Impact of Neurolens Use on the Quality of Life in Individuals With Headaches: A Randomized Double-Masked, Cross-Over Clinical Trial.

Purpose: Vision-related disorders, such as refractive errors and binocular vision issues, can cause headaches. The current study evaluates the impact of Neurolens (NL) on individuals with headaches, assessed using the Headache Impact Test (HIT) questionnaire. Methods: Subjects (18-60 years) with good stereoacuity and a HIT score of ≥56 points were enrolled. Each subject wore both control lens and NL for 30 ± 10 days each. The primary outcome of the study was to assess the difference in the HIT score between the two treatments. Results: Of the subjects randomized, 88% (170/195) completed the study. Overall, subjects reported a greater improvement in HIT score improvement with NL compared with control (mean difference, -1.53 points; 95% confidence interval, -2.8 to -0.26; P = 0.01). In the subgroup with reduced NPC, subjects reported a larger improvement in HIT score improvement with NL but was not statistically significant (mean difference, -1.89 points; 95% confidence interval, -4.27 to -0.47; P = 0.11). Conclusions: NL produced a statistically significant decrease in the impact of headaches on individuals' quality of life compared with placebo. Although the overall magnitude of the decrease was not clinically significant, a clinically meaningful improvement with NL cannot be ruled out with high certainty in the current study. Translational Relevance: Headache is one of the most experienced symptoms by individuals worldwide with vision-related disorders being a primary reason. It is, therefore, critical to screen these disorders before providing a pharmacological intervention, which may have side effects. NL provides an objective way to diagnose and treat digital eyestrain-related headaches.

Lags and leads of accommodation in humans: Fact or fiction?

The focusing response of the human eye - accommodation - exhibits errors known as lags and leads. Lags occur when the stimulus is near and the eye appears to focus farther than the stimulus. Leads occur with far stimuli where the eye appears to focus nearer than the stimulus. We used objective and subjective measures simultaneously to determine where the eye is best focused. The objective measures were made with a wavefront sensor and an autorefractor, both of which analyze light reflected from the retina. These measures exhibited typical accommodative errors, mostly lags. The subjective measure was visual acuity, which of course depends not only on the eye's optics but also on photoreception and neural processing of the retinal image. The subjective measure revealed much smaller errors. Acuity was maximized at or very close to the distance of the accommodative stimulus. Thus, accommodation is accurate in terms of maximizing visual performance.

The blur horopter: Retinal conjugate surface in binocular viewing.

From measurements of wavefront aberrations in 16 emmetropic eyes, we calculated where objects in the world create best-focused images across the central 27\(^\circ\) (diameter) of the retina. This is the retinal conjugate surface. We calculated how the surface changes as the eye accommodates from near to far and found that it mostly maintains its shape. The conjugate surface is pitched top-back, meaning that the upper visual field is relatively hyperopic compared to the lower field. We extended the measurements of best image quality into the binocular domain by considering how the retinal conjugate surfaces for the two eyes overlap in binocular viewing. We call this binocular extension the blur horopter. We show that in combining the two images with possibly different sharpness, the visual system creates a larger depth of field of apparently sharp images than occurs with monocular viewing. We examined similarities between the blur horopter and its analog in binocular vision: the binocular horopter. We compared these horopters to the statistics of the natural visual environment. The binocular horopter and scene statistics are strikingly similar. The blur horopter and natural statistics are qualitatively, but not quantitatively, similar. Finally, we used the measurements to refine what is commonly referred to as the zone of clear single binocular vision.

Contributions of foveal and non-foveal retina to the human eye's focusing response.

The human eye changes focus-accommodates-to minimize blur in the retinal image. Previous work has shown that stimulation of nonfoveal retina can produce accommodative responses when no competing stimulus is presented to the fovea. In everyday situations it is very common for the fovea and other parts of the retina to be stimulated simultaneously. We examined this situation by asking how nonfoveal retina contributes to accommodation when the fovea is also stimulated. There were three experimental conditions. (a) Real change in which stimuli of different sizes, centered on the fovea, were presented at different optical distances. Accommodation was, as expected, robust because there was no conflicting stimulation of other parts of the retina. (b) Simulated change, no conflict in which stimuli of different sizes, again centered on the fovea, were presented at different simulated distances using rendered chromatic blur. Accommodation was robust in this condition because there was no conflict between the central and peripheral stimuli. (c) Simulated change, conflict in which a central disk (of different diameters) was presented along with an abutting peripheral annulus. The disk and annulus underwent opposite changes in simulated distance. Here we observed a surprisingly consistent effect of the peripheral annulus. For example, when the diameter of the central stimulus was 8° (thereby stimulating the fovea and parafovea), the abutting peripheral annulus had a significant effect on accommodation. We discuss how these results may help us understand other situations in which nonfixated targets affect the ability to focus on a fixated target. We also discuss potential implications for the development of myopia and for foveated rendering.

