Plan the incision and the toric phakic lens together.

Enter the refraction, the keratometry and your own surgically induced astigmatism. ODISEO tells you where to enter, which cylinder to order and how far to rotate the lens, on the platform you actually have.

Four lens platforms on one screen. EyeCryl, IPCL, Intralens and EVO, each with its own catalogue.
Nothing leaves your browser. No account, no upload, no stored patient data.
Free for clinical use. Prints a theatre sheet and the full arithmetic for the record.

Before you start

ODISEO is a planning aid for qualified eye care professionals. Please read the conditions of use once; this browser will remember that you accepted them.

By continuing you confirm that you have read these conditions, that you accept them, and that you are a qualified eye care professional using this tool for your own clinical practice.

Remembered in this browser only.

ODISEO toric planning

Surgeon

Patient

Patient ID

Date of surgery

Lens

Your SIA D

Cylinder notation

Vertex distance mm

Incisions you can use Temporal Superotemporal Superior

OD · Right eye

Sphere D

Cylinder D

Axis °

K1 flat D

K1 axis °

K2 steep D

K2 axis °

ACD mm

OS · Left eye

Sphere D

Cylinder D

Axis °

K1 flat D

K1 axis °

K2 steep D

K2 axis °

ACD mm

ODISEO toric planning

Patient

Name

Identity document

Date of birth

Date of surgery

Surgeon

These appear on the theatre sheet, where identifying the patient and the eye is the point. Everything you type stays in this browser's memory while the page is open, is never written to browser storage, and is never transmitted. Printing or sharing the sheet is your act and your responsibility.

Each eye holds its own values. Both are planned, both print.

Print

The theatre sheet is always page one: patient, eye, lens, wound, rotation. Each eye's calculations then start on their own page, so you can separate them physically or print them alone.

Refraction

Sphere D

Cylinder D

Axis °

Vertex distance mm

Manifest refraction at the vertex distance you measured it. Switching the toggle transposes what is already typed.

Biometry

K1 D

@ °

K2 D

@ °

ACD mm

WTW mm

CCT mm

ACD is internal, endothelium to anterior lens. K1 is the flatter meridian. White to white and pachymetry ride on the sheet for the order; neither enters the astigmatism arithmetic and neither sizes the lens.

Lenses available to you

Tick what you can actually order. Click a name to make it the one shown in detail; the rest appear in the cross-platform table. The chip says how well each is characterised against real reports, not how good the lens is.

Axis grid °

Cyl step D

Cyl max D

Cyl floor D

Selection

Incision

Your SIA D

Temporal, horizontal Superotemporal Superior Any meridian

Enter the SIA you use for this incision, as every toric calculator asks. It is applied as flattening at the wound meridian, the same at any meridian you allow. Use your vector mean (centroid) if you have it; the mean of magnitudes overstates the effect.

Advanced SIA model

Epsilon °

SIA scatter SD D

SIA model

Superior SIA D

Superior epsilon °

Leave these alone for the standard calculation. Epsilon tilts the SIA vector away from exactly orthogonal to the wound (Kamiya 2021 measured −8° temporal, +1° superior). Scatter is the eye-to-eye SD of the SIA vector per component (Kamiya 2021: about 0.5 D); above 0 the wound is chosen on the residual expected under that scatter. The by-site model sweeps SIA from the value above at a temporal wound to the superior pair (Kamiya: 0.23 D temporal, 0.47 D superior).

Check an existing proposal

Their cyl D

Their axis °

Their incision °

Type the lens a manufacturer already proposed and the wound you were going to use. The comparison gains a row showing what that plan actually leaves behind. Leave blank to hide it.

Model

Plane transfer

d mm

Tau

Lambda

Move the wound only if it gains at least, D

Eta0 °

Drift m

d is the distance from the corneal vertex to the plane of the lens. It is set for each platform from the ACD you enter and can be overridden here. Lambda, eta0 and m weight the rotation term of the objective. The threshold keeps you on your usual horizontal wound unless moving it is worth at least that much.

