Association between ADHD and myopia among schoolchildren

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A new Chinese investigation found that attention-deficit hyperactivity disorder (ADHD) is associated with reduced myopia prevalence, more hyperopic spherical equivalent refraction (SER), and shorter axial length (AL) in schoolchildren, according to Xiu Nian Chen, PhD, from the Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong.

Chen and colleagues explained that increased risks of astigmatism, strabismus, reduced near point of convergence, color discrimination, and contrast sensitivity have been reported in patients with ADHD.^2-5 This is noteworthy considering that myopia is the most common ocular disease worldwide with a heavy public health burden in many parts of the world.⁶

While a few studies have found no difference in the prevalence of myopia between patients with ADHD and healthy controls,^2,7,8 Chen and colleagues noted that the methodologies of those studies may not have been able to detect a difference.

Another consideration is that the first-line treatment for ADHD, oral methylphenidate, inhibits the reuptake of dopamine and norepinephrine, thereby enhancing catecholaminergic activity in the brain regions involved in ADHD pathogenesis, which leads to symptom improvement.^9-11 “Concurrently,” they stated, “the dopamine system plays a significant role in mediating myopic eye growth and is broadly associated with other myopic mechanisms.^12,13 Thus, it is intriguing to explore whether oral methylphenidate affects myopia by influencing dopamine levels.”

Moreover, while near-work and outdoor activity affect the myopia prevalence, children with ADHD may have different patterns of near-work and outdoor activity compared to their unaffected peers, indicating that the impact of ADHD symptoms on myopia remains unclear.

Cross-sectional study

The children in the study were 6 to 8 years old and underwent a cycloplegic autorefraction and AL measurements between 2016 and 2021. The ADHD diagnoses were established according to the ICD-10 criteria, and the ADHD symptoms were assessed using the Strengths and Weaknesses of ADHD-Symptoms and Normal-Behaviors Questionnaire.

The study included 474 children with ADHD and 9,950 control children.

The authors reported that the age- and sex-adjusted myopia prevalence was lower in the ADHD group (21%) compared with the controls (26%; P= 0.02). Multivariable regression analysis showed that the children with ADHD had less myopia (odds ratio [OR] = 0.75; P = 0.03), higher SER (β = 0.13; P = 0.04), and shorter AL (β = −0.07; P = 0.03).

Specifically, the patients with ADHD who were treated with oral methylphenidate had less myopia (OR = 0.61, P = 0.04), higher SER (β = 0.36; P < 0.001), and shorter AL (β = −0.25; P < 0.001) compared to the controls.

Chen and colleagues found that each additional month of treatment with oral methylphenidate was associated with a higher SER (β = 0.02; P = 0.01) and shorter AL (β = −0.01; P = 0.01).

“For each 1-point increase in attention-deficit scores, the children were found to be less myopic (OR = 0.88, P = 0.01), having higher SER (β = 0.07; P = 0.003), and shorter AL (β = −0.04; P = 0.001),” they reported.

They also found that the prevalence of myopia among children with ADHD increased to 32% during the COVID-19 pandemic compared with 23% before the COVID-19 pandemic (P = 0.04).

The authors concluded, “This cross-sectional study found that ADHD is associated with reduced myopia prevalence, more hyperopic SER, and shorter AL.”

However, they advised that because the effect sizes of these associations were small, the clinical relevance of the findings needs to be interpreted with cautious.

References

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