THE PATTERN AND SEVERITY OF PRIMARY GLAUCOMA IN QATAR

Al Mansouri F.
Ophthalmology Section, Surgery Department Hamad Medical Corporation, Doha, Qatar

Abstract:

Purpose: To describe the pattern of both types of primary glaucoma in Qatari adult patients and to outline the main problem related to its management. Material and

Methods: A random sample of Qatari patients with primary glaucoma either open angle or angle closure glaucoma in whom the diagnosis was made after the age of 30 years was studied over the last 2 years (1997-1998) by standard questionnaire as regards their personal and medical profile, and assessed ophthalmologically both subjectively and objectively.

Results: 195 patients were studied, of whom 29.7% had angle closure glaucoma. Early presentation was clearly shown in both type of glaucoma. Legal blindness was present in significant proportion of patients.

Comment: Glaucoma in Qatari patients presents at an early age, with substantial loss of visual function at presentation. Poor compliance is an obstacle for manage-ment in both types of glaucomas. The need for an educational campaign and a program for early detection is highly advised.

Introduction:

Primary glaucoma, by definition, refers to those cases of glaucoma in which there is no association with known ocular or systemic disorders that cause disturbance in the aqueous outflow. Primary open-angle glaucoma (POAG) is essentially a chronic, gradually progressive optic neuropathy. It is a symptom-free disease until the advanced stages when severe visual field loss develops or central fixation is involved. Early detection and management of the disease is important. In contrast, primary angle closure glaucoma (PACG) is bilateral and in the acute form a severe attack of angle-closure may occur rapidly with a painful eye and blurred vision. If left untreated, recurrent attacks may lead to blindness. The chronic form of PACG is usually asymptomatic with the angle becoming slowly and progressively closed.

A specialized glaucoma service clinic was established in the Ophthalmology Department, Hamad Medical Corporation (HMC), Qatar in late 1996 since when most glaucoma patients have been referred to this clinic. Glaucoma patients seen over the last two years represent approximately 10% of outpatients seen in the Ophthalmic Department. In 1997 of 31,763 patients, 16,281 were Qataris (51.3%) and 1145 were glaucoma patients (3.6%). In 1998, of 16,407 Qatari ophthalmic patients (53.4%) 948 were glaucoma patients (3.1%).

This study, on a sample of patients drawn from the glaucoma service was intended to show a cross-sectional profile of the pattern and severity of primary glaucoma in Qataris; to determine any medical risk factor associated with either type of primary glaucoma whether open angle or angle closure glaucoma; and to show the relative frequencies of the two different types of glaucoma. It was intended also to determine the degree of compliance for adequate management of the condition in the two different patterns of glaucoma. We tried to correlate our objective findings at presentation as determined ophthal-moscopically with cup/disc ratio estimation with the level of visual function subjectively (as determined with visual acuity measurement and visual fields evaluation).

Materials and Methods:

Primary glaucoma in Qatari nationals above the age of 30 years was studied on a sample obtained by selecting two or three cases each week from patients attending the clinic. Each case was interviewed by a standard questionnaire(1) for the age of onset of glaucoma(2), associated medical or systemic problems(3), gender(4), patients’ awareness of their ocular problems(5), their degree of compliance with therapy and(6) the presence of a family history of glaucoma. Each case was assessed also by the best corrected visual acuity (BCVA) with Snellen’s chart. Intraocular pressure (IOP) was measured with Goldmann applanation tonometry. Cup/disc ratios were estimated by using slit-lamp biomicroscopy and a 90 diopter fundus lens, slit-lamp examination was carried out in each case for assessment of the presence of pseudo-exfoliation or any other ocular abnormalities, and gonioscopy was performed with a Goldmann 3-mirror contact lens. The Shaffer (1) grading system was used at gonioscopy to differentiate the two main categories open-angle or angle-closure glaucoma.

Visual field data were provided by automated perimetry (Dicon LD 400). Visual field changes were classified in a fashion taken from Stewart and Chorak et al(2) who divided visual field into five stages: 1) within normal limits, 2) early changes (para-central or Seidel’s scotoma), 3) late arcuate changes, 4) central island remaining with complete superior and inferior arcuate scotomas, 5) unable to perform due to deep diffuse depression of the field with co-existent loss of central vision.