OD

not planned yet

OS

not planned yet

Plan for OD

Incision at

–

degrees, –

Lens cylinder

–

D, lens plane

Label axis

–

manufactured

Seat at

–

rotate –

Residual

–

D calculated

–

The lens to order

The same eye on each platform


Platform	Wound	Lens SE	Cyl	Axis	Label	Turn	Residual	J

In the eye how the lens arrives and where it has to end

The vector picture doubled-angle plane, where the whole method lives

Meridian sweep what every possible incision would leave behind

residual astigmatism J score horizontal wound shaded bands are the arcs you marked reachable

The steps in the curve are the catalogue. Residual jumps whenever moving the wound pushes the required cylinder across a 0.50 D boundary, which is why the best meridian is rarely the steep one and almost never obvious.

Against the alternatives


Plan	Incision	Cyl	Seat	Rot	Residual	J

Cylinder options at the recommended incision

Residual in both cylinder forms, because the sign convention is where toric orders go wrong. The two columns describe the same eye. The highlighted row is what ODISEO selects.
Lens cyl	Seat at	Label	Rot	Residual +cyl	Residual −cyl	J

Spherical power vergence estimate, confirm with the manufacturer


Lens SE	Residual SE, spectacle plane	Residual SE, corneal plane

Read a report

Drop a PDF here, or click to choose one.

Reads the text layer of a manufacturer calculator report or a biometer printout and offers the values it recognises. Nothing is uploaded: the file is parsed in this browser and discarded. Fields it fills are highlighted and must be checked against the document before you order. Reports that are screenshots rather than text are refused rather than guessed at.

Worked arithmetic for this eye

One calculation instead of two.

A toric phakic lens is usually chosen first and the incision decided afterwards. ODISEO treats the two as a single problem, because the incision changes the astigmatism the lens has to correct.

The refraction is taken to the cornea
Each principal meridian of the spectacle refraction is referred to the corneal plane by back vertex distance. The astigmatism is then handled as a vector, so magnitude and axis are never treated separately.
Your incision is added as a vector
An incision flattens the meridian it sits on. The surgically induced astigmatism you enter is added at that meridian, which gives the astigmatism the eye will actually present to the lens after surgery.
The lens is chosen from the real catalogue
The cylinder needed at the lens plane is worked out by vergence along each meridian, then matched to the cylinder steps and label axes the manufacturer really makes. The rotation needed from the label axis is part of the result.
Every reachable incision is compared
The same calculation is repeated for each incision meridian you are willing to use. The plan shown is the one with the lowest calculated residual, with a small penalty for plans that need more rotation. If moving the wound gains less than a threshold you set, the plan stays on your usual incision.

Every plan reports three residuals: the standard calculation with no incision effect, the standard calculation with your SIA, and the ODISEO plan. When all three agree, it says so.

The arithmetic, briefly

Each principal meridian of the spectacle refraction is referred to the corneal plane by back vertex, F = P / (1 − vP). The resulting astigmatism R is carried as a power vector in the doubled-angle plane. An incision at φ flattens φ and steepens φ + 90 + ε, so its summated vector mean is added there, giving the target T = R + SIA. The lens cylinder required at the lens plane is |T| / τ, quantised to the platform catalogue, and its axis must end at the meridian of T, reached by rotating from the nearest manufactured label axis. The objective is J = |residual| + λ · 2τc · sin(η) with η = η₀ + m|ρ|, minimised over the meridians marked reachable.

Residuals are the vector difference between the astigmatism the eye will present and the correction delivered at its achieved axis, so a plan whose lens axis misses the target meridian is penalised correctly rather than by magnitude alone. For a pure misalignment this reduces to 2C·sin θ, the Langenbucher relation.

A phakic lens corrects the refraction, not the cornea, so it also neutralises lenticular and posterior corneal astigmatism. That is why the target meridian follows the refractive astigmatism and not the keratometric one, and why the ocular residual astigmatism is reported for information rather than used in the arithmetic.

