Individual Differences in Scotopic Visual Acuity and Contrast Sensitivity: Genetic and Non-Genetic Influences

A Comprehensive Investigation of Contrast Sensitivity and Disk Halo in High Myopia Treated With SMILE and EVO Implantable Collamer Lens Implantation

Purpose

To investigate the clinical outcomes in small incision lenticule extraction (SMILE) and EVO implantable Collamer lens (ICL)–treated high myopia.

Methods

Thirty-three SMILE-treated and 32 EVO ICL-treated patients were included and followed up for 6 months. Subjective refraction, contrast sensitivity, and disk halo size were measured preoperatively and postoperatively. Patient-reported outcomes (PROs) were obtained at the final visit.

Results

Significant differences in efficacy and safety indices were observed between the SMILE and EVO ICL groups at 6 months postoperatively (P < 0.05). In the SMILE group, the mesopic contrast sensitivity at 2.2 cycles per degree (cpd) and photopic contrast sensitivity at 0.5, 3.4, and 7.1 cpd were significantly improved. In the EVO ICL group, the mesopic contrast sensitivity at 7.1 cpd and photopic contrast sensitivity at 0.5, 7.1, and 14.6 cpd were significantly improved. The halo radii after SMILE were significantly increased at 1 week, showed a decreasing trend at 1 month, returned to baseline at 3 months, and progressed stably at 6 months. However, it was unchanged in the EVO ICL group. Regarding subjective experience, haloes were the most common disturbance with mild and little bothersomeness after EVO ICL in contrast to starbursts after SMILE.

Conclusions

EVO ICL implantation yielded better visual outcomes, improved contrast sensitivity particularly at high spatial frequencies, had a stabler disk halo size, and increased incidence of haloes, with less influence than that of SMILE.

Translational Relevance

The disk halo and PRO findings will be of benefit for consultations and evaluations in visual performance and disturbances.

Lutein and Zeaxanthin Intake during Pregnancy and Visual Function in Offspring at 11–12 Years of Age

(1) Background: Lutein and zeaxanthin (L&Z) are essential dietary nutrients that are a crucial component of the human macula, contributing to visual functioning. They easily cross the placental barrier, so that retinal deposition commences during foetal development. This study aims to assess associations between maternal L&Z intake during pregnancy and offspring visual function at 11–12 years. (2) Methods: Using the Spanish INfancia y Medio Ambiente project (INMA) Sabadell birth cohort, 431 mother–child pairs were analysed. L&Z data were obtained from food frequency questionnaires (FFQ) at week 12 and 32 of pregnancy, alongside other nutritional and sociodemographic covariates. Contrast vision (CS) and visual acuity (VA) were assessed using the automated Freiburg Acuity and Contrast Testing (FRACT) battery. Low CS and VA were defined as being below the 20th cohort centile. Associations were explored using multiple logistic regression. (3) Results: After controlling for potential confounders, L&Z intake during the 1st and 3rd trimester did not reveal any statistically significant association with either CS or VA in offspring at age 11/12 years. (4) Conclusions: No evidence of a long-term association between L&Z intake during pregnancy and visual function in offspring was found. Further larger long-term studies including blood L&Z levels are required to confirm this result.

STRUCTURAL AND FUNCTIONAL CHARACTERISTICS OF LAMELLAR MACULAR HOLES

PURPOSE

Lamellar macular holes (LMHs) can been subdivided into tractional and degenerative subtypes. This cross-sectional cohort study compared structural and functional characteristics in these subtypes hypothesizing that tractional LMH has a higher prevalence of vitreopapillary adhesion and tangential traction (macular pucker), whereas degenerative LMH has more ellipsoid zone disruption and worse vision, measured three different ways.

METHODS

Tractional LMH (n = 22) and degenerative LMH (n = 15) were distinguished by optical coherence tomography criteria. Separate spectral domain optical coherence tomography scanning of the macula and optic disk was performed. Visual acuity, contrast sensitivity function (Weber Index, %W), and the degree of visual distortions (3-dimensional threshold Amsler grid; % volume lost [%VL]) were quantified.

