Chronic glaucoma - A diagnosis not to be missed

Ming-Pong Yiu 姚銘邦, Wan-Luk 陸雲, Kit-Kuen Ip 葉傑權, Yuk-Kwan Yiu 姚玉筠

HK Pract 2005;27:275-277

Summary

In our daily general practice, we will encounter elderly patients complaining of blurred vision. Although many of them may be normal after clinical assessment, exception does occur. As family physicians, we should be cautious of this common complaint. Illustrated below is a case of painless visual loss which turned out to be a condition of chronic glaucoma. The presentation of chronic glaucoma and its difficulties in detection are also briefed. Family physician should refer the suspected patients to ophthalmologist for an comprehensive assessment because of the subtle presentation and findings.

摘要

日常診症中，常有老年病人訴說視力模糊，雖然大多數情況，經臨床檢查後都屬於正常，但作為家庭醫生，我們仍應謹慎處理。以下的案例，表現為無痛的視力不清，檢查確診為慢性青光眼。 本文亦描述慢性青光眼的表現及其診斷的困難之處。鑒於此病的症狀缺乏特發性，家庭醫生應轉介疑似病人由專科醫生做詳細檢查。

Introduction

Visual deterioration is a common complaint among the elderly patients in general practice. Many cases are due to cataract which has a high prevalence in the elderly. However, it is not uncommon to see cases in which elderly presented with visual deterioration with clear lenses and satisfactory visual acuity.

Chronic glaucoma is one of the common causes of visual loss in the elderly. It could easily be missed in our daily practice as it often lacks obvious clinical signs and the patients may not notice any symptoms.

The following illustrated a case of chronic glaucoma which was suspected after an incidental detection of visual field loss.

Case

Mr. P, 69 years old, had hypertension for 4 years and was followed up in the general out- patient clinic. During a routine visit, Mr. P said that he had decreased vision of his right eye for 2 weeks. There were no other associated complaints. The cardiovascular and neurological examination findings were normal. With the preoccupation for the diagnosis of cataract in mind, the lenses were examined and the visual acuity was checked. We were surprised, the lenses were clear. The unaided visual acuity of the right eye was 10/35 and 10/15 with the pinhole. The left eye was 10/15 unaided. Both fundi were examined. Red reflexes were present and optic discs were normal. There were no abnormal blood vessels or retinal haemorrhage seen.

Finally, the visual fields of both eyes were checked with a red target in the consultation room. It aroused our interest to find that the visual field of the inferior nasal side of the right eye was constricted while the visual field of the left eye was normal. The patient was referred to the ophthalmologist for further assessment for suspicion of chronic glaucoma.

The diagnosis by the ophthalmologist was chronic open angle glaucoma. The patient then had a laser operation and timolol eye-drop was prescribed postoperatively.

Although the patient allegedly had the symptom for 2 weeks only, it might have actually developed over a longer time without the patient having noticed it.

Discussion

In the primary care setting, we see elderly patient presenting with decreased vision from time to time. The most common causes of chronic visual loss include cataract, age related macular degeneration, diabetic retinopathy and chronic glaucoma. While cataract and diabetic retinopathy are relatively easier to detect by examining the lens and the fundi, it is more difficult to diagnose chronic glaucoma especially in the early stages as there may be no florid clinical signs

Glaucoma is a disease that gradually steals sight without warning and often without symptoms. Visual loss is caused by damage to the optic nerve.¹ The risk factors are elevated intraocular pressure (IOP), family history of a first-degree relative, advanced age, diabetes, high blood pressure, myopia, eye injury and steroid treatment. (Table 1)² In fact, glaucoma is ranked after cataract as the second leading cause of blindness in the world, and nearly half of the glaucoma-related blind people reside in East Asia.³ Therefore it is important for family physicians to have a high index of suspicion for chronic glaucoma and be familiar with the presentation of glaucoma and its physical signs.

