Comparison of a Novel Binocular Refraction System with Standard Digital Phoropter Refraction.

SIGNIFICANCE: New refractive technologies are consistently emerging in the optometry market, necessitating validation against current clinical standards. PURPOSE: This study aimed to compare the refractive measurements between standard digital phoropter refraction and the Chronos binocular refraction system. METHODS: Standardized subjective refraction was conducted on 70 adult participants using two separate refraction systems. The final subjective values from both devices were compared for M , J0 , and J45 . The time taken to complete refraction and patient's comfort were also evaluated. RESULTS: Good agreement was found between the standard and Chronos refraction, with narrow mean differences (including 95% confidence intervals) and no significant bias for M (0.03 D, -0.05 to 0.11 D), J0 (-0.02 D, -0.05 to -0.01 D), and J45 (-0.01 D, -0.03 to 0.01 D). The bounds of the limits of agreement of M were -0.62 (lower bound; -0.76 to -0.49) and 0.68 (upper bound; 0.54 to 0.81), those of J0 were -0.24 (lower bound; -0.29 to -0.19) and 0.19 (upper bound; 0.15 to 0.24), and those of J45 were -0.18 (lower bound; -0.21 to -0.14) and 0.16 (upper bound; 0.12 to 0.19). No significant differences were noted between the two techniques for any of the refraction components ( M standard = -3.03 ± 2.42 D, M novel = -3.06 ± 2.37 D, z = 0.07, P = .47; J0 standard = 0.12 ± 0.40 D, J0 novel = 0.15 ± 0.41 D, z = 1.32, P = .09; J45 standard = -0.04 ± 0.19 D, J45 novel = -0.03 ± 0.19 D, z = 0.50, P = .31). The Chronos was significantly faster than the standard technique, with an average difference of 19 seconds (standard, 190 ± 44 seconds; novel, 171 ± 38 seconds; z = 4.91; P < .001). CONCLUSIONS: The final subjective refraction end points of the standard technique and the Chronos were well aligned in this group of adult participants, and no statistically or clinically significant differences were noted in M , J0 , or J45 components. The Chronos offered improved efficiency, meeting the demands of eye care.

Individualized modeling for the peripheral optics of the human myopic eye.

Individualized optical modelling of the eye is a useful tool to estimate optical properties of the eye from a set of geometrical parameters. In the context of myopia research, it is important to understand not only the on-axis (foveal) optical quality, but also the peripheral profile. This work describes a method to extend on-axis individualized eye modeling to the peripheral retina. Using measurements of corneal geometry, axial distances, and central optical quality from a group of young adults, a crystalline lens model was built to help reproduce the peripheral optical quality of the eye. Subsequent individualized eye models were generated from each of the 25 participants. These models were used to predict the individual peripheral optical quality over the central 40 degrees. Outcomes of the final model were then compared to the actual measurements of peripheral optical quality in these participants, measured with a scanning aberrometer. A high agreement was found between the final model and measured optical quality for the relative spherical equivalent and J0 astigmatism.

Baseline metrics that may predict future myopia in young children.

PURPOSE: We used baseline data from the PICNIC longitudinal study to investigate structural, functional, behavioural and heritable metrics that may predict future myopia in young children. METHODS: Cycloplegic refractive error (M) and optical biometry were obtained in 97 young children with functional emmetropia. Children were classified as high risk (HR) or low risk (LR) for myopia based on parental myopia and M. Other metrics included axial length (AXL), axial length/corneal radius (AXL/CR) and refractive centile curves. RESULTS: Based on the PICNIC criteria, 46 children (26 female) were classified as HR (M = +0.62 ± 0.44 D, AXL = 22.80 ± 0.64 mm) and 51 (27 female) as LR (M = +1.26 ± 0.44 D, AXL = 22.77 ± 0.77 mm). Based on centiles, 49 children were HR, with moderate agreement compared with the PICNIC classification (k = 0.65, p < 0.01). ANCOVA with age as a covariate showed a significant effect for AXL (p < 0.01), with longer AXL and deeper anterior chamber depth (ACD) (p = 0.01) in those at HR (differences AXL = 0.16 mm, ACD = 0.13 mm). Linear regression models showed that central corneal thickness (CCT), ACD, posterior vitreous depth (PVD) (=AXL - CCT - ACD-lens thickness (LT)), corneal radius (CR) and age significantly predicted M (R = 0.64, p < 0.01). Each 1.00 D decrease in hyperopia was associated with a 0.97 mm elongation in PVD and 0.43 mm increase in CR. The ratio AXL/CR significantly predicted M (R = -0.45, p < 0.01), as did AXL (R = -0.25, p = 0.01), although to a lesser extent. CONCLUSIONS: Although M and AXL were highly correlated, the classification of pre-myopic children into HR or LR was significantly different when using each parameter, with AXL/CR being the most predictive metric. At the end of the longitudinal study, we will be able to assess the predictability of each metric.

