Comparative Analysis of Human Amniotic Membrane Graft Versus Contact Lenses in Syntomathic Bullous Keratopathy

INTRODUCTION Handling of patients with severe eye surface injuries has always been challenging in the field of ophthalmology. One of the most significant pathologies causing severe injuries is Bullous Keratopathy (BK). This disorder is caused by a failure in corneal endothelial pump (Na+/K+/ATPase) characterized by chronic stromal edema, and it tends to evolve to the production of corneal vesicles and bullae due to the drainage of fluid to the anterior corneal layers as a consequence of intraocular pressure(1). Most common causes of BK are intraocular surgical procedures including those related to cataract surgery(2). This entity conforms the first cause for corneal transplant in the USA (from 26 to 50%) and the second in Europe(3,4,5).

Clinically, BK is characterized by chronic ocular pain, which is secondary to recurrent epithelial defects, ocular surface inflammation and visual sharpness decrease(1). Definitive treatment for patients with BK with remaining visual potential is corneal transplant. However, donor grafts are not always available and they often require long waiting times. For those reasons, medical and surgical palliative measures should be temporarily used to relief ocular pain. Among others, the use of therapeutic contact lenses stands out as one of the best alternatives due to its contribution to the prevention of epithelial falling and ulceration, acting as a mechanical bandage(6,7,8). These contact lenses do not improve visual sharpness neither contribute to the resolution of the problem that originated corneal edema. Besides, prolonged use of contact lenses may be associated to potential complications such as ocular disturbance, superficial neovascularization, inflammation and corneal infections, together with the economical expenses that patients have to deal with(6).

In 1940, De Roth described for the first time the use of human amniotic membrane (AM) in ophthalmology, and since that date, multiple studies guaranteed its application as an efficient treatment for ocular surface diseases(9,10, 11), including BK(12,13,14,15,16,17,18). AM is a thin membrane covering the foetal side of the placenta, and it consists of the external chorion (maternal origin) and the internal amnion (foetal origin). Histologically, it is composed of three layers: epithelium, basal membrane and stroma(19).

The therapeutic effect of the AM involves three basic synergistic actions on the ocular surface: 1) induction of growth and proliferation of new epithelia on the tissues (cornea and/or conjunctiva), 2) control of the inflammation of the tissues under the implant and 3) inhibition of fibrosis and neovascularization of the corneal stroma(19). For all these reasons AM might be an effective treatment to ameliorate disturbances generated by BK. In addition, human amniotic epithelial cells do not express HLA surface antigens, which justifies the absence of graft rejection in this type of transplants(20,21) and makes it a highly safe procedure.

In the present work, we describe the results of a randomized clinical trial in which the AM grafting technique was compared with the use of therapeutic contact lenses for the management of symptomatic bullous keratopathy in patients waiting for a corneal transplant at Carlos Van Buren Hospital from Valparaiso, Chile.