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Astigmatism from Lens Tilt
or anterior chamber implants are rarely seen with uncomplicated ECCE and posterior chamber 10Ls. Robert C. Maynor, Jr., M.D .
Huntsville, Alabama
ASTIGMATISM FROM LENS TILT To the Editor: I would like to comment on the article by Jolson and Seidl, "Postoperative Astigmatism Induced by Intraocular Lens Tilt" (Am Intra-Ocular Implant Soc] 10:213-214, 1984), in which the authors describe a significant astigmatic change in correction that was not manifest in a keratometry reading, but is ascribed to the tilt of a posterior chamber intraocular lens (IOL). The astigmatism was present when the 10L was tilted, but disappeared after tilt was cured by YAG laser surgery. The lens implanted was a 20 diopter Coburn Model 70. This lens, as all Coburn lenses, is a biconvex posterior chamber lens. On page 214, the authors present a table that shows the amount of astigmatism that can be expected with varying posterior chamber lens tilt and diopter power. The authors do not, however, give the source of this table and whether it applies to biconvex lenses, plano convex, as well as convexo concave. I might guess that this was supplied by the manufacturer and might apply only to biconvex lenses.
Over the years I have had the opportunity to see several posterior chamber lenses tilted in varying degrees . Ihave never seen astigmatism of the magnitude reported by Jolson and Seidl from a tilted posterior chamber lens. All such lenses examined were plano convex with the plano surface posterior. Kenneth J. Hoffer, M.D .
Santa Monica, California
Dr. Jolson replies : The source for the table on astigmatism induced by intraocular lens (IOL) tilt is Clinical Refraction by I. M. Borish, 3rd ed, Chicago, The Professional Press, Inc, 190 p 1HO (reference 3 in the article). Percival's chart for resultant cylindrical power for lens tilt in the vertical meridian per diopter is as follows: Degree of Tilt 15
20
25
30 35
Cylinder
.0734 .1379 .2315
.3349
.5547
The amount of astigmatism induced by a particular 10L power is obtained by multiplying the lens power by the cylinder factor. This method of calculation was confirmed by Dr. Melvin Rubin. It is not specified whether Percival's calculations are based on biconvex or plano convex lenses. Alfred S. Jolson, M.D. Winter Park, Florida
AM INTRA-OCULAR IMPLANT SOC J-VOL 11, JANUARY 1985
67
Huntsville, Alabama
ASTIGMATISM FROM LENS TILT To the Editor: I would like to comment on the article by Jolson and Seidl, "Postoperative Astigmatism Induced by Intraocular Lens Tilt" (Am Intra-Ocular Implant Soc] 10:213-214, 1984), in which the authors describe a significant astigmatic change in correction that was not manifest in a keratometry reading, but is ascribed to the tilt of a posterior chamber intraocular lens (IOL). The astigmatism was present when the 10L was tilted, but disappeared after tilt was cured by YAG laser surgery. The lens implanted was a 20 diopter Coburn Model 70. This lens, as all Coburn lenses, is a biconvex posterior chamber lens. On page 214, the authors present a table that shows the amount of astigmatism that can be expected with varying posterior chamber lens tilt and diopter power. The authors do not, however, give the source of this table and whether it applies to biconvex lenses, plano convex, as well as convexo concave. I might guess that this was supplied by the manufacturer and might apply only to biconvex lenses.
Over the years I have had the opportunity to see several posterior chamber lenses tilted in varying degrees . Ihave never seen astigmatism of the magnitude reported by Jolson and Seidl from a tilted posterior chamber lens. All such lenses examined were plano convex with the plano surface posterior. Kenneth J. Hoffer, M.D .
Santa Monica, California
Dr. Jolson replies : The source for the table on astigmatism induced by intraocular lens (IOL) tilt is Clinical Refraction by I. M. Borish, 3rd ed, Chicago, The Professional Press, Inc, 190 p 1HO (reference 3 in the article). Percival's chart for resultant cylindrical power for lens tilt in the vertical meridian per diopter is as follows: Degree of Tilt 15
20
25
30 35
Cylinder
.0734 .1379 .2315
.3349
.5547
The amount of astigmatism induced by a particular 10L power is obtained by multiplying the lens power by the cylinder factor. This method of calculation was confirmed by Dr. Melvin Rubin. It is not specified whether Percival's calculations are based on biconvex or plano convex lenses. Alfred S. Jolson, M.D. Winter Park, Florida
AM INTRA-OCULAR IMPLANT SOC J-VOL 11, JANUARY 1985
67