This study aimed to explore the characteristics of glaucoma patients in the city of Ankara. To the best of our knowledge, no previous studies in Turkey included a large number of glaucoma patients such as our study, neither studied the proportion of the different types of glaucoma and their general characteristics. Ankara is the capital and the second largest city of Turkey after Istanbul and major urban center in Central Turkey. This urban area has a stable and homogenous population, with about 98% of the population identified as being Turkish ethnicity. We used an internationally recognized glaucoma classification system, and all the patients were examined by glaucoma specialists. The population of our study consisted of Caucasian origin, therefore the comparison of our results with those from other studies including Caucasian race would be appropriate.
We found POAG as the most common glaucoma type. In several other studies, POAG was also declared as the most common type of glaucoma in various populations [15–18]. In Caucasian races, POAG accounts for 75–95% of the primary glaucomas . In our study, women were more likely to develop POAG (52.5%). Male/female ratio of POAG patients differed from one study to other. While men were more commonly affected from POAG in Thessaloniki Eye Study, Yazd Study and the Maccabi Glaucoma Study reported a higher prevalence of POAG in women [16, 17, 19]. Mean age of our POAG patients was similar to the previous reports. There was a trend for increased number of POAG patients with increasing age. Approximately 89% of the patients with POAG had bilateral involvement.
A remarkably high number of PSXG cases were noted in this study and PSXG was the second most common diagnosis after POAG. As well known, prevalence of PSX highly varies between different ethnic groups. In a study from Japan, PSXG accounted for nearly 60% of POAG cases . On the other hand, a low prevalence of PSXG has been reported amongst Eskimos . PSXG was the most common glaucoma subtype in a clinic-based study from Ethiopia . Reykjawik Eye Study revealed that 31% of open-angle glaucoma patients had PSX . This ratio was similar in a study from Finland which reported that one third of newly diagnosed glaucoma cases had PSX . On the other hand, PSXG was not so common in India, Saudi Arabia, and finally Iran which is an eastern neighbor to Turkey [16, 21, 22]. In Greece, another neighbor to the west of Turkey however, clinic-based study revealed that PSXG is probably responsible for the majority of severe cases of glaucoma . In a recent population-based study, PSX syndrome has been shown to be common in Turkey . In a study from Eastern Mediterranean area of Turkey, percentage of PSX syndrome in patients with open-angle glaucoma was 46.9% . This ratio was quite high compared to our results in which 40.7% of open-angle glaucoma patients were PSXG. This ratio was around the highest ratios reported so far. PSXG patients comprised the oldest patients in the overall group and, similar to a previous study from Turkey, there was male preponderance . Bilateral involvement in these patients was present in 77% of our series, similar to the previous reports [16, 23]. Visual field parameters MD and PSD showed that PSXG patients had the second most serious field defects. Monocular and binocular blindness was common in PSXG patients (Table 5).
PACG was the third most common diagnosis. The prevalence of PACG was 2 times that of PAC. This finding is similar to previous reports and may suggest that not all people with PAC progress to PACG. Bilateral involvement was present in 90% of our PACG patients. Similar to reports of other clinic-based studies, there was a significant female preponderance [21, 22]. Proportion of PACG has been reported to be 16.7% and 16.3% of POAG in Europe, and worldwide, respectively . This ratio was slightly higher (19.4%) in our study population, but lower than the proportion of this glaucoma type in Asia and some neighboring countries . Monocular and binocular blindness were not so high when compared with other diagnosis groups. Blindness ratio was less than POAG and PSXG, 15.8% and 4% of PACG cases had monocular and binocular blindness, respectively. We think that, compared with POAG and PSXG, PACG is more likely to be symptomatic, resulting in a greater probability of seeking medical services. Another probability is that the easy access to cataract surgery in Turkey may have prevented these cases to progress to advanced glaucomatous damage.
NTG was the fourth common diagnosis in our group. NTG is reported as a common diagnosis in many population-based studies, though the numbers vary in different studies and populations. The main reasons for the variation are the differences in normal IOP range in different populations and difficulty in making the diagnosis. Large epidemiological studies in North America, Europe, and Australia estimated the prevalence of NTG to be up to half that of POAG [26–28]. The prevalence is considerably higher in Japan [6, 29]. The ratio of NTG in all the patients was 4.1% in our study. Our finding is similar to the previous reports from the neighboring countries and other white populations. In Maccabi Glaucoma Study, authors report that about 2.4% of the glaucoma patients were NTG . This ratio was 6% in a clinic-based study from Riyadh and 1.6% in a population based study from Yazd [16, 22]. In our study, NTG patients had the highest BCVA value. Monocular blindness ratio was less than half of POAG and there was no case with binocular blindness.
