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LASIK and corneal thickness

Thickness of the cornea and LASIK possibility

The thickness of the cornea is important in surgery LASIK, especially for short-sighted. Some patients, surgical candidates, are left out of the LASIK technique because "their cornea is too thin. Others may benefit from LASIK, even for a high myopia, because the cornea is thick enough. The technique of PKR (surface laser) is available to some ineligible myopic LASIK (low and medium myopia).

Legitimate questions arise from this type of verdict: why is the thickness of the cornea in some insufficient case? Is there a limit of thickness below which LASIK is impossible?  To appreciate the role of corneal thickness in the choice of the refractive surgery technique, it is important to understand the mode of action of LASIK, and familiarize themselves with certain data about the biomechanical resistance of the cornea: this page is dedicated to this goal.

What is the thickness of the cornea?

The cornea is a generally hemispherical dome whose thickness decreases from the edges toward the Center. When we're interested in the thickness of the cornea, it is usually the thickness of its "central region".

We can measure the corneal thickness in different ways:

-corneal product: this is rather imprecise (it does measure the thickness that at a given point)

-Topographical maps in thickness (corneal tomography): these maps allow to analyse thickness corneal "point by point", and get a map "point by point", which notably allows to determine the value of minimum thickness and contact information.

-OCT cards, which provide the same information as the tomographic maps, and will in the near future to achieve specific maps of the epithelial thickness. OCT 'online' technique allows to measure the thickness of the cornea during LASIK surgery real-time: it equips the latest platforms (ex: Alcon Wavelight EX500)

 

Here is an example of map of thickness (CT) corneal:

Map of corneal thickness (Corneal Thickness). Superimposed on the color statement numbers correspond to local values. The corneal thickness value next to the apex, as well as the minimum thickness are mentioned in the left sidebar.

Map of corneal thickness (Corneal Thickness). Superimposed on the color statement numbers correspond to local values. The corneal thickness value next to the apex, as well as the minimum thickness are mentioned in the left sidebar.

In the population known as "caucaseienne", free corneal pathology, theminimum thickness of the cornea is close to an average 550 microns  (see:)   http://www.IOVs.org/content/51/11/5546/T2.expansion.html), with a standard deviation of 35 microns about.

Thus, close 70% of the myopic patients have a central corneal thickness of at least 515 microns, and only 2.5% of the population of 'healthy' myopic eyes have less than 480 microns thick (95% of the eyes of a representative sample of healthy eyes have a corneal thickness between the average more or less two standard deviations, is between 480 and 620 microns about (these figures are of course rounded).) These benchmarks are specific to the caucaseienne population; native populations of the Maghreb and the Indian continent have a corneal thickness lower than average. Patients with Keratoconus, even beginner (ex: forms frustrated), have a reduced average corneal thickness (525 microns).

The cornea is composed of several tissue layers, which are the three principal: (on the surface) epithelium, stroma and endothelium.

Among the various layers of the cornea, the stroma is the thickest: it was she who is carved by the during the LASIK excimer laser

Among the various layers of the cornea, the stroma is the thickest: it was she who is carved by the during the LASIK excimer laser

The thickness at the center of the corneal epithelium is understood between 40 and 60 microns (or nearly 10% of the total corneal thickness). Unlike the stroma, the epithelium is a purely cellular tissue, which has the ability to "push back" after debridement. That is why it would be unwise to issue the correction laser directly on the epithelium, because the printed effect would disappear in a few days as epithelial regrowth. The endothelium has a thickness of only a few microns. 90% of the thickness of the cornea is so filled by tissue stromal (or stroma) of the cornea, which is made up of collagen fibers intertwined.

What are these fibers which are subject to certain biomechanical constraints: intraocular fluid (aqueous) pressure exerted on the internal face of the cornea, so that its outer side is the contact of air and is under atmospheric pressure. In addition to the importance of the natural stiffness of the collagen fibers of the stroma of the cornea, the thickness of the "lattice" they are involved in maintaining the harmonious shape of this transparent fabric.

 

Correction of myopia and thickness of the cornea

The correction of myopia (excess of optical power of the eye) in LASIK involves a sculpture to sight refractive (laser photoablation), designed to change the corneal profile: reduction of the curvature of the cornea causes a reduction in the power of the cornea, which must be equal to preoperative myopia.

