In order to prescribe correction in children, and after considering visual sharpness, integrity of the anterior segment and motor state, there must be considered the magnitude and the orientation of astigmatism regarding age and ethnic group of the patient. When there is lack of anisometropy, astigmatism with rule should be corrected if they are higher than 2.50 dioptres. As oblique astigmatisms and against rule have a higher ambliopizante risk, lower magnitudes might be taken into account when giving prescription. In case of anisometropy equal or higher to 1 dioptre correction has to be provided.

The evaluation of the visual human function includes the visual acuity, field of vision and sensibility to the contrast, this test can be used as test of routine when the achievements of the patient do not reach the results we have been waiting for. The development of the sensibility to the contrast in children has an important ripeness during the first 3 months of age, towards the majority of the spatial frequencies, a function of sensibility is achieved to the comparable contrast with that of the adult about 6 months of age. Though the sensibility to the contrast (SC) can have a relative value for screening and diagnosis, one recommends doing it as part of the functional valuation, specially, in the valor in patients of low vision or multiple disabilities and SC’s test designed for them. The SC they give us an useful information, revealing some conditions in the losses of vision are identifiable across the test of visual acuity (AV), providing a method for with monitoring treatment and a better understanding of the interpretation of the visual problems found in patients with alteration of the vision (Owsley, 2003)

Emmetropization is defined as the tendency of the optical device eye towards emmetropia by a correlation of individual optical elements, since the child is born with different optical elements that influence the targeting of retinal images and according to its dioptric power as the cornea and lens or length for the anteroposterior axis. It is observed the child at birth has a degree of farsightedness and as it grows the optical power is adjusted so that more or less in preschool refractive status is zero. However, this process can be affected by genetic influence, because of visual deprivation as observed in animal experiments or by mechanical pressure in the eyeball. Additionally, the values of refraction in different ages have been determined statistically and clinical significance in deciding whether there is optical correction according to the physiological values determined by age and allows us to relate whether a prescription or not optically alter the emmetropization process.

<em><strong>Objective</strong><em> to determine the reference values of visual acuity, refractive status, corneal curvature, stereopsis and color vision in children between the ages of three and seven in the locality of Chapinero in Bogota. <em><strong>Materials and methods</strong><em> cross-sectional descriptive observational study. The population under study consisted of schoolchildren between the ages of three and seven (200 children). Measurements included visual acuity (VA) with the Lea Symbols and HOTV tests, cycloplegic refraction, keratometry with Nidek KM-500 autokeratometer, color vision with Color Vision Testing Made Easy and stereopsis with Randot test. <em><strong>Results</strong><em> The median visual acuity in all age groups was 0.00 (20/20). One hundred percent of the children had hypermetropia (spherical equivalent for astigmats of up to 1.00 Dpt). The medium refractive error was + 0.75 in the groups of three and four-years-old, +0.50 in the groups of five and six-year-old children and +0.62 in the group of seven-year-old children. The median corneal curvature in the horizontal meridian was 42.62 and 41.50 for the vertical meridian of three and four years, 42.75 horizontal meridian and 43.75 the vertical of five and six years, and 41.50 and 42.50 at seven-years-old. All had normal color vision. The median stereopsis was twenty-five arc seconds for three and four-year-old children, twenty arc seconds for five and six-year-old children and twenty-five for the group of seven-year-old children.