Astigmatism

Blurry vision at all distances can signal astigmatism, a common refractive error affecting nearly 1 in 3 Americans. Unlike nearsightedness or farsightedness, astigmatism creates distorted vision because light entering the eye focuses on multiple points rather than a single point on the retina. Optometrists in Tulsa diagnose this condition during routine eye exams and can prescribe effective correction methods.

Astigmatism correction has advanced significantly in recent years. Whether you choose glasses, toric contact lenses, or refractive surgery, clear vision is achievable with the right treatment plan.

What Is Astigmatism?

Astigmatism is a refractive error caused by an irregularly shaped cornea or lens. In a normal eye, the cornea has a round shape like a basketball. With astigmatism, the cornea is shaped more like a football, with one meridian significantly more curved than the perpendicular meridian.

This irregular curvature prevents light rays from focusing properly on the retina. Instead of converging at a single focal point, light focuses at multiple points, either in front of or behind the retina. The result is blurred or distorted vision at all distances.

Types of Astigmatism

Corneal astigmatism occurs when the cornea (the clear front surface of the eye) has an irregular shape. This is the most common type.

Lenticular astigmatism develops when the lens inside the eye has shape irregularities. The cornea may have a normal spherical shape, but the lens compensates or adds to the refractive error.

Astigmatism also classifies by axis orientation:

• Regular astigmatism: The two principal meridians are perpendicular to each other (most common)
• Irregular astigmatism: The principal meridians are not perpendicular, often caused by eye injury, surgery, or keratoconus

Causes of Astigmatism

Astigmatism is usually present from birth and often runs in families. Genetics play the strongest role in determining corneal shape.

The condition can also develop or worsen due to:

• Eye injury or trauma that changes corneal shape
• Eye surgery complications that alter corneal curvature
• Keratoconus, a progressive condition that thins and reshapes the cornea into a cone
• Pterygium, a growth on the eye surface that can distort the cornea
• Eyelid pressure from conditions like chalazion or ptosis

Contrary to popular belief, reading in dim light or sitting too close to screens does not cause astigmatism. The condition results from the physical shape of eye structures, not from habits or eye strain.

Symptoms of Astigmatism

Astigmatism creates distinct visual symptoms that differ from other refractive errors:

Blurred or distorted vision affects both near and far objects. Lines may appear tilted or wavy, and text may seem smudged.

Eye strain and fatigue develop after prolonged visual tasks. Your eyes work harder to compensate for unclear images, leading to discomfort during reading, computer work, or driving.

Headaches often occur in the forehead or temple area, particularly after focusing on detailed work.

Difficulty seeing at night is common because pupils dilate in low light, allowing more unfocused light rays to enter the eye. Halos or starbursts may appear around lights.

Squinting happens unconsciously as you try to improve focus by changing the shape of your eye.

Many people with mild astigmatism experience no noticeable symptoms. Others may attribute symptoms to normal eye tiredness without realizing correction would help.

How Astigmatism Is Diagnosed

Eye doctors diagnose astigmatism during a comprehensive eye examination using several tests:

Visual Acuity Test

You read letters on a standardized eye chart at 20 feet. This establishes baseline vision clarity and identifies whether refractive correction is needed.

Keratometry

A keratometer measures the curvature of your cornea's steepest and flattest meridians. The instrument reflects light off the corneal surface to calculate the degree of curvature in different meridians.

Corneal Topography

This computerized test creates a detailed map of your corneal surface. It measures thousands of points across the cornea to detect irregular astigmatism, keratoconus, or corneal scarring that standard tests might miss.

Refraction Assessment

Your eye doctor uses a phoropter (the instrument with multiple lenses) to determine your exact prescription. You compare different lens combinations while viewing an eye chart, identifying which lenses provide the clearest vision.

The refraction test produces measurements in three numbers:

• Sphere (SPH): Corrects nearsightedness or farsightedness
• Cylinder (CYL): Corrects astigmatism (the power needed to neutralize the irregular curvature)
• Axis: The orientation of astigmatism (0 to 180 degrees)

A complete astigmatism prescription might read: -2.00 -1.50 x 090, indicating moderate nearsightedness with moderate astigmatism at the 90-degree axis.

Astigmatism Correction Options

Eyeglasses for Astigmatism

Eyeglasses remain the simplest and most common astigmatism correction method. Prescription lenses contain a cylindrical correction that compensates for the irregular corneal or lenticular shape.

