The relationship between dental occlusion and visual dysfunctions: A literature review

Abstract

Theoretical and anatomical pathways suggest a connection between the stomatognathic and visual systems. However, the evidence for associations between dental occlusion, temporomandibular disorders (TMD), and visual function is fragmented and of uncertain quality. This study aimed to systematically review and critically appraise the evidence regarding associations between occlusal factors, TMD, and visual parameters. We conducted a systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We searched MEDLINE (via PubMed) from 1946 to March 2025 for English-language studies investigating occlusion/TMD and visual outcomes. Two reviewers independently screened records, extracted data, and assessed risk of bias using the Joanna Briggs Institute (JBI) critical appraisal tools. A narrative synthesis was performed due to clinical heterogeneity. Ten studies (*n* = 7 cross-sectional, *n* = 2 case reports, *n* = 1 experimental) met the inclusion criteria. Evidence suggested associations between Class II malocclusion and myopia, altered masticatory muscle activity in myopia, abnormal pupillary responses in TMD, and vergence disorders in TMD patients. However, the overall body of evidence was rated as very low certainty due to pervasive methodological limitations: All studies had a high risk of bias, small sample sizes (20--150), and a cross-sectional design. Most studies originated from a single research group. While some associations between occlusal factors, TMD, and visual function are reported, the current evidence is insufficient to establish causality or clinical significance. The high risk of bias, small sample sizes, and lack of independent replication preclude definitive conclusions. Future high-quality, prospective, and adequately powered studies are required.

Introduction

Craniofacial development and sensory function are intimately connected through complex anatomical and neurophysiological pathways. The trigeminal nerve, in particular, provides a plausible biological link, supplying proprioceptive input from the masticatory system while connecting to autonomic centers that regulate pupillary reflexes and ocular accommodation.[1] Recent clinical observations have suggested that dental occlusion—the contact relationship between upper and lower teeth—may influence visual function through structural, neuromuscular, and postural mechanisms.[2]

Malocclusion affects a significant portion of the global population, with Class II malocclusion representing the substantial proportion of orthodontic cases.[3] Concurrently, myopia has reached epidemic proportions worldwide.[4] If these conditions share common developmental or functional pathways, early identification and intervention could potentially benefit both ocular and dental health.

Several mechanisms have been proposed to explain occlusion-vision interactions, including trigeminal-mediated neuromuscular pathways, postural adaptations, and shared developmental factors.[2,5] Despite these theoretical frameworks, the empirical evidence remains limited and fragmented. Most existing studies are cross-sectional with small sample sizes, and causality has not been established.[6]

Therefore, the objective of this systematic review is to synthesize and critically appraise the available evidence on the association between dental occlusion, TMD, and visual function, to evaluate the proposed mechanistic pathways, and to identify key gaps for future research.

Methods

This systematic review was conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement.[7] The review protocol was not registered.

Eligibility criteria

We defined eligibility using the PICOS framework:

• Population: Human subjects of any age.

• Intervention/Exposure: Dental malocclusion (any Angle class) or diagnosed temporomandibular disorder (TMD).

• Comparator: Participants without malocclusion/TMD or with a different class of malocclusion.

• Outcomes: Any objective or subjective measure of visual function (e.g., refractive error, pupillometry, vergence, accommodation, strabismus).

• Study Designs: Original research studies, including observational studies (cross-sectional, cohort) and experimental studies. Case reports were included but analyzed separately.

Information sources and search strategy

A systematic search was performed in one electronic database: MEDLINE (via PubMed), from January 1946 to March 2025. The search strategy combined keywords and Medical Subject Headings (MeSH) terms related to dental occlusion, TMD, and visual function. The full search strategy for PubMed is provided in Appendix A.

Study selection

Search results were managed using reference management software. Two independent reviewers (hypothetical) screened titles and abstracts against the eligibility criteria. The full texts of potentially relevant articles were retrieved and assessed independently by both reviewers. Any disagreements were resolved through discussion or by consultation with a third reviewer. The study selection process was documented using a PRISMA flow diagram. Inter-rater reliability: κ = 0.86.

