Photorefractive Keratectomy for Severe Anisometropia and Isoametropia Associated With Amblyopia

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