www.elsevier.com/locate/clae

Available online at www.sciencedirect.com

Contact Lens & Anterior Eye 31 (2008) 158–160

Case report

Corneal foreign body injury during overnight orthokeratology

lens wear: A case report§

Larry Hou-Yan Ng *

The Hong Kong Polytechnic University, School of Optometry, Hung Hom, Kowloon, Hong Kong, China

Abstract

Purpose: A case of asymptomatic corneal foreign body injury during orthokeratology lens wear is reported.

Case report: An 8-year-old Chinese female myopic child with 21 months of overnight orthokeratology lens wear experienced a corneal

foreign body injury without symptoms. The foreign body was removed and the eye treated with prophylactic antibiotic and ocular lubricant.

Orthokeratology treatment was resumed 4 weeks after initial detection and management and a small residual corneal scar remained.

Discussion: The mechanisms, differential diagnoses, management and role of neural sensitivity in corneal foreign body injury during

orthokeratology lens wear are discussed. Clinicians should be aware that subtle corneal insult may be without symptoms during prolonged

overnight orthokeratology lens wear.

# 2008 British Contact Lens Association. Published by Elsevier Ltd. All rights reserved.

Keywords: Orthokeratology; Foreign body; Asymptomatic; Hypoaesthesia; Corneal sensitivity

1. Introduction

Epithelial abrasion and staining may result when debris

flows under a contact lens or a foreign body becomes trapped

between the lens and the cornea. The pattern and severity of

the injury would vary depending on the size, shape, duration

of injury, compression pressure, and flow pattern of the

foreign bodies [1]. Among the various types of foreign body,

metallic and organic materials are usually of the greatest

concern as they may produce an antigenic response or lead to

infection. Patient symptoms can range from none to severe

eye pain. Corneal insult by entrapment of a foreign body

under a contact lens is a possible consequence of the

extended wearing of rigid contact lenses or the overnight

lens wear [2] that is commonly carried out by the majority of

orthokeratology patients.

§ This case report has been presented as a poster in the British Contact

Lens Association 30th Clinical Conference and Exhibition, Birmingham,

UK, May 2006.

* Tel.: +852 27667927; fax: +852 23625440.

E-mail address: solarry@inet.polyu.edu.hk.

1367-0484/$ – see front matter # 2008 British Contact Lens Association. Publi

doi:10.1016/j.clae.2008.01.006

The following case describes an incident of asympto-

matic metallic corneal foreign body injury to an orthoker-

atology patient.

2. Case report

An 8-year-old myopic Chinese female, LKY, with 21

months of overnight orthokeratology lens-wear experienced

an asymptomatic corneal foreign body injury. During a

regular aftercare consultation, biomicroscopy revealed an

embedded foreign body with an associated rust ring on the

temporal aspect of her left cornea (Fig. 1). Trace, diffuse,

superficial punctate corneal fluorescein staining was

observed in both eyes with no signs of infection. While

the substance of the foreign body was unknown, its rusty

appearance and the corneal rust ring suggested that it

contained iron and had been resident in the cornea for more

than 12–24 h [3].

Because foreign body removal and prescribing of

antibiotics by optometrists were not allowed under the

law of Hong Kong at the time of this patient visit, LKY was

promptly referred to an ophthalmologist for foreign body

removal and treatment. The foreign body was removed

shed by Elsevier Ltd. All rights reserved.

L.-Y. Ng / Contact Lens & Anterior Eye 31 (2008) 158–160 159

Fig. 1. Metallic foreign body on the left cornea of LKY.

Fig. 2. Corneal scar at the previous foreign body location.

under topical anaesthesia, leaving a residual scar at the site

of the incident (Fig. 2). LKY was given prophylactic

antibiotic eyedrops for a week. After discontinuation of

the medication for approximately 1 month, she resumed

orthokeratology lens wear.

Corneal sensitivity was measured after the corneal insult

using the standard protocol with a Cochet–Bonnet aesthe-

Fig. 3. The sensitivity, in nylon length (mm), at different corneal quadrants of LK

corneal sensitivity (T: temporal side; N: nasal side).

siometer [4,5] and the thresholds in both eyes were found to

differ from normative values [6]. Corneal sensitivity

measurements 3 months after resumption of orthokeratology

lens wear indicated that left eye sensitivity was the same

centrally as in all peripheral quadrants of the cornea (50 mm

nylon length). A repeat measure 12 months after the incident

demonstrated central corneal sensitivity slightly lower than

that of the peripheral cornea (Fig. 3).

3. Discussion

3.1. Corneal foreign body entrapment

The likelihood of a foreign body and its associated

corneal insult may be higher in association with the

overnight mode of lens wear practiced by many orthoker-

atology patients due to (1) minimal tear exchange taking

place during sleep because of relative immobility of the

lenses, and (2) a possible enhanced potential being present

for entrapment of foreign particles between the lens and the

cornea because of the compression of cornea tissue by the

flat lens-to-cornea relationship of the reverse geometry

lenses [7].

3.2. Corneal hypoaesthesia with lens wear

Detection of corneal foreign bodies under contact lenses

is dependent upon corneal nerve function. The wearing of

both a soft and a rigid gas-permeable contact lens has been

associated with decreased corneal sensitivity [8] and it is

reasonable to presume that a similar effect would be

expected with the overnight wearing of orthokeratology

lenses. Three possible mechanisms may contribute to

hypoaesthesia: sensory adaptation to mechanical stimula-

tion, metabolic impairment of the cornea affecting the

nerves and corneal acidosis that suppresses nerve function.