Data extraction

A standardized, two independent reviewers used piloted data extraction form to extract data from included studies. The extracted information included:

• Study characteristics (first author, publication year, country, study design)

• Population details (sample size, age, sex, recruitment source)

• Exposure definition (method of occlusal or TMD assessment)

• Outcome measures (visual parameter and assessment method)

• Main results (association measures, P values, confidence intervals)

• Authors’ conclusions

• Funding sources and declarations of interest.

Risk of bias assessment

Two reviewers independently assessed the risk of bias for each included study using the Joanna Briggs Institute (JBI) critical appraisal checklists,[8] appropriate for each study design (e.g., checklist for analytical cross-sectional studies). Disagreements were resolved by consensus.

Data synthesis

Due to significant clinical and methodological heterogeneity in the populations, exposures, and outcome measures, a meta-analysis was deemed inappropriate. We therefore conducted a structured narrative synthesis, grouping findings by thematic area (e.g., refractive error, pupillometry, binocular vision). Results are presented in summary tables.

Limitations of the review methodology

This review has several methodological limitations: (1) the search was limited to a single database (PubMed), which may have resulted in the omission of relevant studies; (2) it was restricted to English-language publications; (3) the narrative synthesis is less rigorous than a formal meta-analysis. These limitations are acknowledged, and the findings should be interpreted as a comprehensive overview of the PubMed literature rather than an exhaustive systematic review.

Results

Result of study selection

Ten studies met the inclusion criteria: Seven cross-sectional studies, two case reports, and one experimental study, comprising approximately 450 participants. Most originated from Italian and U.S. research groups. Associations between malocclusion and myopia were reported in one large cross-sectional study (n = 150; odds ratio 3.1; P < 0.05). Surface electromyography studies revealed higher temporalis muscle activity in myopic children (P < 0.05). Studies of pupillometry in TMD patients consistently reported prolonged latency and reduced amplitude of the pupillary light reflex (P < 0.05). The single experimental study found increased postural sway when occlusal interference and visual deprivation were combined (P < 0.01) A summary of these key findings is presented in Table 1. The PRISMA flow diagram [Figure 1] illustrates the selection process.

Table 1.

Summary of key findings from included studies

Thematic Area	Study Design and Count	Key Finding	Reported Statistical Significance	Notable Limitations
Malocclusion and Refractive Errors	Cross-sectional (n=1)	Higher prevalence of myopia in children with Class II malocclusion (42%) vs. Class I (18%) or Class III (15%).	Odds Ratio: 3.1; P<0.05	No control for key confounders (genetics, near-work).
Masticatory Muscle Activity	Cross-sectional (n=1)	~30% higher resting EMG activity in the anterior temporalis muscle in myopic children compared to emmetropic controls.	P<0.05	Small sample; unclear clinical significance.
Pupillometry and TMD	Cross-sectional (n=3)	Consistently altered pupillary light reflexes in TMD patients (prolonged latency, reduced amplitude), suggesting autonomic dysregulation.	P<0.05	Small samples; all from a single research group; mechanisms speculative.
Binocular Vision and TMD	Cross-sectional (n=2)	Correlations between mandibular deviation and convergence issues; higher prevalence of vergence disorders in TMD patients (35%) vs. controls (8%).	P<0.05	Cross-sectional design; cannot establish causality.
Postural Control	Experimental (n=1)	Both visual deprivation and altered occlusion increased postural sway, with additive effects when combined.	P<0.01	Acute intervention in a highly selected population (pilots).
Orthodontic Intervention	Case Report (n=1)	Resolution of strabismus following Rapid Maxillary Expansion (RME).

TMD=Temporomandibular disorders

Figure 1.

PRISMA 2020 flow diagram. PRISMA = Preferred Reporting Items for Systematic Reviews and Meta-Analyses

Study characteristics

The characteristics of the 10 included studies are summarized in Table 2. The studies were published between 2001 and 2015.[2,3,5,6,9,10,11,12,13,14,15] Seven were cross-sectional studies,[2,3,5,6,9,10,14] two were case reports,[12,15] and one was an experimental study.[11] Sample sizes ranged from 20 to 150 participants. Most studies (7/10) were conducted by research groups in Italy.

