RESEARCH Effect of cyclopentolate versus tropicamide on anterior segment angle parameters in three refractive groups Clin Exp Optom 2020 DOI:10.1111/cxo.13103 Nasrin Moghadas Sharif* † MSc Nasser Shoeibi ‡ MD Maryam Heydari † MSc Negareh Yazdani* † MSc Somayeh Ghasemi-moghaddam † MSc Asieh Ehsaei †§ PhD *Student Research Committee, Mashhad University of Medical Sciences, Mashhad, Iran † Department of Optometry, School of Paramedical Sciences, Mashhad University of Medical Sciences, Mashhad, Iran ‡ Eye Research Centre, Mashhad University of Medical Sciences, Mashhad, Iran § Refractive Errors Research Centre, Mashhad University of Medical Sciences, Mashhad, Iran Email: ehsaeia@mums.ac.ir Submitted: 28 February 2020 Revised: 7 May 2020 Accepted for publication: 12 May 2020 Clinical relevance: Frequent clinical application of cycloplegia in clinical practice makes it essential to assess how this condition influences anterior segment angle parameters. Background: This study aims to compare the effects of cyclopentolate and tropicamide on anterior segment angle parameters in three adult refractive groups. Methods: Sixty healthy individuals were recruited and assigned into three refractive groups according to inclusion criteria. At baseline visit, anterior segment angle parameters were measured using anterior segment optical coherence tomography in the right eye. All mea- surements were repeated at two separate visits, one week apart, after administration of tropicamide 1% and cyclopentolate 1% at similar conditions. Main outcome measures were angle-opening distance, trabecular iris angle, trabecular iris space area and anterior cham- ber depth. Anterior segment angle parameters were recorded at temporal areas (180 degrees). Results: Sixty participants (29 men and 31 women, age: 27.82  4.71 years) completed the experiment. Baseline mean spherical equivalents were +1.52  1.20 D, -0.04  0.33 D and -1.91  0.91 D in hyperopic, emmetropic and myopic groups, respectively. No statistically significant differences were found between tropicamide and cyclopentolate for all angle parameters in three refractive groups. Both drops induced an increase in all parameters in three refractive groups. Analysis between refractive groups revealed that a more hyperopic refraction was associated with less trabecular iris angle, angle-opening distance and ante- rior chamber depth parameters in baseline, after tropicamide and cyclopentolate instillations. Conclusions: Topical application of cycloplegic eye drops in healthy individuals leads to small but significant changes in anterior chamber depth and anterior segment angle param- eters, regardless of refractive status. Moreover, lower values of anterior chamber depth and anterior segment angle parameters in hyperopic individuals after administration of cycloplegic drops should be taken into account during biometric measurement and phakic intraocular lens implantation. Due to shorter effect and recovery time and less ocular/sys- temic reaction of tropicamide versus cyclopentolate, tropicamide could be a recommended cycloplegic agent for diagnostic and therapeutic procedures. Key words: anterior segment angle, cyclopentolate, optical coherence tomography, tropicamide Topical eye drops inducing both mydriasis and cycloplegia are primarily used for comprehensive ocular examinations in outpatient clinics and during surgery, refraction, and in treatment of some ocu- lar diseases including amblyopia and cor- neal traumas. Furthermore, they may be used in the management of uveitis to pre- vent synechia. 1 Atropine, cyclopentolate and tropicamide are the most commonly used cycloplegic drops. These anticholinergic drops block the action of the sphincter muscle of the iris and the ciliary muscles of the crystalline lens to cholinergic stimulation. 2,3 After adminis- tration, many changes occur in anterior chamber angle, anterior chamber depth, iris thickness/volume and pupil dilation, hence causing accommodation inhibition. 4,5 Atropine is the gold standard for complete cycloplegia; however, a long duration of action and severe side effects limit its clinical application. In contrast, cyclopentolate and tropicamide provide temporary cycloplegia and mydriasis with shorter duration of action compared with atropine and are widely used in clinical practice. 6 Cyclopentolate has an onset of action of 30–45 minutes and dura- tion of action of 24 hours. Tropicamide is another short-acting cycloplegic agent with an onset of action of 15–30 minutes that per- sists for up to four to six hours. 2 The assessment of anterior segment parameters is an important part of ophthal- mic practice. Slitlamp biomicroscopy with Goldman 3-mirror lens attachment has been traditionally employed for anterior chamber angle assessment. However, newly developed devices such as swept-source © 2020 Optometry Australia Clinical and Experimental Optometry 2020 1 CLINICAL AND EXPERIMENTAL