Keratometry
Warsaw · Krakow · Vienna · Zurich
Keratometry (ophthalmometry, corneal topography) is a non-invasive, painless diagnostic examination performed when it is necessary to measure the curvature and refractive power of the cornea.
Keratometry – In Brief
- What it is: measurement of the curvature and refractive power of the cornea in the main axes – manually (ophthalmometer) or digitally (videokeratograph, biometer)
- What it’s for: diagnosis and measurement of astigmatism, contact lens fitting, calculation of implant power before cataract surgery and lens replacement, laser correction planning
- How it works: you look at a point of light, the device measures reflections on the cornea – non-contact, in a matter of seconds
- Result: K values in diopters and the axis of astigmatism; in cases of irregular astigmatism we supplement with full corneal topography
- Price: At SwissLaser we perform it as part of a comprehensive qualification examination (400 PLN, approximately 90 minutes, Warsaw and Krakow), which includes the complete set of measurements needed before the procedure.
Keratometry (Ophthalmometry, Corneal Topography)
This is a non-invasive, painless diagnostic examination performed when it is necessary to measure the curvature and refractive power of the cornea. Indications for the examination include:
- diagnosis of refractive errors and the need to select eyeglasses/contact lenses
- diagnosis of astigmatism
- preparation for cataract surgery (necessity of calculating the power of the implanted artificial lens)
- before planned laser vision correction procedures and after such procedures to assess the changes in corneal curvature obtained
- in the diagnosis of certain corneal diseases (e.g., keratoconus [keratoconus], megalocornea [megalocornea], keratoglobus [keratoglobus], microcornea [microcornea], cornea plana [cornea plana], or sclerocornea).
Keratometry in the Diagnosis of Astigmatism
Manual keratometry is the gold standard for assessing the power and axis of astigmatism in toric lens calculation. A keratoscope (Placido disc), which is a disc with black and white circles, allows observation of the shape of the reflected circles on the cornea. Specialists also still use the Javal ophthalmometer (keratometer), a manual keratometer used to measure corneal curvatures in two main meridians. These measurements allow for precise determination of the magnitude and axes of astigmatism.
Digital Corneal Shape Examination
Ophthalmologists also have access to a computer videokeratograph (digital) – the examination uses an image of the Placido disc projected onto the corneal surface, which is then recorded by a camera, sent to a computer, and analyzed. The keratometer projects images onto the cornea and analyzes the position of their reflections relative to each other. The central part of the cornea acts as a spherical convex mirror.
What does corneal measurement involve?
If an illuminated object of known size is placed at a known distance from the cornea and the size of the reflected image can be measured, its radius of curvature can be determined. Because the eye is constantly moving, measuring the image size with a linear scale is difficult. The use of two prisms placed base-to-base will create two images separated by a constant distance, which does not change due to minor eye movements (the doubling principle).
Are you eligible for laser surgery?
Corneal topography allows for a precise assessment of the eye’s surface and the detection of many anterior segment pathologies, thereby enabling appropriate patient preparation for surgery. It is believed that this examination is crucial for determining a patient’s eligibility for surgery. A cornea that is too thin may, but does not necessarily, contraindicate the procedure. Corneal thickness is measured during an examination called pachymetry (optically measured non-contact or by contact using an ultrasonic probe). If the cornea is too thin, but other (numerous!) eye parameters checked by the specialist for laser surgery are correct, the laser can be programmed to perform such an operation.
Corneal tomography also allows for determining the depth of the anterior chamber, the iridocorneal angle, the size of any changes in shape, scars, and inhomogeneities.
During computer keratometry, the doctor can see:
- The eye’s surface: this provides additional information about each corneal curvature and its characteristics. Based on this, it is assessed whether the planned correction is possible and will achieve the patient’s desired results.
- The posterior corneal surface: it should be healthy for a decision on surgery to be made.
- Corneal thickness: determines whether all methods are possible – that is, surface methods, LASIK, and micro-lens laser vision correction.
- Anterior chamber depth and corneal diameter: this is important for phakic lens implantation.
The result of the examination is a corneal map, a cross-section of the corneal surface, and a map of digital corneal curvature values.
The most important step is to choose the appropriate method for your vision defect. During the initial consultation, we will propose the suitable laser correction technique.
Frequently Asked Questions
How does keratometry differ from corneal topography?
Keratometry measures curvature at several central points and provides two main axes. Topography creates a color map of the entire corneal surface from thousands of points – essential in cases of irregular astigmatism and suspected keratoconus.
Does keratometry hurt?
No. The examination is non-contact, takes a matter of seconds, and does not require drops.
Why is keratometry needed before cataract surgery?
The power of the implanted lens is calculated from the length of the eyeball and the curvature of the cornea. An error in keratometry translates directly into a refractive error after surgery, which is why we repeat the measurement and compare it with biometry.
How much does keratometry cost?
At SwissLaser, keratometry is part of a comprehensive qualification examination for 400 PLN, performed in Warsaw and Krakow.
Do contact lenses affect the result?
Yes – contact lenses change the shape of the cornea. Soft lenses should be discontinued for 7 days, hard lenses for 3 weeks before measurement, if the result is to be used for procedure planning.
We perform all examinations in Warsaw (Kolejowa 1) and Krakow (Kluczborska 15/U3). Diagnostic overview: eye examinations; what happens next: qualification for the procedure.
