Artificial anterior chamber

Artificial anterior chamber

1. Artificial anterior chamber Dr.m.dinesh

2. AAC( Artificial anterior chambers) first described by Ward and Nesburn in 1976. utilized for manual lamellar dissection, automated lamellar dissection of the donor cornea using a microkeratome and Surgical objective is to obtain a lamellar corneal disk of desired thickness &diameter, an even surface with an uniplanar cut to augment the donor-host corneal interface, ease of operation, avoidance of disk perforation

3. Types of AAC Reusable AAC Moria AAC (manual), and Moria ALTK system (automated with microkeratome) Bausch and Lomb AAC (manual). Disposable AAC Barron Disposable AAC Coronet AAC

4. Moria AAC utilizes the Evolution3 console fully compatible with all Moria microkeratomes including the LSK, M2, and the CB units. It runs on wall current and has a battery back-up for uninterrupted use. It has two high pumps that provide a quick and stable vacuum for the procedure. The Moria unit for lamellar surgical procedures is called the ALTK system ( Automated lamellar therapeutic keratoplasty)

5. Moria AAC for ALK The Hanna trephine seats well on the Moria AAC and allows for stable partial thickness trephination of the donor cornea from the epithelial side. This is followed by manual lamellar dissection of the donor corneal tissue Unlike the Moria ALTK system, with the Moria AAC there is no control of the amount of corneal tissue that is exposed within the ring . Hence the diameter of tissue resection is determined by the diameter of the blade in the Hanna trephine.

6. Moria ALTK system This has the capability of raising or lowering the mounted donor corneo -scleral button thus altering the final diameter of the resected donor tissue. It comprises of an artificial chamber with central post on which the DCSB( donor corneoscleral button ) is placed with the endothelial side down after injecting Optisol solution from the donor corneal vial. Next the encasing cylindrical unit with the central opening for the cornea is moved into place such that the three posts descend into the corresponding slots in the base of the AAC unit, taking care to maintain the central position of the donor cornea. Turning this encasing unit in a clockwise fashion locks it in place and the DCSBis firmly mounted on to this AAC, with uniform pressure being applied to 360° of the scleral rim.

7. The intrachamber pressure can be titrated by injecting additional fluid from the attached syringe into the chamber, and locking the valve if the pressure is low, or alternatively aspirate fluid from the chamber if the intrachamber pressure is too high. The pressure can be checked using a Barraquer tonometer Depending on whether a LSK(LASIK) or CB( Corrazio-Barraquer ) microkeratome is used with this unit, the appropriate ring is chosen and screwed on to the unit.

8. 7.The amount of corneal tissue being exposed can now be adjusted by turning the rings and raising or lowering the central post

9. 8.The applanation lenses provide an estimate of diameter to be resected, ranging from 6 to 11 mm and for a CB unit on the right. (A) Moria ALTK system with applanating lenses ranging from 6.0 to 9.0 mm in diameter. (B) Moria ALTK system showing sequential assembly prior to use

10. 9.Fig showing the composite set-up for the LSK microkeratome on the left and for a CB unit on the right.

11. 10.The LSK microkeratome or a CB microkeratome can be used to complete the lamellar excision of the donor corneal disk. Moria LSK microkeratome being used with the Moria ALTK system. Moria CB microkeratome being used with the Moria ALTK system.

12. In summary, the 3 steps to the use of Moria ALTK system are as follows The donor cornea is sealed within the AAC, and the intrachamber pressure is adjusted to the required level. The surgeon selects the desired diameter of the cut. Perform the donor corneal resection

13. The Moria ALTK( Automated lamellar therapeutic keratoplasty) uses anterior lamellar keratoplasty (ALK) Deep lamellar endothelial keratoplasty (DLEK) Descemet Stripping Automated Endothelial Keratoplasty (DSAEK) Advantages : Reduced corneal astigmatism smooth keratectomy with seamless-edge margin