The characteristics of the profile of laser photoablation cause one photoablation maximum Center of the cornea. However, we have seen that the center of the cornea is naturally the finest region. By technique LASIK, the laser correction is issued under a previously realized flap (to the) femtosecond laser in modern centers) then recline, before be repositioned after the operation. The flap, whose thickness is chosen by the surgeon (around a value of 110 microns in general) is composed of a bilayer tissue: the epithelial layer on the surface, and the layer stromal shallow in depth.

To correct a dipotrie of myopia, thin the center of the cornea about 14 microns on a 6 mm optical zone (this value is approximate and depends on the corneal Asphericity initial and final target): http://www.IOVs.org/content/43/4/941/F3.expansion.html. During the programming of the correction in the excimer laser ablation maximum depth is displayed (ex: 70 microns for a correction of 5 diopters). Some lasers have tissue saving program: these programs are actually software changes designed to reduce tissue cost that was initially higher with these lasers to dictate what the laws of physics with first generation lasers. Modern lasers use by default the most fuel-efficient ablation strategies in tissue (corneal)to learn more about the strategy of economy of fabric / fabric saving claimed with the Zyoptix correction and compare "tissue cost" with some platforms lasers)

The thickness of the tissue removed is not the only one given position to determine the biomechanical impact of the laser photoablation. The volume occupied by the stromal to the flap contingent is relatively consistent, and often far exceeds the volume of cornea removed by laser excimer for the correction of myopia. This arises from the constant thickness of the edges stromal flap toward the Center, and its diameter (8-9 mm). In comparison, the lenticule of tissue removed by the excimer laser has a thickness that decreases to its edges, and a near 6 to 7 mm diameter.

We have established a simplified formula that provides the volume removed by a correction of myopia laser:

V = D (S/9) ^ 4 (V: in millimeter cube, D diopters, and S = diameter of the optical zone in mm). A diopter of myopia corrected on a 6 mm box "consumes" a volume of 0.20 stromal tissue about mm3. A LASIK flap in diameter 8.5 mm and a thickness of 120 microns (including 70 microns of stroma) represents in comparison a close volume 4 mm3 (equivalent to a correction of 20 diopters). Even if this flap is back in place, the fibers that make her volume no longer participate in the stability of the corneal Vault.

The rest of flap of LASIK is done on what is called the "residual stromal rear wall", whose thickness is equal to that of the cornea before the operation under the flap, and less of the photoablation. The predicted this posterior residual wall thickness value is an important factor in operative planning.

Residual wall posterior stromal

It is considered as the flap of LASIK, even rested, no longer significantly involved to the biomechanical strength properties the corneal dome after the operation. The posterior residual wall only helps maintain the rigidity and the curvature of the cornea.

Corneal posterior residual wall thickness depends on the thickness of the LASIK flap and the thickness of the myopic photoablation

Corneal posterior residual wall thickness depends on the thickness of the LASIK flap and the thickness of the myopic photoablation

 

It is logical and intuitive to apply that This rear wall must not be too thinto resist the constraints that represent intra ocular, to potential eye rubbing digital repeated pressure, etc.

Some experimental studies and clinical data accumulated over time suggest to actually maintain a sufficient residual thickness at the center of the cornea, to avoid that eventual permanent progressive deformation of it occurs: we call this (fortunately rare) complication thecorneal ectasia.  This permanent deformation is a result of a phenomenon akin to a "creep".  even if the permanent constraints suffered by the cornea (mainly related to the intra ocular pressure, which corresponds to the force exerted on a surface unit) does not reach the "yield strength" (stress from which a material's deforming in a reversible manner - elastic), she can start to deform irreversibly over time in the same way as a shelf bearing many books, can "bend" gradually.

There is a consensus among the community of refractive surgeons to consider that the Central wall thickness residual posterior stromal in LASIK must be at least equal to 250 microns (nearly half of the initial thickness of the corneal stroma). This value is empirical, and stems from observations of case of "decompensation" more or less late of the biomechanical resistance of the cornea for less than that value residual thicknesses (thirty years ago, a now abandoned technique was to voluntarily induce a 'ectasia' to correct hyperopia, by cutting a very thick flap, of the order of 350 microns or more) ", leaving a very thin residual wall). Some surgeons recommend a residual thickness of posterior wall of 300 microns, in particular for corneas with less than average initial thickness.

