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Visual acuity (VA) screening in children primarily detects low VA and amblyopia between 3 and 6 years of age. Photoscreening is a low-cost, lower-expertise alternative which can be carried out on younger children and looks instead for refractive amblyopia risk factors so that early glasses may prevent or mitigate the conditions. The long-term benefits and costs of providing many children with glasses in an attempt to avoid development of amblyopia for some of them needs clarification. This paper presents a framework for modeling potential post-referral costs of different screening models once referred children reach specialist services. The EUSCREEN Screening Cost-Effectiveness Model was used together with published literature to estimate referral rates and case mix of referrals from different screening modalities (photoscreening and VA screening at 2, 3–4 years and 4–5 years). UK 2019–20 published National Health Service (NHS) costings were used across all scenarios to model the comparative post-referral costs to the point of discharge from specialist services. Potential costs were compared between a) orthoptist, b) state funded ophthalmologist and c) private ophthalmologist care. Earlier VA screening and photoscreening yield higher numbers of referrals because of lower sensitivity and specificity for disease, and a different case mix, compared to later VA screening. Photoscreening referrals are a mixture of reduced VA caused by amblyopia and refractive error, and children with amblyopia risk factors, most of which are treated with glasses. Costs relate mainly to the secondary care providers and the number of visits per child. Treatment by an ophthalmologist of a referral at 2 years of age can be more than x10 more expensive than an orthoptist service receiving referrals at 5 years, but outcomes can still be good from referrals aged 5. All children should be screened for amblyopia and low vision before the age of 6. Very early detection of amblyopia refractive risk factors may prevent or mitigate amblyopia for some affected children, but population-level outcomes from a single high-quality VA screening at 4–5 years can also be very good. Total patient-journey costs incurred by earlier detection and treatment are much higher than if screening is carried out later because younger children need more professional input before discharge, so early screening is less cost-effective in the long term. Population coverage, local healthcare models, local case-mix, public health awareness, training, data monitoring and audit are critical factors to consider when planning, evaluating, or changing any screening programme. [ABSTRACT FROM AUTHOR]

Objective: For cost-effectiveness comparison of child vision and hearing screening programmes, methods and data should be available. We assessed the current state of data collection and its availability in Europe. Methods: The EUSCREEN Questionnaire, conducted in 2017–2018, assessed paediatric vision and hearing screening programmes in 45 countries in Europe. For the current study, its items on data collection, monitoring and evaluation, and six of eleven items essential for cost-effectiveness analysis: prevalence, sensitivity, specificity, coverage, attendance and loss to follow-up, were reappraised with an additional questionnaire. Results: The practice of data collection in vision screening was reported in 36% (N = 42) of countries and in hearing screening in 81% (N = 43); collected data were published in 12% and 35%, respectively. Procedures for quality assurance in vision screening were reported in 19% and in hearing screening in 26%, research of screening effectiveness in 43% and 47%, whereas cost-effectiveness analysis was performed in 12% for both. Data on prevalence of amblyopia were reported in 40% and of hearing loss in 77%, on sensitivity of screening tests in 17% and 14%, on their specificity in 19% and 21%, on coverage of screening in 40% and 84%, on attendance in 21% and 37%, and on loss to follow-up in 12% and 40%, respectively. Conclusions: Data collection is insufficient in hearing screening and even more so in vision screening: data essential for cost-effectiveness comparison could not be reported from most countries. When collection takes place, this is mostly at a local level for quality assurance or accountability, and data are often not accessible. The resulting inability to compare cost-effectiveness among screening programmes perpetuates their diversity and inefficiency. [ABSTRACT FROM AUTHOR]