14. Bausch and Lomb AAC : Bausch and Lomb AAC, (A) Rectangular metallic base, (B) Central post, (C) Excess fluid collects in this space, (D) Two metallic channels with metallic valves for injection or aspiration of fluid to titrate the intrachamber pressure, (E) Fixation ring, (F) C-arm that can be extended or retracted, (G) Screw to tighten the C-arm in place

15. DCSB is placed on central post with the endothelial side down after applying viscoelastic material and fluid from the donor corneal vial. The central post has two openings for egress of fluid used to alter the intrachamber pressure. The metallic base has a circular space surrounding the central post for collecting the fluid that egresses out of the two openings in the central post. Two metallic channels are attached to the central post on one end and to metallic valves on the other end where a syringe filled with fluid can be attached. Once the DCSB is placed on the central post and the intrachamber space is primed with fluid, the circular fixation ring is placed over the donor corneoscleral rim and the C-arm is moved forwards such that it is above the flange of the fixation ring.

16. Once the C-arm is in its extended position the screw is tightened and this fixates the donor cornea within the B&L AAC. The intrachamber pressure is optimized by injecting fluid from the attached syringe and closing the valve to maintain the chamber pressure. The unit is now ready for lamellar dissection. Unlike the Moria AAC where the fixation pressure on the donor corneoscleral rim is applied 360° directly from the top,in the B&L AAC the C-arm applied pressure only on the proximal 180° of the flange of the fixation ring and the fixation ring in turn transmits the pressure to the scleral rim

17. A Barron radial vacuum trephine ( Katena , Inc.) of the desired diameter is placed on the moistened, epithelial surface of the donor cornea and suction is applied to fixate the trephine. Partial thickness trephination to desired corneal depth is f /by lamellar dissection of the donor cornea to obtain a lamellar donor corneal disk Advantages : can be used for manual dissection of the donor lamellar corneal disk. can be used for both DLEK and for anterior lamellar keratoplasty. Disadvantages : Cannot be used with a microkeratome.

18. Barron AAC( Katena , Denville, NJ) an innovative development in corneal transplant and lamellar surgery. Disposable device that allows a DCSB to be anatomically positioned ‘‘epithelial side up.’’ used to mount the donor tissue and maintain adequate pressure while lamellar dissection or full thickness trephination is being performed. designed in a bright blue color to provide a high contrast background for visualizing the cornea and aiding in the lamellar dissection of the cornea.

19. Design : The base has 2 ports with silicone tubing: in-line pinch clamps and female Luer -Lok connectors. Either port may be used to inject or aspirate viscoelastic material, balanced salt solution, preservation media, or air

20. 3.The design of the chamber allows the surgeon to firmly hold the 14- to 18-mm DCSB on a bed of viscoelastic material, pressurize it, and cut it from the epithelial side .

21. 4.The chamber is designed with a peripheral angle so that the surgeon can still use a regular set of lamellar dissection instruments with the disposable chamber

22. DCSB is placed onto the base the tissue retainer is carefully placed over the unit with the guideposts aligned; tissue retainer is advanced to the bottom of the base. AAC is then secured by placing the locking ring over the unit and turning it until the locked position is reached. Main steps

23. step-by-step description of preparing the DCSB using Barron AAC 1.Instruments req Disassemble the components of Barron AAC Have available the lamellar dissection instruments, donor trephine punch, guarded trifaceted diamond knife gentian violet marking pen, corneal preservation media balanced salt solution cohesive viscoelastic material, 25-gauge needle, Merocel sponges

24. Prepare 2 syringes and fill them with desired fluid or air medium ( ie , Optisol -GS solution and balanced salt solution). Connect the syringes to the 2 ports attached to the base of the artificial anterior chamber. Keep the pinch locks in the open position. Purge the first port with balanced salt solution and snap the pinch lock shut . Remove the excess solution from the base of the chamber. Using Optisol -GS solution, fill the second port until the fluid covers the base of the chamber. Leave the pinch lock in the open position

25. Apply viscoelastic material to the endothelial side of corneoscleral button. Place the DCSB on the base of the AAC, avoiding any air pockets to develop under the graft once the DCSB is on the base. Place the tissue retainer over the DCSB , aligning the guideposts; then, advance the tissue retainer to the bottom of the chamber base. Place the locking ring over the tissue retainer. While holding the tissue retainer with 1 hand, use the other hand to rotate the locking ring into the closed position. The DCSB is now securely in place. Infuse the Optisol -GS solution through the irrigation port and shut the pinch lock once the desired pressure is achieved.

