WHEN WE THINK of the most involved way to improve corneal clarity, full-thickness penetrating keratoplasty (PKP) often comes to mind. However, keratoplasty has limitations due to longevity, and their prognosis for success is occasionally guarded. This is when the Boston Keratoprosthesis (KPro; Mass Eye and Ear), an artificial cornea, has a place (Cherny et al, 2022).

A 47-year-old female presented to our clinic five years ago with a failing PKP for the second time. The ophthalmic history in her left eye was a retinal detachment repaired with a scleral buckle and silicone oil tamponade and two failed PKPs with neovascularization, moderate-stage glaucoma, retro corneal membranes, and hypotony. Her entering acuity was hand motion in the left eye.

The decision not to undergo a third PKP was made by the corneal surgeon due to the high probability of failure because of previous failures and corneal neovascularization. The option of a type I Boston KPro was discussed. This patient eventually went through a combined surgery removing her existing PKP and placement of a temporary KPro, removal of a retro corneal membrane, silicone oil exchange, endolaser treatment, and placement of a permanent KPro. Throughout the follow-up, many bandage contact lenses were tried and eventually the patient’s vision improved to 20/200 in her left eye (Cherny et al, 2022).

The Boston KPro was created for patients in whom the conventional full-thickness cornea transplant would not succeed (Doane et al, 1996). The corneal pathologies indicating its use are multiple graft failures, Steven-Johnson syndrome, ocular cicatricial pemphigoid, other autoimmune diseases, and ocular burns (Shihadeh and Mohidat, 2012). There are some who believe the Boston KPro to be the primary treatment for repeat graft failure and aniridia (Shihadeh and Mohidat, 2012). The literature shows a success rate of that is respectively around 94% and 90% for chemical burns and non-cicatrizing graft failures, and these eyes achieve around 20/200 vision maintained for around one year (Feldman et al, 2023).

The Boston KPro is a collar button design keratoprosthesis that consists of three components: a front plate with an optical stem, a back plate, and a titanium locking c-ring. The front and back plates are snapped together with corneal tissue in between, which is then sutured to the eye (Khan et al, 2007). Advancements to the type I design have been made since its origin, including the addition of holes in the back plate to allow diffusion of aqueous to support donor graft stroma and keratocytes, a titanium locking c-ring that was added to prevent intraocular disassembly of the device and threadless assembly, and, most recently, the implementation of a titanium back that is thought to improve biocompatibility and retention (Ament et al, 2009).

Our patient was fit with a type I Boston KPro, however, two different types exist. Type II is only used for severe end-stage ocular surface disease desiccation and requires a permanent tarsorrhaphy to be performed (Feldman et al, 2023).

The Boston KPro has proved to be an advantageous technological invention; however, it does have some negatives. KPro patients are prone to develop inflammation, retroprosethetic membranes, and cellular debris within (Feldman et al, 2023). There is an active keratoprosethetic research program in Boston, and centers all over the world are working to improve these sequelae and enhance vision.

References

1. Cherny C, Sherman S, Trief D. Contact Lens Modifications for Boston Keratoprosthesis: Novel Case Report and Review of the Literature. JCLRS. 2022 Nov;6:e9-e17. Available at jclrs.org/index.php/JCLRS/article/view/50 . Accessed Aug. 1, 2023.
2. Doane MG, Dohlman CH, Bearse G. Fabrication of a keratoprosthesis. Cornea. 1996 Mar;15:179-184.
3. Shihadeh WA, Mohidat HM. Outcomes of the Boston keratoprosthesis in jordan. Middle East Afr J Ophthalmol. 2012 Jan;19:97-100.
4. Feldman BH, Bunya VY, Woodward MA, Moon C, Klufas MA. Boston Keratoprosthesis (KPro). American Academy of Opthalmology EyeWiki. 2023 March. Available at eyewiki.aao.org/Boston_Keratoprosthesis_(KPro) . Accessed Aug. 1, 2023.
5. Khan BF, Harissi-Dagher M, Khan DM, Dohlman CH. Advances in Boston keratoprosthesis: enhancing retention and prevention of infection and inflammation. Int Ophthalmol Clin. 2007 Spring;47:61-71.
6. Ament JD, Spurr-Michaud SJ, Dohlman CH, Gipson IK. The Boston Keratoprosthesis: comparing corneal epithelial cell compatibility with titanium and PMMA. Cornea. 2009 Aug;28:808-811.