Accommodation anomalies are frequently caused or exacerbated by psychological problems such as anxiety. Patients share many features with those with other anxiety based somatic symptoms such as stomach-ache, palpitations and headaches. They can be difficult to treat, and the ophthalmic literature rarely goes beyond diagnosis and ocular treatment. This study reports characteristics and outcomes of a short case series of patients with accommodation spasms and weaknesses assessed objectively, and outlines a psychological approach to treatment 23 patients (13 severe accommodative weakness or "paralysis," 10 accommodative spasm) aged between 8–30 years, were referred to our laboratory after diagnosis by their referring clinician and exclusion of pathology or drug-related causes. Their accommodation and convergence were assessed objectively with a laboratory photorefractive method, as well as by conventional orthoptic testing and dynamic retinoscopy. All interactions with the patients used an evidence-based psychological approach, to give them insight into how stress and anxiety can cause or exacerbate eye symptoms and help them to break a vicious cycle of anxiety and risk of deterioration. 83% were female and 57% had previously diagnosed anxiety or dyslexia (with many more acknowledging being "worriers"). Inconsistency of responses was the rule and all showed normal responses at some time during their visit. Responses were poorly related to the visual stimuli presented and objective responses often differed from subjective. Dissociation between convergence and accommodation was more common, compared to our large, previously reported, control groups. No participant had true paralysis of accommodation. Responses often improved dramatically within one session after discussion and explanation of the strong relationship between anxiety and accommodative anomalies. None have returned for further advice or treatment. Our approach explicitly addresses psychological factors in causing, or worsening, accommodation (and co-existing convergence) anomalies. Many of these patients do not realize that a certain amount of blur is normal in everyday life. Ocular symptoms are often a sign of anxiety, not the primary problem. By recognizing this, patients can be helped to address the triggering issues and symptoms often subside or resolve spontaneously. Well-meaning professionals, offering only ocular treatments, can deflect attention away from the real cause and can unwittingly be making things worse. [ABSTRACT FROM AUTHOR]

Purpose: To describe and compare vision screening programmes and identify variance in number and type of tests used, timing of screening, personnel involved, monitoring and funding to be used as data for optimising, disinvesting or implementing future screening programmes. Methods: A questionnaire consisting of nine domains: demography & epidemiology, administration & general background, existing screening, coverage & attendance, tests, follow-up & diagnosis, treatment, cost & benefit and adverse effects was completed by Country Representatives (CRs) recruited from 47 countries. Results: The questionnaire was sufficiently completed for 46 Countries: 42 European countries, China, India, Malawi and Rwanda. Variation of provision was found in; age of screening (0-17 years), tests included (23), types of visual acuity (VA) test used (35 different optotypes), personnel (13), number of screens per child (median 5, range 1-32), and times VA tested (median 3, range 1-30). Infant screening is offered in all countries, whereas childhood vision screening is offered at least once in all countries, but not all regions of each country. All 46 countries provide vision screening between the ages of 3-7 years. Data on screening outcomes for quality assurance was not available from most countries; complete evaluation data was available in 2% of countries, partial data from 43%. Conclusion: Vision screening is highly variable. Some form of VA testing is being undertaken during childhood. Data collection and sharing should be improved to facilitate comparison and to be able to optimise vision screening programmes between regions and countries. [ABSTRACT FROM AUTHOR]

Background: In 2018 and 2019, paediatric vision screening was implemented in Cluj County, Romania, where universal paediatric vision screening does not yet exist. We report on the preparation and the first year of implementation. Methods: Objectives, target population and screening protocol were defined. In cities, children were screened by kindergarten nurses. In rural areas, kindergartens have no nurses and children were screened by family doctors' nurses, initially at the doctors' offices, later also in rural kindergartens. CME-accredited training courses and treatment pathways were organised. Implementation was assessed through on-site observations, interviews, questionnaires and analysis of screening results of referred children. Results: Out of 12,795 eligible four- and five-year-old children, 7,876 were screened in 2018. In the cities, kindergarten nurses screened most children without difficulties. In Cluj-Napoca 1.62x the average annual birth rate was screened and in the small cities 1.64x. In the rural areas, however, nurses of family doctors screened only 0.49x the birth rate. In 51 out of 75 rural communes, no screening took place in the first year. Of 118 rural family doctors' nurses, 51 had followed the course and 26 screened children. They screened only 41 children per nurse, on average, as compared to 80 in the small cities and 100 in Cluj-Napoca. Screening at rural kindergartens met with limited success. These are attended by few children because of low population density, parents working abroad or children being kept at home in case of bad weather and road conditions. Conclusions: Three times fewer children were screened in rural areas as compared to urban areas. Kindergartens in rural areas are too small to employ nurses and family doctors' nurses do not have easy access to many children and have competing healthcare priorities: there are 1.5x as many family doctors in urban areas as compared to rural areas. For nationwide scaling-up of vision screening, nurses should be enabled to screen a sufficient number of children in rural areas. [ABSTRACT FROM AUTHOR]

