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Astigmatism and axis error

THEastigmatism is an optical defect "oriented": it has a magnitude (in diopter) and a direction (axis). This characteristic allows astigmatism to be easily represented vectorally, the standard of the vector (length of the arrow) being proportional to the magnitude of astigmatism. The correction of astigmatism requires the use of a device which, when apprehended vectorally, generates a vector of astigmatism equal in magnitude, but opposite in direction. The orientation of the corrective device must be carried out with care; This must be aligned according to the "axis" of astigmatism: glass of glasses, Contact lens O-Ring, Crystalline lens Artificial cataract surgery ), Profile of Photoablation (LASIK(, PKR), etc.

(see also page): rotation of a toric implant in a patient with Keratoconus)

For example, an astigmatism of (+ 1 x 0 °) is corrected if we apply a device that generates an astigmatism of (-1 x 0 °).

It sometimes happens that a "axis error" occurs (see example): a toric implant axis error). Rather than be positioned according to the axis of astigmatism (ex: 90 °), the correction device is 'shifted' by a few degrees (ex: 95 °). This can be caused by inadvertent rotation of a toric implant after installation, movements of cyclotorsion during surgery on the cornea laser photoablation, etc.

A legitimate question arises: what is the result of this shift of axis on the refractive correction result?

Several approaches can be used to calculate the effect of an error in axis for the correction of astigmatism: analytical approach (trigonometric calculations: astigmatism is expressed as a function A x cos (2T), or approach vector (astigmatism is treated as a vector of which the 'norm' is proportional to the magnitude of astigmatism, and orientation in line with the axis expressed in the form of astigmatism - ex) (: 90 °). Can also be used to representation by complex numbers.

The vector method is particularly suited to a 'Visual' understanding of the consequences of an error in axis. Here is the ' graphical representation ' about an example where to correct astigmatism is expressed by the formula + 1 x 90 °.

All astigmatism formulated as an optical prescription ophthalmic can be converted into formulation in positive cylinder (example:-1 x 0 ° plan is equivalent to + 1 x 90 ° with a sphere of + 1 D)

The method described below applies to any situation: if the initial astigmatism is different from + 1 x 90 °, the difference with 90 ° should be added to the final result; And multiply the magnitude of the cylinder obtained in this calculation by the value of the original cylinder. In this representation, a classical angular representation is used, "on 360 °". This representation leads in certain calculation steps to consider doubled angle values. NB: The use of a "Double plot" graph for astigmatism Allows you to draw vectors of the same sign, whose angles are automatically doubled.

The Trigonometric representation of astigmatism Also allows you to see the effect of a correction axis alignment error.

 

With the vector graphics method on 360 °, one represents astigmatism to be corrected by a vector (one arrow) of length + 1 and axis 90 °, oriented in a graduated mark in degree (remember that this method requires converting the initial astigmatism to Correct in positive cylinder formula). The arrows pointing upward have by convention a positive standard (length), the arrows pointing downwards a negative norm.

We can represent the astigmatism (+ 1 x 90 °) like this:

 

vector astigmatism

Vector representation of astigmatism + 1 x90 °

The "opposite" astigmatism, which adding compensates exactly + 1 x 90 ° is:-1 x 90 °. He may be represented by an arrow "down", according to the 90 ° axis.

vectors astigmatism opposed

Opposite astigmatisms: + 1 x90 ° and – 1x 90 ° represented in vector form.

The 'sum' of these vectors of astigmatism is a vector, and a situation where the astigmatism + 1 x 90 ° is perfectly corrected by the addition of a device that induces - 1 x 90 °.

astigmatism compensation neutralization vectors

Total Correction of an astigmatism of + 1d to 90 ° by an astigmatism inducing device (-1 x90 °) in vector representation.

Imagine that a 30 ° axis error occurs in anti clockwise: the corrective device is more placed at 90 ° but (90 °-30 °). Compensatory astigmatism is a vector oriented at 120 °:-1 x (90 ° + 30 °) or - 1 x 120 °. The situation can be represented as follows:

astigmatism axis error 30 ° vector

The axis error of 30 ° induces a "rotation" of the arrow of the correcting astigmatism (vector) of 30 °.

Due to the modulation of the refractive astigmatism on 180 ° (non 360), it must be 'double' the angle corresponding to the axis error (30 °) to continue our graphic resolution of the problem: this angle becomes so 2 x 30 ° = 60 °. We then do an additional 30 ° rotation of the arrow of our vector corresponding to astigmatism induced by the correction device.

astigmatism vector calculation

The angle corresponding to the axis error is doubled.

We can then achieve the vector sum and an arrow which length corresponds to that of residual astigmatism: in this example, this arrow also has a length equal to 1 (the triangle formed by the arrows is equilateral, every angle being equal to 60 °!). When the error of axis is 30 °, residual astigmatism has the same magnitude as the initial astigmatism! On the other hand, its axis is changed (we say colloquially that the axis of astigmatism has "turned"!)

vector astigmatism residual error of axis

The magnitude of residual astigmatism induced by an axis error is obtained by the addition of the arrows. However, the axis must be multiplied by 2 to obtain the final formula.

The geometry of the figure suggests that this axis is (with the horizontal axis) 30 ° and 60 ° with the direction of astigmatism to be corrected (90 °). Again because of the double modulation of astigmatism on 360 °, divide the angle with the axis of initial astigmatism (here located according to 90 °) 2;  60 ° / 2 = 30 °.

astigmatism vectors axis result error

An axis error of 30 ° does not reduce astigmatism to "importance"; But changes the axis by 30 °

An error of axis of 30 ° (-1 x 120 ° instead of-1 x 90 °) induces a residual of 1 diopter astigmatism oriented to 60 °: + 1 x 60 °. The magnitude of astigmatism has not changed, but its axis has changed!

