Assessing visual fields in young patients is testing – OCT may be a good place to begin.
The biggest challenge in visual field testing is recognizing when a child might have a visual field problem. A variety of symptoms may be hints, including problems locating words, difficulty reading as confirmed by missing out on words or hemifield slip, problems through examinations as the result of skipping letters, not reading an entire line, or seeing one number of the Ichihara test when there are in fact two.
A doctor pointed out that physicians must realize that some kids make up for their visual field defects, with, for example, head turns pertaining to visual area loss that are not related to strabismus.
“They may have head turning or head thrusting toward the non-seeing area or use of touch to assist moving around, as at a young age, children tend to make up for the defect” said the doctor.
Some children can have associated motor or sensory deficits, for example, youngsters with cerebral palsy might have a hemiparesis on the side of the visual field deficit and these need to be examined.
Children with a well-known central nervous system abnormality that consists of optic pathway, periventricular leukomalacia, glioma perinatal stroke, pituitary adenoma, craniopharyngioma, encephalomalacia, or some other well-known systemic or genetic irregularity, such as neurofibromatosis, ought to undergo visual field testing, to see if these symptoms can also be taken care of, the doctor pointed out.
Other indications for visual field testing and where it needs to be also performed are the presence of retinal abnormalities as well as anterior visual pathway congenital disorders.
Options in visual field testing
Numerous alternatives are readily available that can be made use of to evaluate the visual fields, each with limitations. Visual field testing usually is done binocularly and monocularly. Nevertheless, the doctor stated, if a patient has a bitemporal flaw, testing must be done monocularly due to the fact that the problem might not be apparent when it is done binocularly.
Confrontation visual field testing, in which the child is shown toys and also the clinician keeps an eye on the actions, is the most fundamental test that has not changed substantially over the decades.
Using the saccadic technique, which is a confrontation test, the medical professional moves things in front of little children in order to observe the saccades; in older youngsters, counting fingers or the red objects test can be used.
Arc perimetry is an old tried and tested strategy during which babies can be evaluated by making use of a flashing light to evaluate the child’s response to the light.
Goldmann perimetry is an additional screening method in which a light moves from the periphery to the center of a hemisphere. The child signals when she or he finds the light by tapping on a buzzer; this technique functions best with cooperative patients.
The Humphrey visual field analyzer, the latest technology, is an additional choice, but its use is incredibly challenging in small children, the doctor stated.
Contribution of OCT
OCT can offer important information regarding the nerve fiber layer. He advises doctors to additionally measure the ganglion cell layer.
“The ganglion cell layer provides a great deal of detail that might not be readily available if only the nerve fiber layer is evaluated, and so there might be some loss of information” he said.
Specifically, in an individual with café au lait spots and glioma, the visual field deteriorate was progressing. OCT done in this individual showed that the glioma was advancing together with a decrease in the nerve fiber layer over time.
Keeping track of ganglion cell loss is insightful. In a kid with a suspicious visual field, in whom analyzing the nerve fiber layer may not give a good deal of information, the ganglion cell layer might shed some light on the retinal condition.
The doctor described a patient with binasal ganglion cell loss secondary to a suprasellar lesion, who was diagnosed with bitemporal hemianopsia.
In one more instance, in which a change in vision in the right eye was discovered, the bilateral vision was 20/20. The right eye showed up to have a subtle change in the visual field. Evaluation of the nerve fiber layer on OCT revealed an excellent structural look; nonetheless, a little ganglion cell loss was apparent in the left eye.
“This issue is seen frequently in individuals with demyelinating disease,” the doctor said. “The visual acuity can be totally normal, and seems to be unaffected, the colour vision may be excellent also and not show any symptoms, yet there is a reduction in the ganglion cells, visible only through an OCT.”
In a case of left homonymous hemianopsia, OCT showed an corresponding loss of ganglion cells with a lesion in the occipital lobe.
“Patients are being identified to retrograde axonal degeneration that can be determined by assessing the ganglion cell layer, again through an OCT” he stated. “In cases in which a visual field assessment cannot be executed and also in which ganglion cell loss is found, by making use of an OCT scan, doctors should be worried concerning a posterior defect.”
In a comparable instance, the patient had a superior quadrantic defect; the nerve fiber layer was normal on examination yet the ganglion cell layer was defective as well as corresponded to that defect, which would otherwise not have been noticeable without the OCT. The patient was diagnosed with post-lateral geniculate disease, finally.
In commenting on the importance of OCT, the doctor noted that the nerve fiber layer thickness ought to be affected in anterior visual pathway disorders, though not in all cases like in some cases with demyelinating disease in which the ganglion cell layer just might be affected.
“Some ganglion cell loss, visible through an OCT can be seen in retrograde axonal degeneration. OCT can be easier to execute in children and the findings can correspond to visual area defects,” the doctor explained.
Technologies on the horizon
Saccadic vector optokinetic perimetry utilizes fixation targets and an eye tracking device to monitor real-time eye movement responses to visual area stimuli. The system includes separate patient and also examiner displays, the eye tracker, which tracks visual stimuli, and a height-adjustable table, adjustable according to the height of the patient.
A head-mounted eye tracking perimeter device capable of vector analysis is under development, which would be a new technology breakthrough and should be introduced commercially in the coming times.
While numerous alternatives are readily available to evaluate the visual fields in young patients, the doctor normally begins with OCT due to the richness of information that the technology offers. Executing Humphrey visual field testing can be useful in cooperative patients. Some newer technologies on the anvil might soon add to the eye doctor’s armoury in this young and challenging patient populace.