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Objective: To establish a methodology for objectively estimating the Lens Equatorial Plane (LEP) from clinical images, comparing LEP with dilated versus non‐dilated pupils. Methods: A cohort of 91 eyes from 60 patients undergoing preoperative assessments for cataract surgery was evaluated. Anterior Segment Optical Coherence Tomography (AS‐OCT) images were analysed under conditions of pharmacologically induced pupil dilation versus a non‐dilated pupil. Geometrical parameters, including LEP, intersection diameter (ID), lens thickness (LT), anterior and posterior lens thickness were automatically calculated by applying standard image processing techniques to clinical AS‐OCT images. Results: Significant differences in lens parameters, including LEP, were observed between dilated and non‐dilated conditions (all p < 0.001). A strong linear correlation was found across all geometrical variables under both conditions (r[LEP] = 0.64, r[ID] = 0.78, r[LT] = 0.99, all p < 0.001); enabling reliable correction of these differences. Conclusion: The study introduces an objective methodology for LEP calculation, emphasising the need to consider the eye's physiological state during preoperative measurements. Incorporating LEP into future intraocular lens (IOL) power calculation formulas and replacing the habitual effective lens position may potentially improve the accuracy of IOL power estimation and thus postoperative visual outcomes. [ABSTRACT FROM AUTHOR]

Purpose: To analyse and compare image acuity for different refractive errors generated by either altering axial length or corneal curvature and using three human eye models with two pupil sizes. Methods: Three different eye models, Liou‐Brennan, Goncharov and Navarro, were used. Simulations were made (using Ansys Zemax OpticStudio 22.3) for real pupil sizes of 3 and 6 mm with refractive errors ranging from −2 to +2 D in 0.25 D increments. Refractive errors were simulated by varying axial length or corneal curvature. Root mean square (RMS) values were used to determine image acuity. Results: For the 3‐mm pupil, all models gave similar results, with the Navarro model having slightly higher RMS values for the emmetropic eye. For the 6‐mm pupil, the Liou‐Brennan and Goncharov eye models gave similar results, with RMS values lower than for the Navarro eye model. The highest RMS value was visible in the axial length‐induced refractive errors. Refractive errors generated by altering corneal curvature give smaller RMS values than those generated by altering axial length. The axial length and corneal radius simulations indicate a wide spread of results for myopic, hyperopic and emmetropic eyes. There are multiple outcomes that give the same refractive error, even within a single‐eye model. The axial length/corneal curvature ratio showed a higher ratio for myopes than hyperopes for every model. Conclusions: The influence of refractive error on image acuity varied depending on the simulation method of refractive error and the model used. The origins of refractive error and the influence it has on image acuity need further investigation. As models become more sophisticated, personalised and biologically relevant, they will better represent the image acuity of the eye for varying refractive errors, ethnicities, ages and pupil sizes. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the influence of defocus and pupil size on subjective (visual acuity [VA]) and objective (electrophysiology) descriptors of human vision and their effect on binocular visual performance by means of neural binocular summation (BS). Methods: Fifteen healthy young subjects were recruited in this crossover study. Pattern electroretinogram (PERG) and visual evoked potentials (VEP) were measured under two levels of positive (+1.5 and +3.0 D) spherical and astigmatic defocus (axis 90°). Pupil size was controlled to reduce the inter‐individual variability factor. Results: Low‐ and high‐contrast VA showed poorer visual performance in the monocular versus the binocular condition. Positive BS (for VA) was higher with greater pupil size and higher levels of defocus. In the visual electrophysiology tests (i.e., VEP and PERG), peak time and amplitude were affected by pupil size and defocus. The increase in peak time was larger and the reduction in amplitude was more significant with greater levels of defocus and smaller pupil sizes. For the VEP, positive BS was found in all conditions, being stronger with larger amounts of defocus and pupil size (for the P100 amplitude). Significant negative correlations were observed between the P100 amplitude and VA BSs. Conclusion: Smaller pupil size and levels of defocus produced greater changes in cortical activity as evidenced by both the PERG and VEP. Considering these changes and the obtained positive BS, the mechanism could be initiated as early as the retinal processing stage, then being modulated and enhanced along the visual pathway and within the visual cortex. [ABSTRACT FROM AUTHOR]

