Astigmatism, a condition of refractive error in the eye, is related to the inconsistent curvature of the cornea and lens surface. Research found that congenital astigmatism is very common, clinical can find astigmatism eye as high as 90%, but many people's astigmatism degree is not high, when matching glasses, do not add astigmatism degree. About 44% of people have astigmatism above 50 degrees, 10% have astigmatism above 100 degrees, and 8% have astigmatism of 150 degrees or more.

We can not find the division of corneal astigmatism and lens astigmatism in Baidu Encyclopedia, because they are classified according to the refractive medium of the eye. The refractive media of the eye are mainly tears, cornea, aqueous humor, lens, and eye contents (vitreous body). Professional academic papers can often see such professional terms.

What is corneal astigmatism? What is crystalline astigmatism?

Corneal astigmatism: as the name suggests, it is astigmatism formed on the cornea. Corneal astigmatism will not be measured separately in ordinary optometry. But when doing some corneal examination or related treatment, it needs to be measured separately. For example: do excimer laser surgery, wear orthokeratology lens and RGP.

In clinical, there will be some diseases causing corneal astigmatism increase, leading to the decline of vision. For example: pterygium, keratoconus, ocular trauma and so on. Corneal astigmatism can be detected by keratometer or corneal topography.

Lens astigmatism: also known as intraocular astigmatism, it is mainly caused by the lens.

In short, what we usually call astigmatism = corneal astigmatism + lens astigmatism.

What are the effects of corneal astigmatism and lens astigmatism on keratoplasty?

In the process of fitting orthokeratology lens, we need to consider the influence of these two parameters on the wearing effect

1. Large corneal astigmatism is easy to cause lens instability or deviation.

2. Lens astigmatism may be exposed by orthokeratology lens after changing corneal morphology reasonably. If the corneal astigmatism detected by corneal topography is too large, but the degree of refraction astigmatism is very low. Special attention should be paid to the possible exposure of crystal astigmatism.

Therefore, in the process of fitting orthokeratology lens, it is helpful for the surgeon to identify corneal astigmatism and lens astigmatism to accurately evaluate the expected wearing effect.