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Abstract #9662 Published in IGR 5-3
Assessment of reproducibility of measures of intraocular pressure and central corneal thickness in young white adults over a 16-h time period.
Aakre BM; Doughty MJ; Dalane OV; Berg A; Aamodt O; Gangstad HOphthalmic and Physiological Optics 2003; 23: 271-283
PURPOSE: The aims of this study were to obtain clinical measurements of intraocular pressure (IOP) and central corneal thickness (CCT) and during waking hours to further assess both the nature of diurnal changes, and the reproducibility of any possible association between the two measures. METHODS: Fifteen white (Norwegian) healthy young adult subjects aged 20-29 years had IOP and CCT measurements made, using a non-contact specular microscope and non-contact tonometry (NCT), every hour over a period of 16 hours, starting at 06.30 hours. The experiment was repeated on two successive days. RESULTS: The average NCT readings were 12.5 and 11.4 mmHg for days 1 and 2, while pachometry averages were 0.518 and 0.514 mm. The range of NCT values, for any set of readings, averaged 2 mmHg, while this range was 0.014 mm for CCT measurements. The reproducibility of these measurements, as estimated by the coefficient of variation (COV), was 7.2% for NCT and 1.0% for pachometry. The COV for tonometry was inversely proportional to the actual values of these measurements. A significant time-related decline in tonometry values was seen over day 1, but not day 2. Pachometry values declined very rapidly over the first hour in both sessions and were essentially constant for the remainder of the sessions. The strongest association between pachometry data and NCT measurements was noted around midday (12.30 hours) on both sessions. CONCLUSIONS: These studies confirm that the reproducibility (repeatability) of NCT and pachometry are substantially different. It is suggested that this aspect of tonometry needs to be taken into account, especially where there are lower values, when considering the possible impact of corneal thickness on tonometry measurements and their interpretation. These types of effects need to be further assessed in older patients with ocular hypertension, or other glaucoma suspects.
Dr. B.M. Aakre, Buskerud College, Department of Optometry, Kongsberg, Norway
Classification:
2.2 Cornea (Part of: 2 Anatomical structures in glaucoma)
6.1 Intraocular pressure measurement; factors affecting IOP (Part of: 6 Clinical examination methods)