Certified Paraoptometric (CPO) Practice Exam 2025

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What is the main function of a lensometer?

  1. To check visual acuity

  2. To verify the spectacle and contact lens prescription

  3. To determine lens material

  4. To create custom lenses

The correct answer is: To verify the spectacle and contact lens prescription

The main function of a lensometer is to verify the spectacle and contact lens prescription. This instrument measures the power of lenses to ensure they match the prescribed specifications provided by an eye care professional. It does this by determining the lenses' diopter power, which is crucial for ensuring that corrective lenses accurately address a patient's vision needs. While checking visual acuity is essential in vision care, it is not a function of a lensometer; that task is performed by other devices like a phoropter or vision chart. Additionally, determining lens material and creating custom lenses involve different processes and tools, as these tasks are related to lens fabrication and material science rather than prescription verification.