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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 60  |  Issue : 3  |  Page : 246-249

A comparative study of central corneal thickness changes in bevel-up and bevel-down phacoemulsification


Department of Ophthalmology, MGM Medical College, Navi Mumbai, Maharashtra, India

Date of Submission23-Sep-2021
Date of Acceptance27-Jan-2022
Date of Web Publication26-Sep-2022

Correspondence Address:
Ayushi Choudhary
24, Mishra Vihar, Geetabhawan, Indore - 452001, Madhya Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/tjosr.tjosr_146_21

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  Abstract 


Introduction: Many techniques that have been developed but the risk for corneal endothelium damage and posterior capsule rupture still exist. It is believed that corneal endothelium is minimally damaged when the tip is bevel down in phacoemulsification surgeries. There is a difference between ophthalmologists with respect to the position of tip in phacoemulsification, and hence we conducted this study. Methodology: Thirty patients were evaluated in this study, both eyes of all the patients were operated using phacoemulsification; the right eye of all patients was operated with the bevel-up phaco tip and the left eye of all patients was operated using bevel-down phaco tip. The central corneal thickness (CCT) was taken and compared on preoperative day, immediate postoperatively, and on postoperative day 1, day 14, and 1 month in bevel-up and bevel-down phacoemulsification. Results: The mean CCT on day 14 in bevel-up phacoemulsification was 593.40 ± 18.11 and in bevel-down phacoemulsification was 585.37 ± 26.60, and on day 30 in bevel-up phacoemulsification was 573.53 ± 16.27 and bevel-down phacoemulsification was 561.80 ± 18.20. It can be observed that there was no significant difference in the CCT on day 0, day 1, and day 14; however, on day 30, there is a significant difference in the bevel up versus bevel down. Conclusion: In our study, it was observed that there was no significant difference in the CCT on day 0, day 1, and day 14; however, on day 30, there is a significant difference in the bevel up versus bevel down. Hence, it is observed that the corneal endothelial loss is less in bevel down when compared to bevel-up phacoemulsification.

Keywords: Cataract, central corneal thickness, phacoemulsification


How to cite this article:
Gore V, Choudhary A, Agrawal M, Shah A, Alex J. A comparative study of central corneal thickness changes in bevel-up and bevel-down phacoemulsification. TNOA J Ophthalmic Sci Res 2022;60:246-9

How to cite this URL:
Gore V, Choudhary A, Agrawal M, Shah A, Alex J. A comparative study of central corneal thickness changes in bevel-up and bevel-down phacoemulsification. TNOA J Ophthalmic Sci Res [serial online] 2022 [cited 2022 Dec 7];60:246-9. Available from: https://www.tnoajosr.com/text.asp?2022/60/3/246/357105




  Introduction Top


Cataract surgeries have become one of the safest, most frequent, and successful surgeries to be performed in patients. Since the introduction of phacoemulsification, various attempts have been made to decrease corneal endothelial damage as it is one of the major concerns. Corneal endothelial cell damage is influenced by various preoperative parameters such as age, small pupil diameter, and shorter axial length as well as intraoperative parameters including the size of the incision, phacoemulsification technique, and time.[1]

Several mechanisms have been proposed for the endothelial cell damage during phacoemulsification surgery, these include mechanical contact with nuclear fragments, direct trauma caused by instruments or lens fragments, irrigation flow, turbulence of fluid, and formation of the cavitation bubbles.[2]

There have been many techniques that have been developed but the risk for corneal endothelium damage and posterior capsule rupture still exists. Theoretically, keeping the lowest phaco energy decreases the amount of damage to endothelial cells. It is traditionally believed that the bevel end of the tip should be turned toward the nucleus (i.e., bevel down) directs the phaco energy posteriorly away from the endothelial cells as phacoemulsification should occur in the posterior chamber.

There is a difference between ophthalmologists with respect to the position of tip in phacoemulsification, and hence we conducted this study.

Objective

The objective of this study is to compare the central corneal thickness (CCT) in postoperative patients on day 1, day 14, and 1 month in bevel-up and bevel-down phacoemulsification.

Intervention

Thirty patients were evaluated in this study, both eyes of all the patients were operated using phacoemulsification; the right eye of all patients was operated with the bevel-up phaco tip and the left eye of all patients was operated using bevel-down phaco tip. Patients with senile immature cataracts were taken. The patients included in this study were above 50 years, cataract grading of 2–3 nuclear sclerosis, were willing to undergo pachymetry to measure CCT changes after phacoemulsification cataract surgery postoperatively and were able to follow study instructions. The patients unable or unwilling to follow study instructions and the patients with other pathologies affecting the corneal thickness (e.g., bullous keratopathy) were excluded from the study.


  Methodology Top


Data were collected after informed consent. Initial evaluation of the patient, including but not limited to vision, Intra-ocular pressure (IOP), anterior segment evaluation, and fundus examination were carried out. Preoperative CCT was recorded using pachymeter (Pachette 4). Postoperative CCT was taken on days 1, 14, and 30 to compare the corneal endothelial cell loss in bevel-up and bevel-down phacoemulsification.

Preoperative evaluation

All the patients underwent a complete preoperative ocular examination including uncorrected distance visual acuity (UDVA), best-corrected visual acuity (BCVA), slit-lamp evaluation of the anterior segment, applanation tonometry, and fundus evaluation with a noncontact 20 diopter lens with indirect ophthalmoscope or direct ophthalmoscopy. Preoperative CCT was measured using a pachymeter (Pachette 4) [Figure 1].
Figure 1: Pachymeter

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Surgical procedure

Both the eyes of the patients were operated with phacoemulsification, the right eye of all the patients was operated with the bevel-up phaco tip and the left eye was The preoperative evaluation, rest of the surgical procedure and the intraoperative and postoperative evaluations was the same in both the eyes.

