What will be the prescription for spectacles in a patient having simple myopic with the rule astigmatism?
**Core Concept**
Simple myopic with the rule astigmatism is a type of refractive error characterized by a combination of myopia and regular astigmatism, where the refractive error is aligned with the rule (i.e., the meridians of equal power are at 90 degrees and 180 degrees). This type of astigmatism is typically associated with a cylindrical correction of 1.5 to 2.5 diopters.
**Why the Correct Answer is Right**
In simple myopic with the rule astigmatism, the near point of the patient is behind the nodal point, resulting in a longer focal length and a more pronounced myopic shift. The cylindrical correction is used to address the astigmatic error, and the spherical correction is used to correct the myopia. The correct prescription for spectacles in a patient with simple myopic with the rule astigmatism typically involves a spherical correction of -3 to -5 diopters and a cylindrical correction of 1.5 to 2.5 diopters at 90 degrees.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not account for the astigmatic error in the prescription.
**Option B:** This option is incorrect because it does not provide a spherical correction for the myopia.
**Option C:** This option is incorrect because it provides an excessive cylindrical correction that is not necessary for simple myopic with the rule astigmatism.
**Clinical Pearl / High-Yield Fact**
When prescribing spectacles for patients with astigmatism, it is essential to consider the orientation of the astigmatic meridians and the type of astigmatism (regular or irregular). Regular astigmatism can be corrected with a cylindrical correction, while irregular astigmatism may require a more complex correction.
**Correct Answer:** C. -3.00 - 2.25 x 90.