Cost effectiveness of different visual screening modalities cannot be calculated without long-term outcome data. This paper reports detailed outcomes from a gold-standard UK recommended orthoptist-delivered screening (ODS) at 4–5 years in school, compared to a neighboring school-nurse delivered screening (SNDS), both feeding into the same treatment pathway. The target condition was reduced visual acuity (VA) of worse than logMAR 0.2 in either eye. Available records from screening databases and hospital records were analyzed, comparing the two services wherever possible. More screening data was available from the ODS. ODS: 5706 screened, 3.5% referred. False positives 6.5%, PPV 91.4%, sensitivity 97.9%, and specificity 99.8% for reduced VA. Cost per child with reduced vision detected £195.22, and per amblyope detected £683.28. The mean treatment cost per child with reduced VA was £331.68 and for amblyopia treatment was £458.65. SNDS: 5630 screened and 3.8% referred (plus some referrals to local optometrists lost to follow up). False positives 34%, PPV 53.2%, sensitivity and specificity estimated as 89.3% and 98.67%. Costs to secondary services of false positives were seven times greater. The cost per child with confirmed reduced vision seen at the hospital was 46% more; and per amblyope detected was 39% more. Outcomes for treatment post referral in both groups were similar and excellent. 86% of genuine referrals improved to within normal limits with glasses alone. Of 221 genuine referrals with final outcome data, all now have better than 0.2logMAR acuity in the better eye and only two (0.9%) have residual amblyopia in one eye worse than 0.4logMAR. About 14–18% of children with reduced VA would have passed AAPOS photoscreening referral criteria. An orthoptist-delivered single VA screen at 4–5 years is highly cost effective with good outcomes. The main contributing factors to success appear to be training and experience in accurate VA testing, the opportunity to rescreen equivocal results, and monitoring, audit, and feedback of outcomes. [ABSTRACT FROM AUTHOR]

Purpose: Photoscreening assesses risk factors for amblyopia, as an alternative to measurement of visual acuity (VA) to detect amblyopia, on the premise that its early correction could prevent development of amblyopia. We studied implementations of Plusoptix photoscreening in existing population‐based screening in Flanders and Iran. Methods: In Flanders, VA is measured at age 3, 4 and 6, photoscreening was added to existing screening at age 1 and 2.5 years in 2013. In Iran, VA is measured at ages 3–6 years, photoscreening was added at ages 3–6 years between 2011 and 2016. Plusoptix use was analysed in the literature for detection of risk factors for amblyopia and amblyopia itself, for ages 0–3 and for 4–6. A questionnaire, containing seven domains: existing vision screening, addition of photoscreening, implementation in screening program, training, attendance, diagnosis and treatment, and costs was distributed. In Iran, screening procedures were observed on site. Results: Implementation of Plusoptix photoscreening was mainly analysed from questionnaires and interviews, its effectiveness from literature data. In Flanders, of 56 759 children photoscreened at age one (81% of children born in 2013), 9.2% had been referred, 13% of these were treated, mostly with glasses, resulting in an increase of 4‐year‐old children wearing glasses from 4.7% to 6.4%. In Iran, 90% of children aged 3–6 years participated in vision screening in 2016, but only those who failed the vision test were subjected to photoscreening. Conclusions: In Flanders, the use of Plusoptix photoscreening at ages 1 and 2.5 resulted in an increase of children wearing glasses, but it remains unknown how many cases of amblyopia have been prevented. Studies are needed to determine the relation between size and sort of refractive error and strabismus, and the increased chance to develop amblyopia. [ABSTRACT FROM AUTHOR]

