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Common glaucoma-related problems

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Dr Lance Liu
MBBS FRANZCO
Melbourne, VIC

 

When patients present with an eye problem, it is common not only to find the cause or causes but also discover other incidental ocular conditions.

Think back to the last few patients you saw recently and you may realise that most usually have more than one eye problem.

Given that we are initially guided by the patient’s symptoms and medical history, one may be forgiven for looking for a single pathology and neglecting others, for example, focusing our attention on the retina in a patient who presents for a diabetic eye check. Part of the reason for this is that our learning is based on information sources (textbooks, conferences, publications and public health awareness programs) that are disease-specific and oriented. We are quick to focus on one area of the eye but what happens if a patient has more than one eye problem?

Patients usually present for an eye examination when they are experiencing symptoms related to their vision, ocular discomfort such as dry eye symptoms, when they are at risk of developing symptoms like diabetes or when they have family history of glaucoma. The prevalence of eye conditions increases with age, with 80 per cent of the world’s blindness due to refractive error, cataract, glaucoma, diabetes and macula degeneration.

Given that many eye conditions are asymptomatic in the early stages, it is not uncommon for patients to have early signs of more than one of these conditions. Before deciding which treatment is best, one needs to determine whether their conditions are related. Remember that any chosen treatment can exacerbate other eye problems, for example: topical steroids and cataract.

101. Figure 1. Optic Disc Photo _F

Figure 1. Optic disc showing damage inferiorly with a Drance haemorrhage Photo: Dr L Liu

Dry eye

As an example, let us look at glaucoma. It is defined as a progressive optic neuropathy where accelerated loss of retinal ganglion cells leads to changes of the optic nerve and retinal nerve fibre layer, usually leading to loss of the peripheral vision initially and then loss of the central vision later. There are many risk factors associated with the development and progression of glaucoma, but intraocular pressure is the only risk factor we can modify. Treatment includes topical IOP-lowering drops, laser procedures (iridotomy, trabeculoplasty, cyclodiode) or glaucoma filtering operation such as a trabeculectomy and aqueous drainage devices (such as tube surgery).

Glaucoma is a life-long condition that once diagnosed usually requires ongoing treatment and monitoring. However, we know that up to 50 per cent of glaucoma is undiagnosed at the time of the consultation1 so it is important to exclude glaucoma in all patients.

It has been shown that topical glaucoma treatments can cause or exacerbate dry eye symptoms. The latter is usually related to ocular surface disease (OSD) which can also be caused by blepharitis or rarely keratoconjunctivitis sicca. One of the main causes is related to the preservatives found in these drops, the most common being benzalkonium chloride.2 The severity of the symptoms is related to the preservative load the patient receives: concentration, number of drops per day and exposure over time. These preservatives can either initiate or contribute to pre-existing OSD symptoms. Recently, non-preservative glaucoma drops have become available, which can be initiated in those with newly diagnosed glaucoma and pre-existing OSD, or substituted in those glaucoma patients who develop dry eye symptoms.

101. Figure 2. Anterior Blepharitis _F

Figure 2. Anterior blepharitis

Cataracts

Other conditions may be present at the initial consultation or develop subsequently. Cataract, the cloudiness of the natural lens in the eyeball, eventually worsens over time and may be accelerated by a number of conditions including diabetes, steroids and ironically, glaucoma treatments (drops, laser3 or surgery4). As the cataract worsens, the vision can become impaired either slowly or quickly, depending on the type of cataract. The ongoing enlargement of the lens can also lead to angle closure that can cause the IOP to rise or worsen glaucoma. Current technologies allow us to remove the cataracts successfully in 98-99 per cent of cases.

With increasing age, it is not uncommon for cataract and glaucoma to co-exist in the same patient although the severity of each condition may vary. There are various treatments available for glaucoma and cataracts; however, although there is usually vision improvement following cataract surgery, the vision loss from glaucoma is permanent. What is the role of cataract surgery in the glaucoma patient?

101. Figure 3. Cortical Cataract _F

Figure 3. Cortical cataract   Photo: Dr L Liu

Cataract surgery

Traditional teaching has always been that we remove cataracts for vision reasons and perform glaucoma surgery for glaucomatous progression. Once diagnosed, glaucoma is a life-long condition that requires ongoing treatment and monitoring. A cataract, on the other hand, progresses slowly over time—but may be accelerated by the treatments we have to stabilise the glaucoma—and usually requires surgical removal.

Does one wait until the vision is significantly impaired before removing the cataract or should this be removed earlier in the glaucoma patient’s lifetime? It raises another issue: how does one define a cataract? Although we rely on the Snellen/LogMAR acuity test to determine the severity, cataracts can also affect refraction, colour discrimination and contrast sensitivity, depending on the pathologic type. We do not routinely test the latter two visual modalities,5 so a patient with a cortical cataract may complain of glare but the vision may be still 6/9.