The value of the rotation suffered by the axis of astigmatism in case of error correcting device axis with respect to the 90 ° axis is always equal to (90 ° e) / 2 where E is the error in absolute terms (in degree). In the example above: (90 ° - 30 °) / 2 = 30 °. Well, the axis was diverted 30 ° (angular difference between 90 ° and 60 °).

Another "graphically" remarkable example is an error of 45 °. Instead of (-1 x 90 °) we 'deals' by mistake (-1 x 135 °). As we need to double the value of the angle before sommer arrows, and as 2 × 45 ° = 90 °, we get easily by looking at the geometry of the figure that the magnitude of residual astigmatism is equal to the square root of 2 (or 1.4 D about).

astigmatism axis error 45 ° vectors vector calculation

An axis error of 45 ° induces an increase in astigmatism in magnitude (x140 °)! The axis is deflected by 22.5 °.

The axis of residual astigmatism is (90 ° - 45 °) / 2 = 22.5 °. The final formula is of (+ 1.4 x 67.5).

 

Conclusion

The vector method is particularly well adapted to apprehend the consequences of an axis error for the correction of astigmatism in a "visual" way. The consequences of this type of error consist of an astigmatism of different axis, and of residual magnitude depending on the axis error. This magnitude increases if the axis error is greater than 30 °. This method is useful if you do not have a computer calculator or a suitable software. It is important to remember that the formula of refraction to be corrected should be converted into a positive cylinder; The correcting device is then a vector of the same axis but of opposite magnitude. The use of a "double plot" graph allows you to directly plot the vectors to be summed (without doubling the axes, since they are already doubled in the circular coordinate system, a complete rotation of which corresponds to 180 ° and not 360 °).

This method is useful for the understanding of the observed residual astigmatismes after photoablation (LASIK, PKR), poses a toric implant (cataract surgery), or ask a toric contact lens.

In clinical practice, axis errors do not usually exceed a few degrees. The residual astigmatism is therefore low in magnitude, and its often oblique orientation vis-à-vis the initial axis; A vector graphic representation of the consequences of a few degree error explains this.

astigmatism vectors low error d axis

A small axis error represented in vectorial form induces a moderate residual astigmatism, whose axis is located in an oblique direction (about 45 °) vis-à-vis the initial direction.

 

83 responses to "Astigmatism and axis error"

  1. Dr. Damien Gatinel says:

    Simply because these axes correspond to the same astigmatism (aberration "oscillating twice" on the 360 degrees of a unit circle)

  2. TURK I says:

    Hello doctor,

    I have an astigmatism (OD-2,75, (5) and OG-2,25, 170 °) with a presbyopia which is changing rapidly for 1 year (I am 47 years old and in 6 months I needed to increase the Addition of 1.75 to 2, or even of the + 2.25 + discomfort with progressive lenses). Initially, I would have a slight farsightedness of 0.25 or 0.5, never previously diagnosed, and detected recently with the technique of interference (although this is uncomfortable one + 0.5 extra VL Sphere).
    On the other hand I noticed everything by chance (following several tests in opticians and ophthalmologists), that with an additional correction of + 0.25 or + 0.5 in hyperopia (sphere, to normalize the addition VP% age), I need a correction Slightly stronger astigmatism of 0.25 (i switch to OD-3 and OG-2.5) and especially the axis changes for the OD! (I go from 5 ° to 10 °).
    How to theoretically explain the increase in astigmatism (after correction a hyperopia) and the marked change of the axis? The fact that the axis changes by 5 ° is very vicious because generally the ophthalmologists do not readjust in review this critical parameter when evaluating the addition of hyperopia needed! Without this readjustment of 5 ° I see blurry with the new correction (I am very sensitive to the axis at 2 degrees near). Also, I do not know if the progressive lenses also take into account this perceived change of the axis in VP (especially with a addition of + 2d!). Would this explain the discomfort I have with progressive (yet individualized) lenses?
    What do you think? Thank you.

  3. Dr. Damien Gatinel says:

    It is difficult to give you definitive answers but some components could account for the effects of the change of your correction. You present a direct myopic astigmatism, that can be corrected in glasses by the application of a right cylindrical glass. Refraction fluctuations are common in astigmatic that "' frequently to"optimize"their vision, that is to say the quality of the retinal image. Astigmatism is a "mathematisation" of a complex optical problem and not limited to astigmatism (aberrations of high degree, spherical defocus) Associate, etc.; Remember that in practice, the image formed on the retina by the optics of the eye is blurred. In accommodating slightly, we can modulate this image, and the quality will depend on its contents in detail and color. Based on these details and colors, the 'optimal' correction may vary. The diameter of the pupil is also a setting likely to vary your correction. Finally, if it is certain that the axis of astigmatism correction is important and must be respected, it can also vary with respect to the mount to test under the effect of the position of the patient's head (and), and of course the factors. Thus, there is no '' a correction '' optimal but a correction adapted to what you see, depending on the distance of the Visual stimulus, its content (spatial frequencies), its chromatic spectrum etc. etc. If one modulates the sphere (correction of hyperopia in your case), the increase of myopic astigmatism is not surprising, because this astigmatism in his formulation eye, 'contains' the sphere (spherical equivalent change). Finally, the addition of a progressive lens on a glass addition spherocylindrique is quite able to cause a slight variation of astigmatism, without speaking of distortion effects, which can make these lenses uncomfortable in certain lines of glass.