This video shows the creation of a constant monitoring of the product (Central corneal thickness measured by OCT 'online pachymetry' technology laser excimer Alcon Wavelight EX500) during LASIK surgery.  The treatment of myopia of-6.75 D imposes Central removal of 99 microns deep. The initial thickness of the cornea at the Center's 530 microns. A posterior residual wall more than 300 microns is preferred for this eye: scheduled flap of LASIK with femtosecond FS200 laser thickness is 120 microns. The first measurement is done just after the creation of the interface with the femtosecond laser and found about 550 microns thick (this thickening is related to the diffusion of water in the interface during the creation of the flap). After the uprising of the flap, a new measurement is performed, until the photoablation is issued. At the end of it, and before the rest of the flap, a final measure of the residual rear wall is completed.

However, things would be too simple if the feasibility of LASIK depended only on the residual thickness of the posterior stromal wall... The lift of a shelf does not depend only on its thickness: the quality of the material put into play in its construction is obviously guarantor of its resistance to the weight carried. The same goes for the cornea: the thickness of the corneal wall isn't the only component to be considered to determine operability in LASIK : the intrinsic "quality" of the corneal tissue (stromal fibers, they even made up of collagen fibrils) is intuitively a given importance. Even if the calculation of the residual thickness of posterior stroma provides a reassuring figure, he must eliminate the presence of a biomechanical intrinsic fragility.

 

Thickness and biomechanical quality of the cornea

Keratoconus is an exemplary pathology to illustrate the importance of the integrity of the structural properties of the cornea.  Any of the causes of Keratoconus remains unknown. Biomechanical measures (ex: Ocular Response Analyser) show an early modification of the biomechanical properties of the cornea in Keratoconus. the hysteresis, i.e. the ability to absorb the energy of a constraint as a jet of air pressure is reduced. This is related to a reduction in the 'strength' of the corneal tissue; Collagen fibers are disorganized, disunited, and lose their arrangement harmonious because they "slide" more easily on top of each other. This causes a progressive deformation spontaneous, responsible for a astigmatism irregular, and the resurgence of progressive myopia.

Keratoconus is a contraindication for LASIK, whatever the central cornea thickness (the thickness is usually reduced over the course of the disease). Them Beginner forms of Keratoconus must absolutely be tracked in the preoperative consultation, because thinning caused by a LASIK would reduce even the resistance of the corneal dome and would accelerate the strain of it, realizing the clinical picture of post LASIK ectasia.  Corneal topography, supplemented by biomechanical measures (ORA), is systematic;  It must include an analysis of the posterior side of the cornea, as well as its variations of thickness of the edges to the Center (CT). The use of modern testing indices is indicated (ex:) SCORE Analyzer)

It is important to note that the main risk factor for the ectasia is the presence of a form no diagnosed of Keratoconus, and no excessive thinning of the residual wall rear induction ! The appreciation of this point is complicated because the early forms of Keratoconus are usually associated with a lesser thickness of corneal tissue! However, many case of ectasia are seen on eyes which the posterior residual wall has a close or even superior to 300 microns thickness, but the retrospective analysis of the topographic maps obtained before the procedure reveals the presence of a beginner not tracked Keratoconus.

 

Conclusion

The indication of a LASIK depends on many parameters and respect for the contraindications of this technique.

The initial thickness of the central cornea imposes certain limits, since it must ensure that the degree of correction to carry out will not lead to a depth of ablation laser which, added to that of the flap, will leave a residual rear wall at least equal to 250 microns.

Even if this condition is satisfied, it is crucial to eliminate the presence of a fledgling form of Keratoconus (beginner infra clinical Keratoconus). Regardless of the corneal thickness and the degree of correction, need not perform LASIK, and possibly direct the patient to a surface technique (PKR), without cutting of flap. The fact that the corneal ectasia is essentially observed after LASIK (the case of ectasia after PKR are exceptional in comparison) accredits the assumption that the cutting of the flap is an important causal factor (remember that the volume of the flap exceeds the cornea removed by the laser to correct nearsightedness).

In case thin cornea (ex 510 microns), and unscathed from a beginner Keratoconus type pathology, it is not possible to correct as many short-sightedness in thick cornea case (580 microns).

