Choroidalyzer: An Open-Source, End-to-End Pipeline for Choroidal Analysis in Optical Coherence Tomography.

Purpose: To develop Choroidalyzer, an open-source, end-to-end pipeline for segmenting the choroid region, vessels, and fovea, and deriving choroidal thickness, area, and vascular index. Methods: We used 5600 OCT B-scans (233 subjects, six systemic disease cohorts, three device types, two manufacturers). To generate region and vessel ground-truths, we used state-of-the-art automatic methods following manual correction of inaccurate segmentations, with foveal positions manually annotated. We trained a U-Net deep learning model to detect the region, vessels, and fovea to calculate choroid thickness, area, and vascular index in a fovea-centered region of interest. We analyzed segmentation agreement (AUC, Dice) and choroid metrics agreement (Pearson, Spearman, mean absolute error [MAE]) in internal and external test sets. We compared Choroidalyzer to two manual graders on a small subset of external test images and examined cases of high error. Results: Choroidalyzer took 0.299 seconds per image on a standard laptop and achieved excellent region (Dice: internal 0.9789, external 0.9749), very good vessel segmentation performance (Dice: internal 0.8817, external 0.8703), and excellent fovea location prediction (MAE: internal 3.9 pixels, external 3.4 pixels). For thickness, area, and vascular index, Pearson correlations were 0.9754, 0.9815, and 0.8285 (internal)/0.9831, 0.9779, 0.7948 (external), respectively (all P < 0.0001). Choroidalyzer's agreement with graders was comparable to the intergrader agreement across all metrics. Conclusions: Choroidalyzer is an open-source, end-to-end pipeline that accurately segments the choroid and reliably extracts thickness, area, and vascular index. Especially choroidal vessel segmentation is a difficult and subjective task, and fully automatic methods like Choroidalyzer could provide objectivity and standardization.

Myopia management algorithm. Annexe to the article titled Update and guidance on management of myopia. European Society of Ophthalmology in cooperation with International Myopia Institute.

Myopia is becoming increasingly common in young generations all over the world, and it is predicted to become the most common cause of blindness and visual impairment in later life in the near future. Because myopia can cause serious complications and vision loss, it is critical to create and prescribe effective myopia treatment solutions that can help prevent or delay the onset and progression of myopia. The scientific understanding of myopia's causes, genetic background, environmental conditions, and various management techniques, including therapies to prevent or postpone its development and slow its progression, is rapidly expanding. However, some significant information gaps exist on this subject, making it difficult to develop an effective intervention plan. As with the creation of this present algorithm, a compromise is to work on best practices and reach consensus among a wide number of specialists. The quick rise in information regarding myopia management may be difficult for the busy eye care provider, but it necessitates a continuing need to evaluate new research and implement it into daily practice. To assist eye care providers in developing these strategies, an algorithm has been proposed that covers all aspects of myopia mitigation and management. The algorithm aims to provide practical assistance in choosing and developing an effective myopia management strategy tailored to the individual child. It incorporates the latest research findings and covers a wide range of modalities, from primary, secondary, and tertiary myopia prevention to interventions that reduce the progression of myopia.

The effect of sustained eye rotation upon eye length in healthy myopic adults.

AIM: The aim of the study was to determine whether ocular movement can affect the shape of the globe and lead to measurable change in axial and peripheral eye length. METHODS: Ten subjects aged 18-30 years (6 M/4 F) participated with informed consent. The mean spherical equivalent refractive error was ≤-1.00 DS with cylindrical refraction <-1.25 DC. One drop of tropicamide hydrochloride 1% was instilled 20 min before measurement to induce mydriasis and mild cycloplegia. Using IOLMaster, eye length was measured centrally and temporally (25° off-axis) in four different positions. Subjects then rotated their eyes 25° in the temporal direction to fixate on a target for 10 min. After that, the same measurements were repeated. RESULTS: Before rotation, the group mean peripheral eye length was significantly shorter than the central eye length (P < 0.05). There was no significant variation in central or peripheral eye length due to off-axis fixation, either after the initial eye rotation or after fixation for 10 min at the off-axis point. The difference between central and peripheral eye lengths was maintained after 10 min of temporal fixation (P < 0.05). CONCLUSION: Peripheral eye length was shorter than central eye length showing the prolate shape associated with myopia. The action of the extraocular muscles on the globe has no significant effect upon the retinal shape assessed by off-axis eye length measurement in myopic subjects.

