Access to the PDF text
Service d'aide à la décision clinique

Free Article !

Journal Français d'Ophtalmologie
Volume 40, n° 9
pages 770-776 (novembre 2017)
Doi : 10.1016/j.jfo.2017.04.012
Received : 8 February 2017 ;  accepted : 26 April 2017
Ahmed glaucoma valve in various etiologies of refractory glaucoma: Surgical outcomes and success factors
Résultats à moyen terme de l’implantation de la valve d’Ahmed dans différentes étiologies de glaucome réfractaire

M.A. Sahyoun a, c, , R.G. Farhat a, c, J.C.B. Nehme a, c, A.E. Jalkh a, b, c, G.G. Azar a, b, c
a Holy Spirit University of Kaslik, Kaslik, Lebanon 
b Saint Joseph University, Beirut, Lebanon 
c Eye and Ear University Hospital, Naccache, Lebanon 

Corresponding author.

To study the epidemiology and mid-term results of the Ahmed glaucoma valve (AGV) in various etiologies of refractory glaucoma in a Lebanese center, and to assess complications and factors that influence the surgical success rate.


In this retrospective epidemiological study, we reviewed 108 eyes with refractory glaucoma that underwent an AGV implantation in a tertiary care center in Lebanon between January 2002 and August 2014. Findings including best-corrected visual acuity (BCVA), intra-ocular pressure (IOP), number of antiglaucoma medications, factors influencing the surgical outcome, success rate and complications were also reviewed.


The mean duration of follow-up was 29.85±21.45 months [range, 3–60 months]. As in other Arab countries and compared to the rest of the world, the rate of neovascular glaucoma (NVG) was particularly high, occurring in 63 eyes (58.3%), and represented the primary cause of refractory glaucoma. Mean IOP was significantly reduced to 17.97±7.35mmHg at the last follow-up visit (P <0.05). Similarly, a significant decrease was noted in the number of antiglaucoma medications (P <0.05). The surgical success rate, defined as a postoperative IOP<21, was significantly higher (62.0%), in older patients, those with baseline BCVA2 LogMAR and those with a history of hypertension (P <0.01). Hyphema was the most noted complication.


The AGV is a safe and effective procedure for lowering IOP in refractory glaucoma patients, with hyphema being the most frequent complication. Both the presence of hyperstension and initial BCVA2 LogMAR seem to increase the success rate of the procedure. NVG remains the most common etiology for implantation, probably due to uncontrolled diabetes in the Middle East and North Africa.

The full text of this article is available in PDF format.

Étudier l’épidémiologie et les résultats à moyen terme de la valve d’Ahmed (VA) dans différentes étiologies de glaucome réfractaire et évaluer les complications ainsi que les facteurs pouvant influencer le taux de succès chirurgical.


Il s’agit d’une étude épidémiologique rétrospective. Cent huit yeux atteints de glaucome réfractaire ont subi une implantation de VA dans un centre hospitalier tertiaire au Liban entre janvier 2002 et août 2014. La meilleure acuité visuelle corrigée (MAVC), la pression intraoculaire (PIO), le nombre de médicaments antiglaucomateux, ainsi que les complications et les facteurs pouvant exercer une influence sur le taux de succès chirurgical ont été évalués.


La durée moyenne du suivi était de 29,85±21,45 mois (marge, 3–60 mois). Le taux de glaucome réfractaire lié au glaucome néovasculaire (GNV) était particulièrement élevé (58,3 %), ce qui corrélait avec l’épidémiologie des études faites dans les pays Arabes de voisinage. La PIO moyenne a été significativement réduite à 17,97±7,35mmHg lors de la dernière visite (p <0,05). De même, une diminution significative du nombre de médicaments antiglaucomateux a été notée (p <0,05). Le taux de réussite chirurgicale, définie par une PIO postopératoire<21mmHg, était significativement plus élevé (62,0 %) chez les patients âgés, hypertendus et ceux ayant été opérés avec une MAVC de base2 LogMAR (p <0,01). La complication la plus fréquente était l’hyphéma.


La VA est une procédure sûre et efficace pour réduire la PIO chez les patients glaucomateux réfractaires. L’hypertension artérielle et une MAVC de base2 LogMAR semblent augmenter le taux de réussite chirurgicale. Le GNV reste l’étiologie la plus fréquente probablement à cause du diabète mal contrôlé dans la région du Moyen-Orient et d’Afrique du Nord.