Two stab incisions were made on the limbus. The anterior chamber was filled with hydroxypropyl methylcellulose 2% and a capsulorhexis 5.0–5.5 mm in diameter was created with a tip cystotome. A 2.8 mm incision was made on the cornea, which was followed by hydrodissection and hydrodelineation of the nucleus. Phacoemulsification of the nucleus was performed using the phaco chop technique with a 0° 20-gauge phaco tip. The nucleus was stabilized with the phacoemulsification tip either bevel up or bevel down, which was impaled with moderate vacuum and low ultrasonic power. The chopper was then advanced toward the phaco tip splitting the nucleus into two parts, following which several pieces of nucleus were broken by rotating the lens. The corneal material was aspirated or irrigated using a cannula. A foldable intraocular lens was then implanted in the capsular bag using a disposable injector cartridge system. The anterior chamber was irrigated, the incisions were secured by hydration of the corneal stroma and the eye was patched.

Postoperatively, all the patients were put on topical moxifloxacin and dexamethasone eye drops, one drop six times a day for 1 week, after which they were gradually tapered. All the patients were examined postoperatively on day 1, day 14, and at the end of 1 month. The examinations included UDVA, BCVA, slit-lamp examination, applanation tonometry, CCT measurement, and fundus examination.


  Results Top


A sample size of 30 patients was included in this study, where the right eye of each patient was operated with the bevel-up phaco tip and the left eye of each patient was operated with the bevel-down phaco tip [Graph 1].



There was no noteworthy difference in the age, sex, anterior segment examination, fundus examination and intraocular pressure of all the patients. The CCT was measured for all the patients preoperatively, immediate postoperatively, and on postoperative day 1, day 14, and day 30.

As shown in [Table 1], the mean CCT immediately postoperative in bevel-up phacoemulsification was 626.93 ± 20.03 and in bevel-down phacoemulsification was 622.83 ± 19.44, the mean CCT on day 14 in bevel-up phacoemulsification was 593.40 ± 18.11 and in bevel-down phacoemulsification was 585.37 ± 26.60 and on day 30 in bevel-up phacoemulsification was 573.53 ± 16.27 and bevel-down phacoemulsification was 561.80 ± 18.20. It can be observed that there was no significant difference in the CCT on day 0, day 1, and day 14; however, on day 30, there is a significant difference in the bevel up versus bevel down.
Table 1: Comparison of mean central corneal thickness between bevel up versus down (n=30 per group)

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  Discussion Top


Various attempts have been made to reduce the corneal endothelial cell loss in phacoemulsification surgeries. There are various factors preoperatively and postoperatively that affect the endothelial cell loss, but the position of the phaco tip is one of the most significant factors.

A letter submitted by Fine stated that phaco tip in bevel-down position has several advantages as the energy is not directed toward the corneal endothelium but instead it is directed toward the cataract.[3]

Faramarzi et al. conducted a study comparing corneal endothelial cell loss in bevel-up versus bevel-down phacoemulsification and stated that with phaco tip in bevel down position, the percentage of endothelial cell loss was nearly twice of what it was in bevel-up position, due to the emulsification of the nucleus around the endothelial cells when the phaco tip is bevel down. It also stated that the posterior capsule maybe damaged as the phaco tip is near to the posterior surface of the cornea in bevel-down phacoemulsification.[4]

However, in the study conducted by us the CCT is much closer to the preoperative measurement in bevel-down tip position when compared to bevel-up tip position on postoperative day 30 as seen in [Graph 2].



In the bevel-down phacoemulsification, it is observed that all the phaco energy is directed toward the cataract. As the energy is directed away from the corneal endothelium or trabecular meshwork, the corneal endothelial cell loss is less in bevel-down phacoemulsification. In bevel-up phacoemulsification, the phaco energy is directed toward the corneal endothelium instead of the cataract itself causing comparatively more endothelial cell loss. It is easier to aspirate the epinucleus in bevel-down phacoemulsification as the energy is already directed toward the cataract.

It is also observed that a vacuum can be easily achieved in bevel-down tip position with very little ultrasound energy, whereas in bevel-up tip position, high ultrasound energy is required. In bevel-up phacoemulsification, more ultrasound energy is required to get the bevel-up tip into the endonucleus to achieve a vacuum. In conclusion, the benefits of bevel-down phaco tip are more when compared to bevel-up phaco tip.


  Conclusion Top


In our study, it was observed that there was no significant difference in the CCT on day 0, day 1, and day 14; however, on day 30, there is a significant difference in the bevel up versus bevel down. Hence, it is observed that the corneal endothelial loss is less in bevel down when compared to bevel-up phacoemulsification.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Raskin E, Paula JS, Cruz AA, Coelho RP. Effect of bevel position on the corneal endothelium after phacoemulsification. Arq Bras Oftalmol 2010;73:508-10.  Back to cited text no. 1
    
2.
Linebarger EJ, Hardten DR, Shah GK, Lindstrom RL. Phacoemulsification and modern cataract surgery. Surv Ophthalmol 1999;44:123-47.  Back to cited text no. 2
    
3.
Fine IH. Advantages of bevel-down technique. J Cataract Refract Surg 2012;38:925-6.  Back to cited text no. 3
    
4.
Faramarzi A, Javadi MA, Karimian F, Jafarinasab MR, Baradaran-Rafii A, Jafari F, et al. Corneal endothelial cell loss during phacoemulsification: Bevel-up versus bevel-down phaco tip. J Cataract Refract Surg 2011;37:1971-6.  Back to cited text no. 4
    


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