Certified Ophthalmic Medical Technologist (COMT) Practice Exam

For an accurate IOP measurement using a Goldmann tonometer, the tonometer tip must be set at 43 degrees from the minus cylinder axis if corneal astigmatism is __________.

1. 1 diopter or more

2. 2 diopters or more

3. 3 diopters or more

4. 4 diopters or more

The correct answer is: 3 diopters or more

For accurate intraocular pressure (IOP) measurements with a Goldmann tonometer, understanding the relationship between corneal astigmatism and the alignment of the tonometer tip is crucial. When corneal astigmatism is present, the tonometer tip must be oriented appropriately to account for the astigmatism's impact on pressure readings. Setting the tonometer tip at 43 degrees from the minus cylinder axis is necessary when the level of corneal astigmatism reaches a diopter value that significantly alters the corneal curvature and consequently affects the pressure measurement. In the context of this question, the requirement to set the tonometer tip at 43 degrees specifically applies to situations where corneal astigmatism is 3 diopters or more. This level of astigmatism is where the differences in curvature between the cornea's steep and flat meridians become pronounced enough to influence the accuracy of the IOP reading. Therefore, adjusting the tonometer tip allows for compensation of this astigmatism, ensuring that the IOP measurement reflects the true intraocular pressure rather than being skewed by the unequal curvatures of the cornea. If the astigmatism were less than 3 diopters, a