942
AMERICAN JOURNAL OF OPHTHALMOLOGY
Tying the posterior ends of the sutures anteriorly avoids the problem of tying sutures posteriorly. This procedure is made easier in vitrectomized eyes with a pars plana infusion line in which intraoc ular pressure can be decreased to achieve greater visualization of the posterior sclera. A single arm 4-0 or 5-0 Dacron suture on a spatula needle is used. Two scleral bites are made in the anteroposterior di rection (Figure). Since the mattress suture is being placed posterior to the equator, the curve of the needle is opposite the curve of the globe, thus reducing the chances of the needle penetrating the globe. After the second scleral bite, the needle is removed, and the two posterior ends of the suture are brought forward and tied together. An appropriately sized Lincoff silicone sponge is now slipped beneath the posterior loop of the mattress suture and the anterior ends of the suture are tied snugly over the top of the silicone sponge.
NOVEMBER, 1979 SUMMARY
We devised a method for safely placing mattress sutures for radial scleral buck ling of posterior retinal holes. The ability to pass the needle in the anteroposterior direction, as well as the ability to tie the posterior ends of the mattress suture an teriorly where they are easily accessible, makes this method of placing the mattress suture safe and effective for posterior ra dial buckles. REFERENCES 1. Joondeph, H. C , and Goldberg, M. F.: Rhegmatogenous retinal detachment after tributary reti nal vein occlusion. Am. J. Ophthalmol. 80:253, 1975. 2. McMeel, J. W.: Discussion of treatment and techniques of photocoagulation. In Goldberg, M. F., and Fine, S. L. (eds.): Symposium on the Treatment of Diabetic Retinopathy, bulletin 1890. Public Health Service, 1969, p p . 623-653. 3. Machemer, R.: A new concept for vitreous surgery. 2. Surgical techniques and complications. Am. J. Ophthalmol. 74:1022, 1972. 4. Machemer, R., and Laqua, H.: A logical ap proach to the treatment of massive periretinal prolif eration. Trans. Am. Acad. Ophthalmol. Otolaryngol. 85:584, 1978. 5. Michels, R. G.: Vitrectomy for the complica tions of diabetic retinopathy. Arch. Ophthalmol. 96:237, 1978.
A NEW TYPE OF CORNEAL ELECTRODE
FOR ELECTRORETINOGRAPHY P. G I L B E R T N I E L S E N , Odense,
Figure (Scott and Stern). A single arm suture is passed in the anteroposterior direction (a,b). After the second scleral bite, the needle is removed (c), and the posterior ends of the suture are brought anteriorly and tied together (d). A silicone sponge is slipped beneath the posterior loop of the mattress suture, and the anterior ends of the suture tied snugly over the top of the silicone sponge (e,f).
M.D.
Denmark
The contact lens-type of corneal elec trodes most commonly used for electroretinograms can be cumbersome in clinical applications, and they often cause the patient discomfort. To reduce these dis advantages I designed a new type of corFrom the Department of Ophthalmology, Univer sity Hospital, DK-5000 Odense C, Denmark. Reprint requests to P. Gilbert Nielsen, M.D., Department of Ophthalmology, University Hospi tal, DK-5000 Odense C, Denmark.
VOL. 88, NO. 5
943
NOTES, CASES, INSTRUMENTS
neal electrode* based on the criteria that it could be used conveniently and posi tioned readily on the cornea. The result is an electrode that has proved useful in adults as well as in children. It is easy to position and remove, causes little discom fort to the patient, and gives excellent recordings. The electrode is made of methacrylate mounted with two small gold plates tilted to fit the corneal cur vature (Figure). Coating the electrode eliminates the photovoltaic artifact that is generated when bright light illuminates exposed metal of recording electrodes, thus making it suitable for bright flash electroretinography (ERG) and early re ceptor potentials. Because the optics of the eye are unaffected by the electrode, it is also possible to obtain focal ERGs that require sharp imagery and a minimum of scattered light. *Available from Brd. Rasmussen, Bondovej 11, DK-5250 Odense, Denmark.
SUMMARY
I designed a new corneal electrode that is easy to position and remove, causes the patient little discomfort, and gives excel lent recordings.
STREAKS (SCHLIEREN) AS A SIGN OF RHEGMATOGENOUS D E T A C H M E N T IN VITREOUS SURGERY T H O M A S R. F R I B E R G , M.D., YASTJO T A N O , M.D., AND R O B E R T M A C H E M E R , M.D. Durham, North
Carolina
Schlieren are streaks created in trans parent media by regions of varying refrac tion. 1 In gasses, schlieren are produced by density gradients, a phenomenon es pecially useful in wind tunnel testing. 2 Familiar schlieren are the heat waves seen over the surface of a darkly painted automobile parked in the hot sun in stag nant air. The heat waves are the result of local differences in air density near the warm surface. Alternatively, schlieren can be observed as light passes through incompletely mixed liquids with differ ent refractive indices, such as alcohol and water. Fluids having different densities typically have different refractive indices and cause streaking of the transmitted light. It is therefore not surprising to observe schlieren during intraocular sur gery. During vitrectomy, the vitreous humor is replaced with an aqueous solution. If a
Figure (Nielsen). Electrode made of methacrylate mounted with two small gold plates tilted to fit the corneal curvature.
From the Duke University Eye Center, Durham, North Carolina. This study was supported by Public Health Research Grant Nos. EY-00841 and EY-2903, and a Research to Prevent Blindness, Inc., Award, New York. Dr. Friberg was a Heed Foundation Fellow (1978-1979). Reprint requests to Robert Machemer, M.D., Duke University Eye Center, P.O. Box 3802, Durham, NC 27710.
