A reassessment and comparison of the Landolt C and tumbling E charts in managing amblyopia

Current criteria for amblyopia do not account for difference in visual acuity charts. This prospective observational study analyzed 100 children younger than 10 years treated at a tertiary referral center. Visual acuity was separately tested in each eye using Landolt C and tumbling E charts in a random order. For each chart, receiver operating characteristic curve analysis was performed to determine the best cutoff for visual acuity score. Main outcome measures included the difference in visual acuity scores between the two charts, the feasibility of repeated testing of visual acuity in each eye, and amblyopia cutoff values for each chart. Mean logMAR visual acuity scores obtained by tumbling E chart were significantly better than those obtained by Landolt C chart. For amblyopia, the best cutoff values were < + 0.14 (20/27 Snellen equivalent) for tumbling E chart and < + 0.24 (20/35 Snellen equivalent) for Landolt C chart. For children under 10 years old, visual acuity scores for tumbling E chart were significantly better than those for Landolt C chart. We suggest that amblyopia management in children should account for age and the type of visual acuity chart used.

Eye-Tracker Analysis of the Contrast Sensitivity of Anomalous and Normal Trichromats: A Loglinear Examination with Landolt-C Figures

The contrast sensitivity of normal and anomalous trichromats were examined with Landolt-C figures by eye-tracking system. For the measurements, two series of test images (achromatic and colored) were designed. The difficulty levels of the tests were gradually increased after each right answer. In the case of the observation of the ring of the Landolt-C figures, the variables related to fixation duration, fixation count, visit duration and count significantly affected this subject, success or image parameters, and their interactions. The main questions of this study were as follows: Which statistical method is suitable to model the differences between anomalous and normal trichromats? Which eye-movement variables have a significant effect on the investigated parameters and on their interactions? Is there any significant difference between eye-movement variables of normal and anomalous trichromats? How does the survival time of anomalous and normal trichromats change in the case of achromatic and colored figures? The results showed that the right answers of anomalous and normal trichromats can be described with multiple or cross-classified contingency tables evaluated effectively by loglinear regression. The survival analysis showed that normal trichromats are more successful in interpreting colored images, while anomalous trichromats seemed to be more efficient in perceiving achromatic images.

On the joint effect of spatial attention and defocus blur on acuity: attentional limit to the resolving power of the eye

Defocus blur and spatial attention both act on our ability to see clearly over time. However, it is currently unknown how these two factors interact because studies on acuity resolution only focused on the separate effects of attention and defocus blurs. In this study, resolution acuity was measured along the diagonal 135°/315° with horizontal, at 8° eccentricity for clear and blur Landolt C images under various manipulations of covert endogenous attention. We observe that attention not just improves the resolution of clear stimuli, but also modulates the resolution of defocused stimuli for compensating the loss of resolution caused by retinal blur. Our results show, however, that as the degree of attention decreases, the differences between clear and blurred images largely diminish, thus limiting the benefit of an image quality enhancement. It also appeared that attention tends to enhance the resolution of clear images more than blurred targets, suggesting potential variations in the gain of vision correction with the level of attention. This demonstrates that the interaction between spatial attention and focus plays a role in the way we see things. In view of these findings, the development of adaptive (neuro-optical) interventions, which adjust the eye’s focus to attention, may hold promise.Significance statementVisual technologies are now attaining a degree of extreme sophistication and diversity, which allows more comprehensive, but often complex manipulations of the optical image formed onto the back of the eye. It is therefore an enigma how those fine and immersive manipulations of the sensory environment are integrated in the brain. In this study, we show that the resolving power of the eye can depend complexly on the interaction between spatial attention and focus. This discovery suggests that perception might be advantageously guided by technologies tailoring optical focus to individual attentional patterns.

The “speed” of acuity in scotopic vs. photopic vision

Purpose The effect of duration of optotype presentation on visual acuity measures has been extensively studied under photopic conditions. However, systematic data on duration dependence of acuity values under mesopic and scotopic conditions is scarce, despite being highly relevant for many visual tasks including night driving, and for clinical diagnostic applications. The present study aims to address this void. Methods We measured Landolt C acuity under photopic (90 cd/m2), mesopic (0.7 cd/m2), and scotopic (0.009 cd/m2) conditions for several optotype presentation durations ranging from 0.1 to 10 s using the Freiburg Acuity and Contrast Test. Two age groups were tested (young, 18–29 years, and older, 61–74 years). Results As expected, under all luminance conditions, better acuity values were found for longer presentation durations. Photopic acuity in young participants decreased by about 0.25 log units from 0.1 to 10 s; mesopic vision mimicked the photopic visual behavior. Scotopic acuities depended more strongly on presentation duration (difference > 0.78 log units) than photopic values. There was no consistent pattern of correlation between luminance conditions across participants. We found a qualitative similarity between younger and older participants, despite higher variability among the latter and differences in absolute acuity: Photopic acuity difference (0.1 vs. 10 s) for the older participants was 0.19 log units, and scotopic difference was > 0.62 log units. Conclusion Scotopic acuity is more susceptible to changes in stimulus duration than photopic vision, with considerable interindividual variability. The latter may reflect differences in aging and sub-clinical pathophysiological processes and might have consequences for visual performance during nocturnal activities such as driving at night. Acuity testing with briefly presented scotopic stimuli might increase the usefulness of acuity assessment for tracking of the health state of the visual system.

STUDY ON CLINICAL PROFILE OF PATIENTS WITH AMBLYOPIA: A HOSPITAL BASED PROSPECTIVE STUDY.

