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Mechanisms of cataractogenesis in the presence of magnesium deficiency

Agarwal R, Iezhitsa IN, Agarwal P, Spasov AA

Magnes Res, 2013 Jan-Feb;26(1):2-8.
PMID: 23708888 DOI: 10.1684/mrh.2013.0336

Senile cataract is the most common cause of bilateral blindness and results from the loss of transparency of the lens. Maintenance of the unique tissue architecture of the lens is vital for keeping the lens transparent. Membrane transport mechanisms utilizing several magnesium (Mg)-dependent ATPases, play an important role in maintaining lens homeostasis. Therefore, in Mg-deficiency states, ATPase dysfunctions lead to intracellular depletion of K(+) and accumulation of Na(+) and Ca(2+). High intracellular Ca(2+) causes activation of the enzyme calpain II, which leads to the denaturation of crystallin, the soluble lens protein required for maintaining the transparency of the lens. Mg deficiency also interferes with ATPase functions by causing cellular ATP depletion. Furthermore, Mg deficiency enhances lenticular oxidative stress by increased production of free radicals and depletion of antioxidant defenses. Therefore, Mg supplementation may be of therapeutic value in preventing the onset and progression of cataracts in conditions associated with Mg deficiency.

Matched MeSH terms: Cataract/complications*
Implantation and diabetes: analysis of 525 cases

Lim AS, Ang BC, Heng LK, Hart PM, Ngui MS, Chew P, et al.

Ann Acad Med Singap, 1989 Mar;18(2):174-7.
PMID: 2751233

This is a retrospective study of 525 posterior chamber implants in diabetics performed by A S M Lim and B C Ang of Singapore. The patients were reviewed by visiting ophthalmologists--J E Kennedy (Sydney), M Ngui (East Malaysia) and P M Hart (Belfast). This study did not show any significant difference in the complication of post-operative visual acuity between diabetics and non-diabetics. 95% obtained 6/12 vision or better when pre-existing disease was excluded. It also showed that posterior chamber implants can be inserted in eyes with maculopathy or proliferative retinopathy if laser treatment was effectively done before or after surgery.

Matched MeSH terms: Cataract/complications*
Fulltext The Kuala Pilah cluster cataract study: Accessible eye care reduces cataract blindness

Nur Hanis Y, Raman P, Premala Devi S, Mohd Khalid KH

Med J Malaysia, 2019 08;74(4):296-299.
PMID: 31424036

OBJECTIVE: The Ministry of Health introduced the cluster hospital project in Kuala Pilah district in 2016 to allow sharing of resources between the hospitals in the same vicinity. The aim of this study is to compare the demographic profile, prevalence of cataract blindness and low vision among patients who presented for cataract surgery before and after the programme.

METHODOLOGY: This is a retrospective cohort study of patients who underwent cataract surgery in Kuala Pilah Cluster Hospitals between 2010 and 2017. A total of 2539 records of patients were reviewed. Patients were assigned into two groups: Group 1 (2010-2012)- before the programme (2010-2012) and Group 2 (2015-2017) after the introduction of the programme.

RESULTS: There was a significant increase in number of cataract cases in the district hospital after the cluster initiative. The mean age of patients undergoing cataract surgery was similar in both groups. The common comorbidities were hypertension (Group 1=57.3%; Group 2=70.8%) and diabetes mellitus (Group 1=40.6%; Group 2=51.1%). In 2010-2012, most of the patients were one eye blind (34.4%), whereas in 2015-2017 majority of patients presented with vision better than 6/18 (43.5%). The proportion of patients with cataract blindness reduced from 6% in 2010-2012 to 4.3% in 2015-2017 (p<0.01).

CONCLUSION: There is a significant decrease in percentage of patients with cataract blindness and low vision after the introduction of Kuala Pilah Cluster Hospital Program. We believe that that cluster hospital system is effective in improving accessibility to eye care and therefore increases the cataract detection rate.

Matched MeSH terms: Cataract/complications*
Prevalence of blindness and low vision in Malaysian population: results from the National Eye Survey 1996

Zainal M, Ismail SM, Ropilah AR, Elias H, Arumugam G, Alias D, et al.

