ī is substituted for idam and kī for kim before the words 1. dṛg 2. dṛśa and the affix vat,
Thus इदृक्, ईदृशः and इयान्, कीदृक्, कीदृशः and कियान् ॥ ईवत् and कीवत् are changed to ई + इयत् and को + इयत् by 5.2.40 and the long ई is elided by 6.4.148 : and we get इयत् and कियत् ॥
Vart:- So also before दृक्ष, as ईदृक्षः and कीदृक्षः ॥,