Whilst doing a well-baby clinic you see Charlie, who is eight-weeks old. He is brought to you by his mother, Sarah. She informs you that her pregnancy went well and she had a water-birth at home. Since birth, Charlie has been well, he is exclusively breast-fed and is gaining weight along the 50th centile. On examination, Charlie is easily arousable, he has good tone, his head circumference is normal and cardiovascular, respiratory and abdominal examinations are unremarkable. Barlow’s and Ortolani’s tests are negative. The red reflex is present in the right eye but is difficult to view in the left. On closer inspection, you note that the left pupil is grey in colour. Sarah thinks his eye has always looked like that and is not worried about it.
What is the most appropriate next step?