Perform at least a partial fluid-air exchange (so that the fluid meniscus lies below the sclerostomies). Having air on the inside of the sclerotomies prevents vitreous exiting the wounds, as it tends to stick to the interior of the eye wall, and enhances self-sealing. In addition, it helps to determine if the wounds are air tight - the sclerostomies will “bubble” if not and should be sutured.
If, during the fluid-air exchange in a phakic patient a “donut” of air develops peripherally (trapped between the lens and vitreous base), insufficient vitrectomy has been performed and more is required (Figure 3.2.1).
Remove the superior (light pipe and vitrector) cannulae. Remove the cannula at the same angle that it was inserted. One can insert an instrument such as the light pipe or vitrector cutter into the cannula to plug the port and pull the cannula up around it. This potentially prevents vitreous prolapse into the wound.
Adjust the IOP if necessary before removing the infusion cannula.
After removing each cannulae, use a cotton bud (q-tip) or tip of the cannula to momentarily press on the anterior lip of the wound. This ensures better closure of the sclerostomy if it is not to be sutured. Some surgeons use the reverse end of a cotton bud (q-tip). Others like to gently “squeeze” the sclerostomies using conjunctival / Moorfields forceps, which facilitates closure.
Suturing Small-gauge Sclerostomies:
Suturing the sclerostomies is necessary under the following circumstances:
Most surgeons use 7-0 or 8-0 Vicryl in 3-1-1 throws. Use a blunt forceps to hold one of the other cannulae while suturing. If unsure where the sclerostomies are (e.g. because of conjunctival ballooning), use the back (bent part) of the needle holder to flatten the conjunctiva over the sclerostomy to allow visualization. Some surgeons tie a 4-throw bowtie suture and remove it at the slitlamp on the first post-operative day (not for silicone oil). Subconjunctival gas can be removed using a 30G needle on an empty syringe (it will stay subconjunctival for weeks in case of C3F8).
(C): If a complete fluid-air exchange is required, a silicone soft-tipped extrusion cannula is safer to use than the vitrectomy cutter. Fluid can be drained at the optic disc.
e.g. Subconjunctival cephalexin and dexamethasone.
Most surgeons choose to inject subconjunctival antibiotics (e.g. a cephalosporin) and steroid (e.g. dexamethasone) at the conclusion of the operation (Figure 3.2.3). Injecting these near the sclerostomy sites further displaces the conjunctiva from these sites. Warn the patient that they may feel a “sting” prior to injecting. Under certain circumstances (e.g. macular oedema, uveitis), intravitreal or posterior sub-Tenon’s triamcinolone acetonide may be indicated (Figure 3.2.4 and Figure 3.2.5).
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