Retinal Responses to Simulated Optical Blur Using a Novel Dead Leaves ERG Stimulus.

Purpose: The purpose of this study was to evaluate retinal responses to different types and magnitudes of simulated optical blur presented at specific retinal eccentricities using naturalistic images. Methods: Electroretinograms (ERGs) were recorded from 27 adults using 30-degree dead leaves naturalistic images, digitally blurred with one of three types of optical blur (defocus, astigmatism, and spherical aberrations), and one of three magnitudes (0.1, 0.3, or 0.5 µm) of blur. Digitally computed blur was applied to the entire image, or on an area outside the central 6 degrees or 12 degrees of retinal eccentricity. Results: ERGs were significantly affected by blur type, magnitude, and retinal eccentricity. ERGs were differentially affected by defocus and spherical aberrations; however, astigmatism had no effect on the ERGs. When blur was applied only beyond the central 12 degrees eccentricity, the ERGs were unaffected. However, when blur was applied outside the central 6 degrees, the ERG responses were significantly reduced and were no different from the ERGs recorded with entirely blurred images. Conclusions: Blur type, magnitude, and location all affect the retinal responses. Our data indicate that the retinal area between 6 and 12 degrees eccentricity has the largest effect on the retinal responses to blur. In addition, certain optical blur types appear to have a more detrimental effect on the ERGs than others. These results cannot be solely explained by changes to image contrast and spatial frequency content, suggesting that retinal neurons might be sensitive to spatial cues in order to differentiate between different blur types.

IMI Accommodation and Binocular Vision in Myopia Development and Progression.

The role of accommodation in myopia development and progression has been debated for decades. More recently, the understanding of the mechanisms involved in accommodation and the consequent alterations in ocular parameters has expanded. This International Myopia Institute white paper reviews the variations in ocular parameters that occur with accommodation and the mechanisms involved in accommodation and myopia development and progression. Convergence is synergistically linked with accommodation and the impact of this on myopia has also been critiqued. Specific topics reviewed included accommodation and myopia, role of spatial frequency, and contrast of the task of objects in the near environment, color cues to accommodation, lag of accommodation, accommodative-convergence ratio, and near phoria status. Aspects of retinal blur from the lag of accommodation, the impact of spatial frequency at near and a short working distance may all be implicated in myopia development and progression. The response of the ciliary body and its links with changes in the choroid remain to be explored. Further research is critical to understanding the factors underlying accommodative and binocular mechanisms for myopia development and its progression and to guide recommendations for targeted interventions to slow myopia progression.

Effects of temporal frequency on binocular deficits in amblyopia.

Amblyopia is associated with a range of well-known visual spatial deficits, which include reduced contrast sensitivity, spatial distortions, interocular suppression, and impaired stereopsis. Previous work has also pointed to deficits in processing dynamic visual information, but it is unknown whether these deficits influence performance under binocular conditions. We examined the effects of temporal modulation on contrast sensitivity and binocular interactions in a preliminary study of 8 adults with amblyopia and 14 normally-sighted control subjects. For each observer, we measured interocular balance and stereopsis thresholds with binocular flicker across a range of four temporal (0, 4, 7.5, and 12 Hz) and spatial (1, 2, 4, and 8 cpd) frequencies. Interocular balance was estimated by varying the relative contrast of dichoptic letter pairs to produce perceptual reports of each letter with equal frequency, and stereopsis thresholds were measured by determining the minimum disparity at which subjects identified a front-depth target with 75% accuracy. Consistent with previous findings, we observed greater interocular imbalance and impaired stereoacuity at high spatial frequencies in amblyopes. In contrast, the effects of temporal frequency on performance were smaller: across both groups, interocular imbalance was largest at mid-to-low temporal frequencies, and stereopsis thresholds were unaffected by temporal frequency. Our results suggest that there may be a previously unreported effect of temporal frequency on interocular balance, as well as a possible dissociation between the effects of flicker on interocular balance and stereopsis.

