Unilateral corneal ectasia following trigeminal schwannoma resection with chronic neurogenic eye rubbing

Abstract

Background

Keratoconus (KC) is typically a bilateral, progressive corneal ectasia. Unilateral ectasia is uncommon and has been associated with chronic mechanical stress, such as eye rubbing. Although unilateral ectasia related to unilateral rubbing has been reported, the neurogenic driver of such behavior is less commonly highlighted. We describe a case of late-onset unilateral ectasia developing after trigeminal schwannoma resection.

Case presentation

A 50-year-old man with a history of left cerebellopontine angle schwannoma resection developed persistent left-sided facial hypoesthesia followed by chronic unilateral eye rubbing. Approximately a decade later, he noticed progressive visual decline in the left eye (OS). Examination revealed advanced unilateral ectasia in OS, with high irregular astigmatism (4.8 D), and a corneal thinnest point of 439 μm, a Fleischer ring, and severely reduced corneal sensitivity on the Cochet-Bonnet aesthesiometer. The right eye (OD) remained unaffected, with normal corneal tomography and preserved corneal sensitivity. No family history or systemic risk factors for KC were identified, supporting a localized mechanical contribution.

Conclusion

This case supports a plausible association between trigeminal nerve dysfunction, chronic unilateral eye rubbing, and subsequent corneal ectasia. It highlights the importance of recognizing neurogenic drivers of eye rubbing, performing careful ocular surface and corneal evaluation, and closely monitoring such patients for secondary corneal changes.

Highlights

• •Late-onset unilateral ectasia followed trigeminal schwannoma resection.
• •Chronic neurogenic eye rubbing followed persistent trigeminal dysfunction.
• •Cochet-Bonnet testing showed severe unilateral corneal hypoesthesia.
• •Fellow-eye tomography and BAD-D v4 showed no suspicious ectatic features.

1. Introduction

Keratoconus (KC) is a corneal disorder characterized by progressive corneal steepening and stromal thinning, leading to impaired visual function. It is typically bilateral, though often asymmetrically, with a prevalence of 1.38 per 1000 in the general population.¹

Chronic eye rubbing has been strongly linked to KC pathogenesis. Repetitive mechanical trauma contributes to corneal weakening through apoptosis and oxidative stress, compromising corneal biomechanics.²

Unilateral ectasia associated with unilateral eye rubbing has been reported sporadically, challenging the view of KC as a purely bilateral disease. However, most of these reports rely largely on retrospective patient history and do not clearly identify the underlying driver of the asymmetric rubbing behavior.³,⁴

We report a late-onset unilateral presentation of ectasia following trigeminal schwannoma resection. The novelty of this case lies in the plausibly neurogenic mechanism underlying the chronic unilateral eye rubbing after trigeminal nerve injury. It further supports the concept that sustained external biomechanical stress may contribute to the development of ectasia in a localized, highly asymmetric manner.

2. Case presentation

A 50-year-old man was referred to our clinic for progressive visual impairment in the left eye (OS) over the preceding 10 years. His medical history was notable for a large left cerebellopontine angle schwannoma, which had compressed the trigeminal nerve and was resected approximately two decades earlier. He wore spectacles and had never used contact lenses. He had no family history of keratoconus, nor allergies, atopic disease, hormonal disorders, or medication use.

Before the neurosurgical intervention, the patient reported no visual complaints in either eye. After surgery, he developed persistent left-sided facial hypoesthesia accompanied by neuropathic irritation, which led to chronic rubbing of the left eye. In the years that followed, serial neuroimaging showed no tumor recurrence. Approximately a decade after surgery, he began noticing progressive visual decline in OS. Before referral to our clinic, he had been diagnosed with unilateral dry eye in OS, presumed to explain the reduced vision, and was treated with intensive lubrication.

At presentation, approximately 20 years after the neurosurgical intervention, his best corrected visual acuity (BCVA) was 20/20 in the right eye (OD) and 20/100 in the OS. Intraocular pressure was 14 mmHg in both eyes. Corneal sensitivity was assessed using a Cochet-Bonnet aesthesiometer (0.12 mm filament), testing approximately 3 mm from the corneal center. Sensitivity measured 55 mm in OD and 5 mm in OS, findings consistent with severely reduced corneal sensation in OS.⁵ Slit-lamp examination of OS revealed a Fleischer ring, mild inferior superficial punctate keratopathy, and Vogt striae. Tear film assessment showed Schirmer's test >10 mm in both eyes. However, Tear Breakup Time was reduced in OS (4 seconds) compared to OD (7 seconds). Fundus examination was unremarkable bilaterally.