  4. TURK I says:

    Thank you for your response doctor. Actually, I have found that since my recent prescriptions for strong additions (> + 1.75 / + 2.00 D), aberrations and distortions of progressive lenses are more important, aberrations that I can't bear with my astigmatism (blurry vision on the sides, strong very annoying distortions in intermediate vision). It also seems to me due to back the centering of the vision closely (possible with some types of glass individualized to have, a priori, a sufficient intermediate convex addition on computer at 40 cm), greatly reduces the field of view to 5 or 6 cm on the screen of the computer and adds a lot of distortions that I can't bear.
    Automatic refractometers, very widely used in examination (to first approach the corrections), seem to have difficulty in diagnosing "hidden" hypermétropies behind an astigmatism like mine (the proof is at 47 years, when Of my presbyopia, that I am diagnosed with a latent hyperopia of + 0.5 D, while I have been wearing glasses since the age of 5 years. I am told that the farsighted Presbyopic are never happy but ink must have the right lenses and good assembly (good centring of the VP in progressive lenses minimizing aberrations/distortions, accuracy of the primordial axis in my xxx_xxx _ 51634730 Fort astigmatism).
    I wonder if it should not, in my case of longsighted/astigmatism/hyperopic (in short the total:-)), have glasses dedicated to reading on computer screen (intermediate) and newspaper/tablets (close).
    A poorly corrected presbyopia can be very annoying in some case and induce ophthalmic headaches and quick eye fatigue (my case). It deserves to be explained especially in the presence of strong astigmatism and/or hyperopia, or sometimes lack of convergence.
    I want to thank you for your very informative and educational site.

  5. Dr. Damien Gatinel says:

    There is not really of dogma or absolute rules of lens correction for the presbyopic hypermetropia; the 'unmasking of a farsightedness to quarantine, to the occaseion of the installation of presbyopia (reduction of accommodative power) is very common.

  6. BALAKRISHNAN says:

    Hello
    I understand that an axis has 0 or 180 is identical?
    What explains the difference between a prescription and an optician's bill?
    Thank you for your validation

  7. Dr. Damien Gatinel says:

    Exactly. 0-180 degrees are equivalent to the prescription of ocular astigmatism correction.

  8. digoit says:

    Hello
    I have a question about my prescription: In 2014 when I was pregnant with my second child I had the correction; OD + 1.00 (-2.75) 25 ° OG + 0.75 (-0.50) 10 °.
    Two years (39 years) I get; OD + 1.00 (-2.50) 25 ° OG + 0.75 (-0.50) 5 °
    I don't quite understand the difference. Would the right eye be less corrected than it was two years ago? I would also like to understand the meaning of the axis on the left eye, I went from 10 ° to 5 °.
    Thank you for enlightening me on that.
    Kind regards.

  9. Dr. Damien Gatinel says:

    Changes you have noticed are low, and may correspond to a "fluctuation" of measure. In other words, these corrections are very close. A difference of 5 ° can for example be at a slightly different angle of the eye (with respect to equipment for test corrections) at the time of the measurement.

  10. WAA says:

    Hello
    I'd like an opinion on this prescription:
    At my daughter during the discovery of astigmatism it was prescribed as following glasses:
    Od; -1 (+ 2.5) 90 °
    og; Plan (+ 2.5) 90 °

    Two years later he was prescribed glasses as following:
    OD: + 4.50 (-4.00) 180 °
    OG: + 6.50 (-4.50) 180 °
    Thanks in advance.
    Well cordially

  11. Dr. Damien Gatinel says:

    Your daughter has a direct hypermetropique astigmatism. This is usually related to an excessive toricite of the cornea (the toricite is a geometric feature which reflects the fact that if you measure the cornea of your daughter in two cups, a vertical and the other horizontal, one would observe an optically significant difference). Overall; the curvature of the cornea that is explored in a horizontal direction is insufficient to focus light the retinal plane and provide a clear enough vision. It is necessary to correct the astigmatism by a correction in glasses. Progression of astigmatism seems important, but it is may be related to an "accommodative decompensation", that is, less compensation by accommodation of this astigmatism. The realization of a topography of the cornea (if your daughter is wise enough to write this painless test but sometimes a little impressive for young children) will allow to measure the curvature of the cornea and confirm these points.

  12. SARLANGE says:

    Hello
    I ordered lenses from an optician with these fixes:
    OD + 3 (-0.75) at 70 °
    OG + 3.75 (-1.25) at 55 °.
    No problem for the OD when ordering but for the OG, they tell me that the correction at 55 ° does not excite and they put a correction to 70 ° as a test. But I would not have the correct correction. Will there be a big difference? Why not put a 60 ° correction

  13. Dr. Damien Gatinel says:

    It is certainly a matter of stock or high-end, but -rings lenses sometimes tend to align themselves with a slightly different focus from that of their prescription, and so it's interesting that you try this lens to check the quality of the correction that it provides.

