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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 20  |  Issue : 1  |  Page : 33-38

Treatment of corneal astigmatism by limbal relaxing incisions during phacoemulsification surgery


Department of Ophthalmology, Memorial Institute for Ophthalmic Research, Cairo, Egypt

Date of Submission11-Feb-2021
Date of Decision01-Jun-2021
Date of Acceptance12-Jun-2021
Date of Web Publication4-Mar-2022

Correspondence Address:
MD Hussam E.O Elrashidy
Assistant Professor of Ophthalmology at Giza Memorial Institute for Ophthalmic Research, 12511
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/azmj.azmj_22_21

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  Abstract 


Background and aim The aim was to assess the effectiveness of limbal relaxing incisions (LRIs) in treatment of astigmatism in patients undergoing phacoemulsification surgeries.
Patients and methods Forty-eight eyes of 48 patients suffering from senile cataracts of mean age 64.7±7.9 (range: 50–77) years, and mean corneal astigmatism 1.8±0.73 diopters (D) (range: 1.5–3.5 D) were included in this study. All LRIs were performed at the end of phacoemulsification. Corneal topography results were compared before surgeries and 2 and 6 months after surgeries.
Results A statistically significant reduction in the mean corneal astigmatism was seen from 1.8±0.73 D (range: 1.50–3.50) preoperatively to 1.1±0.24 D (range: 0.5–1.7) and 1.4±0.52 D (range: 0.60–1.9) in the second and sixth postoperative months, respectively (P<0.001). Surgical-induced astigmatism (the amount and axis of astigmatism change induced by surgery) was 0.90±0.48 at 2 months and 0.96±0.59 at 6 months. Correction index (calculated by determining the ratio of surgical-induced astigmatism/target-induced astigmatism) was 0.56±0.42 and 0.57±0.33 at 2 and 6 months, respectively. Index of success (ratio of topographic residual astigmatism and target-induced astigmatism) was measured to be 0.45±0.42 and 0.48±0.33 at months 2 and 6 correspondingly.
Conclusion Combined LRI and phacoemulsification appears to be safe and fairly effective to correct mild-to-moderate corneal astigmatism. However, undercorrection is a common limitation that may be further managed by modified nomograms in future studies.

Keywords: corneal astigmatism, limbal relaxing incisions, phacoemulsification surgery


How to cite this article:
Naguib MA, Elrashidy HE, Samir G. Treatment of corneal astigmatism by limbal relaxing incisions during phacoemulsification surgery. Al-Azhar Assiut Med J 2022;20:33-8

How to cite this URL:
Naguib MA, Elrashidy HE, Samir G. Treatment of corneal astigmatism by limbal relaxing incisions during phacoemulsification surgery. Al-Azhar Assiut Med J [serial online] 2022 [cited 2022 Jun 29];20:33-8. Available from: http://www.azmj.eg.net/text.asp?2022/20/1/33/339072




  Introduction Top


Nowadays, cataract-extraction surgeries are the most popular and most successful surgeries in ophthalmology [1],[2].

The aim of these surgeries is to correct any refractive errors and obtain the best acuity for the patients, and minimize the use of glasses after surgeries [3].

In order to correct pre-existing astigmatism before cataract surgeries, new techniques have been developed in order to achieve the best correction possible of refractive errors [1],[4],[5].

Postoperative astigmatism due to cataract surgery can be minimized by different techniques such as intraoperative relaxing incisions, toric intraocular lens (IOL) implantation, or postoperative vision correction by ablative–refractive surgery by excimer laser [2].

Every technique has its own benefits and drawbacks.

In our study, we will report the safety and efficacy of limbal relaxing incisions (LRIs) for correction of pre-existing corneal astigmatism at the end of phacoemulsification.


  Patients and methods Top


It is a prospective study performed from January 2019 to January 2020. The study included 48 eyes of 48 patients with senile cataracts and significant corneal astigmatism.

All patients have read and signed informed consents at their own will. The study has the Institutional Review Board approval. The study’s inclusion criteria were cataract patients aged greater than or equal to 50 years and 1.5–3.5 diopters (D) of regular corneal astigmatism documented by corneal topography. Exclusion criteria were previous ocular surgery, ocular trauma, pre-existing ocular disease, high intraocular pressure (IOP), corneal opacity, strabismus, amblyopia, diabetes mellitus, and irregular astigmatism.

All patients underwent the ophthalmic examinations that included uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), manifest refraction, anterior segment slit-lamp biomicroscopy, applanation tonometry, indirect ophthalmoscopy, corneal topography (Pentacam 70700: Oculus, Wetzlar, Germany), limbal pachymetry, and ultrasound biometry (IOL master).

Phacoemulsification with concomitant LRIs was performed in 48 eyes. Patients were evaluated in follow-up examinations at months 2 and 6 and their data were evaluated.

