INTRODUCTION

A corneal descemetocoele is characterised by a protrusion of the cornea as a result of an erosion of the corneal stroma leaving only the Descemet’s membrane. A descemetocoele is a sequella of amongst others: corneal ulcer, traumatic, infectious or inflammatory conditions.

PATHOPHYSIOLOGY

Essentially, a descemetocoele involves herniation or anterior bulging of an intact Descemet’s membrane through a defect of the overlying corneal stromal and epithelial layers. Descemetocoele is known to follow: infectious (bacterial, viral, fungal), inflammatory (collagen vascular diseases: RA, SLE, IBD, sarcoidosis), Mooren’s ulcer, trauma (penetrating, surgical, chemical injury), other (keratoconus,Terrien’s marginal degeneration, Pellucid marginal degeneration, keratoconjuncitivis sicca, vitamin A deficiency, ocular cicatricial pemphigoid, Stevens Johnson Syndrome, Sjogren’s syndrome, graft-versus-host disease, conditions.

MANAGEMENT

Descemetocoele is identified by observing the Descemet folds at the base of the corneal ulceration and areas of thinning. The descemetocoele needs to be resolved urgently to prevent corneal perforation and uveal prolapse. Uveal prolapse or a positive Seidel test are definitive for confirming the diagnosis of corneal perforation. This is accompanied by a flat/shallow anterior chamber. The Seidel test can be performed with a sterile fluorescein strip that is saturated with a small amount of sterile saline and painted over the suspected area of perforation. A positive Seidel test results in the dilution of the fluorescein dye in the anterior chamber when viewed under cobalt blue light. Sometimes, uveal prolapse may result in plugging of the defect resulting in a negative Seidel test and a formed anterior chamber. Tonometry is a very important diagnostic tool when managing descemetocoele. Here, the good old fashioned, non-contact tonometer works better than the Goldmann applanation tonometer, because it decreases the risk of spreading infection and avoids ocular pain caused by the applanation contact prism. You have to compare the IOP’s of both eyes. In the case of secondary glaucoma, the IOP in the eye with the descemetocoele will be elevated. A significantly low IOP (for example, 4mmHg) indicates corneal perforation.

The failure to diagnose this condition can result in further corneal damage, loss of anterior chamber integrity, secondary glaucoma, cataract development, endophthalmitis, profound vision loss and ultimately loss of the eye.

The choice of treatment will depend on the underlying disease in addition to the size, extent of stromal involvement, location of the perforation and visual potential. Multiple treatments are often employed at the same time or in a staged process. Also, treatments of descemetocoeles and corneal perforations range from temporary or short-term solutions to more definitive repair.

The optometrist can play a significant role in the management of corneal descemetocoele. An extended wear bandage contact lens (BCL) stops injuries or irritations that come from outside of the eye (such as shearing and rubbing of eyelids against the lesion). In addition, it provides a more stable environment underneath the contact lens to allow new epithelium to regenerate more easily. This treatment is useful in non-infectious impending or small corneal perforations or lacerations that have good apposition of edges and alignment, and no prolapse of uveal tissue. This can also be useful in peripheral defects or dry eye cases related to aqueous deficiency. For corneal penetrating wounds, soft, hydrophilic contact lenses are kept in place for 7 days, closing off the leak initially by epithelialisation and later by scar formation. Contact lenses can be kept in place for longer periods of time if needed and used in conjunction with topical (preferably) and/or systemic antibiotics and topical aqueous suppressant medications.

Frequent lubrication and punctal occlusion can promote re-epithelialisation in cases of aqueous deficient dry eye related corneal ulceration and impending corneal perforation.

Referral to an ophthalmologist is warranted for further management. Corneal gluing with cyanoacrylate glue or fibrin glue can be considered for impending corneal perforations or frank corneal perforations that are small (< 3 mm), concave, and located away from the limbus. Gluing is also a useful technique as a temporary measure for infectious perforations to allow for antimicrobial treatment prior to more definitive management with penetrating keratoplasty. Cyanoacrylate glue has the advantage of being bacteriostatic and longer lasting than fibrin glue. It is also believed to inhibit polymorphonuclear lymphocytes and the production of collagenases, which may halt the corneal melting process. Penetrating keratoplasty are reserved for large corneal perforations (> 3 mm) not amenable to other treatments, flat anterior chamber with iris prolapse, or failure of medical treatment or corneal gluing. Immunosuppressive agents, such as oral or topical cyclosporine, systemic methotrexate, cyclophosphamide, rituximab or infliximab, may be helpful to control the underlying disease process in cases of progressive non-infectious corneal ulceration, secondary to corneal inflammatory diseases.

CLINICAL PEARLS

• Corneal ulceration starts with a defect in the corneal epithelial layers that can progress to involve the stroma and ultimately to full thickness corneal perforation. A positive Seidel test usually indicates corneal perforation. Also, look for flat or shallow anterior chamber.
• Care should be taken to minimise pressure on the globe while examining the patient with suspected descemetocoele or corneal perforation.
• Bandage contact lens (BCL) can promote corneal healing and re-epithelialisation by protecting new epithelial cells from repeated disturbances from eyelid blinking and eye movements.
• Topical and/or systemic antibiotics are often used for prophylaxis or therapeutically in cases of infections. Aqueous suppressant topical medications can reduce intraocular pressure, decrease outflow from the site of defect and encourage healing in cases where the anterior chamber is formed.
• Steroids may help dampen inflammation by blocking the entry of polymorphonuclear lymphocytes and prevent the accumulation of collagenases and ultimately promoting re-epithelialisation and possibly improving final best-corrected visual acuity by reducing scarring.
• Steroids are contraindicated in fungal and HSV keratitis.

CONCLUSION

Corneal descemetocoele formation is characterised by bulging cornea, sudden drop in visual acuity, intense ocular pain and anterior chamber malformation. It requires prompt treatment to prevent corneal perforation and significant visual morbidity.

REFERENCE

1. Kanpolat A, Uçakhan OO. Therapeutic use of Focus Night & Day contact lenses. Cornea. 2003 Nov;22(8):726-34.
2. Ralph RA. Tetracyclines and the treatment of corneal stromal ulceration: a review. Cornea. 2000 May;19(3):274-7.
3. Brodovsky SC, McCarty CA, Snibson G, Loughnan M, Sullivan L, Daniell M, Taylor HR. Management of alkali burns : an 11-year retrospective review. Ophthalmology. 2000 Oct;107(10):1829.
4. Davis AR, Ali QK, Aclimandos WA, Hunter PA. Topical steroid use in the treatment of ocular alkali burns. Br J Ophthalmol. 1997 Sep;81(9):732.
5. Srinivasan M, Mascarenhas J, Rajaraman R, Ravindran M, Lalitha P, Glidden DV, Ray KJ, Hong KC, Oldenburg CE, Lee SM, Zegans ME, McLeod SD, Lietman TM, Acharya NR; Steroids for Corneal Ulcers Trial Group. Corticosteroids for bacterial keratitis: the Steroids for Corneal Ulcers Trial (SCUT). Arch Ophthalmol. 2012 Feb;130(2):143.
6. Vote BJ, Elder MJ. Cyanoacrylate glue for corneal perforations: a description of a surgical technique and a review of the literature. Clin Experiment Ophthalmol. 2000 Dec;28(6):437-42.
7. Gandhewar J, Savant V, Prydal J, Dua H. Double drape tectonic patch with cyanoacrylate glue in the management of corneal perforation with iris incarceration. Cornea. 2013 May;32(5):e137-8.