Capstone Week #1 - Brinkley Brooks
Research:
Article 1: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5322839/#b25-opth-11-357
- 10% reduction of risk of glaucoma for every 1 mmHg decrease in IOP until threshold is met
- IOP can be lowered through medical management, lasers, and surgeries such as Ahmed valve
- Excessive capsule fibrosis is an issue with the Ahmed valve and a very common side effect
- Silicone seems to create less of a hypertensive phase than polypropylene because it is less inflammatory
- How an Ahmed Valve works: thin silicone membranes that open and close due to the IOP variations. Valve opens to decrease IOP and closes to increase IOP.
- Threshold is 8-12 mmHg
Article 2: https://www.eyephysiciansoflongbeach.com/services/glaucoma-long-beach/ahmed-valve/
- IOP increases due to aqueous humor build up
- Drainage happens through the shunt to the bleb
- 60-80% success rate for the Ahmed valve surgery
- Some complications include inflammation, redness, initial elevated IOP until bleb is fully functional, clogging of shunt, etc.
- Surgery does not improve vision, but prevents it from getting worse
- How to insert Ahmed Valve:
- Cut on sclera
- Valve goes into pocket
- Use drops post op.
- Operation takes 1-1.5 hours
- Outpatient surgery
- Stents are used for glaucoma and child NLD obstructions
- Imaging machines help diagnose glaucoma early on
- Eye drops are the first round of defense for treatment
- Fibrosis remains the major impediment to lowering IOP
- Trabeculectomy prevails as the most effective strategy for getting a constant IOP reduction
- Increased mechanical load, or distinct growth factors can increase scaring and fibrosis
(1) sutures
(2) blood vessel-derived cells, cytokines and growth factors
(3) aqueous humor-derived growth factors
(4) shear force stimulation by interstitial fluid flow
(5) signaling molecules released from ECM storage sites
(6) myofibroblast transdifferentiation leading to matrix deposition and tissue compaction
Video #1: https://www.youtube.com/watch?v=cFt8yomVB7A
- This video showed an Ahmed Valve surgery
- First, the valve needs to be primed with solution to remove air, so the eye does not have to use pressure to get it out.
- The superior temporal quadrant is the 1st choice for placement of the device
- The sclera is cut and a deep pocket is formed
- Valve is pushed into pocket
- The valve is sutured into place
- A needle hole is made for the tube to go inside
- Tube is inserted into hole and sutured into place
- Cover tube with donor tissue
Video #2: https://www.youtube.com/watch?v=z0ohS8nTioI
- Trabecular by pass stent surgery provides a more direct way for the fluid to leave the eye.
- The optic nerve is damaged when fluid does not drain properly, causing vision loss.
- A cornea incision is made, so the stent can be inserted.
Client Meeting Notes:
- Helpful Resource: SOLX company
- Purpose/Goal of Project: Make an improved device similar to an Ahmed Valve. Make the device with variable resistance, 3 levels. High for post op, medium for a little while after surgery, and low for long term.
- Complications Ahmed Valve Faces: After every year post surgery, 10% of valves fail. The main issue that patients have is fibrosis. A device that is able to have variable resistance could be able to decrease or diminish fibrosis.
- The extra medical device in the project description only has to be made if the valve that is created needs something to help doctors insert it.
- The volume measurement device only needs to be used in a lab setting, not an eye that is still in a human eye.
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