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L. Liu; Central Corneal Thickness vs. IOP and Time . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4449.
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To observe the variability of central corneal thickness in relation to intraocular pressure (IOP) and time
The central corneal thickness was measured in patients from a private clinic using a non–contact partial coherence interferometer (PCI) pachymeter (Haag–Streigt) and a contact ultrasonic (US) pachymeter (Heidelberg Engineering). 3 consecutive corneal thickness readings were taken using the non–contact pachymeter prior to the intraocular pressure being measured using a Goldmann tonometer. Then the 3 readings were repeated using the contact pachymeter.
This was then repeated over 2 separate consecutive visits within a 3–4 month period.
236 eyes of 123 patients (predominantly glaucoma suspects) were examined over the 3 visits. 150 had no medical or surgical intervention over the 3 visits. The mean observation period was 33+/–25.5 days. When measured with the PCI pachymeter
a) the mean change in CCT was –0.5 ± 8.5 um (visit 2) and –1.7 ± 9.7 um (visit 3, p=0.034) from the first visit
b) in ocular hypertensives (IOP > 21mmHg), the mean change in CCT was +1.3 ± 8.9 um (visit 2) and +2.7 ± 7.5 um (visit 3, p=0.005) from the first visit
c) there was a linear association between a change in CCT and a change in IOP (R2=0.0291, p=0.013)
The mean difference between PCI and ultrasound pachymeter measurements was up to –4.5 ± –6.4 microns (p<0.05). There was a strong correlation between both instrument measurements at all 3 visits (R2 = 0.895, p<0.05)
Central corneal thickness is a) quite stable over time
b) undergoes very small changes in ocular hypertensive patients and
c) undergoes a very small change with changes in IOP
Whether this is clinically significant or not remains unclear.
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