Diagnostic Technology Explained: How Corneal Topography and OCT Scans Enable Early Detection of Keratoconus

“We need to run some scans to check your corneas properly.” 

If you’ve been told this during an eye examination, you might wonder what these scans actually do and why they’re necessary. The answer is simple – modern diagnostic technology can detect keratoconus years before it becomes obvious to the naked eye, giving you options that simply don’t exist once the condition has advanced. 

At Bellamy Eyecare in Leicester and Irthlingborough, we use two key technologies for keratoconus detection – corneal topography and OCT scanning. These aren’t complicated procedures – they’re quick, painless and remarkably revealing about what’s happening with your corneas. 

Understanding how these scans work helps you appreciate why they’re so valuable for anyone with vision changes, family history of keratoconus or risk factors like chronic hay fever. 

Why Regular Eye Tests Miss Early Keratoconus 

During a standard eye test, your optician examines your eyes using a slit lamp – essentially a microscope with a bright light. They can see obvious corneal problems like scars or advanced bulging but early keratoconus? It’s invisible. 

Your cornea might have started thinning and bulging slightly but unless the changes are dramatic, they won’t show up on visual examination. By the time keratoconus is obvious to the naked eye, significant damage has already occurred. 

Think of it like trying to spot a small dent in a car bonnet by looking at it from across the street. You might notice a massive dent, but a subtle one? You’d need to get closer, maybe run your hand over it, or take measurements to detect it properly. 

That’s where diagnostic technology comes in – it takes precise measurements that reveal changes impossible to spot visually. 

Corneal Topography: Mapping Your Cornea’s Shape 

Corneal topography creates a detailed map of your cornea’s surface, showing its shape, curvature and any irregularities. 

How Corneal Topography Works 

You rest your chin on a support and look at a target inside the machine. The device projects a series of rings onto your cornea – imagine looking at a target or bullseye reflected in your eye. A camera captures how these rings reflect off your corneal surface. 

Normal corneas reflect the rings in a regular, even pattern. Keratoconic corneas distort the rings, showing irregular patterns that reveal exactly where and how much the cornea has deformed. 

The whole process takes about 30 seconds. No contact with your eye, no discomfort, just looking at a target while the machine works. 

What the Maps Show 

The scan produces colour-coded maps showing corneal curvature. Think of it like a weather map with different colours representing different temperatures – except here, colours represent how steep or flat different areas of your cornea are. 

Normal corneas show relatively symmetrical patterns with gradual colour changes – usually warmer colours (reds and oranges) in the centre where the cornea is naturally steeper, cooling to blues and greens towards the edges. 

Keratoconic corneas show distinctive patterns: 

• A concentrated area of steep curvature (hot spot) where the cone is forming. 

• Asymmetry between upper and lower cornea. 

• Irregular patterns that don’t follow the normal bow-tie shape. 

Even very early keratoconus creates subtle pattern changes that experienced optometrists can spot on these maps. 

Why Topography Catches Keratoconus Early 

Corneal topography detects shape changes long before they cause obvious symptoms. Your vision might still be correctable with glasses and your cornea might look normal under the slit lamp, but topography reveals the truth. 

At Bellamy Eyecare, we use topography for: 

• Anyone with unexplained vision changes or frequent prescription updates. 

• People with family history of keratoconus. 

• Patients with risk factors like allergies or chronic eye rubbing. 

• Regular monitoring of diagnosed keratoconus to track progression. 

OCT Scanning: Measuring Corneal Thickness 

While topography maps your cornea’s front surface, OCT (Optical Coherence Tomography) scans see through your cornea, measuring its thickness at thousands of points. 

How OCT Works 

OCT uses light waves to create cross-sectional images of your cornea – similar to how ultrasound uses sound waves but with much higher resolution. The scan measures how long light takes to reflect back from different layers within your cornea, building a detailed picture of its structure. 

Again, it’s completely painless. You look at a target while the machine scans your eye. Takes less than a minute. 

What OCT Reveals 

OCT creates thickness maps showing exactly how thin or thick your cornea is at every point across its surface. 

In normal eyes, corneal thickness is relatively even, typically around 540-560 micrometres (about half a millimetre) in the centre, slightly thicker toward the edges. 

In keratoconic eyes, OCT reveals: 

• Focal thinning where the cone is developing. 

• Asymmetric thickness between upper and lower cornea. 

• The precise location of the thinnest point. 

• How thickness changes across the entire corneal surface. 