Stimulus Unpredictability in Time, Magnitude, and Direction on Accommodation.

SIGNIFICANCE: The effect of predictability in changes of time, magnitude, and direction of the accommodation demand on the accommodation response latency and its magnitude are insignificant, which suggests that repetitive accommodative tasks such as the clinical accommodative facility test may not be influenced by potential anticipation effects. PURPOSE: The purpose of this study was to investigate the effect of stimulus' time, magnitude, and direction predictability, as well as their interactions, on accommodation latency and response magnitude. METHODS: Monocular accommodative response and latency were measured in 12 young subjects for nine different conditions where the stimulus accommodative demand changed several times in a steplike fashion for a period of 120 seconds. Each change in accommodative demand could have different time duration (i.e., 1, 2, or 3 seconds), magnitude (1, 2, or 3 diopters), and/or direction (i.e., accommodation or disaccommodation). All conditions were created permuting the factors of time, magnitude, and direction with two levels each: random and not random. The baseline condition was a step signal from 0 to 2 diopters persisting for 2 seconds in both accommodative demands. After each condition, subjects were asked to provide a score from 1 to 5 in their perceived predictability. RESULTS: Friedman test conducted on the perceived predictability of each condition resulted in statistically significant differences between the nine conditions (χ = 56.57, P < .01). However, repeated-measures analysis of variance applied to latency and accommodative response magnitude did not show significant differences (P > .05). In addition, no correlation was found between the perceived predictability scores and both latency and accommodative response magnitudes between the most predictable and the most unpredictable conditions. CONCLUSIONS: Subjects were able to perceptually notice whether the stimulus was predictable or not, although our results indicate no significant effect of stimuli predictability on either the accommodation latency or its magnitude.

IMI - Industry Guidelines and Ethical Considerations for Myopia Control Report.

Purpose: To discuss guidelines and ethical considerations associated with the development and prescription of treatments intended for myopia control (MC). Methods: Critical review of published papers and guidance documents was undertaken, with a view to carefully considering the ethical standards associated with the investigation, development, registration, marketing, prescription, and use of MC treatments. Results: The roles and responsibilities of regulatory bodies, manufacturers, academics, eye care practitioners, and patients in the use of MC treatments are explored. Particular attention is given to the ethical considerations for deciding whether to implement a MC strategy and how to implement this within a clinical trial or practice setting. Finally, the responsibilities in marketing, support, and education required to transfer required knowledge and skills to eye care practitioners and academics are discussed. Conclusions: Undertaking MC treatment in minors creates an ethical challenge for a wide variety of stakeholders. Regulatory bodies, manufacturers, academics, and clinicians all share an ethical responsibility to ensure that the products used for MC are safe and efficacious and that patients understand the benefits and potential risks of such products. This International Myopia Institute report highlights these ethical challenges and provides stakeholders with recommendations and guidelines in the development, financial support, prescribing, and advertising of such treatments.

Binocular temporal visual processing in myopia.

Our ability to utilize binocular visual information depends on the visibility of the retinal images in each eye, which varies with both their spatial and temporal frequency content. Although the effects of spatial information on binocular function have been established, the effects of temporal frequency on binocularity are less well understood. These factors may also vary with refractive error if spatiotemporal sensitivity is affected by structural changes during the emmetropization process that may differentially affect distinct ganglion cells. In a cross-sectional study, we evaluated the potential effects of temporal and spatial frequency on binocularity in young individuals with emmetropia or myopia. Stereopsis and binocular balance were measured as a function of temporal (0-12 Hz) and spatial (1-8 c/deg) frequency. Stereopsis thresholds were measured by determining the minimum disparity at which subjects accurately identified the depth of bandpass-filtered rings. Binocular balance was measured by determining the relative contrast at which subjects reported dichoptic bandpass-filtered letters with equal frequency. Stereopsis thresholds were temporal but not spatial frequency dependent whereas binocular balance was spatial and temporal frequency dependent. There were no differences in monocular spatiotemporal contrast sensitivity between refractive groups in our sample. However, individuals with myopia showed reduced stereopsis with flickering stimuli and greater binocular imbalance at higher spatial and lower temporal frequencies compared to emmetropes. Differences in binocular vision between emmetropia and corrected myopia depend on temporal as well as spatial frequency and may be the cause or consequence of abnormal emmetropization during visual development.

