1. Ahmed Glaucoma Valve
Pf.박찬기/R2 유가영

2. Glaucoma drainage devices
Tube + Reservoir plate
Fibrous capsule forms filtering bleb around the plate
Tube
End
plate

3. Glaucoma drainage devices
1907
Rollet
Implant a horse’s hair
Maintain patency of a drainage fistula
Hair, wire, threads…..
Fail because of excessive scar formation near the limbus

4. Glaucoma drainage devices
1969
Dr. Anthony Molteno
Using large surface area to disperse aqueous near the limbus
1973
Drained the aqueous 8-10mm away from the limbus
Molteno device

5. Implant Design Open-tube drainage devices
Baerveldt, Molteno, Schocket implant
Flow-restricted drainage devices
Ahmed valve, Krupin valve implants
Krupin Baerveldt Ahmed Molteno

6. Implant material Materials that prevent fibroblast adherence
Polypropylene(may produce more inflammation)
Some Ahmed, Molteno implants
Silicone
Baeveldt, Krupin, Ahmed device

7. Basic principles Goal ! Non-valved implants resulting hypotony !!!
Remove aqueous out of the AC without causing hypotony
Maintain long-term lower IOP
Non-valved implants resulting hypotony !!!

8. Ahemd valve mechanism (1)
Two silicone thin elastomer membranes
8mm long, 7mm wide
Sandwiched and stretched by plates
Elastomer: 탄성중합체

9. Ahemd valve mechanism (1)
Self-regulated resistance
One-way regulation of the flow when IOP is above 8~10mmHg
Lowest rate of hypotony

10. Ahemd valve mechanism (2)
Venturi design
Overcome internal resistance in valve system
helps in evacuating aqueous from the valve, thereby helping to reduce valve friction.
Elastomer: 탄성중합체

11. Ahmed Glaucoma Valve Models
Material
Model
Size
Polypropylene S2
184mm² B1
364mm²
S3(pediatric)
96mm²
Silicone
FP7
FX1
FP8(pediatric)
FP-7 may lower IOP at 1yr more than S2

12. Prototype : model S2 Silicone tube Large polypropylene plate Plate
Thickness : 1.9mm
Width : 13.00mm
Length : 16.00mm
Surface area : 184mm²
Tube
Length : 25.00mm
Inner diameter : 0.305mm
Outer diameter : 0.635mm

13. Different biomaterials : model FP7
Silicone tube + Silicone plate
Good biocompatibility
60% edge thickness
Facilitate closure of conjunctiva
Three holes
Tissue growth through through the hole
Increasing the effective area available for drainage
Silicone may reduce inflammation and scarring during encapsulation of the device

14. Bi-plate : model B1 and FX1
Second plate(180mm²)
Increase the size of end plate & surface area
Greater aqueous drainage → lower IOP

15. Pediatric : model S3, FP8 Smaller in size Polypropylene Plate
Width : 9.60mm
Length : 10.00mm
Surface area : 96.00mm²
Tube
Length : 25.00mm
Inner diameter : 0.305mm
Outer diameter : 0.635mm
Polypropylene
Silicone

16. Pars plana clip : model PC and PS
Enter posterior chamber at sharp angle → kinking

17. Indications Young patients Failed trabeculectomy Neovascular glaucoma
Uveitic glaucoma
Severe conjunctival scarring
Refractory pediatric glaucoma
Aniridia

18. Contraindications There are no known absolute contraindications
Borderline corneal endothelial function may worsen

19. Surgical technique Position Tube priming Superotemporal quadrant
Superonasal quadrant
Post. edge of the plate may be close to the optic nerve with further posterior placement of the plate
Tube priming
BSS must be irrigated through the tube using 27G cannula
During sterilization process, membranes may adhere to each other → Ensure valve opens
Air removal

20. Surgical technique “No touch zone”
Creation of subconjunctival space in the superotemporal quadrant
Fornix based
Wet-field cautery in used sparingly(esp. around the tube insertion site)
Insertion of plate into subconjunctival space using nontoothed forceps
Avoid holding device over the valve body
→ May damage valve and fibrovascular ingrowth
Ant. edge of valve : 8-10mm posterior to the limbus
Suture with #8-0 or #9-0 nylon
“No touch zone”

21. Surgical technique Cutting the tube to the appropriate length
Bevel upward toward cornea
Tube tip extend 2~4mm into AC
Entering the AC through the limbal area with a 23G or 22G needle parallel to the iris plane
Approximately 0.5mm posterior to the limbus

22. Surgical technique
Tube insertion into the AC via the needle track using nontoothed forceps
Should not touch cornea, iris, lens
Posterior to schwalbe’s line and anterior to the iris plane
Loosely secured to sclera, avoiding constriction of the tube
Suturing of donor sclera or other patch material(pericardial tissue, fascia lata…) over the tube area at the limbus
Prevent tube erosion

23. Surgical technique : modifications
Viscoelastic
Through paracentesis, temporally
Maintain AC at normal depth
SO filled eye
Plate positions : inferotemporal
Minimize SO loss through the tube
Limbal based scleral flap
Post vitrectomized eye
Pars plana insertion prefered
Eliminate tube-cornea touch
Model PC and PS

24. Complications Hypotony Choroidal effustion
Less common with Ahmed Glaucoma vlave

25. Complications All glaucoma drainage implants
Obstruction of tube by fibrin, blood, iris, vitreous
Tube retraction and erosion
Tube kink
Motility disturbance
Corneal decompensation and graft failure
Endophthalmitis
Retinal detachment

26. Complications Elevated IOP Hypotensive phase(7-10days)
low IOP, conj/corneal edema, conj. vessel cong.
Hypertensive phase(1-4weeks)
IOP elevation, capsule formation
The incidence of the hypertensive phase may be lower after silicone plate(FP7) than polypropylene plate(S2)
Stabilization(3-6month)
Early IOP increase
Tube obstruction by fibrin, blood, iris, vitreous membrane, silicone oil

27. Complications Failure of priming Fibrovascular ingrowth Uncommon
Late failure
Gap between valve chamber and plate during manipulation of the valve

28. Reference Shields textbook of GLAUCOMA 6th edition, ALLINGHAM
Shaarawy GLAUCOMA surgical management, SAUNDERS
Chen, Teresa C., Glaucoma surgery, SAUNDERS

29. 감사합니다