We excluded patients with congenital and secondary glaucomas. The compliance of patients for glaucoma therapy was determined as poorly administering their medical therapy or who did not turn up on regular follow-up visits, or when a patient was not accepting the surgical option when indicated.

The patient awareness of the glaucoma pathology was determined by the patient understanding that the treatment of glaucoma can only prevent further visual deterioration and would not improve the visual acuity or visual performance.

Results:

A total of 352 glaucomatous eyes of 195 Qatari patients with primary glaucoma were assessed between 1997 and 1998. Table1 shows 137 patients (70.3%) and 58 (29.7%) with POAG. There were slightly more females (58.4%) than males (41.6%) with POAG but there was a significant difference in PACG with a ratio of female to male approaching 2:1. It shows also a positive family history in approximately 34% of both types of glaucoma. Poor compliance occurred in 47.7% of all glaucoma patients. There were no significant differences in medical problems for either POAG or PACG. (Table 1)

Table 2 shows the distribution of different forms of glaucoma according to different age groups. No case of PACG was found in those more than the age of 70. The age group 50 to 59 showed no differences between POAG (31.3%) and PACG (37.9%). Twenty nine patients (21.1%) with POAG presented before 40 years of life and six patients (10.4%) with PACG.

Table 3 gives the visual acuity in both types. Of the eyes with primary glaucoma, 82 eyes (23.3%) [55 eyes (21.7%) in POAG and 27 eyes (27.3%) in PACG] had visual acuity between 6/60 and no perception of light (NPL). Advanced glaucomatous optic disc cupping (C/D ratio ž 0.8) was present in 36.4% of eyes with POAG and in 45.4% with PACG. (Table 1)

Table 5 shows the distribution of visual field stages in different forms of glaucoma. Ninety two eyes (36.4%) with POAG showed progressive visual field changes (stage 3 to 5) and 46 eyes (46.5%) with PACG. Thirty nine of 352 eyes were unable to perform a visual field test because of lack of cooperation during the test.

Discussion:

Glaucoma represents an important health problem and is one of the leading causes of blindness worldwide(3) . To this day the etiology of the disease is not completely known and the management remains unsatisfactory. An estimated 66.8 million people in the world will suffer from primary glaucoma by the year 2000, with 6.7 million people becoming blind(4). Epidemiologically glaucoma sufferers constitute two per cent or more of the blind population in different countries and it may be the second or third leading cause of blindness in different communities(5-9).

So far there are no statistics on glaucoma or glaucoma patients from Qatar. This prompted the study of the two main categories of primary glaucoma in a random sample drawn from 195 Qatari patients attending the glaucoma clinic service in 1997-1998. All had the condition for varying lengths of time. Angle closure glaucoma was present in 29.7% of our patients while the rest were of open angle type.

Primary glaucoma is known to be a heritable disease(10 -13). Our group of patients show positive family histories of equal degree (about 34.3%) in both types of glaucoma (almost third of cases have positive family history). This shows that the condition has no preference as regards hereditary element in either type of glaucoma in Qatari patients.

We consider compliance of patients to be a crucial factor for success in the management of glaucoma, since the objective is not only to control IOP, or to improve their visual function but to improve their health in general. Unfortunately, poor compliance in administering their medical therapy or in keeping follow-up appointments was present in a high proportion of patients. Ninety three patients (47.7%) of whole series showed poor compliance; of these 60 (64.5%) had progressive glaucoma changes. Glaucoma remained stable in the other 33 patients (35.5%). Similar to other reports(2,14) and in contrast to one report(15), non-compliance seemed to be associated with the occurrence of progressive glaucomatous damage and was the principal factor affecting the successful outcome in our patients.

An important observation in our group of patients was the early onset of glaucoma. Open angle glaucoma presented in the first 50 years of life in 35.6% of patients, of whom 21% presented before 40 years of life. While in angle closure glaucoma, 46.5% were younger than 50 years of age when they had glaucoma diagnosed for the first time. Our study also showed a high proportion of females in the angle closure glaucoma (almost 2/3 of the total cases) in agreement with other reports (16-18).

