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Myopia, also known as nearsightedness, is an eye condition in which people have difficulty seeing objects that are far away, but can clearly see objects that are in close proximity. People with high myopia have a high degree of nearsightedness and need objects to be very close in order to see them clearly. Myopia is usually corrected with glasses, contact lenses, or surgery.
In myopic individuals, the eyeball is excessively long, or the cornea is overly curved. This means that light rays fail to bend in the correct way when entering the eye, which is called a refractive error. The myopic eye cannot focus sufficiently to see distant objects clearly.
High myopia can be easily diagnosed in an eye care office by an ophthalmologist or optometrist. Vision deficiencies are measured in diopters, with positive numbers indicating farsightedness or difficulty seeing close up, and negative numbers indicating myopia. Higher numbers, either positive or negative, indicate a greater degree of deficiency. People with high myopia have prescriptions above -6.0 or -8.0 diopters. Prescriptions can go up to around -35.0, which would indicate a very high degree of myopia.
Myopia tends to run in families, and often develops in childhood. Sometimes it degenerates, or gets steadily worse with age, and often it plateaus after a person is done growing.
High myopia is particularly likely to degenerate or result in damage to the eye, which can lead to sight loss in rare cases. This can occur because the lengthening of the eyeball puts stress on the retina, causing it to detach or become damaged. High myopia may also be associated with cataracts and glaucoma. People with high myopia should have regular eye exams and notify an eye care professional of any changes in their vision or eyes.
There are a few different treatments for high myopia. Usually, the treatment of choice is contact lenses. Glasses for high prescriptions need to be very specifically and carefully designed so that they exactly suit the eyes of an individual. The lenses for the glasses must also be fairly thick, although advances in lens-making have greatly reduced this. Contact lenses for high prescriptions reduce the vision errors that glasses of the same prescription can cause, such as making everything look smaller than it really is.
Surgery is also an option for people with this eye condition. The most common is laser-assisted in situ keratomileusis (LASIK) eye surgery, in which a laser cuts a flap in the cornea and removes some corneal tissue, allowing light to bend correctly when it enters the eye. Another option is corneal rings, in which plastic rings are implanted into the eye to alter its shape. The plastic rings can be removed if necessary, or changed if a person's prescription changes. As with any surgery, these procedures do hold some risks and are not suitable for all patients.