The full text of this article is available in PDF format.

Keywords : Ahmed glaucoma valve, AGV, Efficacy, Epidemiology, Neovascular glaucoma, Refractory glaucoma, Diabetic retinopathy

Mots clés : Valve d’Ahmed, Efficacité, Épidémiologie, Glaucome néovasculaire, Glaucome réfractaire, Rétinopathie diabétique


The Ahmed glaucoma valve (AGV, New World Medical, Inc., Rancho Cucamonga, California, USA) was implanted for the first time in 1993 for patients with high intra-ocular pressure (IOP) that had not responded to medical treatment, laser photocoagulation, or previous glaucoma surgery [1]. Its effectiveness in lowering IOP and reducing number of last visit antiglaucoma medications has since then been established in many studies, and overall reported success rates varied between 54% and 78.7%% at 4 years [2, 3, 4].

To prevent excessive aqueous drainage and anterior chamber collapse, the AGV has an autoregulated non-obstructive valvular system that is formed by silicone elastomer membranes held in a polypropylene or silicone body [2]. However, tube insertion is a delicate procedure and a number of complications have been reported following surgery, such as tube blockage, retraction, exposure and malposition, as well as more serious complications such as hypotony, hyphema, choroidal detachment and corneal endothelium decompensation with longer follow-ups [2, 3, 5, 6].

Very few studies have been conducted in the Arab population concerning this type of implants. One study was held in Tunis [4] in 2007 and another one in Kuwait [7] in 2012. More recently, Shah et al. [6] followed 40 eyes that underwent an AGV implantation in Oman over a period of 3 months (mo). While the three studies yielded almost comparable results, they were all limited by a small number of participants and a relatively short follow-up period.

The aim of this retrospective study was first to describe the epidemiology of patients with refractory glaucoma that needed an AGV implantation in our center in Lebanon. Once established, the mid-term results of the surgery on IOP, best-corrected visual acuity (BCVA) and the number of antiglaucoma medications were studied. A final objective was to assess the valve's complications, and to evaluate the putative factors that may influence its surgical success rate.

Material and methods
Inclusion and exclusion criteria

This retrospective epidemiological study collected the records of patients admitted to our ophthalmology department for AGV implantation between January 2002 and August 2014. All patients with a follow-up period of at least 3 months were included in the study, regardless of their glaucoma etiology. The AGV was implanted for refractory glaucomatous patients with high IOP not responding to maximal medical therapy, and for patients in whom filtering surgery was unlikely to be successful because of factors such as uveitis, a previous failed filtering surgery or aphakia. The study was approved by the hospital's institutional review board and adhered to the tenets of the Declaration of Helsinki.

Although the follow-up information of patients operated in the early part of the study was of long duration, collection of data was withheld after 5 years. Nine patients underwent bilateral implantation, in which data were collected for both eyes separately. A total of 108 eyes of 99 patients were therefore included in the study.

Exclusion criteria were the use of earlier cyclodestructive procedures or drainage implants and a follow-up duration of less than 3 months.

Surgical procedure

All patients were under maximal medical therapy before surgery, except in cases of major contra-indications or allergies. The surgery was performed by 2 physicians (AJ and GA) using the same technique.

After administration of regional or general anesthesia, a conjunctival flap was first created in the superotemporal quadrant, in which the AGV was inserted and sutured 8–10mm away from the limbus using 9–0 monofilament nylon sutures. A 23-gauge needle was used to enter the anterior chamber through the limbus, and then the tube edge was cut obliquely and inserted (bevel facing upward) through the track, 3mm within the anterior chamber. After fixation with 10-0 monofilament sutures, the tube was covered with a small piece of donor sclera. The conjunctiva and Tenon capsule were reapproximated to the limbus using 8.0 vicryl sutures, and subconjunctival steroids and antibiotics were injected at the end of the procedure. Postoperatively, patients were discharged on topical antibiotics and prednisolone acetate 1% four times per day.

Data collection

Demographic and epidemiological characteristics were inquired from patient's records and operation log books: age at the time of implantation, gender, medical history such as the presence of high blood pressure (HBP) or diabetes mellitus (DM), type of glaucoma, affected eye, number of antiglaucoma medications, follow-up duration, lens status, history of a previous trabeculectomy, the need for valve revision or re-implantation, location of the AGV tube insertion (anterior chamber versus pars plana) and postoperative complications.

