If you are researching Contoura Vision and want to understand exactly how much corneal tissue the procedure removes, you are asking the right question. The amount of tissue ablated during any laser eye surgery directly determines whether you qualify, how much safety margin remains in your cornea, and how stable your results will be long-term.
The short answer: Contoura Vision typically removes between 10 and 75 microns of stromal tissue, depending on your prescription. That is a fraction of the cornea’s total thickness — but the precise number matters enormously. This guide from Visual Aids Centre explains the formula surgeons use to calculate tissue removal, why Contoura is considered more tissue-efficient than conventional LASIK, what residual thickness must remain for safety, and how the numbers compare to other procedures.
Key Takeaways
- Contoura Vision removes approximately 12–16 microns of corneal stroma per dioptre of myopic correction — typical total removal ranges from 10 to 75 microns.
- The corneal flap itself accounts for 100–120 microns; the laser ablation occurs beneath it.
- A minimum residual stromal bed of 250 microns must remain after ablation to ensure long-term corneal stability.
- Contoura’s topography-guided approach is more tissue-efficient than conventional LASIK because it corrects only the measured irregularities, not a generic optical profile.
How Much Corneal Tissue Does Contoura Remove?
The amount of tissue removed during Contoura Vision depends almost entirely on your prescription. For a mild myopic correction of –1.00 to –2.00 dioptres, the excimer laser ablates roughly 12 to 30 microns of stromal tissue. For moderate prescriptions around –4.00 to –5.00 D, removal typically reaches 50 to 65 microns. Higher corrections approaching the upper treatable limit of Contoura may require up to 75 microns or slightly more.
To put these numbers in context, the average human cornea is approximately 540 microns thick at the centre. The flap created during the procedure accounts for another 100 to 120 microns. So even in a higher correction, the total tissue affected — flap plus ablation — represents roughly one-third of the cornea’s full thickness. The remaining two-thirds provide the structural integrity your cornea needs for the rest of your life.
The Formula Behind Tissue Removal
Refractive surgeons do not estimate — they calculate. The industry-standard approximation for myopic ablation is known as the Munnerlyn formula. In simplified terms, the depth of tissue removed is proportional to the square of the optical zone diameter multiplied by the dioptre correction. For a standard 6.5 mm optical zone, this works out to roughly 12 to 16 microns per dioptre of myopia corrected.
For example, a patient with –3.00 D of myopia treated over a 6.5 mm zone would have approximately 40 to 48 microns of stroma removed. A –6.00 D correction doubles that to roughly 80 to 96 microns. This is precisely why pre-operative corneal thickness measurement is non-negotiable — it tells the surgeon exactly how much tissue is available to work with before hitting the safety floor.
Contoura Vision adds an additional refinement layer on top of this formula. Because its topography-guided profile corrects micro-irregularities across the corneal surface, the ablation pattern is not uniform — it removes slightly more tissue in some meridians and less in others, resulting in a smoother final surface with fewer higher-order aberrations.
Why Contoura Is More Tissue-Efficient
Conventional LASIK uses a wavefront-optimised or wavefront-guided ablation profile that applies a relatively uniform correction across the treatment zone. Contoura’s topography-guided approach is fundamentally different — it maps 22,000 elevation points on your individual cornea and designs an ablation pattern that addresses only your specific irregularities.
The practical effect is that Contoura often achieves the same (or better) visual outcome while removing marginally less tissue than a standard ablation profile would for the same dioptre correction. This tissue-sparing advantage matters most for patients with moderate-to-high prescriptions or those whose corneal thickness sits closer to the lower qualifying limit. It also preserves more biomechanical strength in the cornea — reducing the long-term risk of ectasia.
The Residual Bed Thickness Rule
No matter how much tissue the laser removes, one number must always be respected: the residual stromal bed (RSB). This is the thickness of untouched corneal stroma remaining beneath the flap after ablation. The widely accepted safety threshold is a minimum of 250 microns, though many surgeons prefer 280 to 300 microns for an extra margin.
