Jordan John Lawrie was not taking medication at the time

Jordan John Lawrie, 19, pleaded guilty to wounding Troy Reynolds on March 18 last year and to assaulting him by punching him to the head eight to 10 times.

Crown prosecutor Emily Judd said the two men were not known to each other and that Reynolds had been transferred to a new unit the night before.

She said the complainant was on the bed about 12.10pm when Lawrie, then 18, entered and then exited the communal bathroom holding a small instrument.

"The accused approached the complainant and hit him to the left eye with the instrument causing a sharp piercing pain," Ms Judd said.

"He attempted to defend himself but then the accused stabbed him in the eye a second time causing a laceration to the eyelid.

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Lawrie dropped the instrument and punched him to the face eight to 10 times causing his mouth to bleed and then left the cell and shut the door.

He went to the communal bathroom where correctional officers searched and found the weapon located in a shoe.

"It was a modified pen with a rusty nail commonly known as a shiv," Ms Judd said.

She said the victim was taken to the Royal Hobart Hospital where he required four stitches to the lower left eyelid and superficial injury to the cornea.

There was no long-term effect to his vision.

Ms Judd told Acting Justice Shane Marshall that Lawrie had prior offending as a youth.

She said it was an aggravating feature of the crime that it was a similar crime only a year.

"This was unprovoked when the victim was lying on his bed and he stabbed him to the eye with a makeshift weapon," he said.

Defence counsel Hannah Phillips said Lawrie had spent 81 days in custody although he was also remanded in custody in March for an alleged robbery to which he had pleaded not guilty.

She said Lawrie had a troubled background which included being punched and kicked to the head and run down by his father on a motorbike.

Ms Phillips said the incident occurred at a time when Lawrie was being stood over in Risdon Prison by prisoners wanting his schizophrenia medication.

She said he had not taken medication on four dates in January and February.

"The prison was advised in January 2020 that he was experiencing hallucinations but it was not until March 23, after this crime, that a review was conducted," Ms Phillips said.

Acting Justice Marshall adjourned sentencing until June 3 at 4pm.