Ординатура / Офтальмология / Английские материалы / Glaucoma Surgery_Trope_2005

2.PRE-OPERATIVE EVALUATION

Once the decision to proceed with glaucoma surgery has been made, several factors should be considered during surgical planning.

2.1.Patient Age

Younger patients tend to have a more vigorous healing response making them more susceptible to failure. This may indicate the use of antifibrotic agents, although they should be used with caution in young myopes due to the risk of hypotonous maculopathy. By the virtue of their longer life expectancy, younger patients are more likely to have surgical failure within their lifetimes, requiring repeat surgery. We therefore advise initial surgery in one upper quadrant leaving the other quadrant for repeat surgery at a later date. It is important to remember that surgery in younger patients may result in an increased risk of blebitis and endophthalmitis due to their longer life expectancy.

Older patients may have a decreased healing response and may be more susceptible to complications in the short-term. In addition, elderly patients may have difficulty with postoperative care without assistance from caregivers.

2.2.External Disease

Evidence of ocular surface disease, including dry eye, conjunctival scarring, symblepharon, and previous ocular surgery, should be noted. These conditions make the surgical procedure more difficult, and also increase the risk of postoperative scarring, and complications. Lack of suitable conjunctiva may require an alteration in both the type and the site of surgery planned (e.g., from a trabeculectomy to a seton).

The lids should always be examined for epiphora, entropion, or distachiasis. These should be dealt with prior to glaucoma surgery. Temporary measures, such as Quickert sutures for entropion or epilation for distachiasis, may be sufficient. Chronic infections, such as staphylococcal blepharitis or purulent discharge from the lacrimal sac, must be addressed prior to glaucoma surgery.

2.3.General Health Status

Although most glaucoma surgery is performed with local anesthetic, including topical anesthetic, general health status should be known. In particular, patients with cardiovascular disease, systemic hypertension and diabetes are at increased risk of suprachoroidal hemorrhage. Surgery should be performed with caution in such cases. Patients with liver dysfunction or patients on anticoagulation therapy will have increased intraoperative bleeding. Such patients should be advised of the increased risk and be assessed by the relevant specialists before recommending discontinuation of anticoagulation therapy. Most glaucoma surgery can be successfully performed with patients on anticoagulation therapy but informed consent is important in such cases.

3.SURGICAL OUTCOMES

Success rates for incisional glaucoma surgery depend on patient factors as discussed earlier, but are also affected by surgical techniques. The use of antimetabolites has significantly improved both the success rate and the survival rate of trabeculectomies. Two types

Figure 1.1 Success rates with and without 5 FU (27). [Reprinted from Ref. (27), with permission from Elsevier.]

of antimetabolites are commonly used in glaucoma surgery. 5-Fluorouracil (5-FU) inhibits DNA replication but is reversible and may be used intraoperatively, as well as multiple times postoperatively. Mitomycin-C permanently binds DNA, and can only be used once with maximal effect after 5 min.

The Fluorouracil Filtering Surgery Study examined the success rates of trabeculectomies with and without the use of postoperative 5-FU. Success was defined as IOP ,21 mmHg with or without medications and no need for re-operation to control IOP. The 5 years success rate of trabeculectomies was 49% with 5-FU use, but only 26% without antimetabolite use (Fig. 1.1) (27). One of the major causes of failure in both groups was early postoperative wound leak (within 2 weeks of surgery). At 5 years, the success rate for the 5-FU group was 54% in eyes without a leak and 28% in those with a leak. The 5 year success rate in the group without antimetabolites was 24% without a wound leak and 15% with a leak (28). Risk factors for wound leaks include the use of antimetabolites, one-layer (vs. two-layer) conjunctiva-Tenon capsule closure, inferiorly located trabeculectomy, and older patients.

More recent studies have demonstrated similar efficacy with intraoperative mitomycin-C without the need for postoperative injections of antimetabolites (29). With the use of any antimetabolite, caution must be exercised as these patients may be more susceptible to complications from glaucoma surgery such as wound leaks or blebrelated infections (30 32).

4.SUMMARY

The decision to proceed with glaucoma surgery is usually straightforward: surgery is indicated when target pressures are not achieved or when optic disc and/or visual field loss occurs despite maximally tolerated medical and laser therapies. However, risk factors

for progression other than IOP must be evaluated as well. The presence of numerous risk factors in addition to IOP suggests the need for more aggressive target pressures and treatment. Early surgery may be indicated when compliance with medical therapy is a problem, or in developing countries where the cost of medications may be prohibitive. Large diurnal pressure variations in a patient with severe disc damage may also be an indication for earlier surgery even if the mean IOP is at target. Conversely, quality of life issues should not be used in the decision to either proceed with or delay with surgery.

Once the decision to proceed with surgery has been made, careful pre-operative evaluation must be performed to determine the optimal site and type of glaucoma surgery, including the use of antifibroblastic agents. This will help to improve the success of the surgery and minimize potential complications.

