McKinley, now 27, was on Leinster's books when he suffered the serious injury after sustaining an accidental boot to his eye.
The Dubliner was forced to retire but made a playing return in Italy thanks to special protective goggles.
McKinley has played 21 Treviso games in this season's Pro12 and Challenge Cup.
His form has led Italy coach, former Ireland international Conor O'Shea, to name the fly-half in a 44-man squad for the Tests against Scotland, Fiji and Australia.
Ireland Under-20 international McKinley now qualifies for the Azzurri under the residency rule.
In a tweet on Wednesday, McKinley said that he been "overwhelmed by the reaction" to his inclusion in Italy's squad.
After his playing career had apparently ended, McKinley began a coaching stint in the Italian town of Udine before returning to action in his adopted-country's domestic league for Leonorso Udine and Viadana.
That led to him being awarded a contract with Pro12 club Zebre in 2015/16 before he moved to Treviso last summer.
McKinley, who sustained the initial eye injury during a match for University College Dublin in 2010, kicked 11 points in Treviso's 21-6 win over Edinburgh last month.
Following initial surgery in 2010, McKinley's left eye regained 70% vision and he went on to make a try-scoring Leinster debut in 2011 before complications led to him losing sight in the eye.
For a time, Irish Rugby's rules prevented him from representing Zebre in his native country but a change of regulations last season opened the door to him playing Pro12 games in Ireland.
Italy will face Scotland in Singapore on 10 June before facing Fiji on 17 June before taking on Australia in Brisbane a week later.
The Azzurri lost all their five games in this year's Six Nations, which was rounded off by a 29-0 defeat by the Scots.
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Irish-born Ian McKinley has been called into Italy's squad for their summer Tests six years after losing his sight in his left eye.