الفهرس 
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Abstract
Astigmatism (> 0.5 diopters) is a commonly encountered refractive error, accounting for about 13 % of the refractive errors of the human eye. It is estimated that 15% to 29% of patients presenting for cataract surgery have more than 1.50 D of corneal astigmatism. As little as 0.50 to 0.75 D of uncorrected cylinder after cataract surgery can leave a patient with visual disturbances including blur, halos, and ghosting. Furthermore, in patients with multi-focal IOLs, even small amounts of residual astigmatism may reduce visual acuity noticeably, especially at near.
Aside from glasses or contact lenses, treatment options for patients with cataracts who have preexisting corneal astigmatism include excimer laser refractive procedures; astigmatic keratotomy (AK), limbal or, corneal-relaxing incisions; and toric IOLs. Corneal or limbal relaxing incisions can be used in combination with monofocal, toric, or presbyopia-correcting IOLs at the time of cataract surgery.
In astigmatic keratotomy, incisions can be limbal, arcuate, or transverse and are traditionally performed free-hand or with a mechanized keratome. The instruments used for astigmatic keratotomy are front cutting diamond blades and mechanized trephines, which can lead to corneal perforations, irregular astigmatism, undercorrections and worsening of the pre-existing astigmatism.
Femtosecond laser technology offers the ability to control the desired shape, length, radius and depth of incisions in astigmatic keratotomy. Multiple studies have found femtosecond-assisted laser arcuate keratotomy to have enhanced predictability and a reduced rate of complications.
So, we conducted this study to evaluate the safety and efficacy of single intrastromal astigmatic keratotomy during FLACS. Both control and ISAK groups showed a statistically significant improvement of UCVA and BCVA postoperatively. The ISAK showed a statistically significant decrease in refractive and topographic astigmatism postoperatively by correction index of 81%. The magnitude of error and correction index of ISAK suggested undercorrection of this technique. Both groups did not show a significant change in corneal aberrations postoperatively.
The femtosecond laser assisted intrastromal arcuate keratotomy has an excellent safety profile. In addition, patient satisfaction was very high. Overcorrection, which sometimes happens with penetrating incisions and may require suturing, was not seen in any case.
The use of femtosecond laser assisted intrastromal arcuate astigmatic keratotomy is an effective mean of correcting low to moderate degrees of corneal astigmatism, during femtosecond laser assisted cataract surgery. It has neutral effect on optical aberrations and did not change the biometry of patients.
So, We recommend using femtosecond laser in doing astigmatic keratotomy (AK). Intrastromal AK is less than penetrating AK in reduction of corneal astigmatism but with high safety profile (no wound gap, inflammation) and high patient satisfaction. We believe the astigmatic effect can be increased as we refine the nomogram and use paired incisions instead of one.