Adverse reactions to anti-glaucoma eyedrops can occur either due to the main active ingredient or from the additive agents, especially preservatives.
Preservatives extend the shelf-life of drugs and have sterilising or bacteriostatic properties.
Most preservatives also act as surfactants which destabilize bacterial cell membranes. This causes destruction of the cell membrane, inhibition of cell growth, and reduction of cell adhesiveness. However, preservatives also exert these effects on normal corneal and conjunctival cells, resulting in ocular surface disorders such as superficial punctate keratitis, corneal erosions, conjunctival allergy, conjunctival injection, and anterior chamber inflammation.
Adverse reactions to topical medications can be limited to the eye or occur systemically. The latter usually occur as the drug is absorbed through the nasal mucosa and enters the blood circulation. This is one reason why patients are advised to include the puncta when instilling the drops.
BETA BLOCKERS:
Ocular adverse reactions to β-blockers include conjunctival allergies, conjunctival injection, corneal epithelium disorders, blepharitis, and ocular pemphigoid.
Betoxolol reduces corneal sensitivity due to a local anaesthetic effect (membrane-stabilizing effect). The subsequent reduction in reflex tearing may lead to corneal epithelial disorders.
Carteolol has intrinsic sympathomimetic activity so administration of this drug does not lead to a reduced corneal sensitivity. Therefore, carteolol administration is associated with fewer cases of corneal epithelium disorders compared to other beta blockers such as timolol.
Systemic adverse reactions of the circulatory system caused by β1-blockers includes bradycardia, hypotension, and an irregular pulse. Adverse effects of the respiratory system are caused by β2-blocker activity and include worsening of asthma attacks and chronic obstructive pulmonary disease. Patients may also experience symptoms of the central nervous system, including headaches, depression, anxiety, confusion, dysarthria, hallucinations, somnolence, and lethargy.
Vasodilatation occurs with carteolol, which has intrinsic sympathomimetic activity, so adverse reactions mentioned above do not often appear after carteolol administration.
Betaxolol is a selective β1-blocker with few adverse reactions because it is the β2-blockers that affect the respiratory system.
Nipradilol is a β-blocker and an α1-blocker, but has few systemic side effects because of the weaker β-blocker activity.
PROSTAGLANDIN ANALOGUES:
Ocular adverse reactions such as
conjunctival allergy, conjunctival hyperemia, corneal epithelial disorders, and blepharitis are characteristic adverse reactions associated with prostaglandin analogs (PAs). Patients receiving these drugs might have eyelash bristling/lengthening, vellus hair, eyelid pigmentation, iris pigmentation, and deepening of the upper eyelid sulcus (DUES).
In the initial stages of treatment with PAs, patients often have intense conjunctival hyperemia, but this gradually decreases over time. A meta-analyses has shown that conjunctival hyperemia occurred significantly less often with latanoprost than with travoprost (odds ratio =0.512) or with bimatoprost (odds ratio =0.32). However, there are conflicting reports regarding which PA causes more hyperemia.
Eyelash lengthening and eyelid pigmentation appear to be the same with all PAs. Iris pigmentation often occurs in Europeans and Americans, in whom iris pigments are green-brown, yellow-brown, blue-brown, and/or of mixed color.
DUES occurred in 60%, 50%, 24%, and 18% of patients using bimatoprost, travoprost, latanoprost, and tafluprost, respectively.
In anamnestic cases involving corneal epithelium herpes, recurrent herpes was reported to occur and progress with latanoprost administration. Therefore, caution should be used when prescribing prostaglandin analogs in these patients. Macular edema has also been reported after latanoprost administration following cataract surgery.
No systemic adverse reactions have been reported with prostaglandin analog use.
CARBONIC ANHYDRASE INHIBITORS:
Ocular adverse reactions associated with carbonic anhydrase inhibitors include conjunctival allergy, conjunctival hyperemia, corneal epithelial disorders, blepharitis, Stevens–Johnson syndrome, and toxic epidermal necrosis. Dorzolamide is viscous and has a fairly acidic pH (pH =5.5–5.9), which generally causes ocular irritation. Because intraocular transitivity is slightly poor, foreign body sensation and blurred vision often occur in patients receiving brinzolamide.39 More over, carbonic anhydrase naturally exists in the corneal endothelium, and caution is needed in patients with corneal endothelial disorders.
No systemic adverse reactions were associated with topical carbonic anhydrase inhibitor use.
Ocular adverse reactions associated with parasympathomimetic drugs (Pilocarpine) included miosis-caused aphose, visual field constriction, and night vision loss. Near sightedness could also occur because of stress on ciliary muscles and patients may be conscious of haze. Ocular pemphigoid, cataract, and retinal detachment may also occur.
Systemic adverse reactions
Increases in parasympathetic nervous system activity of the internal organs may result in higher secretory gland activity and cause stress on smooth muscles. As a result, drooling, sweating, diarrhea, nausea/vomiting, stomachache, asthma, bradycardia, hallucinations and depression may occur with parasympathomimetic medication use.
SYMPATHETIC ALPHA -1 ANTAGONISTS:
Ocular adverse reactions to sympathetic α1-receptor antagonists included conjunctival hyperemia, foreign body sensation, and blepharitis.
Systemic adverse reactions to sympathetic α1-receptor antagonists included headaches and a throbbing sensation, both of which were mild.
SYMPATHOMIMETICS:
Ocular adverse reactions to sympathomimetic drugs (Dipivefrin) included burning sensation, irritation, conjunctival injection and pupil dilation. Ocular pemphigoid had also been observed in some patients and epinephrine maculopathy could occur in aphakic patients.
Systemic effects affect the cardiac system and adverse reactions include increases in systemic blood pressure, tachycardia and irregular pulse. The respiratory effects include coughing, difficulty breathing and bronchitis. Adverse reactions related to the neuropsychiatric system include sleeplessness, depression, nervousness, and trembling. Finally, digestive system reactions include gastrointestinal disorders, taste disorders, and nausea.
SYMPATHETIC ALPHA-2 ANTAGONISTS:
Ocular adverse reactions associated with long-term sympathetic α2-receptor antagonist (brimonidine and apraclonidine) use include hyperemia conjunctivae, pale conjunctiva, pupil dilation, and allergic conjunctivitis.
Systemic adverse reactions associated with long-term sympathetic α2-receptor antagonist use includes decreases in blood pressure and pulse, drowsiness, dizziness, and dry mouth.
