Spontaneous Unilateral Anterior Corneal Mosaic in Orbital Apex Syndrome: A Case Report

1. Junior Resident, Department of Ophthalmology, Guru Gobind Singh Medical College and Hospital, Faridkot, Punjab, India. 2. Junior Resident, Department of Ophthalmology, Guru Gobind Singh Medical College and Hospital, Faridkot, Punjab, India. 3. Associate Professor, Department of Ophthalmology, Guru Gobind Singh Medical College and Hospital, Faridkot, Punjab, India. 4. Junior Resident, Department of Ophthalmology, Guru Gobind Singh Medical College and Hospital, Faridkot, Punjab, India. 5. Junior Resident, Department of Ophthalmology, Guru Gobind Singh Medical College and Hospital, Faridkot, Punjab, India.

Abstract

Cornea is the transparent, avascular, outermost fibrous coat of the eyeball. Fluorescein dye is used to detect epithelial discontinuities in the cornea. In a normal cornea, there is no uptake of stain after fluorescein instillation. However, a distinct honeycomb or mosaic pattern is often observed after massaging the cornea through the lids with fluorescein staining. This pattern is known as Anterior Corneal Mosaic (ACM) and is characterised by a polygonal/honeycomb pattern on the cornea. Present case is the first case of spontaneous unilateral ACM in an eye with orbital cellulitis and orbital apex syndrome, displaying a ‘guitar-pick’ sign on Magnetic Resonance Imaging (MRI) and B-scan. In this case, a 65-year-old female patient complained of a sudden onset of decreased vision in her left eye that began one week ago. Slit lamp examination revealed chemosis and a spontaneous mosaic pattern on the cornea. Pus culture from an upper lid abscess identified Methicillin Resistant Staphylococcus aureus (MRSA). Treatment with intravenous antibiotics, abscess drainage, and topical antibiotics resulted in clinical improvement, although vision remained poor after one month. Authors hypothesise that the ACM was spontaneously induced in the absence of external pressure from the eyelids. It was likely caused by pressure on the cornea from lid swelling and increased posterior pressure due to orbital soft-tissue inflammation. Thus, it may serve as a clinical indicator of elevated orbital pressure.

Exposure keratopathy, Fluorescein staining of the cornea, Orbital cellulitis

Case Report

A 65-year-old female presented with chief complaints of diminution of vision in the left eye since one week, which was sudden in onset. She was a known diabetic and hypertensive for 2-3 years and was on treatment (Metformin 500 mg and Amlodipine 5 mg). She was examined after giving written informed consent. The examination revealed upper and lower lid oedema along with congestion and tenderness, chemosis of the conjunctiva, a non reactive pupil, loss of extraocular movements, and minimal proptosis in the left eye. The anterior segment had quiet pseudophakia, and the posterior segment showed optic disc oedema and tortuous vessels. All findings were consistent with orbital apex syndrome with total ophthalmoplegia (Table/Fig 1)a,b. Best Corrected Visual Acuity (BCVA) of the right eye was 20/30, and the left eye had no Perception of Light (PL). The right eye was normal except for mild cataractous changes. She also had inferior conjunctival exposure due to non axial proptosis displacing the left globe inferolaterally. The radiological findings suggested increased soft-tissue pressure with conical globe distortion, also known as the ‘guitar-pick sign,’ in the left orbit with a medial orbital abscess on MRI (Table/Fig 1)c (1). The B-scan of the left eye also showed globe distortion in the form of compression and straightening of the sclera into a triangle-like configuration (Table/Fig 1)d.

Slit lamp examination of the left eye revealed chemosis of the bulbar conjunctiva inferiorly (Table/Fig 1)b. Fluorescein staining was performed to assess the extent of exposure; incidentally, the cornea exhibited a mosaic/honeycomb pattern under cobalt-blue light. This pattern was observed spontaneously; there was no history of itching or rubbing the eye, and eyelid tenderness was present. The pattern appeared as a mosaic of interconnecting fluorescent lines on the corneal surface, forming multiple polygonal figures lying side by side across the entire cornea (Table/Fig 2)a. This pattern did not disappear over time and was induced without any pressure. There was no spontaneous pattern of ACM in the other eye, although it was faintly inducible by pressure on the lids and disappeared after blinking (Table/Fig 2)b.

A pus culture from the upper lid abscess revealed MRSA; no evidence of Mucor infection was found. The patient responded well to treatment with intravenous antibiotics, including ceftriaxone (2 grams), vancomycin (1 gram), metronidazole (500 milligrams), abscess drainage, and topical antibiotics (moxifloxacin eye drops 6 times daily) and lubricants. The patient was followed-up for one month, but vision remained PL negative.

Discussion

According to the best of authors knowledge, this was the first case describing spontaneous onset unilateral ACM in an eye with orbital cellulitis and orbital apex syndrome. Radiological findings on B-scan and ‘guitar-pick’ sign on MRI were suggestive of extensive soft-tissue swelling in the orbit (1). Authors hypothesise that the ACM was induced spontaneously, in the absence of any external pressure from the eyelids. It may be due to pressure on the cornea from lid swelling and increased pressure posteriorly due to orbital soft-tissue inflammation. The prominent spontaneous ACM pattern was correlated in the left eye with increased intraorbital pressure as that is the lone positive noteworthy finding in the left eye which may explain the spontaneous induction of the ACM pattern over the cornea. Rubbing of eyelids, which is a known cause of ACM pattern, also essentially increases pressure of the lid against the eyeball (2).

The ACM pattern has also been reported in patients with keratoconus, compression keratopathy, and hard contact lens wearers (3),(4),(5). Kobayashi A et al., showed that ACM disappears with progressing keratoconus due to increasing abnormalities of the Bowman’s membrane (3). At this stage, it would be too immature to suggest that ‘spontaneous ACM’ may act as a clinical indicator of increased orbital pressure, as was seen in present case. Currently, there is no protocol for altering the treatment plan based on such a finding. However, further exploration is required. Disappearance of ACM in the disease course might indicate treatment response in conditions with increased intraorbital pressure including thyroid eye disease, panophthalmitis, orbital cellulitis, orbital tumours, etc., using this cheap and simple test.

Authors emphasise that the mosaic pattern is a normal but less known finding on fluorescein staining of the cornea; which all ophthalmologists should be aware of. It consists of a mosaic pattern on the surface of the cornea seen under cobalt-blue light after lid massage that disappears after a few seconds.

Conclusion

This was the first case of unilateral spontaneous-onset ACM pattern on fluorescein staining in an eye with orbital cellulitis and orbital apex syndrome without preceding lid massage with increased intraorbital pressure depicted by the ‘guitar-pick’ sign on MRI and ultrasonography. The ACM pattern is not well-known, but it is a normal finding. It was revealed on fluorescein staining of the cornea, induced by lid massage.

DOI and Others

DOI: 10.7860/JCDR/2024/69937.19771

Date of Submission: Feb 05, 2024
Date of Peer Review: Mar 09, 2024
Date of Acceptance: Jul 12, 2024
Date of Publishing: Aug 01, 2024

AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. Yes

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ETYMOLOGY: Author Origin

ETYMOLOGY: 6