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Laura Sanchez Parra, Roger Buckley, Shahina Pardhan, Rupert Bourne, Investigating Management of Primary Angle Closure Treatment Study: IMPACT Study; The association of Diurnal Intraocular Pressure (DIOP) fluctuation and anterior chamber angle dimensions in patients with primary angle closure, and the association with peripheral anterior synechiae (PAS): The Investigating Management of Angle Closure and Treatment (IMPACT) study. Invest. Ophthalmol. Vis. Sci. 2013;54(15):3489.
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To investigate the hypothesis that greater extent of PAS and narrower values for Angle Opening Distance (AOD), Angle Recess Area (ARA), Trabecular-Iris Space Area (TISA) and Trabecular-Iris Angle (TIA), are associated with greater DIOP fluctuation, using 3-dimensional swept-source anterior segment optical coherence tomography (AS-OCT)
40 Caucasian patients with a diagnosis of Primary Angle Closure (PAC) and/or Primary Angle Closure Suspect (PACS) and no ocular co-morbidity were recruited. IOP was measured hourly from 9.00h to 16.00h with Goldmann applanation tonometry. Fluctuation was defined as the difference between the maximum and minimum IOP during that period. AOD, ARA, TISA and TIA were measured using the novel AS-OCT (CASIA) in dark (0.3-0.5 lux) and light (170-200 lux) on the same day of DIOP measurements and quantified in 8 different sections of the angle (Superior, Superior-Nasal, Nasal, Inferior-Nasal, Inferior, Inferior-Temporal, Temporal and Superior-Temporal) and at 500 and 700μm from the scleral spur
DIOP fluctuation ranged between 1.50 mmHg and 14.50 mmHg (mean 5.92±2.82 mmHg). Single predictor models were statistically significant for the majority of angle parameters in Superior and Superior-Nasal sections, showing standardized coefficients from -254 to -438, demonstrating an inverse relationship between angle parameters and DIOP in these sections. Additionally, the higher contribution to the multiple predictor models was provided by negative standardised coefficients showing a similar inverse relationship for the remaining angle sections. These models were statistically significant (p<0.05) for AOD 750 (light), ARA 750 (light and dark), TISA 500 and 750 (light), TIA 500 (light) and TIA 750 (light and dark). Single predictor models showed a statistically significant direct association between the degree of PAS and IOP at every time measurement of the DIOP excluding 12:00h IOP. An association between DIOP fluctuation and PAS was not found.
Substantial changes in IOP occur throughout the day in patients with occludable anterior chamber angles. Narrower angle parameters are associated with greater diurnal fluctuation.
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