Preoperatively, all patients had their BCVA assessed on a three-meter Snellen's chart, which was then converted to the logMAR unit in order to allow for statistical analysis. IOP was measured by Goldmann tonometer. A detailed fundus exam was also performed.

The follow-up assessments were noted for IOP (when available) at day 1, day 7, 1 mo, 3 mo, 6 mo, 1 year and then every 6 months. BCVA and number of antiglaucoma medications were reported at 3 mo, 6 mo, 1 year and then annually.

During follow-up, antiglaucoma medications were reintroduced when the IOP exceeded 21mmHg. Hypotony was defined as an IOP5mmHg at 2 consecutive visits.

Surgical success was defined as an IOP of 6mmHg or greater and 21mmHg or less, with or without the use of additional antiglaucoma medications and without loss of light perception (LP). Surgical failure was defined as an IOP<5mmHg or>21mmHg under maximal medical therapy at two consecutive follow-up visits, a deterioration of the BCVA with loss of LP, or the need for further glaucoma surgical interventions.

Statistical analysis

Statistical analysis was performed using IBM SPSS 22.0 (SPSS Inc., Chicago, IL, USA), and graphics were done using GraphPad Prism 6. The results were expressed as means±standard deviation (SD), and percentages with confidence intervals of 95%. Qualitative data were compared using Chi2 and Fisher's exact test, and quantitative data using independent-samples t test and paired-samples t test. The cumulative probability of success was analyzed by the Kaplan-Meier method. Differences with P -values<0.05 were considered statistically significant.


A total of 108 eyes (99 patients) were included in the study. Their demographic and baseline characteristics are summarized in Table 1. The mean age of patients was 61.71±17.50 years [range, 2–86 years], with a mean follow-up period of 29.85±21.45 mo [range, 3–60 mo]. 36 patients (33.3%) were women. Preoperatively, 65 eyes (60.2%) were pseudo-phakic and 5 eyes (4.6%) were aphakic. Twenty-eight eyes (25.9%) had undergone a previous trabeculectomy. DM was found in 62 eyes (55 patients, 57.4%) and HBP in 28 eyes (26 patients, 25.9%). The tube was inserted through pars plana into the posterior chamber in 12 eyes (11.1%) presenting a refractory glaucoma with either secondary angle closure or angle neovascularization, corneal diseases, or any other anterior chamber abnormalities.

The most common refractory glaucoma etiologies were respectively NVG in 63 eyes (58.3%), pseudophakic glaucoma in 14 eyes (13.0%), traumatic glaucoma in 10 eyes (9.3%), primary open-angle glaucoma (POAG) in 8 eyes (7.4%) and others in 13 eyes (12.0%).

The mean IOP, BCVA and number of antiglaucoma medications preoperatively and at different follow-up visits are shown in Figure 1. IOP was significantly reduced from a baseline of 38.76±11.50mmHg to 17.97±7.35mmHg at last follow up visit (P <0.05). The number of medications was also significantly reduced (2.31±0.81 and 1.35±0.97 at first and last visit, respectively; P <0.05). However, a significant deterioration of the BCVA was observed, with an increase of mean logMAR from 1.99±0.98 to 2.29±1.11 (P <0.05).

Figure 1

Figure 1. 

Mean intra-ocular pressure (IOP), number of antiglaucoma medications and best-corrected visual acuity (BCVA) after insertion of the Ahmed glaucoma valve over the study period. The numbers between brackets correspond to the number of patients available for follow-up at each time point.


No major intraoperative complications of AGV implantation were reported. Postoperative complications were assessed throughout the follow-up and were as follows (Table 2). Mild to moderate hyphema was the most common postoperative complication occurring in 19 eyes (17.6%), 18 of which had NVG. Tube exposure was seen in 14 eyes (13.0%), followed by a fibrinous reaction in 11 eyes (10.2%), tube blockage in 9 eyes (8.3%) and corneal decompensation in 9 eyes (8.3%). In one eye, fibrinous ingrowth occurred over the intraocular lens occluding the intracorneal portion of the tube shunt and required treatment by Nd:YAG Laser.

