National Antivisection Society
Animal-free cataract model developed
Posted: 26 April 2010. Updated: 26 April 2010
Dr. Michael Wormstone’s laboratory at the University of East Anglia was funded for one year. The culmination of this work was a successful in vitro model. This model will allow the testing of intraocular lens which are used in cataract surgery.
Pictured right, a piece of lens cultured in human serum. Cell growth visible in purple.
Cataracts, which affect both sexes equally, are the main cause of impaired vision in the world. They are most commonly found in older people, but occasionally children can be born with them. There are various risk factors for cataracts including a family history of the disease, smoking and overexposure of eyes to sunlight. Cataracts can be treated with surgery which removes the cloudy lens, which is then replaced by a synthetic intraocular lens (IOL) [1].
Unfortunately, many operations result in secondary blindness due to the colonisation of the back of the capsule, by stubborn resident epithelial cells which usually line the lens-holding capsule. This is known as known as Posterior Capsule Opacification (PCO) and occurs in about 25% of patients.
Until a mechanism is discovered which will prevent PCO occurring, the modification of IOL design will continue to be important. Unfortunately, the current method for IOL investigation has used rabbits. However, Dr Wormstone used donated human “eye bags” to carry out such tests. Capsular bags containing an IOL are maintained in a tissue culture dish, pinned down and inverted so that they are cultured with the anterior face down. This provides better physical interaction between IOL and the capsule, which is more reflective of the human in vivo situation.
Dr. Wormstone established the optimal level of human serum in which to maximise cell growth on the lens. This was done using dissected human capsular bags, which had associated epithelial cells. These were cultured until the cells recolonised the capsule and then cut into quarters, each maintained a different media. Cell growth was identified using microscopy and by observing cell division levels using a DNA labelling dye. The team were then able to use these conditions to begin testing IOLs in the fully human ocular bag system, in order to determine how lens shape influences the growth of new cells on the capsule. IOLs were implanted into donated human eye capsules and eye bags without IOLs were used as a control. In order to monitor any cellular growth, fluorescence microscopy was employed.
It was noted that the presence of an IOL slowed cell growth and also reduced the degree of wrinkling of the capsule – those capsules without an IOL showed cells at an earlier point in the research, followed next by those with a round edged IOL and finally the square edged IOLs.
Dr Wormstone concluded that, the LDF funded project had culminated in the development of “a fully human in vitro capsular bag system that relates well to clinical observations and permits the testing of novel intraocular lenses in the future.”
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[1] http://www.cks.nhs.uk/patient_information_leaflet/cataracts_age_related
