I can understand why you are concerned, Lily but drusen is really quite common and often inocuous (sp? Debka will correct me!). I think your optician is probably playing it safe by referring you for another opinion.
How old are you?
there are 2 types of ARM - wet and dry. Dry accounts of 90% of ARM, but only 10% of blind registrations due to ARM. Wet, on the other hand, accounts for 90% of blind registrations due to AMD, but only 10% of AMDs. Does that make sense? Dry is more common but less devestating to sight.
When the retina works, it metabolises and produces waste, like any other living cell. The waste can congregate under the retina and this is called drusen. It prevents good oxygen flow to the retina, and may cause further degeneration. Or it may sit there and do nothing at all.
In the older population I often see drusen and think nothing of it. If there are other changes as well (pigment changes) or distortions on the Amsler chart, for example, or a reduction in vision, it may be more serious.
Dry AMD unfortunately does not have an effective treatment yet. Recommendations are to eat a diet high in fruit and veg, esp green leafy veg like broccoli, spinach and kale. Protect your eyes from UV as this can increase the damage, and above all, don't smoke.
Wet AMD is when there is leaking of fluid or blood under the retina. This can be treated if caught early, with either a laser or injections of drugs.
If you are young (under 50ish!) then there may be another cause for the drusen other than AMD, which by its name is age-related.
I hope that helps.