVANCE

Accurate colour vision assessment is important in clinical settings to minimise false-positive errors and enhance the reliability of diagnoses outcomes.

BACKGROUND

Colour vision testing is valuable in assessing the visual system, particularly given the high proportion of individuals with poor vision. This study aimed to determine the minimum visual acuity level required to perform a colour-vision test without errors.

METHODS

After fogging the right eyes of 52 healthy participants using plus lenses to 1.60 logMAR, vision was evaluated using Ishihara, Hardy - Rand - Rittler Standard Isochromatic, Waggoner Pseudo-isochromatic, City University, Waggoner Computerised, and Farnsworth D-15 tests. Participants then completed these tests at lower fogging degrees (in 0.1-logMAR intervals). The acuity at which 5% of the tested population was considered abnormal was determined.

RESULTS

Significant differences were found in the average visual acuity required to perform colour vision tests without errors (p < 0.05). The Waggoner Computerized test required the highest average visual acuity among the tests utilised. The Farnsworth D-15 test yielded the highest logMAR values. No significant differences were observed between the Waggoner Pseudo-isochromatic test and Hardy - Rand - Rittler Standard Isochromatic, Ishihara, and Farnsworth D-15 tests (p > 0.05). Additionally, no significant differences were found between the Ishihara and Hardy - Rand - Rittler tests (p > 0.1) or between the Waggoner Computerized and City University tests (p = 0.11). Colour vision testing maintained an accuracy ≤ 1.0 logMAR with the Ishihara and Hardy - Rand - Rittler tests, 1.1 logMAR with the Waggoner Pseudo-isochromatic and Farnsworth D-15 tests, and 0.9 logMAR with the Waggoner Computerized and City University tests.

CONCLUSIONS

Insights are provided into the visual acuity thresholds required for accurate colour vision testing, which can serve as a basis for future research and provide a reference for clinical practice in this field.

Seeing “the Dress” in the Right Light: Perceived Colors and Inferred Light Sources

In the well-known “dress” photograph, people either see the dress as blue with black stripes or as white with golden stripes. We suggest that the perception of colors is guided by the scene interpretation and the inferred positions of light sources. We tested this hypothesis in two online studies using color matching to estimate the colors observers see, while controlling for individual differences in gray point bias and color discrimination. Study 1 demonstrates that the interpretation of the dress corresponds to differences in perceived colors. Moreover, people who perceive the dress as blue-and-black are two times more likely to consider the light source as frontal, than those who see the white-and-gold dress. The inferred light sources, in turn, depend on the circadian changes in ambient light. The interpretation of the scene background as a wall or a mirror is consistent with the perceived colors as well. Study 2 shows that matching provides reliable results on differing devices and replicates the findings on scene interpretation and light sources. Additionally, we show that participants’ environmental lighting conditions are an important cue for perceiving the dress colors. The exact mechanisms of how environmental lighting and circadian changes influence the perceived colors of the dress deserve further investigation.

Evaluation of tablet computers for visual function assessment

Recent advances in technology and the increased use of tablet computers for mobile health applications such as vision testing necessitate an understanding of the behavior of the displays of such devices, to facilitate the reproduction of existing or the development of new vision assessment tests. The purpose of this study was to investigate the physical characteristics of one model of tablet computer (iPad mini Retina display) with regard to display consistency across a set of devices (15) and their potential application as clinical vision assessment tools. Once the tablet computer was switched on, it required about 13 min to reach luminance stability, while chromaticity remained constant. The luminance output of the device remained stable until a battery level of 5%. Luminance varied from center to peripheral locations of the display and with viewing angle, whereas the chromaticity did not vary. A minimal (1%) variation in luminance was observed due to temperature, and once again chromaticity remained constant. Also, these devices showed good temporal stability of luminance and chromaticity. All 15 tablet computers showed gamma functions approximating the standard gamma (2.20) and showed similar color gamut sizes, except for the blue primary, which displayed minimal variations. The physical characteristics across the 15 devices were similar and are known, thereby facilitating the use of this model of tablet computer as visual stimulus displays.

The correlation between visual acuity and color vision as an indicator of the cause of visual loss

PURPOSE

To explore the correlation between visual acuity (VA) and color vision and to establish a guide for the diagnosis of the cause of visual loss based on this correlation.

DESIGN

Retrospective comparative evaluation of a diagnostic test.

METHODS

A total of 259 patients with visual impairment caused by 1 of 4 possible disease categories were included. Patients were divided into 4 groups according to the etiology of visual loss: 1) optic neuropathies, 2) macular diseases, 3) media opacities, and 4) amblyopia. The best-corrected VA was established and a standard Ishihara 15 color plates was tested and correlated to the VA in every group separately. Correlation between the VA and the color vision along the different etiologies was evaluated. Frequency of each combination of color vision and VA in every disease category was established.

RESULTS

VA is correlated with color vision in all 4 disease categories. For the same degree of VA loss, patients with optic neuropathy are most likely and patients with amblyopia are the least expected to have a significant color vision loss. Patients with optic neuropathy had considerably worse average color vision (6.7/15) compared to patients in the other 3 disease categories: 11.1/15 (macular diseases), 13.2/15 (media opacities), and 13.4/15 (amblyopia).

CONCLUSIONS

Diseases of the optic nerve affect color vision earlier and more profoundly than other diseases. When the cause of visual loss is uncertain, the correlation between the severity of color vision and VA loss can imply the possible etiology of the visual loss.