Illicit Drug Use Tied to Vision Loss

Pauline Anderson

August 26, 2020

A new study shows vision loss is almost twice as common among military veterans than among civilians and was independently associated with self-reported illicit drug use.

The results should trigger increased awareness among both behavioral and eye health specialists, study author Justin Tyler McDaniel, PhD, associate professor of Public Health at Southern Illinois University's School of Human Sciences, Carbondale, told Medscape Medical News.

"As behavioral health folks routinely screen for alcohol misuse and drug use, they potentially could do some vision screening and refer folks to an optometrist if necessary," McDaniel said.

Conversely, ophthalmology professionals "perhaps could begin to implement screening for drug use during routine visits for eye checkup," and refer those who screen positive, he said.

The paper was published online August 13 in BMJ Military Health.

Research Streams

Studies have uncovered numerous associations between substance abuse and ocular injuries. For example, some have linked cocaine and methamphetamine with corneal injuries, and others have tied opiates, cocaine, methamphetamine and "bath salts," synthetic recreational stimulants, to iris injuries.

Justin Tyler McDaniel, PhD

Vision impairment has been associated with other health behaviors and conditions as well, the researchers note, including HIV, hypertension, smoking, diabetes, poor diet, physical activity, cancer, depression, gum disease, and socioeconomic status.

The new study aimed to more closely assess these streams of research "to see if there's any association between drug use and vision loss," said McDaniel.

The study included 1578 randomly selected participants (1472 civilians and 106 military service members or veterans) in the 2013 to 2018 cycles of the National Health and Nutrition Examination Survey (NHANES). NHANES is a nationally representative survey of health and nutrition status among US residents.

Since NHANES doesn't interview institutionalized individuals, which would include those in active military service, "we assume that all our sample was veterans," who were retired from active duty and living in the community, said McDaniel.

Survey questions determined use of cocaine, methamphetamine, and heroin, and of injection drug use. In addition to illicit drug use, study covariates included age, gender, race/ethnicity, education level, household income, blood pressure, diabetes, smoking, diet, sedentary time, health insurance, cancer history, depression, HIV status, and oral health.

Vision Problems

The dependent variable was self-reported vision loss, which was obtained from the disability module in the NHANES. Respondents were asked if they are blind or have serious difficulty seeing even when wearing glasses.

The analysis showed that compared to civilians, veterans had a significantly higher prevalence of HIV-positive status (1.89% vs 0.41%; P = .038) and illicit drug use (20.75% vs 13.62%; P = .041).

While active military members tend to have lower rates of illicit drug use compared with civilians because of a "zero tolerance" policy and random drug testing, veterans retired from service may be dealing with posttraumatic stress disorder (PTSD) that "may be connected to beginning of illicit drug use," said McDaniel.

The rate of 1 in 5 veterans using illicit drugs seems high, but should be taken in context, said McDaniel, noting that the measure of illicit drug use in the survey is "quite broad."

"It could be someone who chronically uses illicit drugs or someone who just tried it one time," he noted.

More veterans in the study (8.49%) reported vision loss than civilians (4.48%). The higher prevalence of vision loss among veterans could be because of exposure to combat explosions, said McDaniel, but veterans also had more risk factors possibly linked to vision impairment.

For example, they had higher mean values of systolic blood pressure (125.8 vs 122.5 mm Hg), more pack years of cigarette smoking (8.29 vs 4.25), and more sedentary minutes per day (379.15 vs 337.07 min).

On the other hand, civilians had a higher prevalence of poor dietary habits; only 7.61% reported trying the MyPlate diet plan, which highlights elements of a healthy diet, vs 13.21% of veterans (P = .032).

Strongest Predictors

In a model that adjusted for risk factors of vision loss — including physical inactivity, diabetes, socioeconomic factors, and other health behaviors and conditions — military service status (adjusted β coefficient [aB] 0.91; P = .04) and illicit drug use (aB 0.72; P = .02) were associated with increased risk for vision loss. The next strongest predictor was HIV-positive status.

McDaniel stressed that the study shows only an association between drug use and vision loss, without determining from which direction the association is occurring.

"We have no way of inferring causation here," he said. "It could be that vision loss is a stressor that results in drug use, or it could be that a history of drug use leads to vision loss down the road."

McDaniel would like future research projects to determine where in the US veterans are most prone to illicit drug use and to vision loss. "Then we can begin to really refine and target some public health programming in those areas," he said.

"We could then maybe look at screening and brief interventions for service members who use drugs. And for vision loss, we could implement some sort of screening and vision rehabilitation programs."

Service Experiences

Commenting on the study for Medscape Medical News, Kate Hendricks Thomas, PhD, from George Mason University's Department of Global and Community Health, Fairfax, Virginia, said the current study is a continuation of McDaniel's "interesting research" on the links between service experiences, behavioral health trends, and health outcomes among active military and veterans.

"The results of the present study are interesting in that they outline key predictor variables' influence on eye health," said Thomas.

"The study does a nice job of demonstrating empirically what we know about risk behaviors in military veterans," — that they can lead to poorer health outcomes, said Thomas.

While substance abuse isn't the only behavior that can be correlated to poor eyesight, "in the present study, it demonstrated a strong enough link that screening veterans for addictive behaviors is warranted in the clinical setting."

The authors have not declared a specific grant for this research from any funding agency in the public, commercial, or not-for-profit sectors. McDaniel and Thomas have disclosed no relevant financial relationships.

BMJ Mil Health. Published online August 13, 2020. Abstract

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