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Learn about topical and injectable anesthetics and mydriatics used in ophthalmic procedures. Understand dosages, onset times, and precautions for each. Discover essential information for safe and effective eye care.
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useful for diagnostic and therapeutic procedures, including tonometry, removal of foreign bodies or sutures, gonioscopy, conjunctival scraping, and minor surgical operations on the cornea and conjunctiva
Proparacaine, tetracaine, and benoxinate are the most commonly used topical anesthetics. • equivalent anesthetic potency
Note: Topical anesthetics should never be prescribed for home use, since prolonged application may cause corneal complications
Proparacaine Hydrochloride (Ophthaine) Preparation: Solution, 0.5%. Dosage: 1 drop and repeat as necessary. Onset and duration of action: Anesthesia begins within 20 seconds and lasts 10–15 minutes. Comment:Least irritating of the topical anesthetics.
Tetracaine Hydrochloride (Pontocaine) Preparations: Solution, 0.5%, and ointment, 0.5%. Onset and duration of action: Anesthesia occurs within 1 minute and lasts for 15–20 minutes. Comment: Stings considerably on instillation
Benoxinate Hydrochloride Preparation (as Fluress): Solution, 0.4%. Onset and duration of action: Anesthesia begins within 1 or 2 minutes and lasts for 10–15 minutes.
Lidocaine, procaine, and mepivacaine are commonly used local anesthetics for eye surgery. • Longer-acting agents such as bupivacaine and etidocaineare often mixed with other local anesthetics to prolong the duration of effect. • the physician must be aware of the potential systemic toxic action when rapid absorption occurs from the site of the injection, with excessive dosage, or following inadvertent intravascular injection
The addition of hyaluronidaseencourages spreading of the anesthetic and shortens the onset to as little as 1 minute. For these reasons, hyaluronidase is commonly used in retrobulbar and peribulbar injections prior to cataract extraction. • Injectable anesthetics are used by ophthalmologists most commonly in older patients, who may be susceptible to cardiac arrhythmias; therefore, l-epinephrine should not be used in concentrations greater than 1:200,000
Lidocaine Hydrochloride (Xylocaine) • Owing to its rapid onset and longer action (1–2 hours), lidocaine has become the most commonly used local anesthetic. It is approximately twice as potent as procaine. • Up to 30 mL of 1% solution, without epinephrine, may be used safely. In cataract surgery, 15–20 mL is usually more than adequate. The maximum safe dose is 4.5 mg/kg without epinephrine and 7 mg/kg with epinephrine. • Intracamerallidocaine in a 1% solution without preservatives is employed for anesthesia in cataract surgery.
Procaine Hydrochloride (Novocaine) Duration of action: 45–60 minutes.
Mepivacaine Hydrochloride (Carbocaine) Duration of action: Approximately 2 hours. Comment: Carbocaine is similar to lidocaine in potency. It is usually used in patients who are allergic to lidocaine.
Bupivacaine Hydrochloride (Marcaine, Sensorcaine) • Onset and duration of action: The onset of action is slower than that of lidocaine, but it persists much longer (up to 6–10 hours).
Etidocaine Hydrochloride (Duranest) • Onset and duration of action: The onset of action is slower than that of lidocaine but more rapid than that of bupivacaine. The duration of action is approximately twice as long as that of lidocaine (4–8 hours).
Mydriatics & Cycloplegics
Mydriatics and cycloplegics both dilate the pupil. In addition, cycloplegics cause paralysis of accommodation . • Their prime uses are (1) for dilating the pupils to facilitate ophthalmoscopy; (2) for paralyzing the muscles of accommodation, particularly in young patients, as an aid in refraction; and (3) for dilating the pupil and paralyzing the muscles of accommodation in uveitisto prevent synechia formation and relieve pain and photophobia.
Since mydriatics and cycloplegics both dilate the pupil, they should be used with extreme caution in eyes with narrow anterior chamber angles since cause angle-closure glaucoma .
