Journals 
Present Issue 
Past Issues 
 

THESMANEWS 
Present Issue 
Past Issues 
 

SMJ Editorial Board 

Letters to the Editor 

ABSTRACT 

Purpose: Data is lacking with regard to the factors which may predict the outcome of an acute glaucoma eye to treatment and its long-term prognosis. This study was carried out to identify such factors, in particular among Singaporeans. 
Methods: Fifty-seven eyes were included in this retrospective analysis and factors analysed included age and sex; the duration of onset of symptoms to the time they presented to hospital; state of pupil and presenting intraocular pressure (IOP); whether attack is terminated by medical treatment alone or a second procedure (eg laser, trabeculectomy) was required; final outcome with respect to the development of chronic angle closure glaucoma and state of pupil at last follow-up. 
Results: Patients with 24 to 72 hours' delay in presentation had a relative risk of 2.78 (CI=1.03-7.46) in developing chronic glaucoma. Those who required the addition of a laser procedure to control the initial presenting IOP while those who proceeded to a trabeculectomy had relative risks of 3.63 (CI=1.49-8.89) and 4.83 (CI=1.18-19.7) respectively in developing chronic glaucoma when compared to patients who did not require any secondary treatment. 
Conclusion: Delay in presentation, and unresponsiveness to medical treatment in termination of the acute attack in an acute angle closure glaucoma patient carry a significant risk of chronic glaucoma. 
Keywords: angle-closure glaucoma, laser peripheral iridotomy, prognosis 

INTRODUCTION 
Laser procedures such as laser peripheral iridotomy (PI) or argon laser peripheral iridoplasty (ALPI), are the effective and definitive treatment in primary acute angle-closure glaucoma(AACG) (1-4). In order to perform laser iridotomy safely and satisfactorily, the intra-ocular pressure (IOP) in the eye with an acute attack must be lowered with medical therapy in order to clear the cornea oedema. Frequently, this is achievable with medical treatment alone, or in combination with laser procedures, thus avoiding the need for surgical intervention in order to abort the attack. Data is lacking with regard to the factors which may predict the responsiveness of an acute glaucoma eye to medical treatment, and those in which a secondary procedure is necessary to terminate an acute attack. Moreover, there are conflicting studies in the literature on factors affecting the outcome of patients with AACG(2,3,5,6). Few, if any, of these analyses were done on Oriental population(1-3,5,6) in general, and among Singaporeans in particular. 
The high prevalence of AACG in this country(7) provides us an opportunity to examine the 
1.  outcome of patients with AACG with respect to response to initial treatment 
2.  risk-factors, if any, that are predictive of unresponsiveness to medical treatment 
3.  long-term outcome with respect to development of chronic angle glaucoma in AACG patients who had PI 
4.  factors affecting the long-term outcome in these patients. 
 
PATIENTS AND METHODS 
A retrospective study of all patients presenting to the National University Hospital with AACG in the years 1990 and 1991 (January 1990 to December 1991) was undertaken. Secondary causes of acute-angle closure glaucoma such as intumescent lens, neovascular glaucoma etc, were excluded from the study. All patients with AACG were treated with guttae pilocarpine 2%-4% q15 minutes in the first hour following diagnosis, thereafter qds; guttae timolol 0.5% bd; and i.v. acetazolamide 250-500 mg stat depending on patient's weight, followed by 250 mg orally qds. Laser PI (Argon blue-green at 1.0W to l.5W, 50 micron spot size, 0.08 second exposure; followed by Nd-YAG laser at 1.2mJ to 2.4 mJ) was performed once the IOP is lowered and/or the cornea is clear. In instances that were unresponsive to medical therapy where the cornea remained hazy or anterior chamber was too shallow for laser PI to be performed safely, argon laser peripheral iridoplasty were performed. This was then followed by laser PI once the cornea was clear and anterior chamber was deeper. A prophylactic laser PI was routinely performed in the fellow eye. 
A total of 50 case-records representing 57 affected eyes were retrieved and the following data recorded: (1) age, race and sex; (2) the duration of onset of symptoms to the time they presented to the Eye Department; (3) state of pupil and presenting IOP; (4) whether attack is terminated by medical treatment alone or a second procedure was needed (eg PI, ALPI, trabeculectomy); (5) time taken for the attack to be terminated (ie IOP drops to below 21mmHg) after initiation of treatment; (6) final outcome with respect to the development of chronic angle-closure glaucoma, ie IOP>21 without any further medical or surgical intervention at the last follow-up; (7) state of pupil at last visit. 
Statistical evaluation was performed using the computer program DEPID running on Microsoft DOS. 

RESULTS 
Fifty-seven eyes from 50 patients were included in the study. Seven patients had simultaneous bilateral AACG attack; all the patients presented to the Eye Department within 1 week after the beginning of symptoms. There were 40 females in the sample, outnumbering males by 3:1. The mean age was 65 years (range 40 to 89 years). The mean duration of follow-up was 20 months, with follow-up rate of 82%, 65% and 61% at 3-6 months, and 1 year respectively. The average presenting pressure was 56 mmHg (SD 13.6; range 24 to 80 mmHg). Ninety-three percent of patients had the presenting IOP lowered to less than 21 mmHg within 24 hours of initiation of treatment while in the remainder, the acute attack was terminated within 3 days. The mean post treatment IOP was 11.7 mmHg (SD 4.2; range 5-19). Table I summarises the acute attack treatment response of this study population. 
There were no recurrence of AACG noted in the same eye after successful treatment, and no AACG attack in the fellow eyes were recorded. 

