Complications of drainage include hemorrhage, choroidal detachment, retinal incarceration, iatrogenic retinal holes, and infection. Cibis wrote about the uncertain nature of a release of subretinal fluid: "This is perhaps the most dangerous step in any of the retinal detachment procedures presently employed, except where Custodis' technique is used" .
Intraocular bleeding (major retinal, subretinal, or vitreal) was seen in 14.4% of drained versus 3.3% of undrained cases . Choroidal detachment occurred in 8.6% of drained versus 1.6% of undrained cases. Both bleeding and choroidal detachment reduced the probability of reattachment and good postoperative vision in this population-based study . Choroidal edema was found more frequently in older patients after drainage, hypotony, encircling, larger buckles, more extensive cryopexy and more complete vortex vein obstruction .
Kreissig,who drained 98.7% of cases from 1966 to 1969, reported intraocular hemorrhage (smallest or larger) in 15.6% . In 1975, Blagojevic, who drained 96% of cases, found intraocular hemorrhages in 16% and retinal incarceration in 1% . Huebner, who drained 89% of cases, found intraocular hemorrhages in 6.9% and retinal incarceration in 0.7% [3o].Also in 1975, Spalter reported iatrogenic retinal holes related to drainage that had occurred in 2.3-14.8%, often accompanied by vitreous loss, depending on the technique used .
Improvements in the technique of drainage included transillumination of the choroid to identify large vessels, diathermy , puncturing away from vortices and long posterior ciliary vessels , using the microscope , using traction , or incomplete drainage .
All of the reports on drainage and its complications are retrospective. It is hard to imagine a detailed report about the exact sub-macular distribution of blood in the operative note. Yet, as Cibis wryly remarked,"As you all know, surgeons, as a rule, do not report their complications and mistakes unless they are related to a technique devised by another surgeon" . Nevertheless, reports of failures exist, relating failure to complications of drainage in a majority of cases . Underreporting of less than a "major hemorrhage" is likely. Blagojevic, who noted intraocular hemorrhages in 16% wrote: "It is important to stress that [the intraocular hemorrhages] were never widespread, and that they did not unfavorably affect the results of the operation. Hemophthalmus and choroidal hematoma were not noticed" . There have been many modifications of the drainage technique [27-34], attesting to the difficulty of producing a bloodless perforating injury in a highly perfused, inflamed and hypotonous vascular layer. Added risks over the past seven decades have been increasing patient age and widespread use of anticoagulants. Possibly, poor visual acuity found after "scleral buckling" might be related to underreported complications of drainage and layers of barely visible subretinal blood under the fovea (Fig. 3.5).
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