Objective: To investigate the repeatability of pupil size measurements, determined from the NIDEK OPD‐Scan III, of myopic eyes in children wearing single‐vision spectacles (SVS), undergoing orthokeratology (OK) and receiving combined treatment of 0.01% atropine and orthokeratology (AOK). Methods: A single examiner took two sets of mesopic pupil size measurements from the right eyes of 80 children (SVS:16, OK: 34, AOK: 30) (mesopic 1 and mesopic 2) and two sets of photopic (photopic 1 and photopic 2) pupil size measurements (internal light source) using the NIDEK OPD‐Scan III. Each set was taken at a single visit, 15 min apart. Subjects in the OK and AOK groups had undergone treatment for at least 6 months, and the SVS subjects had no previous myopia treatment other than wearing spectacles. Repeatability of measurements was analysed using intraclass correlation coefficient (ICC), Bland‐Altman (BA) plot, and coefficient of repeatability (CoR). Results: Mesopic 1 and 2 values were not significantly different among the three groups (p = 0.56, 0.77), hence the data were pooled for each set of measurements (mean [±S.D.] values were 7.09 ± 0.61 and 7.12 ± 0.61 mm, respectively) for further analyses. ICC for repeated mesopic pupil size measurements was 0.98 (95% CI, 0.98–0.99). No significant correlation was found between the means of the mesopic 1 and 2 measurements and their differences (Pearson's r = −0.02, p = 0.83). A BA plot also demonstrated narrow 95% limits of agreement, with a CoR of 0.28 mm. Mean photopic 1 and 2 measurements for the AOK group (3.74 ± 0.46; 3.73 ± 0.43 mm, respectively) were significantly larger (p = 0.01; 0.009) than those of the SVS and OK groups, but no significant difference was found between the latter two groups (p > 0.05). Hence, photopic 1 and 2 measurements for the SVS and OK groups were pooled (SVS‐OK) for further analyses. ICC for repeatability of the photopic measurements was 0.98 (95% CI, 0.96 to 0.99) for the SVS‐OK and AOK groups. The differences between photopic 1 and 2 measurements were not significantly correlated with their means, either in the AOK group (Pearson's r = −0.25, p = 0.19), or in the pooled SVS‐OK group (Pearson's r = −0.04, p = 0.78). BA plots also showed narrow 95% limits of agreement, and CoR was 0.25 mm and 0.23 mm in the AOK and pooled SVS‐OK groups, respectively. Conclusion: Mesopic and photopic pupil size measurement using the NIDEK OPD‐Scan III was highly repeatable and suitable for use on children. [ABSTRACT FROM AUTHOR]

Purpose To examine the separate and combined influences of zone geometry, pupil size, diffraction, apodisation and spherical aberration on the optical performance of concentric zonal bifocals. Methods Zonal bifocal pupil functions representing eye + ophthalmic correction were defined by interleaving wavefronts from separate optical zones of the bifocal. A two-zone design (a central circular inner zone surrounded by an annular outer-zone which is bounded by the pupil) and a five-zone design (a central small circular zone surrounded by four concentric annuli) were configured with programmable zone geometry, wavefront phase and pupil transmission characteristics. Using computational methods, we examined the effects of diffraction, Stiles Crawford apodisation, pupil size and spherical aberration on optical transfer functions for different target distances. Results Apodisation alters the relative weighting of each zone, and thus the balance of near and distance optical quality. When spherical aberration is included, the effective distance correction, add power and image quality depend on zone-geometry and Stiles Crawford Effect apodisation. When the outer zone width is narrow, diffraction limits the available image contrast when focused, but as pupil dilates and outer zone width increases, aberrations will limit the best achievable image quality. With two-zone designs, balancing near and distance image quality is not achieved with equal area inner and outer zones. With significant levels of spherical aberration, multi-zone designs effectively become multifocals. Conclusion Wave optics and pupil varying ocular optics significantly affect the imaging capabilities of different optical zones of concentric bifocals. With two-zone bifocal designs, diffraction, pupil apodisation spherical aberration, and zone size influence both the effective add power and the pupil size required to balance near and distance image quality. Five-zone bifocal designs achieve a high degree of pupil size independence, and thus will provide more consistent performance as pupil size varies with light level and convergence amplitude. [ABSTRACT FROM AUTHOR]

We extended an earlier study (Vision Research, 45, 1967–1974, 2005) in which we investigated limits at which induced blur of letter targets becomes noticeable, troublesome and objectionable. Here we used a deformable adaptive optics mirror to vary spherical defocus for conditions of a white background with correction of astigmatism; a white background with reduction of all aberrations other than defocus; and a monochromatic background with reduction of all aberrations other than defocus. We used seven cyclopleged subjects, lines of three high-contrast letters as targets, 3–6 mm artificial pupils, and 0.1–0.6 logMAR letter sizes. Subjects used a method of adjustment to control the defocus component of the mirror to set the ‘just noticeable’, ‘just troublesome’ and ‘just objectionable’ defocus levels. For the white-no adaptive optics condition combined with 0.1 logMAR letter size, mean ‘noticeable’ blur limits were ±0.30, ±0.24 and ±0.23 D at 3, 4 and 6 mm pupils, respectively. White-adaptive optics and monochromatic-adaptive optics conditions reduced blur limits by 8% and 20%, respectively. Increasing pupil size from 3–6 mm decreased blur limits by 29%, and increasing letter size increased blur limits by 79%. Ratios of troublesome to noticeable, and of objectionable to noticeable, blur limits were 1.9 and 2.7 times, respectively. The study shows that the deformable mirror can be used to vary defocus in vision experiments. Overall, the results of noticeable, troublesome and objectionable blur agreed well with those of the previous study. Attempting to reduce higher-order aberrations or chromatic aberrations, reduced blur limits to only a small extent. [ABSTRACT FROM AUTHOR]

