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V. Sheth, M. Blair, J. De la Cruz; Macular Optical Coherence Tomography Findings in Boston Type 1 Keratoprosthesis Patients at the Illinois Eye and Ear Infirmary. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5707.
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To evaluate the retina in post-operative keratoprosthesis patients and the usefulness of OCT in the assessment of these patients.
All Boston Type 1 Keratoprosthesis patients with retinal OCT studies were included in this series. Post-operatively, macular OCT examinations were performed using the Stratus OCT. These scans were performed between 1 day and 8 months post-operatively. The same machine and operator were used for all of the studies.
A total of 5 patients and 7 studies were included in this series. The disease process leading to keratoprosthesis placement was variable (rheumatoid arthritis, Fuchs' corneal dystrophy, chemical burn, pseudophakic bullous keratopathy after anterior chamber lens placement, and Acanthamoeba keratitis). All patients had prior failed full thickness grafts (penetrating keratoplasty). Two of five patients were pseudophakic after the procedure while three of five were left aphakic. Zero of seven scans and zero of five patients demonstrated macular edema on OCT. For each of the seven studies, one scan with the highest signal strength (SS) score was determined. The average of the maximum signal strength scores was 4.57 (range of 2.00 to 7.00). In the standard macular OCT protocol, six scans are taken of the macula. The average of these six scans was calculated for each study. The overall average of signal strength in the seven studies was 3.50 (range of 0.83 to 6.00). In patient Number 5, the keratoprosthesis eye demonstrated a maximum SS of 6.00 and an average of 4.67 while the contralateral, unoperated eye demonstrated a maximum SS of 9.00 with an average SS of 6.83.
In both phakic and aphakic keratoprosthesis patients, no macular edema was found. Signal strength (SS) appeared to be low for all post-operative keratoprosthesis patients. This is surprising as the view to the macula in these patients is very clear. Multiple variables may play a role in the poor signal strength. One possibility is that the prosthetic itself is made of PMMA, which may limit signal strength. Another possibility is that these patients are often wearing contact lenses, which may add another optical interface that may degrade the quality of the scan.Determining the cause of poor signal strength is important in finding a way to improve the quality of these studies. Better quality OCT studies would provide more accurate assessment of the macula in these patients.
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