Astigmatism is a common vision condition that causes blurred vision. It occurs when the cornea or lens in the eye is irregularly shaped, causing light to focus imperfectly on the retina. This results in distorted or blurry vision. Astigmatism can worsen over time or remain stable throughout life. There are several factors that can cause astigmatism to progress and worsen.
Aging
As we age, changes in the structure of the eye can cause astigmatism to worsen. The cornea can become less flexible and take on a more irregular shape with age. The lens inside the eye also becomes less elastic over time. These age-related changes often result in increased astigmatism and vision deterioration in older adults. Many people develop astigmatism for the first time later in life due to these normal age-related changes.
Eye Injury
Injuries to the eye, particularly the cornea, can trigger the onset or worsening of astigmatism. Scar tissue that develops after an eye injury may cause irregularities in the cornea’s shape. Any type of trauma to the cornea – from chemical burns to corneal ulcers – can potentially distort its smooth curvature and induce astigmatic changes. Eye surgeries like corneal transplantation and cataract surgery also carry a risk of inducing astigmatism during the healing process.
Eye Surgery
While eye surgery aims to correct vision, it can sometimes worsen astigmatism as a side effect. Incisions made during cataract surgery or corneal transplantation can distort the cornea’s shape and increase astigmatism. Laser eye surgeries like LASIK are also associated with higher order aberrations that can induce astigmatism. Post-surgical astigmatism often improves over time as healing occurs, but some permanent worsening is possible. Proper wound construction and precise laser calibration helps minimize astigmatic side effects of eye surgery.
Contact Lens Wear
Wearing contact lenses, particularly rigid gas permeable lenses, can worsen astigmatism over time. The pressure of the contacts on the cornea may gradually distort its shape. This most often occurs with improper contact lens fitting and overwear. Soft contact lenses typically do not affect astigmatism as much. To prevent contact lens-induced astigmatism, proper fitting by an eye care professional is essential, along with giving the eyes a rest from lens wear each day.
Keratoconus
Keratoconus is an eye disease characterized by progressive thinning and bulging of the cornea. This cone-shaped protrusion of the cornea causes increasing irregular astigmatism. Keratoconus typically begins in childhood or early adulthood and worsens over time. As the cornea bulges forward, vision distortion from irregular astigmatism increases. Rigid gas permeable contacts can help early on, but a cornea transplant may be eventually needed in advanced keratoconus.
Pterygium
A pterygium is an overgrowth of pink tissue that extends onto the cornea from the white part of the eye. As this abnormal tissue grows, it may alter the regular curvature of the cornea, inducing astigmatism. Pterygium can cause astigmatism to gradually increase as the growth expands across the cornea. Surgical removal may be done for advanced cases affecting vision. However, pterygium often grows back after removal, continuing to worsen astigmatism.
Corneal Ectasia
Corneal ectasia refers to thinning and bulging of the cornea from conditions like keratoconus. Weakening of corneal tissue leads to a protrusion that alters the normal shape of the cornea. This results in irregular astigmatism that worsens as the ectasia increases. Corneal collagen cross-linking can strengthen the cornea and halt progression in some cases. But corneal transplantation may eventually be needed for visual rehabilitation in advanced ectasia.
Corneal Scarring
Scarring of the cornea, from trauma or infections like keratitis, can lead to worsening of astigmatism. Fibrous scar tissue forms irregular mounds that disrupt the smooth curvature of the cornea. Depending on the depth and severity of scarring, astigmatism may gradually increase over time. Mild superficial scars have less effect on vision. But deep stromal scarring creates significant visual distortion that may warrant cornea transplant surgery.
Genetics
Studies show genetics play a role in astigmatism progression. People who have family members with increasing astigmatism appear more prone to worsening over time themselves. Certain genetic disorders are also linked to progressive astigmatism, like Stickler syndrome, Marfan syndrome, and Down syndrome. The exact genes involved are still being investigated. But it is clear that hereditary factors influence changes in astigmatism, indicating a genetic predisposition in some people.
