What do you need to know about Corneal topography?
It is used to diagnose certain corneal pathologies. Corneal topography is a very precise method that consists of making a computerized map of the cornea to diagnose corneal diseases.
Corneal topography is a computer-aided diagnostic tool that creates a three-dimensional map of the surface curvature of the cornea. The cornea (the front window of the eye) is responsible for about 70% of the eye’s focusing power. An eye with normal vision has a uniformly rounded cornea, but if the cornea is too flat, too steep or unevenly curved, the result is less than perfect vision. The greatest advantage of corneal topography is its ability to detect irregular conditions invisible to most conventional tests.
Corneal topography produces a detailed and visual description of the shape and power of the cornea. This type of analysis provides very fine details of the condition of the corneal surface. These details are used to diagnose, monitor and treat various eye disorders. They are also used for fitting contact lenses and planning surgery, including laser vision correction. For laser vision correction, corneal topography mapping is used in conjunction with other tests to determine exactly how much corneal tissue will be removed to correct vision and with what ablation pattern.
In the Dr. Holhoș clinics we also perform in some cases investigations with Pentacam AXL Wave and MS-39 device in order to prepare epithelial mapping, in addition to corneal topography.
What does Corneal topography involve?
During the investigation, the patient sits in front of the topographer with the head placed on a special holder, while a series of data are generated. The computer software digitizes these data points to produce a printout of the corneal shape, using different colors to identify different heights, just as a topographical map of the earth displays changes to the land surface. The topographic map can be represented in a number of graphical formats, such as a sagittal map, which color codes the steepness of the curvature according to its dioptric value. Testing is non-contact, painless and short.
What disorders can be diagnosed with Corneal topography?
Dr. Holhoș clinics are equipped with the Zeiss Atlas topographer, the top of the range from Zeiss, which allows a high accuracy of the investigation result. Zeiss’ patented technology for this device involves a certain degree of automation of the procedure, which means more precision and speed.
Computerized corneal topography can be beneficial in evaluating certain corneal diseases and injuries, including:
- Corneal diseases
- Corneal abrasions
- Corneal deformities
- Irregular astigmatism following corneal transplants
- Postoperative cataract extraction with acquired astigmatism
Corneal topography is most commonly used for the following purposes:
Refractive surgery: examining patients for a normal corneal shape and excluding suspicious or keratoconus patterns. Postoperative, topography can help assess the dioptric change created in the cornea (thus actual corneal change), ruling out decent or incomplete ablation, post excimer ectasia or other changes.
Keratoconus: early screening of keratoconus suspects is one of the most useful roles of topography. In cases with established keratoconus, the role of topography is essential for monitoring progression and performing cross-linking surgery, and for fitting contact lenses.
Postoperative astigmatism: corneal astigmatism can be studied with the topographer and selective suture removal or other interventions can be planned.
Effect of corneal and ocular surface disorders: disorders such as pterygium, lingual dermoid, localized corneal scarring, can cause a change in corneal topography and therefore monitoring is very useful.
Other uses: contact lens fitting, incision placement and intrastromal ring placement in keratoconus, ocular vs corneal wavefront monitoring.