Increased endothelial cell density in the paracentral and peripheral regions of the human cornea
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investigations for hemphagocytic lymphohistiocytosis. In none of our cases was there systemic or retinal signs that would suggest that such an investigation was indicated. Glutaric aciduria is another rare cause of retinal hem- orrhage and subdural hemorrhage. However, these chil- dren usually present in a fashion very different than SBS. They have a history of macrocrania, an acute crisis with CT scan showing involvement of the extraprymidal sys- tem, and extraprymidal signs on recovery. A review of the world’s literature, as well as nonreported cases, reveals not a single case in which a child had more than a few intraretinal or preretinal hemorrhages confined to the posterior pole of the retina in the absence of concurrent evidence of SBS. 1 Almost two-thirds of the children reported in our study had severe multilayered retinal hemorrhages extending to the ora serrata, and approxi- mately one-third had macular retinoschisis, a picture never reported in glutaric aciduria. At our institution, investiga- tions for glutaric aciduria are only carried out when a patient has systemic and retinal findings, that might suggest an overlap diagnosis. Some of our children were investigated for this disorder, and none was found to be affected. The cause of death for the children in our study was the secondary effect of their abusive head injury in particular, severe cerebral edema, and absence of cerebral profusion. Doctor Raj’s letter serves as a reminder of the impor- tance of careful attention to the terminology used when describing retinal hemorrhages, including number, type, patterns, extent, and location of the hemorrhages. 1 In addition, equal attention must be paid to the systemic findings, which may or may not suggest a differential diagnosis that requires exploration. ALEX V. LEVIN, MD, MHSC, FRCSC YAIR MORAD, MD YURI M. KIM, MD DEREK ARMSTRONG, MD DIRK HUYER, MD, FRCPC MARCELLINA MIAN, MD, FRCPC Toronto, Ontario, Canada REFERENCE 1. Levin AV. Retinal haemorrhage and child abuse. In: David TJ, editor. Recent Advances in Paediatrics, no 18. London: Churchill Livingstone, 2000:151–219. Increased Endothelial Cell Density in the Paracentral and Peripheral Regions of the Human Cornea EDITOR: THE ARTICLE BY AMANN AND ASSOCIATES (AM J OPHTHAL- mol 2003;135:584 –590) on the increased endothelial cell density in the paracentral and peripheral regions of the human cornea is a very thought-provoking and nice piece of work, and we sincerely convey our heartiest congratu- lations to all the authors. The authors have noted an increase in the endothelial cell density in the paracentral and peripheral regions of the cornea compared with the central region. The human endothelium is a single cell layer and is approximately 3 m thick. 1 It would be interesting to hypothesize that a relatively fewer number of endothelial cells in the central cornea might in some way account for the maximum transparency for the central cornea. Another important finding in their study was that the superior peripheral region of the corneal endothelium was found to have the largest endothelial cell density. It would be interesting to know whether a temporal clear corneal incision would be less damaging than the top incision with respect to relative loss of endothelial cells during phaco- emulsification cataract surgeries. It is heartening to know that it is not only the increase in the numbers of endothelial cells in the periphery 2 but also the special characteristics they possess, such as the telomerase activity. The presence of telomerase activity could indeed point toward their totipotent potential as stem cells. It would be good work for the researchers in the future to harness these potential progenitor cells to treat conditions such as endothelial dystrophy, primary corneal graft failures, and so on. AKASH RAJ, MD, DRCOPHTH (LONDON), FRCS Essex, England RAFIK ABDEL M. GIRGIS, FRCS Hull, England REFERENCES 1. Richard A. Farrell. Corneal transparency: principles and practice of ophthalmology (basic sciences). Albert DM, Jako- biec FA, editors. Principles and practice of ophthalmology. Philadelphia: WB Saunders, 1994:68. 2. Daus W, Voelker HE, Meysen H, Bundschuh W. Vitalfaer- bung der Hornhautendothels-erweiterte Moeglichkeitein der Diagnostik. Fortschr Ophthalmol 1989;86:259 –264. AUTHOR REPLY WE THANK DRS. RAJ AND GIRGIS FOR THEIR THOUGHTFUL comments about our manuscript on increased endothelial cell density in the paracentral and peripheral regions of the human cornea. In response to the first query about the potential of fewer central corneal endothelial cells ac- counting for maximum transparency in the central cornea, the endothelial cells have a thickness of 3 m to 5 m, they are thin, and the change in refractive index between the endothelial cells and aqueous humor would be minimal AMERICAN JOURNAL OF OPHTHALMOLOGY 774 OCTOBER 2003
Transcript of Increased endothelial cell density in the paracentral and peripheral regions of the human cornea
investigations for hemphagocytic lymphohistiocytosis. Innone of our cases was there systemic or retinal signs thatwould suggest that such an investigation was indicated.