Diabetes
Uncontrolled diabetes can contribute to worsening astigmatism. High blood sugar levels damage nerves and change the shape of the eye over time. Diabetic retinopathy causes weakening of retinal blood vessels that may promote changes in the lens, distorting its shape. Diabetes also makes people more prone to eye infections, which can cause scarring and corneal irregularities. Tight control of blood sugar levels helps prevent diabetes-related eye damage that exacerbates astigmatism.
Glaucoma
Like diabetes, glaucoma is another eye condition that can accelerate astigmatism progression. Elevated pressure inside the eye damages the optic nerve in glaucoma. But this pressure can also lead to subtle changes in the shape of the cornea and lens. Glaucoma surgery may also induce astigmatism, since it involves incisions in the eye. Preventing vision loss from glaucoma may require corneal refractive procedures to correct worsening astigmatism.
Deformational Plagiocephaly
Babies who have deformational plagiocephaly, or flat head syndrome, are prone to developing astigmatism. The uneven pressure on one part of the skull in plagiocephaly alters ocular development, resulting in corneal asymmetry. The eye on the flattened side of the head is most often affected with increasing astigmatism. Wearing a molding helmet normalizes pressure and reduces risk of worsening astigmatism. Prompt helmet therapy allows proper eye and vision development.
Down Syndrome
People with Down syndrome have a high prevalence of astigmatism that worsens over time. The genetic defect that causes Down syndrome affects ocular development and corneal shape. Strabismus or misaligned eyes is also common, which can further increase astigmatism. Due to these factors, the vast majority of individuals with Down syndrome progress to high astigmatism and experience vision decline later in life. Regular eye exams allow early detection and correction of changing astigmatism in Down syndrome.
Marfan Syndrome
Marfan syndrome is a genetic disorder of connective tissue that commonly leads to progressive astigmatism. Abnormalities in fibrillin proteins compromise the structural integrity of ocular tissues. Over time, defects in the lens capsule cause it to take on an asymmetric shape, resulting in increased astigmatism. The cornea may also become abnormally steepened or irregular. Chronic eye inflammation from Marfan syndrome can also distort the cornea. Regular monitoring helps detect astigmatic changes requiring correction.
Corneal Warpage Syndrome
Corneal warpage syndrome consists of progressive astigmatism combined with corneal distortion from normal daily activities. Rubbing the eyes or eyelid pressure from blinking warps the shape of the cornea in this condition. Sleeping on one side may also asymmetricallly distort the cornea overnight. Those with corneal warpage syndrome often have increasing astigmatism that fluctuates day to day with activity. Custom rigid contact lenses can help stabilize the cornea in these patients.
Corneal Transplant Rejection
Astigmatism often worsens when a corneal transplant is rejected. Transplant rejection involves the immune system attacking donor corneal tissue. This triggers inflammation and scarring that distorts the cornea’s shape. Mild rejections may only cause temporary astigmatic fluctuations. But severe rejections can permanently scar and warp the transplanted cornea, leading to higher irregular astigmatism. Preventing rejection is key to avoid permanent corneal changes that increase astigmatism after transplant.
Radial Keratotomy
Radial keratotomy is an outdated refractive surgery that involved making spoke-like incisions in the cornea to flatten it. This technique often resulted in worsening astigmatism years later as scarring caused the radial incisions to gape open. The poorly healing incisions would disrupt the cornea’s curvature and cause visual distortion. Many who underwent this procedure experience gradual worsening of astigmatism over time. Modern laser vision correction like LASIK leads to much lower rates of astigmatism progression.
