Detecting keratoconus: from clinical signs to advanced corneal tomography

As eye care practitioners, myopia management is an integral part of our standard of care.¹  However, myopia is not the only condition requiring our attention, and our role places us in a unique position to detect early signs of keratoconus in pediatric populations. While our focus might often be on monitoring refractive error and axial elongation, changes in astigmatism, corneal signs and visual acuity may also indicate developing corneal ectasia. Keratoconus has also been associated with axial myopia, so the two conditions may coexist. Early detection of keratoconus is particularly important in younger patients when it comes to keratoconus as they face a higher risk of rapid structural change,²  and timely intervention can help preserve vision.

Traditionally, keratoconus detection has relied on changes in refraction, slit lamp signs and corneal topography. Corneal tomography, a tool which may already be in the clinic for orthokeratology fitting, can help to identify subtle abnormalities before the development of obvious clinical signs. In this article, we explore the latest recommendations for detecting keratoconus, the role of corneal tomography in identifying early disease, and how advances in diagnostic technologies and algorithms can support earlier diagnosis.

The 2026 Global Consensus on Keratoconus and Ectatic Diseases¹ defines keratoconus as a primary, bilateral and typically asymmetrical corneal ectasia characterised by progressive steepening and thinning centred around the cone apex.

Four major diagnostic criteria were identified:

1. Abnormal steepening of the anterior and/or posterior corneal surfaces.
2. An abnormal corneal thickness profile.
3. Classic slit-lamp biomicroscopy signs (Fleischer's Ring, Vogt's Striae, Munson's Sign, localized corneal thinning and apical scarring).
4. Reduced corrected distance visual acuity (CDVA).

The consensus emphasises that slit-lamp signs and reduced CDVA are not mandatory for diagnosis, particularly in the early stages of keratoconus, in which case these clinical signs may be absent. 

The 2026 Global Consensus places particular importance on early keratoconus detection in children and adolescents, as the disease can progress more rapidly and aggressively in younger patients, increasing the risk of permanent visual impairment.² Diagnosis is often delayed until a reduction in corrected distance visual acuity (CDVA) becomes apparent, despite early disease potentially presenting with good vision and few clinical signs.³  

The consensus recommends further assessment (beyond clinical history, visual acuity and slit-lamp examination) in children aged 6–18 years presenting with more than 2.00 D of astigmatism. This recommendation is particularly relevant to primary eye care, where children with significant but correctable astigmatism may otherwise be managed with spectacle correction alone. 

Corneal topography has traditionally been used to identify characteristic patterns of keratoconus, including inferior steepening, asymmetric bow-tie patterns and irregular astigmatism. However, conventional Placido disc-based topography primarily evaluates the anterior corneal surface. This limits its ability to detect changes involving the posterior cornea or the distribution of corneal thickness, both of which may be the earliest signs of corneal ectasia.

Corneal tomography provides a more comprehensive three-dimensional assessment by evaluating:

• Anterior corneal curvature and elevation.
• Posterior corneal elevation
• .Corneal thickness and its spatial distribution.
• The location of the thinnest corneal point.
• Changes in pachymetric progression from the centre towards the periphery.

Scheimpflug imaging systems, such as the OCULUS Pentacam®, combine these measurements to provide a more detailed assessment of corneal structure. 

The 2026 Global Consensus supports this multimodal approach to diagnosis, incorporating tomography and, where available, anterior segment optical coherence tomography (AS-OCT) and corneal biomechanical assessment.

