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What makes the problem more challenging is the difficulty of measuring the intraocular pressure accurately in an eye with a KPro. In the Boston KPro the stiff back plate prevents measurements based on indentation of the cornea, even in its periphery. Scleral tonometry or the use of any device acting through the lids has been highly unreliable due to often distorted or scarred tissue arrangement. Despite all of variances, finger palpation over the upper lid with the patient looking down has been shown to be the best approach to gross judgment of the IOP (Melki, Lopez and Dohlman, 2009).
The KPros are manufactured to match the refractive need of the individual patient and, therefore, a substantial inventory is required to rapidly supply a device of the desired dimensions. For the eye that is pseudophakic and approximately emmetropic, and where the IOL is left in place at surgery, a single standard power is chosen for the manufacture. For aphakic eyes of different axial lengths, devices with a varying degree of power are made in order to match a patient's needs as closely as possible. Therefore, the axial length of the individual aphakic patient is always ask for from the surgeon in order to allow the choice of a KPro that in theory best matches the dioptric requirement of the eye which is being operated on (Dohlman, Harissi-Dagher and Graney, 2007).
Indications that a patient is suitable for the Boston Keratoprosthesis include:
Two failed grafts, with poor prognosis for further grafting
Vision less than 20/400 in the affected eye
No end-stage glaucoma or retinal detachment.
The one-step that is performed in this surgery is much simpler than the procedure that is used in other Keratoprosthesis forms. Even though general anesthesia is recommended, the current trend is...
Visual improvement is usually already seen within a week (Artificial Cornea - the Boston Keratoprosthesis, n.d.).
In a study done by Ament, Stryjewski, Ciolino, Todani, Chodosh and Dohlman (2010), the cost-effectiveness of the Keratoprosthesis was determined by a cost-utility analysis, using expected-value calculations and time-tradeoff utilities. Cost-effectiveness was evaluated against recently published data on penetrating keratoplasty (PK). The average cost-effectiveness of the Keratoprosthesis was determined to be $16, 140 per QALY. Compared to corneal transplantation, with cost-effectiveness between $12, 000 and $16, 000 per QALY. Based on this the Keratoprosthesis is considered to be highly cost-effective.
References
Ament, Jared D., Stryjewski, Tomasz P., Ciolino, Joseph B., Todani, Amit, Chodosh, James and Dohlman, Claes H. (2010). Cost-Effectiveness of the Boston Keratoprosthesis. American Journal of Ophthalmology. 149(2), p. 221-228.
Artificial Cornea - the Boston Keratoprosthesis. (n.d.). Retrieved May 4, 2010, from Web site:
http://www.uic.edu/com/eye/Department/News/KeratoprosthesisInformation%20.pdf
Birkholz, Emily S. And Goins, Kenneth M. (2009). Boston Keratoprosthesis an option for patients with multiple failed corneal grafts. Retrieved May 4, 2010, from Eye Rounds
Web site: http://webeye.ophth.uiowa.edu/eyeforum/cases/94-Boston-Keratoprosthesis-Failed-Corneal-Grafts.htm
http://www.masseyeandear.org/specialties/ophthalmology/cornea-and-refractive-surgery/
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