RECOVERY
We next asked whether any 
recovery in physiology in a 
monkey could be obtained by 
opening the eye that had been 
closed. The answer was that 
after a week or more of eye 
closure, little or no 
physiological recovery ever 
occurred if the closed eye was 
simply opened and nothing else 
done. Even a few years later, 
the cortex was about as 
abnormal as it would have been 
at the time of reopening the 
eye, as shown in the left graph 
to the left. If at the time of 
reopening, the other, 
originally open eye was closed, 
in a procedure called eye 
reversal, recovery did occur but 
only if the reversal was done 
when the monkey was still in 
the critical period, as shown in 
the middle and right-hand 
graphs to the left for early and 
late eye reversal. After the 
critical period, even an eye 
reversal followed by several 
years with the second eye 
closed failed to bring about 
anything more than slight 
recovery in the anatomy or 
physiology.

Left: One eye was closed at birth 
for nine days in this monkey 
and then opened. The 
recordings were done four years 
later, during which time the 
animal had had much testing of 
its vision. Even that long a 
period with both eyes open 
produced little recovery in the 
physiology. Middle: The right 
eye in this macaque monkey 
was closed at birth. At five and a 
half weeks the right eyelids 
were opened and the left closed. 
When at six months the 
recording was made from the 
right hemisphere, most of the 
cells strongly favored the right, 
originally closed eye. Right: In 
this macaque monkey the right 
eye was closed at seven days, 
for one year, at which time the 
right eye was opened and the 
left was closed. After another 
year, the left eye was opened, 
and both remained open. When 
finally the recording was made 
at three and a half years, most 
cells favored the eye that was 
originally open. Evidently one 
year is too late to do a reverse 
suture.

    The monkey's ability to see 
did not necessarily closely 
parallel the cortical physiology. 
Without reversal, the originally 
closed eye never recovered its 
sight. With reversal, sight did 
return and often approached 
normal levels, but this was so 
even in late reversals, in 
which the physiology remained 
very abnormal in the originally 
closed eye. We still do not 
understand this disparity 
between the lack of substantial 
physiological or anatomical 
recovery and what in some 
cases seemed to be considerable 
restoration of vision. Perhaps 
the two sets of tests are 
measuring different things. We 
tested the acuity of vision by 
measuring the ability to 
discriminate such things as the 
smallest detectable gap in a line 
or circle. But testing this type 
of acuity may yield an 
incomplete measure of visual 
function. It seems hard to 
believe that such florid 
physiological and anatomical 
deficits in function and 
structure would be reflected 
behaviorally by nothing more 
than the minor fall in acuity 
we measured.