We wouldn't be the first to compare the optics of the eye to a camera. The eye is actually a satellite extension of the brain and much more complex. If you understand the interaction of the lens optics, the camera body, the film/receptor, aperture, and other concepts, you will have a better understanding of how eye floaters are seen and interpreted by the eye and brain.

Unlike the static image created by a camera, eye floaters are a dynamic visual phenomenon that are interpreted by the brain's visual cortex and the awareness of these floaters are influenced by the person's personality type or other factors such as vocational activities, and other external factors.

Depending on the location of the floater material in the eye, the shadow can be seen as soft vs. hard edged, distinct vs. vague. The mobility of the floater is influenced by the liquefaction (breakdown of gel to more watery fluid) of the vitreous as well as the amount of eye, head, and body movement. The awareness of the eye floaters also depends greatly on the visual task performed. As we will explain, bright ambient light (e.g. daytime driving) and/or brightly backlit visual material (e.g. computer monitors will tend to accentuate the shadows.

Here is an illustration showing a cross-section of a simple camera and the basic optical components of the eye. In both instances they are observing and focused on this light bulb. The optical component of the camera are several lens elements. The adjustable features include focus and aperture (the iris opening regulating the amount of light entering the eye). The analogous light refracting parts of the eye are the cornea (very front transparent curved element and the crystalline lens labeled here. The cornea is static whereas the crystalline lens has some adjustability to it allow us to focus at different distances. the aperture of the eye is regulated by a muscular structure also call the iris. The color of the iris determines the color of the eye, and the opening of the center of the iris is the pupil. When the environment is very bright the optimal position of the iris is for a small opening (aperture). With a camera, the "f-stop" would be f16 or f32. When the environment is dark, the aperture opens up to allow as much light as possible to enter (camera equivalent of f1.8 or f2.4 depending on how much you are willing to spend on camera lenses!!). The sensor in the camera would be film or the newer digital sensors. The curved, concave, orange structure shown in the eye is the sensory retina. It has multiple layers and is incredible complex, but for our purposes we will just need to understand that each "pixel" sensor (rod or cone cell) senses light, dark, and color information and relays that to the visual cortex of the brain where it is interpreted.

One observation that will be important later is the optical principle of reversal of the image projected onto the the film or retina. In this illustration, you may see that the image of the light bulb is upside-down and reversed when it is focused onto the sensor. This characteristic will help us find the eye floaters at the time of examination and treatment.

Here is a basic cross sectional cartoon illustration of the eye showing the primary optical parts: The Cornea and crystalline lens making up the light-bending (refracting components), the round globe itself (analogous to the camera body), and the neurosensory retina which lines the inside of the globe.

Here is a combination illustration showing the position of an opaque object positioned in the middle of the eye. The dark disk toward the front of the they represents the pupil opening (small opening in this example) The light rays enter the eye through a small opening and cast a fairly well-defined shadow onto the retina. The box to the right shows how it might be seen by someone looking out towards a plain white background.

Here is that same object but now the light is passing through a much larger dilated pupil such as at nighttime or when the doctor dilated the eyes with eye drops. Since the light is entering from a much larger opening, the shadows overlap. The light coming in from the periphery decreased the shadow in the center. The result is a much less prominent and less bothersome or distinctly defined shadow.

A. A small floater located close to the retina with a small pupil opening: Since the object is very close to the sensor, the shape of the object will tend to be very well defined under most lighting conditions. This can be very bothersome to the person even though the object casting the shadow can be very small.

B. A small floater located close to the retina but with a large pupil: Since it is still close to the retina it is fairly well-defined, but the edges are somewhat softer.

C. A mid-sized, mid-positioned floater  with a small pupil aperture light source. The image is fairly well defined as shown here.

D. A mid-positioned floater with a large pupil aperture: The floater is still defined but with much blurrier and softer edges. Better, but still bothersome.

E. Here we have an object closer to the front of the eye (anterior) with a small pupil opening: Even with a small pupil, the object is softer with moderately blurry edges.

F. This is the same anteriorly-positioned object but seen through a much larger pupil. depending on the size and density if the object it may or may not be seen. If it is seen, it will have very soft edges and will be easier to ignore under most circumstances.

These are all just illustrative examples and generalizations to show that the position of the object in the eye, its density, and the pupil size opening are all very important factors which help determine the awareness of moving objects affecting the quality of vision.

Next, we will learn about the vitreous humour under normal circumstances: VITREOUS