Diagnostic Devices Explained (Topography, Pentacam, iDesign)

Expect a lot of measurements—that’s a good thing. Accurate data makes safer, sharper outcomes.

Topography and tomography

• Topography maps the front surface of the cornea.
• Tomography (e.g., Pentacam) creates a 3D picture of the cornea, measuring both front and back surfaces and thickness.
• Why it matters: Detects irregularities and early ectasia risk that can rule out LASIK in favor of safer options.

Pachymetry (thickness)

Measures corneal thickness to ensure enough tissue remains after treatment. This protects structural integrity.

Wavefront aberrometry (iDesign/others)

Captures optical imperfections beyond simple prescriptions (higher‑order aberrations). Helps tailor guided treatments.

Tear film and ocular surface testing

Assesses dryness and gland function. A healthy surface improves visual quality and comfort.

How long does this take?

Most clinics complete measurements within an hour, often less. Bring your lens holiday instructions so your cornea is in its natural shape.

What to ask

• Are my measurements consistent across devices and visits?
• Any signs that make LASIK less ideal—and if so, what’s safer?

Bottom line: Good data drives good decisions. Expect to learn a lot about your eyes.