  14. bougardier says:

    Hello

    I'd like an opinion on this prescription:

    Right:-0.50 (+ 0.25 0) add + 1.75
    Left: (+ 0.25 0) Add + 1.75

    Why not give on the left as - 0.50 on the right

    and 0 is identical (0.25 + 0) = (+ 0.25 180) = (-0.25 90)

    Thank you

  15. Dr. Damien Gatinel says:

    The left eye has a very moderate reverse hypermetropique astigmatism. The same astigmatism is present right, but with a very slight myopia (-0.50D). It is unlikely that these corrections are necessary for distance vision. Presbyopia you leads to having to wear an addition (progressive lens, + 1.75 D)

  16. Mahdi says:

    Hello
    I would love to have your opinion on this prescription:
    OD:-0.5 Axis 75 °
    OG:-0.25 Axis 100 °

    Thank you

  17. Dr. Damien Gatinel says:

    This requirement corresponds to the correction of a very moderate myopia, the direction of which is called "against the rule" (or even "reverse astigmatism").

  18. Véronique says:

    My old prescription lenses was od-3.75 (-1.25) 180 and OG-3.00 (-1.75) 10. My new prescription is od-4.00 (-1.25) 5 and OG-3.25 (-2.00) 5. Is it possible to take lenses with a 10 axis? Thank you!

  19. Dr. Damien Gatinel says:

    If astigmatism has been measured at a 5 ° axis, and you are trying lenses for which the axis is 10 °, there should actually be no problem and correction be effective.
    I hope that this information will be useful to you.

  20. Fournier says:

    Hello
    In 2013 my correction indicated OD-1.50 (+ 0.25) 120
    OG + 0.25 (+ 0.25) 55 addition + 1.75
    In 2017 it indicates OD-1.00 (+ 0.25) 90 and OG + 0.50 (+ 0.25) 90 addition + 2
    I'm also amblyopic left eye
    I am amazed at the difference in the numbers of the axis between these two ordinances is this the lower my vision?
    Thank you for explaining. Christine

  21. Quenta says:

    I read a comment indicating that an angle of 0 or 180 is the same, but in negative cylinder notation (ophthalmologist) or positive cylinder (optician?)

    For my myopia + astigmatie, my prescription says on the OD
    -2.25 (90 °-0.75)
    My "warranty" optician says
    -0300 (+ 075) 180

    or by applying the transposition formula (ex:) Http://www.thomassinclairlabs.com/vu.. URsposition.html) I always find
    -0300 (+ 075) 0

    Hence my interrogation ...

    Thank you!

  22. Dr. Damien Gatinel says:

    The equality 0 °-180 ° is independent of the cylinder sign. Thus, the correction expressed in positive or negative in your message corresponds exactly to the same realization of corrective glass.

  23. Dr. Damien Gatinel says:

    The difference in axis is actually pronounced, but astigmatism must be interpreted according to the value of the cylinder, which is very low in you, and this is not disturbing or the fact of a progression to be dreaded. This is certainly more of a measurement fluctuation.

  24. Ahmed says:

    Hello I know the consequences of a strong astigmatism and low myopia-1.5 (-5.00) 180 ° and also when to wear my glasses. Thank you cordially

  25. Pat says:

    During my recent check I have a new prescription for the right eye either
    OD-5.25 (-1.50) 100
    While the current correction is
    OD-4.50 (-2.25) 90
    Has astigmatism decreased? Is that possible? I have not found any explanations on your site yet very well documented.
    Thank you

  26. Dr. Damien Gatinel says:

    Astigmatism, especially in its reverse direction, is generally likely to induce different prescriptions over time. There is often a more marked discrepancy for "inverse" astigmatism (the eye exhibits an excess of power compared to the horizontal meridians) between the corneal part of astigmatism and its "internal" part. In other words, a fluctuation in measurement is possible. It would be better to carry out a measure of cornénnne topography (and a possible aberrométrique examination) to study the part corneal vs. internal (subjective refraction vs.) of your astigmatism. It is interesting to note that your spherical counterpart is unchanged (the spherical equivalent represents a bit the "average" of your refractive error). What was removed from astigmatism was added to the correction of the sphere (passage from-4.50 D to-5.25 D). It is possible that there is no big change but that the measurement technique of your ophthalmologist has led to a sensible but not major difference in your correction.

  27. Nizar says:

    Hello
    During my recent check I have a new prescription for the left eye either:
    OG:-1.00-1.25 175 and I have not find my axis on the site I find only 170 and 180 which one to choose??
    Thanks in advance

  28. Dr. Damien Gatinel says:

    The axis 175 ° exists well, but if for some reason you have to make a choice between the two, you can choose 180 °, this should not significantly change things.

  29. Rhizou says:

    Hello
    I would like to understand because my ophthalmologist put me
    Right eye: 10 °-0.25 and left eye: 180 °-0.25
    I noticed that there was a difference in relation to the axis.
    Can you please explain to me?
    I said maybe he missed a number too lol

  30. Dr. Damien Gatinel says:

    The axis of the left eye is not necessarily exactly the same (or symmetrical) of the right eye. There is nothing shocking in your (weak) correction.

  31. Magali says:

    Hello
    I'm astigmatism with a slight presbyopia. I have a prescription for monthly lenses (OD: + 0.25 (-2.25) to 140 ° and OG: + 0.50 (-2.25) to 40 °) but I would like to switch to the daily lenses since I only wear it very rarely. On the other hand, I do not find at all the same axes between the two kinds of lenses. Is it better to choose an axis lower than or greater than that prescribed? Does it have a big impact? Thank you for your help

  32. Dr. Damien Gatinel says:

    The nearest axis to 5 or 10 degree should be sufficient, approaching 0 ° for axes below 90 ° and 180 ° for axes greater than 90 °.