The patients will benefit from treating their astigmatism-better vision in a single surgical procedure, stabilizing their visual acuity (VA) and no need for any further intervention.

Surgeries

All surgeries were performed. SRK-T formula was used for all patients for IOL power calculation. Cataract surgery was performed under retrobulbar anesthesia. Acrylic foldable IOLs were implanted through a 2.8-mm temporal clear corneal incision without enlargement using the injector for all eyes. Before surgery, 6 and 12 o’clock position of the cornea were marked while the patient was sitting upright.

LRIs were made according to the modified Gills nomogram [5] ([Table 1]). At the beginning of the surgery, the steepest meridian is marked before phacoemulsification. We placed LRIs inside surgical limbus at a depth of 600 μm ([Figure 1]).
Table 1 Modified Gills nomogram indicating the degrees of arc incised with paired LRIs centered on the steep axis. The length is titrated by keratometric cylinder and patient age; the incision depth is set at 600 µm

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Figure 1 All limbal relaxing incisions were placed inside the surgical limbus at a depth of 600 µm before phacoemulsification with the limbal relaxing incision knife determined for 600 µm as shown in this figure.

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In case of patients whose corneas are with against-the-rule astigmatism (steep corneal meridian within 20° around 180° on corneal topography), the temporal hinge incision for phacoemulsification was oriented to align with placement of the LRI.

Before phacoemulsification, a second LRI was done nasally.

After IOL implantation and before removal of viscoelastic material, the original minimal LRI was extended according to the nomogram.

In case of patients whose corneas are with with-the-rule astigmatism, paired LRIs were placed on the steep meridian before phacoemulsification as dictated by modified Gill’s nomogram [5] ([Table 1]).

Measures

Comparison of pre- and postoperative topographic astigmatism is used to evaluate the effectiveness of LRI [6]. Analysis of the effectiveness was done using mean and standard deviation of the postoperative topographic astigmatism 2 and 6 months after surgery. The vector Zare and colleagues LRI during phacoemulsification analysis method was used to evaluate the efficacy of astigmatic correction (method of Kaye and Patterson) [7]. The safety of the LRI procedure was evaluated by recording of the intraoperative and postoperative complications and subjective symptoms (method of Kaye and Patterson) [7]. We evaluated the stability of the procedure by the variability of the mean topographic astigmatism at the end of the second- and sixth-month postoperative follow-up examinations ([Figure 2]). We performed paired t-test for statistical analysis and P less than or equal to 0.05 was considered statistically significant.
Figure 2 Preoperative and 6-month postoperative topography of a patient with preoperative corneal astigmatism and the difference map showing the effect of limbal relaxing incision.

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  Results Top


LRI was performed in 48 eyes (27 right eyes and 21 left eyes) of 48 patients. Mean age of patients was 64.7±7.9 years (range: 50–77).

Data analysis demonstrated a statistically significant reduction in the mean topographic astigmatism in the LRI eyes from 1.8±0.73 D (range: 1.50–3.50) preoperatively to 1.1±0.24 D (range: 0.5–1.7) and 1.4±0.52 D (range: 0.60–1.9) in the second and sixth postoperative months, respectively (P<0.001). There was no statistically significant difference between mean astigmatism at 2 and 6 months after LRI (P=0.91) ([Table 2]).
Table 2 Vector analysis of postoperative astigmatism for eyes that underwent combined phacoemulsification and limbal relaxing incision (2 and 6 months follow-up) (mean±SD)

Click here to view


UCVA was equal to 0.6 or more than 0.6 in 77% (36 cases) at month 2 after LRI, following 86% (41 cases) of patients at month 6 postoperatively. No patient lost any lines of UCVA or BCVA, which cannot be attributed solely to LRI efficacy as simultaneous cataract surgery was performed.

BCVA showed significant improvement at 2-month and 6-month follow-up evaluation. The average preoperative BCVA was 0.18±0.12 reaching 0.75±0.23 and 0.83±0.19, 2 and 6 months after LRI, respectively (P<0.001).

BCVA was greater than or equal to 0.6 in 78% of patients 6 months after LRI that might mostly be due to the cataract extraction and IOL implantation and not a consequence of the LRI surgery.

There was no intraoperative complication and rare postoperative subjective complaints (such as haloes, glare or fluctuating vision) in our patients.


  Discussion Top


The best visual outcomes of patients undergoing cataract surgery are related to IOL power-correct calculation and postoperative astigmatism suitable management [6],[7],[8],[9],[10]. In total, 17–21% of patients who performed cataract surgery suffer significant corneal astigmatism (1–3 D) [6].

After the usage of aspherical IOLs in cataract surgery, better IOL power calculation formula and lenticular astigmatism was minimized, and the biggest source of postoperative refractive astigmatism became the corneal astigmatism [11].

