Tharppana is of three types – Snehana, Lekhana and Prasadana 

Tharppana may be carried out when eyes are fatigued, inactive, dry, rough, in-jured, in patients with Vaatha and Pittha vitiation, where there is squint, loss of lashes, clouded vision, difficulty in opening eyes, congestion of conjunctival blood vessels, black outs, sub-conjunctival hemorrhage, conjunctivitis, glaucoma, trigeminal neural-gia, corneal opacity, after relieving conditions like redness, excessive lacrimation, pain, irritation and exess excretions (Ashtaangahrudaya Soothra 24-1). 

1.On cloudy days 

2.Those who had not undergone Nasya 

3.Those who are contra-indicated for Nasya