A systematic approach to interpreting corneal tomography allows clinicians to avoid missing subtle or early ectatic disease. A 5-step evaluation system can be used:

1. Posterior corneal elevation: Examine posterior elevation first. Subtle posterior surface changes and localized elevations often appear before any noticeable anterior curvature changes. 
2. Anterior corneal elevation: Abnormal anterior elevation may accompany the progressive steepening associated with keratoconus. Comparing anterior and posterior elevation helps identify whether structural changes are occurring in corresponding regions.
3. Pachymetry and spatial thickness distribution: Keratoconus is associated with focal thinning and an abnormal thickness profile. The location of the thinnest point, particularly when displaced from the corneal centre and corresponding to abnormal elevation, may provide further diagnostic insight.
4. Interocular asymmetry: Although keratoconus is generally bilateral, it is frequently asymmetrical.⁴  Comparing both eyes can help identify subtle abnormalities that might otherwise be overlooked.
5. Anterior Corneal Curvature (Topography): Inferior steepening and irregular astigmatism are useful findings, but curvature alone may not adequately characterise the earliest stages of disease.

Considering these findings together provides a more comprehensive assessment of corneal structure than any individual measurement. For example, a relatively normal anterior curvature map does not necessarily exclude early keratoconus when posterior elevation or pachymetric abnormalities are present.

BAD-D v4 stands for the Belin/Ambrósio Display version 4. It is an advanced diagnostic algorithm embedded within Scheimpflug corneal tomography (such as in the OCULUS Pentacam). BAD-D v4 incorporates an optimised logistic regression algorithm using 11 variables, including patient age, corneal astigmatism, pachymetric measurements, posterior corneal elevation and higher-order aberrations. By combining these parameters, the algorithm aims to improve differentiation between normal corneas and those with clinical or subclinical (subtle) ectatic abnormalities.

In a 2024 multicentre retrospective study, the BAD-D v4 algorithm was evaluated using data from 3,886 eyes of 3,351 patients across 26 international centres.⁵  The study included healthy corneas, eyes with clinically diagnosed keratoconus, and cases of very asymmetric ectasia, where one eye had established ectasia while the fellow eye did not appear to have ectasia. 

BAD-D v4 performed exceptionally well, outperforming its previous version (BAD-D v3) and matching complex artificial intelligence models like the Pentacam Random Forest Index (PRFI) across all tested groups. AUROC (Area Under the Receiver Operating Characteristic Curve) is a standard statistical metric used to evaluate the overall accuracy and discriminating power of a diagnostic test or algorithm. When AUROC = 1.0, this indicates that the test differentiates every single normal case from a diseased case with 100% accuracy. The diagnostic performance of BAD-D v4 across the different study groups was as follows.

• Clinically established keratoconus: Achieved near-perfect diagnostic accuracy with an AUROC score of 0.998.
• Asymmetric ectasia cases: Effective at distinguishing healthy corneas from all categories of ectatic disease with an AUROC score of 0.966.
• Subclinical (normal-topography) ectasia: Demonstrated a major leap in detecting subtle ectasia in eyes with completely normal front-surface topography, scoring an AUROC of 0.858 (compared to 0.789 for version 3).

In short, BAD-D v4 delivered AI-level diagnostic precision without requiring additional steps or changes to existing clinical workflows. 

Keratoconus management should be individualised according to disease severity, progression and visual needs. Key recommendations from the 2026 Global Consensus include:

• Behavioural and medical management: Discourage eye rubbing and manage ocular allergies to minimise irritation and potential disease progression.
• Disease stabilisation: Corneal cross-linking (CXL) is the primary intervention for progressive keratoconus. Early identification in children allows for timely intervention with CXL, which may be considered at diagnosis without waiting for documented progression.³
• Visual rehabilitation: Spectacles or soft contact lenses may be suitable for mild disease, while rigid gas-permeable, hybrid or scleral lenses can improve vision in more advanced cases.
• Surgical intervention: Corneal reshaping procedures or keratoplasty may be considered when adequate vision cannot be achieved with optical correction, particularly in advanced disease.

Myopia management is a routine part of primary eye care, and so practitioners have an important opportunity to look beyond refractive error and axial elongation to identify other conditions affecting eye health. Keratoconus is particularly important to detect early, given its potential for rapid progression in younger patients and the urgency needed for intervention to preserve vision. Advances in corneal tomography and diagnostic algorithms, alongside updated screening recommendations, provide valuable tools for identifying subtle abnormalities before more obvious clinical signs develop.