If intraocular pressure rises sharply due to blocked drainage, what happens to the optic nerve, explaining why visual field defects initially spare central vision?

💡 Explanation

The lamina cribrosa acts as a sieve for optic nerve axons; because elevated intraocular pressure deforms the lamina, peripheral nerve fibers are compressed before central fibers. Therefore, peripheral visual field loss occurs initially, rather than central, because of this mechanical effect, rather than uniform cell death or blood flow changes.

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