We used a perceptual closure task with Mooney images as stimuli to record eye-movement patterns in response to the same degraded image before and after perceptual learning in 21 adolescents and young adults with ASD and 23 sex-, age-, and IQ-matched typically developing individuals. In the control group, we observed changes in the eye-movement patterns between the first and the last presentation of the degraded stimulus, reflecting top-down optimization of eye-movement patterns, that is, a decrease in the number of fixations and interfixation distance, coupled with an increase in the duration of fixations. This effect was attenuated in individuals with autism, pointing to a decreased rate of perceptual learning. We also found that participants with autism displayed decreased scanpath stability, that is, a lower recurrence of fixation locations between different presentations of the same image, which may suggests a lower rate of perceptual learning or decreased predictability in the eye-movement patterns. These results provide evidence for decreased use of prior knowledge in perceptual decisions in autism. Autism Res 2019, 12: 1386-1398. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: We showed autistic and typically developing participants some degraded images that were difficult to recognize for the first time, but once you knew what they represent, you could see it easily. We found that the eye-movement patterns of persons with autism did not change as much after learning what the pictures represented as in the case of typically developing participants. This means that previous experiences and knowledge change the way people with autism perceive things to a smaller extent.