Current Interests:

VEP EVALUATION OF CONE FUNCTION IN CHILDREN WITH CONE DYSFUNCTION SYNDROMES.

We are currently using the Visual Evoked Potential (VEP), full field electroretinography, and multi-focal electroretinography for assessment of cone photoreceptor function in the central visual field of pediatric patients. We have found the VEP to be a very useful alternative to electroretinography and other standard clinical testing in children, who would not otherwise tolerate testing. The Full-field Electroretinogram (ERG) serves as a standard method of objective assessment of retinal rod and cone function.

We have found several advantages to the VEP over ERG testing:

  1. The ERG is a costly and time-consuming procedure in the pediatric clinic. Often we must sedate the patient in order to tolerate contact lens electrodes. The VEP takes about ½ hour and does not need sedation/anesthesia.
  2. Children tolerate the VEP much better than the ERG.
  3. The ERG is prone to noise from nystagmus, whereas the VEP is still robust if horizontal grating stimuli are presented.
  4. While the ERG is sensitive to gross rod dysfunction, the ERG may not detect dysfunction of cone receptors in the macula or fovea.
  5. Assessment of individual cone types (L, M, S or red, green, blue) is easily performed with the VEP. Control children generate very robust VEPs to these stimuli. Therefore color vision screening is objectively assessed without requiring any cognitive skills (such as sorting with the FM-100, isochromatic plates, etc.).

Links:
RetNet -- a summary of genes that cause retinal diseases

OBJECTIVE ASSESSMENT OF VISION IN CHILDREN WHO ARE VISUALLY INATTENTIVE ON A CORTICAL BASIS.

We also use the Visual Evoked Potential (VEP) in addition to Magnetic Resonance Imaging and CT scans for assessment of pediatric patients, who appear to be blind but have a normal eye exam. We have applied the T2circ analysis of the transient VEP in these children to determine whether a statistically significant visual response is present (for information on the T2circ, see Victor JD, Mast J. A new statistic for steady-state evoked potentials. Electroencepholography and Clinical Neurophysiology, 1991;78:378-388.). Often we find that this statistical analysis is the only way to determine if a child can see. In some cases, the visual disorder may be attributed to "delayed visual maturation" while other cases may result from "cortical visual impairment."

Links:
The Center for Children with Special Needs <http://www.cshcn.org/>

 

PREDICTION OF VISUAL ACUITY  DEVELOPMENT IN CHILDREN WITH BILATERAL OPTIC NERVE HYPOPLASIA.

This disorder can severely affect vision in newborn children. The disorder causes abnormally low numbers of retinal ganglion cells resulting in reduced vision, variable brain malformations, and possibly abnormal endocrine system function. There is no cure for the disease so the child will experience reduced vision for the rest of his or her life. There is wide variation in how much vision the child will have from the disease. Our research has shown that the expected outcome in visual acuity depends upon the size of the optic nerve and the initial visual acuity assessment after six months age. The analysis of visual evoked potentials can also lead to the distinction between children who will have better than 20/200 vision.

 

OPTIMIZATION STUDIES FOR APPLICATIONS OF A SCANNED LIGHT DISPLAY.

This work is currently being done at the Human Interface Technology Laboratory at the University of Washington. The lab uses a high speed mechanical resonant scanner to generate a raster-based display on the retina with lasers. The display is called the Virtual Retinal Display or VRD. This work investigates how the VRD display characteristics can be optimized as a display device, and the effects of laser light on visual function. We have collected information on the temporal characteristics of scanning a laser light across the retina and its potential effect of zero image persistence, hyper-acuity, and contrast sensitivity. Currently we are examining how observer’s accommodation can vary with a monochromatic monocular display that uses a very small exit pupil. Under these conditions, the observer has few cues that provide feedback about the accuracy of accommodation.

I am also collaborating with Conor Kleweno and Eric Seibel on applications of the VRD to observers with low vision. For more details see : http://www.hitl.washington.edu/research/lowvision/. 

HAND-HELD LASER OPHTHALMOSCOPE FOR OCULAR IMAGING AND VISION ASSESSMENT.

This work was being performed in collaboration with Laser Diagnostics Technology Inc. The purpose was to bring the confocal scanning laser ophthalmoscope to the pediatric practice. We are also interested in examining the accommodative response to a confocal scanning laser ophthalmoscope.

Probing brain mechanisms with Visual Evoked Potentials in children with anisometropic amblyopia.

Using the transient VEP we have isolated unique components that respond to successful patching.

 

Using Visual Evoked Potentials to quantitate visual loss and progression of visual field loss in children with tumors of the optic pathways.