Random Changes of Accommodation Stimuli: An Automated Extension of the Flippers Accommodative Facility Test.

PURPOSE: To study the accommodative dynamics for predictable and unpredictable stimuli using manual and automated accommodative facility tests Materials and Methods: Seventeen young healthy subjects were tested monocularly in two consecutive sessions, using five different conditions. Two conditions replicated the conventional monocular accommodative facility tests for far and near distances, performed with manually held flippers. The other three conditions were automated and conducted using an electro-optical system and open-field autorefractor. Two of the three automated conditions replicated the predictable manual accommodative facility tests. The last automated condition was a hybrid approach using a novel method whereby far and near-accommodative-facility tests were randomly integrated into a single test of four unpredictable accommodative demands. RESULTS: The within-subject standard deviations for far- and near-distance-accommodative reversals were (±1,±1) cycles per minute (cpm) for the manual flipper accommodative facility conditions and (±3, ±4) cpm for the automated conditions. The 95% limits of agreement between the manual and the automated conditions for far and near distances were poor: (-18, 12) and (-15, 3). During the hybrid unpredictable condition, the response time and accommodative response parameters were significantly (p < 0.05) larger for accommodation than disaccommodation responses for high accommodative demands only. The response times during the transitions 0.17/2.17 D and 0.50/4.50 D appeared to be indistinguishable between the hybrid unpredictable and the conventional predictable automated tests. CONCLUSIONS: The automated accommodative facility test does not agree with the manual flipper test results. Operator delays in flipping the lens may account for these differences. This novel test, using unpredictable stimuli, provides a more comprehensive examination of accommodative dynamics than conventional manual accommodative facility tests. Unexpectedly, the unpredictability of the stimulus did not to affect accommodation dynamics. Further studies are needed to evaluate the sensitivity of this novel hybrid technique on individuals with accommodative anomalies.

Vergence driven accommodation with simulated disparity in myopia and emmetropia.

The formation of focused and corresponding foveal images requires a close synergy between the accommodation and vergence systems. This linkage is usually decoupled in virtual reality systems and may be dysfunctional in people who are at risk of developing myopia. We study how refractive error affects vergence-accommodation interactions in stereoscopic displays. Vergence and accommodative responses were measured in 21 young healthy adults (n=9 myopes, 22-31 years) while subjects viewed naturalistic stimuli on a 3D display. In Step 1, vergence was driven behind the monitor using a blurred, non-accommodative, uncrossed disparity target. In Step 2, vergence and accommodation were driven back to the monitor plane using naturalistic images that contained structured depth and focus information from size, blur and/or disparity. In Step 1, both refractive groups converged towards the stereoscopic target depth plane, but the vergence-driven accommodative change was smaller in emmetropes than in myopes (F1,19=5.13, p=0.036). In Step 2, there was little effect of peripheral depth cues on accommodation or vergence in either refractive group. However, vergence responses were significantly slower (F1,19=4.55, p=0.046) and accommodation variability was higher (F1,19=12.9, p=0.0019) in myopes. Vergence and accommodation responses are disrupted in virtual reality displays in both refractive groups. Accommodation responses are less stable in myopes, perhaps due to a lower sensitivity to dioptric blur. Such inaccuracies of accommodation may cause long-term blur on the retina, which has been associated with a failure of emmetropization.

Effect of Experimental Conditions in the Accommodation Response in Myopia.