Table: Summary of What Worsens Astigmatism
| Factor | Description |
|---|---|
| Aging | Age-related changes to the cornea and lens distort their shape, increasing astigmatism. |
| Eye injury | Corneal scarring from injuries causes irregular curvature, inducing astigmatism. |
| Eye surgery | Incisions made during eye surgery can distort corneal shape and worsen astigmatism. |
| Contact lens wear | Rigid contact lenses may gradually warp the cornea over time, increasing astigmatism. |
| Keratoconus | This corneal bulging disease causes irregular astigmatism to steadily worsen. |
| Pterygium | Corneal tissue growth from pterygium alters curvature, worsening astigmatism. |
| Corneal ectasia | Corneal bulging from ectasia creates irregular astigmatism that increases with progression. |
| Corneal scarring | Scar tissue distorts the smooth corneal surface, leading to worsening astigmatism. |
| Genetics | A genetic predisposition likely contributes to progressive worsening of astigmatism in some people. |
| Diabetes | Chronic high blood sugar damages ocular tissues, promoting astigmatism progression. |
| Glaucoma | Pressure changes in glaucoma can alter corneal and lens shape, increasing astigmatism over time. |
| Deformational plagiocephaly | Uneven skull growth causes corneal asymmetry, leading to worsening childhood astigmatism. |
| Down syndrome | Genetic factors lead to high rates of progressive astigmatism in Down syndrome. |
| Marfan syndrome | This connective tissue disorder causes lens dislocation and distortion, increasing astigmatism. |
| Corneal warpage syndrome | Chronic warping of the cornea from everyday activities worsens irregular astigmatism. |
| Corneal transplant rejection | Immune rejection of donor cornea causes scarring and distortion, increasing astigmatism. |
| Radial keratotomy | Poor healing of surgical cornea incisions worsens astigmatism over time. |
Prevention
While some risk factors for progressive astigmatism cannot be controlled, the following preventive strategies may help slow worsening:
- Wear protective eyewear during sports or risky activities to prevent eye injuries that could distort the cornea.
- Maintain strict blood sugar control if diabetic to minimize diabetes-related ocular changes.
- Manage other conditions like glaucoma to avoid associated pressures on ocular structure.
- Choose updated laser vision surgery like LASIK instead of outdated radial keratotomy.
- Wear a helmet to correct head flattening and prevent asymmetric corneal changes in infants.
- Have annual eye exams to monitor for subtle shifts in astigmatism so new glasses or contacts can compensate.
- Select soft contacts instead of rigid lenses that may alter corneal shape with long-term wear.
While astigmatism progression often cannot be avoided completely, identifying those at high-risk allows closer monitoring and earlier treatment when changes occur.
Treatment
If astigmatism progresses and worsens, there are treatment options to improve vision:
- Glasses – Updated eyeglasses prescriptions help compensate for increasing astigmatism.
- Contact lenses – Either soft lenses or rigid gas permeable lenses can be fitted to neutralize changing astigmatism.
- Corneal relaxing incisions – Surgically making small incisions flattens areas of corneal steepening from irregular astigmatism.
- Toric IOLs – Astigmatism-correcting toric lenses can be implanted during cataract surgery.
- Corneal cross-linking – Using vitamin B2 drops and UV light halts the progression of corneal instability conditions.
- Corneal ring segments – Small plastic ring segments are inserted in the cornea to reshape abnormal curvature.
- Corneal transplant – Severely irregular and scarred corneas may require replacement to restore normal shape and vision.
Conclusion
While mild amounts of astigmatism are normal, excessive irregular astigmatism can significantly impair vision and worsen over time. Aging, genetics, injuries, and eye diseases contribute to changes in the cornea and lens that increase astigmatism. Preventive strategies like eye protection and blood sugar control can help avoid exacerbating factors. Regular eye exams allow early detection of progression so new prescriptions can optimize vision. For severe cases, corneal refractive procedures or transplant surgery may be required to restore vision distorted by worsening irregular astigmatism. With a combination of prevention, regular monitoring, and treatment, the impact of astigmatism progression can be limited.
