Effects of Monocular Flicker on Binocular Imbalance in Amblyopic and Nonamblyopic Adults.

Purpose: This study aimed to evaluate the effects of monocular flicker stimulation on binocular imbalance in both amblyopic and nonamblyopic adults. Methods: Seven amblyopic patients (28.3 ± 3.3 years; four females) and seven normally sighted participants (27.3 ± 4.1 years; five females) participated in the study. We used liquid crystal spectacles to create externally-generated monocular flicker (4, 7, 10, 15, or 20 Hz) and used the metric of log balance point (logBP) to determine whether imposed flicker could change the eyes' equilibrium interocular contrast ratio. Flicker was applied to either the fellow eye vs. the amblyopic eye or dominant eye (DE) vs. non-DE (non-DE) of amblyopic and nonamblyopic participants, respectively. We defined a logBP of 0 to indicate complete binocular balance and an increase in logBP relative to baseline to indicate a relative strengthening of the non-DE or amblyopic eye. Results: Monocular flicker applied to the DE or fellow eye increased logBP, whereas when applied to the non-DE or amblyopic eye, reduced the logBP. These effects were more pronounced at low temporal frequencies than that at high temporal frequencies. The interaction between eye and temporal frequency was significant in both normals, F(4, 24) = 58.082, P < 0.001, η2 = 0.906, and amblyopes, F(1.923, 11.538) = 60.555, P < 0.001, η2 = 0.91. Conclusions: Monocular flicker diminishes the contribution of the flickered eye in binocular combination, resulting in a relative dominance of the nonflickered eye in interocular interactions. Furthermore, a more pronounced temporally modulated effect was observed at lower temporal frequencies.

An Isolated and Deeply Divergent Hynobius Species from Fujian, China.

It is important to describe lineages before they go extinct, as we can only protect what we know. This is especially important in the case of microendemic species likely to be relict populations, such as Hynobius salamanders in southern China. Here, we unexpectedly sampled Hynobius individuals in Fujian province, China, and then worked on determining their taxonomic status. We describe Hynobius bambusicolus sp. nov. based on molecular and morphological data. The lineage is deeply divergent and clusters with the other southern Chinese Hynobius species based on the concatenated mtDNA gene fragments (>1500 bp), being the sister group to H. amjiensis based on the COI gene fragment, despite their geographic distance. In terms of morphology, the species can be identified through discrete characters enabling identification in the field by eye, an unusual convenience in Hynobius species. In addition, we noted some interesting life history traits in the species, such as vocalization and cannibalism. The species is likely to be incredibly rare, over a massively restricted distribution, fitting the definition of Critically Endangered following several lines of criteria and categories of the IUCN Red List of Threatened Species.

Rapid Alternate Flicker Modulates Binocular Interaction in Adults With Abnormal Binocular Vision.

Purpose: The current understanding of binocular processing is primarily derived from static spatial visual perception: this leaves the role of temporal information unclear. In this study, we addressed this gap by testing the effect of alternating flicker on binocular information processing in adults with abnormal binocular vision. Our goal was to determine which temporal frequency optimally balanced input from both eyes. Methods: We took measurements in four groups of human adults: 10 normal adults with the individual's nondominant eye covered by a 2% neutral density filter (aged 25.60 ± 1.43 years, experiment 1), 9 nonamblyopic anisometropes (aged 24.33 ± 1.66 years, experiment 2), 7 amblyopes (aged 26.5 ± 1.64 years, experiment 3), and 7 treated amblyopes (aged 24 ± 3.21 years, experiment 4). The balance point (BP), where participants' two eyes are equally effective, was measured using a binocular orientation combination task at four spatial frequencies (SFs; 0.5-4 c/d) and five temporal frequencies (TFs; baseline and 4, 7, 10, and 15 Hz). Its log transformation |logBP| was taken into further analysis. Results: We observed clear U-shaped temporal tuning of the |logBP| for the entire range of TFs (that we measured: trough occurred at 7 Hz). This pattern occurred and was significant in all four groups (P < 0.001). In addition, the effect of SFs on |logBP| was significant in normal, amblyopic, and treated amblyopic groups (all P < 0.001) and was marginally significant in the nonamblyopic anisometropic group (P = 0.086). Conclusions: Alternating flicker around 7 Hz may be the optimal temporal frequency for balancing eyes in human adults with binocular imbalance.

The Efficacy of Defocus Incorporated Multiple Segments Lenses in Slowing Myopia Progression: Results from Diverse Clinical Circumstances.

