|Year : 2020 | Volume
| Issue : 2 | Page : 166-170
Comparison of the scleral tunnel constructed with crescent versus razor blade using the anterior segment optical coherence tomography
Sowmya Raveendra Murthy, Priyanka Sudhakar
Department of Pediatric Ophthalmology and Strabismus, Sankara Eye Hospital, Bengaluru, Karnataka, India
|Date of Submission||15-Jan-2020|
|Date of Acceptance||15-Feb-2020|
|Date of Web Publication||25-Aug-2020|
Dr. Sowmya Raveendra Murthy
Department of Pediatric Ophthalmology and Strabismus, Sankara Eye Hospital, Bengaluru, Karnataka
Source of Support: None, Conflict of Interest: None
Aim: The aim of this study is to compare and contrast the efficacy of a razor blade against crescent, in constructing a scleral tunnel in temporal small-incision cataract surgery (SICS) in a community setup. The following parameters were considered for the comparative analysis: a) Structural anatomical dimensions using the anterior segment optical coherence tomography (ASOCT), b)Tunnel integrity based on the need for suturing or subsequent resuturing and c) Section outcome in terms of any associated tunnel complications. Methods: A prospective, comparative study of 100 consecutive cases of temporal SICS was done. The cases were randomly divided to undergo the surgery with tunnel construction either with a crescent knife or a razor blade (50 eyes each), by a singleoperating surgeon (Dr SR). The structural dimensions and integrity of the tunnel were noted using an AS-OCT on the 1st postoperative day. Tunnel-related complications were noted both intra and postoperatively. Results: Of the 100 eyes operated, the mean average depth at section, with crescent was found to be 526 μ, while that with blade was 598 μ. The mean average depth at internal entry was found to be 607 μ with crescent and that with blade was 670 μ. Self-sealing wound was achieved in 49 of the 50 cases with crescent as well as with blade, with only 1 tunnel requiring 1 suture for anterior chamber (AC) formation in case of both crescent and blade. Tunnel complications included Descemet's membrane detachment in 1 eye and premature entry in 1 eye, in razor blade constructed tunnel. The time taken with crescent was on a mean average 32.9 s, while that with blade was 27.3 s. Conclusion: Razor blade constructed scleral tunnels are slightly deeper compared to crescent as noted on AS-OCT. Integrity and complication rates being comparable between the two. The razor blade could be considered as a safe, equally efficacious, if not better, and an economical alternate to crescent knife in a high-volume community setup.
Keywords: Anterior segment optical coherence tomography, cost-effective surgery, crescent, razor blade, small-incision cataract surgery, temporal small-incision cataract surgery
|How to cite this article:|
Murthy SR, Sudhakar P. Comparison of the scleral tunnel constructed with crescent versus razor blade using the anterior segment optical coherence tomography. Kerala J Ophthalmol 2020;32:166-70
|How to cite this URL:|
Murthy SR, Sudhakar P. Comparison of the scleral tunnel constructed with crescent versus razor blade using the anterior segment optical coherence tomography. Kerala J Ophthalmol [serial online] 2020 [cited 2021 Apr 22];32:166-70. Available from: http://www.kjophthal.com/text.asp?2020/32/2/166/293296
| Introduction|| |
In developing nations such as India, despite the boom of cataract surgery as a refractive surgery, the predominant population in the rural community at large seek a more cost-effective solution. Hence, the prospects of alternative techniques would yield outcomes similar to phacoemulsification but at lower costs, such as the manual small-incision cataract surgery, still thrive to achieve the same benefits as phacoemulsification.,,,,,
Eons ago, when Von Graefe brought into vogue, his customized knife, he had suggested a dictum, “As the section goes, so goes the operation.” Despite the advancements in techniques of cataract extraction, this dictum largely holds true even today. Tunnel construction forms a particularly integral part of small-incision cataract surgery (SICS). Since the advent of this technique, several types of cataract knives have evolved to facilitate this vital step of surgery. Right from ultrasharp diamond knives introduced by Durham and Luntz (I968), to the von Graefe knife, keratome, corneal scissors, disposable cataract knives, keratomes, and the Bard-Parker blades have been widely used for this purpose. Over the years, however, the crescent knife has come to be used popularly as part of the conventional SICS. The use of razor blade has been described in the past, especially as a feasible instrument readily available worldwide. However, there have been no head-on studies comparing these instruments in making of a corneoscleral tunnel.
In this study, we compare the efficacy of a razor blade against the conventional crescent knife and compare and contrast the tunnel formed using anterior segment optical coherence tomography (ASOCT). Also to note the complications related to tunnel so formed.
| Methods|| |
Our study is a prospective comparison study of 100 consecutive cataract surgeries done by a single-operating surgeon. The hospital ethical committee clearance was obtained. The study population included patients aged 35–80 years, who were screened for cataract surgery between February 2018 and August 2018 at the community outreach section of our hospital. Uncooperative patients or those unable to position themselves for the imaging were excluded from the study.
Of the 100 cases, 50 would be randomly assigned to each of these two groups. All patients underwent SICS with the temporal section as part of the hospital protocol in the community setup.
