The Blurredy Thing!

A Doctor writes:

Sooner or later, genealogists will encounter the medical condition which we doctors have come to know as Microfilm Blur (mī'krə-fĭlm' blûr).
The condition is often transient, but is noted for its severity on those occasions when it does manifest itself.
Typically, the subject will have spent a minimum of 3 hours in a County Records Office. In some cases (and this has been reported from patients in the North Yorkshire area, in particular), the surroundings in which they find themselves will be so cold as to lead to the onset of shivering and a hacking cough. Combined with microfilm blur, such a condition can only be treated by complete bedrest. On no account must the patient be allowed to look at grainy images of parish records - even if these are high-quality photocopies, taken with a view to looking at them later.
Thankfully, symptoms have been shown to ease after a short period. Alcohol may help.