A perspective on psychophysical testing in children

[Timing of congenital cataract surgery : Amblyopia versus aphakic glaucoma]

A congenital cataract is a rare disorder, which is associated with a high risk of amblyopia. Ophthalmologists are faced with many diagnostic and surgical challenges in the management of this disease. Older children can undergo primary treatment with an intraocular lens, whereas children younger than 12 months of age usually initially remain aphakic. The most frequent long-term complication of aphakic eyes following congenital cataract surgery in connection with posterior capsulorrhexis and anterior vitrectomy is aphakic glaucoma, which in individual cases can lead to substantial impairment of vision. Many factors have been reported to increase the risk of postoperative glaucoma, including microphthalmos, fetal nuclear cataract, conspicuous family history and associated ocular malformations, such as persistent fetal vasculature (PFV). Cataract surgery during early infancy is well-established to be the most important factor for the formation of postoperative aphakic glaucoma. In individual treatment planning it has to be considered that although younger age at the time of cataract removal can provide better prerequisites for prophylaxis of amblyopia, it also confers a higher risk of development of aphakic glaucoma. Children undergoing congenital cataract surgery have to be regularly monitored given the lifelong risk for postoperative complications, such as aphakic glaucoma.

Early diagnosis of amblyopia

Amblyopia can be improved or eliminated more easily when treated early in life. Because amblyopia in older children is generally less responsive to treatment (Holmes et al., 2011), there is a premium on the early identification of amblyopia and its risk factors and the subsequent treatment thereof. Clinical preference is to institute treatment in children before 7 years of age when an optimal visual outcome is typically easier to obtain.

Preschool vision screening: rationale, methodology and outcome

Although population outcome studies support the utility of preschool screening for reducing the prevalence of amblyopia, fundamental questions remain about how best to do such screening. Infant photoscreening to detect refractive risk factors prior to onset of esotropia and amblyopia seems promising, but our current understanding of the natural history of these conditions is limited, thus limiting the prophylactic potential of early screening. Screening for strabismic, refractive and ocular disease conditions directly associated with amblyopia is more clearly proven, but the diversity of equipment, methods and subject populations studied make it difficult to draw precise summary conclusions at this point about the efficacy of photoscreening. Sensory-based testing of preschool-age children exhibits a similar combination of promise and limitations. The visual acuity tests most widely used for this purpose are prone to problems of testability and false negatives. Moreover, the utility of random-dot stereograms has been confused by misapplication, and new small-target binocularity tests, while attractive, are as yet inadequately field-proven. The evaluation standard for any screening modality is treatment outcome. However, variables in amblyopia classification and quantitative definition differences, timing of presentation, nonequivalent treatment comparisons, and compliance variability have been uncontrolled in virtually all extant studies of amblyopia treatment outcome, making it difficult or impossible to evaluate either the relative efficacy of different treatment regimens for amblyopia or the effects of age on treatment outcome within the preschool age range. The latter issue is a central one, since existence of such an age effect is the primary rationale for screening at younger rather than older preschool ages. The relatively low prevalence of amblyopia makes it difficult to achieve a high screening yield in terms of predictive value, but functionally increasing prevalence by selective screening of high risk populations causes further problems. Unless a "supertest" can be devised, with very high sensitivity and specificity, health policy decisions will be required to determine which of these two characteristics should be emphasized in screening programs. Performance of screening tests can be optimized, however, with adequate training, perhaps via instructional videotapes.

Methodology for a randomised controlled trial of preschool vision screening. A new approach with the 'ALSPAC' project

We present the methodology of a population-based Randomised Controlled Trial, comparing an intensive programme of primary preschool vision screening by orthoptists with the usual non-specialist screening. The aims of the trial are to compare the effectiveness and costs of intensive orthoptic screening with non-specialist measures. The orthoptic screening programme will be evaluated both as a composite package and in terms of the screening value of the individual tests at specific ages. This trial is nested within a large population-based longitudinal study. Additional demographic and developmental data on the children in the trial are therefore available. The results of the trial will be used to help clarify which methods of preschool ophthalmic population screening are best in terms of disease detection and cost efficiency.

The development of visual acuity in the peripheral visual field of human infants: binocular and monocular measurements

We measured binocular and monocular grating acuity in the peripheral visual field of infants, using a modified preferential looking procedure. Both binocular and monocular peripheral acuity increased between 2 and 11 months of age, but had not reached adult levels at the end of the first year of life. Binocular acuity was always higher than monocular acuity. At all ages tested, acuity was higher in the temporal than in the nasal visual field. We conclude that, in spite of the relative morphological maturity of the peripheral retina, visual acuity develops in the peripheral visual field.