Postoperative astigmatism due to cataract surgery can be minimized by different techniques such as intraoperative relaxing incisions, toric IOL implantation or postoperative vision correction by ablative–refractive surgery by excimer laser with its own benefits and drawbacks.

Toric IOLs are very expensive. In addition, if any rotation happened to the IOL postoperatively, a significant astigmatism would occur.

Excimer laser vision correction after cataract surgery needs an additional operation with additional charges, possible complications, and limitations in patients with thin cornea [12],[13],[14],[15].

LRIs are used to correct preoperative astigmatism at the same time of cataract surgery.

In addition to lower costs, easy performance, and easy learning, however, the stability and range of correction are unpredicted [12],[13],[14].

Gills and Guyton [5] stated that LRIs are more effective in eyes that have low or moderate astigmatism more than high astigmatism.

LRIs give better VA than clear corneal incisions, as they cause less risk of glare and discomfort and they cause less distortion at the limbus [12],[15].

In this study, the range of astigmatism correction is evaluated using vector analysis of surgical-induced astigmatism (SIA) vector and target-induced astigmatism (TIA) vector. SIA vector is the amount and axis of astigmatic change that the surgery actually induced.

TIA vector is astigmatic change (by magnitude and axis) that the surgery was intended to induce. Correction index (CI) is calculated by dividing SIA by TIA. The CI is preferably equal to 1.0. In overcorrection, CI is more than 1, and less than 1, in the case of undercorrection. Difference vector (DV) is calculated by TIA–SIA. Index of success is calculated by dividing the DV by the TIA vector. The index of success is a relative measure of success and is preferably [16].

Considering the above-mentioned ratios, our study demonstrated that use of LRIs during phacoemulsification reduces corneal astigmatism by a ratio of 51%, however, there was a trend for undercorrection. Undercorrection was not uncommon in previous reports [17],[18],[19].

Budak et al. [20] studied 22 patients. They found a 44% reduction of astigmatism in eyes treated with LRI during phacoemulsification using the Gills nomogram, compared with our results of 51% reduction of astigmatism in a larger number of patients (48 patients).

In a study of Carvalho et al. [6], a statistically significant reduction in the mean topographic astigmatism was seen in the cataract LRI eyes from 1.93±0.58 D preoperatively to 1.02±0.60 D 6 months postoperatively (P<0.05).

Multiple factors might cause undercorrection of astigmatism in patients who are treated with phacoemulsification and LRIs, like the age of the patient, the accuracy of measuring the depth and length of the relaxing incision, and the surgeon factor [11],[12],[15].

We minimized the surgeon factor by performing all operations by only one surgeon. Another cause may be the improper position of the blade (oblique incision rather than perpendicular incision on the limbus, that may result in the wrong depth causing undercorrection) [21]. Undercorrection may be related to the area of limbal incision that is far from the corneal center [22]. However, more central clear corneal incisions may cause more glare and higher-order aberrations for the patients.


  Conclusion Top


In summary, simultaneous LRI during phacoemulsification surgery appears to be safe and fairly effective to correct mild-to-moderate amounts of corneal astigmatism between (i.e. 0.75 and 3.5 D).

A common disadvantage is undercorrection. Apart from the patient age, multiple factors, including ethnicity, sex, corneal limbal thickness, course of postoperative steroid regimen, and surgeon factors, should be considered for adjustment of future nomograms.

We recommend surgeons to apply nomograms that take patient age and size of LRI in millimeters to decrease preoperative corneal astigmatism. It seems that LRI incisions cannot fully correct but would cause more acceptable reduction in the preoperative corneal astigmatism.

Acknowledgments

A very special gratitude goes out to all down at Memorial Institute for Ophthalmic Research (MIOR) Dean Professor Dr Laila Elshazly, MIOR CRC President, Professor Dr Hany Nasr. Thanks to the whole MIOR staff for their support for helping and providing the suitable facilities for the work, with a special thanks to Al-Azhar Assiut Medical Journal for allowing us to publish our research in your dignified journal!

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Nichamin LD. Treating astigmatism at the time of cataract surgery. Curr Opin Ophthalmol 2003; 14:35–38.  Back to cited text no. 3
    
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Gills JP, Gayton JL. Reducing pre-existing astigmatism. In: Gills JP, Fenzle R, Martin RG, editors. Cataract Surgery: The State of the Art. Thorofare, NJ: Slack; 1998. 53–66.  Back to cited text no. 5
    
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Carvalho MJ, Suzuki SH, Freitas LL, Branco BC, Schor P, Lima AL. Limbal relaxing incisions to correct corneal astigmatism during phacoemolsification. J Refract Surg 2007; 23:499–504.  Back to cited text no. 6
    
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