Ординатура / Офтальмология / Английские материалы / Glaucoma Medical Therapy Principles and Management_Netland_2008

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260 Glaucoma Medical Therapy

most ophthalmologists view the potential complications of glaucoma surgery as serious enough that other therapeutic modalities should be employed first. Therefore, for most patients, surgery should be performed only when medical therapy has failed or is likely to fail. In other words, surgery to lower IOP is generally indicated for glaucoma patients on maximum tolerable medical therapy who have had maximal laser benefit and whose target IOP is exceeded.

15.1 MAXIMUM MEDICAL THERAPY

With six available classes of topical medications to use for IOP lowering, there is a seemingly bewildering array of treatment choices.1 The large number of these choices has contributed to the ambiguity of the term ‘‘maximum medical therapy.’’ The added benefit of a third or fourth topical agent is often minimal for most patients, and certainly the use of six classes of drugs is not feasible. Further, in clinical practice, combinations of each available medical agent at their highest concentrations are not indicated before a surgical approach is considered.

A medical treatment regimen needs to be customized to each individual patient to optimize the benefits and avoid the risks of the administered drugs. Clinicians should generally measure IOP more than once and preferably at different times of the day when establishing baseline IOP prior to surgery. Assuming topical agents have been administered appropriately, a single determination of IOP may be sufficient when it is markedly elevated. Certainly, drugs that have intolerable side effects should be excluded from consideration when assessing whether medical control of IOP can be achieved satisfactorily. An ineffective drug should be discontinued and similarly excluded. Medical contraindications may preclude the use of various agents.

Poor adherence or persistence with a prescribed medical regimen also needs to be considered when assessing maximum tolerable medical therapy. Patients who continue to worsen despite apparent IOP control should be questioned about their use of prescribed medications. Patients who are administering their medication only prior to a scheduled visit to the ophthalmologist, and not during the interval between visits, most likely will benefit little from long-term medical treatment. Patients who have well-controlled IOP when under the surveillance of their ophthalmologist, but who cannot remember to use their eye drops or are poorly persistent for a multitude of other reasons, ought to be considered for surgical treatment. With any patient on maximum tolerable medical therapy, poor adherence or persistence should be suspected because of the greater probability of side effects when numerous drugs are prescribed, as well as the difficult dosing schedules. In the latter situation, patients may have had prescribed six different eye drops with schedules varying from one to four times daily. Therefore, the term ‘‘maximum medical therapy’’ is used to indicate that no further escalation of medical treatment is available, appropriate, or likely to provide a clinically significant lowering of IOP.

15.2 THE OPTIC NERVE AND TARGET INTRAOCULAR PRESSURE

In the absence of structural of functional findings on examination of the optic nerve, the clinician certainly must refrain from rapidly advancing therapy to an intolerable or unacceptable level. Nevertheless, advancing optic disk or retinal nerve fiber layer damage even without observable visual field loss is progression and under certain circumstances can be an indication for surgery. Efforts should be directed at estimating the rate or risk of progression. Glaucoma patients who are at highest risk for progression should be identified and the threshold for surgery lowered. Conversely, those glaucoma patients who are at lowest risk should be followed with structural and functional testing of the optic nerve to identify early progression.2 The risk of progression needs to be weighed against the risks and benefits of surgery and the life expectancy of the patient.

Regardless of whether there is an apparently adequate IOP with medical treatment, surgery is indicated if there is progressive worsening of the visual field, progressive optic disk damage, or thinning of the retinal nerve fiber layer. IOP that consistently exceeds the target suggests the possibility of progression even if the visual field, the optic disk appearance, and retinal nerve fiber layer are unchanged. The extent and location of damage may alter the threshold for surgery. Patients with advanced damage or damage threatening central vision should have lower IOP than those with early disease. One also should keep in mind that elderly patients with slow progression may have no change in quality of life during their lifetime and often can be observed on medical treatment. In addition, patients who have become blind from glaucoma in one eye despite good medical management and those with a strong family history of blindness from glaucoma are candidates for earlier surgical intervention. With so many classes of medication available, it is essential that the ophthalmologist set an appropriate IOP target and not wait for progressive visual field or optic disk changes before escalating therapy.

15.3 NEUROPROTECTION

Neuroprotection is a therapeutic paradigm for slowing or preventing death of neurons, including retinal ganglion cells and their axons (optic nerve fibers), to maintain their physiological function.3 The underlying theoretical basis for a neuroprotective strategy in glaucoma appears sound. Moreover, considerable data from retinal ganglion cell culture and animal models of optic nerve injury support a neuroprotective strategy. Randomized controlled trials are evaluating neuroprotective strategies in patients with glaucoma. For neuroprotection to become an integral part of our therapy for glaucoma, it is necessary that clinical research complement and extend available basic research. If neuroprotection does become a viable therapy for glaucoma, it is likely that it will be complementary, and not replace, IOP-lowering medical therapy.

262 Glaucoma Medical Therapy

15.4 LASER SURGERY

Many types of open-angle glaucoma are amenable to treatment with laser trabeculoplasty. In contrast, only some types of closed-angle glaucoma, particularly (but not exclusively) those with a component of pupillary block, are amenable to treatment with laser iridotomy. Laser trabeculoplasty is usually performed over 3608 of the anterior chamber angle during one or two sessions using appropriate treatment parameters. Except in situations where it has not performed correctly or in the presence of pseudoexfoliative glaucoma, retreatment is seldom effective. Although retreatment with selective laser trabeculoplasty has been touted as more effective than argon laser trabeculoplasty, studies to prove this have not yet been reported. Retreatment with either laser can be attempted, however, before proceeding to trabeculectomy if the clinician and the patient are willing to incur certain risks: possible deterioration of the condition during the additional delay, a reduced level of expectation for success, and temporary or sustained elevation of IOP.

