Dynamic Contour Tonometry: Handheld versus Slit-lamp–Mounted Pascal B. Knecht, MD, 1 Martina M. Bosch, MD, 1 Marcel N. Menke, MD, 1 Lucas M. Bachmann, MD, PhD, 2 Jens Funk, MD, 1 Claude Kaufmann, MD 1 Purpose: To compare the newly developed handheld dynamic contour tonometer (hh-DCT) with the estab- lished slit-lamp–mounted DCT (sl-DCT) in terms of agreement for intraocular pressure (IOP) and ocular pulse amplitude (OPA) measurements, intraobserver variability, and tonography effect. Design: Evaluation of diagnostic technology. Participants: Fifty eyes of 50 healthy volunteers were examined with the hh-DCT and sl-DCT. Methods: A paired t test was performed to analyze differences in IOP and OPA readings. Measurements were compared for bias and agreement according to the method of Bland and Altman. Intraclass correlation coefficients (ICCs) were calculated to compare intraobserver variability. A mixed model analysis was performed to assess a possible tonography effect. Main Outcome Measures: The differences in IOP and OPA measurements, intraobserver variability, and tonography effect between the hh-DCT and the sl-DCT were examined. Results: No statistically significant differences in IOP (sl-DCT-hh-DCT: 0.11.43 mmHg, 95% confidence interval [CI], -0.31 to 0.5, P = 0.63) or OPA (sl-DCT-hh-DCT: -0.10.52 mmHg, 95% CI, -0.28 to 0.01, P = 0.08) measurements were detected. Bland-Altman analysis revealed a bias of 0.1 with the limits of agreement of IOP measurement differences ranging from -2.71 to +2.90 mmHg. With regard to IOP readings obtained by sl-DCT, hh-DCT overestimated IOPs less than 15.6 mmHg and underestimated IOPs more than 15.6 mmHg. ICCs calculated for IOP readings were 0.87 (95% CI, 0.8 – 0.92) for hh-DCT and 0.85 (95% CI, 0.78 – 0.90) for sl-DCT. ICCs for OPA readings were 0.86 (95% CI, 0.79 – 0.91) for hh-DCT and 0.87 (95% CI, 0.8 – 0.91) for sl-DCT. Comparing the ICCs revealed no statistically significant difference between the devices with regard to IOP and OPA measurements (P = 0.53 and P = 0.93, respectively). Mixed model analysis of 3 consecutive IOP measurements revealed a decrease in IOP of 0.5 mmHg after each measurement in both devices, which was not significant between the 2 methods (P = 0.68). Conclusions: IOP and OPA readings obtained by the novel hh-DCT were shown to be strongly concordant with measurements obtained by the sl-DCT device. The hh-DCT may be a valuable alternative to the sl-DCT in clinical practice. Financial Disclosure(s): The author(s) have no proprietary or commercial interest in any materials discussed in this article. Ophthalmology 2009;116:1450 –1454 © 2009 by the American Academy of Ophthalmology. Since the first report about Dynamic Contour Tonometry (DCT) in 2003, 1 a vast amount of scientific literature has been developed on this subject, which has been reviewed in detail elsewhere. 2 The main findings that emerge from these reports suggest that intraocular pressure (IOP) and ocular pulse amplitude (OPA) measurements with DCT in normal eyes are hardly affected by corneal properties such as thickness and curva- ture and that intraobserver and interobserver variabilities are small. 1,3 In human cadaver eyes, IOP values obtained with DCT are closer to the manometric reference pressure than those measured with Goldmann Applanation Tonometry. 4 The recent incorporation of a DCT-tonometer tip into a Perkins tonometer handpiece (Haag-Streit, Munich, Ger- many) showed promising results when compared with si- multaneous intracameral pressure measurements. 5 We set out to compare the prototype of a newly designed handheld DCT (hh-DCT) with the established slit-lamp–mounted DCT (sl-DCT) in terms of agreement for IOP and OPA measurements, intraobserver variability, and tonography ef- fect (a decrease in IOP caused by successive or prolonged measurements performed on the same eye) in an outpatient setting. Materials and Methods This was a prospective, single-center, randomized study. Informed consent was obtained from each subject, adhering to the tenets of the Declaration of Helsinki. The study protocol was approved by the local ethics committee. None of the subjects had any history of ocular disease, trauma, or surgery. Slit-lamp findings were unre- markable. Inability to comply with repeated contact measurements represented an exclusion criterion. Only right eyes were examined. All measurements were performed by the same experienced oph- thalmologist (PBK). Measurement Technique/Procedure IOP and OPA measurements were taken by sl-DCT and hh-DCT devices in random order. Measurements with the sl-DCT were 1450 © 2009 by the American Academy of Ophthalmology ISSN 0161-6420/09/$–see front matter Published by Elsevier Inc. doi:10.1016/j.ophtha.2009.02.006