**Question:** Gonioscopy is used to study –

A. Anatomy of the angle between cornea and iris in the eye
B. Glaucoma
C. Pathology of the angle between cornea and iris in the eye
D. Refractive error of the eye

**Core Concept:** Gonioscopy is a non-invasive ophthalmic examination technique that allows visualization and assessment of the angle between the cornea and iris, specifically the trabecular meshwork and the Schlemm's canal. This examination aids in understanding the structure and function of the angle, which plays a crucial role in the filtration of aqueous humor and maintenance of intraocular pressure (IOP).

**Why the Correct Answer is Right:** Gonioscopy is primarily used to study A) Anatomy of the angle between cornea and iris in the eye. By examining the angle, ophthalmologists can assess the presence and severity of angle closure, angle recession, and other abnormalities that may contribute to elevated intraocular pressure and potentially lead to glaucoma.

**Why Each Wrong Option is Incorrect:**

A. While gonioscopy does provide information about the angle between cornea and iris, option A is too specific focusing on anatomy rather than the primary purpose of gonioscopy.

B. Glaucoma (option B) is a disease associated with elevated intraocular pressure, not the examination method itself. Gonioscopy aids in diagnosing and monitoring glaucoma but is not used to directly treat or study glaucoma.

C. Pathology (option C) is too broad and does not capture the primary objective of gonioscopy, which is to study the angle between cornea and iris for potential abnormalities leading to glaucoma, not to assess the health of the angle itself.

D. Refractive error (option D) is a misconception, as gonioscopy is unrelated to measuring refractive errors, which are related to the eye's ability to focus light. Gonioscopy is used to study the angle between cornea and iris for abnormalities leading to increased intraocular pressure and potential glaucoma.

**Clinical Pearl:** In clinical practice, gonioscopy is often combined with other diagnostic techniques, such as slit-lamp examination, to evaluate the health of the anterior chamber angle and monitor the progression of glaucoma. It aids in identifying risk factors for glaucoma development and progression, such as the presence of peripheral anterior synechiae, angle closure, or occlusion, which are associated with increased intraocular pressure and potential damage to the optic nerve.