Background/aims To investigate the presence of asymmetrical accommodation in hyperopic anisometropic amblyopia. Methods Accommodation in each eye and binocular vergence were measured simultaneously using a PlusoptiX SO4 photorefractor in 26 children aged 4-8 years with hyperopic anisometropic amblyopia and 13 controls (group age-matched) while they viewed a detailed target moving in depth. Results Without spectacles, only 5 (19%) anisometropes demonstrated symmetrical accommodation (within the 95% CI of the mean gain of the sound eye of the anisometropic group), whereas 21 (81%) demonstrated asymmetrical accommodation. Of those, 15 (58%) showed aniso-accommodation and 6 (23%) demonstrated 'anti-accommodation' (greater accommodation for distance than for near). In those with anti-accommodation, the response gain in the sound eye was (0.93±0.20) while that of the amblyopic eye showed a negative accommodation gain of (-0.44±0.23). Anti-accommodation resolved with spectacles. Vergence gains were typical in those with symmetrical and asymmetrical accommodation. Conclusion The majority of hyperopic anisometropic amblyopes demonstrated non-consensual asymmetrical accommodation. Approximately one in four demonstrated anti-accommodation. [ABSTRACT FROM AUTHOR]

Aims: To validate the content of an updated orthoptic curriculum for the British & Irish Orthoptic Society (BIOS), BIOS members were surveyed about their views on what an orthoptist should be able to do soon after entering the profession. Methods: An online survey of all practicing members of BIOS was carried out. In 35 questions across 5 domains (professional behaviour, foundation knowledge and theory, investigation, management and research and literature skills) covering the range of orthoptic practice, orthoptists were asked about the breadth and depth of knowledge required. Results were analysed by the respondents' working environment, experience, geographical region and teaching involvement. Results: 325 orthoptists (27% of the membership) provided useable data, and 265 provided a full dataset. Orthoptists are frequently required to exercise considerable autonomy and responsibility for patient care from very early in their careers across many domains, often in the least-supervised environments. There was broad agreement across most core topics but wider variation in opinion in more peripheral domains. More experienced orthoptists value the wider medical aspects of orthoptic practice more highly. Conclusions: The survey confirmed that there is generally a good match between current undergraduate teaching and clinicians' expectations of newly graduated orthoptists. It is clear that training must prepare graduates for a high level of professional autonomy from the earliest stages of their careers. There may be a place for targeting CPD provision for professionals at different stages in their careers. [ABSTRACT FROM AUTHOR]

The theme of the 2016 Burian Lecture is how our understanding of strabismus has been changed by the research carried out in our laboratory in Reading over the years. Accommodation and convergence are fundamental to orthoptics, but actual responses have often been very different compared to what we had expected. This paper outlines how our laboratory’s understanding of common issues such as normal development of accommodation and convergence, their linkage, intermittent strabismus, anisometropia, orthoptic exercises, and risk factors for strabismus have changed. A new model of thinking about convergence and accommodation may help us to better understand and predict responses in our patients. [ABSTRACT FROM PUBLISHER]

Aim This paper presents Convergence Insufficiency Symptom Survey (CISS) and orthoptic findings in a sample of typical young adults who considered themselves to have normal eyesight apart from weak spectacles. Methods The CISS questionnaire was administered, followed by a full orthoptic evaluation, to 167 university undergraduate and postgraduate students during the recruitment phase of another study. The primary criterion for recruitment to this study was that participants 'felt they had normal eyesight'. A CISS score of =21 was used to define 'significant' symptoms, and convergence insufficiency (CI) was defined as convergence =8 cm from the nose with a fusion range <15? base-out with small or no exophoria. Results The group mean CISS score was 15.4. In all, 17 (10%) of the participants were diagnosed with CI, but 11 (65%) of these did not have significant symptoms. 41 (25%) participants returned a 'high' CISS score of =21 but only 6 (15%) of these had genuine CI. Sensitivity of the CISS to detect CI in this asymptomatic sample was 38%; specificity 77%; positive predictive value 15%; and negative predictive value 92%. The area under a receiver operating characteristic curve was 0.596 (95% CI 0.46 to 0.73). Conclusions 'Visual symptoms' are common in young adults, but often not related to any clinical defect, while true CI may be asymptomatic. This study suggests that screening for CI is not indicated. [ABSTRACT FROM AUTHOR]

