Myopia

Useful Terms

Myopia = the medical designation of the condition known as nearsightedness, in which closer objects appear to be clear but objects in the distance seem to be blurred; is considered to be an eye focusing disorder and not an eye disease; affects almost a quarter of the American population

Low myopia = a mild form of myopia

High myopia = a severe case of myopia; a risk factor for the development of retinal detachment, glaucoma, and cataracts

Common Symptoms

  • They are usually apparent in children between the ages of 8 and 12
  • Those children with myopia suffer from:

    • A need to rub the eyes frequently
    • A need to blink excessively
    • A need to sit closer or hold objects closely in order to see them properly
    • An unawareness of objects that are in the distance
    • A need to squint persistently and constantly in order to see properly
  • Myopia becomes much worse during adolescence, which is when the body starts to undergo major changes
  • Very little change occurs during the adulthood years, ages 20 – 40
  • Blurred vision when looking at objects or people in the distance
  • A need to squint regularly in order to see properly
  • Great eyestrain
  • Headaches caused by great eyestrain
  • Difficulty with seeing during the nighttime, usually when driving (night myopia)

Risk Factors

  • Hereditary

    • A family history of myopia makes it much more likely to pass the disorder on to children and future descendants
  • Close Work

    • Myopia is more common in those people who read a lot and/or do other close work

Causes

  • Normal vision comes from a collaboration of the tear film, lens, and cornea within the eye
  • They are responsible for the refraction (bending) of light rays that the eye receives in such a way that they are properly focused onto the retina

    • The retina then converts the light rays into electrical signals and transmits them into the optic nerve on the way to brain, which interprets them as images
  • Uneven Curvature

    • Vision is normal only when the lens and cornea are flawlessly and uniformly curved
    • If the eye is abnormally long, or the cornea is too steep, then the light rays will be improperly refracted in front of the retina rather than onto it

      • This constitutes a refractive error, of which myopia is one, along with astigmatism and hyperopia (farsightedness)
    • Although vision of objects and people in close proximity is normal, it is this refractive error that is responsible for a blurring of vision when attempting to look at objects or people in the distance

Diagnosis

  • Comprehensive Eye Examination

    • Myopia can be detected in the routine eye examination
    • Letter Charts

      • The patient reads off letters at a certain distance away from the eyes in order to measure visual acuity and clarity
    • Retinoscope

      • This instrument shines a special bright light into the eyes as a way of examining in what way light reflects off of the retina
      • As the light comes back from within the eye, then it will be able to more accurately and with more certainty distinguish between if the patient is experiencing myopia or hyperopia
      • It should only be used once myopia has been found and the ophthalmologist wants to discover the root cause of the myopia
    • Phoropter

      • This is that device in which the patient looks through different sets of lenses and identifies which of the two pairs of lenses in each set offers clearer vision
      • The Phoropter thus helps measure the extent of the existing refractive error and determine the appropriate prescription for eyeglasses or contact lens as a means of correcting it

Treatment

  • Those with high myopia will usually find that it has stabilized between the ages of 20 and 30 years
  • High myopia is very correctable through the means of utilizing eyeglasses, contact lenses, or refractive surgery

    • Eyeglasses and Contact Lenses

      • These are the most common treatment methods
      • They correct for the condition by refocusing the light rays onto the retina as they should be and offset the abnormal length of the eye and/or irregular corneal curvature

        • Eyeglasses are also able to correct other vision problems simultaneously alongside myopia, such as astigmatism or cataracts
      • Eyeglasses have a great variety of styles to choose from, are easy to use, and may be the most cost-effective of the various treatment methods
      • Contact lenses also have a lot of diversity in that there are those that soft, hard, for extended-wear, disposable, rigid gas permeable (contact lenses made of durable plastic that transfer more oxygen to the eyes than do other contact lenses), and bifocal
      • Orthokeratology

        • Hard contact lenses are applied to the eyes as a means of overnight corneal reshaping lenses

          • The cornea will progressively flatten out and the refractive error experienced is mitigated
        • Any improvement of vision gained from this procedure is only temporary

          • Once the lens are discontinued of their usage, the cornea will regress to its earlier, abnormal curvature and the myopia will recur
    • Refractive Surgery

      • Vision is rectified or enhanced by reshaping the corneal curvature into something more normal, which effectively modifies the light focusing ability within the eye
      • LASIK

        • A small, circular incision is made in part of the cornea to make a flap of sorts
        • A laser is then used to destroy layers from the corneal center as a way of flattening its irregular, domed shape
      • LASEK

        • A small incision is made in the corneal epithelium (serves as the thin and protective cover for the cornea) to make a flap
        • A laser is then used to reshape the outer layers of the cornea by flattening the irregular, domed curvature
        • This is followed by the repositioning of the flap within the epithelium
        • The flap is healed over with the usage of a bandage contact lens over the course of several days after LASEK has been performed
      • Photorefractive Keratectomy (PRK)

        • This surgery follows the same procedure as LASEK, save for the removal of epithelial flap
        • It will grow back naturally on its own with time and adapt itself to the changed corneal shape
        • It too requires the usage of bandage contact lenses for a healing period of several days after the procedure is done
      • Intraocular Lens Implant (IOL Implant)

        • This is a viable treatment method for those who suffer from a moderate form of myopia or even high myopia
        • Lenses are surgically implanted in front of the natural lens within the eye