###Rationale: It is characterized by an irregular change of refractive power in different meridia. There are multiple meridia which admit no geometrical analysis.the principal meridians are not perpendicular to each other Image : Corneal topographies in regular and irregular astigmatisms. A: Regular astigmatism of 4.0 diopters with two perpendicular main meridians. B: Irregular astigmatism of 6.5 diopters with non-perpendicular main meridians. Reference : A K KHURANA OPHTALMOLOGY,Edition 4,Page-38

###Answer: OPTION B IS CORRECT.
###Question: What is irregular astigmatism -
###Options:
A. Perpendicular principal meridians
B. Non perpendicular principal meridians
C. Any of the above
D. None of the above
