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Ocular Effect of Neodymium-YAG Laser: Reply
Vol. 99, No.3
in (probably all) normal rabbit corneal endothelium. Of the many hundreds examined in our laboratory by light microscopy in silver-"stained" flat mounts (prepared by the technique used in the article) or by specular microscopy in vivo and in vitro, none has been found wanting in giant cells regardless of the animal's age (3 months to 9 years), sex, or breed. Because of doubts of the normality of the giant cells and suspicion that they resulted from subclinical "infection" in our animal house, we sought them in rabbits elsewhere, including the wild population of the United Kingdom and laboratory specimens in the United States and Australia; giant cells were found in every eye examined. From unpublished observations it seems that the number, distribution, size, and shape of giant cells vary and are unrelated to the rabbit's age, sex, or breed. They almost always occur in dissociated groups as shown in Khodadoust and associates' Figure 2. A given giant cell retains its shape and size for at least one year (shown by repeated specular photomicrography in a single young adult rabbit). The cause and significance of the giant cells are unknown, but as they occur in 3-month-old rabbits (the youngest we have examined) they may represent a developmental anomaly, incomplete mitosis, or fusion of cells. Apart from their multiple nuclei (which vary in number from three to, usually, eight) giant cells show no unusual features by light or scanning electron microscopy. Transmission electron microscopy has not been done. A search through the corneal endothelium of 32 mammalian species disclosed that binucleate corneal endothelial cells occur in many, including hu-
Fig. 2 (Sherrard and Kerr Muir). Light micrograph of silver-"stained" rabbit corneal endothelium.
Correspondence
369
mans, but multinucleate giants were found additionally in the Reeves muntjac (Muntiacus reeves) and gaur (Bas gaurus) only. Examples of giant cells in rabbit corneal endothelium are shown in Figures 1 and 2. EMIL S. SHERRARD, PH.D. MALCOLM G. KERR MUIR, M.R.C.P., F.R.C.S.
London, England
_ _ _ _ _ _ _ Reply
_
EDITOR:
We thank Drs. Sherrard and Kerr Muir for their comments on our paper. Based on our experience on hundreds of flat endothelial preparations on rabbits and humans, we agree with their observation on the presence of multinucleated endothelial cells in normal rabbits as well as in humans. In our experiments with the YAG laser, we routinely used the contralateral eye as the control; the number and distribution of multinucleated endothelial cells in the cornea exposed to the YAG laser did correspond with the area of the cornea exposed to the laser, and were different from those in the controlled eye. The mechanism of formation of multinucleated endothelial cells in these experiments is not known; however, the theory of intensity distribution of laser beam in an optical system proposed by Evans and Morgan! plus the electromagnetic field stress may explain this phenomenon. Evaluating the intensity distribution of focused laser in biomedical material, Evans and Morgan' computed the intensity of beam in and at the vicinity of focal points of an optical system. They showed that the distribution of laser is complex, and areas of axial and off-axial intensity in a given optical system and its aberration will change the intensity distribution of laser beam asymmetrically on either side of the gaussian image point for a distance of several millimeters along the optical axis. Intense laser beam produces an electric field upon electrons and ions of material proportional to the intensity of radiation.! Living cells, particularly the cell membrane, maintain an electrical potential because of active K + and Na + gradient. Coster and Zimmerman" showed that once the electrical stress induced by the laser beam exceeds the limit of the living cell, it leads to breakdown of cell membrane. ALI A. KHODADOUST, DEAN F. ARKFELD, JOSEPH CAPRIOLI, MARVIN L. SEARS,
M.D. M.D. M.D. M.D.
New Haven, Connecticut
370
March, 1985
AMERICAN JOURNAL OF OPHTHALMOLOGY
References 1. Evans, L. R., and Morgan, C. G.: Intensity distribution of focused laser beams in bio-medical studies. Phys. Med. BioI. 14:205, 1969. 2. Taboada, J., and Ebbers, W. R.: Ocular tissue damage due to ultrashort 1060 nm light pulses from a mode-locked Nd: glass laser. Appl. Opt. 14:1759, 1975. 3. Coster, H. G. 1., and Zimmerman, U.: The mechanism of electrical breakdown in the membranes of valonia utriculanis. J. Membr. BioI. 22:73, 1975.
Biofeedback Therapy of Essential Blepharospasm
was first imputed to him by Banister" in 1932. Pulfrich used a hand-driven reciprocating device and, with his son's help, produced a theoretical background to his observers' data, which, contrary to Banister's opinion, was soundly based on the physiologic ideas prevalent at the time, although the underlying algebra has since been modified.! The results observed by Tredici and von Noorden are noteworthy in that they demonstrated a Pulfrich effect when one might have expected it, that is, when foveal and nonfoveal stimuli are combined. I suspect that, as long as fusion takes place, for which function it is an unsurpassed test, it fulfills a useful diagnostic role. Moreover, the spontaneous Pulfrich effect is easily quantified, for example, in terms of the neutral density (in front of the leading eye) required to eliminate the phenomenon. PROFESSOR R. A. WEALE
EDITOR:
I read with interest the article, "Biofeedback therapy of essential blepharospasm" (Am. J. Ophthalmol. 98:28, July 1984), by R. S. Surwit and M. Rotberg. Being familiar with how almost any type of treatment gives transient relief of blepharospasm, I was disappointed that there was no discussion of careful follow-up for these patients. There is merely a statement that, "Informal followup visits have confirmed that these improvements are durable over a six-month period." This does not say how many patients were followed up and for what intervals, nor do I know what the authors mean by "informal follow-up." For any treatment of blepharospasm to be considered efficacious, data on proper follow-up are essential. I hope the authors can provide this so that the efficacy of their use of biofeedback can be assessed. BARTLEY R. FRUEH, M.D.
