Astigmatism: Causes, Symptoms, and Treatment
Also known as: Astigmatic vision, Irregular cornea
Overview
Astigmatism is a very common refractive eye condition. In U.S. national health surveys (NHANES), about 1 in 5 people had significant astigmatism, a share that rose to nearly 30% of adults over 40. It happens when the cornea or lens has an irregular, slightly oval shape instead of being evenly round. This irregularity keeps light from focusing properly on the retina, which causes blurry or distorted vision at both near and far distances. Astigmatism can appear in childhood and often occurs alongside nearsightedness or farsightedness.
Causes and risk factors
Astigmatism is most often congenital, tied to a naturally irregular shape of the cornea or lens. Main risk factors include:
- Family history (genetic predisposition)
- Keratoconus: progressive thinning and bulging of the cornea into a cone shape
- Eye injuries or corneal scarring
- Previous eye surgery
- Certain conditions such as Down syndrome
- Long-term wear of rigid contact lenses, which can reshape the cornea
Symptoms
The signs of astigmatism vary with its severity:
- Blurry or distorted vision, at both near and far distances (the most common symptom)
- Straight lines that appear wavy or tilted
- Eye strain after reading or screen work
- Frequent headaches, especially by the end of the day
- Squinting to try to see more clearly
- Trouble driving at night, with halos around lights
- In children: academic difficulties linked to poor vision
Diagnosis
Astigmatism is diagnosed by an ophthalmologist or optometrist during a comprehensive eye exam, using:
- Subjective refraction: testing corrective lenses with a phoropter
- Keratometry or corneal topography: precise measurement of corneal curvature
- An auto-refractor for an objective measurement
- A slit-lamp exam to assess the health of the cornea
Treatments
Several options correct astigmatism effectively:
- Corrective eyeglasses with toric (cylindrical) lenses: the most common, safe, and accessible option for all ages
- Toric contact lenses (soft or rigid gas-permeable): offer a wider field of view and good correction, especially suited to active people
- Laser refractive surgery (LASIK, PRK): a lasting correction option for adults whose eyeglass prescription has been stable for at least a year
- Phakic intraocular lenses: a surgical option for high astigmatism that cannot be corrected with laser surgery
- Intracorneal ring segments: used for astigmatism associated with keratoconus
Regular eye exams are essential to keep your correction up to date over time.
Prevention
Congenital astigmatism cannot be prevented, but a few habits can limit its progression and complications:
- See an eye doctor starting in childhood for early screening, especially with a family history
- Avoid rubbing your eyes vigorously, which can worsen keratoconus
- Protect your eyes from injury by wearing protective eyewear during higher-risk activities
- Follow proper contact lens hygiene
- Get regular eye exams
When should you see a doctor?
See a doctor promptly for sudden blurry vision, eye pain, significant halos around lights, or a sudden drop in visual acuity. In children, any sign of visual difficulty (squinting, headaches, declining school performance) should prompt a timely visit.
Sources
- American Academy of Ophthalmology (AAO), definition, inherited risk, symptoms, diagnosis, and correction
- American Academy of Ophthalmology (AAO): LASIK, LASIK candidacy (adult, stable prescription over the past year)
- National Eye Institute (NEI), U.S. National Institutes of Health
- MedlinePlus, U.S. National Library of Medicine health information
- StatPearls: Astigmatism (NCBI Bookshelf, NIH), causes including keratoconus, Down syndrome, corneal injury and contact lens warpage, plus diagnosis and treatment
- StatPearls: Keratoconus (NCBI Bookshelf, NIH), eye rubbing as an aggravating factor, and intracorneal ring segments and phakic intraocular lenses
- Astigmatism prevalence from NHANES 2005-2008 (PMC, National Institutes of Health), U.S. population prevalence of astigmatism by age