Corneal Topography
Warsaw · Krakow · Vienna · Zurich
Corneal topography is also known as keratometry (computerized/digital or manual). During this painless and non-invasive examination, a colored map of the eye’s local corneal curvatures is created, enabling the ophthalmologist to diagnose and assess any abnormalities in the cornea’s structure and condition.
Corneal Topography – In Brief
- What it is: a computerized map of the shape of the anterior and posterior corneal surfaces and their thickness from thousands of points (videokeratograph, Scheimpflug tomograph, or OCT)
- Why it’s done: to rule out keratoconus and irregular astigmatism before laser correction, to select the ablation method and profile, to fit contact lenses, and for post-crosslinking control
- How it’s performed: non-contact, a few seconds per eye; no drops
- Preparation: discontinue soft contact lenses for 7 days, hard lenses for 3 weeks – otherwise the map shows the shape of the lens, not the cornea
- Price: At SwissLaser, we perform it as part of a comprehensive qualification examination (400 PLN, approximately 90 minutes, Warsaw and Krakow), which includes a complete set of measurements needed before the procedure.
How Is the Corneal Shape Examined?
A keratoscope (Placido disk), which is a disk with black and white circles, allows observation of the shape of the circle reflections on the cornea. Manual keratoscopes are increasingly less common, as ophthalmologists and optometrists now have computerized/digital videokeratographs at their disposal. This examination uses an image of the Placido disk projected onto the corneal surface, which is then recorded by a camera, sent to a computer, and analyzed. The results of the examination include a corneal map, a cross-section of the corneal surface, and a map of the digital values of corneal curvatures.
The Gold Standard in Astigmatism Measurement
Specialists still use the Javal ophthalmometer (keratometer), a manual keratometer, to measure corneal curvatures in two main meridians. These measurements allow for precise determination of the magnitude and axes of astigmatism. Manual keratometry is the gold standard for assessing the power and axis of astigmatism in toric intraocular lens calculations.
Corneal Examination Before Lens Selection and Surgery
Corneal topography is one of the most important examinations if we are planning the selection of artificial implantable lenses used in the treatment of myopia, hyperopia, astigmatismand cataracts. It is a particularly important tool for qualifying for the appropriate type of lens. Thanks to it, keratoconus can also be diagnosed, with an assessment of its stage of advancement and possible progression. To assess the patient’s eye condition, the results of individual corneal topography, e.g., from a year ago and from the current examination, are compared. Depending on the changes that have occurred during this time, actions are taken to stop the changes occurring in the cornea. Corneal topography also allows for the diagnosis of postoperative or post-traumatic corneal deformities.
Corneal topography, as mentioned, is most often performed using a digital/computerized videokeratograph. The patient rests their chin and forehead on a support in front of a dome illuminated by red light. The dome is covered with concentric black rings that reflect on the cornea during the examination. During the examination, the patient must look steadily, without blinking, at a centrally placed light point. The reflections of the circles/rings (described above) on the cornea, their width, and distortions are recorded and analyzed by computer, then converted into corneal curvature radii. The resulting corneal map can be two- or three-dimensional.
Does a Thin Cornea Exclude Surgery?
There is a belief that this examination is decisive for a patient’s eligibility for surgery. Patients fear that a cornea that is too thin is equivalent to disqualification. However, a cornea that is too thin may, but does not necessarily, be a contraindication to the procedure. Corneal thickness is measured during an examination called pachymetry (optical non-contact or contact using an ultrasound probe).
Which Examinations Determine Surgery?
If the cornea is too thin, but other (numerous!) parameters of the eye to be laser-operated, checked by the specialist, are normal, the laser can be programmed to perform such an operation (depending on the degree of the refractive error). We distinguish between so-called Scheimpflug or OCT topographies, which also measure corneal thickness and other anatomical parameters of the anterior segment of the eye, and so-called Placido topographies, which only measure the regularity of the anterior part of the cornea (without pachymetry).
Ocular Optical Coherence Tomography, also known as Optical Coherence Tomography (OCT)
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. Anomalies of the anterior and posterior cornea are a warning sign that problems may arise in the future. Based on their analysis, the doctor decides whether or not to undertake laser vision correction. If so, which technique to use. And if not, whether it is possible to implant phakic lenses or replace the lens. They may also decide to completely forgo surgical intervention.
- The posterior corneal surface: it should be healthy for a decision on surgery to be made.
- Corneal thickness: This determines whether all methods are possible – i.e., surface methods, LASIK, and small incision lenticule extraction (SMILE).
- Anterior chamber depth and corneal diameter: This is important for phakic lens implantation.
More Precise Corneal Examination – Why Is It Important?
Specialists believe that a routine slit-lamp examination may cause an ophthalmologist to overlook eye diseases such as epithelial basement membrane dystrophy (EBMD). If the disease goes unnoticed, it can lead to postoperative refractive problems.
Computerized keratometry is a non-invasive and painless examination (the patient sits comfortably, resting their forehead and chin on a special support of the examination device), and the accuracy of the measurement depends on the immobilization of the patient’s eyeball – hence the need not only to stabilize their head but also for them to look centrally ahead at the light point visible in the device.
Indications for corneal topography:
- planned laser vision correction
- all procedures involving the cornea
- assessment of the cornea’s condition after these procedures, as well as after transplants and mechanical injuries
- selection of rigid contact lenses, correcting not only atypical astigmatism but also advanced myopia or hyperopia
- the need to determine the power of an artificial intraocular lens, which is implanted into the eye during cataract surgery.
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.
Most Frequent Questions
Does corneal topography detect keratoconus?
Yes – it is the basic examination for diagnosing keratoconus. Irregular corneal steepening, asymmetry between the right and left eye, and thinning in the thickness map allow for early detection of keratoconus before vision deteriorates.
Why is topography mandatory before laser vision correction?
Laser removes corneal tissue; if the cornea is irregular or suspected of having keratoconus, the procedure could weaken it. Topography also shows the axis of astigmatism, which the laser must hit with an accuracy of a few degrees.
How long does corneal topography take and does it hurt?
A few seconds per eye, non-contact and painless. The doctor discusses the results – colored maps – immediately.
How to prepare for topography?
Discontinue contact lenses: soft for 7 days, hard for 3 weeks. Come without eye makeup and do not use moisturizing drops directly before the examination.
How much does corneal topography cost?
At SwissLaser, topography is part of a comprehensive qualification examination for 400 PLN, performed in Warsaw and Krakow.
All examinations are performed in Warsaw (ul. Kolejowa 1) and Krakow (ul. Kluczborska 15/U3). Overview of diagnostics: eye examinations; what happens next: qualification for the procedure.