Choroidal thickness measurements in different ethnicities using swept source optical coherence tomography: repeatability and assessment.

CLINICAL RELEVANCE: Swept-source optical coherence tomography may not provide reliable measurements of choroidal thickness for pigmented subjects. BACKGROUND: The repeatability of choroidal thickness measurements in young healthy adults was investigated using swept source optical coherence tomography. METHODS: Choroidal thickness was measured using swept source optical coherence tomography in 98 healthy subjects (49 South Asian and 49 Caucasian) aged between 19 and 28 years old. Repeated radial scan images centred on the fovea were obtained from the right eye with 5 min between measurements. Choroidal thickness values were obtained from the built-in automated segmentation algorithm for the 9 subfields defined by the Early Treatment Diabetic Retinopathy Study. Interclass correlation coefficients and Bland-Altman methods were used to assess test-retest repeatability. RESULTS: The mean ± standard deviation sub-foveal choroidal thickness was 316.53 ± 63.36 µm for the Caucasian group and 292.70 ± 60.13 µm for the South Asian group. Bland-Altman analysis showed smaller test-retest variability for choroidal thickness measurements in the Caucasian group (mean difference ± SD = -0.01 ± 6.59 µm) compared to the South Asian group (mean difference ± SD = -2.38 ± 12.20 µm). No relationship was found between the mean choroidal thickness and mean spherical equivalent of refractive error for both subject groups. CONCLUSION: Swept source optical coherence tomography is capable of obtaining choroidal thickness measurements with good repeatability. However, test-retest limits of agreement are substantially greater in South Asian subjects, suggesting that successful identification of the choroidal scleral interface may be affected by the amount of pigmentation present in the retinal and choroidal tissues.

Update and guidance on management of myopia. European Society of Ophthalmology in cooperation with International Myopia Institute.

The prevalence of myopia is increasing extensively worldwide. The number of people with myopia in 2020 is predicted to be 2.6 billion globally, which is expected to rise up to 4.9 billion by 2050, unless preventive actions and interventions are taken. The number of individuals with high myopia is also increasing substantially and pathological myopia is predicted to become the most common cause of irreversible vision impairment and blindness worldwide and also in Europe. These prevalence estimates indicate the importance of reducing the burden of myopia by means of myopia control interventions to prevent myopia onset and to slow down myopia progression. Due to the urgency of the situation, the European Society of Ophthalmology decided to publish this update of the current information and guidance on management of myopia. The pathogenesis and genetics of myopia are also summarized and epidemiology, risk factors, preventive and treatment options are discussed in details.

Environmental and behavioural interventions for reducing physical activity limitation and preventing falls in older people with visual impairment.

