Vision Research最新文献

Blue haze (BH) is a significant factor that limits visual range outdoors by reducing the contrast of distant objects. This study evaluated how varying the intensity of veiling light, filtered to approximate the blue haze spectrum, affected visual performance in participants wearing either clear or high energy visible (HEV)-filtering contact lenses. A total of 121 participants (mean age 33.8 ± 13.6 years) were tested using a stratified, controlled, prospective, double-masked, randomized, bilateral crossover design. Participants completed two visits, each time wearing either HEV-filtering or clear lenses on both eyes, with lens type counterbalanced across visits. Three lens designs were evaluated: spherical (n = 41), multifocal (n = 40), and toric (n = 40). Visual performance was measured with a custom optical apparatus that measured peak contrast sensitivity with an ancillary xenon light channel filtered to mimic blue haze. The intensity of veiling light required to obscure a grating target served as the primary outcome, expressed as log relative energy (LRE). Across all lens types, participants could tolerate significantly more veiling light when wearing HEV-filtering lenses compared to clear controls. LRE differences were 0.22 for spherical, 0.16 for multifocal, and 0.21 for toric lenses, corresponding to performance improvements of 6.9%, 5.3%, and 6.6%, respectively. These findings suggest that incorporating HEV-filtering technology into soft contact lenses can meaningfully enhance visual performance under conditions of atmospheric blue haze, with improvements aligning with the optical density of the HEV filter (∼0.22).

Adaptation to faces produces large aftereffects in the appearance of subsequently viewed faces, yet the functional consequences of these aftereffects remain unclear. We investigated the effects of face adaptation on performance in face search and discrimination tasks. Participants searched for faces manipulated by varying the level of morphing between averaged White and Asian faces, and had to respond to a unique target face (morph level) among 5 distractor faces shown simultaneously. Before adaptation, reaction times averaged 4 or more seconds, implying that the stimuli were difficult to distinguish and that a serial search was required to scan each face in turn. Adaptation markedly reduced the search times (by roughly 2 s), with similar improvements after brief (12 s) or prolonged (20 min) adaptation periods, and with little effect on search accuracy. Separate measurements showed that the adaptation also produced large changes in facial appearance (as assessed by the perceived ethnicity category boundary), but did not affect thresholds for discriminating the face differences. These findings provide further evidence for the notion that adaptation heightens the salience of novel stimuli by renormalizing perception for the adapting stimuli.

Amblyopia is a developmental visual disorder characterized by reduced vision in one eye and has traditionally been considered a cortical condition, with no involvement of retinal structures or functions. However, recent evidence suggests that retinal vasculature may be affected in individuals with amblyopia. In this study, we investigated whether there are differences in richness and density of retinal blood vessels between individuals with amblyopia and normal controls. We used the Spatial Attention-UNet network to segment retinal blood vessels from OCT fundus images obtained from both amblyopic and fellow eyes of 23 adults with amblyopia (12 anisometropic; 11 strabismic) and the right eye of 40 control participants. We then used four features to quantify the segmented retinal vasculature: vascular area (number of pixels within segmented vessels), fractal dimension (a measurement of vascular network density distribution pattern), vascular skeleton length (pixel count of the skeletonized vessel tree), and number of vascular bifurcation points (branching complexity of the vessel skeleton). For our sample of amblyopic participants, we found no statistically significant differences between amblyopic and fellow eyes, or between anisometropic and strabismic groups, for the four vasculature features. Compared with normal control eyes, vascular area, fractal dimension and vascular skeleton length were all lower in both amblyopic and fellow eyes of amblyopic participants. These results indicate alterations in retinal vasculature in eyes (both amblyopic and fellow eyes) of individuals with amblyopia, suggesting that further research is warranted to investigate retinal vasculature as a potential biomarker for detecting and managing amblyopia.

Recent advancements in the treatment of amblyopia have adapted visual media (video games and movies) into dichoptic tasks to promote binocular function. This study demonstrates the feasibility of a treatment based on another important daily task: reading. We propose that dichoptic e-book applications may serve as an alternative treatment for binocular vision in amblyopia. We developed a prototype of a dichoptic e-book reading application (D.E.B.R.A), that was installed on Android tablets used for participant assessments. Participants read e-books in anaglyph red/green/black presentation, which allowed for monocular and binocular contrast to be adjusted independently. Amblyopic and control participants were then tested on their reading speed and questioned about their comfort using the application. We found that participants were able to read in the dichoptic presentation, albeit slower than when the books were presented in the typical "binocular" form. This suggests that the visual system can integrate information from both eyes to support reading. For some amblyopic participants, reducing the contrast of text seen by the fellow eye increased their reading speed in accordance with current research on balancing the contrast of the two eyes to unlock binocularity. At the end of each session, participants provided feedback on their comfort using the application. Overall, this study demonstrated that amblyopes can read with both eyes when text is presented in a dichoptic format. Thus, our findings suggests that the dichoptic e-book reading application could provide an effective framework for an amblyopia treatment protocol.

Short-term axial eye length changes in response to imposed positive and negative defocus were compared in hyperopic, emmetropic and myopic young adults to learn about possible differences in emmetropization. Thirty-seven subjects (average age: 28 ± 4 years) participated: emmetropes (n = 15), myopes (n = 15), and hyperopes (n = 7). They viewed a 30-minute movie on a large TV screen (65″) at 2-meter distance (equivalent to -0.5D) with optical corrections, while a + 3.5 D (myopic defocus) or -3.5 D (hyperopic defocus) lens was added in the right eye. A subset of myopes (n = 14) was also tested with -2 D lenses. Axial length was measured in both eyes before and after viewing using the Haag-Streit Lenstar LS 900. With + 3.5 D myopic defocus, emmetropes (-9.7 ± 13.1 µm) and hyperopes (-8.9 ± 5.6 µm) exhibited significant axial shortening, while myopes (-1.1 ± 10.2 µm) did not. Hyperopes and myopes differed significantly, but emmetropes and hyperopes did not. With -3.5 D hyperopic defocus, both emmetropic (+5.0 ± 7.5 µm) and hyperopic eyes (+6.6 ± 6.9 µm) elongated, indicating that their retina distinguished positive from negative defocus. Myopic eyes displayed paradoxical axial eye shortening (-7.1 ± 8.6 µm). Hyperopes and myopes differed significantly, but emmetropes and hyperopes did not. Reducing the lens power to -2 D abolished the shortening in myopes. Group data indicate bidirectional, sign-of-defocus-dependent axial length changes occur in both emmetropic and hyperopic eyes, indicating similar retinal function. Myopes showed reduced or even reversed responses, showing a functional deficiency in the myopic retina.