Certain types of patients tend to respond poorly to laser surgery; therefore, laser surgery should not be offered routinely to patients with childhood glaucoma, inflammatory glaucoma, angle-recession glaucoma, iridocorneal endothelial syndrome, corticosteroid-induced glaucoma, and chronic angle-closure glaucoma. Laser surgery is difficult, if not impossible, to perform in certain other patients, such as those who cannot cooperate or hold a steady position at the laser, whose cornea is edematous, or whose angle cannot be adequately visualized.

15.5 SURGICAL CONSIDERATIONS

15.5.1Nonpenetrating Drainage Surgery. For some surgeons, nonpenetrating glaucoma surgery (NPGS) provides an alternate surgical approach to trabeculectomy for moderate lowering of IOP in glaucoma patients. Lower IOP can be achieved with trabeculectomy than with NPGS, but short-term complications are fewer with NPGS. Further, NPGS is technically more challenging with a longer operative time. Despite potential advantages, there is still need for further evaluation of the technical details and standardization of the technique to improve the learning curve and efficiency of the procedure before NPGS is adopted widely.

15.5.2Sequence of Laser Surgery and Trabeculectomy. The appropriate sequence of surgical therapy in patients whose IOP is uncontrolled by maximum tolerable and

effective medical treatment is debatable. After follow-up of 4 to 7 years, the Advanced Glaucoma Intervention Study,4 a randomized, controlled trial sponsored by the National Eye Institute and initiated in 1988 to compare visual outcomes of two sequences of surgical therapy, has suggested that initial trabeculectomy, rather than laser trabeculoplasty, may be preferable in white patients. In contrast, laser trabeculoplasty may be preferable for a first surgical intervention in African American patients. Longer follow-up and confirmatory data from other studies will be essential for determining whether the race-related differences in treatment outcome persist over the long term.

15.6 SURGICAL CONTRAINDICATIONS

A blind, painful eye is an absolute contraindication to glaucoma surgery. Because there is no visual benefit to be gained, pain control can be more safely and effectively achieved through other means. Surgery also is contraindicated for a blind, painless eye. In addition to being unable to improve vision, the clinician would be incurring a small risk of inducing sympathetic ophthalmia. Eyes with ocular neoplasms and individuals with poor hygiene should be considered poor risks for trabeculectomy; instead, noninvasive surgical therapy, such as cyclodestructive surgery, should be considered. Patients with iris neovascularization or neovascular glaucoma should be treated first with retinal ablation by panretinal photocoagulation and/or peripheral cryotherapy to induce regression of neovascularization.

15.7 CONCLUDING COMMENT

The clinician needs to keep in mind that the goal of glaucoma therapy is to sustain the vision-related quality of life and to maintain both the visual field and the structural integrity of the optic nerve. When the clinician is considering whether or when to advance from medical to surgical therapy, individual patient variations need to be taken into account. Selection of a target IOP for each individual eye is important, and surgical intervention should be considered if this target is not achieved with the appropriate medical therapy. Although these indications represent a prevailing view, they should be considered only as guidelines,5,6 and not as a substitute for the experience and judgment of an individual ophthalmologist. Ophthalmic practice is continually evolving, and indications are likely to change as new knowledge is acquired.

REFERENCES

1.Zimmerman TJ, Fechtner RD. Maximal medical therapy for glaucoma. Arch Ophthalmol. 1997;115:1579–1580.

2.Weinreb RN, Friedman DS, Fechtner RD, et al. Risk assessment in the management of patients with ocular hypertension. Am J Ophthalmol. 2004;138:458–467.

3.Weinreb RN, Levin LA. Is neuroprotection a viable therapy for glaucoma? Arch Ophthalmol. 1999;117:1540–1544.

4.AGIS Investigators. The Advanced Glaucoma Intervention Study (AGIS), 4: comparison of treatment outcomes within race—seven-year results. Ophthalmology. 1998;105: 1146–1164.

5.Weinreb RN, Crowston JG, eds. Glaucoma Surgery. Amsterdam: Kugler Publications; 2005.

6.Weinreb RN, Mills RP, eds. Glaucoma Surgery: Principles and Techniques. 2nd ed. New York: Oxford University Press; 1998. American Academy of Ophthalmology Monograph Series; No 4.

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Questions

Chapter 1

1.The main route of topical ocular drug delivery into the anterior chamber of the eye is through the

a.Conjunctiva

b.Cornea

c.Eyelids

d.Sclera

2.The blood–ocular barrier includes tight junctions between the

a.Capillary endothelial cells in the retina and iris

b.Nonpigmented ciliary epithelial cells

c.Retinal pigment epithelial cells

d.All of the above

3.Iris color can interfere with ocular drug effects.

a.True

b.False

c.Unknown

d.Maybe

4.The conjunctival cul-de-sac compartment has a volume of

a.1 mL

b.7 mL

c.50 mL

d.100 mL

5.Nasolacrimal occlusion may

a.Decrease systemic absorption of topically applied drugs

b.Increase the ocular penetration of topically applied drugs

c.Improve the therapeutic index of topically applied drugs

d.All of the above

Chapter 2

6.Prostaglandin analogs reduce intraocular pressure by

a.Reducing aqueous production

b.Reducing outflow facility

c.Reducing episcleral venous pressure

d.Increasing uveoscleral outflow

7.A documented side effect associated with latanoprost use is

a.Darkening of iris color

b.Lowering of blood pressure

c.Lowering of heart rate

d.Impotence