For example, if a myopia of 6 diopters, corrected on an area of 6 mm photoablation implies a central tissue ablation of 85 Micron and to maintain a wall of residual stromal thickness of 300 microns, with a LASIK flap of 120 microns, it will take that preoperative corneal Central thickness is at least 505 microns. The thickness of the flap is today determined with precision with femtosecond lasers: Unfortunately, the mechanical microkeratomes, still used today in some centres, are less accurate and sometimes induce cuts of greater than expected thickness (ex: 170 microns instead of 130 microns).

 

 

 

 

50 responses to "Lasik and corneal thickness"

  1. Helen says:

    Thank you for this very comprehensive article!

  2. n says:

    Hello doctor, to the product measures were to:
    Og: 461 Microns
    Od: 471 microns
    My myopia is – 3.75 in both eyes, am I a candidate for refractive surgery??? Thank you for your reply

  3. Dr. Damien Gatinel says:

    You are potentially eligible for the technique of PKR (surface laser). However, LASIK is indicated in your case. The results of the correction in PKR for this type of myopia are generally satisfactory.

  4. C.bou22 says:

    Hello doctor,
    I'm 35 years old. I am myopic and astigmatism: OD: 4.75 (1.75; 10) OG: 5.75 (1.75; 175). I also have a corneal thickness of 486. Do you think I can benefit from refractive surgery?
    Thanking you.

  5. Dr. Damien Gatinel says:

    In your situation, a technique of PKR (surface laser) can be possibly considered, by reducing the size of the optical zone, which may however increase the risk and halos of light under correction (particularly on the left side).

  6. Louise says:

    Good evening, doctor.

    I am 26 years old and am nearsighted and astigmatism:
    -9.5 in both eyes.
    At the Pachymetry, the results were as follows:
    OD: 538
    OG: 544.1
    Of course, the supplements of the exam are necessary to you but on the basis of this information, do you think that I would be able to do surgery?
    Thank you very much in advance.

  7. Dr. Damien Gatinel says:

    The technique of LASIK is potentially feasible in your case, if the corneas do not exhibit any particular irregularity. Their thickness is sufficient for a complete treatment, subject to making a fine flap. To check these points, a successful topographical examination is required.

  8. Agathe says:

    Hello doctor,
    I'm, 25 years old, and I'm myopic:
    OD:-8.50
    OG:-6.50
    At the pachymetry, measurements are 530 microns.
    Do you think surgery would be feasible?
    Thank you

  9. Dr. Damien Gatinel says:

    If this thickness of 530 microns is central, that the corneas are regular (you do not rub or often eyes), and that the laser center you are considering is equipped with the laser femtosecond for the realization of the LASIK condoms, then a priori , the intervention is possible. However, a detailed balance sheet is needed to confirm this.

  10. Asma says:

    Hello doctor,
    I just did 2 consultations in two different laser centers. One advocates me the PKR technique (horny too fine according to him) and the other the LASIK laser... I wanted a second opinion to be certain of the choice of the first doctor and well that finally did not help me. I had very good feedback on the two centers.
    What do you think, please? Do I have to do a third center?
    Thickness of my rope: OD 517 and OG 513
    I am myopic and astygmate, my correction: OD-4.50 (cyl-1.25/AX 180) and OG-4.25 (cyl-1.75/AX 170)

  11. Dr. Damien Gatinel says:

    It is difficult to give you a definitive answer because the central corneal thickness is not the only determinant of the choice between PKR and LASIK. The regularity of the corneas in topography is a no less important criterion. There may be differences of opinion between the practitioners you have consulted. If the corneas have a satisfactory topography, LASIK can be performed for this correction, provided that the use of a newer equipment (laser femtosecond especially to be sure to achieve a flap).

  12. Angel Koasix says:

    Hello doctor,
    I'm 27 years old.
    I do in: OG:-6 SPH:-0.50 and OD:-5.75 SPH-O 25.
    Am I fit to apply for surgery to an ophthalmologist?
    What type of surgery would allow me to no longer be dependent on glasses.?
    What are the risks?

    Thank you Doctor

  13. Dr. Damien Gatinel says:

    This degree of correction is operable in LASIK, provided that there is no particular ocular anomaly, and a normal corneal thickness. You have to make a preoperative assessment to be fixed.