The cumulative probability of success of the valve as per Kaplan–Meier life-table analysis (Figure 2) was 62.0% at 5 years. Twenty-one eyes (19.4%) required further glaucoma surgeries, 12 eyes (11.1%) were considered a failure because of high IOP (≥21mmHg at 2 consecutive follow-up visits despite maximal medical therapy) and 12 eyes (11.1%) had loss of LP. No cases of hypotony were noted. A percentage of 82.1 of eyes presenting HBP and 70.3% of those with an initial BCVA2 LogMAR were a success (Table 3). Both these findings were statistically significant when compared to eyes with no history of HBP and those with an initial BCVA worse than 2 logMAR (P <0.05 and P <0.05, respectively). A history of DM, previous trabeculectomy or cataract surgery, were not associated with a higher risk of failure (P =0.35, P =0.31 and P =0.61, respectively).

Figure 2

Figure 2. 

Cumulative probability of success after Ahmed glaucoma valve implantation. The cumulative probability of success of the valve as per Kaplan–Meier life-table analysis was 62.0% at 5 years.



The epidemiology of refractory glaucoma in the Middle East is yet to be established. While POAG predominates over primary angle closure glaucoma (PACG) in Asia in a recent systematic review and meta-analysis [8], other studies found POAG to be most prevalent in Africa and PACG in Asia [9]. Due to the increasing incidence of DM worldwide and in Lebanon particularly, it is expected that NVG would be the most frequent etiology of refractory glaucoma in the country. This study tries to estimate the prevalence and epidemiology of refractory glaucoma and the result of its treatment with AGV implantation.

NVG was found to be the most common etiology of refractory glaucoma in our center in Lebanon, occurring in 58.3% of the eyes included in our study. Similar results were found in two other Arab countries. One study was held in Kuwait [7] in 2012 and another one in Oman [6] in 2013; in both these studies, NVG was the most common preoperative diagnosis (42.4% and 57.7% in Kuwait and Oman, respectively). In Tunis [4], the most common etiology of refractory glaucoma was POAG (48.1%) followed by NVG (29.6%). When compared to the rest of the world, the percentage of NVG came second in Taiwan [10] (24.2%), third in Los Angeles [11] (21.8%), and dropped as low as 4.0% in Kenya [12] and 3.2% in England [2]. NVG is therefore much more frequent in the Arab world, and represent the most common cause of refractory glaucoma requiring the implantation of an AGV.

One possible explanation could be the inadequate control of diabetes and glycated hemoglobin (HbA1c) in the region. In fact, according to the International diabetes federation (IDF), the prevalence of diabetes in the Middle East and North Africa (MENA) in 2015 is one of the highest worldwide (9.1%) with 35.4 million people living with diabetes, 40.6% of whom are undiagnosed (Diabetes Atlas; available online on diabetesatlas; updated 2015). Consequently, four out of 10 adults with diabetes will have their glycemic levels inadequately controlled, which will increase their risk of developing NVG.

Postoperatively, 19 eyes (17.6%) developed hyphema. This complication rate was the highest in our study, and was seen in 18 eyes with NVG. Hyphema was also the most common complication observed in Oman [6] (15.0%) and Tunis [4] (14.8%), and the second most common complication in Kuwait [7] (18.0%). Even though NVG was not as prevalent in other countries, rates of hyphema were relatively high, and varied between 11.5% in Los Angeles [11], 12.8% in China [10] and 15.4% in Turkey [3].

As for the IOP control and number antiglaucoma medications, Shah et al. [6] demonstrated a 23.8mmHg decline in IOP at 12 weeks following AGV implant. Moreover, in their study, Aljazzaf et al. [7] were able to decrease IOP from a baseline of 37.0±12.1mmHg to 18.0±14.1mmHg at 1 year postoperatively. These results were similar to other reports showing a decreased IOP to 13–17mmHg at 1 year [4, 13, 14, 15]. The 5-year treatment outcomes of the Ahmed versus Baerveldt study [16] showed a 47% reduction of mean initial IOP at 5 years. In our study, a significant drop in IOP and number of antiglaucoma medications was also noted throughout the follow-up and until the last follow-up visit (P <0.05 and P <0.05, respectively) with no postoperative hypertensive phase.

