Critical Sensory Chronology of ASD

Neuroscience · Autism · Paediatric Ophthalmology

Ophthalmological integration, cortical plasticity and stratification of phenotypic expression in ASD

Critical Sensory Chronology (CSC) is an integrative synthesis an argumentative position paper, not a primary study producing new data. It connects five established axes of literature: massive ophthalmological prevalence in ASD, critical windows of cortical plasticity, the electroretinographic retinal signature, the US sociodemographic gradient, and an international health-system comparison. The central hypothesis: the support level required in adulthood (DSM-5 Level 1, 2, or 3) is not a neurobiological invariant fixed at birth. It is compatible with a cascade model in which the quality of the visual receptor apparatus plays the role of the first sensory domino.

This thesis does not argue that autism is caused by a vision defect, nor that early ophthalmological correction would cure it. It advances a more precise claim: the phenotypic severity expressed in adulthood is partially modifiable by early sensory intervention, and international statistics on stratified prevalence correlate with the organisation of paediatric visual screening systems. The framework satisfies six of the nine Bradford-Hill criteria, two partially, and defines four operational refutation conditions.

Chapter 2. Scientific Positioning and Central Hypothesis

CSC's epistemological position is that of a position paper or argumentative narrative review. It differs from a strict systematic review which constrains itself to a single question, a pre-registered protocol, and measurable documentary exhaustiveness and from an original research article which produces primary data. This intermediate status conditions its evidentiary claims: no strong causal conclusion is asserted. Conclusions belong either to the level of convergent empirical findings (level 1) or to the internal theoretical model (level 2). This model is proposed as a partial explanatory framework lending itself to empirical refutation under explicitly defined conditions.

The central hypothesis can be stated as follows: in the absence of early effective visual correction (before the closure of binocular plasticity windows, i.e., before 24 months for cortical fusion and stereopsis), the brain of the autistic child is deprived of part of the sensory substrate necessary for the construction of cognitive and behavioural compensation strategies particularly masking, mimicry, and joint attention which are the pathways through which a biologically Level 2 or 3 profile can present clinically as Level 1 in adolescence and adulthood.

Chapter 3. The Ophthalmic Infrastructure of the Atypical Brain

The neurodevelopmental literature suffers from a neurocentric bias: it attributes all perceptual alterations to higher cortical processing anomalies while overlooking dysfunction of the receptor organ itself. Consolidated quantitative data compel a paradigm shift: the eye of the neuroatypical infant is, from the starting line, structurally deficient. Strabismus affects 10.4% of autistic children versus 2.4% in controls (Chang 2020, n = 10 million), and the Perna meta-analysis (2023, 49 studies, 15.6 million individuals) establishes an odds ratio of 4.72 for strabismus in ASD. Astigmatism reaches 26% in ASD cohorts versus 8% in the general paediatric population.

The fusion of two monocular images into a single three-dimensional percept (stereopsis) requires perfect micro-motor alignment of the visual axes. The collapse of this function produces two direct neurobiological consequences. First, cortical suppression: to avoid diplopia induced by strabismus or anisometropia, the primary visual cortex actively suppresses the signal from the weaker eye, locking the individual into a two-dimensional visual world. Second, disruption of the fine motor loop: Lin et al. (2022) demonstrate that amblyopia robustly predicts subsequent ADHD development (aOR 1.69; 95% CI 1.44-1.97), underscoring the interdependence between binocular vision and attentional regulation.

The predictive coding framework applied to autism provides the neurocomputational mediation mechanism. The Pellicano-Burr (2012) framework developed independently through a distinct clinical-cognitive reasoning pathway proposes that the autistic brain allocates excessive weight to prediction errors between expected and received signals. A visual afferent signal degraded by uncorrected strabismus, a chronic accommodative deficit, or undetected aniseikonia generates a continuous stream of unresolved low-level prediction errors. For an autistic brain that over-weights these errors, this constitutes a chronic allostatic overload absorbing the cognitive resources needed for higher-order social processing.

Critical window of binocular plasticity: probability of stereopsis recovery by age at surgery (Birch 2009). The "24-Month Wall" marks the population-level statistical inflection.