Purpose The relative efficiency of different eye exercise regimes is unclear, and in particular the influences of practice, placebo and the amount of effort required are rarely considered. This study measured conventional clinical measures following different regimes in typical young adults. Methods A total of 156 asymptomatic young adults were directed to carry out eye exercises three times daily for 2 weeks. Exercises were directed at improving blur responses (accommodation), disparity responses (convergence), both in a naturalistic relationship, convergence in excess of accommodation, accommodation in excess of convergence, and a placebo regime. They were compared to two control groups, neither of which were given exercises, but the second of which were asked to make maximum effort during the second testing. Results Instruction set and participant effort were more effective than many exercises. Convergence exercises independent of accommodation were the most effective treatment, followed by accommodation exercises, and both regimes resulted in changes in both vergence and accommodation test responses. Exercises targeting convergence and accommodation working together were less effective than those where they were separated. Accommodation measures were prone to large instruction/effort effects and monocular accommodation facility was subject to large practice effects. Conclusions Separating convergence and accommodation exercises seemed more effective than exercising both systems concurrently and suggests that stimulation of accommodation and convergence may act in an additive fashion to aid responses. Instruction/effort effects are large and should be carefully controlled if claims for the efficacy of any exercise regime are to be made. [ABSTRACT FROM AUTHOR]

Aim: To describe preliminary findings of how the profile of the use of blur, disparity, and proximal cues varies between non-strabismic groups and those with different types of esotropia. Design: This was a case control study. Methodology: A remote haploscopic photorefractor measured simultaneous convergence and accommodation to a range of targets containing all combinations of binocular disparity, blur, and proximal (looming) cues. Thirteen constant esotropes, 16 fully accommodative esotropes, and 8 convergence excess esotropes were compared with age- and refractive error-matched controls and 27 young adult emmetropic controls. All wore full refractive correction if not emmetropic. Response AC/A and CA/C ratios were also assessed. Results: Cue use differed between the groups. Even esotropes with constant suppression and no binocular vision (BV) responded to disparity in cues. The constant esotropes with weak BV showed trends for more stable responses and better vergence and accommodation than those without any BV. The accommodative esotropes made less use of disparity cues to drive accommodation ( p = 0.04) and more use of blur to drive vergence ( p = 0.008) than controls. All esotropic groups failed to show the strong bias for better responses to disparity cues found in the controls, with convergence excess esotropes favoring blur cues. AC/A and CA/C ratios existed in an inverse relationship in the different groups. Accommodative lag of >1.0 D at 33 cm was common (46%) in the pooled esotropia groups compared with 11% in typical children ( p = 0.05). Conclusion: Esotropic children use near cues differently from matched non-esotropic children in ways characteristic to their deviations. Relatively higher weighting for blur cues was found in accommodative esotropia compared to matched controls. [ABSTRACT FROM AUTHOR]

Accurate coordination of accommodation and convergence is necessary to view near objects and develop fine motor coordination. We used a remote haploscopic videorefraction paradigm to measure longitudinal changes in simultaneous ocular accommodation and vergence to targets at different depths, and to all combinations of blur, binocular disparity, and change-in-size (‘proximity’) cues. Infants were followed longitudinally and compared with older children and young adults, with the prediction that sensitivity to different cues would change during development. Mean infant responses to the most naturalistic condition were similar to those of adults from 6–7 weeks (accommodation) and 8–9 weeks (vergence). Proximity cues influenced responses most in infants of less than 14 weeks of age, but sensitivity declined thereafter. Between 12 and 28 weeks of age infants were equally responsive to all three cues, while in older children and adults manipulation of disparity resulted in the greatest changes in response. Despite rapid development of visual acuity (thus increasing availability of blur cues), responses to blur were stable throughout development. Our results suggest that, during much of infancy, vergence and accommodation responses are not dependent on the development of specific depth cues, but make use of any cues available to drive appropriate changes in response. [ABSTRACT FROM AUTHOR]