Is 25Hz enough to accurately measure a dynamic change in the ocular accommodation? / ¿Son suficientes 25Hz para medir con precisión un cambio dinámico en la acomodación ocular?

Background: Accommodation is often recorded at a low sampling rate using devices such as autorefractors that are designed to measure the static refractive error. It is therefore important to determine if that resolution is sufficient to accurately measure the dynamic properties of accommodation. The current study provides both theoretical and empirical evidence on the ideal sampling rate necessary to measure a dynamic response. Methods: Accommodative and disaccommodative step stimuli ranging from 1-3 D (1 D steps) were presented using a Badal optical system. Responses from 12 children (8-13 years) and 6 adults (20-35 years) were recorded using a dynamic photorefractor (DPR). Fast Fourier transformation was applied to the unsmoothed dynamic responses including position, velocity and acceleration. Also, velocity and acceleration main sequence (MS) characteristics were compared between three photorefractor conditions on 3 subjects. Results: The Nyquist sampling limit necessary to accurately estimate position, velocity and acceleration was at least 5, 10 and 70 Hz, respectively. Peak velocity and acceleration were significantly underestimated at a lower rate (p < 0.5). However, the slope of MS remained invariant with sampling rate (p > 0.5). Conclusion: Contrary to the previous findings, a dynamic accommodative response exhibited frequencies larger than 10Hz. Stimulus direction and amplitude had no influence on the frequencies present in the dynamic response. Peak velocity and acceleration can be significantly underestimated when sampled at a lower rate. Taken as a whole, low sampling rate instruments can accurately estimate static accommodation, however, caution needs to be exercised when using them for dynamic accommodation

La acomodación se registra a menudo a una tasa de muestreo baja, utilizando dispositivos tales como los autorrefractómetros que están diseñados para medir el error refractivo estático. Por tanto, es importante determinar si dicha resolución es suficiente para medir con precisión las propiedades dinámicas de la acomodación. El estudio actual aporta evidencia tanto teórica como empírica acerca de la tasa de muestreo necesaria para medir una respuesta dinámica. Métodos: Se presentaron estímulos de alteraciones de estimulación y relajación (desacomodación) de la acomodación que oscilaron entre 1 y 3 D (pasos de 1 D) utilizando un sistema óptico Badal. Se registraron las respuestas de 12 niños (de 8 a 13 años) y 6 adultos (de 20 a 35 años) utilizando un sistema de fotorrefracción dinámico (DPR). La transformación rápida de Fourier se aplicó a las respuestas dinámicas no uniformes incluyendo posición, velocidad y aceleración. También se compararon las características de la secuencia principal de velocidad y aceleración entre las tres situaciones del sistema de fotorrefracción en 3 sujetos. Resultados: El límite de muestreo de Nyquist necesario para calcular con precisión la posición, velocidad y aceleración fue de al menos 5, 10 y 70Hz respectivamente. La velocidad y aceleración máximas se subestimaron significativamente a una tasa inferior (p < 0,5). Sin embargo, la pendiente de la secuencia principal permaneció invariable con la tasa de muestreo (p > 0,5). Conclusión: Contrariamente a los hallazgos anteriores, la respuesta acomodativa dinámica mostró unas frecuencias superiores a 10Hz. La dirección y amplitud del estímulo no influyeron en las frecuencias presentes en la respuesta dinámica. La velocidad y aceleración máximas pueden subestimarse significativamente cuando se muestrean a una tasa menor. En conjunto, los instrumentos de baja tasa de muestreo pueden calcular con precisión la acomodación estática; sin embargo, debe actuarse con precaución a la hora de calcular la acomodación dinámica

Is 25Hz enough to accurately measure a dynamic change in the ocular accommodation?