Chapter 4. The 24-Month Wall - Phase 1 (Binocularity)

The 24-Month Wall designates a population-level statistical inflection point in the binocular recovery function, and not an absolute individual biological wall. Birch et al. (2009, J AAPOS) document a functional discontinuity in the probability of binocular stereopsis recovery after paediatric surgery: 77% if surgery occurs at 8 months or less, 20% between 9 and 24 months, 13% beyond 24 months. This curve constitutes the founding empirical datum for the Phase 1 concept. The discontinuity at 24 months is not a measurement artefact: it has been replicated in several independent cohorts and correlates with the molecular closure of critical windows of visual cortical plasticity documented by Hensch (2005) in the animal model.

The closure of binocular plasticity at 24 months rests on two concurrent molecular mechanisms: the increase in mature GABAergic inhibition and the maturation of perineuronal nets that stabilise synaptic connections around parvalbumin interneurons. This stabilisation, adaptive in that it solidifies acquired wiring, is also definitively constraining: ocular columns unused before 24 months reorganise only partially afterwards, at the cost of a permanent neurological compensatory burden. This mechanism, described initially in animals by Hubel and Wiesel and characterised molecularly by Hensch, applies at the human scale with substantially longer windows but a statistically robust discontinuity.

Stereoscopic debt gauge: early correction (before 24M) keeps debt low; late correction (after 24M) accumulates partial but incomplete debt; no correction perpetuates maximal debt.

Chapter 5. The Acuity Window - Phase 2 and Stereoscopic Debt

Phase 2 designates the 2-to-7-year temporal window (extensible to 12-17 years for strict amblyopia) during which treatment of visual acuity and refraction remains possible with significant functional gain. The PEDIG trials have solidly established that amblyopia treatment via occlusion or atropine penalisation remains effective through adolescence, with a mean acuity gain of 1 to 2 Snellen lines even in children treated late. This extended window contrasts with the tight binocular window of Phase 1: visual acuity depends primarily on the maturation of macular photoreceptors and the parvocellular pathway, whose plasticity remains accessible longer than that of binocular fusion.

The concept of Stereoscopic Debt designates the cumulative neurodevelopmental cost of late binocular correction (beyond the Phase 1 window): fine stereopsis will remain durably deficient, but partially restored coarse stereopsis provides a sufficient depth signal for basic visual predictive coding. Late partial correction of the debt interrupts the autistic deepening cascade by restoring an intelligible afferent signal for the predictive brain, without however restoring the entirety of lost binocular functions. This nuance is essential to the CSC framework: it distinguishes what is definitively lost (fine stereopsis for late-corrected individuals) from what can still be preserved in terms of adult functional trajectory (the compensatory cascade halted rather than pursued).

Chapter 6. The Signal Paradigm - Noise vs. Silence

A structural critique of the CSC framework consists of invoking congenitally blind children as a counterexample to the necessity of vision in neurotypical social development. This objection rests on a fundamental categorical confusion between two radically distinct physiological regimes: total deprivation (sensory silence) and partial or aberrant deprivation (sensory noise). When the visual afferent signal is totally absent, as in congenital blindness, the brain triggers a well-documented rescue mechanism: cross-modal plasticity. The visual cortex deprived of input is progressively requisitioned by intact sensory modalities, and the social development of the congenitally blind child does not depend on the missing visual signal.

The configuration of an individual presenting with uncorrected strabismus, a chronic convergence deficit, or severe uncompensated refractive anomaly is radically different. The visual afferent signal is not absent: it is aberrant, unstable, contradictory. From the standpoint of predictive coding, the autistic brain receiving this aberrant signal generates a chronic unresolved prediction error, constituting a permanent low-level allostatic overload. The Noise versus Silence Paradigm can be summarised in three linked propositions: total sensory silence triggers adaptive cross-modal plasticity; chronic sensory noise generates permanent differential allostatic overload depending on individual prediction error weighting; the CSC framework does not apply to total deprivation but specifically to partial or aberrant deprivation.

Chapter 7. The Retinal Signature as a Stratification Tool

The work of Constable and colleagues (2020, 2022) documents a specific alteration of the photopic b-wave of the electroretinogram (ERG) in adult ASD populations compared to non-autistic controls: the b-wave amplitude is reduced and its timing modified, in a signature sufficiently robust to permit automatic discrimination by supervised algorithm with satisfactory sensitivity and specificity. The additional retinal dissociation between ASD and ADHD is decisive for CSC: the photopic b-wave is reduced in ASD while the PhNR (Photopic Negative Response) component is elevated in ADHD (Constable et al. 2023). This dissociation demonstrates the diagnostic specificity of neurodevelopmental retinal signatures.