This information is crucial because keratoconus is fundamentally a thinning disease. Shape changes on topography happen because the cornea has thinned and weakened. 

Why Thickness Matters 

OCT thickness measurements serve several vital purposes: 

• Early detection – thinning often begins before obvious shape changes appear on topography. OCT can catch keratoconus at its earliest stage. 

• Progression tracking – by comparing thickness maps over time, we can see whether your keratoconus is stable or progressing. This determines whether you need cross-linking. 

• Treatment planning – corneal thickness affects what treatments are suitable. Cross-linking requires a minimum thickness. Specialist contact lens fitting depends on understanding your cornea’s structure. 

• Safety screening – some corneas are naturally thin without having keratoconus. OCT helps distinguish normal thin corneas from pathological thinning. 

How These Technologies Work Together 

Topography and OCT complement each other perfectly. 

Topography shows what’s happening – the shape changes and irregularities characteristic of keratoconus. 

OCT shows why it’s happening – the thinning that causes those shape changes. 

Together, they provide a complete picture: 

• Where your cornea is abnormal 

• How severe the changes are 

• Whether progression is occurring 

• What treatments might help 

At Bellamy Eyecare, we use both technologies as part of our keratoconus assessment and monitoring process when clinically appropriate. Neither test alone tells the complete story, but combined, they’re remarkably powerful. 

What Happens During Your Scans 

Understanding the process helps if you’re nervous about diagnostic testing. 

The Appointment 

Both scans happen during your comprehensive eye examination. After discussing your symptoms and checking your vision, we move to the diagnostic equipment. 

For topography, you rest your chin and forehead against supports, keeping your head still while looking straight ahead at a target. The machine captures images in seconds. You might need to blink to refresh your tear film between measurements, then hold your eyes open briefly for each scan. 

For OCT, the setup is similar – chin rest, look at the target, hold still for a few seconds. The machine scans automatically while you’re looking at the fixation point. 

Total time for both scans? Usually under five minutes. 

What You’ll Experience 

• No eye drops required (though sometimes we use them for other parts of the examination). 

• No contact with your eyes. 

• No discomfort or pain. 

• Bright lights to look at, but not uncomfortable. 

• Need to keep eyes open briefly, which can feel odd if you have dry eyes. 

That’s honestly it. People are often surprised how quick and simple the process is, especially given how much information we gain. 

Getting Your Results 

Unlike blood tests where you wait days for results, these scans provide immediate information. We can show you the maps and images right away, explaining what they reveal about your corneas. 

If the scans show keratoconus, we’ll explain: 

• What stage it’s at. 

• Whether it appears stable or progressing. 

• What treatment options suit your situation. 

• What monitoring schedule makes sense. 

If scans are normal but you have risk factors, we’ll recommend appropriate monitoring intervals to catch any future changes early. 

Why Early Detection Changes Everything 

The real value of this diagnostic technology lies in what you can do with early information. 

If keratoconus is caught at mild stage, cross-linking can often halt progression completely. Simple RGP or even soft lenses might provide excellent vision, giving you years or decades of stable, functional sight ahead. 

Caught at moderate stage, cross-linking is still highly effective at stopping progression. Specialist lenses usually achieve good vision and your options remain plentiful for managing the condition successfully. 

But if keratoconus is only diagnosed at advanced stage, the picture changes dramatically. Treatment options become limited, lens fitting grows complex and you might face the possibility of transplant if lenses don’t work. Everything becomes much more challenging to manage. 

Technology that detects keratoconus early literally changes the trajectory of the condition. It’s not just about diagnosis – it’s about intervention while you still have maximum options. 

Who Should Have These Scans? 

At Bellamy Eyecare, we recommend topography and OCT for anyone experiencing frequent prescription changes (more than once yearly), vision that won’t quite come clear with glasses, increasing light sensitivity or distortion and ghosting of images. 

If you have risk factors like family history of keratoconus, chronic allergies or hay fever, a history of frequent eye rubbing, or connective tissue disorders, these scans make sense even without obvious symptoms. 

And if you’ve been diagnosed with keratoconus, have had suspicious findings on previous scans, or have a high-risk profile even with normal current results, regular monitoring with these technologies is essential for tracking any changes. 

These aren’t routine tests we do on everyone – your optician doesn’t need topography to check if you need reading glasses. But for anyone with keratoconus concerns, they’re invaluable. 

The Bellamy Difference 

Having advanced diagnostic equipment matters but knowing how to interpret it matters more. 

