James Buchanan struck the shopping trolley pulled by David McQuiston, knocking him to the ground.
Mr McQuiston was returning home from visiting his dementia-stricken wife at the time of the accident in January 2015.
The pensioner died two months later after never fully recovering from the collision in Dunoon, Argyll and Bute.
Buchanan – a taxi driver for 18 years – could now face jail after he yesterday pled guilty to a charge of causing death by careless driving.
His bail was continued at the High Court in Glasgow pending sentencing next month.
Mr McQuiston had gone to see his wife of 51 years, who lived with their daughter in Dunoon.
The accident happened in the town’s Argyll Road around 3pm on 3 January 2015.
Prosecutor Tim Niven Smith said “the sun was low in the sky” with its brightness “reducing visibility”.
Mr McQuiston was not walking on the pavement and was instead following the double yellow lines at the side of the road.
The pensioner, who lived in the town, was using a stick to help him and he was also pulling a dark shopping trolley. The court heard the pavement was icy possibly explaining why the pensioner was on the road.
Mr Niven Smith said Buchanan failed to spot Mr McQuiston at the kerbside with his car hitting the trolley.
The pensioner fell and smacked his head on the ground.
Buchanan immediately got out of his Seat Toledo and dialled 999.
He told one witness: “I could not see him. I did not mean it. It was the glare of the sun.”
A retired nurse meantime went to help Mr McQuiston. Buchanan repeated: “I did not see him. The sun was in my eyes.”
He then went on to comment that another passing driver was being “blinded” by the sunlight.
Mr McQuiston was transferred by helicopter to intensive care in Glasgow amid fears he had a brain injury.
Following rehabilitation, he was sent to the Erskine care home in Renfrewshire. But, on 20 March 2015, Mr McQuiston died there after falling unconscious due to breathing problems. It was found that he passed away due to a form of pneumonia caused by the head injury.
Tony Graham, defending, said Buchanan offered his “deepest apologies” to Mr McQuiston’s relatives.