What it does not do

Sizing and vault are out of scope by design. Overall diameter and vault depend on sulcus dimensions and crystalline lens rise, not on astigmatism arithmetic, and they carry the manufacturer's liability. Published sizing methods agree on the recommended diameter in only about half of eyes and each selects the ideal size in 29% to 51%; in independent validation on 104 eyes an AI vault tool reached a mean absolute error of 135 µm with systematic overestimation. Size the lens with the manufacturer's own nomogram.

The spherical power is an estimate. It is a vergence calculation on the keratometry and d entered here, for sanity checking. Confirm it against the manufacturer's calculator before ordering.

Residuals are calculated, not achieved. Subjective refraction varies by about 0.17 D per power-vector component between examinations, and published scatter of surgically induced astigmatism in phakic surgery is as large as its own mean. A calculated residual of zero is a planning target, not a promise.

What to keep in mind

Calculated residuals assume the SIA is exactly the value you entered. Published series show wide eye-to-eye scatter, so treat small calculated gains with caution.
The tool does not size the lens and does not predict vault.
The spherical power shown is a vergence estimate. Confirm sphere and cylinder with the manufacturer's own calculator before ordering.
Prospective clinical validation of ODISEO has not yet been published.

Open the calculator

Supported platforms

Each platform is described by the grid it is manufactured on: the label axes available, the cylinder steps and the power range. Those limits decide what a plan can and cannot reach.

Platform	Label axis grid	Cylinder, lens plane	Lens power range	Status	Basis

What the status means

Measured. The catalogue grid and lens position used here were checked against manufacturer calculation reports.
Labelling unconfirmed. The grid is checked, but how the labelled power relates to the power in the eye has not been confirmed. Use the incision and the axis from the plan, and take the power from the manufacturer.
Not characterised. Values come from published documentation only. Treat the output as indicative.

All product names are trademarks of their respective owners. ODISEO is independent and is not endorsed by, or affiliated with, any manufacturer listed here.

Do you work for a manufacturer and want your platform described correctly, or integrated into your own calculator? Write to the author.

Frequently asked questions

Short answers for surgeons using the calculator for the first time.

What does ODISEO calculate?

For a toric phakic lens, it gives the incision meridian, the lens cylinder, the label axis to order, the meridian where the lens must sit, the rotation needed to get it there and the calculated residual astigmatism. It also gives a vergence estimate of the spherical power.

How is it different from the manufacturer's calculator?

Manufacturer calculators choose the lens for a given refraction. ODISEO adds the effect of your incision and compares every incision meridian you are willing to use, so the wound and the lens are planned together. It is meant to be used alongside the manufacturer's calculator and does not replace it.

Which SIA should I enter?

Your own, for the incision you use. The right figure is the vector mean (the centroid) of your SIA, which is smaller than the mean of the magnitudes. If you have never measured it, published values for a 3.0 mm temporal clear corneal incision in phakic lens surgery are around 0.2 to 0.3 D as a vector mean. Entering 0 reproduces a calculation that ignores the incision.

Why does it sometimes tell me to keep my usual incision?

Because the benefit of moving the wound was smaller than the threshold, 0.10 D by default. A small calculated gain rests entirely on the SIA being exactly what you typed, and real SIA varies from eye to eye.

Does it choose the lens size or predict vault?

No. Sizing and vault depend on the dimensions of the sulcus and on the crystalline lens, and remain with the manufacturer's own method.

Can I order the sphere it shows?

Treat it as a check, not as the order. The sphere is a vergence estimate that does not know the manufacturer's constants. Confirm the final power with the manufacturer.

Is my patient's data stored or sent anywhere?

No. Every calculation happens in your browser. Patient fields are kept only in the page's memory while it is open and disappear when you close or reload it. The only thing the browser remembers is that you accepted the conditions of use, and your light or dark preference.

Has it been clinically validated?

The arithmetic is standard vergence and vector analysis, and the catalogue of each platform was checked against manufacturer reports. A prospective clinical validation has not been published yet. Residuals shown are calculated, not achieved.

Is ODISEO a medical device?

