I don't think that an 8 year old uro should be considered
old. At this age they are most likely approaching the middle
life part of their life span. Ofcourse proper husbandry plays
a large part in long lived uros as it does in most reptiles.
The failing eyesight you mentioned could be a health, DNA
or genetic issue. Maybe just due simple by the lack of
certain proteins/vitamins in their daily diet like beta carotene
to mention one.
Some herpetologists might challenged the constant exposure
of artificial lighting when captive housed through their entire
lives with often few hides for them to seek non lit areas of
their terrariums. I don't believe that these uros will bask for a
10 or 12 hour period while in the wild. They may bask in
order to warm up for a morning hunt for their favorite plant
life and often this is interrupted by clouds or even by various
predators seeking a scaly morsel.
I've attached a photo of one of my oldest uros "Tony"
(the tiger). He is a great looking 16 year old tiger stripped
mali which I purchased back in the mid 90s as a young
adult. I first housed him indoors for a couple of years.
He's been outdoors for the past 10 years (at least) and is
in better than decent health ... considering his age. I'm a
great believer in natural sunlight for my reptiles and do
house most of my collection/breeders outdoors with
great success. Many of my uros are entering their silver
years and some (as Tony) their golden years with little
to no issues to speak of.
Just my two cents worth,
John
