A peripheral toric contact lens is a lens with a torical periphery, the peripheral radii are in the two main directions different. The optical zone is spherical, but has an oval shape due to the presence of two different peripheral radii. The lens must centre with the long axis of the oval zone on the deepest meridian of the eye.
The contact lens peripheral construction can be used when the pressure on the flattest meridian of an astigmatic cornea becomes too high for a contact lens with a spherical periphery. As a rule, the need for a peripheral toric contact lens will be greatest with a relatively large corneal astigmatism, so that the area between 1.5 and 5.5 dpt. corneal astigmatism is the most appropriate. In principle, the adjustment of a peripheral toric contact lens in relation to a spherical lens remains the same. For corneal astigmatism of 1.50 dpt. and above, the use of a peripheral toric contact lens may be beneficial if there is a risk of over pressure on the flattest meridian.
Applicable to all (a)spherical indoor geometries
B.C.R 7.00 – 10.00 per 0.05 ascending
Power -/+ 40.00 per 0.25 ascending
Diameter 9.00 – 12.00
Cilinder 1.00 – 10.00 per 0.25 ascending
Take as a starting point the peripheral astigmatism 0.50 more than the corneal astigmatism and leave the other specifications of the lens equal to the fitting of a spherical contact lens.
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