**Core Concept**
HLA (Human Leukocyte Antigen) testing is used to identify specific genetic markers associated with various autoimmune and inflammatory conditions. In the context of ocular affections, HLA testing is employed to diagnose conditions where there is a strong genetic predisposition.

**Why the Correct Answer is Right**
The correct answer involves Fuchs' endothelial corneal dystrophy (FECD), an autosomal dominant inherited condition characterized by corneal endothelial cell dysfunction. HLA class II antigens, particularly HLA-DR and HLA-DQ, have been strongly associated with FECD. The genetic predisposition linked to these HLA markers is crucial in the diagnosis of FECD, with many studies indicating that individuals with certain HLA haplotypes have an increased risk of developing the condition.

**Why Each Wrong Option is Incorrect**
* **Option A:** Fuchs' endothelial corneal dystrophy is not associated with HLA-B27, which is a specific HLA class I antigen primarily linked to ankylosing spondylitis and other spondyloarthropathies.
* **Option B:** HLA testing is not used to diagnose age-related macular degeneration (AMD), a condition primarily linked to environmental and lifestyle factors rather than genetic predisposition.
* **Option C:** HLA-B8 is associated with several autoimmune conditions, but it is not specifically linked to FECD. HLA-B8 is more commonly associated with conditions like autoimmune hepatitis and primary biliary cirrhosis.

**Clinical Pearl / High-Yield Fact**
Be aware that FECD has a strong genetic predisposition, and HLA testing can aid in the diagnosis of individuals with a family history of the condition.

**Correct Answer:** D. Fuchs' endothelial corneal dystrophy