ABSTRACT
The Modified Preliminary Drill represents my other inventions: the indirect effect (Yee, 2011). The Modified Preliminary Drill is a variation of the Preliminary Drill. You will apply it more frequently than the Standard Drill to treat various types of secondary refractive errors. I designed it to treat anisometropia, simple astigmatism, and “compound astigmatism” (or compound myopia and astigmatism). It is the decrease in the Modified Preliminary Drill’s intensity compared to the other drills that make it appropriate in the treatment for secondary refractive errors. The correct intensity influences the crystalline lens to flatten just the right amount to cause the eyeball to retract. If the crystalline lens flattens excessively, the eyeball cannot respond properly.
To treat anisometropia, you do not have to abide by its classical definition: a disparity of −1.0 D between the right and left eye. If the disparity is −0.75 D, you can still treat it as anisometropia by following the same protocol. (Refer to the chapter Treating Anisometropia for more information.) Although a disparity of −0.50 D does not qualify as anisometropia, you can still immediately treat it by applying the Modified Preliminary Drill without starting with the Preliminary Drill. (Refer to the chapter Treating Mild and Moderate Myopia for more information.) To treat astigmatism, it can take the form of simple astigmatism, or it can be combined with myopia, anisometropia, or even anisometropic amblyopia. (Refer to the chapter Treating Astigmatism for more information.)
