Astigmatism is a common vision disorder: a type of refractive error, in which the eye doesn’t focus the light evenly onto the retina. It represents an irregularity in the curvature of the cornea—similarly to a wobble in a ball—which causes the images on the retina to be distorted and blurs the vision.
Astigmatism affects both adults and children. Slight astigmatism may not induce a dramatic change in the vision and many patients don’t even realise they might have it. A recent study of over 2,500 American children (aged 5-17) found out that more than 28% had astigmatism of 1.0 diopters or greater. Another study looked at over 11,000 eyeglass wearers in the UK, of which 47.4% had astigmatism of 0.75 diopters or greater in at least one eye, and 24% had the same amount of astigmatism in both eyes. In Europe and Asia, it’s estimated that between 30 and 60% of the adult population has corrected or uncorrected astigmatism.
The good news is that while astigmatism is fairly prevalent, it can be easily corrected with spectacles or contact lenses (toric lenses). However, if looking for a long-term solution, currently one of the best options is to have astigmatism corrected during routine cataract surgery.
A cataract is a clouding of the clear lens of the eye, common in elderly individuals. To remove it, patients undergo a cataract extraction surgery, during which they can opt in to correct their astigmatism as well. The eye’s cloudy natural lens can be replaced with a special type of intraocular lens (IOL) or a toric IOL. The toric IOL works like the standard toric contact lens: it has different powers in different meridians to correct the unequal amounts of far-sightedness and near-sightedness in the different parts of the eye that cause astigmatism.
Improved vision is, naturally, the biggest advantage of the toric lens implants. The lenses are implanted directly in the eye and are very effective at correcting astigmatism. Since all it takes is single implantation, patients often save a significant amount of money on spectacles or reordering standard toric contact lenses. Lastly, the toric IOL has one major advantage over toric contacts: because it’s positioned securely inside the eye, it provides a more stable astigmatism correction than the contact lens (which often moves around the eye with every blink).