An essential critical reframing: the alteration of the ASD photopic b-wave is not a correctable functional deficit it is a structural signature of the retinal organisation of the autistic individual, likely linked to the different GABAergic modulation of ON bipolar cells. This signature persists into adulthood independently of peripheral optical corrections. Prescribing glasses or operating on strabismus will not normalise the b-wave. The CSC framework therefore reformulates the role of ERG: it is not a proof of the efficacy of correction, but a stratification tool for ASD subpopulations according to the nature of the visual deficit, enabling the distinction of three clinically relevant subgroups (normal ERG plus peripheral deficit; abnormal ERG plus peripheral deficit; abnormal ERG without peripheral deficit).

Chapter 8. Health-System Stratification and Attenuation of the Severity Gradient

International epidemiology of ASD offers a natural experiment: five differently organised health systems share approximately the same genetic biological burden, but diverge fundamentally in the organisation of paediatric visual screening. USA: Repka 2021 shows an odds ratio of 0.65 for amblyopia treatment success in Medicaid children versus privately insured. UK: NHS RTT at 58.9% in 2024 (target 92%), 11.8% of the population holds private medical insurance concentrated at 81% in upper employer tiers. Germany: GKV versus PKV differential of 30.7 days specialist wait time versus 7.8 days.

Canada: median age at diagnosis of 3.7 years (the earliest of the five countries). France: the only system with a legally mandated paediatric visual screening schedule at 9 months, 24 months, 3-4 years, supplemented by Decree 2022-691 on direct access to orthoptists for 9-15 month-olds. This decree constitutes a quasi-experimental test of considerable informative value: a precisely dated administrative discontinuity, allowing the application of regression discontinuity statistical methods that powerfully control for confounders. The cross-arm reading of the comparison is deliberately confined to the ecological level the observed correlations do not permit inference of a causal effect at the individual level but the covariance is sufficiently coherent to motivate the prospective programme.

This chapter introduces the Variability-Integration Cleft (VIC) as a methodological category in its own right. VIC simultaneously designates three dimensions of the same phenomenon: the absence of individual longitudinal data covering the transition from the paediatric sensory critical window to the adult measure of support level; the possibility that the closure of critical windows renders the adult state partially unpredictable from the paediatric state alone; and the discrepancy between the variability of support needs during childhood and their stabilisation in adulthood, often mediated by masking and its physiological costs. For a full exploration of the VIC framework as a cross-cutting methodological category, see

Chapter 9. The Inverse Masking Effect

The CSC framework proposes a fundamental reframing of the aetiology of Level 1 ASD phenotypes with uncorrected visual comorbidities. Rather than considering strabismus or an uncorrected visual deficit as a fortuitous comorbidity added to a primary Autism Spectrum Disorder, this framework hypothesises it as a peripheral cascade trigger. This reformulation does not invalidate the existence of an underlying neurobiological vulnerability this remains constitutive of the individual. It proposes, however, that the clinical expression of the observable ASD phenotype, in a non-trivial fraction of Level 1 cases, is conditioned by the triggering of the behavioural cascade precipitated by the visual deficit.

The central concept proposed is the following: uncorrected strabismus acts as inverse masking. Instead of masking an underlying autism (which conscious behavioural masking does in adulthood), it masks the individual's compensatory capacities by preventing their early deployment. If the same child had been visually corrected at 12 months, they would have maintained binocular convergence, maintained joint attention, and spontaneously developed social cognition strategies that would have made them neurodivergent but clinically adapted. Their underlying atypical neurobiology would have remained, but their phenotypic expression would have been substantially different.

Level 1 - Neurobiological predisposition: atypical neurobiology, over-weighting of prediction errors, ERG signature.

Level 2 - Peripheral trigger: strabismus, convergence or accommodative deficit between 6 and 18 months, undetected.

Level 3 - Behavioural trap: visual convergence avoidance, joint attention suppressed, early social training missed.

Level 4 - Neurodevelopmental deepening: specialisation in local processing, clinically observable Level 1 ASD phenotype at 3-4 years.

