Descemet Membrane Detachment After Canaloplasty
Descemet Membrane Detachment After Canaloplasty
DMD with or without intracorneal hemorrhage is a known complication after cataract surgery. DMD after canaloplasty is a relatively new entity and the incidence has been reported to range from 1% to 6.25%. In our study, the incidence was 7.4%. DMD could be related to excessive amounts of Healon GV injection into the Schlemm canal during the viscodilation portion of the surgery. This explanation may have some truth to it as the primary surgeon (R.S.A.) noticed excessive injection of the Healon GV by inexperienced nursing staff in at least 2 cases. We experienced only 1 case of DMD during the first year followed by 2 to 4 cases/year during the subsequent years using the same technique. It has previously been postulated that there is an increased risk of DMD in canals that have adhesions between the inner and outer wall. Most of the detachments in our series occurred in the inferior quadrants. This could be because of one of 2 reasons. As the Healon GV is injected from the entry point at or near 12 o' clock limbus, the Healon GV may have reached a critical mass in the inferior quadrants leading to the detachment of the Descemet membrane from the Schwalbe line. The intraluminal resistance during the procedure may surpass the strength of the connection between Descemet membrane and Schwalbe line resulting in a detachment of Descemet membrane The other possibility is that there could be an anatomic predisposition or congenital weakness in the inferior quadrants. Palmiero et al reported a case with bilateral inferonasal detachment after canaloplasty and postulated that this may be because of anatomic predisposition. Both these cases resolved without intervention over 3 months. The last possibility could be related to the surgical technique used in the current study. The technique that was used in the study was the same that was previously published. The most likely variable could be the amount of viscoelastic that was injected. The exact amount of the viscoelastic that should be injected into the canal in total and the amount that comes out of the company supplied syringe per quarter turn are unknown and deserve future research.
All but one of our cases resolved without any permanent sequelae. In 58% of our cases (7/12), blood was mixed with Healon GV in the detachment. In 3 of these cases, we chose to drain at the slit lamp because of the presence of significant quantity of blood mixed with Healon GV and the size of the detachment (>3 mm). The DMD resolved completely in 2 of the 3 eyes. One case progressed to corneal decompensation despite air bubble injection into the anterior chamber and drainage of blood. This was an 86-year-old man who developed progressive corneal edema, ultimately needing a PKP.
Limitations of the present study include all the inherent weaknesses of a retrospective study, including possible selection bias and limited patient population. This study analyzed the surgical results of a single surgeon (R.S.A); thus, the results may not be applicable to everyone. Some factors that may have relevance to the present study but were not studied include endothelial cell count and the number of times the viscoelastic was injected in every case.
In conclusion, DMD with or without intracorneal hemorrhage can occur in up to 7% of the patients after canaloplasty. Most cases occur in the inferior quadrants and resolve without any permanent sequelae. Occasionally, DMD can result in central corneal decompensation needing PKP and should be recognized as a potential serious adverse event after canaloplasty.
Discussion
DMD with or without intracorneal hemorrhage is a known complication after cataract surgery. DMD after canaloplasty is a relatively new entity and the incidence has been reported to range from 1% to 6.25%. In our study, the incidence was 7.4%. DMD could be related to excessive amounts of Healon GV injection into the Schlemm canal during the viscodilation portion of the surgery. This explanation may have some truth to it as the primary surgeon (R.S.A.) noticed excessive injection of the Healon GV by inexperienced nursing staff in at least 2 cases. We experienced only 1 case of DMD during the first year followed by 2 to 4 cases/year during the subsequent years using the same technique. It has previously been postulated that there is an increased risk of DMD in canals that have adhesions between the inner and outer wall. Most of the detachments in our series occurred in the inferior quadrants. This could be because of one of 2 reasons. As the Healon GV is injected from the entry point at or near 12 o' clock limbus, the Healon GV may have reached a critical mass in the inferior quadrants leading to the detachment of the Descemet membrane from the Schwalbe line. The intraluminal resistance during the procedure may surpass the strength of the connection between Descemet membrane and Schwalbe line resulting in a detachment of Descemet membrane The other possibility is that there could be an anatomic predisposition or congenital weakness in the inferior quadrants. Palmiero et al reported a case with bilateral inferonasal detachment after canaloplasty and postulated that this may be because of anatomic predisposition. Both these cases resolved without intervention over 3 months. The last possibility could be related to the surgical technique used in the current study. The technique that was used in the study was the same that was previously published. The most likely variable could be the amount of viscoelastic that was injected. The exact amount of the viscoelastic that should be injected into the canal in total and the amount that comes out of the company supplied syringe per quarter turn are unknown and deserve future research.
All but one of our cases resolved without any permanent sequelae. In 58% of our cases (7/12), blood was mixed with Healon GV in the detachment. In 3 of these cases, we chose to drain at the slit lamp because of the presence of significant quantity of blood mixed with Healon GV and the size of the detachment (>3 mm). The DMD resolved completely in 2 of the 3 eyes. One case progressed to corneal decompensation despite air bubble injection into the anterior chamber and drainage of blood. This was an 86-year-old man who developed progressive corneal edema, ultimately needing a PKP.
Limitations of the present study include all the inherent weaknesses of a retrospective study, including possible selection bias and limited patient population. This study analyzed the surgical results of a single surgeon (R.S.A); thus, the results may not be applicable to everyone. Some factors that may have relevance to the present study but were not studied include endothelial cell count and the number of times the viscoelastic was injected in every case.
In conclusion, DMD with or without intracorneal hemorrhage can occur in up to 7% of the patients after canaloplasty. Most cases occur in the inferior quadrants and resolve without any permanent sequelae. Occasionally, DMD can result in central corneal decompensation needing PKP and should be recognized as a potential serious adverse event after canaloplasty.
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