Thickening of the eye’s retina associated with greater risk and severity of postoperative delirium in older patients

Thickening of the macular layer of the eye’s retina is associated with a greater risk of postoperative delirium for older patients undergoing surgery under general anesthetic, reveals a study published online in the open-access journal General Psychiatry.

Postoperative delirium is one of the most common complications for older patients after surgery and can have profound implications for long-term health and well-being.

Patients with postoperative delirium require longer hospital stays and are more likely to require support at home to help with daily tasks such as washing, dressing, and eating or being discharged into a nursing home. They also face a greater risk of cognitive decline and dementia.

Although there are no simple tests to identify patients at risk of developing postoperative delirium, visual impairment is a risk factor, so the authors set out to determine whether a thickened retinal layer called the macular might be a potential biomarker of the condition.

The study included 169 patients aged 65 years or more scheduled for hip or knee replacements, kidney or prostate surgery under general anesthetic at Shanghai 10th People’s Hospital who received an eye imaging test called optical coherence tomography (OCT) as part of their preoperative assessment to measure the thickness of the macular of the retina.

Patients were screened for delirium using the Confusion Assessment Method (CAM) algorithm each day for the first three days post-surgery.

Severity of any delirium was measured using the CAM-Severity (CAM-S) rating of 10 delirium features, including inattention, disorganized thinking, disorientation, reduced quality and amount of sleep, inability to sit still accompanied by anxiety, or slowed movement and thought processes.

Forty patients (24%) developed postoperative delirium, and these patients displayed a greater mean macular thickness (283.35 µm) of the right eye at their preoperative assessment than the patients who did not experience postoperative delirium (273.84 µm).

After adjusting for age, sex and mental state, greater preoperative macular thickness of the right eye was associated with 1.593 higher odds of developing postoperative delirium and the delirium experienced was of greater severity.

Thickness of the macular in patients with postoperative delirium was greater in the right eye, and thickening of the macular of the left eye was not associated with a greater risk of postoperative delirium.

The reasons for the differences in association observed between the right and left eye are unclear, the authors say, but are consistent with findings from previous studies. Studies of healthy individuals have found the mean macular thickness of the right eye to be thicker than that of the left eye, and studies of neurodegeneration have reported asymmetrical neurodegeneration of both the retina and brain.

This is an observational study, and as such, no firm conclusions can be drawn about cause and effect. The authors also acknowledge that the study has some limitations, including its small size and that potential confounding factors, such as pre-existing eye dominance, were not examined.

The authors conclude, “Our findings suggest that macular thickness measured by OCT may serve as a non-invasive marker and identify individuals vulnerable to developing postoperative delirium after anesthesia and surgery among geriatric patients.”

They add, “Further large-scale validation studies should be performed to confirm these results.”