## **Core Concept**
The question revolves around the diagnosis of a condition affecting a 16-year-old boy with eye pain, for which he was prescribed a +3.5 D sphere lens after refractometry. The key concepts here involve understanding refractive errors, the prescription of corrective lenses, and interpreting the results of ocular motility tests like the cover test.

## **Why the Correct Answer is Right**
The prescription of a +3.5 D sphere lens indicates that the boy is **hyperopic** (farsighted) and requires a convex lens to converge light properly on the retina. Hyperopia occurs when the eyeball is too short or the cornea is too flat, causing light to focus behind the retina. A +3.5 D lens corrects this by adding refractive power. The normal cover test and absence of heterophoria suggest that there is no strabismus (misalignment of the eyes) or latent deviation of the eyes when one eye is covered.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Myopia (nearsightedness) would require a concave (minus) lens for correction, not a convex (plus) lens.
- **Option B:** Astigmatism involves an irregular curvature of the cornea or lens inside the eye, requiring a cylindrical lens for correction, not just a spherical lens.
- **Option C:** Presbyopia is a condition associated with aging, typically starting in the early to mid-40s, where the eye's lens loses its flexibility, making it difficult to focus on close objects. A 16-year-old would not be diagnosed with presbyopia.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that hyperopia (hypermetropia) in children can often be compensated for by the eye's natural accommodation, but as they grow, the condition may become more apparent. Early detection and correction can prevent complications like amblyopia (lazy eye).

## **Correct Answer:** D. Hypermetropia.