Correspondence:
To cite this article:
Natarajan S. Agarwal A. 25G Suturless Viterectomy. Day Surg J India,
2006; 2:23-27
Paper received: February 2006. Accepted: March 2006 Source of support: Nil.
Since the advent of couching by Sushrata, ophthalmic surgical techniques undergoing rapid developments and modifications. The aim is to adopt the technique with best possible outcome by least possible invasion of ocular anatomy. With the rise in sutureless cataract surgeries with minimal patient morbidity post operatively, vitreoretinal procedures also underwent lots of changes. A sutureless surgery means that the hospital stay is reduced to negligible & the patient is sent home the same day with minimal redness of the eye and discomfort. It also means that the patient is able to resume work as soon as possible.
Though the more sophisticated instruments and lasers developed for the vitreoretinal surgery but the patients need to undergo 20 gauge sclerotomies and post operative morbidity because of sutured wounds. Tunnel based sclerotomy by Chen
4 was suggested to create self sealing incisions for VR surgery but it requires a conjunctival peritomy and suturing and is associated with complications like wound leakage, extention, dehiscence, hemorrhage, vitreous and / or retinal incarceration, retinal tears, dialysis and difficulty in passing instruments. Modifications in vitrectomy instrumentation aimed at decreasing the size of instruments must achieve a balance between ability to achieve smaller incision sizes versus maximizing instrument functionality, recognizing that high instrument functionality may not always be compatible with small size.At first, there were no suitable materials to use as sutures in the eye, so the eye had to be bandaged and heal on its own.
This meant the patient was confined to bed with their head literally sandbagged to prevent movement that might jeopardize the healing process
. Overall the quest for least morbidity for patient postoperatively undergoes full circle from No suture Era in cataract surgery to again sutureless vitreoretinal surgery. In the early 1970s, Machemer1 used a 17-gauge 1.5mm diameter multifunctional instrument capable of cutting and aspirating the vitreous followed by a smaller vitreous cutter of 20 gauge (0.9 mm) designed by O’Malley and Heintz2 in 1974. The race for smaller instruments doesn’t end here. In 1990 De Juan and Hickingbotham3 designed a variety of 25–guage (0.5mm diameter) vitreoretinal instruments and thus the era of sutureless vitrectomy begins.Transconjunctival sutureless vitrectomy system (TSV) 25 guage developed by Fujii et al5 allows self-sealing transconjunctival sclerotomies and minimizes surgically induced trauma, improves operative efficiency and hastens postoperative recovery. The self-sealing sclerotomy obviates the need for conjunctival peritomy and no sutures are required at any conjunctival or scleral opening site. The development of smaller gauge instruments may prevent the incorporation of multiple functions in their design. Also due to the smaller size, the infusion and aspiration rates are reduced. However, there are settings where the full capabilities of 19-20 gauge instruments may not be required and smaller gauge instruments may be more desired due to their less in invasive nature.
Instrumentation:
The TSV consists of a 25-guage microcannula system and a wide array of vitreoretinal instruments specifically designed for this operating system. Integral to this vitrectomy instrument system is the 25-gauge microcannula system. It consists of a microcannula, an insertion trocar, an infusion cannula, a plug forceps, and a cannula plug. The cannula remains in place and newly designed smaller instruments can be introduced through it to perform surgery in the posterior segment.
The microcannula consists of a thin- walled polyamide tube 3.6 mm in length with an inner / outer diameter of 0.57/0.62 mm. A collar is present at the extraocular portion, which can be grasped with forceps to manipulate the microcannula. A funnel – shaped entry was designed to facilitate access of instruments. Once inserted through the eye wall, sutures are not required to hold the microcannula in place. The microcannulas are inserted through the conjunctiva into the eye by means of a trocar that, when inserted into the cannula, forms a continuous bevel with the microcannula, allowing ease of entry. The trocar is then withdrawn leaving the cannula in place. The main purpose of the 25–gauge microcannula system is to maintain the alignment between the conjunctival and the scleral entry site, because no prior conjunctival dissection is required for insertion of the trocar and cannula. Therefore, the 25–gauge cannula system is referred to as an "entry site alignment system" (EAS). (Fig.1)
The 25–gauge infusion cannula consists of a small metallic tube 5mm long with an inner/outer diameter of 0.37/0.56 mm. The intraocular portion of the infusion cannula is directly inserted into the eye through the microcannula. A collar at the extra ocular portion allows the infusion cannula to be held and facilitates it manipulation.
