536
AMERICAN JOURNAL OF OPHTHALMOLOGY
muscle has a feathered or "paint brush" appearance. This is caused by the muscle descending out of the scan plane. In con trast, the orbital tumor has a sharp edge. In Graves' disease careful inspection of the scan series almost always reveals ad ditional swollen muscles. Swollen extraocular muscles may be distinguished from optic nerve sheath tumors because the entire length of the optic nerve is seen in another scan plane adjacent to the muscle. The size of normal orbital structures is at the limit of resolution of the standard EMI scanner. Reported improvements which increase resolution aid significant ly in recognizing extraocular muscles. We are calling attention to this matter because we are aware of several patients with swollen extraocular muscles who have had surgery on the basis of a false diagnosis of tumor at the orbital apex. S T E P H E N L. T R O K E L , SADEK K. H I L A L ,
APRIL, 1976
tionist will find that in sphere and cylin der only the 0.12 diopter value is really needed; occasionally the addition of 0.12 diopter sph may help equalize the acuity of the eyes, and sometimes the brightness of the principal axes of the astigmatic dial becomes even with an added 0.12 diopter cyl. Elimination of the rest of the 0.12 diopter series permits a better order of the thicker spheres. The 0.5 diopter gradation could then be extended to 8.5 diopters, 9.5 diopters, 10.5 diopters, 11.5 diopters, and 12.5 diopters. This change would facilitate refraction of both aphakic and highly myopic eyes. The cylinders of 0.37 diopters and 0.62 diopters may well be replaced by the more useful powers of 6.5 and 7.5 diopters. J A M E S E. L E B E N S O H N ,
Chicago,
M.D.
Illinois
M.D. M.D.
New York, New York Improving the Trial Case Editor: The modern precision trial case con tains spherical lenses of 0.12 diopter gra dation up to 1.75 diopters, 0.25 diopter intervals to 4.0 diopters followed by 0.5 diopter steps to 8.0 diopters, 1.0 diopter steps to 14.0 diopters and 2.0 diopter steps to 20.0 diopters. The cylinders are in 0.12 diopter gradation to 0.75 diopters then 0.25 diopter intervals to 3.5 diopters, followed by 0.5 diopter steps to 6.0 diop ters and 1.0 diopter steps to 8.0 diopters. Most ophthalmologists aim for 0.25 diop ter accuracy in sphere and cylinder since it is debatable whether a prescription of greater refinement can be filled reliably. A recent study by D. P. Renaldo, A. H. Keeney, and H. L. Duerson, Jr., "Ion exchange tempering of glass ophthalmic lenses," (Am. J. Ophthalmol. 80:291, 1975), supports this opinion. A perfec
BOOK REVIEWS Vitrectomy: A Pars Plana Approach. By Robert Machemer. Grune and Stratton, New York, 1975. Clothbound, 136 pages, table of contents, index, 87 black and white figures. $14.75 Up to about a decade ago the idea of losing vitreous was anathema to ophthal mic surgeons. Every attempt was made to contain the vitreous within the globe and in the presence of vitreous obscuration by blood or some other material, the com mon response was to wait for spontane ous clearing. About ten years ago largely through the oral presentations of David Kasner, it became apparent that some eyes, at least, could manage without vitreous and the concept was changed to "If you lose a little vitreous, lose a lot." Thus began the era of anterior vitrectomy. Unfortunately, anterior vitrectomy frequently left strands
AMERICAN JOURNAL OF OPHTHALMOLOGY
muscle has a feathered or "paint brush" appearance. This is caused by the muscle descending out of the scan plane. In con trast, the orbital tumor has a sharp edge. In Graves' disease careful inspection of the scan series almost always reveals ad ditional swollen muscles. Swollen extraocular muscles may be distinguished from optic nerve sheath tumors because the entire length of the optic nerve is seen in another scan plane adjacent to the muscle. The size of normal orbital structures is at the limit of resolution of the standard EMI scanner. Reported improvements which increase resolution aid significant ly in recognizing extraocular muscles. We are calling attention to this matter because we are aware of several patients with swollen extraocular muscles who have had surgery on the basis of a false diagnosis of tumor at the orbital apex. S T E P H E N L. T R O K E L , SADEK K. H I L A L ,
APRIL, 1976
tionist will find that in sphere and cylin der only the 0.12 diopter value is really needed; occasionally the addition of 0.12 diopter sph may help equalize the acuity of the eyes, and sometimes the brightness of the principal axes of the astigmatic dial becomes even with an added 0.12 diopter cyl. Elimination of the rest of the 0.12 diopter series permits a better order of the thicker spheres. The 0.5 diopter gradation could then be extended to 8.5 diopters, 9.5 diopters, 10.5 diopters, 11.5 diopters, and 12.5 diopters. This change would facilitate refraction of both aphakic and highly myopic eyes. The cylinders of 0.37 diopters and 0.62 diopters may well be replaced by the more useful powers of 6.5 and 7.5 diopters. J A M E S E. L E B E N S O H N ,
Chicago,
M.D.
Illinois
M.D. M.D.
New York, New York Improving the Trial Case Editor: The modern precision trial case con tains spherical lenses of 0.12 diopter gra dation up to 1.75 diopters, 0.25 diopter intervals to 4.0 diopters followed by 0.5 diopter steps to 8.0 diopters, 1.0 diopter steps to 14.0 diopters and 2.0 diopter steps to 20.0 diopters. The cylinders are in 0.12 diopter gradation to 0.75 diopters then 0.25 diopter intervals to 3.5 diopters, followed by 0.5 diopter steps to 6.0 diop ters and 1.0 diopter steps to 8.0 diopters. Most ophthalmologists aim for 0.25 diop ter accuracy in sphere and cylinder since it is debatable whether a prescription of greater refinement can be filled reliably. A recent study by D. P. Renaldo, A. H. Keeney, and H. L. Duerson, Jr., "Ion exchange tempering of glass ophthalmic lenses," (Am. J. Ophthalmol. 80:291, 1975), supports this opinion. A perfec
BOOK REVIEWS Vitrectomy: A Pars Plana Approach. By Robert Machemer. Grune and Stratton, New York, 1975. Clothbound, 136 pages, table of contents, index, 87 black and white figures. $14.75 Up to about a decade ago the idea of losing vitreous was anathema to ophthal mic surgeons. Every attempt was made to contain the vitreous within the globe and in the presence of vitreous obscuration by blood or some other material, the com mon response was to wait for spontane ous clearing. About ten years ago largely through the oral presentations of David Kasner, it became apparent that some eyes, at least, could manage without vitreous and the concept was changed to "If you lose a little vitreous, lose a lot." Thus began the era of anterior vitrectomy. Unfortunately, anterior vitrectomy frequently left strands
