Objective methods for checking the refractive error are all except
**Core Concept**
Refractive errors occur when the shape of the eye does not bend light correctly, resulting in blurry vision. Objective methods for checking refractive error involve measuring the eye's ability to focus light without relying on patient feedback.
**Why the Correct Answer is Right**
The correct answer is **C. Autorefraction with Placido Disk**, which is an objective method for measuring refractive error. This method uses a Placido disk to create a series of rings on the cornea, and a camera captures the image. The image is then analyzed to calculate the refractive error.
**Why Each Wrong Option is Incorrect**
**Option A:** Autorefraction is an objective method, but it is not the same as autorefraction with Placido disk, which is a specific type of autorefraction.
**Option B:** Autorefraction is an objective method, but it is not the same as retinoscopy, which is also an objective method.
**Option D:** Retinoscopy is an objective method, but it is not the same as autorefraction with Placido disk.
**Clinical Pearl / High-Yield Fact**
Retinoscopy and autorefraction are both objective methods for checking refractive error, but they work in different ways: retinoscopy measures the movement of the retina, while autorefraction measures the shape of the cornea.
**Correct Answer:** C. Autorefraction with Placido Disk