A 58-year-old Caucasian female presented with a history of trying to clean a dark spot on her ceiling using a household cleaner which she splashed onto the ceiling and obviously into her eye while looking up. She visited the local hospital emergency unit where she received a tube of Maxitrol^® ointment (antibiotic steroid combination) and instructions to make an appointment with an eye care practitioner as soon as possible. She arrived at our office two days after the injury occurred, in lots of pain and desperate for help. Her eye was hyperaemic and she had lost more than 60% of the corneal epithelium as well as a large chunk of the conjunctival epithelium in the 7h00 to 8h00 bulbar area (Figure 1). 

Visual acuity was 6/60- and she was not quite lucid after taking a number of self-prescribed pain killers. IOP was measured with the rebound tonometer at 15mm Hg in both eyes. Case history revealed that the cleaner contained a 5% solution of ammonium hydroxide, an alkaline solution. A diagnosis of a grade 1 alkaline burn was made. In grade 1 burns the injury is usually confined to the corneal and conjunctival epithelium, the cornea is clear, and there is no limbal ischaemia^{[1, 2]}. Visual prognosis is therefore excellent. Treatment consisted of copious irrigation with normal saline for 30 – 45 minutes to normalise the pH, the fornixes were swept, cycloplegic drops were instilled, a soft bandage lens (Acuvue Oaysys®) inserted to alleviate pain and promote epithelial healing, and a topical fluoroquinolone antibiotic drop prescribed q2h. The patient was seen daily to monitor the condition and to replace the lens ^[3]. The sequence of photographs show the eye at initial presentation, two days later, six days later, and at complete resolution of the injury (Figures 1 – 4 ).

Discussion

Ammonium hydroxide results in a corrosive injury to the mucous membranes of the eye due to the alkaline pH and the hygroscopic nature of ammonia. Alkali chemicals are lipophillic and penetrate cell membranes, including those of the cornea, readily through saponification of membrane lipids^[2]. Hydroxyl ions, which are common to many alkaline chemicals, denature the collagen matrix of the cornea, which further facilitate chemical penetration^[1]. Potent alkalis can reach the anterior chamber within 15 seconds damaging structures such as the trabecular meshwork, lens and ciliary body^[1]. Affected tissues may undergo liquefaction necrosis in which the inflammation triggers the release of proteolytic enzymes, leading to a cascade of damage^[2]. Chemical damage to the conjunctiva can lead to scarring, symblepharon, cicatrical ectropion or entropion, and destruction of the limbal stem cells, which leads to neovascularization and opacification of the cornea^[1]. Glaucoma can arise from damage to the trabecular meshwork and the structures of the anterior segment^{[1, 2]}. The classification of the injury depends on the extent of conjunctival, corneal, and limbal ischaemic damage^{[1, 2]}. The degree of limbal ischaemia (blanching) must be carefully investigated and fluorescein should be instilled to determine the extent of corneal and conjunctival damage^[2]. The major treatment goals that are important throughout the healing phases are: re-establishment and maintenance of an intact and healthy corneal epithelium, control of the balance between collagen synthesis and collagenolysis, and minimising the adverse sequelae that often follow a chemical injury^[2]. Acute phase treatment includes a broad spectrum topical antibiotic, cycloplegic and anti-glaucoma therapy^{[2, 3]}.

Bandage lenses

Cornelius Celsus, in the first century A.D., was the first to apply a honey-soaked linen bandage to the eye after a pterygium excision to prevent the formation of symblepharon^[4]. During the 1880s Eugene Kalt fitted a keratoconus patient with a therapeutic lens ^[4]. With the advent of pHEMA material in the 1970s, soft contact lenses could be successfully used as bandage lenses ^[5]. Bandage contact lenses are fitted to protect the cornea, reduce pain, improve vision when the corneal shape is distorted, and to promote corneal healing in a pain free environment^[4].

Pain from corneal injury can be severe and disabling. In the past, pressure patching in conjunction with medial therapy (antibiotics and cycloplaegics) were extensively used to alleviate pain and prevent secondary infection, when treating these injuries. However, pressure patching is rarely necessary and should not be used if the injury is from vegetative matter, finger nail scratches, or contact lenses^[3]. Extended wear bandage contact lenses can be used to treat corneal abrasions, but concurrent use of prophylactic antibiotics are advocated to avoid microbial keratitis and the patient should be followed up on a daily basis for evaluation and lens replacement if necessary^[3]. Bandage contact lenses decrease trauma to the fragile epithelium caused by the constant movement of the eyelid and provide a smoother surface and lubrication by an even tear film for the pain free healing of the epithelium^[6]. By protecting the exposed nerve endings from exposure and the shearing effects of the eyelid, pain and discomfort is significantly reduced ^{[4, 6]}. Bandage contact lenses in conjunction with a topical antibiotic should be used for several days until epithelial coverage and adhesion is obtained. Patients must be followed up daily until the epithelium has healed, and then as required, until the lens is no longer required and the cornea is completely healed^[3].

