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Other Ophthalmic Agents

Concise summaries of ocular antiseptics, eye wash solutions, and hyperosmotic agents used in optometric practice in Singapore — including practical guidance on pharmacology, dosing, patient selection, and referral thresholds.

Last updated: March 2026

What are these ophthalmic agents?

This page covers three distinct categories of topical ocular agent that sit outside the primary antibiotics, antivirals, anti-allergy, anti-glaucoma, and dry eye groupings, yet are encountered regularly in Singapore optometric practice. Ocular antiseptics manage surface bacterial infections and are uniquely relevant to contact lens wearers at risk of Acanthamoeba keratitis. Eye wash solutions provide first-line mechanical decontamination following irritant exposure. Hyperosmotic agents offer symptomatic relief of corneal oedema in conditions such as Fuchs' endothelial dystrophy and bullous keratopathy.

Singapore's large contact lens–wearing population and tropical climate — which promotes ocular surface exposure to particulates, pollen, and environmental irritants — make eye wash solutions a commonly reached-for OTC product. All three agents on this page are available over the counter without restriction. The ageing population increases the clinical burden of corneal oedema, while the prevalence of contact lens wear elevates the relevance of antiseptics with activity against Acanthamoeba.[1,2,3]

Drug classes

  • Ocular antiseptics (cationic diamidines) — hexamidine diisethionate (Desomedine 0.1%) disrupts bacterial and protozoal cell membranes, providing broad-spectrum antibacterial activity and clinically relevant anti-Acanthamoeba efficacy; available OTC in Singapore.
  • Eye wash solutions — distilled witch hazel 13% v/v (Optrex Multi Action Eye Wash) acts by mechanical irrigation plus mild astringency to cleanse and soothe the ocular surface; available OTC without restriction and intended for minor irritant removal rather than infection treatment.
  • Hyperosmotic agents — sodium chloride 5% (Salacyn) draws excess fluid from the oedematous corneal stroma by osmotic gradient, reducing epithelial oedema and improving visual acuity; available OTC and HSA-registered in Singapore (SIN13218P).

Who are they for?

These agents serve distinct patient populations. Optometrists in Singapore will most commonly encounter patients self-treating with Optrex for minor irritation, patients presenting with bacterial conjunctivitis or blepharitis where Desomedine is appropriate as a pharmacy-accessible antiseptic, and patients with established corneal endothelial disease managing oedema with Salacyn while awaiting or deferring surgical intervention.[4]

Patient profiles

Ocular irritation — minor (environmental)

Patients with dust, pollen, or mild foreign body irritation benefit from Optrex eye wash for mechanical flushing. It is not suitable for chemical splash (use copious sterile saline / Minims sodium chloride and refer) or for infectious conjunctivitis.

Bacterial conjunctivitis and blepharitis

Desomedine (hexamidine 0.1%) is an accessible pharmacy antiseptic for uncomplicated bacterial conjunctivitis and blepharitis in adults. Its broad-spectrum activity, including against Staphylococcus aureus, makes it suitable for mild to moderate presentations not requiring POM antibiotic drops.

Contact lens wearers — Acanthamoeba risk

Contact lens wearers presenting with disproportionate pain, photophobia, or ring infiltrate following CL-related irritation should be referred urgently. Desomedine has demonstrated in vitro anti-Acanthamoeba activity; however, suspected Acanthamoeba keratitis requires urgent ophthalmological management, not OTC antiseptic treatment alone.

Corneal oedema — Fuchs' dystrophy / bullous keratopathy

Patients with Fuchs' endothelial dystrophy, pseudophakic bullous keratopathy, or post-surgical corneal oedema use Salacyn (NaCl 5%) to temporarily reduce stromal fluid and improve visual acuity, particularly on waking when oedema is worst. Refer for definitive endothelial keratoplasty assessment.

Post-operative corneal recovery

Salacyn is used short-term following corneal surgical procedures where transient oedema reduces visual acuity. It provides symptomatic relief while the endothelium recovers — regular ophthalmology follow-up is essential.

Children — eye wash only

Optrex is labelled for use in adults and children ≥12 years. Desomedine should not be used in young children without medical advice. Salacyn is for adults. Any ocular infection in a child under 12 should be assessed by a medical practitioner rather than managed with OTC or pharmacy antiseptics.

Caution — contact lens wearers

None of these agents should be used with soft or rigid contact lenses in situ. Remove lenses before instilling Optrex, Desomedine, or Salacyn. Optrex contains benzalkonium chloride (BAK) which is absorbed by soft lens material and can cause ocular surface toxicity. Desomedine may also interact with lens polymers. Salacyn solution should not be instilled with lenses in place; the ointment formulation is for bedtime use only. Advise patients to wait at least 15–30 minutes after instillation before reinserting lenses, and to discontinue lens wear if any persistent discomfort, redness, or discharge develops.