BACKGROUND: Impairment of vision is associated with a decrease in activities of daily living. Avoidance of physical activity in older adults with visual impairment can lead to functional decline and is an important risk factor for falls. The rate of falls and fractures is higher in older people with visual impairment than in age-matched visually normal older people. Possible interventions to reduce activity restriction and prevent falls include environmental and behavioral interventions. OBJECTIVES: We aimed to assess the effectiveness and safety of environmental and behavioral interventions in reducing physical activity limitation, preventing falls and improving quality of life amongst visually impaired older people. SEARCH METHODS: We searched CENTRAL (including the Cochrane Eyes and Vision Trials Register) (Issue 2, 2020), Ovid MEDLINE, Embase and eight other databases to 4 February 2020, with no language restrictions. SELECTION CRITERIA: Eligible studies were randomized controlled trials (RCTs) and quasi-randomized controlled trials (Q-RCTs) that compared environmental interventions, behavioral interventions or both, versus control (usual care or no intervention); or that compared different types of environmental or behavioral interventions. Eligible study populations were older people (aged 60 and over) with irreversible visual impairment, living in their own homes or in residential settings. To be eligible for inclusion, studies must have included a measure of physical activity or falls, the two primary outcomes of interest. Secondary outcomes included fear of falling, and quality of life. DATA COLLECTION AND ANALYSIS: We used standard Cochrane methods. We assessed the certainty of the evidence using the GRADE approach. MAIN RESULTS: We included six RCTs (686 participants) conducted in five countries (Australia, Hungary, New Zealand, UK, US) with follow-up periods ranging from two to 12 months. Participants in these trials included older adults (mean age 80 years) and were mostly female (69%), with visual impairments of varying severity and underlying causes. Participants mostly lived in their homes and were physically independent. We classified all trials as having high risk of bias for masking of participants, and three trials as having high or unclear risk of bias for all other domains. The included trials evaluated various intervention strategies (e.g. an exercise program versus home safety modifications). Heterogeneity of study characteristics, including interventions and outcomes, (e.g. different fall measures), precluded any meta-analysis. Two trials compared the home safety modification by occupational therapists versus social/home visits. One trial (28 participants) reported physical activity at six months and showed no evidence of a difference in mean estimates between groups (step counts: mean difference (MD) = 321, 95% confidence interval (CI) -1981 to 2623; average walking time (minutes): MD 1.70, 95% CI -24.03 to 27.43; telephone questionnaire for self-reported physical activity: MD -3.68 scores, 95% CI -20.6 to 13.24; low-certainty of evidence for each outcome). Two trials reported the proportion of participants who fell at six months (risk ratio (RR) 0.76, 95% CI 0.38 to 1.51; 28 participants) and 12 months (RR 0.59, 95% CI 0.43 to 0.80, 196 participants) with low-certainty of evidence for each outcome. One trial (28 participants) reported fear of falling at six months, using the Short Falls Efficacy Scale-International, and found no evidence of a difference in mean estimates between groups (MD 2.55 scores, 95% CI -0.51 to 5.61; low-certainty of evidence). This trial also reported quality of life at six months using 12-Item Short Form Health Survey, and showed no evidence of a difference in mean estimates between groups (MD -3.14 scores, 95% CI -10.86 to 4.58; low-certainty of evidence). Five trials compared a behavioral intervention (exercise) versus usual activity or social/home visits. One trial (59 participants) assessed self-reported physical activity at six months and showed no evidence of a difference between groups (MD 9.10 scores, 95% CI -13.85 to 32.5; low-certainty of evidence). Three trials investigated different fall measures at six or 12 months, and found no evidence of a difference in effect estimates (RRs for proportion of fallers ranged from 0.54 (95% CI 0.29 to 1.01; 41 participants); to 0.93 (95% CI 0.61 to 1.39; 120 participants); low-certainty of evidence for each outcome). Three trials assessed the fear of falling using Short Falls Efficacy Scale-International or the Illinois Fear of Falling Measure from two to 12 months, and found no evidence of a difference in mean estimates between groups (the estimates ranged from -0.88 score (95% CI -2.72 to 0.96, 114 participants) to 1.00 score (95% CI -0.13 to 2.13; 59 participants); low-certainty of evidence). One trial (59 participants) assessed the European Quality of Life scale at six months (MD -0.15 score, 95% CI -0.29 to -0.01), and found no evidence of a clinical difference between groups (low-certainty of evidence). AUTHORS' CONCLUSIONS: There is no evidence of effect for most of the environmental or behavioral interventions studied for reducing physical activity limitation and preventing falls in visually impaired older people. The certainty of evidence is generally low due to poor methodological quality and heterogeneous outcome measurements. Researchers should form a consensus to adopt standard ways of measuring physical activity and falls reliably in older people with visual impairments. Fall prevention trials should plan to use objectively measured or self-reported physical activity as outcome measures of reduced activity limitation. Future research should evaluate the acceptability and applicability of interventions, and use validated questionnaires to assess the adherence to rehabilitative strategies and performance during activities of daily living.

Change in body height, axial length and refractive status over a four-year period in caucasian children and young adults.

