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Human eye growth stages uncovered by Australian researchers

20/02/2019By Myles Hume
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The eye’s lens undergoes two distinct growth phases during a person’s life, Australian researchers have confirmed following the most comprehensive study ever conducted into the weight of the human eye.

Dr Ashik Mohammed, under the supervision of Professor Bob Augusteyn, made the discovery after analysing 549 human lenses from people aged from infants to elderly adults, dwarfing previous studies where only 20 weights had been measured in young lenses.

The work formed part of Mohammed’s PhD research at the Brien Holden Vision Institute and University of New South Wales, and could play a future role in developing treatments for cataracts and presbyopia.

Augusteyn – a world authority who has studied lens growth patterns in more than 150 animal species – said the study was the first to measure lens dry weights for the entire lifespan.

Robert Augusteyn
Robert Augusteyn
“Between birth and late teens, the lens changes shape from nearly round to elliptical.”
Professor Bob Augusteyn

“This study, which measured both dry and wet lens weights, demonstrated that pre-natally, the lens grows in a rapid logarithmic fashion, while post-natally, growth becomes linear and the chemistry of the new lens cells changes. Between birth and late teens, the lens changes shape from nearly round to elliptical,” he said.

Although the lens grows in a linear fashion after birth, Augusteyn said the ratio of wet to dry weight changed over time.

“The different rates of dry and wet weight accumulation result in a slow increase in the percentage of dry weight, which equates into a slow increase in refractive index,” he said.

“The continued growth pushes cells into the centre of the lens where they compact through loss of water until the maximum compaction is reached. This produces the nuclear plateau of constant refractive index and contributes to the loss of lens power which occurs with age and presbyopia.”

In another first, the researchers also observed differences in lens weight between men and women from birth, supporting the proposition that changes in lens and body weight maybe linked.

Due to a difference in the prenatal growth rates, male lenses were 4% heavier than female lenses at birth. Thereafter, lens weights increased at the same rate.

This year Augusteyn was made a Member of the Order of Australia for his contributions to vision science and health.

The research was published in the journal Molecular Vision.

 

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