Authorities say a Washington mother repeatedly put bleach into her toddler daughter's eyes, causing permanent vision loss in child's right eye, Q13 Fox reports.

29-year-old Jennifer Mothershead pled not guilty to charges of first-degree child assault Monday.

Authorities say Mothershead was given antibiotics and eye drops in March 2011 for her toddler daughter after the child came to a local hospital with an eye issue. Mothershead told doctors her daughter had scratched her eye while playing in a barn, according to Q13 Fox.

Authorities claim Mothershead's then-14-month-old daughter was airlifted to the hospital with a serious head injury in May 2011. Authorities grew concerned when Mothershead reportedly had no explanation for what had happened.

While examining the girl, doctors noticed the child's eye infection had gotten worse. Mothershead told doctors her child's eyes had been swollen shut for a month, according to Q13 Fox.

She said her daughter was sleeping 20-22 hours a day because she could not tolerate exposure to sunlight due to her eye pain. 

Pierce County Sheriff's Department spokesman Ed Troyer told Q13 Fox investigators decided to look into the case in part because they felt Mothershead showed little concern for her child. When they examined the eye drops Mothershead allegedly had given to her daughter, one detective said the drops caused a burning sensation when he tested them on his wrist.

"We found one of the eye drop bottles of chemicals, which basically burned our detectives," Pierce County Sheriff's Department spokesman Ed Troyer told Q13 Fox.  "It obviously wasn't something that should be going in someone's eyes."

Investigators sent the drops to the Food and Drug Administration's Forensic Chemistry Lab for analysis. The lab determined the drops contained bleach.

"The staff at Harborview determined that the damage to the child's eyes was consistent with repeated exposure to bleach, and ruled out any possibility that the eye dropper had been merely cleaned with bleach," the prosecutor's office said in a statement according to The Associated Press.

The child, now 2, lives with her father. Her eye condition reportedly improved with treatment but doctors say she suffers from permanent vision loss in her right eye.

Click here for more on this story from Q13 Fox.

The Associated Press contributed to this report.