BACKGROUND: Accommodation is often recorded at a low sampling rate using devices such as autorefractors that are designed to measure the static refractive error. It is therefore important to determine if that resolution is sufficient to accurately measure the dynamic properties of accommodation. The current study provides both theoretical and empirical evidence on the ideal sampling rate necessary to measure a dynamic response. METHODS: Accommodative and disaccommodative step stimuli ranging from 1-3D (1D steps) were presented using a Badal optical system. Responses from 12 children (8-13 years) and 6 adults (20-35 years) were recorded using a dynamic photorefractor (DPR). Fast Fourier transformation was applied to the unsmoothed dynamic responses including position, velocity and acceleration. Also, velocity and acceleration main sequence (MS) characteristics were compared between three photorefractor conditions on 3 subjects. RESULTS: The Nyquist sampling limit necessary to accurately estimate position, velocity and acceleration was at least 5, 10 and 70Hz, respectively. Peak velocity and acceleration were significantly underestimated at a lower rate (p<0.5). However, the slope of MS remained invariant with sampling rate (p>0.5). CONCLUSION: Contrary to the previous findings, a dynamic accommodative response exhibited frequencies larger than 10Hz. Stimulus direction and amplitude had no influence on the frequencies present in the dynamic response. Peak velocity and acceleration can be significantly underestimated when sampled at a lower rate. Taken as a whole, low sampling rate instruments can accurately estimate static accommodation, however, caution needs to be exercised when using them for dynamic accommodation.

Is blur sensitivity altered in children with progressive myopia?

School aged children with progressive myopia show large accommodative lags to blur only cue which is suggestive of a large depth of focus (DOF). While DOF measures are lacking in this age group, their blur detection and discrimination capacities appear to be similar to their non-myopic peers. Accordingly, the current study quantified DOF and blur detection ability in progressive myopic children showing large accommodative lags compared to their non-myopic peers and adults. Blur sensitivity measures were taken from 12 children (8-13 years, 6 myopes and 6 emmetropes) and 6 adults (20-35 years). DOF was quantified using step changes in the lens induced defocus while the subjects viewed a high contrast target through a Badal lens at either 2 or 4D demand. Blur detection thresholds (BDT) were tested using a similar high contrast target in a 2-alternate forced-choice paradigm (2AFC) at both the demands. In addition to the large accommodative lags, micro fluctuations and DOF were significantly larger in myopic children compared to the other groups. However, BDTs were similar across the three groups. When limited to blur cues, the findings of a large DOF coupled with large response lags suggests that myopes are less sensitive to retinal defocus. However, in agreement to a previous study, refractive error had no influence on their BDTs suggesting that the reduced sensitivity to the defocus in a myopic eye appears to be compensated by some form of an adjustment in the higher visual processes to preserve the subjective percept even with a poor retinal image quality.

Are high lags of accommodation in myopic children due to motor deficits?

Children with a progressing myopia exhibit an abnormal pattern of high accommodative lags coupled with high accommodative convergence (AC/A) and high accommodative adaptation. This is not predicted by the current models of accommodation and vergence. Reduced accommodative plant gain and reduced sensitivity to blur have been suggested as potential causes for this abnormal behavior. These etiologies were tested by altering parameters (sensory, controller and plant gains) in the Simulink model of accommodation. Predictions were then compared to the static and dynamic blur accommodation (BA) measures taken using a Badal optical system on 12 children (6 emmetropes and 6 myopes, 8-13years) and 6 adults (20-35years). Other critical parameters such as CA/C, AC/A, and accommodative adaptation were also measured. Usable BA responses were classified as either typical or atypical. Typical accommodation data confirmed the abnormal pattern of myopia along with an unchanged CA/C. Main sequence relationship remained invariant between myopic and nonmyopic children. An overall reduction was noted in the response dynamics such as peak velocity and acceleration with age. Neither a reduced plant gain nor reduced blur sensitivity could predict the abnormal accommodative behavior. A model adjustment reflecting a reduced accommodative sensory gain (ASG) coupled with an increased AC cross-link gain and reduced vergence adaptive gain does predict the empirical findings. Empirical measures also showed a greater frequency of errors in accommodative response generation (atypical responses) in both myopic and control children compared to adults.