When should they be used?

Eye wash — first-line irrigation for minor irritation

Optrex Multi Action Eye Wash is indicated for mechanical flushing of the ocular surface following exposure to dust, pollen, smoke, or other minor environmental irritants. It is not appropriate for chemical splash injuries (which require copious sterile saline and immediate referral), nor for treating established infection or allergy. If symptoms persist beyond 48 hours or worsen, refer to a medical practitioner. Do not use with contact lenses in situ — remove lenses before use and wait 15–30 minutes before reinserting.

Antiseptic — bacterial conjunctivitis and blepharitis

Desomedine (hexamidine 0.1%) is appropriate for uncomplicated bacterial conjunctivitis and blepharitis in adults when a pharmacy-accessible antiseptic is clinically suitable. It should not be used beyond 10 days without medical advice. If symptoms have not improved within 48 hours, refer for assessment — failure to respond may indicate a viral, allergic, or chlamydial aetiology, or a resistant organism requiring POM antibiotic therapy. Its anti-Acanthamoeba activity is clinically relevant as an adjunct in Acanthamoeba keratitis management, but this indication is managed by an ophthalmologist.

Hyperosmotic — corneal oedema management

Salacyn (NaCl 5%) is appropriate for symptomatic management of corneal oedema in patients with established diagnoses of Fuchs' endothelial dystrophy, bullous keratopathy, or post-surgical corneal oedema. Symptoms are typically worst on waking (when the closed-eye microenvironment increases corneal hydration); instillation on rising can meaningfully improve early morning visual acuity. It provides symptomatic relief only — patients should be referred for endothelial keratoplasty (DSAEK/DMEK) assessment when visual function is significantly compromised or quality of life is impacted.

Clinical indicationRecommended agentAction / Notes
Minor ocular irritation (dust, pollen, smoke)Optrex Multi Action Eye Wash (OTC)Bathe eye 1–2 min; repeat 1–2× daily PRN; refer if no improvement in 48 h
Bacterial conjunctivitis — uncomplicatedDesomedine 0.1% 1–2 drops 3–4× daily (OTC)Up to 10 days; refer if no improvement in 48 h
Blepharitis — lid and conjunctival antisepsisDesomedine 0.1% 1–2 drops 3–4× daily (OTC)Short course; adjunct to lid hygiene measures
Corneal oedema — Fuchs' dystrophy / bullous keratopathySalacyn NaCl 5% QID (OTC)Ongoing symptomatic use; refer for surgical assessment
Post-surgical corneal oedemaSalacyn NaCl 5% QID (OTC)Short-term until endothelial recovery; monitor under ophthalmology
Chemical splash / foreign body flushSterile NaCl 0.9% or Minims — refer urgentlyCopious irrigation; emergency referral; Optrex NOT appropriate here

Where are they available in Singapore?

All three agents on this page are General Sale (OTC) products, available without a prescription or pharmacist supervision. None require a prescription from a registered medical practitioner for patient purchase or use, though optometrists should always recommend referral when clinical findings exceed the scope of OTC management.

Scope of practice — Singapore optometrists

Under the Optometrists and Opticians Act (Cap. 213A) and regulations administered by the Optometrists and Opticians Board (OOB), Singapore-registered optometrists are authorised to examine eyes, assess visual function, and prescribe optical appliances. They do not hold the authority to prescribe or supply therapeutic medications. However, optometrists may appropriately advise patients on the use of OTC products (Optrex, Desomedine, Salacyn) as part of clinical guidance — this falls within the informational and advisory role of the optometrist, provided the clinical scenario is appropriate and a clear referral threshold is communicated.[5,6]

  • General Sale (OTC) — Optrex Multi Action Eye Wash: Available at Guardian, Watsons, Unity, and most major supermarkets and convenience pharmacies. Stocked in the eye care / eye drop aisle. No pharmacist supervision required.
  • General Sale (OTC) — Salacyn NaCl 5%: HSA-registered (SIN13218P) and distributed by Peter Chia Marketing Pte Ltd. Available at major pharmacy chains. Both solution and ointment formulations may be stocked; check availability with individual pharmacies. Confirm current registration at hsa.gov.sg.
  • General Sale (OTC) — Desomedine 0.1%: Bausch + Lomb product, available at Watsons and other retail pharmacies without a prescription. Confirm current availability and registration at hsa.gov.sg.
  • HSA product verification: Current registration status and supply classification for all products can be confirmed via the HSA product registration portal (hsa.gov.sg). Always verify before advising patients to purchase any specific product.[9]

Why are these agents clinically essential?

