Pars Plana Vitrectomy
History[edit | edit source]
Pars plana vitrectomy (PPV) is a surgical procedure that involves removal of vitreous gel from the eye. The procedure derives it name from the fact that vitreous is removed (i.e. vitreous + ectomy = removal of vitreous) and the instruments are introduced into the eye through the pars plana. PPV was first introduced in 1972, when Machemer invented a single port, multifunctional 17-gauge cutter called the vitreous infusion suction cutter (VISC)1. PPV was a major advance because for the first time it allowed for the removal of vitreous through a closed system, rather than through an open sky technique. In 1975, O’Malley and Heintz described the use of a 20-gauge 3 port system2. 20-gauge 3 port PPV became the gold standard and remained so for at least 3 decades. Over the past several years, the development of small incision transconjunctival, sutureless PPV has led to a major shift in how many diseases are treated in the operating room. In 2002 Fujii et al introduced the modern 25-gauge PPV system3, while Eckhart endorsed 23-gauge PPV in 20034.
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- Vitrectomy machine (in the U.S. options include Accurus, Constellation, Millenium or Stellaris systems)
- Infusion line
- Light source
Additional task specific instruments include:
- Tano scraper
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Traditional 20-gauge PPV requires a conjunctival peritomy prior to placing the sclerotomies. An infusion line is sewn in place, typically in the inferotemporal quadrant and then two superior sclerotomies are placed near the 10 and 2 o’clock positions using a myringovitreoretinal (MVR) blade. Frequently, the vitreoretinal surgeon will hold a light pipe in one hand and a vitrector in the other. Alternative sources of illumination, e.g. chandelier lights or illuminated picks, allow for bimanual surgery. Bimanual surgery may be advantageous when performed particularly complex tasks. For example, during a complex tractional retinal detachment repair, the surgeon may use a forceps in one hand and an illuminated pick in the other to facilitate delamination of membranes.
Advantages of small incision over 20g[edit | edit source]
The advantages of a transconjunctival sutureless approach include increased patient comfort5,6, decreased corneal astigmatism7,8, and decreased operative times5,6. In addition, there is less conjunctival scarring, which may benefit patients who have had multiple previous surgeries or where preserving the conjunctiva is paramount (as in glaucoma patients who may need or have had filtering surgery).
Disadvantages of small incision over 20g[edit | edit source]
There are also some drawbacks to performing 25 and 23-gauge vitrectomy. To date instrumentation is still limited compared to 20-gauge vitrectomy. In cases, where fragmentation, MPC scissors, or bimanual surgery is preferred, 20-gauge may offer certain advantages. Patients who undergo transconjunctival sutureless vitrectomy are more likely to experience post-operative hypotony9. The likelihood of post-operative hypotony is lower in gas or air filled eyes than fluid filled eyes10.
Possibly as a result of hypotony or wound leakage, it has been observed that endophthalmitis is more likely after 25-gauge vitrectomy than after 20-gauge vitrectomy. Kunimoto et al found that endophthalmitis occurs 12 times more frequently after 25-gauge vitrectomy than after 20-gauge vitrectomy11. Similarly, Scott et al found that endophthalmitis occurred every 1 in 119 cases with 25-gauge PPV, while it occurred every 1 in 3188 cases with 20 gauge PPV12. This translates to a 28-fold increased risk of endophthalmitis with 25-gauge surgery compared to 20-gauge PPV. On the other hand, Mason et al, in a retrospective, consecutive series found similar rates of endophthalmitis between 25-gauge (rate = 0.053%) and 20-gauge (rate = 0.076%)13.
Surgical Indications[edit | edit source]
Pars plana vitrectomy is commonly recommended for the following conditions.
- Macular hole
- Macular pucker
- Vitreomacular traction
- Refractory macular edema
- Vitreous hemorrhage
- Tractional retinal detachment
- Rhegmatogenous retinal detachment
- Dislocated intraocular lens
- Refractory uveitis
- Retained lens material
- Intraocular foreign bodies
- Aqueous misdirection syndrome
Complications[edit | edit source]
- Cataract, the most common complication
- Retinal tear
- Retinal detachment
- Suprachoroidal hemorrhage
- Vitreous hemorrhage
- Optic neuropathy
- Raised intraocular pressure, usually from gas or oil tamponade
Surgical follow up
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Follow up should be arranged on a case by case basis and is dependant on the complexity and severity of the underlying disease being treated and the likelihood of complications. A typical follow up regimen may include visits on post-operative day 1, week 1, week 3, week 6, month 3. Follow up should be more frequent if complications occur.
References[edit | edit source]
1. Machemer R, Parel JM, Norton EW. Vitrectomy: a pars plana approach. Technical improvements and further results. Trans Am Acad Ophthalmol Otolaryngol 1972;76:462–466.
2. O’Malley C, Heintz RM Sr. Vitrectomy with an alternative instrument system. Ann Ophthalmol 1975;7:585–588, 591–594.
3. Fujii, G.Y., et al., A new 25-gauge instrument system for transconjunctival sutureless vitrectomy surgery. Ophthalmology, 2002. 109(10): p. 1807-12; discussion 1813.
4. Eckardt, C., Transconjunctival sutureless 23-gauge vitrectomy. Retina, 2005. 25(2): p. 208-11.
5. Misra A, Ho-Yen G, Burton RL. 23-gauge sutureless vitrectomy and 20-gauge vitrectomy: a case series comparison. Eye. 2008 Jun 6
6. Yanyali A, Celik E, Horozoglu F, et al. 25-Gauge transconjunctival sutureless pars plana vitrectomy. Eur J Ophthalmol. 2006 Jan-Feb;16(1):141-7.
7. Yanyali A, Celik E, Horozoglu F, et al. Corneal topographic changes after transconjunctival (25-gauge) sutureless vitrectomy. Am J Ophthalmol. 2005 Nov;140(5):939-41
8. Okamoto F, Okamoto C, Sakata N, Hiratsuka K et al. Changes in corneal topography after 25-gauge transconjunctival sutureless vitrectomy versus after 20-gauge standard vitrectomy. Ophthalmology. 2007 Dec;114(12):2138-41.
9. Gupta OP, Ho AC, Kaiser PK, et al. Short-term outcomes of 23-gauge pars plana vitrectomy. Am J Ophthalmol. 2008 Aug;146(2):193-197.
10. Gupta OP, Weichel ED, Regillo CD, et al. Postoperative complications associated with 25-gauge pars plana vitrectomy. Ophthalmic Surg Lasers Imaging. 2007 Jul-Aug;38(4):270-5.
11. Kunimoto DY. Kaiser RS. Wills Eye Retina Service. Incidence of endophthalmitis after 20- and 25-gauge vitrectomy. Ophthalmology. 114(12):2133-7, 2007 Dec.
12. Scott IU, Flynn HW Jr, Dev S, et al. Endophthalmitis after 25-gauge and 20-gauge pars plana vitrectomy: incidence and outcomes. Retina. 2008 Jan;28(1):138-42
13. Mason JO III, Yunker JJ; Vail RS et al. Incidence of Endophthalmitis Following 20-Gauge and 25-Gauge Vitrectomy. Retina. 28(9):1352-1354, October 2008.