Presbyopia:Effectiveness of correction strategies

Presbyopia is a global problem affecting over a billion people worldwide. The prevalence of unmanaged presbyopia is as high as 50% of those over 50 years of age in developing world populations due to a lack of awareness and accessibility to affordable treatment, and is even as high as 34% in developed countries. Definitions of presbyopia are inconsistent and varied, so we propose a redefinition that states “presbyopia occurs when the physiologically normal age-related reduction in the eye's focusing range reaches a point, when optimally corrected for distance vision, that the clarity of vision at near is insufficient to satisfy an individual's requirements”. Presbyopia is inevitable if one lives long enough, but intrinsic and extrinsic risk factors including cigarette smoking, pregnancy history, hyperopic or astigmatic refractive error, ultraviolet radiation, female sex (although accommodation is similar to males), hotter climates and some medical conditions such as diabetes can accelerate the onset of presbyopic symptoms. Whilst clinicians can ameliorate the symptoms of presbyopia with near vision spectacle correction, bifocal and progressive spectacle lenses, monovision, translating or multifocal contact lenses, monovision, extended depth of focus, multifocal (refractive, diffractive and asymmetric designs) or ‘accommodating’ intraocular lenses, corneal inlays, scleral expansion, laser refractive surgery (corneal monovision, corneal shrinkage, corneal multifocal profiles and lenticular softening), pharmacologic agents, and electro-stimulation of the ciliary muscle, none fully overcome presbyopia in all patients. While the restoration of natural accommodation or an equivalent remains elusive, guidance is gives on presbyopic correction evaluation techniques

SELENIUM CONCENTRATIONS IN SERUM, LENS AND AQUEOUS-HUMOR OF PATIENTS WITH SENILE CATARACT

Selenium (Se) is a trace element which incorporates into the selenoenzyme glutathion peroxidase. Cataractogenesis may be caused either by the excess or deficiency of this trace element. More recently, its potential of becoming a possible environmental pollutant has been emphasized. In an attempt to reveal the relationship of this element with cataractogenesis, we detected its level in 48 serum, 36 lens and 9 aqueous humour samples of 48 patients with senile cataract, comparing the results with appropriate controls. Selenium levels (mean +/- SD) of cataractous patients were found to be 0.28 +/- 0.04 mu g/ml (CI: 0.27 to 0.29 mu g/ml) in sera (controls: 0.32 +/- 0.04 mu g/ml; CI: 0.30 to 0.34 mu g/ml, p < 0.0001), 5.43 +/- 3.07 mu g/g dry weight (CI: 4.43 to 6.43 mu g/g dry weight) in lens (controls: 4.43 +/- 2.53 mu g/g dry weight; CI: 2.78 to 6.08 mu g/g dry weight; p = 0.374) and 0.19 +/- 0.06 mu g/ml (CI: 0.15 to 0.23 mu g/ml) in aqueous humour samples (controls: 0.31 +/- 0.12 mu g/ml; CI: 0.24 to 0.38 mu g/ml, p = 0.02). When patient subgroups were analyzed, serum Se levels were found to be 0.28 +/- 0.05 mu g/ml (CI: 0.26 to 0.30 mu g/ml) in the nuclear cataract and 0.28 +/- 0.02 mu g/ml (CI: 0.27 to 0.30 mu g/ml) in the cortical cataract. Lens Se levels, on the other hand, were detected as 5.91 +/- 3.56 mu g/g dry weight (CI: 4.49 to 7.33 mu g/g dry weight) in the nuclear cataract and 4.47 +/- 1.40 mu g/g dry weight (CI: 3.68 to 5.26 mu g/g dry weight) in the cortical cataract. It is anticipated that decreased Se in aqueous humour and sera of patients with senile cataract may reflect defective antioxidative defense systems which may lead to the formation of cataract