Half of them had a scleral tunnel constructed with a razor blade, and the rest half with a crescent blade. During the surgery, the sterilized razor blade would be broken from one of the corners into 1 small fragment with a blade breaker, as illustrated in [Figure 1].
|Figure 1: Step-wise depiction of scleral tunnel construction with the razor blade|
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Similarly, three more fragments can be broken off the blade for three more cases, from the other three corners of the blade. At the same time, time taken to construct the tunnel was also recorded. Intraoperative complications, if any, associated with the tunnel, such as premature entry/button-hole/sectional Descemet's membrane detachment (DMD), was noted for every case.
On the 1st postoperative day, an AS-OCT of the corneoscleral section was done to assess the following:
- Depth at the external lip
- Depth at internal entry
- Tunnel integrity.
Economical consideration in terms of cost per instrument was also included in the analysis.
| Results|| |
Of the 100 eyes operated, self-sealing wound was achieved in 49 of the 50 cases with both crescent and razor blade. Premature entry, which required tunnel suturing for AC formation, occurred in case of only one tunnel in each of the two groups. DMD was observed in one case in the razor blade group.
On AS-OCT imaging done the following day, we observed that the mean average depth at section (external lip), with crescent, was 526 μ, while that with the razor blade was 592.8 μ. The mean average depth at entry (internal lip) was 612 μ with crescent and 674 μ with the razor blade. [Figure 2] and [Figure 3] show the images as taken by ASOCT on the 1st postoperative day.
|Figure 2: Anterior segment optical coherence tomography image of tunnel constructed with the razor blade, and a digital caliper (in green) depicting the measured depths at the external and internal incisions|
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|Figure 3: Anterior segment optical coherence tomography image of tunnel constructed with crescent knife, and a digital caliper (in green) depicting the measured depth at the external and internal incisions|
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On a comparative analysis of the depth measurements of the tunnel with the two instruments, that obtained with the razor blade was 62–66 μ deeper, as shown in [Figure 4].
|Figure 4: A graphical comparison of depths of incision made with a crescent versus that with a blade at the external lip, (above graph) where the latter is 66 μ deeper than the former and at the inner lip, where the latter is 62 μ deeper(below graph)|
Click here to view
In addition to the above-measured parameters, we also noted that the time taken to construct the tunnel with crescent knife was on an average 32.9 s, while that with blade was on an average 27.3 s. In terms of cost per instrument, one razor blade, which can be used at least for four cases following sterilization, costs Rs. 3, while a crescent, which could be sterilized and used for up to three times, costs Rs. 56.
| Discussion|| |
In hospitals, which cater to a large rural community, employing cost-effective, expeditious strategies with the preservation of good quality into surgical methods is essential to accomplish set goals. High-quality and high-volume surgery is the principle which an experienced surgeon abides by to perform a dozen or more surgeries at a stretch, with the purpose of clearing the pile-up of cases at such center. With these salient features in mind, manual SICS has been proven to be a feasible option.,,,,,, The temporal manual SICS yields good visual outcomes, especially in elderly, due to the negation of preexisting astigmatism in this age group of patients., Achieving a self-sealed, astigmatically neutral wound, is pivotal to a good refractive outcome.
In our study, we perform temporal manual SICS on all patients. Self-sealing wound was achieved in most of the cases (49 of 50) in each of the two groups. Tunnel suturing was warranted in 1 case in each of the two groups, in view of premature entry/poor wound construction. This was similar to a large scale study by Zawar andGogate where tunnel suturing for the same purpose was required in 1.8% of cases, and by a study by Patil et al., where premature entry contributed to 1.2% of the intraoperative complications.
Optimal incision depth is usually one-half to two-thirds the scleral thickness or about 0.3 mm.,, Our results also showed the depth of tunnel in par with optimal recommendations, though depth of the inner lip was slightly higher, which could probably be attributable to 1st postoperative day corneal edema. The only difference between the two groups seemed to be that the tunnels constructed with the razor blade were around 60 μ deeper. Furthermore, DMD was seen in 1 of the 50 cases with razor blade alone. This result is, however, comparable with the probability of the same complication occurring with crescent. DMD as a complication has been noted to be around 1.2%–3% in small-incision cataract surgeries.,
We also noted that it took shorter time to construct the tunnel with blade as compared to crescent (5.6 s lesser). Same razor blade was used to perform the entry and extension of tunnel thus abatting the cost and need for the second instrument (keratome).
Finally, in terms of cost efficiency, razor blade, which costs only Rs. 3 as compared to crescent knife, which costs Rs. 56, is available universally and can be bought in any number in contrast to the crescent which is supplier based and has to be bought in packaged numbers, adding to the cost. This fact has been emphasized in a study by Zawar andGogate.
The study results are to be considered in light of few limitations. The measurements taken were manual and with an inbuilt digital caliper. An experienced surgeon operated all the cases, so complications rate were low and one cannot extrapolate the same to a novice.
| Conclusion|| |
Razor blade constructed scleral tunnels are slightly deeper compared to crescent as noted on AS-OCT. Integrity and complication rates being comparable between the two. The razor blade could be considered a safe, equally efficacious, if not better, and an economical alternate to crescent knife in a high-volume community setup.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4]