INTRODUCTION: Body height and axial length (AL) increase during childhood with excessive axial elongation resulting in myopia. There is no consensus regarding the association between body growth and AL during refractive development. This study explored the association between change in body height, AL and refractive status over 4-years in children and young adults. MATERIAL AND METHODS: Measures were collected biennially (timepoints: t1, t2, t3) (t1 n = 140, aged 5-20years). Non-cycloplegic autorefraction was obtained using the Shin-Nippon openfield autorefractor. AL, corneal curvature (CC) and anterior chamber depth (ACD) were measured by IOL Master. Body height (cm) was measured using a wall mounted tape measure. Refractive status was classified using spherical equivalent refraction (SER): persistent emmetropes (PE) (-0.50D to +1.00D), persistent myopes (PM) (≤-0.50D), progressing myopes (PrM) (increase of ≤-0.50D between timepoints), incident myopes (IM) (subsequent SER≤-0.50D) and persistent hyperopes (PH) (>+1.00D). RESULTS: Change in AL and change in height were correlated in the PE (all t:p ≤ 0.003) and the IM (t1-t2 p = 0.04). For every increase in body height of 1 cm: t1-t2: AL increased by 0.03 mm in the PE, 0.15 in the PM, 0.11 mm in the IM, 0.14 mm in the PrM, -0.006 mm in the PH. T2-t3: AL increased by 0.02 mm in the PE, 0.06 in the PM, 0.16 mm in the PrM, 0.12 mm in the IM and -0.03 mm in the PH. CONCLUSIONS: In emmetropia body growth and axial elongation are correlated. In participants with myopia, body growth appears to stabilise whilst axial elongation continues at a much faster rate indicating dysregulation of normal ocular growth.

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.

Is Pupil Diameter Influenced by Refractive Error?

PURPOSE: To investigate the relationship between pupil diameter and refractive error and how refractive correction, target luminance, and accommodation modulate this relationship. METHODS: Sixty emmetropic, myopic, and hyperopic subjects (age range, 18 to 35 years) viewed an illuminated target (luminance: 10, 100, 200, 400, 1000, 2000, and 4100 cd/m) within a Badal optical system, at 0 diopters (D) and -3 D vergence, with and without refractive correction. Refractive error was corrected using daily disposable contact lenses. Pupil diameter and accommodation were recorded continuously using a commercially available photorefractor. RESULTS: No significant difference in pupil diameter was found between the refractive groups at 0 D or -3 D target vergence, in the corrected or uncorrected conditions. As expected, pupil diameter decreased with increasing luminance. Target vergence had no significant influence on pupil diameter. In the corrected condition, at 0 D target vergence, the accommodation response was similar in all refractive groups. At -3 D target vergence, the emmetropic and myopic groups accommodated significantly more than the hyperopic group at all luminance levels. There was no correlation between accommodation response and pupil diameter or refractive error in any refractive group. In the uncorrected condition, the accommodation response was significantly greater in the hyperopic group than in the myopic group at all luminance levels, particularly for near viewing. In the hyperopic group, the accommodation response was significantly correlated with refractive error but not pupil diameter. In the myopic group, accommodation response level was not correlated with refractive error or pupil diameter. CONCLUSIONS: Refractive error has no influence on pupil diameter, irrespective of refractive correction or accommodative demand. This suggests that the pupil is controlled by the pupillary light reflex and is not driven by retinal blur.

Quantifying interactions between accommodation and vergence in a binocularly normal population.

Stimulation of the accommodation system results in a response in the vergence system via accommodative vergence cross-link interactions, and stimulation of the vergence system results in an accommodation response via vergence accommodation cross-link interactions. Cross-link interactions are necessary in order to ensure simultaneous responses in the accommodation and vergence systems. The crosslink interactions are represented most comprehensively by the response AC/A (accommodative vergence) and CA/C (vergence accommodation) ratios, although the stimulus AC/A ratio is measured clinically, and the stimulus CA/C ratio is seldom measured in clinical practice. The present study aims to quantify both stimulus and response AC/A and CA/C ratios in a binocularly normal population, and determine the relationship between them. 25 Subjects (mean ± SD age 21.0 ± 1.9 years) were recruited from the university population. A significant linear relationship was found between the stimulus and response ratios, for both AC/A (r² = 0.96, p < 0.001) and CA/C ratios (r² = 0.40, p < 0.05). Good agreement was found between the stimulus and response AC/A ratios (95% CI -0.06 to 0.24 MA/D). Stimulus and response CA/C ratios are linearly related. Stimulus CA/C ratios were higher than response ratios at low values, and lower than response ratios at high values (95% CI -0.46 to 0.42 D/MA). Agreement between stimulus and response CA/C ratios is poorer than that found for AC/A ratios due to increased variability in vergence responses when viewing the Gaussian blurred target. This study has shown that more work is needed to refine the methodology of CA/C ratio measurement.