Objectives: This present study was to evaluate the clinical profile of patients with amblyopia. Methods: A detail history, clinical examinations and relevant investigations were performed to all cases of amblyopia. Cycloplegic refraction under atropine sulphate 1 % eye ointment for 5-10 years and eye drop homatropine 2 % for 11-20 years age group was performed. Management material was tissue paper and micropore tape for patching. It was done in the form of 3 hours or 6 hours patching. Visual improvement tested every month upto 3 months and then after 3 months by Snellen’s distant visual acuity or Landolt C chart. Results: Data was analyzed by using simple statistics methods with the help of MS-Office software. Conclusions: Amblyopia was commonly seen in children. Anisometropic amblyopia was very common. Refractive error was commonly seen in cases with hypermetropia with astigmatism, myopia with astigmatism and hypermetropia. Majorities of these cases had 2-4D and 4.25-6D refractive error differences and had 6/24-6/12 visual acuity.Alternate divergent and unilateral partially accommodative convergent were the most common type of squint seen. Majorities of cases with anisometropic amblyopia had seen >2 snellen’s line improvement of visual acuity in 3 hours patching regimens. Hence, early intervention is ideal, with appropriate management and treatment amblyopia patients are likely obtain a successful outcome, and possibly full resolution. Key words: Children, amblyopia, refractive error, visual acuity

Greater effect of contrast polarities on visual acuity measurements using chart with shorter wavelength background

Our study aimed to explore the effect of positive and negative polarities on visual acuity measurements by utilizing black and white as a text against background with three distinct colours. Visual acuity was recorded as logarithm of minimum angle of resolution (LogMAR) using the detection of the gap in a four-position Landolt-C. The 2x3 (polarity x background color) two way repeated measures ANOVA showed a statistically significant interaction between polarity and colour background on visual resolution [F (2, 16) = 23.704, p < 0.001, η2 = 0.744]. Among the three primary background colour, shorter-wavelength (blue background) showed statistically significant findings between both positive and negative polarity [F (1, 9) = 39.875, p < 0.001, η2 = 0.818]. Visual acuity measurements improved with negative polarity but decreased with positive polarity with blue colour background. However, visual acuity was not statistically significantly different with the green (medium-wavelength) [F (1, 11) = 0.625, p = 0.446, η2 = 0.053] and the red (long-wavelength) backgrounds [F (1, 9) = 4.021, p = 0.856, η2 = 0.000]. In conclusion, black text against shorter-wavelength (blue) background apparently more difficult to be resolved by human eyes compared with white text. These findings suggest colour element might be an advantage for negative polarity colour combinations.

Macular Thickness, Foveal Volume, and Choroidal Thickness in Amblyopic Eyes and Their Relationships to the Treatment Outcome

Purpose. To assess the correlations between the retinal/choroidal structure and the treatment outcomes of amblyopic children.Methods. This study enrolled eyes with amblyopia resulting from strabismus, anisometropia, or ametropia. All patients underwent detailed eye examinations, including spectral domain optical coherence tomography (SD-OCT) scan. All of the subjects received amblyopic treatment and were divided into 2 groups after 6 months of follow-up: the recovered amblyopic group with a best-corrected visual acuity (BCVA) ≥0.8 and the persistent amblyopic group with a BCVA <0.8 on the Landolt C chart.Results. Forty-four amblyopic children were included, of which 26 were in the recovered amblyopic group after 6 months of follow-up. The patients with strabismic anisometropic amblyopia and severe amblyopia (initial VA ≤ 0.3) were significantly predisposed to developing persistent amblyopia (P=0.049andP<0.001, respectively). After correcting with Littmann’s formula, the thickness and volume of the parafoveal and perifoveal retinal regions in the persistent amblyopia group did not show significant differences with the recovered amblyopia group.Conclusions. The initial severity of amblyopia and the type of amblyopia were the risk factors related to the poor outcome of amblyopic treatment. The foveal thickness, foveal volume, and choroidal thickness were not associated with the treatment outcome.

Contrast Ratios, Colour Elements, and Polarities in Visual Acuity Measurements

This study was aimed to investigate the effects of contrast ratios, colour elements, and polarities on visual acuity measurements. The visual acuities of 18 subjects were measured using 6 different modifications of the Landolt C chart in a 4-metre LogMAR design: (M1) black-on-white [contrast ratio: 0.8]; (M2) white-on-black [contrast ratio: 0.8]; (M3) black-on-white [contrast ratio: 0.5]; (M4) yellow-on-green [contrast ratio: 0.8]; (M5) yellow-on-green [contrast ratio: 0.5]; and (M6) black-on-yellow [contrast ratio: 0.8]. Comparative analysis was performed to examine the effects of the three aforementioned parameters on visual acuity measurements. The visual acuities were found to be significantly different between the contrast ratios of 0.5 and 0.8, regardless of whether colour elements were present (black-on-white) or otherwise (yellow-on-green) [Friedman test: c2 (3) = 24.24, p < 0.05]. Interestingly, the LogMAR score was found to be significantly different between the yellow-on-green and black-on-yellow chart designs when the contrast ratio remained constant at 0.8 [Wilcoxon signed-rank test: z = 2.950, p < 0.05]. However, the effect of contrast polarity (positive/ negative) on visual acuity was not significant when the contrast ratio was fixed at 0.8 [Wilcoxon signed-rank test: z = 0.318, p > 0.05]. A lower contrast ratio and mid-range wavelength colour reduced visual acuity. The effect of contrast polarity without colour elements on visual acuity was negligible.