Why monitoring matters
Keratoconus that progresses unchecked thins and scars the cornea, reduces the vision achievable with lenses, and in a minority of patients ends in corneal transplantation. Cross-linking prevents that, but it is indicated for progressing disease, and progression is invisible to the patient until vision changes, by which time some cornea has been lost. Regular measurement catches the change while it is small. Monitoring also protects patients from unnecessary treatment: an adult whose maps are unchanged over two years does not need cross-linking.
What is measured
- Steepest corneal curvature (Kmax), the most used single measure of progression
- Thinnest corneal thickness
- Back surface elevation, which often changes earliest
- Indices that summarize irregularity across the cornea
- Refraction and best corrected vision, which show the practical effect
Each scan is compared with all previous ones, not only the last, so a slow trend is not lost in measurement noise. Progression is defined by change beyond the instrument's known variability.
The schedule
Patients under 25, or of any age with a recent change, are measured every three to six months. Adults with two years of stable maps move to annual checks. After cross-linking, tomography at six and twelve months confirms the treatment has held, then continues annually, because a small proportion of eyes progress again years later. Pregnancy, new eye rubbing, or a change in prescription prompts an earlier check.
Monitoring and your lenses
Specialty lenses fit a specific corneal shape. As the cornea changes, or settles after cross-linking, the fit changes, and a lens that once vaulted the cornea may start to touch it. Monitoring visits are combined with lens checks, and the lens is refitted from the new maps when needed.
Contact lenses before scans
Rigid and scleral lenses flatten the cornea temporarily and can hide progression. They are typically left out for two to three weeks before a monitoring scan, soft lenses for a few days. Wear glasses in the meantime, and tell the team if you were unable to.
Is this right for your eyes?
Nothing on this page is a diagnosis. Whether this is the right choice for you is decided by a full examination at one of our 4 offices: Pasadena, Huntington Beach, Woodland Hills and Beverly Hills.
About this content: This page was written with the assistance of AI tools and reviewed for medical accuracy by Dr. Bavand Youssefzadeh, DO. It is general information, not medical advice, and does not replace an eye examination. Individual results vary. Read our medical disclaimer.