From a glaucoma perspective, there has been a trend for early cataract surgery during the glaucoma patient’s lifetime. Removing the cataract early can improve the patient’s current level of vision, stabilise (compare: angle closure glaucoma patients) or lower the IOP slightly, allow easier clinical examination and monitoring of the glaucoma, and improve the imaging of the optic nerve and surrounding retinal nerve fibre layer.6

From a surgical perspective, glaucoma filtering surgery is easier when the patient is pseudophakic and in patients undergoing cataract surgery following a trabeculectomy, there is an increased rate of bleb failure. Earlier cataract surgery is technically easier in patients with pseudoexfoliation and may reduce the glaucoma risk in patients with angle closure.

There is a lot of anecdotal evidence to support the trend for early cataract surgery but we still await long-term prospective trials in this area.

In the past, we have concentrated on the patient’s main problem (usually the glaucoma) and tended to neglect the other eye problems the patient may have until it becomes visually significant. Given the high success rate of cataract surgery, there is a strong argument to consider this earlier in the glaucoma patient’s lifetime to maximise their visual potential, improve the clinician’s ability to monitor the disease and plan for any future glaucoma procedures, if needed. This decision needs to take into account the severity of the glaucoma, the degree of cataract and the patient’s perceived visual disability.

Other problems

Then there are many patients who present with other non-glaucoma related problems such as early visual loss due to cataracts or sore, gritty eyes. It is important to exclude not only glaucoma in these patients, but also those who are at risk of developing this disease. The most common risk factors are age, IOP, a family history of glaucoma and the central corneal thickness.

Other risk factors for open angle glaucoma include ocular conditions, for example myopia, pseudoexfoliation and so on, systemic diseases such as hypertension and epidemiological causes. However, the risk factor for angle closure glaucoma is iridotrabecular contact, which is most commonly found in the dark when the pupil is physiologically dilated. Epidemiologically, it is more commonly found in patients with increasing age, females, and those patients of Asian origin, although it occurs in Caucasians too.

Anatomically, iridotrabecular contact is found in eyes that are hypermetropic, have shallower anterior chambers and are smaller. Gonioscopy remains the gold standard in assessing the angle as one will miss between 25-50 per cent of angle closure if relying on the central anterior chamber depth, Van Herick7 and flash light tests. Therefore, gonioscopy needs to be performed to exclude angle closure or iridotrabecular contact.

101. Figure 4. Gonioscopy Of Angle _F

Figure 4. Gonioscopy of angle   Photo: Dr L Liu

Patients usually have multiple eye problems—some obvious, some in the early stages and some asymptomatic. Therefore, it is important to find the cause or causes of their presenting problem and then, one needs to look for other eye conditions. In the case of glaucoma, this includes performing gonioscopy to exclude angle closure and should be part of the routine eye assessment in all patients,8 regardless of their presenting eye problems.

 

  1. Varma R et al. An assessment of the health and economic burdens of glaucoma. Am J Ophthalmol 2011; 152: 515-522.
  2. Baudouin C, Riancho L. In vitro studies of antiglaucomatous prostaglandin analogues: travoprost with and without benzalkonium chloride and preserved latanoprost. IOVS 2007; 48: 4123-4128.
  3. Heijl A, Leske MC, Bengtsson B, Hyman L, Bengtsson B, Hussein M. Reduction of intraocular pressure and glaucoma progression: results from the Early Manifest Glaucoma Trial. Arch Ophthalmol 2002; 120: 1268-1279.
  4. Feiner L, Piltz-Seymour JR. Collaborative Initial Glaucoma Treatment Study: a summary of results to date. Curr Opin Ophthalmol 2003; 14: 106-111.
  5. Liu L. There is insufficient evidence to recommend lens extraction as a treatment for primary open-angle glaucoma: an evidence-based perspective--comment. Clin Experiment Ophthalmol 2012; 40: 6: 647-648.
  6. Mwanza JC, Bhorade AM, Sekhon N et al. Effect of cataract and its removal on signal strength and peripapillary retinal nerve fiber layer optical coherence tomography measurements. J Glaucoma 2011; 20: 37-43.
  7. Foster PJ, Devereux JG, Alsbirk PH, Lee PS, Uranchimeg D, Machin D, Johnson GJ et al. Detection of gonioscopically occludable angles and primary angle closure glaucoma by estimation of limbal chamber depth in Asians: modified grading scheme.Br J Ophthalmol 2000; 84: 2: 186-192.
  8. NHMRC glaucoma guidelines 2010.


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