  33. Barchilon dela Cruz says:

    BJR l Order of my ophthalmologist indicated for the right eye (0 ° + 0.75) + 0.50, addition + 3.00
    The optician's workshop card indicates for the right eye + 00.50 (+ O. 75) 180 ° ADD + 3.00
    The glasses are coherent with the ordinance.
    I have trouble getting used to it especially standing by walking sensation of loss of balance but C is
    The first day.
    Thank you for your help

  34. Dr. Damien Gatinel says:

    The glasses made correspond well to the prescription, and the imbalances felt during the adjustment should be diminished over time.

  35. Student says:

    Hello, medical student, would it be possible to explain to me how to deduct a direct or indirect astigmatie from an order?

    On this order for example:

    OD-2 (-1 to 90 °) 4/10e, addition + 3; Paing 4
    OG-2.5 3/10e, addition + 3; Paing 4

    Thanks in advance!

  36. Dr. Damien Gatinel says:

    For this you have to look at the sign of the cylinder and the axis: in your example, the sign of astigmatism is negative (-1).
    When this so-called "negative cylinder" formulation is used, astigmatism is said to be direct if the axis is close to 0 ° (or 180 °). It is said indirect if, as in your example, the axis is close to 90 °/

    When astigmatism is expressed in positive cylinder (ex + 2 x 0 °), it is the reverse: direct astigmatism If the axis is close to 90P, it is indirect (or inverse) if the axis is close to 0 °

  37. Christine says:

    Hello doctor
    I am astigmatism, and I would like to have your opinion on these prescriptions
    Six months ago This corrected me was this:
    Od: Plan (-2.50 to 55 °)
    OG: Plan (-2.00 to 110 °)
    Now at the moment it is:
    Od:-1.25 (-3.25 to 30 °)
    Og:-1.25 (-2.75 to 145 °)
    What does this change mean, please?
    Thank you

  38. Dr. Damien Gatinel says:

    This change is quite significant, and I advise you to carry out an examination of corneal topography to élminer the possibility of an alteration of the geometry of your cornea (eg: keratoconus beginner, pathology caused by the eye rubbing, Particularly more common in allergic patients, etc.). Your astigmatism has increased, it has changed direction and myopia has associated with it. All this makes suspect a concern at the level of the corneas, and the topography corneal is an examination that will allow to know more.

  39. DALTO says:

    Hello, doctor.

    My 7-year-old son had last year a correction of
    OD + 3.25 (-0.75) 15 °
    OG + 4.25 (-1.00) 150 °

    This year it goes to:
    OD + 2.25 (+ 0.75) 105 °
    OG + 3.25 (+ 0.75) 65 °

    The doctor indicated a decrease in his astigmatie and that his hyperopia was now stabilized and that she would hardly move. I had understood, however, that by growing this one could greatly diminish (eye that becomes bigger...)

  40. Dr. Damien Gatinel says:

    The hyperopia has regressed slightly, and astigmatism has remained unchanged. It is difficult to predict the evolution of a hyperopia in the feed, but when it has this degree at the age of 7 years, it is impossible that it regresses (ocular growth is overall complete).

  41. Dr. Damien Gatinel says:

    At 7 years of age, it is unfortunately no longer possible for the eye to grow sufficiently to correct such a degree of hyperopia.

  42. Boupillere Agatha says:

    Hello
    I have a prescription for:
    OD – 4.50
    OG (15,-0.25)-3.75

    I wanted to be sure to read the ordinance well and make sure that the orientation of 15 is possible.

  43. Dr. Damien Gatinel says:

    The axis of a correction of astigmatism (cylinder) can take any value between 0 ° and 180 ° (usually in steps of 5 °).

  44. Gaston says:

    Good evening, doctor.
    My daughter is 12 years old, and for 9 years had a correction of;
    OD – 5, – 2 shaft 180 °
    OG – 1 axis 10 °
    Following an important anisometropie, she had an OD strabismus that was definitely guerri by thinking of the left eye.

    Before 2 weeks I have a prescription for:

    OD-5 -2 Shaft 170 °
    OG – 1 Axis 5 °

    I want to know why the axis has changed, or simply is a solution of the optician.
    Is this solution just about the axis?

  45. Dr. Damien Gatinel says:

    Indeed, the axes are slightly modified, this can be linked to the measuring conditions (position of the head). It is rare for the axis of astigmatism to change spontaneously. Here the variation is quite low and should not affect the correction a priori too much.

  46. John Vadlamudi says:

    Hello
    I went to do a check at my optician last month and the results were as follows:
    OD SPH:-1.75 CYL:-1.00 AXIS: 180
    OG SPH:-2.00 CYL:-0.75 AXIS: 5

    I had done another review last year and my results were not quite the same...
    OD SPH:-1.75 CYL:-0.75 AXIS: 175
    OG SPH:-2.00 CYL:-0.75 AXIS: 175

    But I wonder, is it possible that my axis to the OG has gone from 175 to 5??

    Thanks in advance for your reply

  47. Dr. Damien Gatinel says:

    The passage from 175 ° to 5 ° corresponds in fact to a simple deviation of 10 ° from the axis of your astigmatism (0 ° and 180 ° are equivalent). There does not seem to be a big change in your correction in your case.

