Fame
Quick, name a famous optometrist.
Exactly.*
Now name your favorite place to go to get your eyes checked and get new glasses. That's the kind of fame you want as an optometrist. You'll know you're famous when you get good reviews online, you have great word-of-mouth business, and people book in advance. You get there by having a great reputation.
What do your clients love? The latest equipment and dependable service. Are you located close to shops and restaurants with good parking? Do you truly care about your patients and have you established a good rapport with each? That's the kind of fame you want. Extra bonus points for having fresh breath.
*Okay, Robert Morrison is famous for catering to the famous and developing soft contacts. But you get the point.