Refractive error is associated with intracranial volume

The impact of error of refraction and retinal nerve fiber layer thickness on cognitive functions in adults with bilateral myopia

OBJECTIVE

Myopia is considered one of the main causes of visual impairment with increased prevalence. The main objective of this study was to evaluate and characterize cognitive impairment in adult patients with bilateral myopia, in relation to retinal nerve fiber layer (RNFL) thickness.

METHODS

Forty patients with bilateral myopia aged 18-40 years, and 40 age- and gender-matched healthy controls were included in the study. For all subjects, cognitive functions were assessed by Paced Auditory Serial Addition Test (PASAT) and Paired Associate Learning test (PALT). Optical coherence tomography (OCT) was done for all included patients and controls.

RESULTS

Among the myopic group, 15 patients had mild myopia, 8 patients had moderate myopia and 17 patients had high myopia. There were significant differences between patients and control groups in terms of cognitive performance and RNFL thickness. There was a significant correlation between the scores of cognitive tests and error of refraction and RNFL thickness.

CONCLUSION

Adults with bilateral myopia have cognitive impairment, regarding information processing speed and episodic memory. Cognitive impairment is associated with retinal thinning and a higher degree of myopia.

Meridional Attentional Asymmetries in Astigmatic Eyes

Purpose

To investigate the impact of attention orientation in young myopic adults with astigmatism.

Methods

The effect of attention on foveal meridional performance and anisotropy was measured in corrected myopes with various levels of astigmatism (with-the-rule astigmatism ≤ -0.75D, Axis: 180 ± 20) using orientation-based attention. Attention was manipulated by instructing subjects to attend to either the horizontal or the vertical line of a central pre-stimulus (a pulsed cross) along separate blocks of trials. For each attention condition, meridional acuity and reaction times were measured via an annulus Gabor target situated remotely from the cross and presented at random horizontally and vertically in a two-alternative forced-choice employing two interleaved staircase procedures (one-up/one-down). Attention modulations were estimated by the difference in performance between horizontal and vertical attention.

Results

Foveal meridional performance and anisotropy were strongly affected by the orientation of attention, which appeared critical for the enhancement of reaction times and resolution. Under congruent orienting of attention, foveal meridional anisotropy was correlated with the amount of defocus for both reaction time and resolution, demonstrating greater vertical performance than horizontal performance as myopia increased. Compatible with an attentional compensation of blur through optimal orienting of attention, vertical attention enhanced reaction times compared to horizontal attention and was accompanied by an increase in overall acuity when myopia increased. Increased astigmatism was associated with smaller attention effects and asymmetry, suggesting potential deficits in the compensation of blur in astigmatic eyes.

Conclusion

Collectively, attention to orientation plays a significant role in horizontal-vertical foveal meridional anisotropy and can modulate the asymmetry of foveal perception imposed by the optics of the eye in episodes of uncorrected vision. Further work is necessary to understand how attention and refractive errors interact during visual development. These results may have practical implications for methods to enhance vision with attention training in myopic astigmats.

Altered whole-brain gray matter volume in form-deprivation myopia rats based on voxel-based morphometry: A pilot study

Background

Myopia is one of the major public health problems worldwide. However, the exact pathogenesis of myopia remains unclear. This study proposes using voxel-based morphometry (VBM) to investigate potential morphological alterations in gray matter volume (GMV) in form-deprivation myopia (FDM) rats.

Methods

A total of 14 rats with FDM (FDM group) and 15 normal controls (NC group) underwent high-resolution magnetic resonance imaging (MRI). Original T2 brain images were analyzed using VBM method to identify group differences in GMV. Following MRI examination, all rats were perfused with formalin, and immunohistochemical analysis of NeuN and c-fos levels was performed on the visual cortex.

Results

In the FDM group, compared to the NC group, significantly decreased GMVs were found in the left primary visual cortex, left secondary visual cortex, right subiculum, right cornu ammonis, right entorhinal cortex and bilateral molecular layer of the cerebellum. Additionally, significantly increased GMVs were found in the right dentate gyrus, parasubiculum, and olfactory bulb.

Conclusions

Our study revealed a positive correlation between mGMV and the expression of c-fos and NeuN in the visual cortex, suggesting a molecular relationship between cortical activity and macroscopic measurement of visual cortex structural plasticity. These findings may help elucidate the potential neural pathogenesis of FDM and its relationship to changes in specific brain regions.

