Observations of IV over smaller PS induced by pharmacological miosis, while not physiological, may provide useful information about the relationship of iris volume with pupillary size and the PS at which IV is the maximum in normal people. Mydriasis and light-induced miosis alone could not provide a large spectrum of PS over which changes in IV can be measured and its relationship with PS can be determined. The iris area and IV have been studied over a range of pupil size (PS) by inducing mydriasis. The measurement of IV with swept-source OCT is however more accurate. The formula for measurement of IV using AS-OCT had significant shortcomings and led to the use of iris area instead. Iris volume (IV) and its change with pupil size (PS) have been reported as an important risk factor for PACD. In order to avoid overtreatment and decrease unnecessary costs, it is important to study the mechanisms and better identify those who are at higher risk of progression. In a clinical setting, however, most PACSs receive an LPI. #Eye with no pupil trial#The Zhongshan Angle Closure Prevention Trial from China has studied the role of laser iridotomy in PACS, but the results have not yet been published. A population-based study from South India reported that, over a 5-year period, 22% (95% CI 9.8–34.2%) of PACSs progressed to PAC, while 28.5% of PAC (95% CI 12–45%) progressed to PACG. More recently, the importance of dynamic changes in the iris in PACD has also been recognized. Ultrasound biomicroscopy (UBM) and anterior segment OCT (AS-OCT) have identified ocular biometric parameters such as anterior chamber width, anterior chamber area and volume, iris thickness, iris area, lens curvature, and lens vault as risk factors. Some of the known risk factors include short axial length, a shallow anterior chamber, a thicker lens, and a more anteriorly positioned lens. PACD includes primary angle closure (PAC), primary angle-closure glaucoma (PACG), and acute attack (AAC). Primary angle-closure suspects (PACSs) are those with angles at risk for but with no evidence of primary angle-closure disease (PACD). It is estimated that there will be more than 10 million affected by PACG in China by 2020 accounting for 48% of the total number of PACG cases worldwide. Primary angle-closure glaucoma (PACG) is one of the major causes of glaucoma and blindness in China. This trial is registered with ChiCTR-ROC-17013572. The largest IV was recorded at a pupillary size between 3 and 4 mm. The relationship between PS and IV in this study was in the shape of a downward parabola. The largest IV occurred at PS between 3 and 4 mm. The relationship between PS and IV was in the shape of a downward parabola and was modeled using a quadratic equation ( y = −1.3121 x 2 + 8.8429 x + 16.423, R 2 = 0.26886). PS between 3.812 and 6.665 mm was associated with an increase in IV, while PS between 3.159 and 5.54 mm was associated with a decrease. The mean IV increased with miosis in both ME and FE in 13 eyes, IV decreased with a decrease in pupillary size. The pupillary sizes for which IV was recorded in ME and FE ranged from 1.161 mm to 6.665 mm. A scatter plot was used to depict the association between each pupil size and IV. Iris volume (IV), anterior chamber volume (ACV), anterior chamber depth (ACD), and pupil size (PS) were recorded. OCT was performed prior to and one hour after pilocarpine in both ME and fellow eye (FE). Pilocarpine 1% was instilled in a randomly selected eye (eye with induced miosis (ME)) of each participant to obtain iris volume (IV) measurements over a range of pupil sizes. 31 healthy adult Chinese volunteers underwent swept-source anterior segment OCT examination in both eyes. To determine the range of pupil size that has the largest iris volume in normal eyes.
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