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Dosage of intravitreal triamcinolone
Some believe, nevertheless, that there are two disadvantages of indirect ophthalmoscopy for vitreous surgery: (1) the inverted image, as Landers and associates indicated, and (2) the one-handed restriction for intraocular manipulations. Most vitreal-retinal physicians learn to unconsciously transpose the inverted image. And as far as the one-handed limitation is concerned, the great majority of surgical cases do not require an opposite tug with the fellow hand. Difficulty with the indirect ophthalmoscopic vitrectomy technique is not so much a matter of the inverted image, as the authors suggest, but more the result of surgeon ineptitude. Fortunately, inadequacy can be overcome with diligence and patience, and the technique can be used to great advantage for all types of vitreous surgery.2 The surgical technique proposed by Landers and associates, conversely, does not depend so much on diligence of the surgeon. Indeed, the system is flawed (and hazardous) because of the flattened image. Pomerantzeff,3 an optical engineer, noted long ago, and in obvious reference to experiments performed by H. von Helmholtz,4 that the sensation of depth, or stereopsis, is consistently translated by a change in relief within the orthoscopic zone.
most vitreoretinal surgeons currently use a flat or slightly convex lens placed directly on the cornea. Doctor Hawkins also discusses the virtues of the indirect ophthalmoscope viewing system for vitreous surgery. We agree that this can be a very good approach in the hands of a surgeon experienced in its use. Indirect ophthalmoscopy was widely used to carry out vitrectomy procedures in years past. However, the use of the indirect ophthalmoscope in these cases does not provide direct internal illumination, the magnification is fixed, bimanual surgery is not possible, the position of the surgeon is often cumbersome, the assistant cannot see the surgical procedure well, the teaching is extremely difficult, and simultaneous membrane manipulation can be awkward. In summary, we have presented a new, wide-field, noncontact viewing system for use in vitreoretinal surgery, which is inexpensive and yet provides essentially all of the advantages (and shortcomings, such as they are) of other contemporary operating microscope-mounted noncontact wide-field viewing systems for vitreous surgery.
W. REX HAWKINS, MD
GHOLAM A. PEYMAN, MD
Houston, Texas
New Orleans, Louisiana
MAURICE B. LANDERS, III, MD
Chapel Hill, North Carolina
PAUL WHALEN, BSME
Bellvue, Washington IZAK F. WESSELS, MMED
REFERENCES
Chattanooga, Tennessee
1. Rubin M. The optics of indirect ophthalmoscopy. Surv Ophthalmol 1964;9:449 –464. 2. Scott JD. Surgery of retinal and vitreous diseases. Houston: Butterworth-Heinemann, 1998:90 –92. 3. A new stereoscopic indirect ophthalmoscope. In: McPherson A, editor. New and controversial aspects of retinal detachment. New York: Haeber, 1966:137–147. 4. Southall JP. The optical society of America. von Helmholtz H, editor. H. von Helmholtz’s treatise on physiological optics. Vol III, 1925:367– 400.
VIRGILIO MORALES, MD
Mexico City, Mexico
Dosage of Intravitreal Triamcinolone EDITOR: IN A BRIEF REPORT, JONAS AND ASSOCIATES DESCRIBE THE
use of a high dose of intravitreal triamcinolone acetonide for the treatment of pseudophakic cystoid macular edema (Am J Ophthalmol 136:384 –386, 2003). The authors state that “patients received an intravitreal injection of 25 mg or triamcinolone acetonide transconjunctivally.” They go on to describe in detail the procedure for preparing the injection. It would appear from that description that the actual intravitreal dose of triamcinolone would be between 2.5 mg and 5.0 mg. Could the authors please clarify the actual amount of triamcinolone delivered into the vitreous?
