Ideal size of an intraocular lens for capsular bag fixation

PURPOSE

To determine the ideal size of an intraocular lens (IOL) for proper capsular bag fixation in different sizes of evacuated capsular bags.

SETTING

Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea, and Storm Eye Institute Medical University of South Carolina, Charleston, South Carolina, USA.

METHODS

Fifteen eyes obtained post-mortem were divided by crystalline lens size into three groups. Intraocular lenses of five different sizes were implanted in each capsular bag. The arc of contact between the haptics and capsular equator and the capsular bag distortion with each IOL were measured and compared using posterior-view analysis.

RESULTS

The arc of contact was directly proportional to the IOL size and inversely related to the lens size. The smallest arc of contact was 2.0 mm with the smallest IOL implanted in the largest lens group. The maximum capsular bag distortion was 2.6 mm in the case of the largest IOL implantation in the smallest lens group.

CONCLUSION

Implanting an IOL smaller than 12.5 mm in a large capsular bag can result in unstable fixation, while implanting an IOL larger than 12.5 mm in a small capsular bag can result in excessive stretching and distortion of the capsular bag and surrounding zonules.

Analysis of zonular-free zone and lens size in relation to axial length of eye with age

PURPOSE

To evaluate the anatomical relationships of the zonular-free zone (ZFZ) of the anterior capsule and crystalline lens diameter in relation to the axial length of the eye with age.

SETTING

Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea, and Storm Eye Institute, Medical University of South Carolina, Charleston, South Carolina, USA.

METHOD

Various ocular structures in 122 eyes obtained post-mortem were measured without prior preparation. The correlation between age, anterior-posterior (A-P) length and globe size, and diameters of the cornea, crystalline lens, and ZFZ were analyzed.

RESULTS

The average A-P globe length, and corneal, lens, and ZFZ diameters were 24.48, 11.67, 9.65, and 6.93 mm, respectively. There was no significant relationship between A-P length and globe size and corneal diameter in different age groups. The ZFZ size varied negligibly among age groups. There was a statistically significant correlation between lens diameter and age (correlation coefficient = 0.2647; P < .01) and lens diameter and A-P globe length (correlation coefficient = 0.3183; P < .001).

CONCLUSIONS

When choosing an intraocular lens, one should consider the patient's age and the A-P globe length. Six eyes (5%) showed unusual anterior insertion of zonular attachment, which reminds us to be prudent with a large paracentral capsulorhexis.

Anterior shift of zonular insertion onto the anterior surface of human crystalline lens with age

OBJECTIVE

This study aimed to investigate the age-related changes in the position of zonular insertion onto the anterior lens capsule.

DESIGN

The study design was an experimental cadaveric eye study.

PARTICIPANTS

Two hundred twenty-three cadaveric eyes (range, 16-100 years old) from eye banks in the United States were studied.

INTERVENTION

The zonular insertion onto the anterior capsule was detected using a modified posterior photographic technique.

MAIN OUTCOME MEASURES

The distances from the anterior zonular insertion (AZI) to the lens equator and to the ciliary sulcus, size of zonular-free zone, lens diameter, ciliary sulcus diameter, and axial length of the globe were measured.

RESULTS

Multiple regression analysis showed that age, lens diameter, and axial length of the globe had significant correlations with AZI (r2 = 0.748), among which age showed the highest relevance with AZI. Multiple regression equation was expressed as AZI = (0.0079 x age) + (0.202 x lens diameter) - (0.041 x axial length of the globe) + 0.0114. The increase in AZI was accompanied by a decrease in the size of zonular-free zone with age (r = -0.206, P < 0.001).

CONCLUSION

Aging correlates with an increase in the distance from the anterior zonular insertion to the lens equator and a decrease in zonular-free zone.

Homogeneous liposome immunoassay for insulin using phospholipase C from Clostridium perfringens

A new homogeneous liposome immunoassay system was developed in which analyte-phospholipase C conjugates are used instead of complement or melittin. This system was applied for the determination of insulin. Liposomes incorporated with calcein as a marker were prepared by the reverse-phase evaporation method. The lysis of liposomes was determined by measuring the fluorescence intensity of calcein released from liposomes and it was increased with increasing concentration of phospholipase C. Insulin was conjugated to phospholipase C by a three-step procedure with hetero-bifunctional crosslinking reagents, succinimidyl 4-(N-maleimidomethyl)cyclohexane-1-carboxylate and 3-(2-pyridyldithio)propionic acid N-hydroxysuccinimide ester. The lytic activity of phospholipase C was not affected by the reaction for conjugation. Both p-nitrophenylphosphatidylcholine hydrolytic activity and liposome lytic activity of insulin-phospholipase C conjugate were inhibited in the presence of insulin antiserum. However, lower concentration of conjugate and shorter incubation time were required when liposomes were used in the inhibition study. The antibody inhibition of conjugate-induced lysis could be reversed by addition of a competing amount of free insulin. The standard calibration curve was obtained in the range between 4 and 130 microIU/ml (r = 0.994). The detection limit (8 microIU/ml) was comparable with those of conventional heterogeneous enzyme immunoassays. This new assay approach offers a simple, sensitive, and inexpensive testing procedure for determining ultratrace amounts of bioactive substances.

