The Chakshu Upanishad (Netra Upanishad)

The Chakshu Upanishad, also known as Netra Upanishad, is a short minor Upanishad focused on a practical vidya (sacred knowledge/ mantra practice) for curing eye diseases, strengthening eyesight, and preventing blindness. It is is generally classified among the minor or later Upanishads associated with practical or remedial purposes rather than pure philosophical inquiry into Brahman/Atman. 

The Upanishad opens by announcing a pamhita-siddha (accomplished merely by recitation) knowledge that destroys eye diseases from all sides and makes the eyes radiant:

Now we shall expound the Châkshucî vidyâ, which is perfected by mere recitation and removes diseases of the eyes. By it all eye diseases are destroyed everywhere, and the eyes become lustrous. It then gives the main mantra/practice, which includes repeated invocations such as:

“Cakcuh cakcuh cakcuh tejah sthiro bhava”
(Eye, eye, eye — become firm in brilliance/energy)

• Requests for protection, swift removal of eye diseases, revelation of pure radiance, prevention of blindness, welfare, and uprooting of past-life karmic obstacles to sight.
• Salutations to the divine giver of eye-brilliance (Bhâskara/Sûrya), the compassionate nectar-like one, the Sun in its various aspects (including references to the three gunas and the classic “Asato mâ sad gamaya...” peace mantra).

It states that a Brâhmana who regularly studies this Châkshumatî vidyâ never suffers eye disease, nor does blindness appear in his family line. Mastery is said to be complete when one teaches it to eight Brâhmanas.

The text concludes with a solar hymn-like portion (describing the all-formed, golden, fiery Purusha who is the source of the universe and rises for living beings) and further salutations, including to forms of Vishnu with lotus/beautiful eyes (Punarîkâksha, etc.), ending with “Iti Châkshusopanishat sampûrnâ.”

It is a short text, essentially a specialized mantra-vidyâ rather than a lengthy philosophical dialogue. It is a compact, practical Upanishadic text dedicated to the health and radiance of the eyes through devotion to and invocation of the Sun.