Battling The Buldge : Tackling A Case Of Extreme Corneal Ectasia

To describe the approach and surgical management of severe Terriens marginal corneal degeneration with a innovative technique - Peripheral Annular Sclerokeratoplasty ( PALK ) 

A 28 year old woman presented to our clinic with high myopic astigmatism in both eyes. Examination shoed severe peripheral corneal thinning extending circumferentially associated with extreme central corneal thinning.Vascularisation in the periphery confirned the diagnosis of Advanced Terriens marginal corneal degeneration ( TMCD ) in both eyes. 

She had a best corrected visual acuity of 20/250 in BE with -18 D Cylinder and - 17 D cylinder at 90 degrees in the right and left eyes respectively 

Management options in these cases include patient education and advocating use of protective glasses to prevent the risk of perforation secondary to trivial trauma. Spectacles and contact lenses can be considered for visual rehabilitation. However  in our patient due to the severe thinning, contact lens fitting was not feasible. The patient was unable to tolerate scleral lenses and this led us to consider a surgical alternative in the form of Peripheral Annular Scleroplasty ( PALK ).

A annular lamellar dissection was done on the host cornea in the periphery. A large diameter doughnut shaped sclerocorneal donor graft was prepared by trephining out the central 8 mm. Lamellar dissection was done to thin out the peripheral ring and this was sutured on the host with two concentric rows of interrupted sutures. This technique of PALK provides tectonic support to the peripheral thin cornea and central flattening. The patient recovered well with tomography showing central flattening and a uncorrected visual acuity of 20/50 in the operated eye. 

Terries marginal corneal degeneration is a rare disorder characterised by progressive thinning of the peripheral cornea which starts superiorly and slowly progresses circumferentially to involve the entire periphery.It presents with high against the rule astigmatism and patients should be counselled about the distinct possibility of corneal perforation secondary to trivial trauma  due to severe ectasia.Traditional surgical options include conjunctival flaps, crescentric lamellar keratoplasty and full thickness corneoscleral grafts. However their long term outcomes are not very satisfactory .A modified technique of PALK can provide good anatomical and functional outcomes with reduced complications in cases of extreme corneal ectasia.