To the Editor:
Having read the Special Article by Eydelman et al on "Standardized Analyses of Correction of Astigmatism by Laser Systems That Reshape the Cornea/'1 Alpins' letter concerning some deficits in referencing,2 the reply to this letter by Eydelman et al,3 and the editorial comment by Waring,4 I am still not clear what previous publication served as the main basis for the recommendations put forward by Eydelman et al. My own reading of the literature suggests it is largely based on work published by Alpins in 1993 and 19975,6 along with the other work referenced in the Special Article. Is this the case?
It does not "benefit" the reader for a reference list in this kind of article to be "limited" or "concise." This should be a definitive work with as extensive a reference list as would be implied by the 4 years work that went into its creation and as it is to be the basis for an ANSI standard.3
Finally, the reply does not address the need for change in nomenclature from that in current use. The change of "magnitude of error" to "error of magnitude" or "angle of error" to "error of angle" does not seem substantial nor justified.3 Such changes may introduce confusion in a subject in need of clarity.
Michael Goggin, FRCSI(Ophth), FRCOphth, FRANZCO, MS
South Australia, Australia
1. Eydelman MB, Drum B, Holladay J, Humante G, Kezirian G, Durrie D, Stulting D, Sanders D, Wong B. Standardized analyses of correction of astigmatism by laser systems that reshape the cornea. J Refract Surg. 2006;22:81-95.
2. Alpins N. Terms used for the analysis of astigmatism. J Refract Surg. 2006;22:528.
3. Eydelman MB, Drum B, Holladay J, Humante G, Kezirian G, Durrie D, Stulting D, Sanders D, Wong B. Terms used for the analysis of astigmatism [reply]. J Refract Surg. 2006;22:528-529.
4. Waring G. Editors comment: review process for special articles. J Refract Surg. 2006;22:529.
5. Alpins N. A new method of analyzing vectors for changes in astigmatism. J Cataract Refract Surg. 1993;19:524-533.
6. Alpins N. Vector analysis of astigmatism changes by flattening, steepening, and torque. J Cataract Refract Surg. 1997;23:1503-1514.
Goggin's inference that our work1 was based "largely" on Alpins' 1993 and 1997 papers23 is inaccurate. We agree that, in retrospect, it might have been appropriate to include the 1993 paper in our reference list However, our recommendations are based directly on established mathematical principles of vector addition. They draw from the published work of a number of authors besides Alpins and from extensive discussions and written communications among the members of the ANSI Z80 Astigmatism Project Group. As we pointed out in our response to Alpins' earlier letter,4 we cited his 2001 paper,5 which recapitulated his earlier work and referenced his 1993 and 1997 papers.
We disagree with Goggin that our reference list should have been "extensive." Our paper is neither a review article nor an attempt to resolve outstanding issues in the literature. We expect that most readers of our paper will use it as a practical "cookbook" to aid them in analyzing and reporting data from US Food and Drug Administration-regulated clinical trials. Those who wish to delve more deeply will find an adequate window to the literature in the review articles we cited.
Regarding the (surprisingly) sensitive terminology issue, we note that Holladay et al6 published a method for analyzing "Surgically Induced Refractive Change" a year before Alpins2 proposed the term "Surgically Induced Astigmatism Vector" for the same parameter.
We do not consider Alpins or any other author to have a monopoly on astigmatic analysis terminology. Terms will be adopted by the scientific and clinical communities to the extent that they are accurate and useful. We endeavored to develop terms that are consistent with each other and that accurately describe the corresponding analysis parameters. Some are identical to terms in publications, others are modified from published terms to improve accuracy and clarity, and still others are original. With regard to the examples from Alpins' letter,4 we decided that the terms "Error of Angle" and "Error of Magnitude" more clearly and accurately describe the angular and magnitude differences between the intended and achieved refractive change than "Angle of Error" and "Magnitude of Error." We believe that our other four terms in Alpins' table (Error Vector, Error Ratio, Correction Ratio, and Intended Refractive Correction) express the meanings of the underlying analysis parameters more clearly and explicitly than Alpins' equivalent terms.
Malvina B. Eydelman, MD
Bruce Drum, PhD
Jack Holladay, MD, MSEE, FACS
Gene Hilmantel, OD, MS
Guy Kezirian, MD
Daniel Durrie, MD
R. Doyle Stulting, MD, PhD
Donald Sanders, MD, PhD
Bonita Wong, OD, MSc
Astigmatism Project Group
1. Eydelman MB, Drum B, Holladay J, Hilmantel G, Kezirian G, Durrie D, Stulting RD, Sanders D, Wong B. Standardized analyses of correction of astigmatism by laser systems that reshape the cornea. J Refract Surg. 2006;22:81-95.
2. Alpins NA. A new method of analyzing vectors for changes in astigmatism. J Cataract Refract Surg. 1993;19:524-533.
3. Alpins NA. Vector analysis of astigmatism changes by flattening, steepening, and torque. J Cataract Refract Surg. 1997;23:1503-1514.
4. Alpins N. Terms used for the analysis of astigmatism. J Refract Surg. 2006;22:528.
5. Alpins N. Astigmatism analysis by the Alpins method. J Cataract Refract Surg. 2001;27:31-49.
6. Holladay JT, Cravy TV, Koch DD. Calculating the surgically induced refractive change following ocular surgery. J Cataract Refract Surg. 1992;18:429443.