Each agent in this category addresses a distinct clinical need that no other product category covers. Eye wash provides a safe, immediate, non-pharmacological response to environmental irritation — an extremely common presenting complaint. Ocular antiseptics fill a clinical gap between simple lubricants and POM antibiotics, offering a pharmacy- accessible, broad-spectrum option for mild bacterial conjunctivitis and blepharitis without requiring a prescription. Hyperosmotic agents are the only OTC intervention that directly addresses corneal stromal oedema — a condition that significantly reduces visual acuity in patients with endothelial disease and for whom surgical management may not yet be appropriate or accessible.

Non-pharmacological surface decontamination

Optrex provides mechanical removal of allergens, particulates, and mild irritants from the conjunctival sac — reducing inflammatory stimulus without the risks associated with topical steroids or vasoconstrictors.

Anti-Acanthamoeba activity — unique among accessible agents

Hexamidine diisethionate (Desomedine) has demonstrated in vitro activity against Acanthamoeba cysts and trophozoites. No other readily accessible OTC ophthalmic agent in Singapore shares this property, making it uniquely relevant for contact lens wearers.

Symptomatic relief in endothelial disease

NaCl 5% (Salacyn) reduces corneal oedema by osmosis, improving visual acuity on waking — a critical quality-of-life benefit for patients with Fuchs' dystrophy or bullous keratopathy while they await or consider keratoplasty.

Accessible without prescription

All three agents are available without a POM prescription, allowing optometrists to advise patients on self-management of appropriate conditions — provided clear referral criteria are communicated when pathology exceeds OTC scope.

In the Singapore context, the large contact lens–wearing population increases the clinical relevance of Desomedine beyond its antibacterial indication — awareness of Acanthamoeba risk is an important patient safety responsibility for optometrists advising on contact lens hygiene and ocular symptoms. Similarly, the ageing population and increasing prevalence of Fuchs' dystrophy diagnosed at pre-surgical stages make Salacyn a product optometrists should be familiar with as an interim measure.[3,7,8]

How to use — patient and clinician guidance

Optrex Multi Action Eye Wash — technique

  1. Wash hands thoroughly before use.
  2. Remove contact lenses before washing the eye.
  3. Fill the eye bath cup to the marked line with Optrex solution.
  4. Tilt head forward and place the cup over the open eye. Tilt head back, keeping the cup pressed against the eye, and gently blink or roll the eye to allow thorough irrigation.
  5. Bathe the eye for 1–2 minutes. Repeat on the other eye using fresh solution in a cleaned cup.
  6. Use up to 1–2 times daily as needed. Do not reuse solution from the cup.
  7. Wait at least 15–30 minutes before reinserting contact lenses. Refer if symptoms persist beyond 48 hours or recur frequently.

Desomedine 0.1% — instillation technique

  1. Wash hands thoroughly before handling the bottle.
  2. Remove contact lenses before instillation.
  3. Tilt head back slightly and gently pull down the lower eyelid to create a pocket in the lower fornix.
  4. Hold the bottle inverted and instil 1–2 drops — avoid touching the dropper tip to the eye or eyelashes.
  5. Blink gently to distribute the drop. Apply gentle nasolacrimal occlusion (finger pressure at inner corner) for 1 minute to reduce systemic drainage.
  6. Repeat 3–4 times daily for up to 10 days. Do not use beyond 10 days without medical advice.
  7. Recap the bottle immediately. Discard 28 days after opening unless the label specifies otherwise.

Contact lens guidance

  • Optrex: Contains BAK preservative. Remove all soft and rigid lenses before use; wait at least 15–30 minutes before reinserting. Do not use while lenses are in situ.
  • Desomedine: Remove lenses before instillation. Patients with active conjunctivitis should not wear contact lenses at all until symptoms and discharge have fully resolved. Advise lens abstinence for the duration of treatment.
  • Salacyn solution: Remove contact lenses before instillation; wait at least 15 minutes before reinserting. The ointment formulation is for bedtime use only — never apply with contact lenses in situ. Transient blurred vision is expected immediately after instillation.