SIGNIFICANCE: The accommodative response is more affected by the type of refractive error than the method of stimulation, field of view (FOV), or stimulus depth. PURPOSE: This study aims to analyze the effect of stimulation method, stimulus depth, and FOV on the accommodation response (AR) for emmetropes (EMM), late-onset myopes (LOM), and early-onset myopes (EOM). METHODS: Monocular AR was measured in 26 young observers (n = 9 EMM, n = 8 LOM, n = 9 EOM) under 60 different viewing conditions that were the result of permuting the following factors: (1) stimulation method (free space or Badal lens viewing), (2) stimulus depth (flat or volumetric), (3) FOV (2.5, 4, 8, 10, and 30°), and (4) accommodative stimulus (AS: 0.17, 2.50, and 5.00 diopters [D]). RESULTS: Mixed analysis of variance for 2.50 D of AS resulted in a significant effect of refractive group (F = 6.77, P < .01) and FOV (F = 1.26, P = .04). There was also a significant interaction between stimulus depth and FOV (F = 2.73, P = .03) and among stimulation method, FOV, and refractive group (F = 2.42, P = .02). For AS of 5.00 D, there was a significant effect of refractive group (F = 13.88, P < .01) and stimulation method (F = 5.16, P = .03). There was also a significant interaction of stimulation method, stimulus depth, and refractive group (F = 4.08, P = .03). When controlling for all interactions, LOM showed larger lags than EMM and EOM; the AR did not significantly change for fields of 8, 10, and 30°, and it did not significantly differ for different stimulation methods or stimulus depth. CONCLUSIONS: Previously reported differences in AR when using lens-based methods compared with free space viewing may be explained by the effect of other factors such as the FOV or the depth of the stimulus. Targets with an FOV of 8 or 10° may be optimal for accurate ARs.

Blur Adaptation to Central Retinal Disease.

Purpose: The long-term, low-resolution vision experienced by individuals affected by retinal disease that causes central vision loss (CVL) may change their perception of blur through adaptation. This study used a short-term adaptation paradigm to evaluate adaptation to blur and sharpness in patients with CVL. Methods: A variation of Webster's procedure was used to measure the point of subjective neutrality (PSN). The image that appeared normal after adaptation to each of seven blur and sharpness levels (PSN) was measured in 12 patients with CVL (20/60 to 20/320) and 5 subjects with normal sight (NS). Patients with CVL used a preferred retinal locus to view the images. Small control studies investigated the effects of long-term and medium-term (1 hour) defocus and diffusive blur. Results: Adaptation was reliably measured in patients with CVL and in the peripheral vision of NS subjects. The shape of adaptation curves was similar in patients with CVL and both central and peripheral vision of NS subjects. No statistical correlations were found between adaptation and age, visual acuity, retinal eccentricity, or contrast sensitivity. Long-term blur experience by a non-CVL myopic participant caused a shift in the adaptation function. Conversely, medium-term adaptation did not cause a shift in the adaptation function. Conclusions: Blur and sharp short-term adaptation occurred in peripheral vision of normal and diseased retinas. In most patients with CVL, neither adaptation nor blur perception was affected by long-term attention to peripheral low-resolution vision. The impact of blur/sharp adaptation on the benefit of image enhancement techniques for patients with CVL is discussed.

Blur perception throughout the visual field in myopia and emmetropia.

We evaluated the ability of emmetropic and myopic observers to detect and discriminate blur across the retina under monocular or binocular viewing conditions. We recruited 39 young (23-30 years) healthy adults (n = 19 myopes) with best-corrected visual acuity 0.0 LogMAR (20/20) or better in each eye and no binocular or accommodative dysfunction. Monocular and binocular blur discrimination thresholds were measured as a function of pedestal blur using naturalistic stimuli with an adaptive 4AFC procedure. Stimuli were presented in a 46° diameter window at 40 cm. Gaussian blur pedestals were confined to an annulus at either 0°, 4°, 8°, or 12° eccentricity, with a blur increment applied to only one quadrant of the image. The adaptive procedure efficiently estimated a dipper shaped blur discrimination threshold function with two parameters: intrinsic blur and blur sensitivity. The amount of intrinsic blur increased for retinal eccentricities beyond 4° (p < 0.001) and was lower in binocular than monocular conditions (p < 0.001), but was similar across refractive groups (p = 0.47). Blur sensitivity decreased with retinal eccentricity (p < 0.001) and was highest for binocular viewing, but only for central vision (p < 0.05). Myopes showed worse blur sensitivity than emmetropes monocularly (p < 0.05) but not binocularly (p = 0.66). As expected, blur perception worsens in the visual periphery and binocular summation is most evident in central vision. Furthermore, myopes exhibit a monocular impairment in blur sensitivity that improves under binocular conditions. Implications for the development of myopia are discussed.