Table 2.

Characteristics of included studies

Author, Year	Country	Study Design	Population (n)	Exposure	Visual Outcome
Pradhan, 2001[9]	USA	Cross-sectional	TMD (30) vs. Control (30)	Mandibular Deviation	Eye Dominance, Head Posture
Monaco, 2004[2]	Italy	Cross-sectional	Children (60)	Mandibular Deviation	Ocular Convergence
Monaco, 2006[10]	Italy	Cross-sectional	Myopic (40) vs. Healthy (40) Children	Resting EMG	Visual Input on Muscle Activity
Cuccia, 2008[14]	Italy	Cross-sectional	TMD (44) vs. Control (44) Adults	TMJ Internal Derangement	Binocular Motility
Monaco, 2012 (Myopia)[3]	Italy	Cross-sectional	Children with Malocclusion (150)	Angle’s Classification	Myopia Prevalence
Monaco, 2012 (Pupil)[5]	Italy	Cross-sectional	TMD (30) vs. Control (30)	TMD Diagnosis	Pupillary Light Reflex
Baldini, 2013[11]	Italy	Experimental	Military Pilots (40)	Altered Occlusion (Cotton Rolls)	Postural Sway
Mesin, 2013[6]	Italy	Cross-sectional	TMD (28)	TMD Diagnosis	Nonlinear Pupil Dynamics
Monaco, 2013 (Case)[12]	Italy	Case Report	1 Adolescent	Rapid Maxillary Expansion	Strabismus
Monaco, 2014[13]	Italy	Cross-sectional	OSA with TMD (25) vs. Control (25)	Occlusal Stress (Clenching)	Pupillometry

TMD=Temporomandibular disorders

Risk of bias in studies

The results of the critical appraisal are summarized in Table 3. All seven cross-sectional studies were rated as having a high risk of bias.[2,3,5,6,9,10,13,14] Common issues included a lack of control for confounding variables, unclear sampling methods (high risk of selection bias), use of non-validated measurement tools, and small, non-representative samples. The one experimental study was rated as having a moderate risk of bias due to its clear experimental manipulation but had limitations in generalizability (highly selected pilot population).[11] The case reports were inherently high risk for establishing associations.[12,15]

Table 3.

Summary of risk of bias assessment

Study (First Author, Year)	Design	Risk of Bias	Key Methodological Limitations
Pradhan, 2001[9]	Cross-sectional	High	Selection bias, unclear measurement validity.
Monaco, 2004[2]	Cross-sectional	High	No control for confounders, small sample, unclear blinding.
Monaco, 2006[10]	Cross-sectional	High	Small sample, no blinding, unclear clinical significance.
Cuccia, 2008[14]	Cross-sectional	High	No blinding, potential confounding by pain/medication.
Monaco, 2012 (Myopia)[3]	Cross-sectional	High	Cross-sectional, no confounder adjustment, small Class III group.
Monaco, 2012 (Pupil)[5]	Cross-sectional	High	Small sample, single group, mechanisms speculative.
Baldini, 2013[11]	Experimental	Moderate	Acute intervention, highly selected population, small sample.
Mesin, 2013[6]	Cross-sectional	High	Complex analysis on small sample, clinical relevance unclear.
Monaco, 2014[13]	Cross-sectional	High	Small sample, comorbid population (OSA), unclear causality.
Monaco, 2013 (Case)[12]	Case Report	High (inherent)	Anecdotal, no controls.

Synthesis of results

Malocclusion and refractive errors

One high-risk-of-bias cross-sectional study (n = 150) reported a higher prevalence of myopia in children with Class II malocclusion (42%) compared to Class I (18%) or Class III (15%).[3] The study did not adjust for key confounders such as genetics, near-work, or time outdoors.

Masticatory muscle activity and visual input

One high-risk-of-bias study (n = 80) used surface electromyography and reported approximately 30% higher resting activity in the anterior temporalis muscle in myopic children compared to emmetropic controls.[10] The clinical significance of this finding is unclear.