Mydriatics (Sympathomimetics) • Phenylephrine Hydrochloride (Neo-Synephrine) • Preparations: Solution, 0.12%, 2.5%, and 10%. • Onset and duration of action: The effect usually occurs within 30 minutes after instillation and lasts 2–3 hours. • Comment: facilitate ophthalmoscopy, in treatment of uveitis, and to dilate the pupil prior to cataract surgery. • The 10% solution should not be used in newborn infants, in cardiac patients, or in patients receiving reserpine, guanethidine, or tricyclic antidepressants, because of increased susceptibility to the vasopressor effects • Phenylephrine is a mydriatic with no cycloplegic effect
Cycloplegics (Parasympatholytics)
Atropine Sulfate • Preparations: Solution, 0.5–3%; ointment, 0.5% and 1%. • Dosage: For refraction in children, instill 1 drop of 0.25–0.5% solution in each eye twice a day for 1 or 2 days before the examination and then 1 hour before the examination; • Onset and duration of action: The onset of action is within 30–40 minutes. A maximum effect is reached in about 2 hours. The effect lasts for up to 2 weeks . • cycloplegia in children, treatment of iritis. It is also used to maintain a dilated pupil after intraocular surgical procedures.
Toxicity: Atropine drops must be used with caution to avoid toxic reactions resulting from systemic absorption. Restlessness and excited behavior with dryness and flushing of the skin of the face, dry mouth, fever, inhibition of sweating, and tachycardia are prominent toxic symptoms, particularly in young children.
Scopolamine Hydrobromide • Preparation: Solution, 0.25%. • Dosage: 1 drop two or three times daily. • Onset and duration of action: Cycloplegia occurs in about 40 minutes and lasts for 3–5 days when scopolamine is used as an aid to refraction . • Toxicity: dizziness and disorientation, mainly in older people.
HomatropineHydrobromide • Preparations: Solution, 2% and 5%. • Dosage: For refraction, 1 drop in each eye and repeat two or three times at intervals of 10–15 minutes. • Onset and duration of action: Maximal cycloplegic effect lasts for about 3 hours, but complete recovery time is about 36–48 hours. In certain cases, the shorter action is an advantage over scopolamine and atropine. • Toxicity: Sensitivity and side effects associated with the topical instillation of homatropine are rare.
Cyclopentolate Hydrochloride (Cyclogyl) • Preparations: Solution, 0.5%, 1%, and 2%. • Dosage: For refraction, 1 drop in each eye and repeat after 10 minutes. • Onset and duration of action: The onset of dilatation and cycloplegia is within 30–60 minutes. The duration of action is less than 24 hours. • Comment:Cyclopentolate is more popular than homatropine and scopolamine in refraction because of its shorter duration of action • Occasionally, neurotoxicity may occur, manifested by incoherence, visual hallucinations, slurred speech, and ataxia. These reactions are more common in children.
Tropicamide (Mydriacyl) • Preparations: Solution, 0.5% and 1%; 0.25% with 1% hydroxamphetaminehydrobromide (Paremyd). • Dosage: 1 drop of 1% solution two or three times at 5-minute intervals. • Onset and duration of action: The time required to reach the maximum cycloplegic effect is usually 20–25 minutes, and the duration of this effect is only 15–20 minutes; therefore, the timing of the examination after instilling tropicamide is important. Complete recovery requires 5–6 hours. • Comment:Tropicamide is an effective mydriatic with weak cycloplegic action and is therefore most useful for ophthalmoscopy.
Cyclopentolate Hydrochloride-Phenylephrine Hydrochloride (Cyclomydril) • Preparations: Solution, 0.2% cyclopentolate hydrochloride and 1% phenylephrine hydrochloride. • Dosage: 1 drop every 5–10 minutes for two or three doses. • Onset and duration of action:Mydriasis and some cycloplegia occur within the first 3–6 minutes. The duration of action is usually less than 24 hours. • This drug combination is of particular value for pupillary dilation in examination of premature and small infants
The concentration used and the frequency of instillation should be individualized on the basis of tonometric measurements. Use the smallest dosage that effectively controls the intraocular pressure and prevents optic nerve damage. • All parasympathomimetics decrease intraocular pressure by increasing the outflow of aqueous humor through the trabecular meshwork.
