Sen. Karen S. Montgomery (D) (Courtesy of Sen. Karen Montgomery)

Maryland Sen. Karen S. Montgomery, a longtime Democratic lawmaker from Montgomery County, plans to resign next month.

Montgomery, 80, said she made the decision recently after experiencing some trouble with her eyesight. Her resignation is effective Jan. 1.

“There is no horrible disease, no ill feelings, no scandal,” she said in a phone interview on Friday. “I was driving a few times at night and realized that I was not seeing well.”

Montgomery has served in the General Assembly since 2003, first elected to the House of Delegates. She joined the state Senate in 2010 and was reelected to a second term last year.

Senate President Thomas V. Mike Miller Jr. (D-Calvert) said Montgomery, who represents District 14, will be missed.

Her “voice as an advocate for individuals with disabilities, for mental health, education, environment, women’s issues, equality and so much more have been integral to the Senate,” Miller said in a statement. “I have been proud to call her a colleague and friend.”

Montgomery said she hopes that her colleague, Del. Craig J. Zucker (D-Montgomery), will replace her in the Senate. The county’s Democratic Central Committee will make a recommendation for a replacement to Gov. Larry Hogan (R). If Zucker is selected to fill Montgomery’s seat, the same process would take place to fill his seat.

Montgomery’s departure is the third in recent months. Two delegates were sworn in a little more than a month ago after the resignation of former delegate William A. Campos and the death of Del. James E. Proctor Jr., both of Prince George’s County.

Montgomery said she is proud of the work that the General Assembly accomplished while she was a member. She specifically mentioned legislation that prohibited smoking in public places and expanded services for the disadvantaged.

In the Senate, Montgomery served on the Education, Health and Environmental Affairs Committee. The mother of an adult autistic son, she has also worked on a commission on disabilities and a panel on special education access and equity.

“I have no regrets about the years down there,” Montgomery said. “It’s good to leave while you are not the object of everybody wishing that you would. We have seen that on the federal and state level.”