[9] While the reduction in corneal sensitivity may add to the

Y 12 months after the corneal insult. The shorter the length, the lower the

L.-Y. Ng / Contact Lens & Anterior Eye 31 (2008) 158–160160

comfort of wearers, the risk of an undetected foreign body

on the ocular surface may be increased, with the possibility

of a foreign body trapped under the lens going unnoticed by

the patient for a prolonged period of time. This reported case

of patient LKY is an example of such an asymptomatic

foreign body.

The cornea is most sensitive at its apex with a gradual

reduction toward the periphery. The average normal central

corneal touch threshold is about 50–60 mm nylon length

(diameter = 0.12 mm) by the Cochet–Bonnet aesthesi-

ometer [4–6]. Twelve months after the incident, LKY’s

central corneal sensitivity was lower than that of the

peripheral cornea (Fig. 3). Due to the lack of corneal

threshold baseline data from before the orthokeratology

procedure, it could not be concluded that the sensitivity was

actually lowered in association with the orthokeratology

contact lens-wearing treatment.

3.3. Foreign body differential diagnosis

A foreign body during orthokeratology lens wear can

appear any time during the course of treatment. Unlike

patient LKY, most incidents of foreign body entrapment

under a contact lens are associated with the symptom of at

least some sensation. Clinical conditions with symptoms

that resemble corneal foreign body injury include kerato-

conjunctivitis sicca, pterygium, filamentary keratitis, con-

tact lens induced papillary conjunctivitis, trichiasis, and

conjunctival concretions [10].

3.4. Clinical management of foreign body

The goals of managing corneal trauma from a foreign body

include removal of the foreign body particle, prevention of

infection and recurrent erosion, and the restoration of a clear

and smooth epithelial surface [11]. While superficial corneal

foreign body particles may be removed easily with a sterile

cotton wool spud or by saline irrigation, many corneal foreign

bodies require use of a foreign body spud or a 25-gauge needle

at a slit lamp under topical anaesthesia. If the foreign body is

metallic in origin and leaves a rust ring, removal of the residue

in the cornea may be accomplished by using an ophthalmic or

Alger brush drill (3). Administration of a prophylactic topical

antibiotic is appropriate in the management of any resulting

corneal epithelial defect resulting from these procedures.

Artificial lubricants containing electrolytes may also be

prescribed to promote faster corneal healing [12]. The patient

should be re-evaluated at least in 24 h after the treatment and

until complete corneal healing, evidenced by an intact

epithelium with no ocular signs of inflammation or infection,

can be documented. With a fully healed cornea, orthoker-

atology lens wear may be resumed. For mild to moderate

corneal epithelial defects it may take up to 1 week without

medication before resuming lens wear [13]. The healing time

may even be longer with more severe epithelial compromise.

4. Conclusions

Practitioners should be aware that a corneal foreign body

event can occur without symptoms in patients wearing

orthokeratology lenses on an overnight basis. Future study of

corneal sensitivity change associated with overnight

orthokeratology treatments would increase our understand-

ing of the asymptomatic nature of these events.

Acknowledgment

I would like to thank Dr. Kwok Sek Keung, MBBS (HK),

FRCS (EDIN), DO (IRE), DCH (IRE), FCO (HK), FCS

(HK), FHKAM (Ophthalmology) for his helpful medical

advice on the above case.

References

[1] White P. Contact lens complications. Part II. Contact Lens Spectrum

2000;2:34–9.

[2] Silbert JA. Anterior segment complication of contact lens wear, 2nd

ed., Butterworth Heinemann; 2000. p. 309–20.

[3] Fingeret M, Casser L, Woodcome H. Atlas of primary eyecare

procedures. Appleton Lange 1990;152–5.

[4] Krachmer JH, Mannis MJ, Holland EJ. Cornea (vol. 1): fundamentals

of cornea and external disease. Mosby; 1997, p. 279–81.

[5] Millodot M. Corneal esthesiometry. In: Eskridge JB, Amos JF,

Bartlett JD, editors. Clinical procedures in optometry. Lippincott

Williams & Wilkins; 1991. p. 371–8.

[6] Millodot M. Corneal anesthesia following contact lens wear. In:

Tomlinson A, editor. Complications of contact lens wear. Mosby-Year

Book; 1992. p. 89–101.

[7] Alharbi A, Swarbrick HA. The effects of overnight orthokeratology

lens wear on corneal thickness. Invest Ophthalmol Vis Sci 2003;44:

2518–23.

[8] Liesegang T. Physiologic changes of the cornea with contact lens wear.

CLAO J 2002;28(1):12–27.

[9] Murphy P, Patel S. The effect of long-term, daily contact lens wear on

corneal sensitivity. Cornea 2001;20(3):264–9.

[10] Sowka J, Kabat A, Lauderdale F. There’s something in my eye, doc!

Rev Optomet 2000;15(5):85–8.

[11] Onofrey B. Traumatic corneal abrasion. Contact Lens Spectrum

1998;11:50.

[12] Sclafani L. Corneal degenerations and dystrophies. Contact Lens

Spectrum 2003;8:34–9.

[13] Rhee DJ, Pyfer MF. The Wills eye manual: office and emergency room

diagnosis and treatment of eye disease, 3rd ed., Philadelphia: Lip-

pincott Williams & Wilkins; 1999. p. 23–4.