Acute closed angle glaucoma has typical symptoms of eye pain, redness, blurred vision, sometimes associated with headache and seeing haloes around light. It usually occurs at night in elderly patients.⁴ A unilateral red eye associated with vomiting is considered as acute angle-closure glaucoma until proven otherwise. Typical eye signs are mid-dilated pupil, conjunctival injection, and corneal hazziness. Tonometry will reveal intraocular pressure of more than 21mm Hg though normal tension may exist.

On the contrary, chronic open angle glaucoma is more difficult to detect as its onset is more insidious. It is usually asymptomatic especially in the early stages. After loss of more than 40 percent of the nerve fibres, patients may notice a gradual loss of peripheral vision, or "tunnel vision."⁵

On examination, there will be no abnormalities in lens appearance or visual acuity. There may be an increase in cup to disc ratio to > 0.5 but it only occurs in the late stage of the disease.

Visual field defects are more severe in chronic glaucoma than in eyes with acute angle-closure glaucoma.³ Besides, the nasal area is the most commonly involved area in the early stage of chronic angle glaucoma, being noted in 52% of the superior and 58 % of the inferior hemifield in the mild group.³

However, there are many limitations in visual field testing. These include the daily "short term fluctuation", the way the target is presented, the size and brightness of the presenting target, the amount of ambient light and finally the cooperation of the patient. The ophthalmoscopic finding will show disc cupping and pallor. But this will only be detected in the advanced stage and it is usually difficult for family physicians to comment on the cup-disc ratio because of our limited experience.

In fact, direct ophthalmoscopy may be quite inaccurate when used in isolation, and there is considerable interobserver disagreement in the glaucomatous disc between the experienced and the junior ophthalmologists.⁶ In recent years, new techniques of optic nerve imaging have become widely available. These are scanning laser polarimetry, confocal laser ophthalmoscopy and optical coherence tomography.⁷ These provide more accurate and objective measurements for the purposes of glaucoma diagnosis and management. Of course, other causes of painless chronic visual loss in the elderly should be considered in our case, these include age-related macular degeneration, cataract and diabetic retinopathy. Together with chronic open angle glaucoma, these are the four commonest causes of chronic visual loss in the elderly.⁸

Lesson learnt

In our daily practice, we will sometimes skip some parts of eye examination like fundi examination and visual field examination because of the time constraint and uncooperation of the elderly. Sometimes, we may miss an important diagnosis if we perform an incomplete examination.

A complete eye examination should include examination of the eye lids, the cornea, the pupillary response, the ocular movement, nystagmus, visual acuity, visual field and the fundi.⁹ The fluorescent stain, Amsler grid chart and tonometry can also be checked if indicated.

Conclusion

In out-patient general practice, we usually see common complaints. This case illustrates that we should perform a complete physical examination in order not to miss an important diagnosis. It is especially true in the Hong Kong population as their knowledge of common eye diseases is limited. Lau et al¹⁰ showed that awareness of cataract in particular was high, in that over 90% of respondents had heard of it. However, only 22.9% of them could describe cataract symptoms correctly, and these percentages were even lower for glaucoma (10.2%) and age-related macular degeneration (<1%).

Although there is always time constraint in general out-patient clinic, we should have a high index of suspicion for the common but easily missed disease. We should be careful when performing clinical examination in order not to miss any subtle finding and should refer the at risk patients for more comprehensive assessment.

Acknowledgement

We would like to thank Dr. Jackson Woo (SMO of the Ophthalmology Department of Caritas Medical Centre) for his valuable comments and input in this case report.

Key messages

1. Chronic glaucoma is not uncommon in the elderly.
2. Chronic glaucoma is often asymptomatic in the early stages.
3. Visual field testing should be included in the eye examination during our daily practice.
4. Common causes of chronic visual loss in the elderly are cataract, glaucoma, age-related macular degeneration and diabetic retinopathy.