The Allergic Eye: From Itch to Intervention

I have been managing diseases of the ocular surface for well over a decade, and have incorporated intense pulsed light (IPL) therapy into my practice since 2015, at a time when its application in ophthalmology was still emerging. What has become increasingly clear to me over that time is this: the allergic eye and the dry eye are rarely independent entities. They converge, compound one another, and in their most severe forms can threaten vision. Recognising where a patient sits on the allergic spectrum, and intervening at the right level, is what distinguishes adequate from excellent ocular surface care.

Understanding the Spectrum

Ocular allergy encompasses a spectrum of conditions unified by IgE-mediated mast cell activation at the conjunctival surface. At the milder end sit seasonal allergic conjunctivitis (SAC) and perennial allergic conjunctivitis (PAC), accounting for the majority of presentations. These are IgE-mediated hypersensitivity reactions triggered by airborne allergens, often pollens in the case of SAC, and dust mites and animal dander in PAC. Mast cell degranulation releases histamine, tryptase, leukotrienes, prostaglandins, and cytokines, generating the familiar clinical triad of itch, redness, and tearing.^1,2

At the more severe end of the spectrum sit vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC). VKC is predominantly a condition of childhood and adolescence, more common in males, and characterised by intense bilateral inflammation, cobblestone papillae on the upper tarsal conjunctiva, Horner-Trantas dots at the limbus, and in severe cases, corneal shield ulcers, plaques, and neovascularisation.³ AKC typically presents in adulthood with a chronic, year-round course, closely associated with atopic dermatitis, and carries significant risk of corneal scarring, cataract, and secondary infection.⁴ Both are potentially sight-threatening and require ophthalmological co-management.

Perhaps the most clinically important insight in modern ocular surface management is that allergy and dry eye disease (DED) are not mutually exclusive.

The Allergy-Dry Eye Interface

Perhaps the most clinically important insight in modern ocular surface management is that allergy and dry eye disease (DED) are not mutually exclusive. They are frequently co-existing and mutually amplifying conditions. Both share chronic surface inflammation and tear film disruption as core pathophysiological features, and each worsens the other.²

The mechanism is well described. Inflammatory mediators released during allergic mast cell degranulation disrupt goblet cell function and destabilise the tear film mucin layer, shortening tear break-up time (TBUT) and exposing the ocular surface to further allergen penetration.^2,5 Histamine binding at the conjunctival epithelium compounds this by increasing vascular permeability and neurogenic inflammation. In eyes already compromised by evaporative dry eye, the most prevalent subtype driven by meibomian gland dysfunction (MGD), the threshold for allergic reactivity is lowered: a cytokine-rich environment primes mast cells towards hyperactivation.⁶

The practical consequence is that treating allergic symptoms alone, without addressing the underlying ocular surface milieu, will yield only partial and transient relief. A patient who is prescribed antihistamine drops and continues to rub their eyes throughout spring, is also driving progressive meibomian gland distortion, tear film instability, and in the worst case, corneal ectasia. The itch is not merely a symptom; in the context of chronic allergy, it is a driver of structural disease.

A Stepwise Approach to Management

Management of the allergic eye should be guided by disease severity, the presence of comorbid dry eye, and the degree of corneal involvement. A structured, stepwise approach allows clinicians to match intervention intensity to clinical need.

For mild SAC and PAC, first-line management begins with allergen avoidance, cold compresses, and preservative-free artificial tears to dilute and clear allergens from the ocular surface. Topical dual-acting antihistamine/mast cell stabilisers, and agents such as olopatadine or ketotifen, form the pharmacological cornerstone for most patients with SAC and PAC.^1,2 These agents offer the advantage of both immediate symptom relief through H1 receptor blockade and prophylactic mast cell stabilisation with regular use. Preservative-free formulations should be prioritised wherever possible to avoid compounding ocular surface toxicity, particularly in the context of coexisting dry eye.

Short-course topical corticosteroids remain an important option for acute exacerbations or when antihistamine therapy is insufficient, but their use requires ophthalmological oversight given the risks of intraocular pressure elevation and cataract formation with prolonged use. Non-steroidal anti-inflammatory drops may provide supplementary antipruritic benefit in selected patients.

For patients with recalcitrant or moderate-to-severe disease, particularly VKC and AKC, topical calcineurin inhibitors, such as ciclosporin A and tacrolimus, have emerged as steroid-sparing immunomodulators with an established evidence base.⁷ Ciclosporin A 0.1% has received European regulatory approval for children aged four years and older with severe VKC, and its off-label use in AKC is well-supported in the literature.⁸ Tacrolimus (0.03% to 0.1%) ophthalmic ointment offers an alternative for patients who are intolerant of, or unresponsive to, ciclosporin. At the most refractory end of the spectrum, emerging data support the use of systemic biologics, such as dupilumab (an IL-4/IL-13 antagonist) and omalizumab (anti-IgE), in patients with VKC and AKC resistant to conventional immunosuppression, though these agents remain off-label for ocular indications.^8,9

Addressing the Ocular Surface: The Role of IPL and LLLT

When allergy-driven surface inflammation has compromised meibomian gland function, as is the case in a significant proportion of patients presenting with recurrent or perennial symptoms, addressing the tear film and glandular disease is integral to durable management. This is where device-based therapies have changed the clinical landscape in meaningful ways.