The effect of ocular rigidity upon the characteristics of saccadic eye movements.

PURPOSE: To determine whether variation in ocular rigidity (a quantity that describes the elastic properties of the globe) affects the characteristics of horizontal saccadic eye movements. METHODS: Thirty-three young, visually healthy subjects participated with informed consent in the study. Axial length was measured using the IOLMaster ocular biometer. Ocular rigidity coefficients were determined using Schiotz tonometry. Horizontal saccades were stimulated randomly to 40° in 10° steps. Eye movements were recorded continuously at a sampling rate of 60 Hz using the Viewpoint video-eyetracker. RESULTS: Peak velocity increased significantly with increasing ocular rigidity (F [2,263] = 30.635, P < 0.001). Time to peak velocity (F [2,263] = 27.723, P < 0.001) and total response time (F [2,263] = 21.133, P < 0.001) decreased significantly with increasing ocular rigidity. Ocular rigidity was significantly positively correlated with peak velocity (R(2) = 0.67, P < 0.001), and significantly negatively correlated with time to peak velocity (R(2) = 0.64, P < 0.001), and total response time (R(2) = 0.62, P < 0.001). CONCLUSIONS: The known relationship of ocular rigidity with myopia can be extended to shorter hyperopic eyes, which are found to have higher ocular rigidity. The dynamic characteristics of saccadic eye movements are found to vary systematically with ocular rigidity. These findings suggest that the structural characteristics of the eye are an important factor in determining dynamic characteristics of eye movements.

Changes in ocular monochromatic higher-order aberrations in the aging eye.

PURPOSE: To characterize corneal, internal, and total ocular monochromatic higher-order aberration (MHOA) changes that occur in the aging eye. METHODS: Prospective observational case series including 300 eyes of 167 patients (mean age = 63.8 years) attending the ophthalmology service at University Hospital Ayr, Scotland. Corneal, internal, and total ocular aberrations were measured over a 6-mm dilated pupil. Zernike coefficients were obtained to the sixth order. Changes in MHOA between age groups and inter-eye correlations between right and left eyes were analyzed. RESULTS: A significant inter-eye correlation was found for refractive mean spherical equivalent and cylinder. A significant inter-eye correlation for the whole eye, corneal, and internal MHOA was found (p < 0.001). Right eye analysis found a significant positive correlation between age and the root mean square of whole eye MHOA (p = 0.012), with an increase from 0.517 µm in the fifth decade to 0.824 µm in the ninth. Total internal MHOA increased from 0.411 to 0.704 µm. A significant positive correlation was found between age and internal fourth- (p = 0.007), fifth- (p = 0.029), and sixth-order (p = 0.025) root mean square aberrations. There were no significant age-related changes in corneal MHOA or corneal spherical aberration. Overall mean (SD) corneal SA was 0.203 (0.082) µm. CONCLUSIONS: A strong correlation between the right and left eyes exists for MHOA. Whole eye MHOA increases with age. Such changes can be attributed to age-related changes in the internal optical quality of the eye. Such normative data are useful to the cataract surgeon when considering the use of an aspherical IOL to counteract corneal-induced SA during cataract surgery.

Environmental and behavioural interventions for reducing physical activity limitation in community-dwelling visually impaired older people.