  14. Agnes says:

    Hello doctor,
    I'm 32 years old and I'm myopic
    OD: – 8.50
    OG:-9.00
    At the pachymetry the measures are
    OD: 591 microns
    OG: 592 microns
    Do you think surgery would be feasible and what kind of surgery would suit me?
    What are the risks?
    Thank you

  15. Dr. Damien Gatinel says:

    LASIK surgery is a priori possible in your case, because your corneas have a thickness above average. To correct 10 diopters over a diameter of 6.5 mm (optical area), a maximum ablation depth of approximately 140 microns will be required. If a corneal flap thickness of 110 microns is added, it will remain a residual wall much higher than 300 microns. A corneal topography is however necessary to check the regularity of your corneas and validate the indication of LASIK.

  16. Claire says:

    Hello doctor,
    J envisages refractrice Surgery of my myopia + astigmatie stabilized
    OD =-5.5 (-2 to 25) 10/10 P2
    og =-6 – 0.5 to 170) 10/10 P2
    But a priori Pachymetrie limit to 500 micro ODG
    Would the LASIK technique be conceivable, admitting a satisfactory preop explosion?
    Kind regards. Thank you for your answer

  17. Dr. Damien Gatinel says:

    The realization of a LASIK is not excluded in your case, provided that the topographic examination is perfectly normal otherwise, and allows to conclude to a relative congenital finesse of the corneas, and not to a secondary thinning ( Often related to the practice of repeated eye rubbing, for allergies, irritation, dryness, fatigue, etc.)

  18. Sabah says:

    Hello Doctor:
    I am 26 years old and I am myopic and astigmatism at the same time: OD =-6 (-1 to 20 •) and-8 (0.75 a 180 •) I have a thickness corneal od: 491 OG: 493 I already consulted two ophthalmologists the first M said I can Not do LASIK and that the only solution is the ICL implants, and the second MA dis I can do with the smile technique, and I want to know your doctor opinion

  19. Dr. Damien Gatinel says:

    When LASIK is contraindicated (which is the case at home) for thick reasons, the smile is also. The smile will not be able in your case to ensure the persistence of a sufficient residual thickness if the LASIK can not. At 26 years old it is however a little early to consider the installation of ICL implants. It is best to continue wearing the lenses for a few more years.

  20. MACHA says:

    Hello

    Thanks for this article!
    A small question, for the smile technique, the thickness of the cornea must be how much?

    Thank you very much for your reply

  21. Dr. Damien Gatinel says:

    The corneal thickness prerequisites are the same in smile and LASIK. For the same myopia, and the same optical area, the depth reached in smile in the cornea is generally higher than that of LASIK, as it is necessary to add 15 microns to the duckweed removed (so that the edges do not tear during the resection). In addition, the "roof" above the removed duckweed is thicker than a femtosecond laser-made LASIK flap. Some theoretical models suggest that working "in depth" in smile would be less biomechanically detrimental... But this remains to be clarified, and in practice, we must observe the same precautions in smile and LASIK (leave an adequate posterior wall in all case).

  22. JONA says:

    Hello doctor,

    I want to have myopia, but I have the thickness of my cornea too low. When I wear lenses it hurts, I deduce that the thickness of my cornea is really fine no? What do you think?
    Moreover, is it true that the thickness of the cornea becomes thicker over the years?

    Thank you very much in advance!

  23. Dr. Damien Gatinel says:

    In reality the thickness of the cornea has no connection with the comfort of contact lenses. Only an examination of corneal topography (or pachymetry, a simple measurement of the thickness) can inform you about the measurement of the thickness of your cornea and the possibility of benefiting from refractive surgery.

  24. Arthur says:

    Hello doctor,

    I'm 21 years old and I'm myopic
    OD: SPH. -8.75 Cyl. -0.25 Shaft 180 °
    OG: SPH. -8.25 Cyl. -0.25 Shaft 165 °
    At the pachymetry the measures are
    OD: 480 microns (Thinnest point 475 micron)
    OG: 512 microns (Thinnest point 496 micron)
    Do you think a laser operation would be feasible and what type of surgery would suit me?
    Thanks in advance

  25. Dr. Damien Gatinel says:

    Unfortunately, LASIK is contraindicated in your case because the right eye does not have enough thickness to allow you to be corrected in safety.

  26. Simon Keith says:

    Hello

    Thanks for the work done on this site, it's very informative.