No. It is an educational and planning aid for qualified professionals, and it has not been submitted to any regulatory authority. Responsibility for every surgical decision stays with the surgeon.

Does it work on a phone or without a connection?

It works on phones and tablets. Once the page has loaded, the calculation itself needs no connection.

How do I cite it, and can I use it in research?

Clinical use is free. Research use requires attribution: Balparda K. Balparda Phakic Calculator: ODISEO toric planning, version 1.0. Commercial use, and any research funded by industry, needs the author's written approval. See Terms and privacy.

Built by a surgeon who implants these lenses.

The Balparda Phakic Calculator is the home of ODISEO, a method for planning the incision and the toric phakic lens together. ODISEO stands for Optimised Determination of Incision and Specification for Effective Outcome. It began as a way to answer one question in the consulting room: with the lens I can actually order, where should I make the incision?

The author

Kepa Balparda, MD, MSc, PhD, FWCRS, FEBOS-CR, is a refractive surgeon in Medellín, Colombia. He trained in medicine and ophthalmology at Universidad Pontificia Bolivariana and holds an MSc in Refractive Surgery and a PhD in Vision Sciences from Universidad de Valladolid, Spain. He has implanted more than 1,300 phakic intraocular lenses across several platforms and has published more than 60 peer-reviewed articles.

Independence and disclosures

ODISEO is vendor-neutral. No manufacturer funded it, reviewed it or has any control over it. The author has received speaker fees, travel support or research consultancy fees from companies in ophthalmology, including manufacturers of lenses listed on this site (Biotech Healthcare and Care Group). He has no financial interest in the sale of any lens.

Intellectual property

The ODISEO method is the subject of United States provisional patent application 64/148,354. The name, the method and this implementation belong to the author.

Licence in one paragraph

Clinical use is free. Research use requires attribution. Commercial use of any kind, and any research funded in whole or in part by industry, requires the author's prior written approval. The full conditions are under Terms and privacy.

For manufacturers and distributors. ODISEO can be licensed for integration into a platform's own calculator, with that platform's catalogue and constants. Get in touch.

Version 1.0, built 2026-11-12.

Conditions of use and privacy

The short version: this is a planning aid for professionals, it is free for clinical use, and nothing you type is sent anywhere.

Privacy

All computation happens in your own browser. No refraction, biometry, patient detail or uploaded file is transmitted to the author or to anyone else. There are no accounts and no cookies. The browser's local storage holds two things only: that you accepted these conditions, and your light or dark preference. Fonts and the PDF reader are served from this site itself, so no third party is contacted when the page loads.

This site does not use analytics or tracking.

Conditions of use

Questions, errors and licensing

If a result looks wrong, please send the inputs and the output. Reports of errors are the most useful message this site can receive.

Email

kb@kepabalparda.com

Kepa Balparda, Medellín, Colombia. Written communication is preferred.

What to write about

A result you disagree with. Include the eye's inputs, the platform and what you expected.
A platform that is missing or described incorrectly.
Research use. Attribution is all that is needed, but the author is glad to hear about it.
Commercial licensing or integration.

Please do not send patient-identifying information by email.

Plan the incision and the toric phakic lens together.

Before you start

ODISEO toric planning

The lens to order

The same eye on each platform

In the eye how the lens arrives and where it has to end

The vector picture doubled-angle plane, where the whole method lives

Meridian sweep what every possible incision would leave behind

Against the alternatives

Cylinder options at the recommended incision

Spherical power vergence estimate, confirm with the manufacturer

Read a report

One calculation instead of two.

The refraction is taken to the cornea

Your incision is added as a vector

The lens is chosen from the real catalogue

Every reachable incision is compared

The arithmetic, briefly

What it does not do

What to keep in mind

Supported platforms

What the status means

Frequently asked questions

Built by a surgeon who implants these lenses.

The author

Independence and disclosures

Intellectual property

Licence in one paragraph

Conditions of use and privacy

Privacy

Conditions of use

Questions, errors and licensing

Email

What to write about