**Question:** A patient has a complaint of seeing coloured halos around lights at night and blurred vision for the last few days along with normal intraocular pressure (IOP).

**Core Concept:** Ocular symptoms and normal IOP does not always exclude glaucoma.

**Why the Correct Answer is Right:** The patient is presenting with symptoms of glaucoma, specifically the visual field defect known as "coloured halos around lights at night" (also known as "phosphenes") and blurred vision. These symptoms are due to the increased intraocular pressure (IOP) causing damage to the optic nerve and its axons, which transmit visual information from the retina to the brain. Although the patient mentions normal intraocular pressure (IOP), glaucoma can present with a wide range of IOP values, and normal IOP does not exclude the diagnosis. Moreover, the patient's symptoms are suggestive of open-angle glaucoma, which can present with normal IOP as well.

**Why Each Wrong Option is Incorrect:**

A. **Hypotony (low IOP):** This option is incorrect because hypotony is characterized by abnormally low IOP below 6 mmHg, and the patient's IOP is normal.

B. **Hyphema:** Hyphema refers to blood in the anterior chamber due to a traumatic or spontaneous event. The patient's symptoms and normal IOP are not consistent with this condition.

C. **Chalazion:** Chalazion is a non-infectious meibomian gland obstruction, causing a localized inflammation of the eyelid margin. The patient's symptoms and normal IOP are not consistent with this condition.

D. **Chorioretinal folds (Cogan-Reese syndrome):** This condition is characterized by chorioretinal folds due to altered elasticity of the sclera, which is unrelated to the patient's symptoms and normal IOP.

**Clinical Pearl:** Glaucoma can present with normal IOP and should be suspected in patients with ocular symptoms, even if IOP is within the normal range. A thorough clinical examination is crucial to identify other risk factors and signs of glaucoma, such as normal-tension glaucoma, disc hemorrhages, or nerve fiber layer defects.

**Correct Answer:** **D:** Normal-tension glaucoma (NTG) is a form of glaucoma where intraocular pressure remains within the normal range despite the presence of optic nerve damage and visual field defects. NTG is often associated with a reduced optic nerve blood flow and anterior chamber depth, which can be seen in the slit-lamp examination. In this case, the correct answer is D (normal-tension glaucoma) because the patient exhibits symptoms of glaucoma (coloured halos around lights) and normal intraocular pressure, which is characteristic of normal-tension glaucoma.