Ординатура / Офтальмология / Английские материалы / Step by Step Minimally Invasive Glaucoma Surgery_Garg, Melamed, Bovet, Pajic, Carassa, Dada_2006
.pdf
202 Step by Step Minimally Invasive Glaucoma Surgery
Fig. 12.2: The drill held with the tip unassembled just before the surgery
Fig. 12.3: Milling set of metallic tips. The set includes tips for cutting, other for refining
Milling Trabeculoplasty 203 
Fig. 12.4: The notched hemispherical metallic tips to polish but not cut the remaining scleral thickness
Surgical Steps
1.The eyelids are sterilized with ophthalmic Betadine solution (Purdue Frederick, Norwalk, CT), and after the sterile drape was placed, a lid speculum was inserted.
2.An 8-mm fornix-based conjunctival flap is prepared superiorly and Tenon’s capsule was retracted. Bipolar cautery is then applied sparingly to cauterize individual limbal vessels one by one to achieve homeostasis preserving as much as possible the episcleral vessel.
3.A superficial scleral flap of 4 × 4 mm hinged at the limbus was designed using ultra sharp mini blade such as the No. 7511 Beaver, extending 1 mm into the clear cornea (Fig. 12.5A). The thickness of the flap should be between 200 and 250 microns. The incision
204 Step by Step Minimally Invasive Glaucoma Surgery
Fig. 12.5A: Fashioning of the scleral flap size and site
should be made definitively, without multiple tentative strokes (Fig. 12.5B). The edge of the scleral flap was then grasped with Hoskins forceps and gently retracted. The scleral dissection is carried out using a crescent-style blade extending the lamellar dissection anterior tell the blue limbal zone then more anteriorly until 1 or 2 mm of a clear cornea is reached and the iris details can be seen through the deep layers of corneal tissue (Figs 12.5C to E).
4.Under high magnification, a rectangular dry area of the scleral bed about 3 × 3 mm inside the superficially created flap is selected to start milling and the milling motorized drill was applied without pressure allowing to drill and refine the remaining scleral thickness in a linear pattern to leave a thin layer of sclera underneath (Fig. 12.6). The site of milling
Milling Trabeculoplasty 205 
Fig. 12.5B: The scleral incision as being completed
Fig. 12.5C: Beginning of the lamellar dissection
206 Step by Step Minimally Invasive Glaucoma Surgery
Fig. 12.5D: Lamellar dissection of the scleral flap
Fig. 12.5E: Completion of the lamellar dissection
Milling Trabeculoplasty 207 
should be applied at the surgical limbus in order to expose the canal of Schlemm. The refining is carried anteriorly and downwards until the blue-gray color of the choroid should appear through the residual scleral fibers (Fig. 12.7). When reaching the appropriate depth, the canal openings are identified by passing a hook through them (Figs 12.8A and B).
5.The process of “Unroofing” of the canal is automatically done using the motorized milling drill but care should be taken not to apply any pressure (maintaining the high velocity) and leave the drill to refine the tissues. After being unroofed, the inner wall of Schlemm’s canal appears as a dark line, just anterior to the scleral spur. The milling is continued anteriorly towards the cornea to remove the sclero-
Fig. 12.6: The scleral bed refined and grazed using the milling motorized drill in dry field through the remaining scleral thickness in a linear pattern to leave a thin layer of sclera below and a width of 3.5 mm
208 Step by Step Minimally Invasive Glaucoma Surgery
Fig. 12.7: The refining is carried anteriorly and down until the roof of Schlemm´s canal can barely be visible
corneal trabecular meshwork (TM), which typically exhibits a granular texture. If phacoemulsification is combined with the procedure, the superficial corneal flap is reposted and a clear-corneal incision is prepared then the phaco is performed. After the phaco has been completed the milling is carried out anteriorly and 1-2 mm of Descement´s membrane is exposed by milling anterior to the canal till clearcorneal tissue is reached and iris details could be identified though the remaining thin sheet of TM. Another alternative to create the descemtic window is using a mini-blade starting with down-up incision at one of the two opening of the canal then with a shaving movement a block of tissue is excised moving towards the other opening of the canal (Figs 12.9A to C).
Milling Trabeculoplasty 209 
Figs 12.8A and B: A hook is passed through the opening of the canal to insure adequate level of dissection and milling
210 Step by Step Minimally Invasive Glaucoma Surgery
Figs 12.9A and B
Milling Trabeculoplasty 211 
Figs 12.9A to C: Deroofing of Schlemm’s canal is done:
a.2 incisions are created at both sides starting from the opened Schlemm canal and anteriorly tell reaching the clear corneal under the flap
b.The site of incision is checked again and repeated on the other side
c.The roof of the canal is removed using the surgical knife
6.At this stage of the procedure, aqueous humor should be seen percolating through the trabeculo-descemetic membrane. If still there is reduced outflow, stripping the inner wall of Schlemm´s canal was done (Fig. 12.10) to increase aqueous outflow and then further milling is carried out to smoothen the surface (Fig. 12.11). Ultimately, only the trabeculo-descemetic membrane remains intact. Visible filtration of aqueous through the thin trabeculo-descemetic membrane should be obtained. Dilatation of Schlemm´s canal could be also done by inserting a cannula into the canal for 0.5 or 1 mm.