Evaluation of vision in gnathological and orthodontic patients with temporomandibular disorders: a prospective experimental observational cohort study

Objectives: Temporomandibular disorders (TMDs), orthodontic diseases, and vision dysfunctions seem to be strictly related. The purpose of this study was to prove the relationship, to evaluate the prevalence and the distribution of vision defects in dysfunctional and orthodontic patients, and to establish the type of the relationship. Materials and Methods: A total of 100 patients with TMDs were selected and studied through epidemiological analyses of the following factors: gnathological parameters (temporomandibular joint pathologies according to Diagnostic Criteria for Temporomandibular Disorders); occlusal and skeletal parameters (overjet, overbite, dental class, transversal discrepancies, and mandibular asymmetry); and orthoptic parameters (refractive defects and oculomotor diseases). A prospective experimental observational cohort study was conducted. A comparison with the average frequency of vision defects of the Italian population was performed. The prevalence of vision defects was evaluated. All gnathological and orthodontic parameters were associated with the orthoptic ones. A descriptive and statistical analysis of the data was carried out with the Statistical Package for the Social Sciences software; z test (P 0.05), frequency analysis (frequency 50%), chi-square test, and Student's t test (P 0.05) were performed. The scientific consistency was evaluated by using the scientific criteria of Bradford Hill. Results: The comparison with the Italian population showed a higher frequency of refractive defects in the study sample (P 0.001). The most frequent vision defects were phorias (92%) and tropia (3%). The increased frequency of ocular convergence reduction in the presence of disc displacement with reduction was significant (n = 28; 60%; P 0.05). In the presence of asymmetry, low frequencies of astigmatism (n = 18; 30%) were observed compared to its absence (n = 22; 54%) (P 0.05) and high frequencies of motor ocular deviations (n = 59; 100%) were observed compared to its absence (n = 36; 88%) (P 0.05). In the presence of headache, low frequencies of emmetropia (n = 13; 22%) and higher frequencies of hyperopia (n = 18; 30%) were observed (P 0.05). Two of five scientific criteria of Bradford Hill were met. Conclusion: It seems to emerge a possible positive relationship between TMD and vision defects. In particular, the most interesting associations were found between functional or skeletal orthognathic alterations and oculomotor dysfunctions. However, it was not possible to establish the type of relationship.