Concurrent measurements of steady-state accommodation response/stimulus curves and of pupil diameter were made in groups ( n = 20) of young, adult myopes [age (mean ± SD) 23.1 ± 4.5 years, mean-sphere error (MSE) −3.06 ± 2.35 D, range −0.60 to −8.54 D] and emmetropes (mean age 25.3 ± 5.7 years, mean MSE −0.07 ± 0.26 D, range −0.50 to +0.50 D). The aim of this study was to explore the possibilities that pupil diameters with relaxed accommodation were larger, and that accommodative miosis was weaker, in the myopic group. Such behaviour would lead to relatively greater degradation of the retinal images in the myopic group, even though aberrations at constant pupil diameter and dioptric accommodative lags in the two groups were the same: this might result in excessive axial growth and further myopia development. No evidence for any systematic refractive dependence of pupillary characteristics or accommodative responses was found. Interestingly, those subjects whose response/stimulus curves had a higher slope tended to display greater accommodative miosis, irrespective of their refractive error. [ABSTRACT FROM AUTHOR]

The calculation of the extent of the ring scotoma around positive lenses, as conventionally taught to students of clinical optics, indicates that the scotoma is of a significant size. Using knife-edge lenses this study shows that the calculations are invalid due to the finite size of the eye's entrance pupil and in many instances the scotoma is shown not to exist. The effect noticed in clinical practice is probably largely due to the frame and the edging techniques used which add to the refractive scotoma which is present with high powered lenses, large apertures and/or small pupil sizes. [ABSTRACT FROM AUTHOR]

The literature suggests that there may be pupil size and response abnormalities in migraine headache sufferers. We used an infra-red pupillometer to measure dynamic pupil responses to light in 20 migraine sufferers (during non-headache periods) and 16 non-migraine age and gender matched controls. There was a significant increase in the absolute inter-ocular difference of the latency of the pupil light response in the migraine group compared with the controls (0.062 s vs 0.025 s,p = 0.014). There was also a significant correlation between anisocoria and lateralisation of headache such that migraine sufferers with a habitual head pain side have more anisocoria (r = 0.59,p < 0.01), but this was not related to headache laterality. The pupil changes were not correlated with the interval since the last migraine headache, the severity of migraine headache or the number of migraine headaches per annum. We conclude that subtle sympathetic and parasympathetic pupil abnormalities persist in the inter-ictal phase of migraine. [ABSTRACT FROM AUTHOR]

The infrared photorefractor PowerRef II (PR II; PlusoptiX AG, Nürnberg, Germany) uses the principle of eccentric photorefraction. In eight subjects the mean non-cycloplegic refraction measured with the‘Full Scan’ mode of the PR II at a far viewing distance (0.2 D) was significantly more hypermetropic by 0.6 D compared with subjective refraction. The mean accommodation differed by about this same amount between the PR II and the Canon R1 at three different viewing distances (3, 2 and 1 D). The PR II refraction at the 1 m reference distance was 0.25 D more hypermetropic compared with the subjective refraction at far (5 m); these measures were moderately correlated (r = 0.7). To determine temporal changes, the‘Dynamic Scan’ mode was used over a 2-min period: the mean intraindividual standard deviation was 0.32 mm for pupil diameter and 0.29 D for accommodation, while the absolute measurement error of the‘Dynamic Scan’ was found to be<0.12 D for the accommodation data. Interindividual reliabilities were satisfactory. However, the PR II did not provide a continuous stream of data and the specified sampling frequency of 25 Hz was rarely realized. [ABSTRACT FROM AUTHOR]

If it is assumed that the differences between eyes constitute adaptations to different visual environments, then it should be possible to identify the visual environments for which the eye is optimised from these differences. Two different classes of simple eye shapes can be distinguished from the ratio of maximum pupil size to the axial length of an eye. The quantitative description of the two different eye shapes can be used to identify the relative importance of image illumination and resolution to an animal from a cross-section of its eye. [ABSTRACT FROM AUTHOR]