Astigmatism occurs when the cornea or lens has unequal curvature in different meridians, preventing light from focusing to a single sharp point. This causes blurred or distorted vision at all distances.
Causes
Most astigmatism is due to inherited corneal shape and remains relatively stable. Irregular forms can result from keratoconus, corneal scars, surgery, or trauma, and lenticular astigmatism arises from lens changes.
- Regular astigmatism is common and easily corrected with spectacles or toric lenses
- Irregular astigmatism may require rigid or specialised contact lenses
- Progressive thinning disorders such as keratoconus cause increasing, asymmetric astigmatism
- Certain eyelid conditions or pressure can temporarily alter corneal shape
Clinical Impact
Uncorrected astigmatism leads to eye strain, headaches, and reduced clarity, particularly for fine detail. Accurate refraction and corneal topography guide diagnosis and management.
- Children with significant astigmatism need early correction to prevent amblyopia
- Monitoring is important when astigmatism changes rapidly or asymmetrically
- Refractive surgery can correct suitable regular astigmatism
- Contact lens fitting must account for stability and axis alignment
