why does the lens of sheeps eye appear hard and is it like this in a living animal?

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Hello045834
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lyer_in_hellfyre
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(Original post by Hello045834)
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Could ya pls explain what do you mean by sheep's eye's lens being hard? :ta:
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Hello045834
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(Original post by lyer_in_hellfyre)
Could ya pls explain what do you mean by sheep's eye's lens being hard? :ta:
When you dissect the sheeps eye and you feel the lens, it feels hard instead of flexible...
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lyer_in_hellfyre
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(Original post by Hello045834)
When you dissect the sheeps eye and you feel the lens, it feels hard instead of flexible...
Edit : please check mcpatgh- Sheldon's post below :ta:
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macpatgh-Sheldon
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(Original post by lyer_in_hellfyre)
It occurs in living organisms, the drying of cornea, becoming more opaque and hard.
Perhaps you could check this out https://arxiv.org/pdf/1804.01962
Good morning lyer.*,
Firstly thank you for your kind action in conferring more than one rep to me lately!

Apologies if this sounds a little critical [and your abundant answers to Qs are accurate, detailed and useful]; however, there is no direct correlation between the consistency of the cornea and that of the crystalline lens. In fact, the cornea is the outermost part of the anterior aspect of the eyeball, being covered in front only by the bulbar conjunctiva, WHEREAS the crystalline lens is actually in the posterior chamber i.e. behind the iris (the reason for the white appearance of ONLY the pupil aperture in very elderly patients with severe cataract even of the subcapsular type).

To come to OP's Q, the lens does feel quite firm both in vitro and in vivo [latter only possible to feel during e.g. catarectomy operation] because it is composed of tightly packed dense lens fibres aligned in a highly organized fashion [which are actually dead cells] and is surrounded by the lens capsule which is also tightly adherent to the cortex [outer part but just inside the capsule] of the lens. This arrangement has been honed through evolution, especially so in us mammals, in order to permit almost complete transparency of the lens [except when this is compromised in cataract due to age or other factors e.g. diabetes mellitus, radiation, some drugs like corticosteroids], which is, of course, crucial to the transmission of light to reach the retina, and hence to allow the miraculous feat of nature of vision.

I hope this answers your Q.

M.
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lyer_in_hellfyre
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(Original post by macpatgh-Sheldon)
Good morning lyer.*,
Firstly thank you for your kind action in conferring more than one rep to me lately!

Apologies if this sounds a little critical [and your abundant answers to Qs are accurate, detailed and useful]; however, there is no direct correlation between the consistency of the cornea and that of the crystalline lens. In fact, the cornea is the outermost part of the anterior aspect of the eyeball, being covered in front only by the bulbar conjunctiva, WHEREAS the crystalline lens is actually in the posterior chamber i.e. behind the iris (the reason for the white appearance of ONLY the pupil aperture in very elderly patients with severe cataract even of the subcapsular type).

To come to OP's Q, the lens does feel quite firm both in vitro and in vivo [latter only possible to feel during e.g. catarectomy operation] because it is composed of tightly packed dense lens fibres aligned in a highly organized fashion [which are actually dead cells] and is surrounded by the lens capsule which is also tightly adherent to the cortex [outer part but just inside the capsule] of the lens. This arrangement has been honed through evolution, especially so in us mammals, in order to permit almost complete transparency of the lens [except when this is compromised in cataract due to age or other factors e.g. diabetes mellitus, radiation, some drugs like corticosteroids], which is, of course, crucial to the transmission of light to reach the retina, and hence to allow the miraculous feat of nature of vision.

I hope this answers your Q.

M.
Good Morn M!
The posts deserved them just like this one (i need to wait another another day tho)

:ta: It's better to be corrected than to be misinformed and am really grateful for the detailed answer
Just to reconfirm, the lens was never flexible to begin with?
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macpatgh-Sheldon
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Hello,

Thanks for your kind words, and your mature-sounding understanding. Good point [thank you!]:-

1. In babies, I would say the lens is noticeably more flexible [see (2) as well), although babies less frequently require ophthalmic surgery, so even experienced ophthalmologists would only "feel" a live baby's crystalline lens occasionally [to be honest, I do not know from first-hand experience because I have assisted surgeons only in adults].
2. Oc, the lens has to "thicken" out of necessity during accommodation [to increase converging power [more plus Rx [prescription] to permit near vision [e.g. reading, sewing]] by contraction of the ciliary muscle [which is like a circumferential ring around the lens], and the slackening of the suspensory ligament, so a certain degree of "softness" is essential for its normal function, and accommodative capacity is always greater in children and young adults (around +10 dioptres), whereas in people over 40-450 [depending on distance Rx and other factors], this capacity is drastically reduced [to 1-2 dioptres], causing presbyopia, with a concomitant need for "reading glasses".

M
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(Original post by macpatgh-Sheldon)
Hello,

Thanks for your kind words, and your mature-sounding understanding. Good point [thank you!]:-

1. In babies, I would say the lens is noticeably more flexible [see (2) as well), although babies less frequently require ophthalmic surgery, so even experienced ophthalmologists would only "feel" a live baby's crystalline lens occasionally [to be honest, I do not know from first-hand experience because I have assisted surgeons only in adults].
2. Oc, the lens has to "thicken" out of necessity during accommodation [to increase converging power [more plus Rx [prescription] to permit near vision [e.g. reading, sewing]] by contraction of the ciliary muscle [which is like a circumferential ring around the lens], and the slackening of the suspensory ligament, so a certain degree of "softness" is essential for its normal function, and accommodative capacity is always greater in children and young adults (around 10 dioptres), whereas in people over 40-450 [depending on distance Rx and other factors], this capacity is drastically reduced [to 1-2 dioptres], causing presbyopia, with a concomitant need for "reading glasses".

M
Thanks a lot M
Last edited by lyer_in_hellfyre; 1 day ago
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