PURPOSE: Defocus incorporated multiple segments (DIMS) spectacle lenses were reported to slow myopia progression significantly in a randomized controlled trial (RCT). The study evaluated their effectiveness in clinical settings. DESIGN: Retrospective study. PARTICIPANTS: Patient records involving use of DIMS and single-vision (SV) spectacle lenses were collected from subsidiary hospitals of Aier Eye Hospital Group. METHODS: The spherical equivalent (SE), determined by subjective refraction, was adopted to assess the myopia progression. The strategy of propensity score matching (PSM) was applied to match the confounding baseline characteristics between the 2 groups. The effectiveness was calculated based on the difference of myopia progression of these 2 approaches. MAIN OUTCOME MEASURES: Change in SE. RESULTS: Three thousand six hundred thirty-nine patients with DIMS and 6838 patients with SV spectacles were included. The age of the patients was 6 to 16 years (mean ± standard deviation: 11.02 ± 2.53 years). The baseline SE was between 0.00 and -10.00 diopters (D) (mean ± standard deviation: -2.78 ± 1.74 D). After the PSM, data on 2240 pairs with 1-year follow-up and on 735 pairs with 2-year follow-up were obtained. Significantly slower progression was seen in the DIMS group at both the 1-year (DIMS, -0.50 ± 0.43 D; SV, -0.77 ± 0.58 D; P < 0.001) and 2-year (DIMS, -0.88 ± 0.62 D; SV, -1.23 ± 0.76 D; P < 0.001) subdataset. In the 1-year subdataset, 40% and 19% showed myopia progression of no more than 0.25 D for the DIMS and SV groups, respectively (chi-square, 223.43; P < 0.001), whereas 9% and 22% showed myopia progression of more than 1.00 D for the DIMS and SV groups, respectively (chi-square, 163.38; P < 0.001). In the 2-year subdataset, 33% and 20% showed myopia progression of no more than 0.50 D for the DIMS and SV groups, respectively (chi-square, 31.15; P < 0.001), whereas 12% and 29% showed myopia progression of more than 1.50 D for the DIMS and SV groups (chi-square, 65.60; P < 0.001). CONCLUSIONS: Although the magnitude was lower than that reported in the previous RCT, this large-scale study with diversity of the data sources confirmed the effectiveness of DIMS spectacles to slow myopia progression in clinical practice. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Two-Dimensional Peripheral Refraction and Image Quality for Four Types of Refractive Surgeries.

PURPOSE: To provide a comprehensive investigation of the optical quality across the visual field for current mainstream types of refractive surgeries. METHODS: Sixty eyes from 60 adults who received refractive surgery of either femtosecond laser-assisted laser in situ keratomileusis (FS-LASIK), Q-value guided customized laser in situ keratomileusis (Q-LASIK), small incision lenticule extraction (SMILE), or Implantable Collamer Lens (ICL) (STAAR Surgical) implantation were included in this study. Refraction and optical aberrations from a visual field of horizontal 60° (from temporal 30° to nasal 30°) and vertical 36° (from superior 20° to inferior 16°) were measured using a custom-made Hartmann-Shack wavefront peripheral sensor. Refractive error, higher order aberrations, point spread function (PSF), and Strehl ratio were compared among these groups prior to and after the surgical procedures, respectively. RESULTS: All types of surgical procedures achieved an almost plano refraction in the central retina. This was also the case in the peripheral retina for the three types of laser refractive surgeries. However, residual peripheral relative hyperopic defocus was observed after ICL implantation. In all groups prior to the surgery, PSFs showed increasing distortion with eccentricity and arrow-like shape pointing toward the central fovea in the periphery in diagonals. Degradation of the PSFs was diminished by all three types of laser refractive surgeries, whereas ICL implantation made the peripheral distortion more prominent. CONCLUSIONS: Although ICL implantation produced a similar impact on refractive correction and objective optical quality in the central vision compared with other laser refractive surgeries, its outcome on the peripheral optics is different. The impact of this difference on visual performance deserves notice and warrants further investigation. [J Refract Surg. 2023;39(1):40-47.].

Two-Dimensional, High-Resolution Peripheral Refraction in Adults with Isomyopia and Anisomyopia.

