Abstract
Visual fields in the pediatric population are an essential part of the eye exam that remain challenging to even the most experienced clinicians. Becoming educated in the multiple ways a child's visual field can be tested regardless of age and cognitive and physical abilities will allow the clinician to gain better insight into the child's function and in some cases, allow the clinician to identify pathological or neurological anomalies in the visual pathway. Gross visual field or functional visual field extent can be estimated by tests such as confrontation visual field testing, finger counting field testing, and white sphere kinetic perimetry. For threshold measurements of a child's visual fields, the Goldmann perimeter, or the more advanced computerized tests such as the Humphrey perimeter, Octopus perimeter, or frequency doubling technology perimeter can be used. Modifications can be made to certain tests to better suit the child's cognitive and physical abilities. The chapter covers different methods of visual field testing specific for the pediatric population.
TopBackground
Children with physical or developmental disabilities are at a significantly increased risk of visual acuity deficits, visual field defects, or a combination of both (Van den Broek et al., 2006; Warburg, 1994). Examples of these include pre- or post-natal injury as a result of perinatal hypoxic-ischemic brain injury or because of complications of hydrocephalus, systemic infections, traumatic brain injury, retinopathy of prematurity, optic nerve damage, progressive retinal degeneration, or tumors of the optic chiasm. (Gilbert et al., 2003; Rahi & Gilbert, 2005).
When it comes to visual field testing in children we can divide it up into two different types: the traditional methods and the modified methods.
Traditional Visual Field Methods
The traditional methods are effective for children that are able to respond to instructions and give accurate feedback. These are straightforward in testing and interpretation of the results are relatively easy. Tests that fall under this category include confrontation visual field test, finger counting visual field test, Goldmann perimetry, frequency doubling technology perimetry, and automated perimetry such as the Humphrey Field Analyzer and Octopus 900.
Modified Visual Field Methods
The modified methods are usually reserved for children that are unable to respond either verbally, or physically (pointing, gesturing, or pressing buttons). These children also do not follow instructions well. Modified methods of perimetry takes the traditional methods and re-adapts the tests to be used for the child being tested. It takes some experience to administer the test and interpretation may not be straight forward. Modifications cannot be made to all tests but can be made to the following: confrontation visual field test, finger counting visual fields, Goldmann perimetry and Octopus perimetry.
Key Terms in this Chapter
Perimetry: A method of measuring a patient’s visual field. Can be adapted to many different types of techniques.
Kinetic Perimetry: Perimetric test based on a moving peripheral stimulus.
Static Perimetry: Perimetric test based on fixed locations of peripheral stimuli being presented
Monocular Field Extent: Visual field measured when one eye is occluded.
Arc Perimeter: An alternative to the traditional dome perimeters such as the Humphrey or the Goldmann. The arc perimeter is made by joining 2 steel semi-circular arcs at a 90-degree array. This creates 4 arms at the 45, 135, 225, 315-degree meridians. The functional visual field test is carried out based off the 4 main meridians.
Binocular Field Extent: Visual field measured when both eyes are open.
Visual Field: How sensitive and to what extent a patient’s spatial awareness is under conditions where the eye is fixated on a single area and there is no movement. Typically, more restricted nasally (55–60 degrees) than temporally (90–100 degrees).