Factors affecting successful method of treatment of acute attack 
Selected characteristics were analysed to predict if the acute attack would be aborted with medical treatment alone, and what factors would put the patient at risk for an addition of a secondary procedure before the IOP could be lowered to less than 21 mmHg. From Table II, it could be seen that characteristics such as age, sex of patient, duration of symptoms before initiation of treatment, and height of presenting IOP have no predictive effect as to who would respond to medical treatment alone. 

Factors affecting the development of chronic glaucoma 
A total of 16 patients developed chronic glaucoma on follow-up. Analysis of patient data revealed a few important factors that have significant correlation with the eventual development of chronic glaucoma. Firstly, patients with more than 24 hours delay in presentation had an unfavourable outcome; those who waited for 24 to 72 hours before presenting to us had a relative risk of 2.78 (CI=1.03-7.46) in developing chronic glaucoma later. 
Secondly, patients whose initial presenting IOP was unable to be lowered to <21 mmHg with medical treatment alone had an increased risk for chronic glaucoma. Those who required the addition of a laser procedure to control the initial presenting IOP had a relative risk of 3.63 (CI=1.49-8.89); while those who proceeded to a trabeculectomy had a risk of 4.83 (CI= 1.18-19.7) when compared to patients who did not require any secondary treatment to control initial high IOP. Other factors such as age, sex of patient, state of pupil and height of presenting IOP had no effect on the final outcome. 

DISCUSSION 
Acute angle-closure glaucoma is essentially an affliction of the elderly and females are at higher risk. In this study, it is evident that most acute attacks (95%) can be treated successfully (IOP < 22 mmHg) with medical therapy alone or combined with a laser procedure, thus obviating the need for invasive surgical intervention. Laser PI was performed when the cornea was clear and ALPI was done in instances that was unresponsive to medical therapy where the cornea remained hazy or anterior chamber was too shallow for laser PI to be performed safely. Thereafter, laser PI were performed in such cases when the cornea cleared or the anterior chamber deepened. In only 3 cases, an acute attack could not be aborted with medical therapy alone or in combination with laser procedures, thus necessitating a primary surgical intervention (trabeculectomy) to control the IOP. In practice, this translates into better economy and greater safety as anaesthesia risks, operating theatre costs and time, and need for operating theatre staff's assistance could be avoided. None of the patients had any recurrent attack in the same eye after treatment for initial attack, and none of the fellow eyes had an AACG attack. 
In this analysis, there were no factors that may predict which eyes were at risks for an additional secondary procedure in order to terminate the acute attack. It appears that the reversibility of pupillary block, extent of trabecular meshwork damage, or formation of anterior synechiae in AACG is not related to the height, nor the duration of raised IOP. It is possible that there are putative factors which determine if an attack could be terminated by medical treatment alone or those who, in addition, would require a secondary intervention such as a laser procedure or a primary filtering surgery to control the height of IOP. However, the number of patients who required surgery is so small (n=3) that the analysis for predictive factors would be lacking in statistical power. 
In contrast to short term outcome, patients who had a delay in the initiation of treatment had a poorer long term prognosis. This is in agreement with other reports which found significant risks of chronic glaucoma if there had been a delay of more than 24 hours from the start of symptoms to initiation of treatment(2,5). Our study revealed a 2.8 fold increase in risk for chronic glaucoma if there had been a delay for 24 to 72 hours. A similar increased risk is noted for those who had more than 72 hours delay in presentation but this is not statistically significant at 95% confidence level (RR=2.84, CI= 0.94-8.57). Although the exact mechanism for this late rise in pressure is unknown, various hypotheses had been proposed to account for the late rise in pressure which include the importance of time factor in the development of peripheral anterior synechiae, trabecular meshwork damage, pigment dispersion from iris atrophy, etc (2,5). 
Patients who required an additional laser procedure or trabeculectomy in order to terminate the acute attack had significantly increased risks for chronic glaucoma (RR=3.63 and 4.83 respectively). It is possible that in this group of patients, the same factors that determined their unresponsiveness to medical treatment alone, are also responsible for the development of chronic glaucoma. It is interesting to note that there is a suggestion of a positive correlation between the dilated state of pupil at last follow-up (which could be a reflection of severity of the attack) and the risk of chronic glaucoma, although this is not significant at 95% confidence level. (RR=2.50, CI= 0.92-6.79). 
Of the 16 cases who had chronic glaucoma on follow-up, 15 cases developed glaucoma within the first 5 months after AACG, while the remainder developed chronic glaucoma within three years after initial acute glaucoma. This is in agreement with other reports that most patients who would develop chronic glaucoma, occur within 4 months to one year after the initial attack (2,5,6). 
In summary, we have shown that delay in presentation, and unresponsiveness to medical treatment in termination of the acute attack in an AACG patient carry a significant risk of chronic glaucoma. Periodic follow-ups are recommended for this group of patients who are at risk. However, most patients would do well if they had not developed chronic angle-closure glaucoma six months after the acute attack. 
 

Table III - Association of selected single factor characteristics and risk of chronic
                 glaucoma.