    I am 27 years old and I have planned a 100% Lasik operation in late September in Paris. I'm myopic:
    OD-3 (-0.25 to 160 °)
    OG-2.75 (-0.25 to 40 °)

    The corneal topography is "perfect" (I quote my ophthalmologist), the bottom of the eye revealed a few holes in the retina of the left eye that were treated by photocoagulation.

    However the thickness of the cornea is quite small, around 505 to both eyes. He tells me that it is at the limit but still recommends me Lasik rather than a PKR, for my comfort.

    I'd like a second opinion. Thanks in advance!

  27. Dr. Damien Gatinel says:

    A priori, if your corneas are regular (and it is certainly the case unless you rub or you are rubbed your eyes chronically and vigorously, cf allergies etc.), the thickness is sufficient for a LASIK in any Security. The most important thing is not to rub your eyes in postoperatively.

  28. Cynthia says:

    Hello
    I would have liked to know how many microns are removed to correct-6.75 LASIK on an optical area of 6.5.
    And especially how long after surgery do not rub your eyes. Thank you

  29. Dr. Damien Gatinel says:

    It is crucial never to rub vigorously, prolonged, and repeated, eyes after LASIK. To correct myopia on an area of 6.5 mm, approximately 15 microns of central ablation per diopter are Required.

  30. David says:

    Hello doctor,
    I'm 27 Years Old. I am myopic and astigmatism: OD:-10.5 (-1.5 to 160 °) and OG:-10.5 (-2.00 to 180 °). And the Escart interpupillary is: 63.0.
    At the Pachymetry the measures are:
    – OD: 510 microns at the power plant
    – OG: 515 microns at the power plant
    Do you think the femtosecond LASIK operation would be feasible?

    Thank you in advance for your answer.

  31. Aurélie says:

    Hello
    I am 33 years old and I just realized a orbscan for LASIK.
    Here's my Data:
    OD:-5.75 Horned 504 At the very end (very very light Astigmatism)
    OG:-6.50 Horned 509 at the end
    The secretary just phoned me because the operation would be "discouraged".
    In the state of the above data is Lasik or PKR feasible? I'm trying to understand thank You.

  32. Dr. Damien Gatinel says:

    The central corneal thickness is not the only parameter to be considered in determining the eligibility for LASIK. If the corneas are fine but very regular (no eye rubbing repeated in the past), it is possible to envisage a correction in LASIK a priori, may be by making certain adjustments (reduction of the thickness of the flap and/or the Optical area treated to minimize corneal volume mobilized by surgery). otherwise, a PKR must be feasible.

  33. Dr. Damien Gatinel says:

    Without being formally contraindicated, the completion of a LASIK surgery seems difficult, because the degree of total myopia to be corrected is very high, while your corneas are a little thinner than the Average. There is a high risk of under Correction. It is best to continue wearing lenses if they are well Tolerated.

  34. Melanie says:

    Hello doctor,
    I'm 35 years old and I've been myopic ever since.
    I consulted 3 surgeons: 2 recommended LASIK, and 1 rather the PKR. Could you give me your opinion please?
    OD:-8.00 (-1.25 axis 180 °)
    OG:-8.25 (-0.50 axis 10 °)
    My corneas are from (I transcribe the information provided by one of the surgeons consulted, Corneas calculated by 3 different machines):
    Pachymetry: 513/516 * (514 511/512 519)
    Pachymetry Penta: 510/519
    Thank you in advance for your opinion.

  35. Dr. Damien Gatinel says:

    If the corneas are regular, the minimum core thickness you are reporting should be sufficient to achieve a LASIK, provided you use femtosecond laser Découope technology for flap Corneal (by programming a fine thickness, 100 to 110 microns) and adapting the diameter of the Excimer laser treatment area.

  36. Yaso says:

    Hello doctor,

    I have a myopia like this, right eye:-4.25 and left eye:-4.00
    A corneal thickness: right eye 469/left eye: 473
    is a femtosecond laser operation possible in my case ?
    Thank you for your time:)!

  37. Dr. Damien Gatinel says:

    A priori, it is not advisable to make a correction in LASIK in your case . On the other hand, a correction by PKR (surface laser, the cornea is sculpted on the surface, after simple removal of the epithelium) is theoretically possible in case Fine cornea and myopia less than about 6 diopters (which is your case ). It is necessary to check the regularity of the corneas in the examination of corneal topography to confirm this possibility.