REFERENCES

1.Collaborative Normal Tension Glaucoma Study Group (CNTGS). The effectiveness of intra ocular pressure reduction in the treatment of normal tension glaucoma. Am J Opthalmol 1998; 126:498 505.

2.The AGIS Investigators. The Advanced Glaucoma Intervention Study (AGIS): 7. The relation ship between control of intraocular pressure and visual field deterioration. Am J Opthalmol 2000; 130:429 440.

3.Kass MA, Heuer DK, Higginbotham EJ, Johnson CA, Keltner JL, Miller JP et al. The Ocular Hypertension Treatment Study: a randomized trial determines that topical ocular hypotensive medication delays or prevents the onset of primary open angle glaucoma. Arch Ophthalmol 2002; 120:701 713.

4.Spaeth GL. OHTS one year later: has it reduced my threshold for treatment? American Academy of Ophthalmology Subspecialty Day Glaucoma Meeting. Anaheim, CA, Nov 15, 2003.

5.Drance S, Anderson DR, Schulzer M. Collaborative Normal Tension Glaucoma Study Group. Risk factors for progression of visual field abnormalities in normal tension glaucoma. Am J Ophthalmol 2001; 131:699 708.

6.Lichter PR, Musch DC, Gillespie BW, Guire KE, Janz NK, Wren PA et al. Interim clinical outcomes in the Collaborative Initial Glaucoma Treatment Study comparing initial treatment randomized to medications or surgery. Ophthalmology 2001; 108:1943 1953.

7.Tielsch JM, Sommer A, Katz J, Royall RM, Quigley HA, Javitt J. Racial variations in the prevalence of primary open angle glaucoma. The Baltimore Eye Survey. JAMA 1991; 266:369 374.

8.Herndon LW, Weizer JS, Stinnett SS. Central corneal thickness as a risk factor for advanced glaucoma damage. Arch Ophthalmol 2004; 122:17 21.

9.Leske MC, Heijl A, Hussein M, Bengtsson B, Hyman L, Komaroff E, EMGT Group. Factors for glaucoma progression and the effect of treatment: The Early Manifest Glaucoma Trial. Arch Ophthalmol 2003; 121:48 56.

10.Gordon MO, Beiser JA, Brandt JD, Heuer DK, Higginbotham EJ, Johnson CA et al. The Ocular Hypertension Treatment Study: baseline factors that predict the onset of primary open angle glaucoma. Arch Ophthalmol 2002; 120:714 720.

11.The AGIS Investigators. The Advanced Glaucoma Intervention Study (AGIS): 12. Baseline risk factors for sustained loss of visual field and visual acuity in patients with advanced glaucoma. Am J Ophthalmol 2002; 134:499 512.

12.Kass MA, Meltzer DW, Gordon M, Cooper D, Goldberg J. Compliance with topical pilocarpine treatment. Am J Ophthalmol 1986; 101:515 523.

13.Tsai JC, McClure CA, Ramos SE, Schlundt DG, Pichert JW. Compliance barriers in glaucoma: a systematic classification. J Glaucoma 2003; 12:393 398.

14.Thomas R, Kumar RS. Primary open angle glaucoma: the developing world perspective. American Academy of Ophthalmology Subspecialty Day Glaucoma Meeting. Anaheim, CA, Nov 15, 2003.

15.Thomas R, Sekhar GC, Kumar RS. Glaucoma management in developing countries: medical, laser, and surgical options for glaucoma management in countries with limited resources. Curr Opin Ophthalmol 2004; 15(2):127 131.

16.Janz NK, Wren PA, Lichter PR, Musch DC, Gillespie BW, Guire KE et al. The Collaborative Initial Glaucoma Treatment Study: interim quality of life findings after initial medical or surgical treatment of glaucoma. Ophthalmology 2001; 108:1954 1965.

17.Wilensky JT. The role of diurnal pressure measurements in the management of open angle glaucoma. Curr Opin Ophthalmol 2004; 15:90 92.

18.Liu JHK, Bouligny RP, Kripke DF, Weinreb RN. Nocturnal elevation of intraocular pressure is detectable in the sitting position. Invest Ophthalmol Vis Sci 2003; 44:4439 4442.

19.Larsson LI, Rettig ES, Brubaker RF. Aqueous flow in open angle glaucoma. Arch Ophthalmol 1995; 113:283 286.

20. Liu JHK. Diurnal measurement of intraocular pressure. J Glaucoma 2001; 10(suppl 1):S39 S41.

21.Asrani S, Zeimer R, Wilensky J, Gieser D, Vitale S, Lindenmuth K. Large diurnal fluctuations in intraocular pressure are an independent risk factor in patients with glaucoma. J Glaucoma 2000; 9:134 142.

22.Liu JH, Zhang X, Kripke DF, Weinreb RN. Twenty four hour intraocular pressure pattern

associated with early glaucomatous changes. Invest Ophthalmol Vis Sci 2003; 44:1586 1590.

23.Brubaker RF. Targeting outflow facility in glaucoma management. Surv Ophthalmol 2003; 48(suppl 1):S17 S20.