Br J Ophthalmol, 2002 Sep;86(9):951-6.
PMID: 12185113

BACKGROUND: A national eye survey was conducted in 1996 to determine the prevalence of blindness and low vision and their major causes among the Malaysian population of all ages.
METHODS: A stratified two stage cluster sampling design was used to randomly select primary and secondary sampling units. Interviews, visual acuity tests, and eye examinations on all individuals in the sampled households were performed. Estimates were weighted by factors adjusting for selection probability, non-response, and sampling coverage.
RESULTS: The overall response rate was 69% (that is, living quarters response rate was 72.8% and household response rate was 95.1%). The age adjusted prevalence of bilateral blindness and low vision was 0.29% (95% CI 0.19 to 0.39%), and 2.44% (95% CI 2.18 to 2.69%) respectively. Females had a higher age adjusted prevalence of low vision compared to males. There was no significant difference in the prevalence of bilateral low vision and blindness among the four ethnic groups, and urban and rural residents. Cataract was the leading cause of blindness (39%) followed by retinal diseases (24%). Uncorrected refractive errors (48%) and cataract (36%) were the major causes of low vision.
CONCLUSION: Malaysia has blindness and visual impairment rates that are comparable with other countries in the South East Asia region. However, cataract and uncorrected refractive errors, though readily treatable, are still the leading causes of blindness, suggesting the need for an evaluation on accessibility and availability of eye care services and barriers to eye care utilisation in the country.

Matched MeSH terms: Cataract/complications
Fulltext Leprotic iritis and blindness

Hobbs HE

Int. J. Lepr. Other Mycobact. Dis., 1972;40(4):366-74.
PMID: 4677492
Matched MeSH terms: Cataract/complications
Fulltext Reduction of oxidative-nitrosative stress underlies anticataract effect of topically applied tocotrienol in streptozotocin-induced diabetic rats

Abdul Nasir NA, Agarwal R, Sheikh Abdul Kadir SH, Vasudevan S, Tripathy M, Iezhitsa I, et al.

PLoS One, 2017;12(3):e0174542.
PMID: 28350848 DOI: 10.1371/journal.pone.0174542

Cataract, a leading cause of blindness, is of special concern in diabetics as it occurs at earlier onset. Polyol accumulation and increased oxidative-nitrosative stress in cataractogenesis are associated with NFκB activation, iNOS expression, ATP depletion, loss of ATPase functions, calpain activation and proteolysis of soluble to insoluble proteins. Tocotrienol was previously shown to reduce lens oxidative stress and inhibit cataractogenesis in galactose-fed rats. In current study, we investigated anticataract effects of topical tocotrienol and possible mechanisms involved in streptozotocin-induced diabetic rats. Diabetes was induced in Sprague Dawley rats by intraperitoneal injection of streptozotocin. Diabetic rats were treated with vehicle (DV) or tocotrienol (DT). A third group consists of normal, non-diabetic rats were treated with vehicle (NV). All treatments were given topically, bilaterally, twice daily for 8 weeks with weekly slit lamp monitoring. Subsequently, rats were euthanized and lenses were subjected to estimation of polyol accumulation, oxidative-nitrosative stress, NFκB activation, iNOS expression, ATP levels, ATPase activities, calpain activity and total protein levels. Cataract progression was delayed from the fifth week onwards in DT with lower mean of cataract stages compared to DV group (p<0.01) despite persistent hyperglycemia. Reduced cataractogenesis in DT group was accompanied with lower aldose reductase activity and sorbitol level compared to DV group (p<0.01). DT group also showed reduced NFκB activation, lower iNOS expression and reduced oxidative-nitrosative stress compared to DV group. Lenticular ATP and ATPase and calpain 2 activities in DT group were restored to normal. Consequently, soluble to insoluble protein ratio in DT group was higher compared to DV (p<0.05). In conclusion, preventive effect of topical tocotrienol on development of cataract in STZ-induced diabetic rats could be attributed to reduced lens aldose reductase activity, polyol levels and oxidative-nitrosative stress. These effects of tocotrienol invlove reduced NFκB activation, lower iNOS expression, restoration of ATP level, ATPase activities, calpain activity and lens protein levels.

Matched MeSH terms: Cataract/complications
Effects of topically applied tocotrienol on cataractogenesis and lens redox status in galactosemic rats

Abdul Nasir NA, Agarwal R, Vasudevan S, Tripathy M, Alyautdin R, Ismail NM

Mol Vis, 2014;20:822-35.
PMID: 24940038

Oxidative and nitrosative stress underlies cataractogenesis, and therefore, various antioxidants have been investigated for anticataract properties. Several vitamin E analogs have also been studied for anticataract effects due to their antioxidant properties; however, the anticataract properties of tocotrienols have not been investigated. In this study, we investigated the effects of topically applied tocotrienol on the onset and progression of cataract and lenticular oxidative and nitrosative stress in galactosemic rats.

Matched MeSH terms: Cataract/complications*