my close vision seems excessively sharp after close work on the computer so what is going on?

Issue
it seems more than can be accounted for by a drop in blood sugar in the lens

Best Tip

Working closely on the computer refines your near accommodation. Your eyes adapt to your viewing conditions. It will wear off after staring out the window for a while. Then your eyes will adapt to the far condition.

As you get older, it takes longer for the transitions to occur because your crystalline lens loses elasticity due to hydration loss and fiber compaction from a continuous fibril cell layer being deposited onto the lens cortex from the epithelial layer. This is for the normal person. Diabetics can sometimes have, in addition to hydration loss in some areas, excessive hydration in other areas in the form of water pools, or lakes, within the lens. Irregularities in the lens refractive index, such as these, are cataractous. Cataract leads to visual impairment or blindness.

Diabetes can also cause visual performance effects from dynamic glucose concentration changes in the aqueous humor. However, this is more an intraocular scattering issue rather than a refractive error change. On the other hand, intraocular pressure differentials related to diabetes can cause changes in refractive state, or temporary blurred vision.

Others
It could be that due to the diabetes your eye accomodation (the way the eye adjusts to long and short vision) has changed. I don't think that this would be anything to worry about, (I would be worried if the vision had deterioated!) but it wouldn't hurt to see an optician to get it checked out professionally.
Im diabetic!