[Anatomical evaluation of the anterior capsular zonular free zone in the human crystalline lens (age range, 50 approximately 100 years)]

It is important to determine the anterior capsular zonular free zone (ZFZ) in order to minimize the risk of zonular disinsertion. From this point of view the size of the ZFZ of normal suspended lenses was directly measured in 199 human eyes obtained postmortem. The cornea was completely excised and the iris removed to allow clear visualization of the anterior surface of the lens to the equator. After measuring lens diameter with a caliper, a 4 mm continuous curvilinear capsulorhexis was performed, and lens substrate was completely removed by phacoemulsification. Care was taken to minimize trauma to the zonules during surgery. The anterior insertion of the zonules was identified at high power magnification; the size of the ZFZ was measured with a caliper. The mean age was 75.5 +/- 10.3 (+/-SD) years (age range, 50 approximately 100 years). The mean diameter of the lenses was 9.72 +/- 0.31 mm. The mean diameter of the ZFZ was 6.83 +/- 0.35 mm. Statistical analysis revealed no significant correlation between the size of the ZFZ and age, or between the size of the ZFZ and lens diameter. The present study indicates that the size of the ZFZ was constant regardless of age or lens diameter.

Role of protein kinase C isozymes in activation of human immunodeficiency virus type 1 in chronically infected promonocytic cells: evidence against a role of PKC beta 1

Protein kinase C (PKC) plays an important role in activation of human immunodeficiency virus type 1 (HIV-1). Because of a molecular and biochemical heterogeneity of PKC, we have studied the effects of PKC isozymes in HIV-1 activation in a latently infected promonocytic cell line, U1, using various PKC isozyme agonists. 12-Deoxyphorbol 13-phenylacetate (dPP), an agonist of both Ca(++)-dependent and Ca(++)-independent isozymes, and thymeleatoxin (TT), an agonist of Ca(++)-dependent PKC isozymes, induced HIV-1 production at 10 nM with increase in a concentration dependent manner, whereas 12-deoxyphorbol 13-phenylacetate 20-acetate (dPPA), an PKC beta I isozyme agonist, did not induce viral production at 100 nM. We verified that dPPA induced translocation of PKC beta isozyme with the isozyme-specific monoclonal antibody using flow cytometry. This study demonstrates that activation of PKC isozymes leads to an induction of latent HIV-1 in U1 cells whereas PKC beta I isozyme may not be important.

Liposome immunoassay (LIA) with antigen-coupled liposomes containing alkaline phosphatase

Immunoliposomes were prepared and their immunoassay applications investigated. Liposomes were prepared from cholesterol and phospholipids including maleimidobenzoylphosphatidylethanolamine (MBPE) for conjunction with thiol-containing antigens. Alkaline phosphatase (APase) was entrapped in the liposome and BSA, the antigen, was modified by reaction with 3-(2-pyridyl-dithio)propionyl N-hydroxysuccinimide ester (SPDP) to introduce thiol groups for efficient coupling. BSA-coupled liposomes (immunoliposomes) were incubated with anti-BSA serum, complement, and then with APase substrate. The amount of coupled BSA was affected by the reaction time, the composition of the liposome and the BSA concentration in the reactant. The amount of enzyme released from immunoliposomes as a final result of the immunoreaction increased with increasing concentrations of complement and antibody. The liposome immunoassay offers a relatively rapid and simple testing procedure to quantitatively or qualitatively determine the presence or absence of antibodies, or antigenic materials for diagnostic purposes.

Water resource development and prevention of malaria

The construction of dams across the mouths of major tidal rivers in the development of the Kranji Reservoir, Western Catchments Scheme and the Sungei Seletar Reservoir in Singapore created suitable environmental conditions for the propagation of anopheline brackish-water breeders. The employment of foreign contract workers from malarious areas for the projects further increased the potential risk of malaria transmission. However, constant vigilance and environmental management aimed at the permanent elimination of vector breeding habitats, supplemented with chemical control and anti-parasite measures successfully prevented the reintroduction of malaria in these highly receptive and vulnerable areas.

Epidemiological aspects of an outbreak of dengue fever/dengue haemorrhagic fever in Singapore

A nation-wide outbreak of 260 cases of DF/DHF with 1 death occurred in Singapore from Apr-Sept 1986. The outbreak originated from 3 separate foci of transmission at the western, south-eastern and north-eastern parts of the island and then spread to other dengue receptive urban and suburban areas. The morbidity rate was highest in young male Chinese adults between 15 and 24 years of age. The outbreak was rapidly brought under control through destruction of adult Aedes mosquitoes, surveys and source reduction of larval breeding habitats, health education and to a certain extent law enforcement. The Aedes population was high in the main foci of transmission although the overall house index was only 1.1. Other factors which could have precipitated the outbreak included waning herd immunity of the human population and continuous introduction of dengue virus into the country.