Scientists say they have used the gene-editing tool CRISPR to repair a person's eyesight for the first time.DNA is short for deoxyribonucleic acid.It is the substance that carries genetic information in the cells of living things.The CRISPR tool makes it possible to change DNA to add needed genes or take some away if they lead to problems.A patient recently had the procedure done for an inherited form of blindness,the companies that make the treatment announced Wednesday.The operation took place at Oregon Health and Science University in Portland.The companies did not release additional details about the patient.It may take up to a month to see if the procedure worked to repair a patient's vision.If the first few attempts seem safe, doctors plan to test it on 18 children and adults."We literally have the potential to take people who are essentially blind and make them see," said Charles Albright.He is chief scientific officer at Editas Medicine in Cambridge, Massachusetts.Editas is one of the companies developing the treatment.The other is Allergan, based in Dublin, Ireland.Albright added, "We think it could open up a whole new set of medicines to go in and change your DNA."Dr. Jason Comander is an eye doctor at Massachusetts Eye and Ear in Boston.He said it marks "a new era in medicine" in which technology has made "editing DNA much easier and much more effective."Doctors first tried in-the-body gene editing in 2017 for a different inherited disease using a tool called zinc fingers.Many scientists believe CRISPR is a much easier tool for finding and cutting DNA at an exact spot.The people taking part in the study have a genetic condition that keeps the body from making a protein neededto turn light into signals to the brain, which leads to sight.People with the disease are often born with little ability to see.They can lose whatever vision they are born with when they are still very young.Scientists have found it difficult to treat the condition with usual gene therapy.So, they are aiming to edit or remove the mutation by making two cuts on either side of it.The hope is that the ends of DNA will reconnect and make the gene work as it should.The procedure is done in an hour-long operation.Through a tube the width of a human hair,doctors put three drops of fluid containing the gene editing machinery just under the retina.That is the lining at the back of the eye that contains the light-sensing cells.Doctors believe they need to fix one-tenth to one-third of the cells to repair vision.In animal tests, scientists were able to correct half of the cells with the treatment, Albright said.Some independent experts were hopeful about the new study.Dr. Kiran Musunuru is a gene-editing expert at the University of Pennsylvania.He said the treatment seems likely to work, based on tests in human tissue, mice and monkeys.The gene editing tool stays in the eye and does not travel to other parts of the body.So, "if something goes wrong, the chance of harm is very small," Musunuru said."It makes for a good first step for doing gene editing in the body."