Retrodots in the lens in the Beaver Dam Eye Study cohort

Cigarette smoking, body mass index associated with the risks of age-related cataract in male patients in northeast China

AIM

To determine the association between cigarettes smoking, body mass index (BMI) and the risk of age-related cataract (ARC) in middle-aged and elderly men in Northeast China.

METHODS

A hospital-based case control study was conducted. Cases (n =362) were men who had surgically treated ARC, 45-85 years old; controls frequency-matched (n =362) were men who had been admitted to the same hospital as cases for other diseases not related with eye diseases. Cases and controls were matched with 1:1. The cases and controls were interviewed during their hospital stay, using a structured interviewer-administrated questionnaire that included information on sociodemographic characteristics, socioeconomic, lifestyle habits (tobacco smoking and alcohol consumption, etc.), anthropometric measures, personal medical history, and family history of ARC in first-degree relatives, and simultaneously BMI was calculated. The odds ratios (OR) and 95% confidence intervals (CI) of ARC were estimated using multiple logistic regression models.

RESULTS

After adjusting for age and multiple potential confounders, higher BMI was associated with an increased risk of ARC. Cigarette smoking, years smoking or moderate cigarette smoking (1-29 cigarettes per day) had no relation with the risk of ARC (P>0.05), although patients smoking ≥30 cigarettes per day had an elevated risk of ARC as compared with the non-smokers (OR=1.55, 95% CI; 1.16-2.85, P=0.026). Higher BMI was associated with an increased risk of ARC. Both overweight and obesity was associated with an obviously increased risk for surgically ARC (OR=1.55, 95% CI: 1.02-1.98, P=0.015 and OR=1.71, 95% CI: 1.32-2.39, P=0.013 respectively) compared to normal BMI. Then participants were grouped into quartiles of BMI (Q1 to Q4), compared to controls in the lowest quartile, the OR for cases in the highest quartile of BMI was 1.54 (OR=1.54, 95% CI: 1.08-2.46, P=0.022). The results of univariate analysis showed cigarette smoking was not associated with ARC formation for men with lower or normal BMI (P>0.05). Compared to the non-smokers, for men of overweight or obesity, cigarette smoking was associated with a significantly increased risk for surgically ARC (OR=2.00, 95% CI: 1.49-6.65, P=0.003 and OR=1.66, 95% CI: 1.63-13.21, P=0.002 respectively). Similarly, smokers in the highest quartile of BMI had approximately 1.5 times the risk of ARC as non-smokers in the lowest quartile (OR=1.46, 95% CI: 1.06-5.29, P<0.001). Followed multivariate models revealed that the association had never changed.

CONCLUSION

Current cigarette smoking is positively related to ARC only among those who smoking 30 or more cigarettes per day. For men who are both overweight and obesity, cigarette smoking is associated with a significantly increased risk for ARC.

Lens retrodots and vacuoles and their associations with the prevalence and incidence of age-related cataract

AIM

To assess the prevalence of retrodots and vacuoles and their associations with the prevalence and long-term incidence of age-related cataract in an older Australian cohort.

METHODS

Of 3654 baseline participants of the Blue Mountains Eye Study aged 49+ years (1992-1994), 2335 and 1952 were re-examined after 5 and 10 years, respectively. Lens photographs were graded for cataract, retrodots, and vacuoles. Eye-specific data were used to assess the associations between retrodots or vacuoles at baseline and the prevalence and 10-year incidence of nuclear, cortical, and posterior subcapsular (PSC) cataract and cataract surgery.

RESULTS

At baseline, retrodots were present in 142 persons (4%) and vacuoles in 1333 persons (40%). Prevalence of both lens features increased with increasing age (P for trend <0.0001). After adjusting for age and gender, vacuoles were associated with prevalent PSC cataract at baseline (odds ratio (OR), 1.60, 95% confidence interval (CI), 1.25-2.05). After adjusting for age, gender, smoking, hypertension, diabetes, education, and use of inhaled/oral steroids, baseline retrodots were associated with an increased incidence of cataract surgery (OR 2.90, 95% CI 1.71-4.91), while 3+ vacuoles at baseline were associated with an increased risk of PSC cataract (OR 3.56, 95% CI 2.13-5.95) and cataract surgery (OR 1.84, 95% CI 1.22-2.77).

DISCUSSION

Lens retrodots and vacuoles were found to be positively associated with 10-year incidence of cataract surgery, and vacuoles associated with PSC cataract, a finding suggestive of shared risk factors or pathogenesis between these two lens features and the development of PSC cataract.

Age-related retention of fiber cell nuclei and nuclear fragments in the lens cortices of multiple species

PURPOSE

To determine the differences between species in the retention of lens fiber cell nuclei and nuclear fragments in the aging lens cortex and the relationship of nuclear retention to lens opacity. For this purpose old human, monkey, dog, and rat lenses were compared to those of three strains of mouse. We also investigated possible mechanisms leading to nuclear retention.

METHODS

Fixed specimens of the species referred to above were obtained from immediate on site sacrifice of mice and rats, or from recently fixed lenses of other species, dogs, monkeys, and humans, obtained from collaborators. The retention of undegraded nuclei and nuclear fragments was graded 1-4 from histologic observation. All species lenses were examined microscopically in fixed sections stained with hematoxylin and eosin (H&E) or 4',6-diamidino-2-phenylindole (DAPI). Slit lamp observations were made only on the mice and rats before sacrifice and lens fixation. Values of 0 to 4 (clear lens to cataract) were given to degree of opacity. MRNA content in young versus old C57BL/6 mouse lenses was determined by quantitative PCR (qPCR) for DNase II-like acid DNase (DLAD) and other proteins. DLAD protein was determined by immunofluorescence of fixed eye sections.

RESULTS

In old C57BL/6 and DBA mice and, to a lesser degree, in old CBA mice and old Brown Norway (BN) rats lenses were seen to contain a greatly expanded pool of unresolved whole nuclei or fragments of nuclei in differentiating lens fiber cells. This generally correlated with increased slit lamp opacities in these mice. Most old dog lenses also had an increase in retained cortical nuclei, as did a few old humans. However, a second rat strain, BNF1, in which opacity was quite high had no increase in retained nuclei with age nor did any of the old monkeys, indicating that retained nuclei could not be a cause of opacity in these animals. The nuclei and nuclear fragments were located at all levels in the outer cortex extending inward from the lens equator and were observable by the DAPI. These nuclei and nuclear fragments were seen from 12 months onward in all C57BL/6 and DBA/2 mice and to a lesser degree in the CBA, increasing in number and in space occupancy with increasing age. Preliminary results suggest that retention of nuclei in the C57BL/6 mouse is correlated with an age-related loss of DLAD from old lenses.

CONCLUSIONS

A very marked apparently light refractive condition caused by retained cortical nuclei and nuclear fragments is present in the lens cortices, increasing with age in the three strains of mice examined and in one of two strains of rats (BN). This condition was also seen in some old dogs and a few old humans. It may be caused by an age-related loss of DLAD, which is essential for nuclear DNA degradation in the lens. However, this condition does not develop in old BNF1 rats, or old monkeys and is only seen sporadically in humans. Thus, it can not be a universal cause for age related lens opacity or cataract presence, although it develops concurrently with opacity in mice. This phenomenon should be considered when using the old mouse as a model for human age-related cataract.