Peripheral contrast sensitivity and attention in myopia.

Disruption of normal visual experience or changes in the normal interaction between central and peripheral retinal input may lead to the development of myopia. In order to examine the relationship between peripheral contrast sensitivity and myopia, we manipulated attentional load for foveal vision in emmetropes and myopes while observers detected targets with peripheral vision. Peripheral contrast detection thresholds were measured binocularly using vertical Gabor stimuli presented at three eccentricities (±8°, 17°, 30°) in a spatial 2 alternative forced choice task. Contrast thresholds were measured in young adult (mean age 24.5±2.6years) emmetropes (n=17; group SE: +0.19±0.32D) and myopes (n=25; group SE: -3.74±1.99D). Attention at central fixation was manipulated with: (1) a low attention task, requiring simple fixation; or (2) a high attention task, which required subjects to perform a mathematical task. We found that at 30° all subjects exhibited lower contrast sensitivity (higher thresholds). In addition, myopes (Wilcoxon, p<0.01), but not emmetropes (Wilcoxon, p=0.1), had a significant decrease in sensitivity at 30° during the high attention task. However, the attention dependent threshold increase for myopes was not significantly greater than for emmetropes (Wilcoxon, p=0.27). Attentional load did not increase thresholds at 8° or 17° for either refractive group. These data indicate that myopes experience a greater decrease in contrast sensitivity in the far periphery than emmetropes when attention is deployed in central vision.

Design and Clinical Evaluation of a Handheld Wavefront Autorefractor.

PURPOSE: To introduce a novel autorefractor design that is intended to be manufacturable at low cost and evaluate its performance in measuring refractive errors. METHODS: We developed a handheld, open-view autorefractor (the "QuickSee" [QS]) that uses a simplified approach to wavefront sensing that forgoes moving parts and expensive components. Adult subjects (n = 41) were recruited to undergo noncycloplegic refraction with three methods: (1) a QS prototype, (2) a Grand Seiko WR-5100K (GS) autorefractor, and (3) subjective refraction (SR). Agreements between the QS and GS were evaluated using a Bland-Altman analysis. The accuracy of both autorefractors was evaluated using SR as the clinical gold standard. RESULTS: The spherical equivalent powers measured from both autorefractors correlate well with SR, with identical correlation coefficients of r = 0.97. Both autorefractors also agree well with each other, with a spherical equivalent power 95% confidence interval of ±0.84 diopters (D). The difference between the accuracy of each objective device is not statistically significant for any component of the power vector (p = 0.55, 0.41, and 0.18, for M, J0, and J45, respectively). The spherical and cylindrical powers measured by the GS agree within 0.25 D of the SR in 49 and 82% of the eyes, respectively, whereas the spherical and cylindrical powers measured by the QS agree within 0.25 D of the SR in 74 and 87% of the eyes, respectively. CONCLUSIONS: The prototype autorefractor exhibits equivalent performance to the GS autorefractor in matching power vectors measured by SR.

Abandonment of low-vision devices in an outpatient population.

PURPOSE: To investigate abandonment rate of prescribed low-vision devices for near tasks and factors associated with abandonment in a U.S. outpatient population. METHODS: A telephone survey was administered to 88 patients with low vision from four clinical sites about 1 year after examination and prescription of devices. Patients were surveyed on timing and frequency of use and reasons for abandonment of devices. The main outcome measure (abandonment) was defined as patient report of no use of prescribed device in the previous 3 months. Multivariate logistic regression was used to investigate significant vision and demographic factors related to abandonment. RESULTS: Of 119 prescribed devices, 19% (95% CI, 12 to 26) had not been used within the previous 3 months. Mean (±SD) better eye visual acuity at examination was 0.61 ± 0.29 logMAR, and mean age was 77 ± 17 years. Mean time between device prescription and survey was 11 ± 3 months. Device abandonment was not associated with age (p = 0.863), time since prescription (p = 0.125), visual acuity (p = 0.804), or category of magnification device (spectacle, handheld, stand, or video) (p = 0.412). There was a significant association between documented non-central visual field loss and abandonment of magnification device (p = 0.046). Repeat administration of the survey resulted in the same abandonment classification in 15 of 15 patients (100%). CONCLUSIONS: Abandonment rate was similar for this outpatient population to those previously reported in the U.S. veteran inpatient population and in other countries. Patients with visual field loss may be more likely to abandon prescribed devices.