  38. Mohamed says:

    Hello doctor
    I'm 33 years old and I'm nearsighted
    Od:-6
    Og:-6
    Corneal thickness D: 498
    Corneal thickness G: 491
    Am I operable with LASIK?
    Thank you
    Very interesting Article

  39. Dr. Damien Gatinel says:

    If your corneas have good regularity (no repeated friction), a LASIK can be considered, using a femtosecond laser technology to obtain a flap Thickness 100 or 110 microns. An adjustment of the diameter of the optical correction zone must allow to maintain a posterior residual wall close to 300 microns (rather "conservative" safety threshold).

  40. Bicha says:

    Hello, doctor. I have 32 and I am astigmate myopic. Od-8.25 (0-1.25). Og. -9 (175_1,25). Central cornenne thickness:. Od 504. Og 502. My doctor tells me I can make a correction but not 100% because my cornea is not thick enough what do you advise me? I want to take the glasses off:(

  41. Dr. Damien Gatinel says:

    You actually correspond to a " case limit "and if a total correction is possible, it can only be delivered on a reduced optical zone, which may cause night vision discomfort (halos). The advantages and disadvantages of such an intervention must therefore be weighed. Measuring your pupillary diameter in low light condition could be useful in predicting the impact of surgery.

  42. Me says:

    Hello
    I would like to have your opinion
    I have 34 years myopic and slightly astigmatism since the age of 18 years
    OD:-2.00
    OG:-2.25
    I performed a topography results below
    Min pachy OD: 501
    OG min pachy: 503
    Am I a candidate for Lazik?
    Thank you

  43. Arnaud says:

    Hello doctor,
    I'm 32 years old and I'm nearsighted.
    OD:-3 (-0.50) 60 °
    OG:-2.5 (-0.25) 110 °
    Corneal thickness D: 450 in
    Corneal thickness G: 449 in
    Am I operable in PKR? Smile?
    Diverging opinions my given summer and STAAR implants recommended.
    Thank you for your help

  44. Dr. Damien Gatinel says:

    The best and only technique is a priori for your case is the PKR. LASIK and smile are contraindicated, and the placement of IOLs implants is a little invasive for the correction of low myopia.

  45. Dr. Damien Gatinel says:

    The thickness of your corneas is a priori sufficient to envisage a LASIK: However, it is necessary to verify that the topographical regularity is sufficient (absence of Keratoconus type deformation fruste etc

  46. Julia says:

    Hello, what are the solutions you propose for a person with a strong hyperopia and astigmatism?
    (Sphere: +5, 00Cylinder: -1, 75Axis: 90 in both eyes) I did a laser pre-operation test a few years ago and was told that my cornea was too thin. Thank you

  47. Dr. Damien Gatinel says:

    A PKR could be considered, but the correction of strong hyperopia is more difficult (scarring tends to partially erase the effects of surgery). It is rare for the corneas to be too fine for the correction of the hyperopia, because this technique causes a peripheral thinning, not central, of the cornea.

  48. Julia says:

    Could PKR be accompanied by negative side effects due to scarring? What is the success rate of the PKR compared to LASIK? What do you think of implants? Following your reply, I will again consider the operation that I have been interested in for 10 years. Thank you. Julia

  49. Chris says:

    Hello doctor,
    I'm 27 years old

    OD: Sph:-4.50 Cyl:-4.75 axis: 11
    OS: Sph:-4.50 Cyl:-5.00 axis: 176
    Pachymetry: OD: 500 OS: 510

    Am I a candidate for Lasik?
    Thank You

  50. Dr. Damien Gatinel says:

    If your corneas are thin but regular (which suggests that they are biomechanically stable), then a LASIK procedure is theoretically possible, with about 500 microns of minimal thickness. However, one must add the magnitude of the myopic and astigmatic error to estimate the depth of laser ablation which is necessary for the full correction of your compound myopic astigmatism. It is quite plausible that to satisfy some safety rules (preserving a 280/300 residual bed thickness), the surgeon may reduce the planned optical zone (the larger the area, the deeper the ablation and vice versa). If your mesopic (dim light) pupil diameter is not too wide, a correction could be feasible on a reduced optical zone, cutting a thin flap with a femtosecond laser). But you may experience some reduction of your quality of vision at night.

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