In Ayurveda, the local treatment procedures of netra are explained in the name of Netra Kriya Kalpa.
क्रियानां तर्पण पुटपाकादीनां कल्पनं कारनं क्रियाकल्प:// (Su. U. 18/2)
Kriya means therapeutic action and kalpana means formulations. That means the formulations which are used for therapeutic action against the netra rogas is called as Kriya kalpa.
It is a bahirparimarjana chikitsa and gives the best results in curing the eye diseases .It gives best results in eye disease than the oral medication because
1. The drugs given orally has to go through the digestion process with the influence of pachaka pitta. While the drugs administered through kriya kalpa are not digested by it and possibly rectify accumulated dosha.
2. The drugs used as oral medication has difficulty to cross blood-aqueous, blood-vitreous and blood-retinal barriers to reach the target tissues of the eye. The topical drugs can reach there and achieve higher bio-availability.
3.Kriyakalpa can helps in controlling the tissue contact time so and they are selected depending upon the stage and severity of the disease.
4. The medications can be judiciously selected. i.e, to increase ushna or sheeta, snigdha or rooksha in the local area.
Thus high concentration of the drug can be achieved by applying the medicines to eye. 4
Many local therapeutics are described for eye diseases in different contexts.
Acharya charaka explained three kriya kala.
Acharya Susrutha explained 5 kriyakalpa.
। तर्पणं पुटपकाश्च सेक आस्चोतन अंजने //
( Su. U. 18/4)
Sarangadara mentioned 7 kriyakala.
सेक आश्च्योतनं पिंडी विडालस्तर्पण तथा /
पुटपाको अन्जनं चैभि: कल्पनैर्नेत्रमुपाचारेत्//
(Sar. U. 13/1)
Vagbhata followed Susrutha and Bhavamisra followed Sarangadhara in the description of kriyakalpa.