Gradual decrease in vision in a contact lens wearer

Examination of the patient’s right eye found corneal epithelial and subepithelial haze, superficial limbal injection and conjunctival tissue extending down through the visual axis.

Issue: October 15, 2006

A 16-year-old boy was referred to the cornea service at the New England Eye Center for evaluation and management of decreasing vision in the right eye. He recalled that the symptoms first appeared about 3 weeks before presentation and seemed to be progressing over time. The decline in vision was not associated with any scotoma, but more of a generalized haziness over his vision. The patient denied pain, but he noted some foreign body sensation, particularly when he removed his contact lenses. He did not feel that his left eye had been involved. He was a soft contact lens wearer, currently using Opti-Free Express solution (Alcon) for storage and disinfection, and he changed his contacts approximately every 3 weeks. He admitted to wearing his contacts for extended periods, approximately 15 hours each day. He adamantly denied ever wearing the contacts while sleeping.

Shazia Ahmed

My Hanh T. Nguyen

The patient’s ocular and medical history was otherwise unremarkable, and he was on no medications.

Examination

The patient’s visual acuity was 20/80 in the right eye and 20/30 in the left. His contact lens prescription was –4.00 D in the right eye and –4.25 D in the left. Manifest refraction was unable to improve his current visual acuity. IOP by applanation was 11 mm Hg bilaterally. Pupils were equally reactive without an afferent pupillary defect. Visual fields by confrontation were intact. On slit lamp examination, the conjunctiva was white and quiet bilaterally, with the exception of fine perilimbal injection in the superior quadrant of the right eye. The cornea and conjunctiva did not show any fluorescein or rose bengal staining in either eye. However, a fine corneal epithelial and subepithelial haze was present, greater in the right eye than in the left (Figures 1a and 1b). On retroillumination, a fine neovascular network was seen extending inferiorly from the superior limbal edge, as well as ridges of thin conjunctival tissue entering the central visual axis (Figures 2a and 2b).

Color photographs of the right (1a) and left (1b) eyes. Note the fine epithelial and subepithelial haze overlying the cornea, greater in the right eye than the left.

Retroillumination of the right eye. There is superficial limbal injection (2a) and conjunctival tissue extending down through the visual axis (2b).

Images: Hsu T and colleagues

What is your diagnosis?

Visual loss

With the recent news focus on fungal keratitis in contact lens wearers, we are reminded that the differential diagnosis of a patient experiencing visual loss and wearing contact lenses must include an infectious etiology, both bacterial and fungal. There are some features about this case that argue against this mechanism, namely the lack of pain or epithelial defect and definitive infiltrate. This is by no means a certain criterion, and the cornea should be followed carefully with corneal cultures performed as appropriate. From the infectious standpoint, it is important to also recognize the possibility of herpetic keratitis and begin treatment with antivirals and steroids as needed.

The other major category of disorders to be considered falls under a mechanical etiology. Specifically, some of these disorders include superior limbal keratoconjunctivitis, contact lens-induced keratitis and limbal stem cell deficiency. In our patient, there was not a strong reaction in the superior conjunctiva. The velvety appearance characteristic of superior limbal keratoconjunctivitis was lacking. Furthermore, there was an absence of rose bengal staining over the conjunctiva. As for contact lens keratitis, this is certainly a priority on the differential list. Contact lens-related keratitis can cause a wide variety of findings, including epithelial defects, infiltrates, iritis and frank hypopyon. It cannot be ruled out in this case and undoubtedly is contributing to a portion of the patient’s symptoms. However, a more likely diagnosis exists.

Discussion

So what did our patient have? This is a case of limbal stem cell deficiency, a defect in the regenerative stem cells residing in the limbal region. Limbal stem cells play a critical role in the maintenance of ocular health in two fashions. As their name implies, these are true stem cells, capable of self-renewal as well as of differentiation into terminal cell lines. From their position at the limbus, these cells provide the epithelial cells that migrate over time to cover the anterior surface of the cornea. In addition, the limbal stem cells provide a mechanical barrier between the bulbar conjunctiva and the clear cornea, preventing conjunctival overgrowth into the visual axis. Without a healthy population of limbal stem cells, these functions begin to deteriorate, with an increase in patient discomfort and visual loss. Common causes include chemical trauma, such as alkali exposure, inflammatory changes, such as Stevens-Johnson syndrome, and ocular cicatricial pemphigoid and mechanical destruction from contact lens use. In our patient, the last condition appears to be the culprit.

As mentioned above, the stem cells play a critical role in maintaining surface integrity. A lack of stem cells often results in persistent, recurrent or nonhealing epithelial defects. The constant regrowth of defective epithelium leads to an irregular corneal surface and tear film, exacerbating dry eye symptoms. Corneal neovascularization and scarring often accompany severe cases, leading to permanent visual impairment. With the loss of the mechanical barrier between the conjunctiva and cornea, conjunctival tissue containing goblet cells frequently migrates onto the cornea in a process termed “conjunctivalization.” These ridges of tissue are clearly seen in our patient, confirming the diagnosis.

Treatment

Treatment options for limbal stem cell deficiency are limited. Fortunately, conservative measures show a marked degree of success, provided that a majority of stem cells remain viable. Copious lubrication, coupled with a discontinuation of contact lens wear, can often allow the remaining limbal stem cells to divide and repopulate the deficient region. If the degree of cell loss is severe, such as with alkali burns, it becomes impossible for the remaining stem cells to adequately resupply the demands of the cornea. In these cases, limited success with autologous or allogeneic limbal stem cells has been shown. Rejection of transplanted tissue is a major limitation of this technique. Recently, however, promising results have been obtained by coupling the limbal stem cells with amniotic membrane grafting, which by its immunomodulatory effects, as well as its supply of growth factors, was able to maintain a high success rate.

For our patient, a prolonged course of contact lens discontinuation, along with artificial tear gel application four times daily, was sufficient to achieve a smooth corneal surface, disappearance of the conjunctivalization and replenishment of the limbal stem cells.

For more information:

Tom Hsu, MD, Andrew Robinson, MD, and Michael Raizman, MD, can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; Web site: www.neec.com.

Edited by Shazia Ahmed, MD, and My Hanh T. Nguyen, MD. Drs. Ahmed and Nguyen can be reached at New England Eye Center, Tufts University School of Medicine, 750 Washington St., Box 450, Boston, MA 02111; 617-636-4219; fax: 617-636-4866; Web site: www.neec.com. Drs. Ahmed and Nguyen have no direct financial interest in the products mentioned in this article, nor are they paid consultants for any companies mentioned.

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