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September 2012 February 2011 EW GLAUCOMA 79 she said, is to preserve quality of life in glaucoma patients. "However, we do not know the stage of glaucoma, the IOP level, or the age at which quality of life starts to deteriorate in a significant way." Thus, the determination of target IOP must be customized for each patient, and perhaps for each eye, based on the individual patient's risk profile. "Three primary considerations factor into the target IOP determina- tion," Dr. Hoffmann said. "These are the stage of glaucoma, the life expectancy of the patient, and the IOP level at which prior damage occurred." As for coming up with the exact target IOP value, she said that this is as much art as science. "Target pres- sure should be a range rather than an absolute number. It is not an ab- solute. It is a best guess, a useful and practical way to simplify our lives in the clinic by defining our therapeu- tic goals." She added, "Once set, the target IOP should not be considered set in stone. It should be re-evaluated and revised over time as the patient's risk profile changes." Central corneal thickness: Does it matter? As important as IOP is in the management of glaucoma, it is im- portant to have the appropriate per- spective when evaluating the IOP value. "True IOP does not exist in the clinic—it is just an estimate," said Jose Morales, M.D., King Khalid Eye Hospital, Saudi Arabia. It is well known that the biome- chanical properties of the cornea— of which central corneal thickness is just one—affect the validity of applanation tonometry. Acknowledging a frequent question about corneal thickness and IOP, Dr. Morales asked, "Can we correct IOP on the basis of corneal thickness? There are several formulas that have been proposed to do just this. They are mostly linear, how- ever, and they ignore the reality that the relationship between corneal thickness and IOP is complex and nonlinear." More importantly, he pointed out, "Adjusting IOP based on corneal thickness does not improve the prediction models for the devel- opment of glaucoma in the Ocular Hypertension Treatment Study." 3222 Phoenixville Pike, Malvern, PA 19355 • USA 800-979-2020 • 610-889-0200 • FAX 610-889-3233 • www.accutome.com Product #24-4200 Receive a Free Toric Marker with Purchase Visit us at AAO Booth #4221 Meeting the Needs of Your Premium IOL Patient • Industry Leading Resolution • 100% Measurement Capability including dense cataracts • Automatic Alignment Detection • Simplified Personalization of Lens Constants • Unlimited patient data storage, recall, and transfer via USB Memory Stick Every purchase of an A-Scan Plus 4.20 comes with an on-site training program. Since the existing risk calcula- tors allow inclusion of both IOP and central corneal thickness as risk factors, he recommended treating them separately unless future re- search suggests a better approach. EW Reference Gardiner SK, Johnson CA, Demirel S. Factors predicting the rate of functional progression in early and suspected glaucoma. Invest Oph- thalmol Vis Sci. 2012 Jun 14;53(7):3598-604. Contact information Hoffmann: ehoffman@mail.uni-mainz.de Morales: jmorales@kkesh.med.sa Susanna: rsusanna@terra.com.br Right On Target... The New A-Scan Plus®4.20