24.Medeiros FA, Pinheiro A, Moura FC, Leal BC, Susanna R Jr. Intraocular pressure fluctuations in medical versus surgically treated glaucomatous patients. J Ocul Pharmacol Ther 2002; 18:489 498.

25.Jay JL, Allan D. The benefit of early trabeculectomy versus conventional management in primary open angle glaucoma relative to severity of disease. Eye 1989; 3:528 535.

26.Hitchings RA, Migdal CS, Wormald R et al. The Primary Treatment Trial: changes in the visual field analysis by computer assisted perimetry. Eye 1994; 8:117 120.

27.The Fluorouracil Filtering Surgery Study Group. Five year follow up of the fluorouracil filtering surgery study. Am J Ophthalmol 1996; 121:349 366.

28.Parrish RK II, Schiffman JC, Feuer WJ, Heuer DK. Fluorouracil Filtering Surgery Study Group. Prognosis and risk factors for early postoperative wound leaks after trabeculectomy with and without 5 fluorouracil. Am J Ophthalmol 2001; 132:633 640.

29.Singh K, Mehta K, Shaikh NM, Tsai JC, Moster MR, Budenz DL, Greenfield DS, Chen PP, Cohen JS, Baerveldt GS, Shaikh S. Trabeculectomy with intraoperative mitomycin C versus 5 fluorouracil. Prospective randomized clinical trial. Ophthalmology 2000; 107:2305 2309.

30.Lehmann OJ, Bunce C, Matheson MM, Maurino V, Khaw PT, Wormald R, Barton K. Risk factors for development of post trabeculectomy endophthalmitis. Br J Ophthalmol 2000; 84:1349 1353.

31.DeBry PW, Perkins TW, Heatley G, Kaufman P, Brumback LC. Incidence of late onset bleb related complications following trabeculectomy with mitomycin. Arch Ophthalmol 2002; 120:297 300.

32.Mac I, Soltau JB. Glaucoma filtering bleb infections. Curr Opin Ophthalmol 2003; 14:91 94.

exposes the deeper layer of the scleral bed at the surgical limbus. In the upper part of the scleral bed, there are transparent corneal lamellae through which brown iris is visible. This is also recognizable in the photograph (Fig. 2.2) which records the surgeons view. Note that the corneal tissue in the scleral flap does not reach as far as the corneal lamellae in the deeper scleral bed (Fig. 2.1). Posterior to the cornea in the scleral bed is a grey band, which is the trabecular meshwork, and at the posterior border of this grey band dense scleral tissue is visible. The junction of the posterior limit of the grey band and the sclera is the external landmark for the scleral spur and canal of Schlemm. Deeper dissection at this landmark will lead the surgeon directly to the canal of Schlemm (e.g. for trabeculotomy). The scleral spur extends slightly posterior to this junction. It is important to recognize these landmarks, particularly when performing trabeculotomy or nonpenetrating filtration surgery. The ciliary body is attached to the junction of the trabecular band and the sclera at the scleral spur. Dissection through the sclera posterior to this junction will expose the ciliary body and the pars plicata which if cut may result in significant bleeding.

In planning filtration surgery, bear in mind that the extraocular rectus muscles are inserted around the limbus area. As the muscle insertions are placed well back from the limbus, for example, the superior rectus is 7.75 mm behind the limbus, the extraocular muscles do not interfere with filtration surgery which for the most part is performed within 3 4 mm posterior to the limbus. With a limbus-based conjunctival flap, if the scleral flap is dissected further back, great care must be taken not to cut the extraocular muscles (especially superior rectus) (Fig. 2.3).

1.INTRODUCTION

Anesthetic techniques for filtration surgery have evolved over the years. Table 3.1 shows this evolution. Selection of the appropriate anesthetic method for glaucoma surgery depends on the pre-operative assessment of the patient, surgeon’s technique, and the complexity of the surgical procedure.

Although glaucoma surgery is relatively low-risk, glaucoma patients represent a high-risk population, as they tend to be at extremes of age and to have concomitant systemic disease. Mortality for ophthalmic surgery is significantly lower than for general surgery (1 4). General anesthesia is more likely to cause adverse systemic effects. The incidence of anesthesia-related deaths in the operating room for all types of surgery is approximately 1 in 3000. The mortality rate associated with ophthalmic surgery is lower at 1 in 5000 or less (5).

Prior to surgery, every glaucoma patient should be carefully evaluated so that potential complications can be identified and reduced to as close to zero as possible.

2.PRE-OPERATIVE EVALUATION

The goals of pre-operative evaluation are to psychologically prepare the patient, to establish a doctor patient relationship, to plan peri-operative management, to assess local and systemic risk, to obtain informed consent, and to meet other legal requirements. When approaching a pre-operative patient, it is important to consider the following points:

. Every patient undergoing a surgical procedure must have a comprehensive and timely medical history and physical examination and the results should be inserted in the medical record preferably by the patient’s personal physician. A thorough review of all medications should also be included. The interaction

Table 3.1 Evolution of Anesthetic Techniques for Filtration Surgery