A relationship between tolerance of blur and personality.

PURPOSE: To determine whether tolerance of dioptric spherical defocus is related to measures of personality. Clinical observations suggest that there is individual variability in tolerance of blur. METHODS: A computer-controlled Badal optometer was used to measure just-noticeable blur and just-objectionable blur responses to positive lens defocus. Blur tolerance was defined as the difference between these two responses. A personality battery was administered consisting of the NEO-FFI (Neuroticism-Extroversion-Openness-Five Factor Inventory) and the California Adult Q-sort (general measures), as well as individual measures (hypothesis-driven scales) of perfectionism, neuroticism, highly sensitive person, ego resiliency, need for structure, and negative emotionality. Ninety-nine normally sighted subjects (median age, 21 years, median refractive error 0.6 DS) completed both parts of the study. RESULTS: Within-subject blur tolerance measures with three different pupil sizes correlated highly (r(s) = 0.79-0.86), implying good repeatability. There was a wide range of individual blur tolerance (0.0-2.7 D). The personality questionnaires exhibited acceptable reliability (Cronbach's α = 0.67-0.91). Two perfectionism scales correlated significantly with blur tolerance (r = 0.25 and 0.27). The 15 questionnaire items that correlated most with blur tolerance were factor analyzed and yielded two conceptually meaningful factors (both α = 0.76). The "low self confidence" and "disorganization" factors correlated positively with blur tolerance (r = 0.38 and 0.36, respectively) and their composite correlated with blur tolerance (r = 0.46). CONCLUSIONS: These results provide the first evidence of a relationship between personality and tolerance of blur. Tolerance of blur may be related to perception of image quality. If so, personality may influence refractive error correction and development and other choices that are made when presented with degraded images.

Shape and individual variability of the blur adaptation curve.

We are interested in clinical implications of adaptation to blurred and sharpened images. Therefore, we investigated repeatability, individual variability and characteristics of the adaptation curves of 39 normally-sighted individuals. The point of subjective neutrality (PSN - the slope of the spatial spectrum of the image that appears normal) following adaptation was measured for each adaptation level and was used to derive individual adaptation curves for each subject. Adaptation curves were fitted with a modified Tukey biweight function as the curves were found to be tumbled-S shaped and asymmetrical for blur and sharp in some subjects. The adaptation curve was found to be an individual characteristic as inter-subject variability exceeds test/re-test variability. The existence of individual variability may have implications for the prescription and clinical success of optical devices as well as image enhancement rehabilitation options.

Monocular fixation with the optic nerve head: a case report.

PURPOSE: To document and discuss the case of a patient with left esotropia (ET) who uses the left optic nerve head (ONH) for monocular 'fixation'. CASE REPORT: The patient was an 80-year-old male with left ET from early childhood. Retinal tracking monocular fixation measurements with a Nidek MP-1 revealed stable fixation within the left ONH area. In an attempt to challenge the initial observation, further assessments of fixation were performed with a smaller target size and requiring various gaze positions. MP-1 fixation data showed remarkably stable monocular fixation (+/-1 degrees over 30 s) mostly within the left ONH for all the target sizes and positions of gaze tested. Additional clinical binocular evaluations showed concomitant left ET approximately 28 Delta, no movement with cover test regardless of fixation target and no significant monocular motility restrictions. Visuoscopy also revealed fixation at the left ONH. There was a strong family history of ET, but none of the other affected descendants tested (n = 3) demonstrated the same behaviour. CONCLUSIONS: This is the first report documenting an abnormally developed monocular ocular motor system, with principal visual direction and zero retinomotor value shifted from the fovea to the ONH. We do not believe that there is any direct visual input from the ONH. The patient may use visual information obtained by glancing with peri-papillary areas to determine the target position (although this was largely ruled out), or obtain position information from the average luminance produced by scattered light around the ONH margin. The abnormal oculocentric direction might then be combined with extraretinal information (efferent copy or extraocular muscle proprioception) of the eye location in the orbit to stabilize the fixation. This patient does not have the blind spot syndrome (Swan, 1948). We propose the use of a retinal perimeter for documentation of eccentric fixation in strabismus.