Glutaric aciduria is another rare cause of retinal hem-orrhage and subdural hemorrhage. However, these chil-dren usually present in a fashion very different than SBS.They have a history of macrocrania, an acute crisis withCT scan showing involvement of the extraprymidal sys-tem, and extraprymidal signs on recovery. A review of theworld’s literature, as well as nonreported cases, reveals nota single case in which a child had more than a fewintraretinal or preretinal hemorrhages confined to theposterior pole of the retina in the absence of concurrentevidence of SBS.1 Almost two-thirds of the childrenreported in our study had severe multilayered retinalhemorrhages extending to the ora serrata, and approxi-mately one-third had macular retinoschisis, a picture neverreported in glutaric aciduria. At our institution, investiga-tions for glutaric aciduria are only carried out when apatient has systemic and retinal findings, that mightsuggest an overlap diagnosis. Some of our children wereinvestigated for this disorder, and none was found to beaffected.
The cause of death for the children in our study was thesecondary effect of their abusive head injury in particular,severe cerebral edema, and absence of cerebral profusion.
Doctor Raj’s letter serves as a reminder of the impor-tance of careful attention to the terminology used whendescribing retinal hemorrhages, including number, type,patterns, extent, and location of the hemorrhages.1 Inaddition, equal attention must be paid to the systemicfindings, which may or may not suggest a differentialdiagnosis that requires exploration.
ALEX V. LEVIN, MD, MHSC, FRCSC
YAIR MORAD, MD
YURI M. KIM, MD
DEREK ARMSTRONG, MD
DIRK HUYER, MD, FRCPC
MARCELLINA MIAN, MD, FRCPC
Toronto, Ontario, Canada
REFERENCE
1. Levin AV. Retinal haemorrhage and child abuse. In: DavidTJ, editor. Recent Advances in Paediatrics, no 18. London:Churchill Livingstone, 2000:151–219.
Increased Endothelial Cell Density inthe Paracentral and PeripheralRegions of the Human Cornea
EDITOR:
THE ARTICLE BY AMANN AND ASSOCIATES (AM J OPHTHAL-
mol 2003;135:584–590) on the increased endothelial cell
density in the paracentral and peripheral regions of thehuman cornea is a very thought-provoking and nice pieceof work, and we sincerely convey our heartiest congratu-lations to all the authors. The authors have noted anincrease in the endothelial cell density in the paracentraland peripheral regions of the cornea compared with thecentral region. The human endothelium is a single celllayer and is approximately 3 �m thick.1 It would beinteresting to hypothesize that a relatively fewer number ofendothelial cells in the central cornea might in some wayaccount for the maximum transparency for the centralcornea.
Another important finding in their study was that thesuperior peripheral region of the corneal endothelium wasfound to have the largest endothelial cell density. It wouldbe interesting to know whether a temporal clear cornealincision would be less damaging than the top incision withrespect to relative loss of endothelial cells during phaco-emulsification cataract surgeries.
It is heartening to know that it is not only the increasein the numbers of endothelial cells in the periphery2 butalso the special characteristics they possess, such as thetelomerase activity. The presence of telomerase activitycould indeed point toward their totipotent potential asstem cells. It would be good work for the researchers in thefuture to harness these potential progenitor cells to treatconditions such as endothelial dystrophy, primary cornealgraft failures, and so on.
AKASH RAJ, MD, DRCOPHTH (LONDON), FRCS
Essex, EnglandRAFIK ABDEL M. GIRGIS, FRCS
Hull, England
REFERENCES
1. Richard A. Farrell. Corneal transparency: principles andpractice of ophthalmology (basic sciences). Albert DM, Jako-biec FA, editors. Principles and practice of ophthalmology.Philadelphia: WB Saunders, 1994:68.
2. Daus W, Voelker HE, Meysen H, Bundschuh W. Vitalfaer-bung der Hornhautendothels-erweiterte Moeglichkeitein derDiagnostik. Fortschr Ophthalmol 1989;86:259–264.
AUTHOR REPLY
WE THANK DRS. RAJ AND GIRGIS FOR THEIR THOUGHTFUL
comments about our manuscript on increased endothelialcell density in the paracentral and peripheral regions of thehuman cornea. In response to the first query about thepotential of fewer central corneal endothelial cells ac-counting for maximum transparency in the central cornea,the endothelial cells have a thickness of 3 �m to 5 �m,they are thin, and the change in refractive index betweenthe endothelial cells and aqueous humor would be minimal
AMERICAN JOURNAL OF OPHTHALMOLOGY774 OCTOBER 2003