An important observation was the presence of a significant proportion of patients who were legally blind due to glaucoma of both varieties when they presented for the first time. Patients who were termed legally blind in this study were defined according to American Academy of Ophthalmology as having visual acuity of 20/200 or less in better eye with best correction and or a visual field constriction to 20 degree or less.The results of distribution of these patients are shown in Tables 3-5. There is a reasonable match between the subjective findings as assessed by patient visual function and objective findings as assessed ophthalmoscopically by cup/disc ratio. For example, for C/D ratio of 1.0-0.8 there were 37% of eyes with POAG and 45.3% in PACG which matched eyes with legal blindness (6/60 or less), 21.7% in POAG compared to 25.3% in PACG or with gross visual fields (categories 4-5) 28.1% in POAG compared to 35.2% in PACG.

Unfortunately this study was hospital based and little conclusion can be drawn as regard epidemiology of glaucoma in Qatar, its true incidence or prevalence . However, we believe that this study described faithfully glaucoma presentation and its severity and problems associated with its management. We think that this paper addresses for the first time the significant magnitude of the glaucoma problem amongst Qatari patients.

Several conclusions can be drawn from the study. Firstly, glaucoma of both types can be present at an early age in Qataris. Secondly, glaucoma is responsible for a substantial amount of visual loss even at the time of presentation. Thirdly, there is significant amount of poor compliance amongst patients with glaucoma, making the management more difficult.

Therefore we recommend the need for wide-scale health education on a national level. We also recommend screening and early detection of glaucoma with help of general practitioners, family doctors, optometrists and ophthalmologists in order to minimize the magnitude of blindness from glaucoma.

References:

1. Shaffer RN. III Symposium: Office management of the primary glaucomas. Gonioscopy, ophthalmoscopy and perimetry. Trans Am Acad Ophthalmol Otolaryngol. 64, 112-27, 1960.

2. Stewart Wc, Chorak RP, Hunt HH, Sethuraman G: Factors assiciated with visual loss in patients with advanced Glaucomatous changes in the optic nerve head. Am. J. Ophthalmol. 116: 176 - 181, 1993.

3. Leske MC: The epidemiology of open angle glaucoma: A review. Am J Epidemiol. 118: 166 - 191, 1983.

4. Quigley HA: Number of people with glaucoma worldwide. Br J Ophthalmol. 80: 389-393, 1996.

5. Hiller R, Kahn HA. Blindness from glaucoma. Am J Ophthalmol. 80: 62-9, 1975.

6. Leibowitz Hm, Krneger DG, Munder LR etal. The framingham eye study. Surv Ophthalmol. 24; 335 - 610, 1980.

7. Ghafour IM, Allan D, Foulds W. Common Causes of blindness and visual handicap in the west of Scotland. Br J Ophthalmol. 67: 209-13, 1983.

8. Tielsch JM, Sommer A, Witt K, Katz J, Royall RM. Blindness and visual impairment in American Urban population. Arch Ophthalmol. 108: 286-90, 1990.

9. Coffey M, Reidy A, Wormald R, WuXX, Wright L, Courtney P. Prevalence of Glaucoma in the west of Ireland. Br J Ophthalmol; 77: 17-21, 1993.

10. Shin DH, Beck B, Kolker AE: Family history in primary open angle glaucoma. Arch Ophthalmol 95; 598, 1977.

11. Kass MA, Palmberg P, Becker, et al: Histocompatibility antigens and Primary Open Glaucoma: A reassessment Arch Ophthalmol 96; 2207, 1978.

12. Tielsch JM, Katz J, Sommer A, Quigly H, et al: Family history and risk of Primary Open angle glaucoma. Arch Ophthalmol; 112, 69-73, 1994.

13. Booth A, Churchill A, Anwar R, Menage M, Markham A: The genetics of Primary open angle glaucoma. Br. J. Ophthalmol; 81: 409-414, 1997.

14. Kass, M.A: Compliance and prognosis in glaucoma. Arch. Ophthalmol. 103: 504, 1985. 15. Granström, P.A.: Progression of visual field defects in glaucoma. Relation to compliance with pilocarpine therapy. Arch. Ophthalmol. 103: 529, 1985.

16. Kurland L.T, Tauf RC. The frequency of glaucoma in a small Urban Community. AMJ Ophthalmol. 43: 539, 1957.

17. Bonomi L, Marchini G, Marraffa M, Bernardi P, Defranco I, Perfetti S, Varotto A, Tenna V. Prevalence of glaucoma and intraocular pressure distribution in a defined population. The Enga-Newmarkt study. Ophthalmology, 105: 209, 1998.

18. Bengtsson B. The prevalence of Glaucoma. Br J Ophthalmol. 65: 46-9, 1981.