Thirukkannāḍi — The Sacred Mirror
Thirukkannāḍi in Śrī Vaiṣṇava ritual vocabulary is the mirror used in the service of Bhagavān. After or during alaṅkāra, the mirror may be respectfully presented as darpaṇa-upacāra so that the beautifully adorned arcā form is served in the manner prescribed by the relevant tiruvārādhana or temple procedure.
Mirror as Upacāra
The offering belongs to the wider hospitality and royal-service framework of upacāras: Bhagavān is not an inert object being inspected, but the living Lord to whom a mirror is presented as an intimate act of kainkaryam. The point in the sequence, accompanying mantra and manner of presentation follow the applicable Āgama and inherited practice.
In ordinary modern Tamil, kaṇṇāḍi can also refer to spectacles. That secular meaning is distinct from the sampradāya term thirukkannāḍi used for the sacred mirror; the ritual word does not derive from an invented expression meaning 'divine light for the eyes.'