MN 38: How do aging-&-death cease when the eye sees a form?

On seeing a form with the eye, he lusts after it if it is pleasing; he dislikes it if it is unpleasing. He abides with mindfulness of the body unestablished, with a limited mind, and he does not understand as it actually is the deliverance of mind and deliverance by wisdom wherein those evil unwholesome states cease without remainder. Engaged as he is in favouring and opposing, whatever feeling he feels—whether pleasant or painful or neither-painful-nor-pleasant—he delights in that feeling, welcomes it, and remains holding to it. As he does so, delight arises in him. Now delight in feelings is clinging. With his clinging as condition, being comes to be; with being as condition, birth; with birth as condition, ageing and death, sorrow, lamentation, pain, grief, and despair come to be. Such is the origin of this whole mass of suffering.

This sutta is basically telling that when there is clinging there is future birth. This is what Ven Sariputta said about clinging in the Sammaditthi sutta.

And what is clinging, what is the origin of clinging, what is the cessation of clinging, what is the way leading to the cessation of clinging? There are these four kinds of clinging: clinging to sensual pleasures, clinging to views, clinging to rituals and observances, and clinging to a doctrine of self. With the arising of craving there is the arising of clinging. With the cessation of craving there is the cessation of clinging. The way leading to the cessation of clinging is just this Noble Eightfold Path; that is, right view... right concentration.

So the four kinds of clinging are clinging to sensual pleasures, views, rituals and observances, and clinging to a doctrine of self. Clinging to becoming/existence or a being in the next life.

"And what is being, what is the origin of being, what is the cessation of being, what is the way leading to the cessation of being? There are these three kinds of being: sense-sphere being, fine-material being and immaterial being. With the arising of clinging there is the arising of being. With the cessation of clinging there is the cessation of being. The way leading to the cessation of being is just this Noble Eightfold Path; that is, right view... right concentration.

Sense-sphere being are humans and devas. Fine-material beings are brahmas and the immaterial beings are beings who were born there because of the fifth jhana and higher.

So how do aging and death cease when an eye sees a form?

On seeing a form with the eye, he does not lust after it if it is pleasing; he does not dislike it if it is unpleasing. He abides with mindfulness of the body established, with an immeasurable mind, and he understands as it actually is the deliverance of mind and deliverance by wisdom wherein those evil unwholesome states cease without remainder. Having thus abandoned favouring and opposing, whatever feeling he feels, whether pleasant or painful or neither-painful-nor-pleasant, he does not delight in that feeling, welcome it, or remain holding to it. As he does not do so, delight in feelings ceases in him. With the cessation of his delight comes cessation of clinging; with the cessation of clinging, cessation of being; with the cessation of being, cessation of birth; with the cessation of birth, ageing and death, sorrow, lamentation, pain, grief, and despair cease. Such is the cessation of this whole mass of suffering.

This basically means that when you don’t lust after it if it is pleasing; don’t dislike it if it is unpleasing and abides with mindfulness of the body and with an immeasurable mind, and understands as it actually is the deliverance of mind and deliverance by wisdom wherein those evil unwholesome states cease without remainder and don’t crave or delight there is cession of clinging. Having thus abandoned favouring and opposing, whatever feeling you feels, whether pleasant or painful or neither-painful-nor-pleasant, you won’t delight in that feeling, welcome it, or remain holding to it. As he don’ so, delight in feelings ceases in you. With the cessation of delight and craving comes cessation of clinging comes cessation of a being after death. This means you won’t be reborn as humans, devas, Brahma or in the immaterial world. I think becoming/existence would be a better translation than “being”. With the cessation of becoming comes cessation of birth. With the cessation of birth comes cessation aging and death. I used some words from the sutta.

This is how an arahant does not experience aging and death in future lives. An arahant does not experience aging and death in this life because he don’t regard anything in this world as “mine”, “me”, “I”, or self. So even though his body age he doesn’t experience aging because he doesn’t assume himself to be the body. He doesn’t have the view “my self” or I am the one who experience or know

The eye isn't a major player in these two verses. The major player is the shifting of ones attention to the imperceptibly fleeting aggregated structure of self that arises based on data from the eye. Ultimately, seeing is the same for everybody and at anytime during the lifespan. The Buddha was pointing out here in the first verse that what occurs after the seeing is the selfish and divisive mental construction that defines your seeing as being 'mine' and that by - in the second verse - ferreting out this 'me' business we will come to see the ultimate nature of 'me', 'mine' and 'self' as being void. The eye is just passing the information of what is seemingly 'out there' to the brain.

Conventionally, and from my current observations aging and death of the physical form doesn't cease but the Buddha was probably referring to Nirvana so in this sense aging and death ceases by practice.

If you're interested more in the eye then biology might have more relevant information.

Most probably imagine "ceases" to mean something like "ends". The fact is, "ceases" is a translation of "nirodha" which means "make it so it won't arise", "remove a necessary cause of arising" (what I call "prevent" or "dis-enable" in short). So the meaning of the passage is, when the eye sees a form, ear hears a sound etc. - if there is no like/dislike or craving/aversion modality established, then the cause that would normally push the wheel of D.O. to keep on spinning is not created. Because the cause is not created, the chain of events starting from the cause is not started. If this is only done occasionally with one form, then the other occasions would still give rise to the chain of events -- would push the wheel on spinning. But if this is done consistently for all forms, sounds, dharmas etc. - then the chain of D.O. is nirodha (prevented).

It is prevented because, as is explained in standard D.O. descriptions, enabled by Ignorance arise Tendencies. These tendencies are exactly the tendencies to like/dislike and to act based on this liking/disliking. Such tendencies feed and grow the entity-centric thinking and acting. This entity-centric thinking and acting gradually hardens into I-making, which culminates in death.

When stimuli like forms, sounds, dharmas etc. are taken "as-is", without forming personal attitude to them, the entity-centric thinking and acting is not perpetuated. Because it is not perpetuated, the I-making is not perpetuated. When I-making is not perpetuated - death does not apply.