JOAG constituted 2.3% of all glaucoma patients in our study group. This ratio was slightly lower than the ratio of Indian patients (3.38%) while it was higher than the ratio in Ethiopian patients (0.9%) [14, 21]. The mean age of patients was 32,5 ± 12.9 years, and sex distribution was equal. Similar to previous studies, there was mostly bilateral involvement (91%) [14, 22]. While there was quite high number of monocular blindness (25%), binocular blindness (0.9%) was less than the average ratio of the whole patients.
SOAG contributed to 8.6% of all types of glaucoma. This ratio was higher compared to similar clinic-based studies in which the ratios were 3.0% and 3.3% [14, 22]. In our study, uveitic open-angle comprised the 44.7% of all SOAG patients and 3.8% of all patients. This ratio was significantly higher than a previous study by Cumurcu et al, which reported a ratio of 0.8% for uveitic open-angle glaucoma [22, 24]. In a study of 100 patients with uveitis, all of whom had anterior uveal involvement, glaucoma was present in 23 cases . McCluskey et al pointed out to glaucoma as one of the most insidious and, unfortunately, often overlooked complication of uveitis . Other common types of SOAG were traumatic glaucoma (2.4%) and pigmentary glaucoma (1.7%). As expected, patients with traumatic glaucoma mostly had monocular disease and were young male cases. Unilateral ocular involvement was significantly higher in SOAG patients and SOAG patients were younger than POAG, PSXG, and PACG patients. Male/female ratio was also significantly higher in SOAG patients. Monocular and binocular blindness ratios were 22.3% and 2.7%, respectively.
SACG patients were 5.4% of all glaucoma patients. In other two clinic-based studies, this ratio was 3.0% and 9.3% [14, 22]. In our study, male/female ratio of SACG patients was significantly higher than the other diagnosis groups. BCVA was worst and IOP was highest in this diagnosis group. SACG patients had the most severe disc damage. This diagnosis group included patients with neovascular glaucoma (2.8%), glaucoma related to retina and vitreous diseases (1.6%), lens related glaucoma (0.4%), uveitic angle-closure glaucoma (0.4%), ICE syndrome (0.2%), and malignant glaucoma. Highest monocular blindness ratio was in SACG patients (64.2%). Binocular blindness ratio was lower (8%).
Childhood glaucomas were 3.5% of all glaucoma types. This ratio was slightly higher than the results of a study from Saudi Arabia which has reported a ratio of 2.6% for childhood glaucomas . Primary congenital glaucoma (PCG) cases were 66% of CG cases, comprising 2.2% of the whole study population. As well-known, the incidence of PCG is geographically and ethnically variable, ranging from 1:22.000 in Northern Ireland to as high as 1:2.500 in Saudi Arabia and 1:1.250 among Gypsies in Romania [32, 33]. It is also common in certain regions of Turkey, but epidemiologic data regarding its incidence is lacking. Our ratio for PCG was very close to a previous study from Turkey while it was higher than the results of a clinic-based study from India in which, Das et al has reported the proportion of PCG as 0.79% [21, 34]. The sex ratio was significantly shifted towards the male side in our study population, as was reported in other studies. Glaucoma after congenital cataract surgery was the second most common type of glaucoma in childhood group (1%). Other CG cases associated with aniridia, Sturge-Weber syndrome, Axenfeld-Rieger anomaly and Peters anomaly comprised 0.3% of all patients. Nearly all of the patients (98%) with CG in our study population had bilateral involvement. CG patients had the highest ratio of binocular blindness (21.3%).
Over 20% of our patients were blind in at least one eye and 2.8% were blind bilaterally. This ratio is better than the reports of some clinic-based studies but monocular blindness ratio was higher than the study of Pakravan et al. which reported a ratio of 10.8% [14, 16, 20]. Quigley et al estimated the global binocular blindness ratio in OAG and ACG patients as 8.4 billion/80 billion (10.5%) by year 2010 . Bilateral blindness ratio in our study population is remarkably lower than this.
Our study has some limitations. The study is clinic-based rather than population-based which will have limited value in reflecting the true population when guiding service development. The sample is not representative of the whole population since only the patients who sought help were included. The strength of our study is that the study recruited a large number of patients from 10 different centers and used strict criteria in definition of glaucoma and glaucoma suspects. The ISGEO classification uses both structural and functional parameters for glaucoma diagnosis. There have been no previous studies investigating profile of glaucoma in Turkey and very little information is available glaucoma types, age distribution, burden of the disease and its management strategies. We think that our study may serve as a baseline for population based studies in the country.