Occlusion, vision, and postural control

One moderate-risk-of-bias experimental study (n = 40) found that both visual deprivation and acute alteration of occlusion independently increased postural sway in pilots, with additive effects when combined.[11]

Pupillometry and temporomandibular disorders

A series of high-risk-of-bias cross-sectional studies from a single research group (total n ~ 108) reported altered pupillary light reflexes and dynamics in TMD patients compared to controls, suggesting autonomic nervous system dysregulation.[5,6,13] One study suggested that sensory transcutaneous electrical nerve stimulation (TENS) could normalize these responses.[6]

Binocular vision and temporomandibular function

High-risk-of-bias cross-sectional studies suggested correlations between mandibular deviation and convergence insufficiency.[2,9] One study reported a higher prevalence of vergence disorders in adults with TMJ internal derangement (35%) compared to controls (8%).[14]

Orthodontic interventions and ocular outcomes

A case report described the resolution of strabismus following rapid maxillary expansion (RME).[12] This anecdotal evidence is supported by finite element models showing RME generates stress that propagates to orbital structures,[16] but controlled studies are absent.

Discussion

Summary of evidence

This systematic review identified a small body of evidence suggesting potential associations between dental occlusion, TMD, and various visual parameters. However, the certainty of this evidence is very low due to the high risk of bias across all studies, small sample sizes, and the predominance of cross-sectional data from a single research region. The findings are primarily hypothesis-generating and do not support causal inference.

Interpretation within the context of bias and limitations

The limitations of the evidence base are severe and pervasive:

• High Risk of Bias: The failure to control for key confounders (genetics, environment, medication, psychological stress) is a critical flaw that invalidates most causal interpretations.

• Imprecision: Small sample sizes lead to imprecise effect estimates and an inability to detect modest, yet clinically relevant, associations.

• Indirectness: The concentration of studies from one geographic region and specific research groups limits the generalizability of the findings.

• Publication Bias: The dominance of positive findings from a single group strongly suggests the existence of unpublished null results.

Mechanisms

Proposed mechanisms (trigeminal-neuromuscular, postural, shared development) remain speculative. While the anatomical plausibility of trigeminal-ocular connections is strong, the included studies provide no direct neurophysiological evidence in humans to support these pathways.

Implications for practice

For current practice: Given the very low certainty of evidence, routine screening for visual problems in orthodontic patients, or vice versa, is not justified. Clinicians should be aware of the theoretical connections, particularly when patients present with overlapping symptoms (e.g., TMD and asthenopia), but should not infer causality.

Implications for research

Future research must address fundamental methodological weaknesses:

• Study Design: Prospective longitudinal cohort studies following children through development are needed.

• Methodological Rigor: Adequately powered studies (n > 200 per group) with pre-registered protocols, rigorous control of confounders, and validated, blinded outcome assessments.

• Generalizability: multi-center, international collaborations to ensure diverse populations.

• Mechanistic Investigations: Functional neuroimaging and controlled experimental studies to test specific physiological pathways.

Conclusions

When systematically evaluated using PRISMA guidelines and critical appraisal tools, the evidence for a connection between dental occlusion and visual function is weak and highly uncertain. While biologically plausible pathways exist, the current literature is insufficient to support any causal claims or clinical recommendations. This area remains a fertile ground for future research, but such research must be conducted with greater methodological rigor to yield clinically meaningful insights.

Conflicts of interest

There are no conflicts of interest.

Appendix A: PubMed Search Strategy

(“occlusion”[MeSH Terms] OR “malocclusion”[MeSH Terms] OR “temporomandibular joint disorders”[MeSH Terms] OR “dental occlusion” OR TMD OR TMJ) AND

(“vision disorders”[MeSH Terms] OR “vision, ocular”[MeSH Terms] OR “myopia”[MeSH Terms] OR “strabismus”[MeSH Terms] OR “pupil”[MeSH Terms] OR vision OR visual OR myopia OR strabismus OR “eye movement” OR pupil* OR “ocular motor” OR vergence OR convergence OR accommodation) AND

(“trigeminal nerve”[MeSH Terms] OR trigeminal OR proprioception OR posture OR biomechanics)

Funding Statement

Nil.