Direct-Acting Cholinergic (Parasympathomimetic) Drugs • Pilocarpine Hydrochloride & Nitrate Comment:Pilocarpine was introduced in 1876 and is still a commonly used antiglaucoma drug. • Carbachol, Topical Comment:Carbachol is poorly absorbed through the cornea and usually is used if pilocarpine is ineffective.
Indirect-Acting Anticholinesterase Drugs • PhysostigmineSalicylate & Sulfate (Eserine) Comment: A high incidence of allergic reactions has limited the use of this old and seldom-used antiglaucoma drug. The miosis produced is extreme; ciliary spasm and myopia are common. Local irritation is common, and phospholine iodide is believed to be cataractogenic in some patients. Pupillary block may occur. Echothiophate Iodide (Phospholine Iodide) Systemic toxicity may occur in the form of cholinergic stimulation, including salivation, nausea, vomiting, and diarrhea. Ocular side effects include cataract formation, spasm of accommodation, and iris cyst formation. • Demecarium Bromide (Humorsol)
Adrenergic (Sympathomimetic) Drugs; Nonspecific • Epinephrine has the advantages of long duration of action (12–72 hours) and no miosis, which is especially important in patients with incipient cataracts (effect on vision not accentuated). • effects on both alpha and beta receptor sites. • primarily acts by increasing outflow of aqueous humor. However, it also has an ability to decrease production of aqueous humor following long-term use.
Adrenergic (Sympathomimetic) Drugs; Relatively Alpha 2–Specific • Apraclonidine Hydrochloride (Iopidine) Preparation: Solution, 0.5% and 1%. Dosage: 1 drop of 1% solution before anterior segment laser treatment and a second drop upon completion of the procedure. One drop of 0.5% solution two or three times a day as short-term adjunctive treatment in glaucoma patients receiving other medications. Comment: applied topically for prevention and management of intraocular pressure elevations after anterior segment laser procedures. It is also used as adjunctive therapy in patients on maximally tolerated medical therapy who need further reduction of intraocular pressure. Apraclonidine lowers intraocular pressure by decreasing aqueous humor formation. It may also improve aqueous outflow. Unlike clonidine, apraclonidine does not appear to penetrate blood-tissue barriers easily and produces few side effects. The reported systemic side effects include occasional decreases in diastolic blood pressure, bradycardia, and central nervous system symptoms of insomnia, irritability, and decreased libido. Ocular side effects include conjunctival blanching, upper lid elevation, mydriasis, and burning.
BrimonidineTartrate (Alphagan-P) relatively specific alpha 2 adrenergic agonist that lowers intraocular pressure by decreasing aqueous production and perhaps also by increasing outflow through the uveoscleral pathway. It has only minimal effect on heart rate and blood pressure. Preparation: Solution, 0.15%. Dosage: 1 drop two or three times daily. Frequently used as a replacement drug in patients unable to tolerate beta-blockers. Toxicity: Dry mouth, stinging, and redness are the most common side reactions.
Beta-Adrenergic Blocking (Sympatholytic) Drugs • TimololMaleate(Timoptic; Timoptic XE, Betimol) • Preparations: Solution, 0.25% and 0.5%; gel, 0.25% and 0.5%. • Dosage: 1 drop of 0.25% or 0.5% in each eye once or twice daily if needed. One drop of gel once daily. • Comment: nonselective beta-adrenergic blocking agent applied topically for treatment of open-angle glaucoma, aphakic glaucoma, and some types of secondary glaucoma. A single application can lower the intraocular pressure for 12–24 hours. Timolol has been found to be effective in some patients with severe glaucoma inadequately controlled by maximum tolerated antiglaucoma therapy with other drugs. The drug does not affect pupillary size or visual acuity. • Although timolol is usually well tolerated, it should be prescribed cautiously for patients with known contraindications to systemic use of beta-adrenergic blocking drugs (eg, asthma, heart failure).
