Photorefractive Keratectomy for Severe Anisometropia and Isoametropia Associated With Amblyopia
Photorefractive Keratectomy for Severe Anisometropia and Isoametropia Associated With Amblyopia
Photorefractive keratectomy (PRK) with excimer laser has been used successfully to treat
 myopia, hyperopia, and astigmatism in adults for over 30 years. Children with high refractive
 errors that go untreated will develop severe amblyopia. PRK can normalize high refractive
 errors and potentially improve the amblyopia in affected children. The purpose of this study
 is to investigate whether children with high anisometropia or isoametropia with amblyopia
 that are nonresponsive to standard therapy and receive PRK develop better longterm visual
 acuity.
Anisometropia is a condition in which one eye has a significantly different refractive error
 from the other and commonly leads to the development of refractive amblyopia in the affected
 eye. High isoametropia is the condition in which both eyes have high refractive error and
 commonly leads to bilateral refractive amblyopia if untreated. Amblyopia is the condition in
 which vision does not develop fully in the brain due to disuse or misuse of one or both eyes.
 Typically, in high anisometropia, a contact lens in the eye with the stronger refractive
 error and/or glasses must be used to correct the refractive error. Commonly, infants and
 children with this condition refuse to wear the contact lens or glasses because the other eye
 sees normally. There are other problems in treating high anisometropia with glasses. One is
 aniseikonia, the condition of image size disparity between the two eyes. This causes
 difficulty for the brain of the affected person to fuse the images from the two eyes because
 the image from one eye is much larger than that from the other eye. This results in
 asthenopia (eye fatigue) and sometimes even diplopia. If the anisometropia is severe,
 significant amblyopia will result in the eye with the stronger refractive error and, if not
 treated at an early age, permanent and potentially severe vision loss will result.

 In high isoametropia, contact lenses or glasses must likewise be used in order for normal
 vision to develop. Most children with isoametropia will wear glasses well because they cannot
 see well without them. By contrast, children with developmental delays, chromosomal
 abnormalities, autism, or attention deficit hyperactivity disorder and high isoametropia very
 commonly will not wear the needed refractive correction due to strong tactile aversion to
 anything touching the face or head. If the refractive error is high, significant bilateral
 (isoametropic) amblyopia will result and, if not treated at an early age, permanent and
 potentially severe vision loss will result.

 PRK can normalize high refractive errors and potentially improve the amblyopia in affected
 children. The purpose of this study is to investigate whether children with high
 anisometropia or isoametropia with amblyopia that are nonresponsive to standard therapy and
 receive PRK develop better longterm visual acuity. Secondary outcomes are stability of
 refractive correction, and corneal health.
Inclusion Criteria:.

 -  Children aged 2 to 17 with significant anisometropia or isoametropia and amblyopia
 that have failed traditional treatment for at least 6 months.

 -  Anisometropic group:

 -  The anisometropia must be at least 3.00 diopters.

 -  The amblyopic eye best corrected visual acuity must be at least 2 lines worse than the
 fellow eye in verbal children

 -  Isoametropic group

 -  Myopia must be at least -4.00 diopters in both eyes

 -  Hyperopia must be at least 4.00 diopters in both eyes

 -  Astigmatism must be at least 2.50 diopters in both eyes.

 Exclusion Criteria:

 -  History of significant corneal abnormality that, in the investigator's opinion, may
 limit visual rehabilitation.

 -  History of known collagen disorder

 -  History of known corneal ectasia

 -  History of previous herpes simplex keratitis

 -  Corneal thickness of less than 450u