WA Eye Care
Myopia series / 02 of 06

Why does the eye keep growing?

Blur, contrast, the choroid and the sclera.

  1. 01Myopia control: slowing how fast the eye grows
  2. 02Why does the eye keep growing?
  3. 03Treatments, part 1: drops and light
  4. 04Treatments, part 2: lenses
  5. 05Myopia control, the Perth way
  6. 06How do we know it’s working?

The eye reads visual signals to decide how much to grow

Part 02 · 01
Cross-section: the retina reads blur and contrast, the choroid relays the signal, and the sclera remodels.
Fig 2.1Signal → relay → growth
  1. 01

    The retina reads the signal

    Blur and contrast patterns in what the child sees.

  2. 02

    The choroid relays it

    A blood-vessel layer that thickens or thins in response.

  3. 03

    The sclera remodels

    The eye’s outer wall stretches, or holds firm.

Signal 1: blur at the edges of vision

Part 02 · 02
Single-vision glasses leave peripheral focus behind the retina; myopia control lenses move it in front.
Fig 2.2Single-vision vs myopia control lens
  1. 01

    Blur behind the retina says “grow”

    Regular glasses can leave the edges focused behind it.

  2. 02

    Blur in front says “slow down”

    Myopia control lenses move that blur in front.

  3. 03

    Central vision stays clear

    Your child still sees sharply through the centre.

Signal 2: high-contrast close work

Part 02 · 03
High-contrast text creates big differences between neighbouring cones; softer outdoor scenes create small differences.
Fig 2.3Contrast between neighbouring cones
  1. 01

    Black text on a white page

    Creates strong contrast between neighbouring light-sensing cells.

  2. 02

    The theory: strong contrast drives growth

    Softer natural scenes outdoors send a weaker signal.

  3. 03

    Two signals, one system

    Blur and contrast probably work together.

The relay: a thicker choroid is an early good sign

Part 02 · 04
When treatment works the choroid is thicker and well perfused; in a growing eye it is thin and the sclera is starved of oxygen.
Fig 2.4Thick vs thin choroid
  1. 01

    The choroid is a layer of blood vessels

    It sits between the retina and the eye’s outer wall.

  2. 02

    It thickens when treatment works

    Often within days to weeks of starting.

  3. 03

    Better blood flow protects the sclera

    A starved, low-oxygen sclera stretches more easily.

Inflammation: an emerging piece of the puzzle

Part 02 · 05
Low oxygen and inflammatory signals may activate enzymes that break down collagen in the sclera.
Fig 2.5Emerging theory
  1. 01

    Linked with some inflammatory conditions

    Allergic eye disease, uveitis, arthritis, type 1 diabetes.

  2. 02

    Inflammatory markers are higher in myopic eyes

    Including enzymes that break down the eye’s wall.

  3. 03

    Still a theory, not yet a treatment

    Researchers are working out cause versus effect.

In summary

Part 02
  1. 01Blur and contrast tell the eye whether to grow.
  2. 02The choroid relays that signal to the eye wall.
  3. 03Good choroid blood flow helps keep the sclera firm.
← Part 01Eye lengthPart 03 →Drops & light
Myopia / Mt Hawthorn

Book a myopia assessment.

Child getting more short-sighted each year? We measure eye length to see how fast their eyes are growing.

Book

General information only, not personal advice. Every child is different. Treatment is decided after a full eye examination.

WA Eye Care · Room 3, 103 Scarborough Beach Road, Mt Hawthorn WA 601608 6288 4218 · info@waeyecare.com.au