Here is how the calculation works in practice. Start with the patient’s central corneal thickness — say 530 microns. Subtract the flap thickness (110 microns). Subtract the planned ablation depth (60 microns for a –4.50 D correction). The residual bed is 530 – 110 – 60 = 360 microns — well above the safety floor. If you want to understand the maths in detail, our guide on calculating residual thickness after LASIK walks through every step.
When the RSB calculation falls below the safe threshold, the surgeon will either recommend a thinner flap, reduce the optical zone diameter, or advise a flapless procedure like SMILE Pro — which preserves more stromal tissue by eliminating the flap entirely.
How Contoura Compares to Other Procedures
In terms of tissue removal, Contoura and standard Femto LASIK ablate a similar volume of stroma for the same prescription — the difference is in the ablation pattern (topography-guided vs wavefront-optimised), not the total depth. Where Contoura gains its edge is in the quality of the optical surface it produces, which translates to sharper vision and fewer night-time disturbances.
SMILE and SMILE Pro work differently. Instead of ablating tissue with an excimer laser, they extract a pre-shaped lenticule from within the stroma through a small incision. The amount of tissue removed is comparable for the same dioptre correction, but because no flap is created, more of the anterior stroma remains intact.
For patients concerned about whether their cornea can tolerate the tissue removal, the key factor is not the procedure name — it is the total tissue budget: starting thickness minus flap minus ablation must leave an adequate residual bed. Your surgeon calculates this during the pre-operative corneal topography assessment.
Who May Not Qualify Due to Corneal Thickness?
Patients with corneas thinner than approximately 480 to 490 microns, or those with high prescriptions that would push the residual bed below 250 microns, may not be suitable for Contoura Vision. Similarly, patients with early or suspected corneal irregularities such as forme fruste keratoconus require extra caution — even if the thickness numbers technically work, the biomechanical quality of the tissue may not support safe ablation.
In these cases, alternatives such as SMILE Pro, ICL (implantable collamer lens), or PRK are considered. The only way to know where you stand is a thorough pre-operative evaluation, which includes pachymetry, tomography, and a detailed assessment of your corneal shape and health.
Conclusion
Contoura Vision removes between 10 and 75 microns of corneal stroma, depending on your prescription — roughly 12 to 16 microns per dioptre of myopia corrected. The procedure’s topography-guided approach makes it one of the more tissue-efficient forms of laser vision correction available, producing a smoother optical surface while preserving corneal strength. The critical safety check is the residual stromal bed, which must remain above 250 microns after the flap and ablation are accounted for. If you are considering LASIK eye surgery in Delhi and want to know exactly how your corneal numbers stack up, book a consultation at Visual Aids Centre for a complete assessment.
Frequently Asked Questions (FAQs)
How many microns does Contoura remove per dioptre?
Approximately 12 to 16 microns of corneal stroma per dioptre of myopic correction, depending on the optical zone diameter used during treatment.
Is Contoura Vision safer for thin corneas than standard LASIK?
Contoura’s topography-guided ablation can be marginally more tissue-efficient, but the same residual bed safety rules apply. Patients with very thin corneas may still need a flapless alternative like SMILE Pro.
What is the minimum corneal thickness needed for Contoura Vision?
There is no single universal cut-off, but most surgeons require at least 480 to 500 microns of central corneal thickness to ensure a safe residual stromal bed after flap creation and laser ablation.
Does Contoura remove more tissue than SMILE Pro?
For the same dioptre correction, the volume of tissue removed is comparable. However, SMILE Pro does not create a flap, so more anterior stroma remains intact — giving it an advantage in patients where corneal strength is a concern.
Can Contoura be done if I have a high prescription?
Contoura can treat myopia up to approximately –8.00 D and astigmatism up to –3.00 D, provided your corneal thickness allows adequate residual bed after ablation. Higher prescriptions require more tissue removal and therefore need thicker corneas.
What happens if too much cornea is removed?
Excessive tissue removal weakens the cornea structurally, potentially leading to post-LASIK ectasia — a progressive bulging that degrades vision. This is precisely why the 250-micron residual bed rule exists and why accurate pre-operative measurements are essential.