The five-level causal cascade model of CSC. From neurobiological substrate to clinical expression, each level mediates the next.

Chapter 10. The Causal Cascade Model (Revised Version)

The causal cascade model of the CSC framework articulates five linked levels whose mediations are specified by the contributions of Chapters 6 (Noise/Silence paradigm), 7 (ERG signature as stratification), and 9 (inverse masking). This five-level model replaces the four-level model of the previous version. The additional level (Level 3, neurocomputational mediation) specifies the mechanism by which the visual deficit translates into a behavioural cascade, and constitutes the point of connection with the independent framework of atypical ASD predictive coding of Pellicano and Burr.

The model is compatible with circular causality: a mild visual deficit can precipitate withdrawal, which further degrades the oculomotor muscles, which degrades the visual signal, which amplifies withdrawal, in a feedback loop. The CSC framework is compatible with this circular causality without depending on it. The primary directionality can be empirically tested by Study 2 (stratified prospective cohort, Chapter 12): if the objectified visual deficit is already present at 18 months in individuals who will develop a significant ASD phenotype at 36 months, the strabismus-to-ASD causality is partially established.

Chapter 11. Limitations and Falsifiability Criteria

CSC clearly satisfies six of the nine Bradford-Hill criteria (strength of association, consistency, temporality, biological plausibility, coherence with existing knowledge, analogy), two partially (specificity for the ERG signature, dose-response gradient for stereopsis), and one direct experimentation remains to be conducted. This framework is not causally demonstrated to date. Its causal demonstration requires the conduct of the three studies of the prospective programme described in Chapter 12.

Four falsification conditions are pre-specified. Condition 1: if the age-at-correction / adult-level correlation is null after adjustment in the prospective cohort (n >= 500, >= 15-year follow-up), the model is refuted. Condition 2: if the post-Decree 2022-691 natural cohort shows no variation in the ASD severity sociodemographic gradient at a 10-to-15-year horizon. Condition 3: if the DSM-5-level-stratified meta-analysis does not show a significantly higher proportion of late visual correction histories among Levels 2 and 3. Condition 4: if the ADHD pilot trial shows no reduction in psychostimulant prescriptions in the arm with prior ophthalmological assessment. The author commits to publishing results of each condition whether positive or negative.

Epistemic note: CSC does not claim that strabismus creates autism ex nihilo. It claims that strabismus causes an already vulnerable neurodevelopmental trajectory to bifurcate toward a clinically more severe ASD phenotype. Without the Level 1 neurobiological predisposition, uncorrected strabismus produces a visually impaired child, not an autistic child. With the predisposition but without the strabismus, the child develops early compensatory strategies and presents an adapted neurodivergent phenotype.

Chapter 12. Missing Studies and Prospective Programme

The conversion of CSC from the status of a hypothesis compatible with existing data to that of a demonstrated causal result requires the conduct of five studies that the current literature has not produced. Study 1 is a retrospective meta-analysis stratified by DSM-5 support level: the main question is whether the proportion of late visual correction histories differs significantly between Levels 1, 2, and 3 in adulthood, after adjustment. IPDMA (Individual Patient Data Meta-Analysis) protocol, 2,000 target subjects, 36 months.

Study 2 is the ERG-stratified prospective longitudinal cohort: inclusion of 500 autistic children before 24 months, stratification into three arms by ERG signature and presence or absence of peripheral visual deficit, minimum 18-year follow-up. Estimated budget 9 million euros over 22 years. Study 3 is a randomised pilot trial for discrimination of primary versus secondary ADHD (200 children, 30 months). Study 4 exploits Decree 2022-691 as a geographically stratified natural cohort over 15 years. Study 5 is a meta-analysis of ASD prevalence in congenital blindness cohorts, empirically testing the Noise/Silence paradigm: per CSC, blindness (silence) should not be associated with ASD prevalence above the general population.

Chapter 13. Generalisations: VIC as a Cross-Cutting Methodological Category

The Variability-Integration Cleft (VIC), named in Chapter 8 in its visual-ASD instantiation, is not specific to the ASD domain. The framework applies to any developmental phenomenology governed by a critical plasticity window whose closure precedes adult phenotype measurement by the canonical instruments of the domain. Seven candidate root phenomena have been inventoried: visual plasticity (the source case of the present thesis), auditory plasticity and language phenotype, vestibulo-proprioceptive plasticity and developmental coordination disorder, social-emotional attachment and borderline stabilisation, multisensory integration and entry into the schizophrenia spectrum, pubertal hormonal window and identity stabilisation, and attentional-prefrontal scaffolding and adult ADHD subtyping.