Aim: To provide evidence that a near clinical gradient AC/A ratio could instead reflect the CA/C relationship (the accommodation driven by response to disparity). Design: Case control study. Methodology: 27 emmetropic participants with heterophoria <4 PD, 19 with intermittent distance exotropia, and 17 with near exophoria >6 PD were tested. A remote haploscopic photorefractor, which can measure simultaneous convergence and accommodation to a range of targets containing all combinations of presence or absence of binocular disparity, blur, and proximal (looming) cues, was used to assess response AC/A and CA/C relationships. These were compared with clinical gradient AC/A ratios at near and distance fixation using alternate prism cover test and plus or minus lenses. Results: Although the near and distance clinical AC/A ratios correlated weakly with each other ( p = 0.03), neither clinical method correlated with the more accurate response AC/A ratio from the laboratory method ( p = 0.88 and p = 0.93, respectively). The laboratory CA/C ratio correlated strongly with the near clinical AC/A ratio ( p = 0.004) but only very weakly with the distance ratio ( p = 0.16). Conclusions: The 'near gradient AC/A ratio' may actually reflect the CA/C linkage as the dissociation of the prism cover test disrupts vergence accommodation. If the near deviation diverges more with plus lenses, it may be because the lenses allow clear near vision without needing to recruit convergence accommodation to achieve it. [ABSTRACT FROM AUTHOR]

Objective Disparity cues can be a major drive to accommodation via the convergence accommodation to convergence (CA/C) linkage, but, on decompensation of exotropia, disparity cues are extinguished by suppression so this drive is lost. This study investigated accommodation and vergence responses to disparity, blur and proximal cues in a group of distance exotropes aged between 4 and 11 years both during decompensation and when exotropic. Methods 19 participants with distance exotropia were tested using a PlusoptiXSO4 photo refractor set in a remote haploscopic device that assessed simultaneous vergence and accommodation to a range of targets incorporating different combinations of blur, disparity and proximal cues at four fixation distances between 2 m and 33 cm. Responses on decompensation were compared with those from the same children when their deviation was controlled. Results Manifest exotropia was more common in the more impoverished cue conditions. When decompensated for near, mean accommodation gain for the all-cue (naturalistic) target was significantly reduced (p<0.0001), with resultant mean under-accommodation of 2.33 D at 33 cm. The profile of near cues usage changed after decompensation, with blur and proximity driving residual responses, but these remaining cues did not compensate for loss of accommodation caused by the removal of disparity. Conclusions Accommodation often reduces on decompensation of distance exotropia as the drive from convergence is extinguished, providing a further reason to try to prevent decompensation for near. [ABSTRACT FROM AUTHOR]

Purpose: Vergence and accommodation studies often use adult participants with experience of vision science. Reports of infant and clinical responses are generally more variable and of lower gain, with the implication that differences lie in immaturity or sub-optimal clinical characteristics but expert/naïve differences are rarely considered or quantified. Methods: Sixteen undergraduates, naïve to vision science, were individually matched by age, visual acuity, refractive error, heterophoria, stereoacuity and near point of accommodation to second- and third-year orthoptics and optometry undergraduates (‘experts’). Accommodation and vergence responses were assessed to targets moving between 33 cm, 50 cm, 1 m and 2 m using a haploscopic device incorporating a PlusoptiX SO4 autorefractor. Disparity, blur and looming cues were separately available or minimised in all combinations. Instruction set was minimal. Results: In all cases, vergence and accommodation response slopes (gain) were steeper and closer to 1.0 in the expert group ( p = 0.001), with the largest expert/naïve differences for both vergence and accommodation being for near targets ( p = 0.012). For vergence, the differences between expert and naïve response slopes increased with increasingly open-loop targets (linear trend p = 0.025). Although we predicted that proximal cues would drive additional response in the experts, the proximity-only cue was the only condition that showed no statistical effect of experience. Conclusions: Expert observers provide more accurate responses to near target demand than closely matched naïve observers. We suggest that attention, practice, voluntary and proprioceptive effects may enhance responses in experienced participants when compared to a more typical general population. Differences between adult reports and the developmental and clinical literature may partially reflect expert/naïve effects, as well as developmental change. If developmental and clinical studies are to be compared to adult normative data, uninstructed naïve adult data should be used. [ABSTRACT FROM AUTHOR]

