**Question:** Intraocular tension is decreased by all except

A. Glucose
B. Insulin
C. Carbon dioxide (CO2)
D. Oxygen

**Core Concept:**
Intraocular tension refers to the pressure within the eye, which plays a crucial role in maintaining the eye's structure and function. The eye's structure, including the lens and cornea, relies on this pressure to remain flexible and maintain optimal vision. Intraocular tension is primarily regulated by the balance between aqueous humor production and absorption within the eye.

**Why the Correct Answer is Right:**
In this question, we are looking for substances/factors that do not decrease intraocular tension. The correct answer is **D.** Oxygen (O2) does not directly affect intraocular tension as its primary role is in cellular respiration and maintaining tissue oxygenation, which is unrelated to intraocular pressure regulation.

**Why Each Wrong Option is Incorrect:**
A. Glucose (A): Although glucose is essential for cellular energy production, there is no direct link between glucose levels and intraocular tension.
B. Insulin: Insulin is involved in regulating blood glucose levels but does not play a direct role in intraocular tension control.
C. Carbon dioxide (CO2): Elevated CO2 levels can cause vasodilation, which could potentially impact systemic blood flow to the eye, but CO2 itself does not directly influence intraocular tension.

**Clinical Pearl:**
It is essential for students to understand the specific roles of various substances and factors in maintaining ocular health and function. This knowledge is crucial in clinical practice to differentiate between conditions with elevated or decreased intraocular tension and appropriate management strategies.