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Biconcave Contact Lens For Vitreous Surgery
TABLE C R I T E R I A F O R I D E N T I F I C A T I O N O F BACILLUS
LICHENIFORMIS
Test
Result Long, thin, gram+, variably sized rod with subterminal spores Equal Positive Positive Beta hemolysis Alkaline Positive Positive Negative Positive Negative Positive Negative Negative Positive Basic/Acid
Gram stain Growth at 37 and 50°C Motility Anaerobic growth Hemolysis on rabbit blood agar 10% lactose Catalase Oxidase Salmonella-Shigella medium Citrate Urea Nitrate Indol Methyl red Voges-Proskauer Triple sugar iron (TSI) agar (slant/butt) Hydrogen sulfide production Gelatin Litmus milk Nutrient broth: 0% N a C l 6% N a C l 7% N a C l Starch hydrolysis Glucose D-xylose Mannitol Lactose Sucrose Maltose
Negative Partially positive at 7 days Negative Positive Positive Positive Positive Acid Acid Acid and gas No change Acid Acid
ma of this kind is believed to predispose to corneal infection. SUMMARY
A 46-year-old woman developed a cor neal ulcer after an injury to the right eye. Cultures were positive for Bacillus lich eniformis. Although resistant to some an tibiotics, the corneal ulcer resolved after treatment with topical, subconjunctival, and intramuscular gentamicin sulfate.
5. Tabbara, K. F., Juffali, F., and Matossian, R. M.: Bacillus laterosporus endophthalmitis. Arch. Ophthalmol. 95:2187, 1977. 6. Farrar, W. E.: Serious infections due to "nonpathogenic" organisms of the genus Bacillus. Am. J. Med. 34:134, 1963. 7. Pearson, H. E.: Human infections caused by organisms of the Bacillus species. Am. J. Clin. Pathol. 53:506, 1970.
BICONCAVE CONTACT LENS FOR VITREOUS SURGERY
REFERENCES
J O H N G. S E B E S T Y E N , M.
1. Sugar, A. M., and McCloskey, R. V.: Bacillus licheniformis sepsis. J.A.M.A. 238:1180, 1977. 2. Ihde, D. C , and Armstrong, D. A.: Clinical spectrum of infection due to Bacillus species. Am. J. Med. 55:839, 1973. 3. Van Bijsterveld, O. P., and Richards, R. D.: Bacillus infections of the cornea. Arch. Ophthalmol. 74:91, 1965. 4. Davenport, R., and Smith, C.: Panophthalmitis due to an organism of the Bacillus subtilis group. Br. J. Ophthalmol. 36:389, 1952.
Boston,
D.
Massachusetts
During trans pars plana vitreous surgi cal procedures adequate visualization of From the Wm. P. Beetham Eye Unit, Joslin Clin ic, Joslin Diabetic Foundation, Boston, Massachu setts. Reprint requests to John G. Sebestyen, M.D., One Joslin Place, Boston, MA 02215.
719
720
AMERICAN JOURNAL O F OPHTHALMOLOGY
the fundus is essential. The posterior pole usually can be seen well with any of the customarily used plano-concave contact lenses. All of these lenses neutralize the refractive power of the cornea, thus mak ing the retina accessible to viewing with the operating microscope. When the sur geon has to work at or near the equator of the globe, the eye has to be turned. This maneuver requires that the contact lens be tilted to a plane oblique to the sur geon's visual axis. The result will be that the surgeon sees the fundus through an oval, and therefore, smaller, pupil instead of a round one. At the same time, the more peripherally one has to look, the more tilting of the lens is required, and the more distorted the view becomes. To minimize the need for turning the eye I designed a surgical contact lens* that has a much larger field of vision, which allows a view of the fundus as far as the equator. The lens is made of polymethylmethacrylate that has a refractive index of 1.49 by lathe cutting. It is bicon cave in design (Figure), one of its surfaces has a radius of curvature of 12.5 mm, whereas the opposite surface is 13.5 mm. The diameter of the lens is 9.0 mm and its center thickness is 0.5 mm. Its refractive power is —75.50 diopters in air, by calcu lation. The lens is applied to the cornea by floating it on balanced salt solution. Ei ther the flatter or steeper surface faces the surgeon. The image size is greatly reduced from that seen through a plano-concave lens. This difficulty is easily overcome by in creasing the magnification of the operat ing microscope. Slight displacements of the lens from the central position bring into view the more peripheral parts of the fundus, because a strong optical lens has
*The lens was manufactured by LVR Contact Lens Laboratory, 636 Beacon St., Boston, MA 02215.
MAY, 1979
0-5mm.
13.5mm.
9 . 0 mm.
Figure (Sebestyen). Schematic drawing of bicon cave contact lens.
an induced prismatic power when a por tion of the lens is used that is not in its optical axis. In the case of a —75.50 diop ter lens, each millimeter away from the optical axis represents an approximately 7.5 prism diopter power displacing the image toward the center of the lens, that is, apex of the prism. The equator can be visualized easily by a minimal movement of the globe or by sliding of the lens. Lenses of any desired dioptric power and, therefore, different prismatic effects, can be designed by using the following for mula 1000 (n - 1) D = where D stands for dioptric power, n is the refractive index of the lens material, and r is the radius of curvature in milli meters. SUMMARY
I designed a biconcave floating contact lens used for trans pars plana vitreous surgery. The lens uses the prismatic power of strong optical lenses to bring into view portions of the fundus that otherwise would be difficult to see.