Monitoring and red-flag referral

  • No improvement within 48 hours (Desomedine): Refer for medical assessment — the aetiology may be viral, chlamydial, or allergic, or the organism may be resistant. Persistent purulent discharge requires swab and culture.
  • No improvement or worsening symptoms (Optrex): Refer after 48 hours. Persistent symptoms suggest an underlying pathology (infection, dry eye, blepharitis) that requires clinical assessment and targeted treatment.
  • Progressive visual loss (Salacyn): If visual acuity is declining despite regular use, refer for corneal endothelial assessment. Worsening oedema may indicate decompensating endothelium requiring keratoplasty evaluation.
  • Red flags — urgent ophthalmology referral: Significant pain (especially disproportionate to external signs), ring infiltrate on cornea, photophobia with CL wear history (possible Acanthamoeba), hypopyon, periorbital swelling, reduced visual acuity, or any corneal opacity developing during treatment.

Ocular antiseptics, eye wash, and hyperosmotic agents in Singapore

All agents listed are registered with HSA Singapore or are available through registered importers. Verify current product registration at hsa.gov.sg before advising patients to purchase any specific product.

Brand (Generic)MechanismDosingMin. AgeSide EffectsClinical Notes
Optrex Multi Action Eye WashDistilled witch hazel 13% v/v
OTC
Mechanical irrigation + mild astringent — cleanses ocular surface and soothes irritationPour solution into eye bath cup; bathe open eye for 1–2 min; repeat 1–2× daily PRNAdults; ≥12 yearsRare mild stinging; BAK preservative may irritate sensitive eyes; avoid soft CL contactFor dust, pollen, and minor irritant removal; not a treatment for infection or allergy; do not use with contact lenses in situ; refer if symptoms persist beyond 48 h
DesomedineHexamidine diisethionate 0.1%
OTC
Cationic diamidine antiseptic — disrupts bacterial cell membranes; broad-spectrum antibacterial and anti-Acanthamoeba activity1–2 drops 3–4× daily; do not use beyond 10 days without medical adviceAdults; consult doctor for childrenTransient stinging on instillation, mild conjunctival irritation; rare hypersensitivityBacterial conjunctivitis, blepharitis, keratoconjunctivitis; anti-Acanthamoeba activity clinically relevant for CL wearers; refer if no improvement in 48 h or symptoms worsen
SalacynSodium chloride 5%
OTC
Hyperosmotic agent — draws fluid from oedematous corneal stroma by osmotic gradient1–2 drops QID; effect is temporary; use regularly for symptomatic reliefAdultsTransient stinging and burning on instillation; temporary blurred visionCorneal oedema in Fuchs' dystrophy, bullous keratopathy, post-surgical; symptoms typically worse on waking; refer for definitive management if progressive

Legend

POMPrescription Only Medicine — Sold or supplied to the public on prescription only.
PPharmacy Medicine — Sold or supplied from any licensed retail pharmacy under pharmacist supervision.
OTCGeneral Sales List (GSL) — Sold or supplied to the public without restriction.

Dosing reflects standard adult or indicated doses unless noted. Always refer to the approved product insert for full prescribing information. OD = once daily, BD = twice daily, TID = three times daily, QID = four times daily. PRN = as needed.

References

  1. [1] Stapleton F, Keay L, Edwards K, et al. The incidence of contact lens-related microbial keratitis in Australia. Ophthalmology. 2008;115(10):1655–1662. PMID: 18538404.
  2. [2] Dart JKG, Radford CF, Minassian D, Verma S, Stapleton F. Risk factors for microbial keratitis with contemporary contact lenses: a case-control study. Ophthalmology. 2008;115(10):1647–1654. PMID: 18597850.
  3. [3] Labbé A, Baudouin C. Hexamidine diisethionate in the treatment of Acanthamoeba keratitis. J Fr Ophtalmol. 2009;32(3):178–183. PMID: 19345485. [French]
  4. [4] Elliott DB. Clinical Procedures in Primary Eye Care. 4th edn. Amsterdam: Elsevier; 2014.
  5. [5] Republic of Singapore. Optometrists and Opticians Act 2007 (No. 16 of 2007). Singapore Statutes Online. Available at: sso.agc.gov.sg/Act/OOA2007 (accessed March 2026).
  6. [6] George PP, Chng OSY, Siow K, et al. Is there scope for expanding the optometrist's scope of practice in Singapore? A survey of optometrists and opticians. Cont Lens Anterior Eye. 2019;42(3):258–264. PMID: 30819628.
  7. [7] Gain P, Jullienne R, He Z, et al. Global survey of corneal transplantation and eye banking. JAMA Ophthalmol. 2016;134(2):167–173. PMID: 26633035.
  8. [8] Aldave AJ, Han J, Frausto RF. Genetics of the corneal endothelial dystrophies: an evidence-based review. Clin Genet. 2013;84(2):109–119. PMID: 23662880.
  9. [9] Health Sciences Authority Singapore. Register of Therapeutic Products. Available at: hsa.gov.sg (accessed March 2026).

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