A wide array of vitreoretinal microsurgical instruments (Fig.2) complying with the 25-gauge standards has also been designed. These include a high-speed vitreous cutter, illumination probe, intraocular micro forceps, rigid retinal pick, flexible and extended retinal pick, tissue manipulator, laser probe, diathermy probe, aspirator and others.
Infusion and Aspiration rates:
Due to the small size the infusion and aspiration rates at various settings are reduced by 6.9 and 6.6 times respectively when compared with the 20 guage system6.
Time Measurement comparison:
In a published study done by Fujii GY et al6, the mean total operative time was found to be significantly greater for the 20 guage (26 min 7sec) than for the 25 gauge vitrectomy (17 min 17sec). The differences in operating times were noticeably greater for the ‘initial opening’ and ‘final closing’ steps of the surgery. The ‘vitrectomy’ time was an average of 1 min 23 sec longer using the 25 gauge TSV.
Techniques:
Stretching the conjunctiva at the beginning of the procedure with cotton tipped applicator before entering the pars plana ensures that at the end, when the trocar is removed, the conjunctiva will help cover the hole made by trocar. Three entries using trocar cannulas are made in the inferotemporal, superotemporal and supreonasal quadrants. The trocar creates 0.5mm conjunctival and scleral incisions. An infusion cannula is inserted into the IT cannula and plugs used to temporarily close other entry sites till use (Fig3, Fig4)
The other cannula is kept plugged (Blue) till the introduction of endo illuminator.
The TSV requires some modifications of technique during vitrectomy. Maximum cut rates are required to achieve optimal fragmentation of intraocular tissue and to decrease the possibility of obstruction in aspiration line, which is narrower than standard 20-guage vitrectomy systems. The vitreous cutter is used with maximum aspiration rate (500mmHg) and concomitant high cutting rate of 1500cpm. The difference between minimum infusion rate and maximum aspiration rate is larger in the TSV system, which allows for greater safety margin against hypotony during aspiration. The 25-gauge cannula should not be used concurrently with standard 20 guage vitreous cutter as it may result in hypotony during aspiration resulting form functional discrepancy between infusion and aspiration rates of both systems. The TSV system can provide a better gas fill as it is a more closed system. The 25 g. cutter can be used to sweep blood off the retina.
After removal of the trocar pressure is applied to each site to ensure that they are not leaking. The conjunctiva should snap back, of the conjunctiva begins to swell and form a bleb, there may be a leak. Some surgeons prefer to take a fixation forceps and manually close the wound and hold it for a moment until the underlying vitreous can block the wound site form beneath the sclera.
Indication:
Many vitreoretinal procedures that do not involve extensive dissection, are likely to benefit from a less invasive procedure, because much of the surgical trauma in those cases may be related to the conjunctival and scleral incision procedures. The TSV system has been used in epiretinal membrane peeling, macular hole surgery, retinal detachment with minimal or no proliferative vitreoretinopathy, branch retinal vein occlusion sheathotomy, vitreous hemorrhage, endophthalmitis. The TSV is of potential benefit in smaller eyes of children where use of standard instruments may incur technical difficulties related to the ocular size6.
With the rise in health awareness, more and more patients presented early with less complications. Such cases can be better dealt with TSV 25 System. Newer surgical indications like vitrectomy for diabetic macular edema makes the scope of this system further more. Glaucoma prone patients undergoing vitreoretinal procedures may have a better mobile and healthy conjunctiva for the future antiglaucoma surgery. Meanwhile, combined sutureless cataract and vitreoretinal surgery by TSV 25 G System makes the major ophthalmic surgery a day care procedure with least possible morbidity for the patients, the ultimate goal for any surgeon.