  48. Maxime says:

    Hello

    I recently went to do a check, making the difference between my prescription from two years ago and the news that I got on this site:-)
    Order of 2016:
    OD + 2.25 (-0.25) 5 °
    OG + 3.50 (-0.25) 140 °

    Order of this year:
    OD + 2.75 (-0.25) 10 °
    OG + 3.75 (-0.50) 165 °

    I found my consultation of 2014:
    OG + 3.00 (-0.50) 150 °

    Why "So much change" on the axis of astigmatism with one eye in three steps?
    A bad calibration of the machine for the measurement of the axle?
    Is it amazing to have such an evolution in the axis: decrease axis of 10 ° and increase of 25 °?
    A difference of 25 ° is considered important (close to your demonstration for the case of 30 °)?
    Thanks in advance for your return:-)

  49. Dr. Damien Gatinel says:

    There are several factors that may alter the prescription of a moderate astigmatism correction. There is not, in some eyes, an "absolute correction", but a state that can make this type of corrections compatible with a vision deemed satisfactory by the patient. For example, the eyes whose cornea is a bit irregular (this is often observed in patients who rub their eyes, or who sleep on one side, that of the eye concerned), have optical anomalies that can not well be corrected by a glass Glasses. But these aberrations (so-called high-level) can influence the perception of filing, and thus render "imperfect" (or ambiguous) the correction of an astigmatism in luenttes.

  50. Mamine says:

    Hello, I have a prescription: Eye D:-0.50/Eye G:-0.50 (170 degree). My question is why the axis is right on the left eye and why also it is so high (170) that it means this correction please. Knowing that I consulted for a view problem near (my work is on PC) and the diagnosis was (lack of convergence). I really hesitate to put this correction, which you advise me. Thank you so much

  51. Dr. Damien Gatinel says:

    The value of the axis (170 °) is simply that of a "direction" and its value has nothing to do with the strength of astigmatism (its magnitude is at you of-0.50 diopter, which is rather low). Only your left eye is astigmatism, and it is a priori preferable that you wear a correction of this myopia.

  52. PIGEYRE says:

    Hello my last prescription mentions for each of the two eyes the same needs be: + 1.75 (-0.50) 95 º ADD 2.00 What is it in terms of deficit
    Faced with the discomfort of wearing glasses (large outdoor work) for more than 10 years what do you think of laser surgery.
    Thank you

  53. Dr. Damien Gatinel says:

    You have hyperopia, a little astigmatism, and a presbyopia. This type of optical defect is quite accessible to a laser correction in refractive surgery, provided that the operating record of detects no contraindication for it.

  54. Annie says:

    Hello doctor, I have some difficulty in interpreting the evolution of my view with regard to my last 4 prescriptions which I copy below verbatim:

    2009:
    OD (95 ° + 0.25) Map
    OG (90 ° + 0.25) Map

    2011:
    OD + 0.50
    OG + 0.75

    2014:
    OD (+ 0.50 to 100 °)
    OG (+ 0.50 to 60 °)

    2017:
    OD + 0.50 (+ 0.50 to 120 °)
    OG + 0.75

    The passage from 100 ° to 120 ° seems to me consequent...
    I have been astigmatism since childhood but I have not been wearing glasses since 2008 never really felt the need. However, working a lot (since adolescence) on screen, I had my eyesight checked regularly for prudence. Having now 43 years, I think more prudent to wear it again. Do you think I should do a consultation before? The optician tells me that the order of January 2017 will suffice.
    Thank you.

  55. Dr. Damien Gatinel says:

    You present a low latent hyperémtropie, which becomes more manifest as the accommodatifing power of your eye decreases (installation of the presbyopia). The wearing of a correction similar to that of 2017 is quite likely to give you some visual comfort in vision from afar and close. When this one is no longer guaranteed by the port of this correction, you can then revisit and can be benefit of a correction simulatnée for the distance and the near (progressive glasses).

  56. Gerald says:

    Hello
    Very interesting, but I have 2 questions:
    1) The 45 ° axis on the eye is what the patient sees (like à14h40 needles) or what the doctor sees when looking at the patient's eye???

    2) I see much sharper by frowninging the eyebrows, near or far, why?
    Thank you

  57. Dr. Damien Gatinel says:

    The axis of astigmatism is defined according to the ophthalmologist's viewpoint by looking at the patient's eye. Frowning usually results in a slight reduction in the pupil intake (eyelid-induced reduction that creases and overlaps the cornea). This reduces the retinal blur (the pupil Smaller The is, the less the effects of an optical defect are pronounced and conversely).

  58. Karam says:

    Hello doctor,
    I had two consultation the one in 2016 indicates for the right eye: (Sphere + 0.25) (Cylinder-0.50) (Axe100 °). And in 2018 I had noticed a difference following the axis for the same eye: (Sphere + 0.25) (Cylinder-0.50) (Axis 85 °). Could you explain that difference?
    Thanks in advance.

  59. Dr. Damien Gatinel says:

    This difference reflects a slight rotation of the axis of astigmatism, which has no particularly disturbing character. This modification may be the accumulation of physiological factors, or variations in the measure, etc.

  60. Xavier says:

    Hello
    1.5 years ago I was diagnosed with a presbyopia of my hyperopia and astigmatism. I am now 44 years old.
    I then had the following contact lens prescription, and it was satisfying:
    Right: proclear multifocal O + 4.25 (-2.25) 160 ° ADD + 1.00
    Left: Proclear multifocal o N + 5.00 (-2.25) 20 ° ADD + 1.50

    After 6 months I wanted to renew the prescription, but I threw several pairs because my view was no longer correct, my optician believed in a manufacturing defect, we had a new lot but same problem (loss of sharpness, difficult reading,...)

    So I went to Reconsult and got the following correction:
    Right: proclear multifocal O + 4.5 (-2.75) 160 ° ADD + 1.00
    Left: Proclear multifocal o N + 5.25 (-2.75) 20 ° ADD + 1.50

    Always the same problem, loss of sharpness (sometimes the lens stabilizes but it lasts a little long) and especially a lot of discomfort on the vision closely.

