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Optics of Contact Lenses
1092
BOOK REVIEWS
1951 (C. V. Mosby), under the title Surgery of the Oblique Muscles of the Eye. It was a popular and useful book that did an excellent job of encouraging the ophthalmic surgeon to work on these muscles which were then almost forbidden territory. We have watched Dr. Fink's work over the years with keen interest. He has always been a dedicated and meticulous investigator, bas ing his studies on beautifully dissected ana tomic specimens in great quantity. He applied the fundamental knowledge he obtained so painstakingly to the clinic and the operating room. And then he shared his information with us. It is good to see that he has continued his life's work, and so, in the last 11 years, has been able to add much of value to the disen tangling of a complex problem of diagnosis and surgical treatment, in which he was a real pioneer. This present edition, therefore, in many places shows much work in revision and re writing, as well as in bringing the subject up to date by the addition of further reports on the author's vast experiences and those of his colleagues working in this field. Part I concerns the anatomy of the vertical muscles (142 pages). It includes embryology, comparative anatomy, gross and microscopic anatomy and the surgical anatomy. Part II, management of vertical muscle defects (272 pages), includes an historical re view of the surgery of the vertical muscles, the frequency of defects, etiology, physiology, diagnosis, surgical indications, techniques and pitfalls in vertical muscles surgery. An appendix then follows that concerns the anatomic considerations in operations on reti nal detachment. One will find this helpful and useful. The illustrations are well chosen and good. The book will be well received and will attract a wide audience, which it merits. Derrick Vail.
By A. G. Ben nett. London, Association of Dispensing Opticians, 1963, edition 3. 85 pages, 56 figures, paperbound. Price: $2.25. Sir John Herschel in his article on "Light" in the Encyclopedia Metropolitania, 1827, dis cussed Airy's correction of his own astigma tism and offered an arm-chair suggestion of a contact lens as a better means for compensat ing "the malformation of the cornea." Heine, in 1929, initiated the first wave of popularity for contact-lens corrections. His afocal lens is no longer prescribed, the choice of optic radius being now determined by physical re quirements. As it is important to reduce the weight of the lens to a minimum, if two radii seem equally suitable, one should choose that requiring less added power in the contact lens. To produce in the finished lens precisely the same optical effect as that obtained with a trial contact lens plus a separate lens in a trial frame calls for the highest degree of skill on the part of all concerned. To be accurate to 0.12D., the inner optic radius must be correct within 0.025 mm., the outer optic radius to 0.015 mm. and the central thickness to 0.05 mm. Should such minimal errors be additive, an error of 0.37D. results. Though the re quirements for accuracy are so rigid, plastic material is more difficult to work optically than glass, owing to its springiness. Com pared with spectacles, contact lenses for dis tance correction impose a greater accommoda tive effort on myopes and a smaller effort on hypermétropes when used in near vision. Wil liamson-Noble introduced the bifocal contact lens in his Presidential Address to the Con tact Lens Society of Great Britain in 1950. The prism ballast segment type has appar ently solved the problem. It is effective be cause of a relative upward movement of the contact lens when the eye is lowered, thereby lifting the reading portion over part of the pupillary area. James E. Lebensohn. OPTICS OF CONTACT LENSES.
BOOK REVIEWS
1951 (C. V. Mosby), under the title Surgery of the Oblique Muscles of the Eye. It was a popular and useful book that did an excellent job of encouraging the ophthalmic surgeon to work on these muscles which were then almost forbidden territory. We have watched Dr. Fink's work over the years with keen interest. He has always been a dedicated and meticulous investigator, bas ing his studies on beautifully dissected ana tomic specimens in great quantity. He applied the fundamental knowledge he obtained so painstakingly to the clinic and the operating room. And then he shared his information with us. It is good to see that he has continued his life's work, and so, in the last 11 years, has been able to add much of value to the disen tangling of a complex problem of diagnosis and surgical treatment, in which he was a real pioneer. This present edition, therefore, in many places shows much work in revision and re writing, as well as in bringing the subject up to date by the addition of further reports on the author's vast experiences and those of his colleagues working in this field. Part I concerns the anatomy of the vertical muscles (142 pages). It includes embryology, comparative anatomy, gross and microscopic anatomy and the surgical anatomy. Part II, management of vertical muscle defects (272 pages), includes an historical re view of the surgery of the vertical muscles, the frequency of defects, etiology, physiology, diagnosis, surgical indications, techniques and pitfalls in vertical muscles surgery. An appendix then follows that concerns the anatomic considerations in operations on reti nal detachment. One will find this helpful and useful. The illustrations are well chosen and good. The book will be well received and will attract a wide audience, which it merits. Derrick Vail.
By A. G. Ben nett. London, Association of Dispensing Opticians, 1963, edition 3. 85 pages, 56 figures, paperbound. Price: $2.25. Sir John Herschel in his article on "Light" in the Encyclopedia Metropolitania, 1827, dis cussed Airy's correction of his own astigma tism and offered an arm-chair suggestion of a contact lens as a better means for compensat ing "the malformation of the cornea." Heine, in 1929, initiated the first wave of popularity for contact-lens corrections. His afocal lens is no longer prescribed, the choice of optic radius being now determined by physical re quirements. As it is important to reduce the weight of the lens to a minimum, if two radii seem equally suitable, one should choose that requiring less added power in the contact lens. To produce in the finished lens precisely the same optical effect as that obtained with a trial contact lens plus a separate lens in a trial frame calls for the highest degree of skill on the part of all concerned. To be accurate to 0.12D., the inner optic radius must be correct within 0.025 mm., the outer optic radius to 0.015 mm. and the central thickness to 0.05 mm. Should such minimal errors be additive, an error of 0.37D. results. Though the re quirements for accuracy are so rigid, plastic material is more difficult to work optically than glass, owing to its springiness. Com pared with spectacles, contact lenses for dis tance correction impose a greater accommoda tive effort on myopes and a smaller effort on hypermétropes when used in near vision. Wil liamson-Noble introduced the bifocal contact lens in his Presidential Address to the Con tact Lens Society of Great Britain in 1950. The prism ballast segment type has appar ently solved the problem. It is effective be cause of a relative upward movement of the contact lens when the eye is lowered, thereby lifting the reading portion over part of the pupillary area. James E. Lebensohn. OPTICS OF CONTACT LENSES.