What specific problems are cause by astigmatism?

Question

I have it, and know something is round instead of oval, or vice versa.

But what specifically does it cause- thanks in advance

Answer 1

In astigmatism, light rays entering your eye don't focus on a single point on your retina (the nerve layer on the back of your eye - analogous to film in a camera).  

Astigmatism can arise from variation in curvature of your cornea or your lens.  Many people have some degree of astigmatism, though in very mild cases it often doesn't cause noticeable degradation of vision.  Of those with astigmatism that affects vision, it causes blurring that can usually be corrected with glasses or contact lenses.  

The length of your eye can also affect how well light rays are focused on the retina.  An eye that is sightly longer from front to back will cause myopia (nearsightedness).  

Hope this helps.

Answer 2

Astigmatism is only a version of short or long sight, and it is due to a lack of rotational symmetry in the cornal or lens of the eye, (but is not an irregularity, and doesn't involve the shape of the whole eye ball)

The particular feature of astigmatism is that it is present at all distances of gaze, and cannot be eliminated by holding things closer (as in myopia) , or making a focussing effort (as in longsight)

It causes a relative blur in one meridian compared to another: a person with astigmatism oriented diagonally, could not see both bars of an X clearly at the same time, though they might be able to focus on either.

If the astigmatism is of low degree this may not be noticed, but underly a slight reduction in vision and an increase in eye fatigue.

At higher degrees, letters and high contrast objects may appear to have "shadows" in one particular direction.

disitant street lights may appear as ovals or linear streaks, inclined in any direction.

Extreme astigmatism may even be reported as double vision, the two ends of the stretched image being read as separate objects.

Just about everyone has astigmatism if you measure accurately enough, and having 0.25 - 0.50 DC would actually make someone more "average" than having none, but in many it's not enough to include in an Rx, and many spectacle RX's will include a minor astigmatic element that's not been specifically mentioned.

Since soft contacts dont have rotational stability in the eye (they spin on a blink) there has to be *enough* astigmatism for it to be worth supplying the thicker and more expensive toric lenses.  Small degrees of astigmatism (0.25-0.75) are therefore often "written off" when prescribing soft contacts, though for some people an 0.75 cyl correction offers cosniderable benefit.

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Answer 3

I have astigmatism. The actual shape of the back of the eyeball in someone with this condition is oval - like a rugby ball is how the optician who diagnosed me described it. The normal shape of the eyeball is spherical, rather like a soccer ball. my problem is compounded as I am also long sighted.

Astigmatism causes difficulties in reading as the lines on the page appear closer together than they should be , and the sufferer appears to see more lines. This can lead to a "ghosting" effect, in which the reader appears to see the word theyre reading twicw, the second one appearing above the first and being fainter (imagine the picture on on old tv set for an idea of this problem). It can cause driving problems, as road signs tend to appear blurry and the words appear as described.

DId you know that, according to my optician, around 80% of the population has some degree of astigmatism? That' an awful lot of people who may have the problem without evevn knowing it??