Alzheimer’s disease (AD) is an age-related progressive neurodegenerative brain disorder that represents the most common type of dementia. It poses a significant diagnostic challenge that requires timely recognition and treatment. Currently, there is no effective therapy for AD; however, certain medications may slow down its progression. The discovery of AD biomarkers, namely, magnetic resonance imaging, positron emission tomography and cerebrospinal fluid molecules (amyloid-β and tau) has advanced our understanding of this disease and has been crucial for identifying early neuropathologic changes prior to clinical changes and cognitive decline. The close interrelationship between the eye and the brain suggests that tears could be an interesting source of biomarkers for AD; however, studies in this area are limited. The identification of biomarkers in tears will enable the development of cost-effective, non-invasive methods of screening, diagnosis and disease monitoring. In order to use tears as a standard method for early and non-invasive diagnosis of AD, future studies need to be conducted on a larger scale.

Dry eye disease (DED) is a highly prevalent multifactorial disorder of the ocular surface that extends beyond local tear film pathology to involve systemic immune, neuroendocrine, and neurosensory mechanisms. Increasing evidence reveals a strong and bidirectional association between DED and psychiatric disorders, particularly depression, anxiety, post-traumatic stress disorder (PTSD), and sleep disturbances. This review synthesises the current knowledge on shared molecular, neuroimmune, and neuropathic pathways that underlie this comorbidity. Key mechanisms include hypothalamic–pituitary–adrenal (HPA) axis dysregulation, systemic and ocular inflammation, oxidative stress, mitochondrial dysfunction, and impaired neurotrophic signaling, especially reduced brain-derived neurotrophic factor (BDNF). Dysregulation of monoaminergic neurotransmitters such as serotonin and norepinephrine not only contributes to mood disturbances but also alters tear secretion and corneal pain perception. Corneal nerve changes and trigeminal–limbic sensitisation further reinforce the overlap between neuropathic ocular pain and affective dysregulation. Psychotropic medications, while essential for psychiatric care, may exacerbate ocular surface dysfunction through anticholinergic effects, altered neurotransmission, and tear film instability, highlighting the iatrogenic dimension of this interface. Conversely, tear-based biomarkers, including cytokines, serotonin, and BDNF, offer promising translational tools for patient stratification, diagnosis, and treatment monitoring across ocular and psychiatric domains. Recognising DED as part of a systemic, biopsychosocial continuum is critical for effective management. Multidisciplinary strategies that integrate ophthalmologic and psychiatric care, alongside novel therapies targeting shared molecular pathways, provide a framework for improving outcomes. Future research should prioritise longitudinal studies, biomarker validation, and personalised interventions to address this complex comorbidity.

Obstructive sleep apnoea (OSA) is a prevalent condition characterised by intermittent upper airway obstruction during sleep, resulting in recurrent hypoxia and sleep fragmentation. Emerging evidence highlights the significant impact of OSA on neuro-ophthalmological health, linking it to conditions such as glaucoma, optic neuropathy, papilledema, and visual field defects. These associations emphasise the importance of understanding the mechanisms connecting OSA to neuro-ophthalmological disorders to enhance early diagnosis and management. This review explores the pathophysiological pathways, including hypoxia-induced vascular dysregulation, oxidative stress, inflammation, and intracranial pressure fluctuations, that contribute to ocular and neurological impairments in OSA patients. Advanced diagnostic tools, such as optical coherence tomography and polysomnography, offer promising avenues for detecting subclinical neuro-ophthalmological changes, enabling timely intervention. Management strategies, primarily centred on continuous positive airway pressure therapy, have shown efficacy in mitigating OSA-related neuro-ophthalmological complications. However, surgical and pharmacological interventions and lifestyle modifications remain vital components of a multidisciplinary approach to care. Despite advancements, significant research gaps persist, particularly in understanding the long-term impact of OSA treatment on neuro-ophthalmological outcomes and identifying specific biomarkers for early detection. Future research should prioritise longitudinal studies, interdisciplinary collaborations, and personalised medicine approaches to address these challenges. Recognising and treating neuro-ophthalmological disorders in OSA patients is imperative for improving quality of life and preventing irreversible visual and neurological damage.