IN THE NAME OF GOD Astigmatic correction before &during phaco emulsification Sh.Hanjani , M.D

 In modern phaco surgeons no longer seek to avoid inducing ast  In modern phaco surgeons no longer seek to avoid inducing ast. but rather must address to reduce significant pre-existing cylinder. Patients have now come to judge the success of their surgery largely by their refractive result.

1- Placing the incision upon the steep meridian  Several different methods may be employed to achieve this goal . 1- Placing the incision upon the steep meridian 2- Varying size and design of incision . 3- Relaxing incisions . 4- Toric intraocular lens . 5- Bioptics approach (excimer laser or other keratorefractive modality).

In conjunction with cataract surgery Incisional procedures can be used to reduce or eliminate astigmatism.  The most common incisional surgery for the correction of astigmatism associated with cataract surgery is the limbal relaxing incisions (LRIs).  LRIs for the correction of mixed ast. can be very safe , inexpensive , useful technique for surgeons experienced in incisional surgical techniques.

 Arcute incisions and transverse incisions are both placed in the steep meridian of the cornea.  Both techniques flatten the steep meridian of the cornea and cause steepening of the opposite meridian (coupling).  Although the coupling ratio can be quite variable,in general the meridian of the incision will flatten approximately 2 to 3 times as much as the opposite meridian will steepen.

 At study in eyes undergoing phaco , evaluated the efficacy of paired intraoperative arcuate keratotomy combine with 3.5 mm limbal steep axis clear corneal incision.  Arcute incisions were performed in the steep axis at 7 mm optical zone based on lindstrom nomogram ( after 8 weeks ).  Arcute group 2.28 1.02 D (1.26 D)  S Arcute group 2.04 1.55 D (0.48 D)

Limbal Relaxing Incisions  The notion of Astigmatic relaxing incisions in cataract procedures : Osher mid .1980.  For many years corneal incisions done at 7 mm optical zone . Although effective , causes irregular ast.  More recently , a number of authors have recommended moving these incisions out to the peripheral cornea .Indeed these LRI are proving to be a less demanding and more forgiving approach to Ast.

LRIs advantages - Technically , they are easier to perform . - Less likely to cause a shift in the resultant cylinder axis (deminished need to centration). - Technically , they are easier to perform . - Patients generally report less discomfort. - Coupling ratio ,(1:1 ratio) negligible change in spheroequivalent (no need to adjust the IOL power) - Peripheral incisions are less powerful but are still capable of correcting up to 3-4 diopters.  For these reasons more refractive surgeons now prefer LRIs for all patients.

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