To the Editor.
—Cartwright and Anderson,1 in the July 1988 issue of the Archives, reported higher intraocular pressure (IOP) in the eye with greater visual damage in 12 of 14 cases of normal-tension glaucoma. They concluded that this "constitutes evidence that the IOP participates in the production of damage." I do not believe that this conclusion is supported by this study.The methods used by the authors clearly demonstrate the association of increased IOP with glaucoma damage. (One could argue whether a difference of 1 mm Hg, the demonstrated difference in five of 12 cases, is clinically significant, but the point made by the authors is that the higher IOP was present in the eye with more damage.) An observed association as in this study does not constitute the establishment of cause and effect as the authors imply. The reason for the association between increased IOP and glaucoma
Choplin NT. Correlation of Asymmetric Damage With Asymmetric Intraocular Pressure in Normal-Tension Glaucoma (Low-Tension Glaucoma). Arch Ophthalmol. 1989;107(2):167-168. doi:10.1001/archopht.1989.01070010173007