Lens Opacity and Hydrogen Sulfide in a New Zealand Geothermal Area.

PURPOSE: Hydrogen sulfide (H2S) is a highly toxic gas with well-established, acute irritation effects on the eye. The population of Rotorua, New Zealand, sited on an active geothermal field, has some of the highest ambient H2S exposures in the world. Evidence from ecological studies in Rotorua has suggested that H2S is associated with cataract. The purpose of the present study was, using more detailed exposure characterization, clinical examinations, and anterior eye photography, to more directly investigate this previously reported association. METHODS: Enrolled were 1637 adults, ages 18 to 65, from a comprehensive Rotorua primary care medical register. Patients underwent a comprehensive ophthalmic examination, including pupillary dilation and lens photography to capture evidence of any nuclear opacity, nuclear color, and cortical and posterior subcapsular opacity. Photographs were scored for all four outcomes on the LOCS III scale with decimalized interpolation between the exemplars. H2S exposure for up to the last 30 years was estimated based on networks of passive samplers set out across Rotorua and knowledge of residential, workplace, and school locations over the 30 years. Data analysis using linear and logistic regression examined associations between the degree of opacification and nuclear color or cataract (defined as a LOCS III score ≥2.0) in relation to H2S exposure. RESULTS: No associations were found between estimated H2S exposures and any of the four ophthalmic outcome measures. CONCLUSIONS: Overall, results were generally reassuring. They provided no evidence that H2S exposure at the levels found in Rotorua is associated with cataract. The previously found association between cataract and H2S exposure in the Rotorua population seems likely to be attributable to the limitations of the ecological study design. These results cannot rule out the possibility of an association with cataract at higher levels of H2S exposure.

Biomass stoves and lens opacity and cataract in Nepalese women.

PURPOSE: Cataract is the most prevalent cause of blindness in Nepal. Several epidemiologic studies have associated cataracts with use of biomass cookstoves. These studies, however, have had limitations, including potential control selection bias and limited adjustment for possible confounding. This study, in Pokhara City, in an area of Nepal where biomass cookstoves are widely used without direct venting of the smoke to the outdoors, focuses on preclinical measures of opacity while avoiding selection bias and taking into account comprehensive data on potential confounding factors. METHODS: Using a cross-sectional study design, severity of lenticular damage, judged on the LOCS (Lens Opacities Classification System) III scales, was investigated in women (n = 143), aged 20 to 65 years, without previously diagnosed cataract. Linear and logistic regression analyses were used to examine the relationships with stove type and length of use. Clinically significant cataract, used in the logistic regression models, was defined as a LOCS III score ≥2. RESULTS: Using gas cookstoves as the reference group, logistic regression analysis for nuclear cataract showed evidence of relationships with stove type: for biomass stoves, the odds ratio was 2.58 (95% confidence interval, 1.22 to 5.46); and for kerosene stoves, the odds ratio was 5.18 (95% confidence interval, 0.88 to 30.38). Similar results were found for nuclear color (LOCS III score ≥2), but no association was found with cortical cataracts. Supporting a relationship between biomass stoves and nuclear cataract was a trend with years of exposure to biomass cookstoves (p = 0.01). Linear regression analyses did not show clear evidence of an association between lenticular damage and stove types. Biomass fuel used for heating was not associated with any form of opacity. CONCLUSIONS: This study provides support for associations of biomass and kerosene cookstoves with nuclear opacity and change in nuclear color. The novel associations with kerosene cookstove use deserve further investigation.