RESULTS

Vitreopapillary adhesion was present in 14/22 (64%) tractional, but in only 3/15 (20%) degenerative LMH (P = 0.006). Macular pucker was present in 19/22 (86%) tractional, but in only 8/15 (53%) degenerative LMH (P = 0.011). Ellipsoid zone disruption was present in 13/15 (87%) degenerative, but in only 2/22 (9%) tractional LMH (P = 0.0001). Visual acuity was better in tractional than degenerative LMH (P = 0.006), as was contrast sensitivity function (tractional = 3.44 ± 1.07 %W, degenerative = 4.66 ± 1.73 %W; P = 0.015). Visual distortions were less in tractional (0.33 ± 0.61 %VL) than in degenerative (0.85 ± 0.68 %VL) LMH (P = 0.014).

CONCLUSION

Structure and visual function differ significantly in subtypes of LMH. Tractional LMH has 3-fold higher prevalence of vitreopapillary adhesion and 2-fold higher prevalence of macular pucker. Degenerative LMH has 9-fold more ellipsoid zone disruption, worse visual acuity and contrast sensitivity function, and 3-fold more distortions. Thus, outer retinal integrity seems more closely correlated with vision than anterior structural abnormalities in LMH.

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.

Vitreous and Vision Degrading Myodesopsia

Macromolecules comprise only 2% of vitreous, yet are responsible for its gel state, transparency, and physiologic function(s) within the eye. Myopia and aging alter collagen and hyaluronan association causing concurrent gel liquefaction and fibrous degeneration. The resulting vitreous opacities and collapse of the vitreous body during posterior vitreous detachment are the most common causes for the visual phenomenon of vitreous floaters. Previously considered innocuous, the vitreous opacities that cause floaters sometimes impact vision by profoundly degrading contrast sensitivity function and impairing quality-of-life. While many people adapt to vitreous floaters, clinically significant cases can be diagnosed with Vision Degrading Myodesopsia based upon echographic assessment of vitreous structure and by measuring contrast sensitivity function. Perhaps due to the ubiquity of floaters, the medical profession has to date largely ignored the plight of those with Vision Degrading Myodesopsia. Improved diagnostics will enable better disease staging and more accurate identification of severe cases that merit therapy. YAG laser treatments may occasionally be slightly effective, but vitrectomy is currently the definitive cure. Future developments will usher in more informative diagnostic approaches as well as safer and more effective therapeutic strategies. Improved laser treatments, new pharmacotherapies, and possibly non-invasive optical corrections are exciting new approaches to pursue. Ultimately, enhanced understanding of the underlying pathogenesis of Vision Degrading Myodesopsia should result in prevention, the ultimate goal of modern Medicine.

Macular Inner Retinal Layer Thickness in Relation to Photopic and Mesopic Contrast Sensitivity in Healthy Young and Older Subjects

Purpose

To examine relationships between the thicknesses of ganglion cell (GC)-related macular layers and central photopic or mesopic contrast sensitivity (CS) in healthy eyes.

Methods

Measurements were made in 38 young and 38 older healthy individuals. Total, inner, and outer retinal layer (IRL) thicknesses were measured in the macula region through spectral-domain optical coherence tomography (SD-OCT) across three subfields, or rings, centered at the fovea: central foveal, pericentral, and peripheral. Ganglion cell complex and circumpapillary retinal nerve fiber layer thicknesses were also measured. Low-spatial-frequency CS for gratings presented at the central 10° visual field were measured through computerized psychophysical tests under photopic and mesopic conditions. Relationships were examined by uni- and multivariate regression analysis.

Results

Peripheral IRL thickness emerged as the only independent predictor of photopic CS (P = 0.001) in the young group and of photopic (P = 0.026) and mesopic CS (P = 0.001) in the older group. The slopes of regression lines used to predict CS from peripheral IRL thickness were significantly different for pair-wise comparisons of both photopic CS and age group (P = 0.0001) and mesopic CS (P = 0.0001) and age group. These models explained 37% of the variability in photopic CS and 36% of the variability in mesopic CS.

