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Lenticular Astigmatism and Lasik

Lenticular astigmatism - an irregular lens within the eye - is a special challenge for Lasik patients.

Topographical map of a central island after Lasik  
Lenticular astigmatism is an irregularity at the lens within the eye.  

Types of Astigmatism

Astigmatism when applied to the cornea means that the cornea is not spherical like the top of a ball, but oblong like the back of a spoon. Lenticular astigmatism means that the natural crystalline lens of the eye is not perfectly symmetrical front and back, but the crystalline lens is misshaped similar to the back of the spoon example.

Astigmatism Correction

Astigmatism, no matter the source, causes light passing through the cornea to focus at more than one location on the retina, causing blurred vision and sometimes ghosting. Astigmatism is a refractive error that can be corrected with glasses, contacts, or refractive surgery like Lasik, Bladeless Lasik, LASEK, and PRK, but there are important limitations on the correction with refractive surgery.

P-IOLs do not have astigmatic correction available, so a P-IOL cannot correct astigmatism in the cornea nor in the lens.

Correction at the Lens

It is currently impossible to correct lenticular astigmatism at the crystalline lens without removing the lens and replacing it with a new plastic or silicone intraocular lens (IOL). It is impossible to just fix the crystalline lens; the crystalline lens must be replaced. This replacement is the same process as cataract surgery, but when there is no cataract it is called Refractive Lens Exchange (RLE). Due to other considerations, RLE is not always appropriate to correct purely refractive errors.

IOLs do not have astigmatic correction available, so an IOL cannot correct astigmatism in the cornea, but can resolve astigmatism in the lens by replacement.

Correction at the Cornea

Corneal based refractive surgery is able to correct corneal induced astigmatism at the source. It is also possible to correct for lenticular astigmatism by "overcorrecting" in the cornea to accommodate the lenticular astigmatism. In most refractive surgery cases, the desire is to correct all astigmatism no matter the source. This provides the patient with the most clear vision possible.

Think of the eye as having two lenses, one is the cornea, the other is the crystalline lens. If the lens has an error of, say -1.00 diopter astigmatism, then the cornea could be changed +1.00 diopter to provide zero net astigmatism and a clear view. This is like saying that if you can't raise the bridge, lower the water.

If the patient has lenticular astigmatism and the lenticular astigmatism is corrected at the cornea, then when the crystalline lens is replaced with an IOL for RLE or cataract surgery, the corneal correction that includes the correction for the lenticular astigmatism becomes an "overcorrection" at the cornea.

There are many ways to accommodate this situation and much depends upon the individual patient's circumstances. Obviously, someone with significant lenticular astigmatism could simply not have refractive surgery. If the patient is nearing the age of cataract development or is fully presbyopic, RLE is a possible option. The patient could have only the astigmatism in the cornea removed, but this may provide poor vision because the astigmatism in the lens may cause blurry vision or ghosting. The patient could have both corneal and lenticular astigmatism corrected at the cornea, and then have the cornea corrected again after RLE or cataract surgery.

Lenticular astigmatism is easily diagnosed before surgery and is just one of the many considerations that must be evaluated for every patient. A patient with lenticular astigmatism should discuss the situation with his or her doctor and come to a decision that best fits the individual patient's needs and desires.

Looking For Best Lasik Surgeon?

If you are ready to choose a doctor to be evaluated for conventional or custom wavefront Lasik, Bladeless Lasik, PRK, or any refractive surgery procedure, we recommend you consider a doctor who has been evaluated and certified by the USAEyes nonprofit organization. Locate a USAEyes Evaluated & Certified Lasik Doctor.

Personalized Answers

If this article did not fully answer your questions, use our free Ask Lasik Expert patient forum.

Recent Lenticular Astigmatism Medical Journal Articles...

Related Articles

[Internal astigmatism with other ocular lesions].

J Fr Ophtalmol. 2012 Apr;35(4):277-83

Authors: Limaiem R, Baba A, Bouraoui R, Mghaieth F, El Matri L

Astigmatism is a refractive defect whose origin is not always purely corneal, and is sometimes the result of corneal, crystalline lens or mixte contributions. The aim of our study is to report, through two cases, ocular lesions associated with a lenticular astigmatism and their evolution after treatment. In the first observation, it is a 25-year-old patient with a unilateral extra corneal astigmatism within the framework of the "tilted disc syndrome" associated with bilateral myopia. This patient has received treatment by Lasik. The postoperative course was good with a decline of 5 ans. The second observation is that of a patient aged 35 years without having a general history with a posterior lenticonus associated with keratoconus responsible for a major mixed astigmatism. She received combined surgery: penetrating keratoplasty with lens extraction and implantation of an artificial lens. The evolution was good with good visual recovery. The balance of internal astigmatism must include the systematic achievement of a subjective and objective refraction under cycloplegia and corneal topography. The search for etiology is critical to screen for eye or general disease and guide the therapeutic strategy. Knowledge of the refractive power of the cornea and crystalline lens of astigmatism separately would be important for surgery refractive and crystalline lens surgery.

PMID: 22424808 [PubMed - indexed for MEDLINE]


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