It has often been said that major depression is a condition of extremes, leaving the depressed person thinking only in terms of worst case scenarios, blaming himself for whatever goes wrong in his life, refusing to allow himself to experience pleasure and refusing to give himself credit for any positive accomplishment. Non-depressed people moderate their vision of themselves and the world around them. They see the world as good and the bad. They can experience pleasure as well as pain. They sometimes blame themselves and sometimes blame others. They alternate between hope and fear. In a figurative sense depressed people are unable to see shades of gray while non-depressed people can.
We have just learned that depressed people are literally much less able than non-depressed people to see shades of gray. In the July 15, 2010, issue of Biological Psychiatry, a group of researchers led by Emanuel Bubl of the Albert-Ludwigs-University of Freiburg published their study on the use of pattern electroretinogram assessment (PERG) on the eyes of depressed and non-depressed people. An electroretinogram is a machine which measures how the retina responds to visual contrast. Dr. Bubl wanted to find out if depressed patients had reduced sensitivity to contrast perception.
His group recruited and studied forty patients with a diagnosis of major depression (20 with and 20 without medication) and 40 matched healthy subjects. They recorded visual PERGs from both eyes of all study participants. Unmedicated and medicated depressed patients displayed dramatically lower retinal contrast perception, meaning they were much less able to detect shades of gray. The researchers found a strong and significant correlation between contrast perception and severity of depression. Computerized analysis revealed a specificity of 92.5% and a sensitivity of 77.5% for classifying the participants correctly. Because PERG recordings do not depend on subjective ratings by an optometrist, this decrement in the ability of a person’s retina to detect shades of gray is a marker or objective correlate of major depression which can be used for diagnostic purposes.
At this point we do not know why the retinas of people with major depression are so much less able to appreciate visual contrast between the shades of gray that lie between pure black and white. Perhaps neuro-ophthalmologists and neuro-psychiatrists will be able to answer this question in the future. Meanwhile it is a very intriguing piece of data which joins together our visual-psychological metaphor and our medical-ophthalmological understanding of depressed people as being unable to appreciate shades of gray.