    Last Test of a few weeks ago:
    Right: biofinishy TORIC XR + 4.5 (-2.75) 160 °
    Left: Proclear multifocal o N + 5.50 (-2.25) 20 ° ADD + 1.50

    With this vision beyond 80 cm is super sharp, thanks to my right eye, by cons reading impossible...

    So I have 2 small questions
    1) What do you think
    2) More specifically what do you think for someone who wants above all a comfort on reading to put the Strong + eye (right) on the vision from afar and not close?

    I hope to find a solution because for a small year I have been condemned to glasses.

    Thanks in advance for your lighting

  61. Dr. Damien Gatinel says:

    It is difficult to give you an informed opinion because many factors affect the vision of a lens carrier. Your correction is particularly complex: hyperopia, astigmatism and presbyopia are difficult to correct simultaneously; The "multifocal" correction, in particular, may cause some degradation in the correction of astigmatism.

  62. NEPHEW says:

    Hello
    My 2.50-year-old daughter has a prescription:
    OD + 3.75 (-0.75 to 25 °)
    OG + 4.50 (-1.25 to 160 °).

    The optician sold US glasses to
    OD + 3.00 (+ 0.75 to 115 °)
    OG + 3.25 (+ 1.25 to 70 °)

    Is that normal?
    Thanks in advance for your help.

  63. Dr. Damien Gatinel says:

    This formulation is normal and equivalent to the first. The formulation of opticians for the manufacture of glasses with astigmatism correction is in "positive cylinder", while the Ophthalmologistes perform the "negative cylinder" requirements. Néanmmoins these two forms of writing are perfectly equivalent here: the optician simply transposed the written formula into a negative cylinder into a formula written in a positive cylinder.

  64. Kamakshi says:

    Hello doctor,

    Does this change in prescription seem plausible to you?

    En 2013:
    OD + 2.00 + 0.25 55 ° Add 1.75
    OG + 1.25 + 0.50 100 ° ADD 1.75

    En 2019:
    OD + 2.25 + 0.25 180 ° ADD 2.25
    OG + 1.75 + 0.25 100 ° ADD 2.25

    What appeals to me in particular is the very important change of the axis for OD.

    My new glasses I've been wearing for three days don't give me full satisfaction without it being catastrophic either.

    Thanks in advance for your help.

  65. Dr. Damien Gatinel says:

    The axis change is important, but the magnitude of astigmatism is low (0.25 D) and is located in the "background noise" of refraction. Very slight acccommodation efforts, variations in instrumental measurement and other mechanisms are likely to explain this change.

  66. Betty says:

    Hello
    My son from 6yrs and 4mois has a prescription:
    OD + 4 (-3 to 20 °)
    OG + 3 (-3 to 0 °)

    I would like to know if the thickness of the correction lenses would be important and the blow uncomfortable and unaesthetic. What alternatives in this case ?
    Ps: This prescription dates from yesterday. (That worries me)
    Thank you for your help.

  67. Dr. Damien Gatinel says:

    This requirement should provide a slight increase in the horizontal diameter of the eyes, but without a very unsightly character. It is important that your son corrects this pronounced astigmatism to benefit from a good vision.

  68. Amel says:

    Hello
    My 3-year-old daughter had a prescription:

    + 2 (-1.75) 180 °
    + 2 (-1.75) 180 °

    Is astigmatism important? Will she have to wear glasses permanently?

    Thanks in advance for your help

  69. Audrey says:

    Hello
    I just got out of the ophthalmologist with a new prescription, and this one intrigues me... I have not found an answer to my questions, maybe you can help me?

    Here are my last three prescriptions, obtained from 3 different physicians (removals..).

    In 2014:
    OG:-3.75
    OD:-3.75 (+ 0.5 to 160)

    In 2016:
    OG:-4.00
    OD: – 4.00 (+ 0.75 to 160)

    Today:
    OG:-4.50
    OD:-3.50 (-1.00 to 85)

    I have no concern for the left eye who loses steadily over time, but I am puzzled for the right eye. The first two prescriptions were quite close, but for the last one the myopia seems to have improved, as for the astigmatie the sign is reversed and the angle does not have much to see... This intrigues me all the more because I consulted for a loss of vision to the left eye, I do not feel any particular discomfort to the right eye with my current glasses...

    Is it normal, is it another notation, or is it a mistake on the part of my ophthalmo?

    Thank you for your answers.

  70. Paul says:

    Hello doctor,

    I just got a prescription:
    OD: + 2.00 IN (-0.25) 90 °
    OG: + 1.75 (-0.75) 55 °
    Addition: + 2.50

    In 2017:
    OD: + 1.75 IN (-0.25) 140 °
    OG: + 1.75 (-0.50) 50 °
    Addition: + 2.50

    OD: 140 ° in 2017 and 90 ° in 2019. Is that normal?

    Thanks in advance for your lighting.

  71. Dr. Damien Gatinel says:

    The difference you make is noticeable, but not a significant change in your vision. It does not really appear outside the range of confidence allowed for the repeatability of the measures, especially in the context of the determination of a correction of the hyperopia.

  72. Dr. Damien Gatinel says:

    The formulation of your last correction of the right eye is expressed in negative cylinder Convention, while the previous corrections were reported in positive. In this last Convention (positive cylinder) the correction of the left eye becomes; -4.50 (+ 1 x 175 ̈). The astigmatismea a little increased, delightful that myopia. This evolution is somewhat parallel to that of the left eye: gradual increase of myopia.

