Laboratory of Clinical Psychophysics and Electrophysiology

Back to Kenneth R. Alexander, PhD

Research Projects

I have had a long-standing interest in identifying the mechanisms of vision loss in persons with various forms of hereditary and acquired retinal degenerations. A primary emphasis of the research in my laboratory has been to establish the relationship between visual dysfunction and the underlying retinal disease process.

This relationship is investigated through the use of psychophysical, electrophysiological, and other noninvasive test procedures, in combination with information from other disciplines, including molecular genetics and immunocytochemistry.

The overall goals are to advance our understanding of the causes of vision loss in retinal diseases, and to provide insights into the optimal methods for minimizing their impact on the quality of life of persons with ocular disorders.

Examples of recent research studies are given below.

Retinal Dysfunction in Retinitis Pigmentosa

Much of my research has focused on the nature and extent of vision loss in a sight-threatening form of retinal degeneration called retinitis pigmentosa (RP). I have been especially interested in defining the relationship between patients' vision loss within the fovea and the underlying disease process.

To that end, I have examined a number of characteristics of patients' foveal vision loss, including various forms of visual acuity deficits, contrast sensitivity loss, and abnormalities in motion perception, all in the context of models of retinal dysfunction.

Current work is directed toward investigating the characteristics of contrast processing within the magnocellular and parvocellular pathways in RP.

Stimuli used to evaluate the contrast sensitivity of the magnocellular and parvocellular pathways in persons with RP (From Alexander et al., Investigative Ophthalmology and Visual Science, vol. 45, no. 12, 2004.)

ON-Pathway Deficits in Retinal Diseases

I have also been interested in clarifying the disease mechanisms that underlie a number of other retinal disorders. Recently, a primary emphasis has been on electrophysiological and psychophysical studies of dysfunction of the retinal ON-pathway that can occur in certain hereditary and acquired retinal disorders, such as melanoma-associated retinopathy and X-linked retinoschisis.

In these disorders, there are abnormalities in the ON response of the electroretinogram (ERG) that indicate preferential dysfunction of the depolarizing (ON) bipolar cells of the retinal cone system.

Illustration of the abnormal ON response of the ERG that is characteristic of melanoma-associated retinopathy. The b-wave (left) is markedly reduced, but the d-wave (right) is normal. (From Alexander et al., Investigative Ophthalmology and Visual Science, vol. 43, no. 4, 2002.)

Research funding

National Eye Institute
Research to Prevent Blindness, Inc.
Foundation Fighting Blindness

Laboratory Personnel

J. Jason McAnany, MS, Graduate Student
Aparna Raghuram, PhD, Postdoctoral Fellow