Ann Arbor, Michigan
The Pulfrich Effect In Anisometropic Amblyopia and Strabismus EDITOR:
The interesting article by T. D. Tredici and G. K. von Noorden (Am. J. Ophthalmol. 98:499, Oct. 1984) is introduced by what appears to be a historical error: I hope the authors will forgive me if I comment on it. They say "Pulfrich noted that a pendulum oscillating in a frontal plane and viewed binocularly with a filter over one eye appeared to move in an ellipse."! However, he cannot have noted anything of the sort, because he was oneeyed. Moreover, he did not mention any pendulum. As far as I have been able to discover, this
London, England
References 1. Pulfrich, c.: Die Stereoskopie im Dienste der isochromen und heterochromen Photometrie. Naturwissenschaften 10:553, 1922. 2. Banister, H.: Retinal traction time. In Report of a Joint Discussion on Vision. London, Physical Society, 1932, pp. 227-234. 3. Weale, R. A.: Theory of the Pulfrich effect. aphtha1mologica 128:380, 1954.
_ _ _ _ _ _ _ Reply
_
EDITOR:
We were aware that Carl Pulfrich injured his left eye in childhood, 1 and therefore never actually observed the stereoscopic illusion that bears his name. It is of interest that the portrait of Pulfrich in the archives of the Carl Zeiss Company, for whom he worked for many years, shows him to have had an exotropia of the left eye. We wish to thank Professor Weale for informing us that Banister first suggested to Pulfrich that a pendulum could be used to illustrate his stereoscopic principle. Much of the literature on the Pulfrich effect is unclear on this historical point. TOMAS D. TREDIel, M.D. GUNTER K. VON NOORPEN, M.D.
Houston, Texas
Reference 1. Schneider, F.: Carl Pulfrich. Prof. Dr. Carl Pulfrich zu seinem 100. Geburstag am 24. September 1958. Jenaer Rundschau 3:127, 1958.
in (probably all) normal rabbit corneal endothelium. Of the many hundreds examined in our laboratory by light microscopy in silver-"stained" flat mounts (prepared by the technique used in the article) or by specular microscopy in vivo and in vitro, none has been found wanting in giant cells regardless of the animal's age (3 months to 9 years), sex, or breed. Because of doubts of the normality of the giant cells and suspicion that they resulted from subclinical "infection" in our animal house, we sought them in rabbits elsewhere, including the wild population of the United Kingdom and laboratory specimens in the United States and Australia; giant cells were found in every eye examined. From unpublished observations it seems that the number, distribution, size, and shape of giant cells vary and are unrelated to the rabbit's age, sex, or breed. They almost always occur in dissociated groups as shown in Khodadoust and associates' Figure 2. A given giant cell retains its shape and size for at least one year (shown by repeated specular photomicrography in a single young adult rabbit). The cause and significance of the giant cells are unknown, but as they occur in 3-month-old rabbits (the youngest we have examined) they may represent a developmental anomaly, incomplete mitosis, or fusion of cells. Apart from their multiple nuclei (which vary in number from three to, usually, eight) giant cells show no unusual features by light or scanning electron microscopy. Transmission electron microscopy has not been done. A search through the corneal endothelium of 32 mammalian species disclosed that binucleate corneal endothelial cells occur in many, including hu-
Fig. 2 (Sherrard and Kerr Muir). Light micrograph of silver-"stained" rabbit corneal endothelium.
Correspondence
369
mans, but multinucleate giants were found additionally in the Reeves muntjac (Muntiacus reeves) and gaur (Bas gaurus) only. Examples of giant cells in rabbit corneal endothelium are shown in Figures 1 and 2. EMIL S. SHERRARD, PH.D. MALCOLM G. KERR MUIR, M.R.C.P., F.R.C.S.
