Everything is open.
Simply read a little each night - use the conditions you saw in clinic during the day as things to read about. Also talk to your co-residents - each of you will see different things on call - see how they handled the patients. It is amazing how much ophthalmology residents learn in a matter of months with such a technique. With programs providing high patient volumes and high pathology levels, one almost has to try not to learn quickly.
There are several obvious conditions to know well when in clinics examining mostly adult (understant pathogenesis, indications for treatment, treatments, and how to talk to patients about them).
1. Cataract - types, indications for surgery
2. Diabetic Retinopathy - PDR, macular edema, when to treat, how to treat.
3. AMD
4. Blepharitis
5. Severe cornea ulcer - can be intimidating to see yourself on call - but treatment is pretty straightforward.
6. Glacuoma. Open vs closed. Know all drops and side effects. Know surgeries
7. Understanding indications and how to interpret all testing modalities (OCT, FA, visual fields).