From MedlinePlus Genetics
Fuchs endothelial dystrophy is a condition that causes vision problems. The first symptom of this condition is typically blurred vision in the morning that usually clears during the day. Over time, affected individuals lose the ability to see details (visual acuity). People with Fuchs endothelial dystrophy also become sensitive to bright lights.

Fuchs endothelial dystrophy specifically affects the front surface of the eye called the cornea. Deposits called guttae, which are detectable during an eye exam, form in the middle of the cornea and eventually spread throughout the cornea. These guttae contribute to the ongoing cell death within the cornea, leading to worsening vision problems. Tiny blisters may develop on the cornea, which can burst and cause eye pain.

The signs and symptoms of Fuchs endothelial dystrophy usually begin in a person's forties or fifties. A very rare early-onset variant of this condition starts to affect vision in a person's twenties.  https://medlineplus.gov/genetics/condition/fuchs-endothelial-dystrophy