The V/I/C triaxial decomposition transfers by template to each phenomenon. A composite scoring rubric integrating a severity score, a tractability score, and a derived priority score enables cross-domain comparison and directs prospective resource allocation toward phenomena with the highest bridging potential. For the detailed presentation of the VIC Framework as an autonomous research specification including per-phenomenon operationalisations, R9 simulator anchors, the interactive synthetic demonstration, and clinical notices see

Chapter 14. Clinical Implications and Operational Recommendations

The correlational nature of current evidence does not prevent the identification of recommendations whose rationale does not require complete causal demonstration. These recommendations remain conditional on prospective results. During any diagnosis or clinical suspicion of ASD, and regardless of age, a comprehensive ophthalmological and orthoptic assessment should be included in the initial workup. This assessment includes objective visual acuity measurement, binocular alignment evaluation, stereopsis and accommodation measurement, fundus examination, and ideally a photopic electroretinography recording.

Before prescribing a psychostimulant for a newly diagnosed ADHD child, a combined ophthalmological-orthoptic assessment with photopic ERG measurement would allow identification of the subgroup for whom an uncorrected visual deficit constitutes the primary factor underlying the attentional presentation. Finally, given the empirical discontinuity at 24 months for stereoscopic recovery, any surgical referral in paediatric strabology for a child suspected or diagnosed with ASD warrants temporal prioritisation equivalent to functional emergencies.

Chapter 15. Epistemological Critique of Medical Silos

The late and fragmented discovery of the CSC framework is attributable to a structural factor that must be named: the compartmentalised disciplinary architecture of contemporary academic medicine. Paediatric ophthalmology evaluates the visual receptor organ according to rigorous mechanical criteria and declares vision normal once binary criteria are satisfied. This standard practice, perfectly valid within its scope, systematically ignores the neurocomputational ergonomics of vision: the attentional cost of slightly effortful convergence, the allostatic load of unstable but non-pathological binocular processing, the chronic discomfort of accommodation at the limit of compensation. These dimensions do not appear in standard ophthalmological nomenclature because they correspond to no identifiable binary pathology.

Conversely, child and adolescent psychiatry evaluates the subject's behavioural outputs according to DSM-5 symptom criteria without systematically interrogating the quality of the afferent signal that generated those outputs. This disciplinary architecture creates a cross-disciplinary epistemic blindness. The child presenting subtle strabismus and a non-pathological accommodative deficit in the binary sense is declared 'cured' by the ophthalmologist, then diagnosed with 'idiopathic' ASD by the psychiatrist, without the link between the two contemporaneous observations ever being established. The CSC framework is positioned precisely at the interface of these two disciplinary blind spots.

The present thesis assembles five convergent empirical axes and proposes a unified theoretical framework, Critical Sensory Chronology, under which an empirically non-trivial fraction of the phenotypic variability of Autism Spectrum Disorder in adulthood would be attributable to access, prior to the closure of critical windows of visual plasticity, to early and high-quality paediatric ophthalmological care. The model is compatible with accumulated data, proposes a defensible tripartite partition of the neurodevelopmental field, and identifies explicit falsification criteria. It does not substitute for genetic, neurochemical, or connectivity models. It proposes a complementary layer of explanation.

The current scientific defensibility, in the absence of strong causal demonstration, rests on three pillars: consistency with available data (convergence of the five axes and Bradford-Hill criteria); explicit falsifiability guaranteed by the four pre-specified operational conditions; and epistemological modesty guaranteed by the explicit acknowledgement of methodological limitations and the author's personal involvement. The conversion of this correlational compatibility into causal demonstration requires the conduct of the five studies of the prospective research programme. These studies constitute the primary object of the doctoral project.

Desvaux, G.J.Y. (2025). Critical Sensory Chronology (CSC) - Ophthalmological integration, cortical plasticity and stratification of phenotypic expression in Autism Spectrum Disorder. Version 5.0. Hope 'n Mind SASU.