Emmetropisation, squint, and reduced visual acuity after treatment.

Abstract

In a sample of children used to assess the value of optical correction of hypermetropia from the age of 6 months the refraction of the most hypermetropic meridian frequently became less than 3'5 D as the children grew. When this occurred, the incidence of squint was significantly less (p<0001) and the last known acuity after treatment was significantly better (p<0001) than when it did not. This process of emmetropisation appears to have been impeded by the consistent wearing of hypermetropic spectacle correction from the age of6 months. When we assessed the results of our trial of optical correction of hypermetropia from the age of 1 year' we suspected two things: (1) the children who squinted were those who remained hypermetropic, but if the initial level of hypermetropia in a child decreased the prognosis for squint and amblyopia was better; (2) children drawn for treatment with spectacles appeared to remain hypermetropic. We could not prove either ofthese suspicions, principally because we did not know what was a 'normal' amount of hypermetropia at a given age. We therefore decided to look again for an association between reduction of hypermetropia and the visual outcome in children included in our recent trial of treating hypermetropia from the age of 6 months.9 In order to do this we arbitrarily chose a level of hypermetropia below which we deemed that emmetropisation occurred. Since the criterion for entry into this trial was the level of hypermetropia in the most hypermetropic meridian of a pair of eyes, we continued to use this method of recording hypermetropia. We also report observations on the possible effect of wearing spectacles on the process of emmetropisation. Patients and methodsThe sample of children is the one reported in our trial of treating abnormal hypermetropia with spectacles from the age of 6 months9 in an attempt to prevent squint and amblyopia. Details of the protocol used to conduct that trial were reported in that paper.9 Three hundred and seventy two infants, aged 6 months, with +4-00 or more dioptres hypermetropia in one or more meridia of either eye were randomly allocated treatment with spectacles or no treatment, and followed up as effectively as possible. If a child in either group developed a squint, or was found (usually at age 31/2 years) to have reduced visual acuity, he/she was treated conventionally with spectacles, occlusion, or operation as appropriate. The presence of squint was diagnosed with the cover test. Visual acuity was recorded only with Linear Sheridan-Gardiner or Snellen tests. All the refractions were done by the same person (RMI) after cycloplegia with cyclopentolate 1%. The refraction reported is the amount of hypermetropia in the most hypermetropic meridian after + 1-75 D has been subtracted from the retinoscopy findings of all meridia of a pair of eyes. Information abut the refractions, presence of squint, and the last known visual acuity after any additional treatment had been given is now available for 287 of the children.The first purpose of ...

Inheritance of strabismus and the gain of using heredity to determine populations at risk of developing strabismus

“…We found a relative risk increase of somewhat lesser magnitude among those with a family history of strabismus (Table 1b) than expected (odds ratio ∂3). On the other hand, using the combination of heredity and high hyperopia, where the latter is a risk indicator for visual defects (squint and amblyopia) pointed out by Ingram and co-workers (Ingram et al 1991;Ingram 1979), the risk for strabismus was more than doubled compared to heredity alone (odds ratio ∂7). Another important difference between the groups with and without heredity is the distribution of different types of strabismus.…”

“…This process, emmetropization, seems to be important for the development of the growing eye. Lack of emmetropization is related to a significantly increased risk for developing squint or amblyopia (Sjö strand & Abrahamsson 1991;Abrahamsson et al 1991;Ingram et al 1991).…”

Vision screening in preschoolers: the New South Wales Statewide Eyesight Preschooler Screening program

“…The earlier study found that the process of emmetropisation appeared to have been impeded by the consistent wearing of spectacle correction from the age of six months. [93] The later study found that a small, temporary effect of refractive correction occurred between nine and 18 months of age, but had disappeared by 36 months. [94] The US Preventive Services Task Force systematic evidence review found that it was unclear whether treating young children with refractive errors associated with amblyopia would prevent the development of amblyopia.…”

The assessment and management of strabismus and amblyopia: a national audit

“…[35][36][37][38][39] Increasing astigmatism, oblique astigmatism and presence of strabismus have the highest relative risk. 36,39,40 The benefit of early detection and treatment of refractive errors has also been the subject of considerable debate, [41][42][43] with evidence both for and against early correction. 41,44 Thus, the appropriate management of a child with a refractive error depends on the age of the child, the type of refractive error and the presence or absence of strabismus.…”