Higher Amounts of Astigmatism Linked to Keratoconus Diagnosis

Keratoconus can progress quickly and evade detection early in its course; thus, investigators are searching for ways to identify the disease as early as possible to help those affected. As corneal shape irregularities are a hallmark feature of keratoconus, astigmatism has long been a component of its clinical presentation; however, the fairly common finding of astigmatism in the absence of keratoconus argues for a need for more clarification on the relationship.In one new study, researchers analyzed 896,377 adolescents and young adults aged 16 to 20 who underwent standardized medical assessment—including refraction and topography/tomography—to determine if level of astigmatism affected the likelihood of keratoconus. Astigmatism was categorized into groups of none, 0.75D to <2.00D, 2.00D to <3.00D, 3.00D to 5.00D and ≥5.00D. Astigmatism’s predictive value of keratoconus can be enhanced when combined with clinical history elements like frequent eye rubbing, family history of the disease or atopic ocular conditions. Photo: Brian Chou, OD. Click image to enlarge. Diagnosis of keratoconus in the entire cohort was rare, at just 0.21%. However, increasing astigmatism levels were strongly associated with higher prevalence of keratoconus, with a rate of 0.1% in the category of 0.75D to <2.00D, 9.5% with 3.00D to <5.00D and rising to 17.4% in the ≥5.00D group. More specifically, each 1.00D increase in cylinder power above 2.00D mapped onto a 1.76-fold increase in odds of the ectasia. Axis of astigmatism had limited discriminatory ability, and a cut-off of 2.88D of astigmatism yielded moderate sensitivity and specificity of 0.74 and 0.64, respectively.Upon discussion, the authors of the study note that while their analysis supported a strong association between astigmatism and keratoconus, the use of astigmatism level as a singular screening tool to potentially be used is limited. The cut-off of 2.88D is helpful, but they reiterate that “it should be used for keratoconus screening only in conjunction with other clinical factors, such as a history of eye rubbing, atopic ocular disease and a family history of keratoconus in order to enhance screening effectiveness.”The researchers also mention that keratoconus is primarily a bilateral, asymmetric disorder, supported by their findings that anisoastigmatism and lack of enantiomorphism were found significantly related to keratoconus diagnosis. It is added, however, that the odds ratios for these findings were less pronounced than the odds for high astigmatism. The authors explain that this may be due to anisoastigmatism >1.00D often placing at least one eye in the total astigmatism group of ≥2.00D, which is already a marker for the disease. As a result, anisoastigmatism presence doesn’t offer significant discriminatory power beyond what’s captured by total astigmatism threshold. As well, keratoconus presents with varying astigmatism levels in both eyes, so overall level is a better measure than difference between both.Outside of a research setting, the authors believe that “a practical screening strategy for high school children could involve identifying those with ≥2.00D of astigmatism and assessing them for these additional risk factors. Our findings underscore the importance of comprehensive screening in adolescents with high astigmatism to facilitate early diagnosis and management of keratoconus, potentially improving long-term visual outcomes.”Click here for the journal source. Safir M, Nitzan I, Hanina Y, et al. Keratoconus prevalence in astigmatic adolescents: findings from a nationwide screening setting. Eye (Lond). September 18, 2025. [Epub ahead of print]. This article was developed by the editorial staff in conjunction with experts in the field. In the process, AI may have been among the editorial tools used to meet the goals of human editors, who approved all content.