Unfortunately, he was not alone in his underutilization of gonioscopy. If I had 10 cents for every patient referred to me for the management of chronic open-angle glaucoma who actually suffered from primary chronic angle-closure glaucoma, I would have retired to the golf course by now. This article explains why gonioscopy is essential for managing glaucoma suspects and patients with glaucoma.
Figure 1. “All hope abandon, ye who [do not] enter here!”1 The case holding a Goldmann three-mirror goniolens should not remain unopened.
THE NEED FOR GONIOSCOPY
Primary angle-closure glaucoma is the second most common form of glaucoma in non-Asian populations, and relieving relative pupillary block with an iridotomy is mandatory in all cases. Unfortunately, the most common cause of errors in the disease's management that I encounter is related to an inadequate ocular examination (especially gonioscopic) before and after iridotomy. The physician must examine the patient's eye before performing an iridotomy in order to diagnose glaucoma and, if the disease is present, to determine its form. After the iridotomy has eliminated relative pupillary block, the physician must again use gonioscopy to assess the procedure's result and plan additional therapy for the patient.
A physician's omission or poor performance of gonioscopy can result in his misdiagnosis of primary open-angle glaucoma when a patient has chronic primary angle-closure glaucoma. Until the clinician examines the eye's angle gonioscopically to determine whether it is open and not occludable, he cannot diagnose primary open-angle glaucoma or any other form of glaucoma. Some eyes with primary angle closure have what we generally consider “normal” IOP of 15 to 18 mm Hg, because peripheral anterior synechiae have not yet sealed enough of the circumference of the drainage angle to raise the IOP. Without the presence of elevated pressure, many clinicians will not proceed with gonioscopy and therefore misdiagnose the patient unless an abnormal Van Herick test leads them to suspect a narrow angle.2
TECHNICAL TIPS
Method of Gonioscopy
Angle widths, as viewed through a goniolens in eyes with narrow angles, compose a spectrum. Regarding eyes at one end of that spectrum, most competent examiners can concur that the angle is closed or occludable. As to other eyes, however, experienced gonioscopists may disagree. The method of gonioscopy can be an issue because inadvertent pressure by an indentation goniolens on the central cornea can open an occludable angle, a finding that will lead to the incorrect diagnosis of an open and not occludable angle.3
In most cases, it is best first to evaluate the angle for the potential of closure with a Goldmann or Koeppe lens and then evaluate areas of angle closure with an indentation lens to differentiate appositional (reversible) from synechial (permanent) angle closure. If the physician sees that the angle is in a plateau configuration prior to iridotomy and suspects plateau iris syndrome, a laser iridotomy to eliminate relative pupillary block is still indicated because most such cases of angle closure are actually the result of relative pupillary block and not plateau iris syndrome.4
Van Herick Test
Slit lamp evaluation of the peripheral anterior chamber with Van Herick's technique can increase the examiner's suspicion that the eye's angle is closed, partially closed, or occludable.2 Although useful, this test is not foolproof. Occasionally, a normal Van Herick test can mask a closed angle. Physicians' index of suspicion for the presence of primary angle closure should increase in proportion to the degree of the patient's hyperopia, especially in older individuals with increased lenticular volume. It should be realized, however, that primary angle closure has occurred in young, myopic eyes.
Bilateral Examination
A painful red eye with a steamy cornea, mid-dilated pupil, and elevated IOP presents a different set of diagnostic problems than a quiet eye examined for chronic open-angle versus chronic angle-closure glaucoma. The physician must perform careful biomicroscopic and gonioscopic examinations of both of the patient's eyes in order to rule out other causes of acute glaucoma such as neovascular or uveitic glaucoma.
During his examination of the involved eye, the physician should look for keratic precipitates, anterior chamber inflammatory reaction, iris neovascularization, and lens intumescence in order to identify uveitic, neovascular, or phacomorphic glaucoma. All of these glaucomas require entirely different treatment than iridotomy for primary angle closure. Corneal edema may prevent gonioscopy of the involved eye, even with the topical application of anhydrous glycerin. In this case, it is useful to evaluate the width of the angle in the patient's fellow eye because primary angle closure is almost always bilateral. If the fellow eye's angle is wide open, suspect neovascular, uveitic, or some other acute secondary angle-closure glaucoma. A history of sudden visual loss in the involved eye 3 months earlier signifies a central retinal venous occlusion and indicates neovascular glaucoma.
LASER IRIDOTOMY
A diagnosis of primary angle closure necessitates laser iridotomy to eliminate relative pupillary block, the underlying mechanism of angle closure in nearly all cases. In those rare cases in which postlaser gonioscopy reveals plateau iris syndrome, the physician must perform argon laser gonioplasty to remove the plateau mechanism. Laser gonioplasty may also be used to break fresh peripheral anterior synechiae and restore trabecular function in nonplateau cases of angle closure.5 A more invasive method for breaking fresh peripheral anterior synechiae is operative goniosynechiolysis. This method's efficacy has been successful up to 1 year after the acute attack, but results are unpredictable.6 Identifying synechial angle closure entails careful postlaser gonioscopy.
Argon laser iridotomy was introduced in the 1970s and has proven safe and effective.7 Varying degrees of iris pigmentation and thickness cause differing tendencies to absorb or reflect laser light, however. For this reason, argon laser iridotomy is something of an art form, and Nd:YAG iridotomy has now become the preferred technique. Before the advent of lasers, when relieving relative pupillary block required a trip to the OR for surgical peripheral iridectomy, physicians occasionally used provocative tests despite their imperfection in an effort to assess an eye's propensity for angle closure. The high degree of safety of laser iridotomy has prompted many experienced surgeons to use the procedure in eyes with questionable angles.
For rare cases in which laser iridotomy is impossible due to corneal edema, poor patient cooperation, or a lack of equipment, the physician must perform a surgical iridectomy. Intraoperative gonioscopy can help the physician assess the degree of synechial closure and determine whether filtration surgery, rather than just an iridectomy, is a more definitive option.8
IN SUMMARY
Most errors in the management of primary angle-closure glaucoma are the consequence of inadequately examining the patient's eye before and after relieving its pupillary block by iridotomy or iridectomy. My argument is that gonioscopy is underused but required in all cases of glaucoma, in all glaucoma suspects, and for all eyes in which the physician suspects an angle capable of primary angle closure. The competent diagnosis and management of glaucoma is impossible without gonioscopy.
James A. Savage, MD, specializes in glaucoma consultation and surgery at Southeastern Eye Center in Greensboro, North Carolina. Dr. Savage may be reached at (336) 282-5000; iopdoctor@aol.com.
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3. Forbes M. Indentation gonioscopy and efficacy of iridectomy in angle closure glaucoma. Trans Am Ophthalmol Soc. 1974;LXXII:488-515.
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5. Wand M. Argon laser gonioplasty for synechial angle closure. Arch Ophthalmol. 1992;110:363-367.
6. Campbell DG, Vela AP. Modern goniosynechiolysis for the treatment of synechial angle closure glaucoma. Ophthalmol. 1984;91:1052-1060.
7. Beckman H, Barraco R, Sugar S, et al. Laser iridectomies. Am J Ophthalmol. 1971;72:393.
8. Chandler PA, Simmons RJ. Anterior chamber deepening for gonioscopy at time of surgery. Arch Ophthalmol. 1965;74:177-190.
