CAS_Calc

CAS IOL Calc calculates the power of an intraocular lens. It is written for ophthalmic surgeons performing cataract surgery, and for anyone working with ocular biometry. FOUR ENGINES, SIDE BY SIDE • CAS Rx — the engine for routine work. Gaussian optics with a thick corneal model; the machine-learned part is the effective lens position and nothing else. Toric, suitable for all eyes. • CAS classic — the original Castrop formula with the C/H/R constant triplet. It calculates what the web version at iolcon.org calculates. • CAS AI — pure machine learning without any optical calculation, a feasibility study and a cross-check. Spherical only, with hard limits. • SRK/T — the 1990 formula, included as a yardstick because the comparison has been asked for repeatedly. We do not recommend it for clinical use. Where the four diverge, that divergence is information in itself. TWO MODES • Simple — one eye, the short form, the result directly below it. The corneal refinements sit behind a switch. • Full — both eyes in turn, with side comparison, a note field, QR import and a printable calculation sheet: one A4 page, both eyes side by side, with the inputs, the constant footing, the power table, the axis sketch, every note and the scope and limitations of the engine. FOUR MODULES The menu "Module" under the title switches between four calculation paths; the case in the main calculation stays as it is. • IOL calculation — the routine case, the lens in the capsular bag. • Add-on IOL — the supplementary lens in front of a lens already implanted, from the refraction and the pseudophakic anterior chamber depth. • IOL exchange — the replacement lens for a pseudophakic eye; the cylinder comes from the refraction, the radii run alongside as a cross-check. • Secondary implantation — the eye without capsular support, with the lens position set by hand. Each module has its own inputs, its own note field and its own printable sheet. WHAT THE APP DOES • Toric calculation with axis rose, misalignment and residual refraction • Result table with spherical equivalent and the whole lens (sph/cyl) • Refined cornea: posterior surface, thickness, tomographic cylinder • Corneal spherical aberration, derived from the radii and the asphericity (Q or e) and calibrated to the CASIA2 • Post-refractive corneas via funny cornea and the posterior radius • Read biometry from the QR code on the device printout, through the camera or from an image or PDF; the code format is documented at https://iolcon.org/download/LPCM_QR-Import.pdf • Warnings instead of silent extrapolation: percentile limits on every field, eye rarity score, side comparison of the pair, a note when keratometric and tomographic cylinder diverge • Lens catalogue with optimised constants; unknown lenses via the A constant • Full manual inside the app, in three languages • German, English, Italian PRIVACY Everything is calculated on the device. No account, no sign-in, no network connection, no data collection. There are no fields for a name or a date of birth. The report carries no patient identifier, and nothing entered survives closing the app. IMPORTANT CAS IOL Calc is not a medical device. It is for investigational use. Every clinical decision remains with the treating physician. The models were trained on IOLMaster 700 measurements; for other biometers a slight loss of accuracy cannot be excluded. The limitations of each engine are shown permanently in the result panel, on the printout and in detail in the manual. The basis is the Castrop formula: Langenbucher A, Szentmáry N, Cayless A, Weisensee J, Wendelstein J, Hoffmann P. Considerations on the Castrop formula for calculation of intraocular lens power. PLoS One 2021;16(6):e0252102.