Browsing by Author "Smit, Derrick Peter"

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    An investigation into the causes of intraocular inflammation in HIV-positive and HIV-negative patients in the Western Cape Province, South Africa
    (Stellenbosch: Stellenbosch University, 2018-03) Smit, Derrick Peter; Meyer, David; Stellenbosch University. Faculty of Health Sciences. Dept. of Surgical Sciences. Ophthalmology.
    ENGLISH SUMMARY: The causes of intraocular inflammation are divided into 3 large groups namely infectious, non-infectious and idiopathic. This research project set out to establish the prevalence of these 3 large groups and their different subgroups in an effort to determine whether HIV infection plays an important role in how frequently they occur in the Western Cape Province. Out of a total of 106 participants with uveitis enrolled in this study, 66 cases (62.3%) were HIV- and 40 (37.7%) HIV+ with a median CD4+ cell count of 242 x 106/l. The majority of participants were black (n=52; 49.1%) or of mixed ethnicity (n=49; 46.2%) and 59.6% of blacks were HIV+ versus 16.3% of mixed ethnicity participants. Anatomically, most cases were either anterior uveitis (58.5%) or panuveitis (32.1%) while infectious uveitis (n=70; 66.0%) was more common than non-infectious (n=18; 17.0%) or idiopathic (n=18; 17.0%) uveitis. An infectious cause was found in 80.0% of HIV+ cases versus 57.6% in HIV- cases. Intraocular tuberculosis (IOTB) was the most common cause of infectious uveitis in this study (n=35; 33.0%) where possible IOTB (n=23; 21.7%) was more common than probable IOTB (n=12; 11.3%). Tuberculin skin testing alone was more sensitive (90.3% vs 85.7%) and had a higher negative predictive value (92.1% vs 81.5%) than QuantiFERON alone and the latter therefore does not warrant the extra expense in our highly endemic setting. Herpetic uveitis formed the second largest group (n=13; 12.2%) with VZV (53.8%) responsible for more cases than CMV (38.5%) and HSV (7.7%). Syphilis was the third most common cause of infectious uveitis (n=11; 10.4%). Using a novel immunoblot approach the study investigated the relationship between ocular and neurosyphilis and demonstrated that these 2 conditions do not always co-exist. HIV infection was present in 31.4% of IOTB cases, 61.5% of herpetic cases and 81.8% of syphilitic cases. Toxoplasma (n=4; 3.8%), Rubella virus and poststreptococcal uveitis (n=3; 2.8% each) as well as HIV-induced uveitis (n=1; 0.9%) were responsible for the remainder of the infectious uveitis cases. EBV was often identified on multiplex PCR (n=11; 10.4%) but no evidence of active intraocular replication or antibody production was found to prove that EBV caused uveitis in these cases. In most cases an alternative treatable cause of uveitis was identified (n=9; 81.8%). Sarcoidosis and HLA-B27 associated anterior uveitis (n=8; 7.5% each) were the most common causes of non-infectious uveitis. All patients with ocular sarcoid and 75% of patients with HLA-B27 uveitis were HIV-. The percentage of idiopathic cases in this study was lower than in many similar studies (n=18; 17.0%). This is likely due to the high percentage of cases of possible IOTB diagnosed using a recently proposed classification as many of those cases would have been labelled as idiopathic in other studies. The majority of idiopathic uveitis cases were HIV- (n=12; 66.7%). This study revealed that infectious uveitis is the commonest form of uveitis in both HIV+ and HIV- patients but that the specific pathogens differ between patients with and without HIV infection.
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    Polymerase chain reaction to search for Herpes viruses in uveitic and healthy eyes : a South African perspective
    (Makerere University, Faculty of Medicine, 2015) Laaks, Debbie; Smit, Derrick Peter; Harvey, Justin
    Objective: To analyse aqueous polymerase chain reaction (PCR) results in patients diagnosed with undifferentiated uveitis and determine prevalence of herpesviridae in non-uveitic patients undergoing routine cataract extraction. Design: Retrospective comparative case series and prospective cross-sectional study. Subjects: 72 patients with idiopathic uveitis and 57 surgical patients. Methods: Diagnostic aqueous paracentesis with PCR testing for 6 herpes viridae in uveitic patients. Anterior chamber paracentesis immediately pre-operative in the prospective arm, with PCR testing. Results: In the retrospective review we had a 47.2% positive PCR yield. Data analysis revealed a statistically significant correlation between a positive yield and being HIV+ (p=0.018); between an EBV+ yield and being HIV+ (p= 0.026) and a CMV+ result and being HIV+ (p=0.032). Posterior uveitis (p=0.014) and symptoms <30 days (p= 0.0014) had a statistically significant yield. In the prospective arm of the study: all 57 patients were HIV- and all aqueous samples were negative for the 6 herpesviridae. Conclusion: We recommend PCR testing for Herpesviridae as a safe second line test for patients with undifferentiated uveitis. We were unable to establish prevalence and suggest that the idea of a commensal herpes virus is unlikely if the blood-ocular barrier is intact