Phenylephrine Ophthalmic Use

Phenylephrine

• Sympathomimetic that acts directly on alpha-1 receptors, inducing iris dilator contraction.
• Little or no effect on beta receptors
• Used to contract the iris dilator and blanch conjunctival blood vessels.
• Vasoconstriction narrows aperture by Müller muscle contraction
• Helps break posterior synechiae (max 10% used), may lower IOP
• Minimal effect on accommodation / cycloplegic effect
• Maximal dilation occurs in 45-60 minutes, with recovery in 6-7 hours
• Darker irises are harder to dilate due to non-specific binding.
• Formulated with tropicamide (0.25, 0.5, 0.8%)
• Pregnancy Category C

Phenylephrine ADRs

• Transient discomfort, lacrimation, keratitis, and pigmented aqueous floaters are ocular adverse reactions
• May cause increased intraocular pressure, risk of angle closure, rebound miosis, conjunctival congestion and hypoxia.
• Systemic adverse reactions (10%): HTN, tachycardia, occipital headache, subarachnoid hemorrhage.
• Can also cause ventricular arrhythmia, reflex bradycardia, and blanching of skin.
• Systemic atropine may increase the pressor effect
• Interactions with TCAs and MAO-Is
• Use caution in patients with HTN, cardiac disease, advanced arteriosclerosis, aneurysms, and insulin-dependent diabetes.

Hydroxy-amphetamine

• Indirect alpha-1 agonist triggers norepinephrine release from third-order sympathetic neurons
• Mydriasis and vasoconstriction take effect after 60 minutes, onset in 15 mins
• Similar effectiveness to 2.5% phenylephrine
• For use with cholinergic antagonist (tropicamide)
• Locates lesions in Horner syndrome when dilation indicates intact third-order neuron
• Minimal cycloplegic effect and Category C pregnancy status

Hydroxy-amphetamine ADRs

• Not systemically absorbed like phenylephrine
• Has a minor pressor effect, but can trigger tachycardia and arrhythmia when administered systemically.
• May be useful for those with insulin-dependent diabetes, as well as idiopathic orthostatic hypotension
• Contraindications are similar to that of phenylephrine (i.e. patient has HTN, tachycardia, taking MAOIs and TCAs).

Cocaine

• Naturally occurring reuptake inhibitor for norepinephrine
• Potentiates adrenergic activity
• Causes mydriasis within 15-20 minutes
• Vasoconstriction and anesthesia properties
• Excellent for breaking synechiae.

Cocaine ADRs

• Can cause lid rise, epithelial erosion, anesthesia, and angle closure.
• CNS stimulant that may cause excitement, restlessness, irregular pulse, headache, convulsions, and/or death
• Quickly systemic through mucous membrane,
• Detectable in urine for up to 2 days

Atropine

• Occurs naturally
• Cycloplegic
• Mydriasis is maximized at 30-40 minutes and lasts up to 10 days
• Cycloplegia is maximized at 60-180 minutes with effects lasting 7-12 days
• Can be used for diagnostic cycloplegic refraction and therapeutic uveitis

Atropine therapeutic uses

• Breaks posterior synechiae during uveitis in order to control pain and stabilize blood aqueous barrier thus reducing inflammation.
• Can be used for amblyopia and myopia control (0.05%)

Atropine ADRs

• Can cause irritation/stinging and contact dermatitis in the eye
• Could increase the risk for acute angle closure, and light sensitivity
• Can also cause dry mouth, facial flushing, fever, and inhibition of sweating
• Impairs vision due to cycloplegia and dilation, CNS effects
• Fatal dose: Adults (100mg) and infants (10mg)

Scopolamine

• Non-selective antagonist
• Sedative and antiemetic
• Penetrates blood brain barrier
• Sensitivity to atropine can warrant use
• Max effect noted about 30 minutes after administering

Scopolamine Clinical use

• Effects on accommodation and dilation last 3-7 days
• Can be used to treat motion sickness and uveitis
• Canada does not have scopolamine available as its own formulation
• Homatropine: 1/10th as potent as atropine
• Effects noted 40-60 minutes after administering with mydriasis enduring 1-3 days. Affects of accommodation lasts 1-6 days.
• Has been used for AC uveitis Tx. Rarely used for cycloplegia in kids

Homatropine ADRs

• Ocular and systemic
• ADR similar to atropine

Cyclopentolate

• Max cycloplegia combined with mydriasis occur about 30-60 mins after administering. Effects last ~24 hours
• Used to approximate cycloplegia for diagnostic cycloplegic refractive procedures
• Short term for anterior uveitis

Cyclopentolate ADRS

• Ocular issues like stinging/irritation
• Facial rash and lacrimation are possible
• Toxic keratitis and hyperemia reported
• Risk of increase IOP leading to ACG may occur
• Systemic: Similar to atropine, but with more CNS effects cerebellar dysfunction, hallucination, drowsiness, ataxia, and disorientation
• Inc risk to neurologically impaired or inc. dosing

Cycloplegic Potency

• Atropine has more cycloplegic action than scopolamine, which has more than homatropine

Tropicamide

• Better mydriatic than cycloplegic
• Maximal effect occurs as soon as 20-40 minutes
• Recovery within 4-6 hours (0.25 days)
• Primary diagnostic agent for pupillary dilation when examining the fundus
• Not a treatment option

Tropicamide ADRs

• Transient stinging and irritation
• Short term IOP increase of about 4-12mmHg.
• Increases risk of angle closure in narrow angles
• Rare systemic effects
• Minimal vasopressor effects: Safe for neonates/patients with HTN or angina

Dapiprazole

• Works to block receptors to iris dilator muscle
• Reverses phenylephrine and tropicamide.
• Decreased miosis in IOP
• ACG reversal is possible

Dapiprazole Adverse Affects

• Burning
• Red Eyes.
• Itching.

Pilocarpine

• Stimulates iris sphincter muscles.
• Blurry vision develops, with difficulty in dark adaptation.
• Red eye and pupillary block also
• Effects acute cardiac failure and bronchial asthma.
• Used with presbyopia and to reverse dilation
• Induces headache, dizziness, nausea when used

Proparacaine

• Discomfort and ADRs reduced
• Effects are about 15min
• BAK, but still less ADRs than other similar products

Proparacaine Adverse Affects

• Vasodilation
• Stinging can be common.
• Allergy reaction, but generally safe
• Corneal thickness increase is possible

Tetracaine

• Greater stinging effect.
• Can cause allergy
• Preserved with chlorabutanol.

Tetracaine Adverse Affects

• Vasolidation in common
• Red Tearing
• Epithelial desquamation

Lidocaine

• Amide
• Can cause arrhythmia
• Use epinephrine to counter effects

Sodium Fluorescein

• External uses include the fitting of contacts with observation, detecting corneal problems, lacrimal testing and applanation tonometry
• Hypersensitivity
• Alters soft contact lenses
• Causes skin staining

Rose Bengal

• Stains dead cells
• Used when Lissamine is not available
• Used with dye eye detection
• It will sting

Lissamine

• Similar to Rose Bengal
• Stains more than Rose Bengal

Indocyanine

• A fluorescent dye which is water soluble
• Binds to proteins
• Can view choroidal vasculature behind blood