title: The impact of topical mydriatic ophthalmic solutions on retinal vascular reactivity and blood flow.
abstract: The impact of mydriatic agents on the standardized provocation of retinal vascular reactivity has not been systematically investigated. Our aim was to investigate the effect of commonly used mydriatic agents on the provoked vascular response of retinal arterioles. One eye was randomly selected for mydriasis from 10 healthy volunteers (age 23.3 ± 4.9 years). A single drop of: 1% tropicamide (T), or a combination of 0.8% tropicamide and 5% phenylephrine (TP), or 1% cyclopentolate (C) were instilled into the volunteers lower fornix at each of three visits. Volunteers underwent a standardized isocapnic hyperoxic provocation. Four retinal hemodynamic measurements were acquired with the Canon Laser Blood Flowmeter at equivalent positions on the superior temporal arteriole (STA) and inferior temporal arteriole (ITA) at baseline, during provocation and after recovery. Statistical analysis was performed using linear mixed-effect models. Pre- and post-dilation measurements indicated that pupil diameter increased with use of T, TP, C (all <0.001), while systolic blood pressure, diastolic blood pressure and intraocular pressure did not change significantly (all >0.05). In response to a standardized isocapnic hyperoxic challenge, blood vessel diameter, blood velocity and flow decreased in both the STA and ITA relative to baseline. Comparison between the change elicited by isocapnic hyperoxic gas stimuli with respect to blood vessel diameter, blood velocity, blood flow, were equivalent for each mydriatic agent in the STA (p = 0.66, p = 0.99, p = 0.99, respectively) and the ITA (p = 0.85, p = 0.80, p = 0.66, respectively). Furthermore, comparison between the change in the STA and ITA with respect to the above parameters showed equivalent responses in both vessels for each mydriatic agent: T (p = 0.92, p = 0.99, p = 0.35; respectively), TP (p = 0.89, p = 0.96, p = 0.62; respectively), and C (p = 0.87, p = 0.35, p = 0.56; respectively). The provoked retinal vascular reactivity response to standardized isocapnic hyperoxia was equivalent irrespective of the agent used to achieve mydriasis.
authors.affiliation: Department of Ophthalmology and Vision Sciences, Toronto Western Hospital, University Health Network, 399 Bathurst Street, Toronto, ON M5T 2S8, Canada.
authors.forename: Edmund
authors.initials: E
authors.lastname: Tsui
authors.forename: Mitra
authors.initials: M
authors.lastname: Sehi
authors.forename: Richard W F
authors.initials: RW
authors.lastname: Cheng
authors.forename: Jennifer
authors.initials: J
authors.lastname: Wan
authors.forename: Tien
authors.initials: T
authors.lastname: Wong
authors.forename: Stephanie
authors.initials: S
authors.lastname: Dorner
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Fisher
authors.forename: Christopher
authors.initials: C
authors.lastname: Hudson
mesh_terms: D000287:Administration, Topical; D001160:Arterioles / Q000502:physiology; D001783:Blood Flow Velocity; D001794:Blood Pressure / Q000187:drug effects; D003519:Cyclopentolate / Q000008:administration & dosage*; D004338:Drug Combinations; D005260:Female; D006801:Humans; D018496:Hyperoxia / Q000503:physiopathology*; D007429:Intraocular Pressure / Q000502:physiology; D017078:Laser-Doppler Flowmetry; D008297:Male; D009184:Mydriatics / Q000008:administration & dosage*; D009883:Ophthalmic Solutions / Q000008:administration & dosage; D010656:Phenylephrine / Q000008:administration & dosage*; D011680:Pupil / Q000187:drug effects; D012039:Regional Blood Flow / Q000502:physiology; D012161:Retinal Artery / Q000502:physiology*; D014331:Tropicamide / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D004338:Drug Combinations; D009184:Mydriatics; D009883:Ophthalmic Solutions; D010656:Phenylephrine; D003519:Cyclopentolate; D014331:Tropicamide