AUTHOR REPLY WE WOULD LIKE TO THANK DR. HAWKINS FOR HIS INTEREST
in our article, and for his comments. While we agree with some of them, we disagree with some others. The transverse magnification of the aerial image is the dioptric power of the eye (60) divided by the power of the condensing lens (132) and is, thus, 0.45 rather than 0.38. The concept of decreasing axial magnification as a function of increasing diopter power (microscope optic and patient eye power staying the same) is correct. At what point this becomes “hazardous” is unknown. During the trial uses of this wide-angle viewing system, all of the surgeons felt that the new system was not especially useful for delicate membrane peeling such as removal of the internal limiting membrane from the area of the macula in a macular hole surgery procedure. For this type of surgery, 1192
AMERICAN JOURNAL
EDMOND H. THALL, MD
Riverton, Wyoming
AUTHOR REPLY THE AUTHORS WOULD LIKE TO THANK DR. THALL FOR HIS
comment and interest in our study.1 Due to the millipore filter, most of the triamcinolone acetonide crystals are kept OF
OPHTHALMOLOGY
DECEMBER 2003
most vitreoretinal surgeons currently use a flat or slightly convex lens placed directly on the cornea. Doctor Hawkins also discusses the virtues of the indirect ophthalmoscope viewing system for vitreous surgery. We agree that this can be a very good approach in the hands of a surgeon experienced in its use. Indirect ophthalmoscopy was widely used to carry out vitrectomy procedures in years past. However, the use of the indirect ophthalmoscope in these cases does not provide direct internal illumination, the magnification is fixed, bimanual surgery is not possible, the position of the surgeon is often cumbersome, the assistant cannot see the surgical procedure well, the teaching is extremely difficult, and simultaneous membrane manipulation can be awkward. In summary, we have presented a new, wide-field, noncontact viewing system for use in vitreoretinal surgery, which is inexpensive and yet provides essentially all of the advantages (and shortcomings, such as they are) of other contemporary operating microscope-mounted noncontact wide-field viewing systems for vitreous surgery.
W. REX HAWKINS, MD
GHOLAM A. PEYMAN, MD
Houston, Texas
New Orleans, Louisiana
MAURICE B. LANDERS, III, MD
Chapel Hill, North Carolina
PAUL WHALEN, BSME
Bellvue, Washington IZAK F. WESSELS, MMED
REFERENCES
Chattanooga, Tennessee
1. Rubin M. The optics of indirect ophthalmoscopy. Surv Ophthalmol 1964;9:449 –464. 2. Scott JD. Surgery of retinal and vitreous diseases. Houston: Butterworth-Heinemann, 1998:90 –92. 3. A new stereoscopic indirect ophthalmoscope. In: McPherson A, editor. New and controversial aspects of retinal detachment. New York: Haeber, 1966:137–147. 4. Southall JP. The optical society of America. von Helmholtz H, editor. H. von Helmholtz’s treatise on physiological optics. Vol III, 1925:367– 400.
VIRGILIO MORALES, MD
Mexico City, Mexico
Dosage of Intravitreal Triamcinolone EDITOR: IN A BRIEF REPORT, JONAS AND ASSOCIATES DESCRIBE THE
use of a high dose of intravitreal triamcinolone acetonide for the treatment of pseudophakic cystoid macular edema (Am J Ophthalmol 136:384 –386, 2003). The authors state that “patients received an intravitreal injection of 25 mg or triamcinolone acetonide transconjunctivally.” They go on to describe in detail the procedure for preparing the injection. It would appear from that description that the actual intravitreal dose of triamcinolone would be between 2.5 mg and 5.0 mg. Could the authors please clarify the actual amount of triamcinolone delivered into the vitreous?
AUTHOR REPLY WE WOULD LIKE TO THANK DR. HAWKINS FOR HIS INTEREST
in our article, and for his comments. While we agree with some of them, we disagree with some others. The transverse magnification of the aerial image is the dioptric power of the eye (60) divided by the power of the condensing lens (132) and is, thus, 0.45 rather than 0.38. The concept of decreasing axial magnification as a function of increasing diopter power (microscope optic and patient eye power staying the same) is correct. At what point this becomes “hazardous” is unknown. During the trial uses of this wide-angle viewing system, all of the surgeons felt that the new system was not especially useful for delicate membrane peeling such as removal of the internal limiting membrane from the area of the macula in a macular hole surgery procedure. For this type of surgery, 1192
AMERICAN JOURNAL
EDMOND H. THALL, MD
Riverton, Wyoming
AUTHOR REPLY THE AUTHORS WOULD LIKE TO THANK DR. THALL FOR HIS
comment and interest in our study.1 Due to the millipore filter, most of the triamcinolone acetonide crystals are kept OF
OPHTHALMOLOGY
DECEMBER 2003