Ocular defects in children and adolescents with severe mental deficiency.

Kirkpatrick-Steger et al. (1996) looked into the eyes of 260 non-verbal residents with severe intellectual disability. They used a full eye exam to count how many kids had vision loss, need for glasses, crossed eyes, or eye disease. All children lived in a long-stay center and could not tell staff if they saw poorly.

One in four children had severe visual impairment. One in four also needed glasses. Eight in every hundred had crossed eyes, and another eight had eye disease such as cataracts or optic nerve damage. Most problems had never been noticed before the study.

Holburn (2001) later pooled many papers and agreed: sensory loss is common and often missed in people with ID. The review says missed vision loss can look like behavior problems or self-injury.

Li et al. (2025) widened the lens. They showed kids with any developmental disability, not just severe ID, carry almost double the risk of astigmatism and other eye diseases. Their genetic data hint that brain and eye development share pathways, so the high numbers in K et al. may be part of a broader pattern.

Wu et al. (2023) found similar rates of crossed eyes and focusing errors in youths with autism, especially when ID was also present. The overlap supports the idea that severe developmental delay, no matter the label, raises eye-risk.

If you work with non-verbal clients, add a quick vision check to your intake. Ask parents for past eye reports, watch for squinting or eye rubbing, and refer to an optometrist early. Treating vision loss can cut problem behavior and boost learning.