Visual Acuity & Refractive Converter
Convert Snellen metric (6/6), Snellen Imperial (20/20), LogMAR, Decimal, and approximate dioptric refractive blur equivalent.
Safety Stromal Bed (RSB) Standard
LASIK & Refractive Surgery Suitability Index
Determine candidacy for Custom Blade-Free LASIK, PRK, or Implantable Collamer Lens (ICL) based on corneal thickness, myopia power, and tissue margins.
Interactive Clinical Assessment
Enter clinical parameters below for immediate computerized evaluation. Results update instantaneously.
Healthy adult cornea averages 530 – 550 µm.
Laser ablates approximately 14 µm of stromal tissue per diopter of myopia.
Consultant Clinical Insight
"High-precision ophthalmic diagnostics and proactive screening prevent over 80% of preventable visual impairment. Early detection gives patients the greatest opportunity for spectacle freedom and retinal preservation."
Dr. Praveen Kumar
Consultant Cataract & Refractive Surgeon · Dr. Anil Kumar's Eye Hospital
Clinical Background & Evidence Base
Refractive safety demands adequate residual stromal bed (RSB): RSB = CCT - Flap_Thickness (approx 110 µm) - Ablation_Depth (14 µm per diopter of myopia). The Percent Tissue Altered (PTA) = (Flap + Ablation) / CCT. Safety guidelines mandate RSB ≥ 300 µm and PTA < 40% to eliminate the risk of post-LASIK corneal ectasia.
Clinical Staging Reference
| Classification / Stage | Clinical Interpretation & Care Pathway |
|---|---|
| Ideal LASIK Candidate (RSB ≥ 350 µm, PTA < 35%) | Substantial corneal thickness cushion. Excellent safety profile for custom Femto-LASIK or Contoura Vision wavefront-guided correction. |
| Eligible with Caution (RSB 300 – 349 µm, PTA 35% – 39%) | Moderate tissue reserve. Advanced topography (Sirius/Pentacam) required to rule out posterior elevation or subclinical keratoconus. |
| Borderline Cornea / PRK Candidate (RSB < 300 µm with LASIK) | Cornea is too thin for a lamellar flap. Surface ablation (PRK / Trans-PRK) preserves 110 µm of stromal tissue and provides safe results. |
| ICL / Phakic Lens Recommended (Myopia > -8D or CCT < 480 µm) | Laser ablation inadvisable due to risk of ectasia. Implantable Collamer Lens (EVO+ ICL) offers crystal-clear spectacle freedom without removing corneal tissue. |