Ophthalmic manifestations of HIV: an update

[Ocular complications of HIV infection: experience of the Northern Excellence Pole of Morocco]

INTRODUCTION

HIV infection is associated with a wide variety of ophthalmic manifestations. The objective of this study was to identify the ocular complications of HIV/AIDS in Morocco.

MATERIAL AND METHODS

A retrospective study conducted in the internal medicine department of the Rabat Teaching Hospital between 1998 and 2008. All HIV-positive patients were retained for the study. Each patient had an exhaustive ocular examination.

RESULTS

Of 115 ophthalmologic examinations, 28 were abnormal. Twenty-seven patients had stage C HIV infection and one patient was in stage A. The ocular manifestations were: 21 cases of ocular HIV-related anomalies (microangiopathies), four cases of cytomegalovirus (CMV) retinitis, one case of toxoplasmosis chorioretinitis, one case of CMV retinitis associated with toxoplasmosis chorioretinitis, two cases of Cryptococcus neoformans infection, two cases of varicella-zoster virus (VZV) retinitis, and one case of conjunctival Kaposi sarcoma. The CD4 count average was of 86±91/mm(3). Twenty-six patients had a CD4 count lower than 200/mm(3). Progression was favorable in 85 % of the cases, with three cases of blindness: bilateral in a case of VZV retinitis and unilateral in two cases of CMV retinitis and toxoplasmosis chorioretinitis.

CONCLUSION

CMV infection is the main ocular opportunistic infection in our series. However, Highly Active Antiretroviral Treatment (HAART) may be the cause for the decline in the prevalence of ocular diseases and visual impairment in HIV/AIDS.

Retinal Fundus Image Registration via Vascular Structure Graph Matching

Motivated by the observation that a retinal fundus image may contain some unique geometric structures within its vascular trees which can be utilized for feature matching, in this paper, we proposed a graph-based registration framework called GM-ICP to align pairwise retinal images. First, the retinal vessels are automatically detected and represented as vascular structure graphs. A graph matching is then performed to find global correspondences between vascular bifurcations. Finally, a revised ICP algorithm incorporating with quadratic transformation model is used at fine level to register vessel shape models. In order to eliminate the incorrect matches from global correspondence set obtained via graph matching, we proposed a structure-based sample consensus (STRUCT-SAC) algorithm. The advantages of our approach are threefold: (1) global optimum solution can be achieved with graph matching; (2) our method is invariant to linear geometric transformations; and (3) heavy local feature descriptors are not required. The effectiveness of our method is demonstrated by the experiments with 48 pairs retinal images collected from clinical patients.

Withdrawal of maintenance therapy for cytomegalovirus retinitis in AIDS patients exhibiting immunological response to HAART

BACKGROUND: Before the introduction of highly active antiretroviral therapy (HAART), CMV retinitis was a common complication in patients with advanced HIV disease and the therapy was well established; it consisted of an induction phase to control the infection with ganciclovir, followed by a lifelong maintenance phase to avoid or delay relapses. METHODS: To determine the safety of CMV maintenance therapy withdrawal in patients with immune recovery after HAART, 35 patients with treated CMV retinitis, on maintenance therapy, with CD4+ cell count greater than 100 cells/mm³ for at least three months, but almost all patients presented these values for more than six months and viral load < 30000 copies/mL, were prospectively evaluated for the recurrence of CMV disease. Maintenance therapy was withdrawal at inclusion, and patients were monitored for at least 48 weeks by clinical and ophthalmologic evaluations, and by determination of CMV viremia markers (antigenemia-pp65), CD4+/CD8+ counts and plasma HIV RNA levels. Lymphoproliferative assays were performed on 26/35 patients. RESULTS: From 35 patients included, only one had confirmed reactivation of CMV retinitis, at day 120 of follow-up. No patient returned positive antigenemia tests. No correlation between lymphoproliferative assays and CD4+ counts was observed. CONCLUSION: CMV retinitis maintenance therapy discontinuation is safe for those patients with quantitative immune recovery after HAART.

The dual-bootstrap iterative closest point algorithm with application to retinal image registration

Motivated by the problem of retinal image registration, this paper introduces and analyzes a new registration algorithm called Dual-Bootstrap Iterative Closest Point (Dual-Bootstrap ICP). The approach is to start from one or more initial, low-order estimates that are only accurate in small image regions, called bootstrap regions. In each bootstrap region, the algorithm iteratively: 1) refines the transformation estimate using constraints only from within the bootstrap region; 2) expands the bootstrap region; and 3) tests to see if a higher order transformation model can be used, stopping when the region expands to cover the overlap between images. Steps 1): and 3), the bootstrap steps, are governed by the covariance matrix of the estimated transformation. Estimation refinement [Step 2)] uses a novel robust version of the ICP algorithm. In registering retinal image pairs, Dual-Bootstrap ICP is initialized by automatically matching individual vascular landmarks, and it aligns images based on detected blood vessel centerlines. The resulting quadratic transformations are accurate to less than a pixel. On tests involving approximately 6000 image pairs, it successfully registered 99.5% of the pairs containing at least one common landmark, and 100% of the pairs containing at least one common landmark and at least 35% image overlap.