Corneal tomography (Oculus, Pentacam) showed regular with-the-rule astigmatism in OD, with central thickness of 501 μm, Kmax of 46.6 diopters, low corneal asymmetry with IS ratio of 0.57, corneal vertical coma of 0.18 μm, and a D value from the Belin/Ambrosio Enhanced Ectasia Display v3 (BAD) of 1.39 (Fig. 1, Fig. 2, Fig. 3). Supplementary review with BAD-D v4 did not identify suspicious ectatic features in OD.⁶ In contrast, OS demonstrated signs of advanced ectasia with significant inferior steepening of the anterior corneal surface, a high Kmax of 59.5 diopters, posterior bulging on the elevation map, and corneal thinning with a decentered thinnest point of 439 μm (Fig. 4, Fig. 5, Fig. 6).

Fig. 1.

Four Maps Selectable Display from Pentacam showing normal anterior and posterior corneal topography in OD.

Fig. 2.

Keratoconus display showing low corneal asymmetry and KC-related index values within normal limits in OD.

Fig. 3.

Belin/Ambrosio Enhanced Ectasia Display showing normal corneal thickness distribution with no signs of ectasia in OD.

Fig. 4.

Four Maps Selectable Display showing inferior steepening and high Kmax (59.5 D) in OS, consistent with advanced ectasia.

Fig. 5.

Keratoconus display showing elevated KC-related indices and pronounced asymmetry in OS.

Fig. 6.

Belin/Ambrosio Enhanced Ectasia Display showing posterior elevation, a decentered thinnest point (439 μm), and a high D value (7.3) in OS.

The tomographic findings were consistent with advanced unilateral ectasia in OS in the setting of chronic ipsilateral eye rubbing and trigeminal nerve dysfunction.

3. Discussion

This case describes late-onset unilateral ectasia developing in the eye ipsilateral to prior trigeminal nerve injury. Unilateral ectasia associated with unilateral eye rubbing has been previously reported.³,⁴,⁷ The distinctive feature in the present case is the plausibly neurogenic basis of the chronic unilateral rubbing behavior following trigeminal dysfunction.

Two related but distinct mechanisms should be considered. First, trigeminal nerve injury may lead to neurotrophic corneal changes, including reduced corneal sensation, impaired reflex blinking, and tear film instability, thereby compromising ocular surface homeostasis.⁸,⁹ Second, trigeminal dysfunction may also be accompanied by neuropathic irritation or dysesthesia, which can drive repetitive rubbing behavior.¹⁰ In the present case, the neurotrophic changes likely increased surface vulnerability, whereas the chronic eye rubbing represents the more plausible direct biomechanical contributor to ectasia development.

Eye rubbing is strongly implicated in KC pathogenesis and progression, contributing to corneal weakening through repetitive microtrauma, keratocyte injury, transient intraocular pressure spikes, and altered inflammatory and proteolytic signaling.²,¹¹ The striking laterality in this patient is therefore notable: the affected eye had persistent hypoesthesia, ocular surface disturbance, and chronic eye rubbing, whereas the fellow eye was tomographically normal at presentation, with no suspicious ectatic features on supplementary BAD-D v4 review. This pattern supports a localized mechanism rather than a generalized bilateral process.

At the same time, this report has important limitations. No preoperative or early postoperative corneal tomography was available, so a pre-existing subclinical or forme fruste ectatic predisposition cannot be fully excluded. Serial corneal imaging documenting the onset and progression of ectasia was also unavailable. Corneal biomechanical assessment was not performed, and inter-eye analysis of tear inflammatory cytokines or matrix metalloproteinases was also not available; therefore, biochemical mediation of rubbing-associated corneal change cannot be directly demonstrated. In addition, the history of chronic eye rubbing was retrospective and may not accurately capture its frequency, force, or duration, as eye rubbing is inherently difficult to quantify consistently.¹²,¹³

Nevertheless, the absence of family history, atopy, or allergy, the delayed onset of unilateral visual decline after trigeminal injury, and the normal fellow-eye tomography at presentation make the proposed neurogenic-mechanical sequence clinically compelling. Although keratoconus progression in older patients has been reported,¹⁴ the unilateral and ipsilateral nature of the present case remains unusual; however, this finding is consistent with previous reports of secondary ectasia.¹⁵

4. Conclusion

In conclusion, this case highlights a plausible association between trigeminal nerve dysfunction, chronic unilateral eye rubbing, and late-onset unilateral ectasia. It emphasizes the need to identify neurogenic causes of chronic eye rubbing, counsel patients to avoid persistent mechanical trauma, and monitor the cornea closely when unilateral rubbing is present. Whether preventive interventions such as corneal cross-linking have any role in such settings remains uncertain and should be considered on an individualized basis.

CRediT authorship contribution statement

Neofytos Mavris: Writing – original draft, Visualization, Methodology, Investigation, Data curation, Conceptualization. Itay Lavy: Writing – review & editing, Investigation. Renato Ambrósio: Formal analysis, Validation, Writing – review & editing. David Smadja: Writing – review & editing, Validation, Supervision.

Patient consent

This case report was conducted in accordance with the principles of the Declaration of Helsinki. The patient provided informed consent for the use of clinical data and images for publication. All identifying information has been anonymized to protect patient confidentiality.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.