Conclusions

Macular IRL thinning likely due to GC loss was related to reduced photopic and mesopic CS in older healthy eyes. In contrast, in the young eyes, a thicker macular IRL, possibly indicating transient gliosis, was associated with reduced CS.

Examining the Association Between Autistic Traits and Atypical Sensory Reactivity: A Twin Study

OBJECTIVE

Atypical responses to sensory stimuli are common features of autism spectrum disorders (ASD). Consequently, atypical sensory reactivity (SR) is now a diagnostic feature of ASD. Quantitative genetic research on ASD has overlooked these symptoms, however. We therefore investigated the association between autistic traits and SR using twin methods.

METHOD

Autistic traits and SR were assessed by 2 separate scales in 12,419 Swedish twin pairs (n = 3,586 monozygotic [MZ], n = 8,833 dizygotic [DZ]) when the twins were 9 or 12 years of age. The classic twin design estimated the degree to which etiological factors associated with autistic traits were also associated with SR, and the degree to which such shared factors explained the covariance between these phenotypes. DeFries-Fulker analysis estimated the genetic correlation between screening diagnoses of ASD, defined broadly and strictly, and SR.

RESULTS

Autistic traits and SR were both highly heritable (62%-75% and 66%-71%, respectively). There was a moderate phenotypic correlation between autistic traits and SR (r = 0.47). Genetic influences on these phenotypes correlated moderately (genetic correlation = 0.60). These overlapping genetic factors explained most of the correlation between autistic traits and SR. Genetic correlations with SR increased for broad ASD (genetic correlation = 0.72) and strict ASD (genetic correlation = 0.80).

CONCLUSION

The genetic overlap observed between autistic traits and SR lends quantitative genetic support to the notion that ASD and SR are strongly linked. Such symptoms may thus comprise part of the ASD genotype, as well as phenotype. Associations persisted across all definitions of ASD, indicating a genetic link between the broader ASD phenotype and SR.

An Assessment of the Contrast Sensitivity in Patients with Ametropic and Anisometropic Amblyopia in Achieving the Corrected Visual Acuity of 1.0

Both visual acuity (VA) and contrast sensitivity (CS) are important parameters for measuring visual function. In this research, we investigated the CS of patients with ametropic or anisometropic amblyopia, whose corrected visual acuity (CVA) recovered to 1.0. Fifty-five cases with amblyopia and 22 control cases with a normal visual acuity of 1.0 were enrolled. The CS of the patients whose ametropic amblyopia had recovered to a CVA of 1.0 at 18 cpd spatial frequency was still lower than that of the normal control group under both photopic and scotopic conditions (P = 0.001, 0.025), but there were no significant differences at low- and middle-spatial frequencies. The CS of amblyopic eyes of the patients with anisometropic amblyopia was lower than that of the normal control group at the 18 cpd spatial frequency under photopic conditions (P = 0.005), and at the 6 cpd, 12 cpd, and 18 cpd spatial frequencies under scotopic conditions (P = 0.008, <0.001, 0.004, respectively). The CS between the amblyopic eyes and the sound eyes of patients with anisometropic amblyopia presented significant differences at the 6 cpd, 12 cpd, and 18 cpd spatial frequencies under scotopic conditions (P = 0.025, 0.045, 0.019, respectively). We suggest that amblyopia treatment should involve not only the correction of VA but also the improvement of CS.

[Contrast vision-definitions, conversions, and equivalence tables]

Human contrast vision and its quantitative assessment are gaining more attention. Publications on this topic can be confusing due to the overabundance of differing definitions and quantification of contrast vision. As a case in point, in Germany, contrast ratios as required for certain driving licenses and the DIN-defined contrast ratio are reciprocal. In this article, the five most important definitions of luminance contrast and contrast vision (Michelson, Weber, contrast ratios, logCS) are presented. We detail the specific domains for them, give formulae to convert between all of them and provide a table with equivalent values. We recommend the unit logCS wherever possible.