If the lacrimal outflow system is functioning, an estimated 80% of a timolol eye drop is absorbed from the nasal mucosa and passes almost directly into the vascular system. This is called the first-order pass effect and is true for all drugs that can be easily absorbed through mucosal tissue in the head. • whereas if given orally, its first pass includes absorption via the gastrointestinal tract and then the liver, where 80–90% is detoxified before reaching the right atrium. • Cardiopulmonary histories should be taken for candidates of beta-blocker glaucoma therapy. Pulmonary function studies should be considered in patients with bronchoconstrictive disease, and electrocardiograms should be ordered on selected patients with cardiac disease. Patients with known bronchial asthma, chronic respiratory or cardiovascular disease, or sinus bradycardiamay need screening before using timolol. • The drug should be used with caution in patients receiving other systemic beta-blocking agents.
Betaxolol Hydrochloride (Betoptic; Betoptic S) Comment: Its relative 1 receptor selectivity reduces the risk of pulmonary side effects, particularly in patients with reactive airway disease. • Levobunolol Hydrochloride (Betagan) Comment:Levobunolol is a nonselective 1 and 2 blocker. • Metipranolol Hydrochloride (Optipranolol) Comment:Metipranolol is a nonselective 1 and 2 blocker . • Carteolol Hydrochloride (Ocupress)
Carbonic Anhydrase Inhibitors; Orally Administered • Inhibition of carbonic anhydrasein the ciliary body reduces the secretion of aqueous. • useful in reducing the intraocular pressure in selected cases of open-angle glaucoma and can be used with some effect in angle-closure glaucoma. • sulfonamide derivatives. Oral administration produces the maximum effect in approximately 2 hours; intravenous administration, in 20 minutes. The duration of maximal effect is 4–6 hours following oral administration. • in patients whose intraocular pressure cannot be controlled with eye drops. • They are valuable for this purpose but have many undesirable side effects, including potassium depletion, gastric distress, diarrhea, exfoliative dermatitis, renal stone formation, shortness of breath, fatigue, acidosis, and tingling of the extremities. • Since the advent of timolol, topical carbonic anhydrase inhibitors, other newer glaucoma medications, and laser therapy, systemic carbonic anhydrase inhibitors are being used less frequently.
Acetazolamide (Diamox) Preparations and dosages:Oral: Tablets, 125 mg and 250 mg; give 125–250 mg two to four times a day (dosage not to exceed 1 g in 24 hours). Sustained-release capsules, 500 mg; give 1 capsule once or twice a day. Parenteral: May give 500-mg ampules intramuscularly or intravenously for short periods in patients who cannot tolerate the drug orally. • Methazolamide (Neptazane) • Dichlorphenamide (Daranide)
Carbonic Anhydrase Inhibitors; Topically Administered • DorzolamideHydrochloride (Trusopt) Preparation: Solution, 2%. Dosage: 1 drop two to four times daily. Toxicity: Local reactions include burning and stinging, superficial punctatekeratopathy, and allergic reactions of the conjunctiva. Bitter after-taste is common. Systemic side reactions associated with oral carbonic anhydrase agents are rare. • Brinzolamide Ophthalmic Suspension (Azopt) Preparation: Suspension, 1%.
Prostaglandin Analogs • increasing outflow of aqueous humor, mainly via the uveoscleral pathway. • Latanoprost (Xalatan) • Dosage: 1 drop daily. • Travoprost (Travatan) • Bimatoprost (Lumigan) • Unoprostone Isopropyl (Rescula) • Dosage: Two drops daily. • Toxicity: All four preparations are associated with increased brown pigmentation of the iris, conjunctival hyperemia,punctate epithelial keratopathy, and a foreign body sensation. • In addition, they may aggravate ocular inflammation and have been associated with the development of cystoid macular edema.
