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Case report: Monocular diplopia after a routine optometric examination

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Dr Allan G Ared
BOptom(Hons) GradCertOcTher(UNSW) FAAO 

A 53-year-old healthy man presented for a second opinion. Immediately following a routine consultation with his regular optometrist four weeks prior, he developed symptoms of vertical monocular (R > L) diplopia. His condition worsened, leading the optometrist to refer him to a neuro-ophthalmologist for a battery of clinical and costly diagnostic tests. The patient was anxious and concerned as apart from requiring reading glasses, he had never experienced any form of serious eye problems. The patient was convinced his symptoms started after his eye examination.

Clinical details

Unaided acuities were RE 6/7.5 (ghosty) and LE 6/6 part, pinhole testing gave 6/6 in each eye. A small cylindrical refraction in each eye when trial-framed made no difference to his diplopia. The results of his topography depicted centrally swollen ­areas of epithelial islands (R > L) in the anterior corneas (Figures 1 and 2).

934  Figure 1 - F934  Figure 2 - F

Figures 1 and 2. Oculus Pentacam tangential maps depict swollen areas in the anterior cornea

The patient's posterior corneas were normal with no ectasia. Pressures were RE 21 and LE 23 (iCare rebound tonometer). When a hard contact lens was trailed in each eye, his double vision resolved instantly.

Slitlamp examination revealed a number of subepithelial whorls located centrally within the right cornea and to a lesser extent, in the left. A high-resolution Scheimpflug image revealed bilateral anterior corneal haze consistent with these examination findings (Figure 3). There was negative staining over these areas, suggesting that the likely diagnosis is early anterior basement membrane dystrophy (EBMD) or map-dot-fingerprint (MDF) dystrophy.

934  Figure 3 - F

Figure 3. High resolution Scheimpflug image reveal bilateral anterior corneal haze

Discussion

Epithelial basement membrane corneal dystrophy, also known as map-dot-fingerprint corneal dystrophy, is an inherited congenital disorder affecting the corneal epithelium and basement membrane. Characteristic clinical expression is typically exhibited after the fourth decade of life.

Secondary corneal effects include epithelial microcystic oedema, recurrent corneal erosion and visual axis involvement.1 Although this patient did not experience corneal erosions, he did present with diplopia and astigmatism. The fragility of the corneal epithelium is to be noted in these types of patients. Any form of ocular manipulation—anaesthetic eye-drops, applanation tonometry or even residual alcohol on the tonometer probe—can be enough to start the degenerative process. This is the most likely explanation for his rapid onset of symptoms.

With respect to EBMD, a progressive pathology occurs at the level of the epithelium and its corresponding basement membrane, producing an interruption of cellular integrity and tissue function.2 Resultant fluctuation or reduction in visual acuity, minimal to severe ocular discomfort or pain, epithelial oedema or more rarely, ruptured epithelial bullae, may end up becoming part of the clinical picture.

Treatment options

Treatment considerations will vary depending on the extent of corneal involvement and patient symptoms. The main strategy is to educate and reassure the patient that most cases of basement membrane dystrophy are asymptomatic and to reassure them that observation is the only necessary long-term approach.

In the event of progressive keratopathy with frequent recurrent corneal erosion, ocular surface pain or a reduction in VA, more aggressive medical or surgical treatment options may be indicated.

Non-invasive medical therapies are usually recommended initially with regular reviews to monitor and  gauge the response to therapy. In this case, a topical anti-inflammatory eye-drop was prescribed along with a gel lubricant at night to help settle some of the metabolic side-effects of the dystrophy. The patient was scheduled for ongoing reviews.

This cases demonstrates many important messages such as a probing history to deduce the initial onset of symptoms, a careful biomicroscopic examination, in particular close observation of every layer of the cornea and appropriate anterior eye imaging complemented by simple optometric tests such as an RGP trial to help confirm an effective diagnosis. In many cases, a comprehensive ophthalmic work-up can reassure the patient and potentially avoid unnecessary diagnostic imaging like MRIs and expensive neurological work-ups.

  1. Ramamurthi S, Rahman MQ, Dutton GN, Ramaesh K. Pathogenesis, clinical features and management of recurrent corneal erosions. Eye 2006; 20: 6: 635-644.
  2. Arun Verma. Recurrent Corneal Erosion emedicine (accessed September 2013)  http://emedicine.medscape.com/article/1195183-overview.


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