Intense pulsed light therapy has been part of my practice since 2015, when its application in the management of MGD-related dry eye was still in its early evidence stages. At Pure Sight Eye Surgeons, IPL has since become a cornerstone of our ocular surface program, integrated alongside medical management for patients presenting with complex allergic and dry eye disease across our Sydney clinics. In the years since, the evidence base has matured considerably. IPL works via selective photothermolysis: filtered broad-spectrum light targets the abnormal telangiectatic vessels of the periorbital skin that serve as inflammatory reservoirs, reducing the local cytokine burden, improving meibum quality and expressibility, and stabilising tear film lipid layer thickness.10,11 Multiple randomised controlled trials and systematic reviews now confirm statistically significant improvements in TBUT, ocular surface disease index (OSDI) scores, and meibomian gland expressibility following a course of IPL treatments.^11-13

In the allergic patient with concurrent MGD, IPL’s anti-inflammatory mechanism is particularly relevant: by targeting the periocular inflammatory milieu that perpetuates both meibomian gland obstruction and ocular surface sensitisation, IPL addresses pathophysiology that drops alone cannot reach. A series of four to eight treatments, combined with meibomian gland expression, is typically required for meaningful and sustained benefit, with maintenance treatments thereafter as clinically indicated.¹¹

Low-level light therapy (LLLT), or photobiomodulation, is a complementary modality that operates through a distinct mechanism: the absorption of red and near-infrared light (600–1100 nm) by mitochondrial chromophores in eyelid and conjunctival tissue, stimulating cellular energy production, reducing pro-inflammatory cytokines including IL-1β and TNF-α, and producing a clinically significant rise in eyelid temperature sufficient to liquefy inspissated meibum.^14,15 LLLT is well-tolerated, non-invasive, and can be used in patients for whom IPL may not be appropriate, including those with Fitzpatrick skin types V–VI. Evidence for combined IPL and LLLT protocols in refractory MGD-associated dry eye is emerging and clinically promising.¹⁶

It is important to note that IPL and LLLT are indicated in the chronic, stable phase of allergic eye disease, where MGD is a co-driver of surface dysfunction, not during acute inflammatory episodes where cold compresses and topical antihistamines remain the appropriate first response. IPL is most effective in patients with the evaporative subtype of dry eye and MGD as a demonstrable contributor to ocular surface disease. Careful patient selection, with meibography and TBUT assessment prior to treatment, ensures that device-based therapy is deployed where it will yield the greatest benefit.

The Consequences of Chronicity: Keratoconus and Corneal Risk

One of the most clinically important and underappreciated consequences of poorly controlled ocular allergy is the risk of keratoconus. The link is mechanical: chronic, forceful eye rubbing driven by the relentless itch of VKC, AKC, or even inadequately managed SAC, generates repeated biomechanical stress on the corneal stroma, accelerating thinning and ectatic change.^3,4 Keratoconus has been documented at significantly higher prevalence in both VKC and AKC cohorts compared to the general population, and the risk is compounded when rubbing begins in childhood, during the period of corneal development.

From an ophthalmological standpoint, this is a compelling argument for aggressive early control of itch in any patient with chronic allergic eye disease. Every consultation is an opportunity to reinforce the message: rubbing feels like relief but causes harm. Topical therapy, cold compresses, and where appropriate, device-based surface treatment should all be deployed – not merely to improve comfort, but to protect corneal integrity.

In patients with established keratoconus in the setting of atopic disease, close collaboration between the optometrist, the corneal specialist, and the allergy team is essential. Corneal crosslinking may be indicated to halt progression, but it will have limited durability if the underlying inflammatory driver – the itch and the rubbing it provokes – is not controlled in parallel.

Most patients with SAC and PAC can be well managed within the optometric or GP setting with appropriate pharmacotherapy and ocular surface support.

When To Refer and What To Expect

Most patients with SAC and PAC can be well managed within the optometric or GP setting with appropriate pharmacotherapy and ocular surface support. Referral to an ophthalmologist with a subspecialty interest in ocular surface disease should be considered when: symptoms are severe, recurrent, or unresponsive to dual-acting topical agents; there is any corneal involvement (punctate epithelial erosions, shield ulcers, neovascularisation, or ectasia); there is a suspicion of VKC or AKC; steroid therapy is being considered for more than a brief course; or concurrent dry eye with MGD is not responding to conventional management.

Device-based treatment with IPL and LLLT sits within the ophthalmologists’ and specialist optometrists’ toolkit, and referral for these modalities should not be delayed in patients who are failing to achieve adequate surface stability with drops alone. The evidence base for IPL, in particular, has matured to a point where it should be considered a standard rather than an adjunct therapy for MGD-related evaporative dry eye, and its benefits in patients with coexisting allergic disease are compelling.

The allergic eye is common, but it is not simple. Recognising the interplay between allergy, tear film dysfunction, and structural ocular risk, and building a management approach that addresses all three, is the foundation of truly effective ocular surface care.

References

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