(1) Central District: Also known as? Top area, its range? It is also recognized that the diopter around the corneal apex changes within 65438±0D days. The change of diopter in this area should be within 0.25D, and the change of corneal refractive power in this area is small, regular and approximately spherical. Generally speaking, what is the diameter of this area? 4 mm (optical area)
⑵ Near central area: an annular area with a width of 3 mm and a diameter of 4 mm to 7 mm next to the central area of the cornea, where the cornea gradually flattens and assumes an aspheric shape, which plays a very important role in the design and wearing of contact lenses.
⑶ Peripheral zone: The annular zone with a corneal diameter of 7mm to 1 1mm, which is the largest? Plane and asphericity are more obvious and more? Asymmetric form.
⑷ Corneal limbus: An annular area adjacent to the sclera, with a width of about 0.5mm, which is often covered by corneal limbus vascular arch. This area is related to some diseases of corneal limbus thinning, and the change of corneal limbus area will cause the change of refractive power in this area, thus indirectly affecting the refractive state of corneal center.
Extended data corneal topography is to analyze the whole corneal surface, in which 256 points on each projection ring are counted in the processing system, so more than 7000 data points on the whole cornea enter the analysis system.
It can be seen that corneal topography is systematic, accurate and precise. Corneal topographic map is used for clinical diagnosis of corneal astigmatism, quantitative analysis of corneal properties, and display of corneal curvature with data or different colors. The difference between the two axes is corneal astigmatism.
The appearance of corneal topography makes the early diagnosis of subclinical keratoconus and keratoconus possible, and the diagnostic accuracy of keratoconus is as high as 96%. In addition, it can also be used to diagnose corneal deformation caused by contact lens.
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