Indications for bandage or therapeutic lenses

• Management of unusual or distorted corneal shapes – keratoconus, pellucid marginal degeneration and iatrogenic ectasia^[6].
• Management of corneal surface disorders such as filamentary keratitis, Thygeson’s superficial punctate keratitis, and superior limbic keratitis^[6].
• For pain relief by providing a barrier between the damaged corneal epithelium, exposed corneal nerves, and the eye lid^{[4, 6]}.
• Management of recurrent corneal erosions^{[4, 6]}
• Management and treatment of infectious trophic and autoimmune-related corneal ulcers such as Mooren’s ulcer^[6].
• Management of dry eye and keratoconjunctivitis sicca^{[4, 6]}.
• Post surgically in phototherapeutic keratectomy (PTK), photorefractive keratectomy (PRK), laser sub-epithelial keratomileusis (LASEK), laser-assisted in situ keratomileusis (LASIK), corneal crosslinking (CXL) ^{[4, 6]}.
• Management of small aqueous leaks following surgery as well as bleb complications^{[3, 6]}
• As drug delivery systems to the eye ^{[4, 6]}.

Contraindications for therapeutic contact lens wear

The single most important contraindication against the use of a contact lens is corneal anaesthesia^[6]. If a significant decrease in corneal touch sensitivity occurs, the eye does not tolerate the contact lens well and can develop significant inflammation and potential corneal infiltration. Another relative contraindication is significant lagophthalmos or lid-position abnormality^[6]. The localized drying of the contact lens can cause mechanical irritation and abrasion on the surface of the eye, as well as significant discomfort^[4]. Contact lenses can alter the normal ocular surface and tear film significantly^[7]. In situ, contact lenses divide the tear film into pre- and post-lens films. This compartmentalisation impacts the tear film in a number of ways, affecting both the biophysical and biochemical properties of the tear film ^{[8, 9]}. Lens wear can deplete the tear layer of specific components and stimulate the biochemical generation of additional components such as albumin or inflammatory mediators^[9]. Another controversial issue is the alteration of the microbial flora of the normal conjunctiva with contact lens use^[10]. Normally the bacterial diversity of the conjunctiva is higher than that in the skin. However, Shin et al., 2016 showed that the diversity of the eye microbiota of lens wearers is lower than that of non-wearers, resembling more closely the microbiota of the skin under the eye^[7].

Because there is an increase in the risk of infectious keratitis with therapeutic lenses^[3], topical antibiotics should be considered for prophylaxis when using a therapeutic contact lens. In conditions, in which a therapeutic lens is left in place for an extended period of time, removing the lens periodically and cleaning it with solutions to avoid protein and microbial build up, is the best course of action ^[6].

Which lens should be used?

If the therapeutic goal is protection and healing of the corneal epithelium, epithelial or stromal oedema should be avoided, and the selection of a high-Dk/t silicone hydrogel lens is the best choice ^[11]. If the goal is surface protection as well as stimulation of stromal wound vascularisation, selection of allow-water content, thick, hydrophilic lens is the better option^[11]. If the patient is prone to lens loss or requires frequent replacement of the therapeutic lens, a prudent economic decision is to select a daily disposable moderate-water content lens ^[11]. Patients who have dry eye, may benefit from a higher-water content lens if adequate unpreserved tear supplementation is provided with or without punctal occlusion ^[11]. Not all of the available lenses are FDA approved for therapeutic use, and therefore such wear is considered an off-label use. Make sure that the patient is informed of the goal of therapy as well as the benefits and risks of therapeutic contact lenses ^[11].

Conclusion

Alkaline eye injuries are true ocular emergencies and should be managed with great care^[2]. In this specific case the injury was confined to the cornea and conjunctival epithelium and there was no limbal ischaemia. This was probably due to the fact that the patient immediately rinsed her eye with water and visited the emergency unit at the local hospital where more irrigation was performed. Although she was treated with a topical antibiotic steroid combination, the epithelial damage resulted in severe pain, which we managed using a bandage contact lens. Due to the limited nature of the damage her prognosis was good and she fully recovered. However, alkaline burn complications may present weeks after the initial injury and she continued to be monitored for a few weeks after resolution to rule out any sequelae^[1].

References

1. Hemmati HD, Colby KA. Treating Acute Chemical Injuries of the Cornea American acadamy of ophthalmology; 2012.
2. Singh P, Tyagi M, Kumar Y, Gupta KK, Sharma PD. Ocular chemical injuries and their management. Oman Journal of Ophthalmology. 2013;6:83-6.
3. Gerstenblith AT, Rabinowitz MP. Wills Eye Manual: Office and Emergency Room Diagnosis and Treatment of Eye Disease: Wolters Kluwer; 2012.
4. Efron N. Contact Lens Practice E-Book: Elsevier Health Sciences; 2016.
5. Mandell RB. Contact Lens Practice. 4th ed: Charles C. Thomas; 1988.
6. Shah C, Raj CV, Foulks GN. The evolution in therapeutic contact lenses. Ophthalmol Clin North Am. 2003;16:95-101, vii.
7. Shin H, Price K, Albert L, Dodick J, Park L, Dominguez-Bello MG. Changes in the Eye Microbiota Associated with Contact Lens Wearing. mBio. 2016;7:e00198-16.
8. Craig JP, Willcox MDP, Argüeso P, Maissa C, Stahl U, Tomlinson A, et al. The TFOS International Workshop on Contact Lens Discomfort: Report of the Contact Lens Interactions With the Tear Film Subcommittee. Investigative Ophthalmology & Visual Science. 2013;54:TFOS123-TFOS56.
9. Mann A, Tighe B. Contact lens interactions with the tear film. Exp Eye Res. 2013;117:88-98.
10. Larkin DF, Leeming JP. Quantitative alterations of the commensal eye bacteria in contact lens wear. Eye (Lond). 1991;5 ( Pt 1):70-4.
11. Foulks GN, Harvey T, Raj CV. Therapeutic contact lenses: the role of high-Dk lenses. Ophthalmology clinics of North America. 2003;16:455-61.