BACKGROUND: Impairment of vision is associated with a loss of function in activities of daily living. Avoidance of physical activity and consequent reduced functional capacity is common in older people with visual impairment and an important risk factor for falls. Indeed, the rate of falls and fractures is higher in older people with visual impairment than age-matched visually normal older people. Depression and anxiety is common in older people with vision impairment and leads to further restriction of activity, reduced social contact and reduced quality of life. Possible mechanisms to reduce activity restriction and therefore improve mobility and activity include environmental and behavioural interventions delivered by a number of health professionals, including occupational therapists. OBJECTIVES: The objective of this review was to assess the effectiveness of environmental and behavioural interventions in reducing activity limitation and improving quality of life amongst visually impaired older people. SEARCH METHODS: We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2012, Issue 10), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE, (January 1950 to November 2012), EMBASE (January 1980 to November 2012), Cumulative Index to Nursing and Allied Health Literature (CINAHL) (January 1937 to November 2012), Allied and Complementary Medicine Database (AMED) (January 1985 to November 2012), OT Seeker (inception to November 2012), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 9 November 2012. SELECTION CRITERIA: Randomised controlled trials (RCTs) and quasi-randomised controlled trials (Q-RCTs) that compared environmental interventions, behavioural interventions or both, versus control (placebo control or no intervention or usual care), and trials comparing different types of environmental or behavioural interventions, in older people (aged 60 and over) with irreversible visual impairment living independently or in residential settings. To be eligible for inclusion the primary aim of studies must be reducing physical activity limitation and must include a measure of physical activity. Secondary outcome measures included falls, fear of falling, quality of life. DATA COLLECTION AND ANALYSIS: Two authors independently read abstracts retrieved by the search to identify eligibility and study quality. We contacted study authors for additional information. MAIN RESULTS: Our searches found no RCTs or Q-RCTs that met the eligibility criteria for this review. AUTHORS' CONCLUSIONS: We are unable to reach any conclusion about the effectiveness of environmental or behavioural interventions for reducing physical activity limitation in community-dwelling visually impaired older people, as no eligible studies were found. However a number of studies reviewed included only the secondary outcome measures of this review. Although behavioural interventions delivered by occupational therapists have been shown to reduce the rate of falls, we are unable to conclude if this is due to reduced activity restriction (increased mobility) or reduced activity (lessening exposure to risk). There are inconclusive and conflicting results from trials evaluating the effectiveness of behavioural and environmental interventions aimed at improving quality of life. Further research is necessary (such as ongoing Dutch and UK trials considering the effectiveness of orientation and mobility training on activity restriction, physical activity, falls, fear of falling and quality of life in older adults with low vision, and the effect of an occupational therapist delivering home safety modification, coping strategies and exercise with older people with low vision) before any conclusions can be reached.

An exploratory study: prolonged periods of binocular stimulation can provide an effective treatment for childhood amblyopia.

PURPOSE: The purpose of the present study was to explore the potential for treating childhood amblyopia with a binocular stimulus designed to correlate the visual input from both eyes. METHODS: Eight strabismic, two anisometropic, and four strabismic and anisometropic amblyopes (mean age, 8.5 ± 2.6 years) undertook a dichoptic perceptual learning task for five sessions (each lasting 1 hour) over the course of a week. The training paradigm involved a simple computer game, which required the subject to use both eyes to perform the task. RESULTS: A statistically significant improvement (t(13) = 5.46; P = 0.0001) in the mean visual acuity (VA) of the amblyopic eye (AE) was demonstrated, from 0.51 ± 0.27 logMAR before training to 0.42 ± 0.28 logMAR after training with six subjects gaining 0.1 logMAR or more of improvement. Measurable stereofunction was established for the first time in three subjects with an overall significant mean improvement in stereoacuity after training (t(13) =2.64; P = 0.02). CONCLUSIONS: The dichoptic-based perceptual learning therapy employed in the present study improved both the monocular VA of the AE and stereofunction, verifying the feasibility of a binocular approach in the treatment of childhood amblyopia.

Accommodation steps, target spatial frequency and refractive error.

PURPOSE: Errors in the accommodation response of myopes have been reported in many studies although questions remain about the exact differences in accommodation steps when compared with emmetropic individuals. METHODS: The characteristics of the accommodation step response to large (4/1D) and small (3/2D) steps in targets with low (0.5 cpd), mid (4 cpd) and high (16 cpd) spatial frequency (SF) information was measured in myopes (MYOs) and emmetropes (EMMs). RESULTS: In terms of step size, the larger steps showed a greater response in the 4 cpd condition than the 0.5 and 16 cpd conditions and an improved percentage correct response in the 4 cpd compared to the 16 cpd steps. In small step conditions target SF had less effect upon the magnitude of the response. In terms of refractive group differences, MYOs had a lower proportion of correct accommodation responses compared to EMMs during the small steps only, however, when correct steps were performed there were no differences in the characteristics of both large and small step responses between MYOs and EMMs. CONCLUSIONS: These findings suggest that MYOs have some difficulty interpreting small changes in defocus to initiate or possibly fine tune a small accommodation response, however, when a correct accommodation step response is made, the MYOs accommodation plant responds in a similar manner to EMMs.

