Step 1: Think about the two types of primary glaucoma:
Primary glaucoma comes in two forms. In the open angle form, the angle is wide but the trabecular meshwork drains poorly. In the angle closure form, the angle is narrow and the iris blocks the meshwork.
Each form has its own risk profile, so the question is a matter of putting each option under the correct form.
Step 2: Sort the options:
Positive family history: this is linked to POAG, because it is a genetically influenced disease.
Myopia: a large, long eye with a thin sclera and a weaker optic nerve head. It is linked to POAG.
MYOC gene: it codes for myocilin, a protein of the trabecular meshwork. Its mutations raise intraocular pressure and cause POAG.
Hypermetropia: a short eye with a crowded anterior segment and a thick lens relative to the eye size. This gives a shallow chamber and a narrow angle, so it is linked to angle closure glaucoma.
Step 3: Pick the exception:
Three options fit POAG, and one fits angle closure glaucoma. The odd one out is hypermetropia.
Step 4: Quick memory aid:
Open angle glaucoma: the eye is usually larger, so myopia, family history, diabetes and raised pressure go with it.
Angle closure glaucoma: the eye is smaller, so hypermetropia, shallow chamber, older age and female sex go with it.
The question asks for the exception to POAG, so the factor belonging to the closed angle group is the answer.
Final Answer:
Hypermetropia is a risk factor for angle closure glaucoma, not for POAG. The answer is option (C).