  73. Dr. Damien Gatinel says:

    This astigmatism is important enough for it to be necessary to wear glasses not permanently in order to ensure a good visual development. There are, however, more pronounced astigmatisms in children, and there is no need to worry too much. It is rather beneficial that this astigmatism was discovered early enough to be corrected and allow the vision to develop well. Congenital astigmatism usually does not escape, your child is born astigmate, and will remain so; If, at adult age, an intervention is desired and possible.

  74. Arnaud says:

    Hello

    I get out of the ophthalmo with a prescription where he is enrolled:
    OD: (-0.25 to 151)
    OG: (-0.5 to 10 °)

    The 151 disturbs me because I see elsewhere only danaipour where the axis is rounded a multiple of 5, plus it lacks the symbol °.
    Is it consistent with you or is it possible that it is a typing error? If the 1 to took the place of the ° and that it is 15 ° I would look fine with my 151 °...

    Thank you in advance.

  75. Lebris says:

    Hello doctor,

    Thank you very much for the time you devote to answering questions from Internet users!

    I would also have some thorous questions regarding my correction for lenses:

    Flexible toric Rx monthly lenses
    OD: + 2.75 (-3.50 to 175 °)
    OG: + 3.25 (-3.50 at 5 °)

    I have been wearing these lenses for about 10 years, with no particular problem.

    1/for about 2 years, I have to return to the supplier 1 lens on 3, because my vision is a little blurry (corrects by rubbing the eyelid, then becomes blurred again) with some lenses of the lot. I do not understand that this problem only appears with some lenses of the same box, sometimes OD, sometimes OG... is this common? How to solve this problem?

    2/following a parameter error this time, I received a straight lens with a 5 ° axis instead of 175 °, do you think it might still suit or is it not possible to know before starting the box?

    3/What are the hopes that surgery can bring with such a correction?

    4/one often hears about a "capital" lens, what is the indicative average duration of the lens port in an individual and how to know if one has reached this "cut off"?

    A big thank you for your lights,

    Well yours,

  76. Dr. Damien Gatinel says:

    The change of axis can impact a priori (180 ° and 0 ° are identical, 5 ° and 175 ° close enough). The comfort of the toroidal lens is often altered by the geometry of the lens, and case rotation of it, it may be less and the vision reduced. The surgery gives very good results for the correction of astigmatism; a precise balance sheet is required to verify your operability. The lens capital is unique to everyone, it is not possible to predict it individually, some patients wear their lenses all life.

  77. Dr. Damien Gatinel says:

    You are right, you should check the value of the prescribed axis, a call to your OPH should confirm this.

  78. Little says:

    Hello
    Is it possible to have keratocoma at the age of 6?
    My son was detected astigmatist at the age of 3,
    Its current corrections are:
    Right Eye: $2.75 (-5.25) 10
    Left Eye: 1.50 (-6.00) 175

    We had to change ophthalmologist because ours has retired and today my new ophthalmologist tells me about keratocoma on both eyes while my son's corrections are still the same.
    So he sends me to a colleague has him to take more measures visibly.
    Can you give me your opinion?
    Thank you very much.
    Kind regards

  79. Dr. Damien Gatinel says:

    as soon as case keratoconus have been described in very young children, each time they were (as in adults) keratoconus induced by eye rubbing excessive vigorousness (themselves caused by other eye causes). The stability of your child's astigmatism is more of a congenital cause, which should not evolve in a pejorative manner.

  80. Adil says:

    Hello doctor,
    Here are my last three prescriptions, obtained from 3 different DPOs:

    In 2017:
    OD : -1.00 ( -0.75) 95°
    OG : -0.50 ( -0.50) 140°

    February 2019 :
    OD : -1.00 ( -1.00) 105°
    OG : -0.75 ( -0.75) 10°

    I changed my glasses in mid-March 2019. A few days later I started to have light sensations of vertigo/balance problems, especially when I walk.
    (No inner ear problems / brain MRI: no abnormalities)
    I decided to consult another DPO, result:
    OD : -1.00 ( -1.00) 100°
    OG : -0.75 ( -0.50) 135°

    I noticed the difference in the astigmatism axis. Following this, I took back my old glasses two weeks ago, with, the problem persists but less than before.
    Knowing that a DPO has already informed me that I have a poor tolerance for astigmatism. Do you think that these feelings of vertigo/balance problems are related to this?
    Thank you in advance.

  81. Lakhal says:

    Hello doctor,
    After 2 successive consultations (to be more sure of the values), I had different values:
    1st consultation: OD: 175°(-0.5) OG:175°(-0.5)
    2nd consultation: OD: (9°-0.5)-0.25
    OG:(180°-0.25)-0.25
    Are the values of the 2 consultations close? I don't know which ones to choose anymore. I am afraid of over-correction, I don't have the impression that I see poorly or blurred, it's just fatigue and a feeling of heavy eyes in concentration that pushed me to consult...
    P.s.: for the first consultation, they didn't make me dilate my pupils (I'm 25 years old), the second one, if!
    And thank you

  82. Dr. Damien Gatinel says:

    These two corrections are indeed quite close, and within the limits of approval that we observe in terms of refraction (optical correction) of human eyes. They should give you better visual acuity, especially when the brightness decreases.

  83. Dr. Damien Gatinel says:

    The main difference between these corrections is the one of February 19, for the left eye. If it is as a result of this change that the disorders appeared, then it is possible that they are related to a poor correction of astigmatism.

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