A new study published in the open-access journal General Psychiatry found that thickening of the macular layer in the right eye’s retina is significantly associated with a heightened risk and severity of postoperative delirium in older patients undergoing general anaesthesia. The findings suggest that macular thickness, as measured through a standard ophthalmological test, may be a helpful non-invasive biomarker to identify those at increased risk of this common and serious post-surgical complication.
Postoperative delirium is a frequent and concerning outcome for older individuals recovering from surgery. Characterised by sudden confusion, disorganised thinking, and altered levels of consciousness, it can have lasting consequences on a patient’s physical and cognitive health. Those who develop delirium tend to require extended hospital stays, are less likely to regain complete independence, and face increased chances of needing assistance with daily activities or even permanent placement in nursing facilities. Furthermore, there is mounting evidence that postoperative delirium is linked to long-term cognitive decline and an elevated risk of dementia.
Because visual impairment has already been identified as a risk factor for postoperative delirium, the research team sought to investigate whether specific structural changes in the retina could indicate increased vulnerability. In particular, they focused on the macula, the central part of the retina responsible for sharp, detailed vision. They hypothesised that abnormal thickening of this retinal layer might reflect underlying neurological changes that predispose older adults to cognitive disturbances following surgery.
To explore this possibility, the study recruited 169 patients aged 65 or over who were scheduled to undergo elective procedures—such as hip or knee replacements or kidney and prostate surgeries—at Shanghai 10th People’s Hospital. Before surgery, all participants underwent optical coherence tomography (OCT), a non-invasive imaging technique that provides high-resolution cross-sectional images of the retina. The thickness of the macula in both eyes was measured, and each patient was subsequently monitored for signs of delirium during the first three postoperative days using the Confusion Assessment Method (CAM). The severity of any delirium observed was assessed using the CAM-Severity (CAM-S) scale, which evaluates features such as inattention, disorganised thinking, sleep disturbances, agitation, and psychomotor slowing.
The results revealed that 40 patients—approximately 24% of the total sample—developed postoperative delirium. These individuals had a significantly greater average macular thickness in the right eye (283.35 µm) compared to those who did not experience delirium (273.84 µm). Statistical analysis further showed that, even after adjusting for age, sex, and mental status, an increase in right eye macular thickness was linked to a 1.593-fold higher likelihood of developing postoperative delirium. Moreover, greater macular thickness was associated with increased risk and higher severity scores on the CAM-S scale. Interestingly, the macular thickness in the left eye did not demonstrate the same association, suggesting a lateralised effect that aligns with previous research indicating asymmetrical patterns in retinal and cerebral neurodegeneration.
While these findings open new avenues for the early identification of patients at risk for postoperative delirium, the authors caution against over-interpretation. As an observational study, it cannot establish a definitive cause-and-effect relationship. The small sample size and lack of data on potential confounders—such as eye dominance—pose limitations. Nonetheless, the results point to a promising direction for future research. The study concludes by proposing that OCT-derived macular measurements might be integrated into preoperative assessments for older adults, helping clinicians anticipate and mitigate the risk of postoperative delirium through tailored interventions and closer monitoring.
More information: Zhongyong Shi et al, Association between retinal layer thickness and postoperative delirium in older patients, General Psychiatry. DOI: 10.1136/gpsych-2024-101740
Journal information: General Psychiatry Provided by BMJ Group