Despite adequate IOP control, BCVA deteriorated from a baseline mean of 1.99±0.98 logMAR to 2.29±1.11 logMAR at last follow-up visit (P <0.05). This is probably due to the fact that most of the patients included were diagnosed having NVG (58.3%), which is a particularly severe type of glaucoma, essentially characterized by its poor visual prognosis [17, 18]. Similarly, in Kuwait [7] where NVG was also the leading cause of refractory glaucoma, a deterioration of the BCVA was seen in 27% of the patients, and 64% had their BCVA unchanged. However, in Oman [6], BCVA was improved in patients with an initial vision better than 3/60.

The success rate of AGV implantation varies between 54.0% and 78.7% [1, 2, 3, 4] in the literature. In our study, the valve's overall success rate was found to be 62.0% at 5 years and seemed to be influenced by three factors: older age>60 years, initial BCVA2 LogMAR and the presence of HBP. In fact, more than half of the patients (55.3%) who were younger than 60 years at the time of implantation were a failure, as opposed to 28.6% of the older ones. This can be explained by the fact that, with age, the overall size, function and number of fibroblasts in the body decrease [19], which will affect the extracellular matrix structures including collagen, elastin and proteoglycans, and prohibit conjunctival fibrosis. A percentage of 70.3 of the patients with an initial BCVA2 LogMAR were found to be a success, and only 29.7% were a failure (P <0.05). Therefore, for better surgical success, AGV seems to be recommended for BCVA at counting fingers or better. On the other hand, 82.1% of the patients who initially presented with HBP were a success compared to 17.9% who were considered a failure (P <0.05). One possible theory could be that HBP increases the production of the aqueous humor [20], which in return will increase the hydrostatic pressure and the flow through the valve, leading to less obstruction. Another finding that is worth mentioning, is that certain types of glaucoma seemed to respond better than others. In fact, 8 out of 8 POAG patients (100%) had a successful surgery while 27 out of 63 NVG (42.9%) were a failure. However, due to the discrepancy in subgroups sizes, statistical analysis was impossible to make.

Therefore, our study has some limitations, mainly because of its retrospective design. The percentage proportion was very low for certain glaucoma subtypes (1 case of uveitic glaucoma and 1 case of chronic angle closure glaucoma) and made statistical analysis impossible for these groups. Missing data and loss of follow-up were also major limitations, with only 26 eyes (24.1%) reaching the 5 years’ time point, probably due to the severe visual prognosis of NVG and its associated comorbidities. Further prospective studies that take these limitations into consideration are therefore needed in order to generalize our findings.

In conclusion, the AGV appears to be a safe and effective procedure for lowering IOP and number of antiglaucoma medications. Both HBP and an initial BCVA2 LogMAR seem to improve the valve's surgical success rate. In the Arab world, NVG is the leading cause of refractory glaucoma, probably due to the high incidence of uncontrolled diabetes. Finally, hyphema is the most common postoperative complication observed, particularly in NVG patients.

Disclosure of interest

The authors declare that they have no competing interest.

 Oral communication presented at the 121th Congress of the French society of ophthalmology in May 2015.