London, England
_ _ _ _ _ _ _ Reply
_
EDITOR:
We thank Drs. Sherrard and Kerr Muir for their comments on our paper. Based on our experience on hundreds of flat endothelial preparations on rabbits and humans, we agree with their observation on the presence of multinucleated endothelial cells in normal rabbits as well as in humans. In our experiments with the YAG laser, we routinely used the contralateral eye as the control; the number and distribution of multinucleated endothelial cells in the cornea exposed to the YAG laser did correspond with the area of the cornea exposed to the laser, and were different from those in the controlled eye. The mechanism of formation of multinucleated endothelial cells in these experiments is not known; however, the theory of intensity distribution of laser beam in an optical system proposed by Evans and Morgan! plus the electromagnetic field stress may explain this phenomenon. Evaluating the intensity distribution of focused laser in biomedical material, Evans and Morgan' computed the intensity of beam in and at the vicinity of focal points of an optical system. They showed that the distribution of laser is complex, and areas of axial and off-axial intensity in a given optical system and its aberration will change the intensity distribution of laser beam asymmetrically on either side of the gaussian image point for a distance of several millimeters along the optical axis. Intense laser beam produces an electric field upon electrons and ions of material proportional to the intensity of radiation.! Living cells, particularly the cell membrane, maintain an electrical potential because of active K + and Na + gradient. Coster and Zimmerman" showed that once the electrical stress induced by the laser beam exceeds the limit of the living cell, it leads to breakdown of cell membrane. ALI A. KHODADOUST, DEAN F. ARKFELD, JOSEPH CAPRIOLI, MARVIN L. SEARS,
M.D. M.D. M.D. M.D.
New Haven, Connecticut
370
March, 1985
AMERICAN JOURNAL OF OPHTHALMOLOGY
References 1. Evans, L. R., and Morgan, C. G.: Intensity distribution of focused laser beams in bio-medical studies. Phys. Med. BioI. 14:205, 1969. 2. Taboada, J., and Ebbers, W. R.: Ocular tissue damage due to ultrashort 1060 nm light pulses from a mode-locked Nd: glass laser. Appl. Opt. 14:1759, 1975. 3. Coster, H. G. 1., and Zimmerman, U.: The mechanism of electrical breakdown in the membranes of valonia utriculanis. J. Membr. BioI. 22:73, 1975.
Biofeedback Therapy of Essential Blepharospasm
was first imputed to him by Banister" in 1932. Pulfrich used a hand-driven reciprocating device and, with his son's help, produced a theoretical background to his observers' data, which, contrary to Banister's opinion, was soundly based on the physiologic ideas prevalent at the time, although the underlying algebra has since been modified.! The results observed by Tredici and von Noorden are noteworthy in that they demonstrated a Pulfrich effect when one might have expected it, that is, when foveal and nonfoveal stimuli are combined. I suspect that, as long as fusion takes place, for which function it is an unsurpassed test, it fulfills a useful diagnostic role. Moreover, the spontaneous Pulfrich effect is easily quantified, for example, in terms of the neutral density (in front of the leading eye) required to eliminate the phenomenon. PROFESSOR R. A. WEALE
EDITOR:
I read with interest the article, "Biofeedback therapy of essential blepharospasm" (Am. J. Ophthalmol. 98:28, July 1984), by R. S. Surwit and M. Rotberg. Being familiar with how almost any type of treatment gives transient relief of blepharospasm, I was disappointed that there was no discussion of careful follow-up for these patients. There is merely a statement that, "Informal followup visits have confirmed that these improvements are durable over a six-month period." This does not say how many patients were followed up and for what intervals, nor do I know what the authors mean by "informal follow-up." For any treatment of blepharospasm to be considered efficacious, data on proper follow-up are essential. I hope the authors can provide this so that the efficacy of their use of biofeedback can be assessed. BARTLEY R. FRUEH, M.D.
Ann Arbor, Michigan
The Pulfrich Effect In Anisometropic Amblyopia and Strabismus EDITOR:
The interesting article by T. D. Tredici and G. K. von Noorden (Am. J. Ophthalmol. 98:499, Oct. 1984) is introduced by what appears to be a historical error: I hope the authors will forgive me if I comment on it. They say "Pulfrich noted that a pendulum oscillating in a frontal plane and viewed binocularly with a filter over one eye appeared to move in an ellipse."! However, he cannot have noted anything of the sort, because he was oneeyed. Moreover, he did not mention any pendulum. As far as I have been able to discover, this
London, England
References 1. Pulfrich, c.: Die Stereoskopie im Dienste der isochromen und heterochromen Photometrie. Naturwissenschaften 10:553, 1922. 2. Banister, H.: Retinal traction time. In Report of a Joint Discussion on Vision. London, Physical Society, 1932, pp. 227-234. 3. Weale, R. A.: Theory of the Pulfrich effect. aphtha1mologica 128:380, 1954.
_ _ _ _ _ _ _ Reply
_
EDITOR:
We were aware that Carl Pulfrich injured his left eye in childhood, 1 and therefore never actually observed the stereoscopic illusion that bears his name. It is of interest that the portrait of Pulfrich in the archives of the Carl Zeiss Company, for whom he worked for many years, shows him to have had an exotropia of the left eye. We wish to thank Professor Weale for informing us that Banister first suggested to Pulfrich that a pendulum could be used to illustrate his stereoscopic principle. Much of the literature on the Pulfrich effect is unclear on this historical point. TOMAS D. TREDIel, M.D. GUNTER K. VON NOORPEN, M.D.
Houston, Texas
Reference 1. Schneider, F.: Carl Pulfrich. Prof. Dr. Carl Pulfrich zu seinem 100. Geburstag am 24. September 1958. Jenaer Rundschau 3:127, 1958.