Investigating the mechanisms that may underlie the reduction in contrast sensitivity during dynamic accommodation.

Head and eye movements, together with ocular accommodation enable us to explore our visual environment. The stability of this environment is maintained during saccadic and vergence eye movements due to reduced contrast sensitivity to low spatial frequency information. Our recent work has revealed a new type of selective reduction of contrast sensitivity to high spatial frequency patterns during the fast phase of dynamic accommodation responses compared with steady-state accommodation. Here were report data which show a strong correlation between the effects of reduced contrast sensitivity during dynamic accommodation and velocity of accommodation responses, elicited by ramp changes in accommodative demand. The results were accounted for by a contrast gain control model of a cortical mechanism for contrast detection during dynamic ocular accommodation. Sensitivity, however, was not altered during attempted accommodation responses in the absence of crystalline-lens changes due to cycloplegia. These findings suggest that contrast sensitivity reduction during dynamic accommodation may be a consequence of cortical inhibition driven by proprioceptive-like signals originating within the ciliary muscle, rather than by corollary discharge signals elicited simultaneously with the motor command to the ciliary muscle.

The relationship between object spatial profile and accommodation microfluctuations in emmetropes and myopes.

The accommodation microfluctuations are thought to be used by the accommodation controller to obtain information about the direction and magnitude of the required response by monitoring changes in the contrast gradient of this image. The contrast gradient can be altered by presenting different spatial frequency (SF) targets to the eye. Twelve myopes (MYOs) and 12 emmetropes (EMMs) viewed sine and square wave targets of SF 0.5, 1, 2, 4, 8, 16 cpd in a Badal optical system. Accommodation responses were recorded continuously using the Shin-Nippon SRW-5000 autorefractor. There is no change in magnitude of the accommodation microfluctuations as the SF of square waves is altered. While viewing sine wave targets, the microfluctuations are smallest for mid (2, 4 cpd) SFs and increase for low (0.5 cpd) and high (16 cpd) SFs. MYOs show a significantly larger increase in the microfluctuations for the 16 cpd target compared to the EMMs. MYOs have significantly larger microfluctuations than the EMMs throughout. The microfluctuations seem to be monitoring the contrast gradient of the cortical image, which is likely to be used by the accommodation control system during error detection. The results indicate that MYO subjects may have a shallower contrast gradient and the potential reasons and implications of this are discussed.

The effect of modulating ocular depth of focus upon accommodation microfluctuations in myopic and emmetropic subjects.

The magnitude of accommodation microfluctuations increases in emmetropic subjects viewing low luminance targets or viewing a target through small artificial pupils. Larger microfluctuations reported in myopia may result from an abnormally large depth of focus (DoF). The effect of modulating the size of the DoF has not been investigated in myopic subjects and may help to explain the cause of the increased DoF. Accommodation microfluctuations were recorded under two experimental conditions. Firstly, 12 emmetropes (EMMs), and 24 myopes (MYOs) viewed a Maltese Cross target with luminance levels of 0.002, 0.2, 6 and 600cd/m(2) and in darkness, and second, 14 EMMs and 16 MYOs viewed a Maltese Cross target through pupil diameters of 0.5, 1, 2, 3, 4 and 5mm presented in Maxwellian view. The magnitude of the accommodation microfluctuations increased significantly with a target luminance of 0.002cd/m(2) (p<.03) and pinhole diameters of <2mm (p<.05). For all other luminance levels and pupil diameters the magnitude was constant. For both conditions, MYOs had significantly larger microfluctuations than EMMs (p<.01). Considerable inter-subject variability was observed in the degree to which the magnitude of the microfluctuations increased, for both the 0.002cd/m(2) luminance and 0.5mm pupils, however, this was not correlated with refractive error. The increase in the magnitude of the microfluctuations while viewing a low luminance target (0.002cd/m(2)) may be due to a shallower contrast gradient in the cortical image, with a consequent increase in DoF. The microfluctuations also increase when viewing through small pupils (<2mm), which increases the DoF without altering the contrast gradient. The larger microfluctuations found in the MYOs consolidates the theory that MYOs have a larger DoF than EMMs and therefore have a higher threshold for retinal image blur.