Coleman A.L., Hill R., Wilson M.R., Choplin N., Kotas-Neumann R., Tam M., and al. Initial clinical experience with the Ahmed glaucoma valve implant Am J Ophthalmol 1995 ;  120 : 23-31 [cross-ref]
Wishart P.K., Choudhary A., Wong D. Ahmed glaucoma valves in refractory glaucoma: a 7-year audit Br J Ophthalmol 2010 ;  94 : 1174-1179 [cross-ref]
Kaya M., Ozbek Z., Yaman A., Durak I. Long-term success of Ahmed glaucoma valve in refractory glaucoma Int J Ophthalmol 2012 ;  5 : 108-112
El Afrit M.A., Trojet S., Mazlout H., Hamdouni M., Kraiem A. Efficacy of the Ahmed glaucoma valve implant in eyes with refractory glaucoma Tunis Med 2007 ;  85 : 941-944
Minckler D.S., Francis B.A., Hodapp E.A., Jampel H.D., Lin S.C., Samples J.R., and al. Aqueous shunts in glaucoma: a report by the American academy of ophthalmology Ophthalmology 2008 ;  115 : 1089-1098 [cross-ref]
Shah M.R., Khandekar R.B., Zutshi R., Mahrooqi R. Short term outcome of Ahmed glaucoma valve implantation in management of refractory glaucoma in a tertiary hospital in Oman Oman J Ophthalmol 2013 ;  6 : 27-32
Aljazzaf A.M., Abdelmoaty S.M.A., Behbehani A.H., Abdulmuez A.A., Aljazzaf H.A. The outcome of the Ahmad Glaucoma Valve implantation for refractory glaucoma in Kuwait Saudi J Ophthalmol 2013 ;  27 : 15-18 [cross-ref]
Chan E.W., Li X., Tham Y.-C., Liao J., Wong T.Y., Aung T., and al. Glaucoma in Asia: regional prevalence variations and future projections Br J Ophthalmol 2016 ;  100 : 78-85 [cross-ref]
Tham Y.-C., Li X., Wong T.Y., Quigley H.A., Aung T., Cheng C.-Y. Global prevalence of glaucoma and projections of glaucoma burden through 2040: a systematic review and meta-analysis Ophthalmology 2014 ;  121 : 2081-2090 [cross-ref]
Tai M.-C., Cheng J.-H., Chen J.-T., Liang C.-M., Lu D.-W. Intermediate outcomes of Ahmed glaucoma valve surgery in Asian patients with intractable glaucoma Eye Lond Engl 2010 ;  24 : 547-552 [cross-ref]
Souza C., Tran D.H., Loman J., Law S.K., Coleman A.L., Caprioli J. Long-term outcomes of Ahmed glaucoma valve implantation in refractory glaucomas Am J Ophthalmol 2007 ;  144 : 893-900 [inter-ref]
Kiage D.O., Gradin D., Gichuhi S., Damji K.F. Ahmed glaucoma valve implant: experience in East Africa Middle East Afr J Ophthalmol 2009 ;  16 : 151-155 [cross-ref]
Ayyala R.S., Zurakowski D., Smith J.A., Monshizadeh R., Netland P.A., Richards D.W., and al. A clinical study of the Ahmed glaucoma valve implant in advanced glaucoma Ophthalmology 1998 ;  105 : 1968-1976 [cross-ref]
Wilson M.R., Mendis U., Smith S.D., Paliwal A. Ahmed glaucoma valve implant vs trabeculectomy in the surgical treatment of glaucoma: a randomized clinical trial Am J Ophthalmol 2000 ;  130 : 267-273 [inter-ref]
Huang M.C., Netland P.A., Coleman A.L., Siegner S.W., Moster M.R., Hill R.A. Intermediate-term clinical experience with the Ahmed glaucoma valve implant Am J Ophthalmol 1999 ;  127 : 27-33 [inter-ref]
Christakis P.G., Kalenak J.W., Tsai J.C., Zurakowski D., Kammer J.A., Harasymowycz P.J., and al. The Ahmed versus Baerveldt study: 5-year treatment outcomes Ophthalmology 2016 ;  123 : 2093-2102 [cross-ref]
Olmos L.C., Lee R.K. Medical and surgical treatment of neovascular glaucoma Int Ophthalmol Clin 2011 ;  51 : 27-36 [cross-ref]
Horsley M.B., Kahook M.Y. Anti-VEGF therapy for glaucoma Curr Opin Ophthalmol 2010 ;  21 : 112-117 [cross-ref]
Gunin A.G., Kornilova N.K., Petrov V.V., Vasil’eva O.V. Age-related changes in the number and proliferation of fibroblasts in the human skin Adv Gerontol Uspekhi Gerontol 2011 ;  24 : 43-47
Shiose Y. The aging effect on intraocular pressure in an apparently normal population Arch Ophthalmol Chic Ill 1960 1984 ;  102 : 883-887

© 2017  Elsevier Masson SAS. All Rights Reserved.
EM-CONSULTE.COM is registrered at the CNIL, déclaration n° 1286925.
As per the Law relating to information storage and personal integrity, you have the right to oppose (art 26 of that law), access (art 34 of that law) and rectify (art 36 of that law) your personal data. You may thus request that your data, should it be inaccurate, incomplete, unclear, outdated, not be used or stored, be corrected, clarified, updated or deleted.
Personal information regarding our website's visitors, including their identity, is confidential.
The owners of this website hereby guarantee to respect the legal confidentiality conditions, applicable in France, and not to disclose this data to third parties.
Article Outline