KERATOGLOBUS: A COMPREHENSIVE OVERVIEW OF THE CLINICAL FEATURES OF THE DISEASE AND ITS TREATMENT OPTIONS

To provide a synopsis of the clinical features of keratoglobus and summarize the available surgical treatment options.

Collaboration between the Ophthalmology Departments of Royal Bournemouth Hospital and Southampton General Hospital in United Kingdom.

A retrospective literature search was conducted using the following electronic platforms: i) Pubmed ii) Mendeley iii) Scopus and iv) Google Scholar. No large prospective double-blind randomized control trials specifically designed for keratoglobus exist in the literature. The literature on this rare disorder is limited to case reports or case series. All reviewed published manuscripts had major weaknesses, namely their retrospective nature, limited number of recruited eyes and limited post-operative follow-up periods. Due to the scarcity of patients suffering from this condition, it is practically very challenging to conduct large multicentre double-blind prospective studies to determine the optimum surgical management of keratoglobus.

Data for each surgical option is reported. Penetrating keratoplasty (PK) with large diameter grafts from limbus to limbus avoids graft-host junction at mid-periphery, but may increase the risk of graft rejection, limbal stem cell loss and damage to the angle structures and secondary glaucoma. Conventional epikeratoplasty provides good tectonic support with reduction in post-op refractive errors. Nevertheless, it may cause limbal stem cell disruption and persistent epithelial defect. Epikeratoplasty with 360 degree host peripheral intrastromal pocket for peripheral donor lenticule induces no limbal stem cell or angle structure disruption and provides stable host bed for possible secondary PK, but there is a higher chance of interface opacities and intraepithelial cysts. Epikeratolasty followed by PK allows better visual rehabilitation following host bed stabilisation by epikeratoplasty, but it is a 2-stage procedure. "Tuck-in" lamellar keratoplasty (TILK) provides good tectonic ability with no limbal stem cell or angle structure damage. However, it is technically much more challenging and may cause interface opacities. Pentacam-based deep anterior lamellar keratoplasty (DALK) provides detailed topographical analysis pre-operatively and decreases endothelial rejection rate but is also technically challenging. Corneoscleral rim is easy to perform, can provide good structural support and delay corneal thinning but is only a temporary measure.

Keratoglobus is a rare non-inflammatory ectatic corneal disorder with limited literature on the subject. Visual rehabilitation and preservation of the structural integrity of the cornea are the main therapeutic challenges. Various surgical techniques have been described, but no gold standard treatment exists due to the paucity in patient reports and limited follow-up of newer surgical procedures.