The severity of astigmatism is generally determined by the amount of diopters (the unit used to measure the refractive power of an optical system) present in the eye. A higher number of diopters corresponds to a higher degree of astigmatism. A refractive error of 5.50 diopters is considered to be moderate to severe, as it falls within the range of 4.00 to 6.00 diopters which is generally considered to be the range of astigmatism that would require corrective lenses.
At 5.50 diopters, astigmatism can cause significant blurring of vision, and can lead to problems with depth perception and visual acuity. Symptoms of astigmatism at this level could include headaches, eyestrain, and difficulty in focusing on objects at a distance or up close. People with astigmatism may also experience difficulty in seeing objects clearly at night, or have an increased sensitivity to bright light.
The good news is that astigmatism can generally be corrected with eyeglasses, contact lenses, or laser vision correction. However, the best course of action for someone with astigmatism of 5.50 diopters will depend on their individual needs and lifestyle, and should be discussed with an optometrist or ophthalmologist.