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Assessing the Impact of Pharmacological Pupil Dilation on Anterior Chamber Cells Counting Using OCT
Priscilla Manni1, Francesco Romano2,3, Matteo Airaldi2,4,5
1Department of Sense Organs, Ocular Immunovirology Service, Sapienza University of Rome, Rome, Italy.
Purpose:
Anterior chamber (AC) cells are seen as hyperreflective dots (HRDs) on anterior segment OCT (AS-OCT), but many factors can affect their objective counting. The aim of this study was to evaluate the effect of pharmacological dilation with tropicamide 0.5% (T) or phenylephrine 2.5% + tropicamide 0.5% (PH + T) on the assessment of AC HRDs density measured in healthy eyes by AS-OCT.
Design:
Cross-sectional, observational study.
Participants:
Healthy subjects with no history of uveitis, no ocular or systemic conditions, and no recent ocular surgery.
Methods:
Participants underwent comprehensive ophthalmic examinations, including single-line AS-OCT (16.5 mm; μm:pixel ratio = 8.79; Anterion, Heidelberg Engineering) imaging before (miosis) and after pupil dilation with either T or PH + T drops. Hyperreflective dots were quantified using FIJI (National Institutes of Health, Bethesda) through the Analyze Particles tool after image binarization. Hyperreflective dot density was calculated by dividing the total HRDs by the AC area and expressed as the number per 10 000 pixels². Iris displacement after dilation was measured using the apex-to-pupil distance (APD).
Main Outcome Measures:
Anterior chamber HRDs density before and after dilation measured by AS-OCT. A generalized Poisson mixed-effects model was used to evaluate the effects of group (miosis, T, PH + T), lens status (phakic, pseudophakic), and their interaction on HRD density. Covariates included age, sex, iris color, and variation in APD after dilation (APDD).
Results:
A total of 100 eyes from 59 healthy participants (55.9% female), mean age 73.0 ± 11.7 years were included. Mean (standard deviation) HRDs density (per 10 000 pixels²) significantly increased from 0.79 (1.44) in normal photopic conditions to 1.71 (3.30) after the dilatation in the T group and from 0.52 (0.83) to 15.8 (25.8) in the PH + T group (P < 0.001). Dilation with T (P = 0.03) or PH + T (P < 0.001), increased APDD (P < 0.001), and the interaction between PH + T and phakic status (P < 0.001) were all significantly associated with higher HRDs density.
Conclusions:
Pharmacological dilation, especially with PH + T, significantly increases HRDs in the AC of healthy subjects, with a more pronounced effect in phakic eyes and greater APDD. These findings suggest increased iris-lens friction and potential pigment release after dilation, providing critical considerations for standardizing AS-OCT-based assessments of AC inflammation.
Financial Disclosures:
The author has no/the authors have no proprietary or commercial interest in any materials discussed in this article.
