Evaluating the accuracy of the visual field index for the Humphrey Visual Field Analyzer in patients with mild to moderate glaucoma.

PURPOSE: To evaluate the accuracy of the visual field index (VFI) for the Humphrey Visual Field Analyzer in a population of patients with mild to moderate glaucoma. DESIGN: Retrospective cohort study. METHODS: The study included 42 patients (61 eyes) with at least 11 years of follow-up, and annual automated visual fields (VFs). Patients with mean deviations ≤-20 dB were excluded. All unreliable fields were omitted (fixation losses ≥20%, false-positive ≥15%, false-negative ≥33%). The VFs were divided into two 5-year series and the data were analyzed by the new Humphrey Visual Field Analyzer software. Projected VFIs from the first 5 years were compared with observed values obtained from the last 5 years. Unreliable fields initially excluded were reintroduced into the series (22 eyes) to create a comparison. RESULTS: Predicted VFIs were accurate with a mean overestimation of VF deterioration of 1.37% (95% CI: -0.22%, 2.96%). Of the predicted values, 95% were between -4.5% and 5.2% of the observed values when the predicted VFI was ≥90%; and between -13.8% and 20.5% when the predicted VFI was <90%. No statistical difference was found between the reliable and unreliable series (mean difference of 0.09% [95% CI: -0.41%, 0.59%]). CONCLUSION: The new software for the Humphrey Visual Field Analyzer projects an accurate value for patients when the predicted VFI is ≥90%. Clinicians should consider the limitations of the software, especially for those patients with greater initial VF loss.

Histopathology in a dissecting conjunctival filtering bleb.

CASE REPORT: Four years after trabeculectomy, a patient developed unilateral tearing and presented with an ipsilateral conjunctival filtering bleb that had dissected into the cornea. The corneal portion of the bleb was excised for symptomatic relief. Histopathological examination disclosed dissection of the conjunctival filtering bleb into the cornea between Bowman's layer and the corneal epithelium. The internal portion of the bleb consisted of loose stromal tissue lacking any internal epithelial lining. COMMENTS: A conjunctival bleb dissecting into the cornea is a well-described late complication of trabeculectomy; however, its pathophysiology remains controversial. The subepithelial dissection plane in this specimen supports the concept that the conjunctival filtering bleb may dissect into, as well as "overhang", the limbal cornea.