LICHENIFORMIS
Test
Result Long, thin, gram+, variably sized rod with subterminal spores Equal Positive Positive Beta hemolysis Alkaline Positive Positive Negative Positive Negative Positive Negative Negative Positive Basic/Acid
Gram stain Growth at 37 and 50°C Motility Anaerobic growth Hemolysis on rabbit blood agar 10% lactose Catalase Oxidase Salmonella-Shigella medium Citrate Urea Nitrate Indol Methyl red Voges-Proskauer Triple sugar iron (TSI) agar (slant/butt) Hydrogen sulfide production Gelatin Litmus milk Nutrient broth: 0% N a C l 6% N a C l 7% N a C l Starch hydrolysis Glucose D-xylose Mannitol Lactose Sucrose Maltose
Negative Partially positive at 7 days Negative Positive Positive Positive Positive Acid Acid Acid and gas No change Acid Acid
ma of this kind is believed to predispose to corneal infection. SUMMARY
A 46-year-old woman developed a cor neal ulcer after an injury to the right eye. Cultures were positive for Bacillus lich eniformis. Although resistant to some an tibiotics, the corneal ulcer resolved after treatment with topical, subconjunctival, and intramuscular gentamicin sulfate.
5. Tabbara, K. F., Juffali, F., and Matossian, R. M.: Bacillus laterosporus endophthalmitis. Arch. Ophthalmol. 95:2187, 1977. 6. Farrar, W. E.: Serious infections due to "nonpathogenic" organisms of the genus Bacillus. Am. J. Med. 34:134, 1963. 7. Pearson, H. E.: Human infections caused by organisms of the Bacillus species. Am. J. Clin. Pathol. 53:506, 1970.
BICONCAVE CONTACT LENS FOR VITREOUS SURGERY
REFERENCES
J O H N G. S E B E S T Y E N , M.
1. Sugar, A. M., and McCloskey, R. V.: Bacillus licheniformis sepsis. J.A.M.A. 238:1180, 1977. 2. Ihde, D. C , and Armstrong, D. A.: Clinical spectrum of infection due to Bacillus species. Am. J. Med. 55:839, 1973. 3. Van Bijsterveld, O. P., and Richards, R. D.: Bacillus infections of the cornea. Arch. Ophthalmol. 74:91, 1965. 4. Davenport, R., and Smith, C.: Panophthalmitis due to an organism of the Bacillus subtilis group. Br. J. Ophthalmol. 36:389, 1952.
Boston,
D.
Massachusetts
During trans pars plana vitreous surgi cal procedures adequate visualization of From the Wm. P. Beetham Eye Unit, Joslin Clin ic, Joslin Diabetic Foundation, Boston, Massachu setts. Reprint requests to John G. Sebestyen, M.D., One Joslin Place, Boston, MA 02215.
719
720
AMERICAN JOURNAL O F OPHTHALMOLOGY
the fundus is essential. The posterior pole usually can be seen well with any of the customarily used plano-concave contact lenses. All of these lenses neutralize the refractive power of the cornea, thus mak ing the retina accessible to viewing with the operating microscope. When the sur geon has to work at or near the equator of the globe, the eye has to be turned. This maneuver requires that the contact lens be tilted to a plane oblique to the sur geon's visual axis. The result will be that the surgeon sees the fundus through an oval, and therefore, smaller, pupil instead of a round one. At the same time, the more peripherally one has to look, the more tilting of the lens is required, and the more distorted the view becomes. To minimize the need for turning the eye I designed a surgical contact lens* that has a much larger field of vision, which allows a view of the fundus as far as the equator. The lens is made of polymethylmethacrylate that has a refractive index of 1.49 by lathe cutting. It is bicon cave in design (Figure), one of its surfaces has a radius of curvature of 12.5 mm, whereas the opposite surface is 13.5 mm. The diameter of the lens is 9.0 mm and its center thickness is 0.5 mm. Its refractive power is —75.50 diopters in air, by calcu lation. The lens is applied to the cornea by floating it on balanced salt solution. Ei ther the flatter or steeper surface faces the surgeon. The image size is greatly reduced from that seen through a plano-concave lens. This difficulty is easily overcome by in creasing the magnification of the operat ing microscope. Slight displacements of the lens from the central position bring into view the more peripheral parts of the fundus, because a strong optical lens has
*The lens was manufactured by LVR Contact Lens Laboratory, 636 Beacon St., Boston, MA 02215.
MAY, 1979
0-5mm.
13.5mm.
9 . 0 mm.
Figure (Sebestyen). Schematic drawing of bicon cave contact lens.
an induced prismatic power when a por tion of the lens is used that is not in its optical axis. In the case of a —75.50 diop ter lens, each millimeter away from the optical axis represents an approximately 7.5 prism diopter power displacing the image toward the center of the lens, that is, apex of the prism. The equator can be visualized easily by a minimal movement of the globe or by sliding of the lens. Lenses of any desired dioptric power and, therefore, different prismatic effects, can be designed by using the following for mula 1000 (n - 1) D = where D stands for dioptric power, n is the refractive index of the lens material, and r is the radius of curvature in milli meters. SUMMARY
I designed a biconcave floating contact lens used for trans pars plana vitreous surgery. The lens uses the prismatic power of strong optical lenses to bring into view portions of the fundus that otherwise would be difficult to see.