Astigmatism occurs when the cornea or lens is abnormally shaped. For example, if the cornea is more curved in one direction than another, it may resemble a football more than a basketball. This causes images to be incorrectly projected onto the retina, and vision to be blurry, distorted or even double. Near and distance vision are affected. Sometimes uncorrected patients adopt a face turn to improve the clarity of vision by using the bridge of the noses as a pinhole. Astigmatism is treated with glasses, contact lenses, refractive surgery on the cornea or with toric (astigmatism-correcting) intraocular lenses.
Hyperopia (hypermetropia), or farsightedness, is a type of refractive error for which distant objects may be seen more clearly or focused upon more easily than near targets. Images are focused behind, rather than on, the retina because the eye is too short, the ciliary muscles are too weak, or the cornea or lens is too flat. The need for glasses depends on the severity of the farsightedness, the strength of the focusing (ciliary) muscle, and the flexibility of the lens. In general, the younger the person the stronger the focusing muscles and the softer the lens. Thus, children are often able to accommodate for this condition without the need for correction unless the magnitude is significant enough to impact vision or eye alignment or to cause symptoms.
For example, some children demonstrate 20/20 vision of each eye without correction in the office, but they have frequent headaches, especially at the end of a school day, which resolve after they wear correction for at least a portion of their farsightedness. Other children seem to see fine according to their parents but were brought our office because their eyes cross, and they are often found to have one eye that sees better than the other. Glasses with some or all of their farsightedness controls the eye crossing, and frequently amblyopia treatment in addition, corrects the amblyopia. Adults with hyperopia have more difficulty compensating for their farsightedness, especially as they become older because their lenses become harder as they age.
Myopia, or nearsightedness, is a type of refractive error. People with nearsightedness can usually see close objects clearly, but objects that are far away may appear blurry or difficult to distinguish. Myopia is typically easily corrected with glasses or contact lenses.
Due to the proliferation of myopia in developed countries, treatments to slow or stop the progression of the myopia are becoming more popular. Atropine in the Treatment of Myopia studies (ATOM1 and ATOM2) have shown that chronic use of low-dose atropine 0.01% drops is an effective and straightforward solution to slow the progression of pathological or routine myopia. Special contact lenses worn at night to reshape the cornea are effective only if the patient strictly adheres to the wearing regimen and the results are often reversed once the lenses are discontinued.
Surgical procedures performed upon adults to correct nearsightedness include procedures to reshape the cornea (the clear-domed window at the front of the eye) such as LASIK (laser-assisted in situ keratomileusis), PRK (photorefractive keratectomy) or EpiLASIK (a modified combination of the two). Alternatively, myopia can be addressed by changing the lens power with phakic intraocular lenses (implantable contact lenses) or refractive lens exchange (clear lens extraction with intraocular lens implantation). Although refractive surgery is rarely performed on children, it can be helpful in children with marked amblyopia in one eye because of a very large difference in refractive error between the child’s two eyes and which is unresponsive to conventional amblyopia treatment (including patching, eyedrops, fogging lenses and/or glasses/contact lenses), for which the child is noncompliant with amblyopia treatment, or for which the child did not receive amblyopia treatment early but is in the mid to late amblyogenic period.