Certified Ophthalmic Medical Technologist (COMT) Practice Exam

In the process of neutralizing +8.00 -2.00 X 90 in minus cylinder, where will the thick mires focus?

1. +4.00

2. +8.00

3. +6.00

4. -2.00

The correct answer is: +6.00

In the context of neutralizing a prescription of +8.00 -2.00 X 90, it is important to understand how cylindrical lenses work alongside spherical lenses. The prescription consists of a spherical component of +8.00 diopters and a cylindrical component of -2.00 diopters oriented at 90 degrees. To neutralize a prescription with a minus cylinder, you typically use a lens that can bring the image into focus on the retina. The cylindrical power acts to correct astigmatism and will have its maximum effect in a direction perpendicular to its axis. In this case, the minus cylinder will create a situation where light rays entering the eye are focused differently depending on their orientation. When you focus the thick mires created by the plus and minus combination, they will appear to converge or diverge based on the net power of the lens being used. In essence, to find where the thick mires would focus using this combination, one must combine the spherical and cylindrical powers effectively. In this instance, when calculating the effective power, you take the +8.00 spherical lens and combine it with the -2.00 cylindrical lens. The effective spherical equivalent here can be approximated as the sphere power plus half of the cylinder power