Of differing methods, disputed estimates and discordant interpretations: the meta-analytical multiverse of brain volume and IQ associations

Brain size and IQ are positively correlated. However, multiple meta-analyses have led to considerable differences in summary effect estimations, thus failing to provide a plausible effect estimate. Here we aim at resolving this issue by providing the largest meta-analysis and systematic review so far of the brain volume and IQ association (86 studies; 454 effect sizes from k = 194 independent samples; N = 26 000+) in three cognitive ability domains (full-scale, verbal, performance IQ). By means of competing meta-analytical approaches as well as combinatorial and specification curve analyses, we show that most reasonable estimates for the brain size and IQ link yield r-values in the mid-0.20s, with the most extreme specifications yielding rs of 0.10 and 0.37. Summary effects appeared to be somewhat inflated due to selective reporting, and cross-temporally decreasing effect sizes indicated a confounding decline effect, with three quarters of the summary effect estimations according to any reasonable specification not exceeding r = 0.26, thus contrasting effect sizes were observed in some prior related, but individual, meta-analytical specifications. Brain size and IQ associations yielded r = 0.24, with the strongest effects observed for more g-loaded tests and in healthy samples that generalize across participant sex and age bands.

Applicability of the Smart Vision Screening Instrument among Chinese Primary School Students

Background:

A smart vision screening instrument was applied for screening low eyesight in primary school students in Wuhan, China. We aimed to compare the differences in test results between this instrument and lamp-box visual acuity charts, assess the validity of the screening results, and perform a preliminary comparison of the cost inputs of the two approaches.

Methods:

In this cross-sectional study conducted in Wuhan, China in 2017, vision tests were performed on the same day among enrolled primary school students by using the two approaches. The t-test and kappa test were performed to compare the differences, and the indicators of validity were calculated and receiver operating characteristic (ROC) curves were drawn. Existing cost-input data were collected and the budget was analyzed.

Results:

In total, 1001 schoolchildren were included, and the prevalence of low eyesight was 21.18% (95% CI: 18.71–23.87%). The test results of the two approaches were not statistically different (t=1.929, P>0.05) and showed moderate consistency (kappa=0.519, P<0.001). Sensitivity and specificity of the instrument were 84.90% (95% CI: 79.21–89.30%) and 91.63% (95% CI: 89.42–91.64%), respectively; positive predictive value was 73.17% (95% CI: 67.10–78.51%); and negative predictive value was 95.76% (95% CI: 94.00–97.04%). Area under the ROC curve was 0.883 (95% CI: 0.853–0.913) and significantly differed from 0.5 (P<0.001). The budget when using the instrument decreased 48.07% compared to that when using lamp-box visual acuity charts.

Conclusion:

The test result of the instrument is reliable, and using it to conduct screening is cost-saving. Therefore, it might be popularized for vision monitoring in schoolchildren.

Naturally-occurring myopia and loss of cone function in a sheep model of achromatopsia

Achromatopsia is an inherited retinal disease characterized by loss of cone photoreceptor function. Day blind CNGA3 mutant Improved Awassi sheep provide a large animal model for achromatopsia. This study measured refractive error and axial length parameters of the eye in this model and evaluated chromatic pupillary light reflex (cPLR) testing as a potential screening test for loss of cone function. Twenty-one CNGA3 mutant, Improved Awassi, 12 control Afec-Assaf and 12 control breed-matched wild-type (WT) Awassi sheep were examined using streak retinoscopy and B-mode ocular ultrasonography. Four CNGA3 mutant and four Afec-Assaf control sheep underwent cPLR testing. Statistical tests showed that day-blind sheep are significantly more myopic than both Afec-Assaf and WT Awassi controls. Day-blind sheep had significantly longer vitreous axial length compared to WT Awassi (1.43 ± 0.13 and 1.23 ± 0.06 cm, respectively, p < 0.0002) and no response to bright red light compared to both controls. Lack of response to bright red light is consistent with cone dysfunction, demonstrating that cPLR can be used to diagnose day blindness in sheep. Day-blind sheep were found to exhibit myopia and increased vitreous chamber depth, providing a naturally occurring large animal model of myopia.