AMERICAN JOURNAL OF OPHTHALMOLOGY
Tying the posterior ends of the sutures anteriorly avoids the problem of tying sutures posteriorly. This procedure is made easier in vitrectomized eyes with a pars plana infusion line in which intraoc ular pressure can be decreased to achieve greater visualization of the posterior sclera. A single arm 4-0 or 5-0 Dacron suture on a spatula needle is used. Two scleral bites are made in the anteroposterior di rection (Figure). Since the mattress suture is being placed posterior to the equator, the curve of the needle is opposite the curve of the globe, thus reducing the chances of the needle penetrating the globe. After the second scleral bite, the needle is removed, and the two posterior ends of the suture are brought forward and tied together. An appropriately sized Lincoff silicone sponge is now slipped beneath the posterior loop of the mattress suture and the anterior ends of the suture are tied snugly over the top of the silicone sponge.
NOVEMBER, 1979 SUMMARY
We devised a method for safely placing mattress sutures for radial scleral buck ling of posterior retinal holes. The ability to pass the needle in the anteroposterior direction, as well as the ability to tie the posterior ends of the mattress suture an teriorly where they are easily accessible, makes this method of placing the mattress suture safe and effective for posterior ra dial buckles. REFERENCES 1. Joondeph, H. C , and Goldberg, M. F.: Rhegmatogenous retinal detachment after tributary reti nal vein occlusion. Am. J. Ophthalmol. 80:253, 1975. 2. McMeel, J. W.: Discussion of treatment and techniques of photocoagulation. In Goldberg, M. F., and Fine, S. L. (eds.): Symposium on the Treatment of Diabetic Retinopathy, bulletin 1890. Public Health Service, 1969, p p . 623-653. 3. Machemer, R.: A new concept for vitreous surgery. 2. Surgical techniques and complications. Am. J. Ophthalmol. 74:1022, 1972. 4. Machemer, R., and Laqua, H.: A logical ap proach to the treatment of massive periretinal prolif eration. Trans. Am. Acad. Ophthalmol. Otolaryngol. 85:584, 1978. 5. Michels, R. G.: Vitrectomy for the complica tions of diabetic retinopathy. Arch. Ophthalmol. 96:237, 1978.
A NEW TYPE OF CORNEAL ELECTRODE
FOR ELECTRORETINOGRAPHY P. G I L B E R T N I E L S E N , Odense,
Figure (Scott and Stern). A single arm suture is passed in the anteroposterior direction (a,b). After the second scleral bite, the needle is removed (c), and the posterior ends of the suture are brought anteriorly and tied together (d). A silicone sponge is slipped beneath the posterior loop of the mattress suture, and the anterior ends of the suture tied snugly over the top of the silicone sponge (e,f).
M.D.
Denmark
The contact lens-type of corneal elec trodes most commonly used for electroretinograms can be cumbersome in clinical applications, and they often cause the patient discomfort. To reduce these dis advantages I designed a new type of corFrom the Department of Ophthalmology, Univer sity Hospital, DK-5000 Odense C, Denmark. Reprint requests to P. Gilbert Nielsen, M.D., Department of Ophthalmology, University Hospi tal, DK-5000 Odense C, Denmark.
VOL. 88, NO. 5
943
NOTES, CASES, INSTRUMENTS
neal electrode* based on the criteria that it could be used conveniently and posi tioned readily on the cornea. The result is an electrode that has proved useful in adults as well as in children. It is easy to position and remove, causes little discom fort to the patient, and gives excellent recordings. The electrode is made of methacrylate mounted with two small gold plates tilted to fit the corneal cur vature (Figure). Coating the electrode eliminates the photovoltaic artifact that is generated when bright light illuminates exposed metal of recording electrodes, thus making it suitable for bright flash electroretinography (ERG) and early re ceptor potentials. Because the optics of the eye are unaffected by the electrode, it is also possible to obtain focal ERGs that require sharp imagery and a minimum of scattered light. *Available from Brd. Rasmussen, Bondovej 11, DK-5250 Odense, Denmark.
SUMMARY
I designed a new corneal electrode that is easy to position and remove, causes the patient little discomfort, and gives excel lent recordings.
STREAKS (SCHLIEREN) AS A SIGN OF RHEGMATOGENOUS D E T A C H M E N T IN VITREOUS SURGERY T H O M A S R. F R I B E R G , M.D., YASTJO T A N O , M.D., AND R O B E R T M A C H E M E R , M.D. Durham, North
Carolina
Schlieren are streaks created in trans parent media by regions of varying refrac tion. 1 In gasses, schlieren are produced by density gradients, a phenomenon es pecially useful in wind tunnel testing. 2 Familiar schlieren are the heat waves seen over the surface of a darkly painted automobile parked in the hot sun in stag nant air. The heat waves are the result of local differences in air density near the warm surface. Alternatively, schlieren can be observed as light passes through incompletely mixed liquids with differ ent refractive indices, such as alcohol and water. Fluids having different densities typically have different refractive indices and cause streaking of the transmitted light. It is therefore not surprising to observe schlieren during intraocular sur gery. During vitrectomy, the vitreous humor is replaced with an aqueous solution. If a
Figure (Nielsen). Electrode made of methacrylate mounted with two small gold plates tilted to fit the corneal curvature.
From the Duke University Eye Center, Durham, North Carolina. This study was supported by Public Health Research Grant Nos. EY-00841 and EY-2903, and a Research to Prevent Blindness, Inc., Award, New York. Dr. Friberg was a Heed Foundation Fellow (1978-1979). Reprint requests to Robert Machemer, M.D., Duke University Eye Center, P.O. Box 3802, Durham, NC 27710.
