What is irregular astigmatism -: (A) Perpendicular principal meridians, (B) Non perpendicular principal meridians, (C) Any of the above, (D) None of the above
Answer is B. 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