Visual Fields and Retinal Nerve Fiber Layer Thickness After Boston Keratoprosthesis

Abstract

 

Purpose:

 

To assess the visual field and retinal nerve fiber layer (RNFL) thickness in patients with Boston Keratoprosthesis (KPro) using Goldmann Visual Field (GVF), Humphrey Visual Field (HVF), and Stratus optical coherence tomography (OCT).

 

Methods:

 

In compliance with the Declaration of Helsinki, a cross-sectional study was conducted of 9 patients with implanted KPro and 8 normal patients without history of glaucoma. Of 35 eyes that underwent KPro implantation from 5/04 to 10/08, 9 eyes with visual acuity better than 20/100 were selected. Of the 9 KPro patients, 4 were diagnosed with glaucoma based on optic nerve appearance. Patients underwent peripheral kinetic testing using isopters I_4e and II_4e on the Goldmann perimeter, central static testing using program 24-2 on the Humphrey Field Analyzer, and RNFL thickness measurement at the optic nerve head with Stratus OCT. Each Goldmann isopter was traced onto Photoshop, and the area was determined by calculating the number of pixels within each isopter. Statistical analysis was performed using unpaired t-tests.

 

Results:

 

Findings are summarized in Table 1. The peripheral visual fields measured with isopters I_4e and II_4e of all KPro patients (both glaucomatous and non-glaucomatous) were significantly more constricted when compared to that of normals. This difference was not significant when comparing the glaucomatous with non-glaucomatous KPro patients. The foveal threshold on HVF is significantly higher for normals than KPro eyes or non-glaucomatous KPro eyes, but there was no difference between the two KPro subgroups. The HVF mean deviation (MD) was significantly different when normals were compared to all KPro and KPro subgroups. MD was not different between glaucomatous and non-glaucomatous KPro subjects. RNFL thickness is greatest for normals and lowest for glaucomatous KPro patients, with significant differences found between normals and all groups.

 

Conclusions:

 

There is significant constriction of the peripheral visual field in KPro patients with or without glaucoma when compared to normal patients. Also noted is the relative decrease in foveal threshold and thinning of the RNFL in all KPro patients.  

 

Keywords: keratoprostheses • visual fields • imaging methods (CT, FA, ICG, MRI, OCT, RTA, SLO, ultrasound)