enhancement of emmetropization in highly hyperopic infants

Conditions: Hyperopia

Summary: infants do not usually wear glasses because they usually do not need them to see clearly. most infants are born with a moderate amount of farsightedness. most infants then undergo a natural process called 'emmetropization' that reduces the amount of farsightedness. however, up to 10% of infants don't emmetropize and end up with very farsighted prescriptions. farsighted infants must use extra focusing effort to see clearly, which may make their eyes cross and perhaps cause a "lazy eye". if infants avoid this effort and their vision stays blurred into childhood, they may develop two lazy eyes. farsightedness in school-aged children makes reading and learning more difficult. new studies in animals and in humans show that infant eyes will emmetropize best if they have just a normal, moderate amount of farsightedness. the infant eye must be in this normal target zone in order to emmetropize. if a baby were given glasses with the full prescription to correct all of his farsightedness, the eyes would also be out of the target zone and would not receive any signal to grow. the best strategy might be to give a partial spectacle correction for the farsightedness, just enough to put them in the zone that is most effective for emmetropization. the purpose of this project is to determine if emmetropization can be enhanced in very farsighted babies. we will give them glasses with a partial correction and accommodative (eye focusing) training. the partial correction is an amount that is less than their full degree of farsightedness but enough to put them in the zone of effective emmetropization. as changes in farsightedness occur, the power of the glasses will be reduced to keep the farsightedness within the target zone. if an infant reaches a normal amount of farsightedness, the glasses will be discontinued. the comparison group will be farsighted babies who receive the current standard of care, namely no correction. the main outcome of the study will be whether there is a significant difference in the decrease of farsightedness between the two groups when the infants are 18 months of age. if emmetropization can be enhanced in very farsighted babies, the risk of developing crossed or lazy eye will be reduced. the lifelong need for spectacles, contact lenses, or refractive surgery for high amounts of farsightedness would also be reduced. positive results might also make infant eye examinations more common and place a new therapeutic option in clinicians' hands.


Eligibility criteria:
inclusion criteria: * age: between 8 and 15 weeks at baseline examination * either gender * any ethnicity * birthweight greater than 2500g * normal pregnancy and delivery (including cesarean section delivery but excluding serious complications or conditions such as eclampsia or rubella) * hyperopia greater than or equal to +5.00 diopters (d) in the spherical component of refractive error in one or both eyes measured with cycloplegic retinoscopy using 1% cyclopentolate * infants with a refractive error of greater than or equal to +5.00d but less than or equal to +7.00d in the spherical component of refractive error will be randomized to treatment (partial correction with accommodative training) or observation only. * infants with greater than +7.00d in the spherical component of refractive error will receive treatment exclusion criteria: * astigmatism greater than 2.00d in either eye * anisometropia greater than 1.50d (spherical equivalent) * history of strabismus surgery * history of difficulty with pupillary dilation * history of cardiac, liver, asthma, or other respiratory disease * history of ocular disease, retinal detachment, severe macular dragging, intraocular surgery, optic nerve hypoplasia, malformations of the eye, cortical visual impairment or active inflammation * history of hydrocephalus, down syndrome, cerebral palsy, developmental delay, seizure disorders

Keywords: emmetropization refractive error glasses accommodation