Binocular disparity, blur, and proximal cues drive convergence and accommodation. Disparity is considered to be the main vergence cue and blur the main accommodation cue. We have developed a remote haploscopic photorefractor to measure simultaneous vergence and accommodation objectively in a wide range of participants of all ages while fixating targets at between 0.3 and 2 m. By separating the three main near cues, we can explore their relative weighting in three-, two-, one-, and zero-cue conditions. Disparity can be manipulated by remote occlusion; blur cues manipulated by using either a Gabor patch or a detailed picture target; looming cues by either scaling or not scaling target size with distance. In normal orthophoric, emmetropic, symptom-free, naive visually mature participants, disparity was by far the most significant cue to both vergence and accommodation. Accommodation responses dropped dramatically if disparity was not available. Blur only had a clinically significant effect when disparity was absent. Proximity had very little effect. There was considerable interparticipant variation. We predict that relative weighting of near cue use is likely to vary between clinical groups and present some individual cases as examples. We are using this naturalistic tool to research strabismus, vergence and accommodation development, and emmetropization. [ABSTRACT FROM AUTHOR]

A remote haploscopic photorefractor was used to assess objective binocular vergence and accommodation responses in 157 full-term healthy infants aged 1–6 months while fixating a brightly coloured target moving between fixation distances at 2, 1, 0.5 and 0.33 m. Vergence and accommodation response gain matured rapidly from ‘flat’ neonatal responses at an intercept of approximately 2 dioptres (D) for accommodation and 2.5 metre angles(MA) for vergence, reaching adult-like values at 4 months. Vergence gain was marginally higher in females ( p = 0.064), but accommodation gain ( p = 0.034) was higher and accommodative intercept closer to zero ( p = 0.004) in males in the first 3 months as they relaxed accommodation more appropriately for distant targets. More females showed flat accommodation responses ( p = 0.029). More males behaved hypermetropically in the first two months of life, but when these hypermetropic infants were excluded from the analysis, the gender difference remained. Gender differences disappeared after three months. Data showed variable responses and infants could behave appropriately and simultaneously on both, neither or only one measure at all ages. If accommodation was appropriate (gain between 0.7 and 1.3; r2 > 0.7) but vergence was not, males over- and under-converged equally, while the females who accommodated appropriately were more likely to overconverge ( p = 0.008). The apparent earlier maturity of the male accommodative responses may be due to refractive error differences but could also reflect gender-specific male preference for blur cues while females show earlier preference for disparity, which may underpin the earlier emerging, disparity dependent, stereopsis and full vergence found in females in other studies. [ABSTRACT FROM AUTHOR]

. Purpose: This study considered whether vergence drives accommodation or accommodation drives vergence during the control of distance exotropia for near fixation. High accommodative convergence to accommodation (AC/A) ratios are often used to explain this control, but the role of convergence to drive accommodation (the CA/C relationship) is rarely considered. Atypical CA/C characteristics could equally, or better, explain common clinical findings. Methods: Nineteen distance exotropes, aged 4-11 years, were compared while controlling their deviation with 27 non-exotropic controls aged 5-9 years. Simultaneous vergence and accommodation responses were measured to a range of targets incorporating different combinations of blur, disparity and looming cues at four fixation distances between 2 m and 33 cm. Stimulus and response AC/A and CA/C ratios were calculated. Results: Accommodation responses for near targets (p = 0.017) and response gains (p = 0.026) were greater in the exotropes than in the controls. Despite higher clinical stimulus AC/A ratios, the distance exotropes showed lower laboratory response AC/A ratios (p = 0.02), but significantly higher CA/C ratios (p = 0.02). All the exotropes, whether the angle changed most with lenses ('controlled by accommodation') or on occlusion ('controlled by fusion'), used binocular disparity not blur as their main cue to target distance. Conclusions: Increased vergence demand to control intermittent distance exotropia for near also drives significantly more accommodation. Minus lens therapy is more likely to act by correcting overaccommodation driven by controlling convergence, rather than by inducing blur-driven vergence. The use of convergence as a major drive to accommodation explains many clinical characteristics of distance exotropia, including apparently high near stimulus AC/A ratios. [ABSTRACT FROM AUTHOR]