Corneal topography and OCT generate enormous amounts of data. The skill lies in knowing which patterns indicate genuine problems versus normal variations, understanding which findings warrant intervention versus monitoring and explaining complex results in ways that actually make sense. 

We’ve been using these technologies for keratoconus diagnosis and management for more than 10 years. That experience means we catch subtle early changes that less experienced practitioners might miss, we track progression accurately over time and we explain your results clearly without overwhelming jargon. 

Our 45-minute comprehensive examinations provide time to run scans properly, review them carefully with you, and discuss what they mean for your specific situation. 

Taking Action 

If you’re concerned about keratoconus – whether you’ve noticed symptoms, have family history, or want screening because you’re at risk – having proper diagnostic assessment gives you clarity and options. 

Without topography and OCT, you’re relying on visual examination that can easily miss early changes. With them, you have precise, objective measurements that reveal exactly what’s happening with your corneas. 

Early detection genuinely matters. The sooner we identify keratoconus, the more options we have for managing it successfully and protecting your long-term vision. 

Contact us to arrange a comprehensive assessment including corneal topography and OCT scanning at either our Leicester or Irthlingborough practice. 

Leicester Practice
156 Fosse Road North, Leicester, LE3 5ES
Tel: 0116 2531750 

Irthlingborough Practice
24 High Street, Irthlingborough, NN9 5TN
Tel: 01933 653226 

Frequently Asked Questions About Keratoconus Diagnostic Technology 

1. What is corneal imaging and why is it important for keratoconus?

Corneal imaging uses advanced ophthalmology instruments like topography and OCT to perform a detailed analysis of your cornea’s shape and thickness. This improves diagnostic accuracy, allowing specialists to detect keratoconus long before symptoms like blurring or glare begin to affect your quality of life. 

2. How does pachymetry help detect keratoconus earlier?

Pachymetry measures corneal thickness, which is crucial because keratoconus involves progressive thinning. Combined with OCT imaging, it allows precise evaluation of corneal structure, helping specialists identify early disease progression and plan appropriate interventions. 

3. Can keratoconus be mistaken for astigmatism?

Yes – early keratoconus often appears similar to astigmatism, especially when vision changes frequently. However, advanced analysis using topography and OCT reveals irregular surfaces and steepening patterns that standard eye tests can miss, improving diagnostic accuracy. 

4. What role do OCT scans play in keratoconus management?

OCT plays a vital role in keratoconus management by providing high-resolution imaging of the cornea. It enables detailed evaluation of the epithelium, thickness (pachymetry), and structural biomechanics, helping specialists monitor keratoconus progression and guide treatment decisions. 

5. Are these scans necessary for keratoconus patients who already wear contact lenses?

Yes. Even if you wear contact lenses, regular imaging is essential for monitoring disease progression and ensuring long-term eye health and stability. It also supports better contact lenses fitting, including scleral lenses that vault over the sclera for improved vision and comfort. 

6. What treatments might be recommended after early detection?

Early detection opens up more keratoconus treatment options, including collagen cross-linking (CXL), which uses riboflavin to strengthen the cornea and slow degeneration. Other options may include intracorneal ring segments, specialist lenses, or in severe cases, procedures like keratoplasty. 

7. How do specialists assess keratoconus severity and stages?

Specialists use advanced imaging tools, indices, and elevation maps (including Placido-based systems) to assess severity, stages, and progression. This detailed analysis allows a tailored approach to care based on each patient’s condition and visual acuity. 

8. Is keratoconus linked to children or family members?

Yes, keratoconus can affect children and often runs in families. If you have affected family members, early evaluation with diagnostic instruments is strongly recommended to detect early development and begin appropriate keratoconus care. 

9. Are procedures like LASIK safe for keratoconus patients?

Procedures like LASIK are generally not suitable for keratoconus patients because they can worsen corneal instability. Proper evaluation using advanced imaging ensures safe treatment decisions and identifies suitable candidates for alternative techniques. 

10. Where can I get keratoconus diagnostic scans in Leicester or Irthlingborough?

You can visit a specialist keratoconus care centre like Bellamy Eyecare in Leicester or Irthlingborough, where advanced imaging, expert analysis, and a dedicated team of specialists provide accurate diagnosis, personalised advice and ongoing support. 

 

Written by Alan Bellamy, principal optometrist at Bellamy Eyecare in Leicester and Irthlingborough. Alan has over 25 years of experience using advanced diagnostic technology to detect and manage keratoconus.