Limitations:
The TSV system should not be use on previously scarred operated eyes as it is difficult to enter the sclera and the trocar may bend. In highly myopic patients with thin sclera, wound does not close in the same manner as other patients. It is difficult to infuse silicone oil through 25-gauge cannula. In retinal detachments with proliferative vitreoretinopathy, because of smaller port and diameter of 25-gauge cutter, the cutting and aspiration rates are reduced so its efficiency in dense fibrous proliferation may be limited. The increase flexibility of 25 gauge instruments may not be able to control eye positions during the surgery. There is also a theoretical possibility of suture less sclerotomies serving as a conduit for the entry of bacteria.
Surgeons may experience wound leaks that need to be sutured in their initial cases. A re-operation the next day is worse than suturing at the time of closure.
Results:
Being a relatively new technique few studies are available in literature. Fujii et al described6 their initial experiences in a consecutive series of 35 eyes. They used the TSV in cases of retinal detachment, retinopathy of prematurity, Norrie disease, epiretinal membrane, macular hole, branch retinal vein occlusion, persistent diabetic macular edema and vitreous hemorrhage and retained lens material post cataract surgery.
No wound leakage was seen in any case and the postoperative IOP was maintained. In idiopathic epiretinal membrane cases, core vitrectomy and membrane peeling was performed satisfactorily. Sheathotomy at the pathologic arterio-venous crossing was performed by using a nitinol pick that can be extended to adjust its curvature, which enables the surgeon to get optimal positioning at the dissection point of the crossing. It was possible to peel epiretinal membranes and perform sheathotomy without prior vitrectomy in some cases. Treatment of retinal detachment was successful is all cases, although none of these cases had severe proliferative vitreoretinopathy.
In our initial experience TSV was found to be suitable in cases with epiretinal membranes, macular hole and fresh vitreous haemorrhage. The TSV system was used in 4 cases requiring Vitreoretinal procedures. The four cases were Epiretinal Membrane in a post laser diabetic patient, Idiopathic Macular Hole, Retinal Detachment and Vitreous Hemorrhage. We evaluated the operative time, wound closure, limitations of the system and the outcome of surgery. The average operating time was 30 mins and all the wounds showed good closure with no wound leaks. The epiretinal membrane was successfully removed with an increase of three lines in visual acuity. The macular hole showed flat edges with an open hole. The retinal detachment underwent resurgery for recurrence. The vitreous hemorrhage was old and repeatedly clogged the cutter. Probably the further improvement in technology will makes us able to handle complicated cases in the near future.
Conclusion:
In select cases where full capabilities of conventional vitrectomy system are not required,the 25-gauge TSV system can offer better patient comfort, care and management by reducing operative time effectively. With more advancement in technology, future of sutureless 25 G vitrectomy and thus the vitreoretinal surgery going for a major turning point.
References:
1. Machemer R, Buettner H, Norton EW, PArel JM. Vitrectomy a pars plana
approach. Trans Am Acad Ophthalmol Otolaryn gol 1971; 75:813 20.
2. O’Malley C, Heintz RM Sr. Vitrectomy with an alternative instruments
system, Ann Ophthalmol 1975; 7: 585-8; 591-4.
3. De Juan E Jr, Hickingbotham D. Refinements in microinstruementation for
vitreous surgery. Am J Ophthalmol 1990; 109: 218-20.
4. Chen JC, Sutureless pars plana vitrectomy through self-sealing
sclerotomies. Arch Ophthalmol 1996;114:1273-5
5. A new 25- guage instrument system for transconjunctival sutureless
vitrectomy surgery: Fujii GY, De Juan E Jr, Humayun Ms, Pieramici DJ, Chang TS,
Ng E, Barnes A, Wu SL, Sommerville DN. Ophthalmology 2002 Oct;109 (10): 1807 12;
discussion 1813.
6. Initial experience using the transconjunctival sutureless vitrectomy
system for vitreoretinal surgery: Fujii GY, De Juan E Jr, Humayun MS, Chang TS,
Pieramici DJ Barnes A, Kent D. Ophthalmology 2002 Oct; 109(10): 181420.
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