The lenses are ground with different curvatures in different meridians. When positioned at the correct axis, they neutralize the eye's irregular focusing, allowing light to converge properly on the retina.

Advantages:

• No risk of eye infection
• Easy to use
• Can be removed when not needed
• Protect eyes from UV light and debris
• Affordable compared to surgery

Considerations:

• Peripheral distortion can occur with high astigmatism prescriptions
• Frames can limit peripheral vision
• Glasses fog, get wet, or smudge
• May interfere with sports or active lifestyles

Toric Contact Lenses

Toric contact lenses correct astigmatism by incorporating different powers in different meridians, similar to eyeglasses. Unlike standard spherical contacts, toric lenses must maintain a specific orientation on the eye to work correctly.

Manufacturers use several stabilization methods to prevent lens rotation:

• Prism ballast: Thicker lens bottom that uses gravity to keep the lens oriented
• Peri-ballast: Thin zones at top and bottom, thick zones at sides
• Truncation: Flattened lens edge that aligns with the lower eyelid

Toric contacts are available in soft and rigid gas permeable (RGP) materials. Soft toric lenses offer immediate comfort but may rotate during wear. RGP lenses provide sharper vision and better stability but require an adaptation period.

Professional contact lens fitting ensures proper lens selection, fit, and orientation for astigmatism correction.

Advantages:

• Natural field of view without peripheral distortion
• No glasses to fog or smudge
• Better for active lifestyles and sports
• Some find them more cosmetically appealing

Considerations:

• Higher cost than standard contacts
• Require proper hygiene to prevent infection
• May take longer to achieve optimal fit
• Need regular replacement (daily, biweekly, or monthly)

Refractive Surgery

Surgical astigmatism correction permanently reshapes the cornea to eliminate or reduce the irregular curvature.

LASIK (Laser-Assisted In Situ Keratomileusis) creates a thin corneal flap, then uses an excimer laser to remove microscopic amounts of corneal tissue. The flap is repositioned, and the reshaped cornea focuses light correctly. LASIK can correct astigmatism up to approximately 6 diopters.

PRK (Photorefractive Keratectomy) removes the corneal epithelium (outer layer), then reshapes the cornea with the same excimer laser used in LASIK. The epithelium regenerates over several days. PRK is preferred for patients with thin corneas or certain occupations where flap dislocation is a concern.

SMILE (Small Incision Lenticule Extraction) uses a femtosecond laser to create a small lens-shaped piece of tissue (lenticule) within the cornea. The surgeon removes this lenticule through a small incision, changing the corneal shape. SMILE corrects myopic astigmatism.

Refractive Lens Exchange replaces the eye's natural lens with an artificial intraocular lens (IOL). Toric IOLs correct astigmatism while addressing presbyopia (age-related reading difficulty). This option suits patients over 45 or those with high refractive errors.

Ideal candidates for refractive surgery:

• Age 18 or older with stable prescription for at least one year
• Healthy corneas of adequate thickness
• No active eye disease or infection
• Realistic expectations about outcomes
• Not pregnant or nursing (hormones affect prescription)

Surgery eliminates dependence on glasses or contacts for many patients, though reading glasses may still be needed after age 40.

Living With Astigmatism

Regular Eye Examinations

Astigmatism can change over time. Annual comprehensive eye exams ensure your prescription remains accurate and detect any progression or complications.

Children with astigmatism need frequent monitoring because refractive errors can affect learning and development. Uncorrected astigmatism in childhood may contribute to amblyopia (lazy eye) or eye strain that interferes with reading.

Corrective Lens Maintenance

Glasses require regular cleaning to maintain optimal vision. Scratched or damaged lenses reduce clarity and may cause eye strain.

Contact lens wearers must follow prescribed replacement schedules and proper hygiene protocols. Overwearing lenses or poor cleaning habits increase infection risk.

Managing Eye Strain

Even with proper correction, extended visual tasks can cause fatigue. The 20-20-20 rule helps reduce digital eye strain: Every 20 minutes, look at something 20 feet away for 20 seconds.

Proper lighting when reading or using screens reduces the eyes' workload. Positioning screens at arm's length and slightly below eye level minimizes strain.

When to Seek Care

Contact your eye care provider if you experience:

• Sudden vision changes or increased blurriness
• Flashes of light or new floaters
• Eye pain or redness
• Halos or glare that worsens
• Difficulty seeing clearly with your current prescription

These symptoms may indicate prescription changes, eye health issues, or complications requiring professional evaluation.