# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DbNzT57Al3g
- **Gondola URL:** https://gondola.cc/posts/68267161-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/a8440066be.jpg
- **Posted:** 2026-07-25T12:21:50.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

The lens inside your eye holds the highest protein concentration of any tissue in the body, and no blood supply at all. Over decades those crystallin proteins oxidise, unfold and clump together. The clumps scatter light. That is a cataract, and the only fix is taking the lens out.

Modern removal is phacoemulsification, and it is a genuinely strange piece of engineering:

- A 2.2 mm incision is cut into clear cornea in two planes, so internal pressure presses the flap shut against itself. No sutures.
- The anterior capsule, a basement membrane around 14 microns thick, is torn in a continuous circular curve roughly 5 mm across. Torn, not cut. A controlled tear follows the collagen and resists propagating under stress.
- Fluid is injected beneath that opening to float the lens free of its shell.
- A titanium needle oscillating at 28 to 45 kHz enters. Stroke length is only 50 to 100 microns, but at those frequencies the tip destroys lens material through direct impact and through cavitation, microbubbles collapsing against the nucleus.
- Emulsified lens is aspirated at 25 to 40 mL per minute while balanced salt solution replaces the volume in real time.

The pressure balance is the hard part. When a fragment occludes the tip, vacuum builds behind it toward 400 mmHg. The instant it clears, fluid surges out and the chamber can collapse onto the needle. Modern machines sense that occlusion break and throttle flow within milliseconds.

What goes back in is a folded acrylic lens injected through the same 2.2 mm wound, unfolding inside the empty capsular bag. Its power is chosen beforehand from axial length measured by optical interferometry to about 20 microns, corneal curvature, and formulas regressed across hundreds of thousands of eyes.

Twenty minutes. Local anaesthetic. Roughly 30 million performed a year.

We learned to dissolve a solid inside a living chamber without letting the chamber notice.

#stemantics #ophthalmology #biomedicalengineering #medtech #optics

## Stats

- **Views:** 48,728
- **Likes:** 5,787
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- **Comments:** 86

## Tags

optics, medtech, biomedicalengineering, ophthalmology, stemantics

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