From the Guidelines
Astigmatism is a refractive error that occurs when incident light rays do not converge at a single focal point, resulting in blurred vision at all distances. This condition can be divided into corneal, lenticular, and retinal astigmatism, with most cases being corneal in origin 1. According to the refractive errors preferred practice pattern, astigmatism can be further classified into regular and irregular corneal astigmatism, with the latter being clinically significant in conditions such as keratoconus and other corneal ectasias 1.
Some key points to consider about astigmatism include:
- It can occur alongside other refractive errors, such as myopia and hyperopia 1
- The correction of astigmatism can be achieved through various methods, including corrective eyewear and refractive surgeries 1
- Higher order aberrations, such as coma, spherical aberration, and trefoil, can also affect visual quality and cannot be fully corrected by spherocylindrical corrective lenses 1
- Regular comprehensive eye exams are essential for proper diagnosis and management of astigmatism, as it can change over time 1
The most effective way to manage astigmatism is through a comprehensive eye exam and appropriate correction, which can include corrective eyewear or refractive surgery. This approach can help alleviate symptoms such as eye strain, headaches, and difficulty with night vision, and allow individuals to perform daily activities without visual discomfort 1. It is essential to note that the definition and classification of astigmatism, as well as its correction, are based on the most recent and highest quality evidence, as outlined in the refractive errors preferred practice pattern 1.
From the Research
Definition of Astigmatism
- Astigmatism is a refractive error that occurs when the eye cannot focus light properly, resulting in blurred or distorted vision 2.
- It is caused by an irregularly shaped cornea or lens, which focuses light at two points rather than one 2.
- Astigmatism can be internal, external, or a combination of both, and can be classified as "with the rule", "against the rule", or "oblique" 3.
Prevalence of Astigmatism
- Astigmatism is the most frequent refractive error worldwide, followed by hyperopia and myopia 3.
- The prevalence of astigmatism (≥ 1 D cylinder) is 23.1% in people aged 20 to 39,27.6% in people aged 40 to 59, and 50.1% in people aged 60 and older 2.
Treatment of Astigmatism
- Various treatment options are available for astigmatism, including conservative approaches such as eyeglasses or toric contact lenses, and surgical procedures such as photorefractive keratectomy, femtosecond laser-assisted keratotomy, and toric intraocular lens implantation 3, 4, 5, 6.
- Toric intraocular lenses (IOLs) are effective in correcting preexisting corneal astigmatism in eyes with previous excimer laser corneal refractive surgery 5.
- Femtosecond laser-assisted astigmatic keratotomy (FSAK) and toric IOL implantation are both effective procedures for correcting astigmatism in cataract surgery, but toric IOL implantation may be more effective in certain cases 6.