26. 11.Proceed with the lamellar dissection as follows: Scrape off the epithelium of donor graft. Mark the temporal side and the horizontal direction on donor cornea. Prepare the surface markings on cornea as reference. Make a peripheral incision using the trifaceted diamond knife set at a depth of 0.4 mm. Proceed with typical lamellar dissection

27. Release some pressure within the AAC by unlocking the pinch lock on the Optisol -GS solution irrigation port. Place a Merocel sponge soaked in Optisol -GS solution on the corneal surface and proceed with the preparation of the procedures for the recipient To remove the corneoscleral button, release the locking ring with 1 hand while holding onto the tissue retainer with the other hand. Grasp the wings of the tissue retainer and gently remove the retainer from chamber base. Take the retainer ring off while keeping the cornea on the chamber base by gently using a needle to retain the donor tissue on the AAC. While the surgeon is separating the cornea from the chamber, the assistant should maintain pressure through the Optisol -GS solution irrigation port to prevent tissue collapse or buckling.

28. Mount the donor cornea (epithelial side down) onto a punch block using the previously made central marking on the surface of the cornea as a guide. Use a donor trephine to punch out the donor disc. Dry the periphery using a Merocel sponge. Ensure that the posterior lamellar disc can be separated from the anterior corneal layers. Fold the disc (endothelial side in) with an approximate 60/40 ratio. Make sure that a very thin layer of viscoelastic material protects the endothelial layer. The disc may now be inserted into the anterior chamber.

29. advantages diminish donor-host mismatch with full-thickness PK reduced cost, less time consuming and cumbersome disadvantage its design does not allow for the use of the chamber in conjunction with a microkeratome. it may take some experience to get AACustomed to the removal of the dissected donor cornea from the AAC complication inability to create a seal between the base of the chamber, the donor cornea, and the tissue retainer ring.

30. Coronet AAC Supplied with 2 tissue retaining heads (small 14.5-16mm, large 16-18mm) Single chamber design can be adapted to fit graft tissue between 14.5mm and 18.0mm Provides improved approximation b/w the donor button and patient cornea Designed to allow required intraocular pressure to be recreated Constructed to provide a leak free chamber Graticule cross hairs for improved precision Suitable for use with both manual trephines and femto-second lasers Weighted and broad base gives a stable platform Supplied sterile, single use only, one per box, 5 year shelf life

31. Tissue retaining heads

32. Prerequisite : The DCSB should have a minimal scleral skirt of 3.6 mm for successful use in an AAC for lamellar or penetrating keratoplasty (epithelial approach)

33. New non contact nonmechanical trephination using femtosecond laser excimer laser Er:YAG laser Advantages it is performed from the epithelial side in both donor & recipient; it avoids mechanical distortion during trephination by creating smooth and congruent cut edges eliminates a major factor for postkeratoplasty astigmatism Caution right exposure parameters, such as repetition rate and rotation speed to reduce the thermal effects of the laser

34. THAN Q Ref: Corneal Endothelial Transplant by Thomas John MD USA Use of a Disposable AAC for Trans-Epithelial Trephination and Endothelial Keratoplasty 2007 Lippincott Williams & Wilkins,

35. The Moria automated lamellar therapeutic keratoplasty system ( Moria /Microtek Inc, Doylestown, PA) includes a reusable stainless steel AACused to support the corneoscleral rim. designed with a gearless track on the base plate to AACept the use of a microkeratome head. The grooved base plate enables the microkeratome to pass across the cornea maintaining the same plane and direction. The Moria chamber offers the surgeon a reusable chamber and a fast method of preparing donor tissue of any diameter The Bausch & Lomb AACis also available to surgeons (Bausch & Lomb, St Louis, MO)