Purpose: The purpose of this study was to investigate the two-dimensional peripheral refraction in fellow eyes of patients with isomyopia and anisomyopia. Methods: Sixty-eight young adults were recruited, including 25 isomyopes with interocular differences (IODs) of foveal refraction < 1.00 D and 43 anisomyopes with IOD > 1.50 D. Peripheral refraction across an area of the visual field of 60° × 36° with a resolution of 1° was measured using a custom-made Hartmann-Shack wavefront sensor. The retinal area was divided into 3 × 3 zones for comparison between the fellow eyes. Results: There was no difference of refraction in all corresponding zones between the fellow eyes in the isomyopic group (all P > 0.05). The IODs between more myopic (MM) eyes and less myopic (LM) eyes in the anisomyopic group ranged from -1.40 to approximately -2.46 D (all P <0.001), which was flagged in the center and attenuated in peripheral zones by varied magnitudes. In the stratification analysis for different levels of anisomyopia, the nasal retina first presented significant relative hyperopic shifts compared to the center, followed by the temporal retina. In contrast, the superior and inferior periphery only differed from the center when the central IOD was greater than 3.00 D. Conclusions: The two-dimensional peripheral refraction patterns showed a mirror symmetry between the fellow eyes of a patient with isomyopia. However, in the anisomyopic group, peripheral refraction showed significantly relative hyperopic shift when compared with the center and developed with a varied rate in different areas. These findings may indicate an asymmetrical variation in the peripheral refraction patterns during myopia progression.

The Adaptation and Acceptance of Defocus Incorporated Multiple Segment Lens for Chinese Children.

PURPOSE: We investigated the adaptability and acceptance of a novel spectacle lens design that was recently reported to achieve a significant antimyopia effect. DESIGN: A prospective, cross-over study. METHODS: Twenty children were recruited to wear both Defocus Incorporated Multiple Segments (DIMS) and single vision (SV) lens, with a random assignment of which type of lens was experienced first. For each type of lens, high and low contrast central distant visual acuity (VA) and high contrast mid-peripheral near VA were measured at both 500 lux and 50 lux ambient illuminance after 30 minutes' and a week's wearing of the lens. A self-developed questionnaire was applied to evaluate the visual discomfort at the 1-week visit. All quantitative data were analyzed by paired t test, while qualitative data were analyzed with the χ2 or Wilcoxon signed-rank tests. RESULTS: Central VA was not affected by DIMS lens compared with SV lens in all circumstances (all P > .05). However, the mid-peripheral near VA was found to reduce by approximately 0.06 logarithm of minimal angle of resolution unit in 2 of 4 quadrants (500 lux; P < .05) and in 3 quadrants (50 lux; P < .05) for DIMS lenses. No improvement was detected in the 1-week visit. Mid-peripheral blurred vision was the main visual complaint, which was noticed only once or twice a day. Being aware of the average antimyopic efficacy, 90% of children subjects preferred DIMS lenses. CONCLUSION: Mid-peripheral vision through DIMS lenses was slightly affected compared with SV lenses. Otherwise, DIMS lenses received good tolerance and acceptance by Chinese children.

An Objective Comparison of Light Intensity and Near-Visual Tasks Between Rural and Urban School Children in China by a Wearable Device Clouclip.

PURPOSE: To compare light intensity and near-visual tasks objectively between rural and urban children. METHODS: Clouclip, a wearable device, was applied to assess metrics of these two factors in 78 fifth-grade students from an urban and from a rural school. RESULTS: The light intensity experienced by urban students was found significantly lower both in the school period (614.05 ± 178.77 vs. 918.41 ± 257.81 lux, P < 0.001) and on the weekend (444.53 ± 216.65 vs. 882.21 ± 536.67 lux, P < 0.001). The duration of exposure to bright light (>1000 lux) was also substantially shorter for urban students. Although no significant difference was found in near work-related behaviors during the school period and the weekend, for the after-school period the urban students had a shorter average viewing distance (30.94 ± 4.14 vs. 34.81 ± 3.93 cm, P < 0.001), a longer accumulated duration of near work (2.25 ± 0.53 vs. 1.95 ± 0.46 hours, P = 0.010), a greater time ratio of near work (56% ± 14% vs. 49% ± 14%, P = 0.045), and a greater time ratio of excessively close near work (49% ± 13% vs. 40% ± 12%, P = 0.001). CONCLUSIONS: Our data indicate there were substantial differences in light exposure and near-work metrics between the two regions. The correlation between these differences and the discrepancy in regional myopia prevalence needs further investigation. TRANSLATIONAL RELEVANCE: The objective quantification of these metrics might help explain the varied myopia prevalence among regions.