For this analysis the clinical course of 153 eyes of 153 patients (80 female and 73 male; 77 right and 76 left eyes) were included. Four groups of eyes suffering from different types of glaucoma were treated. 113 eyes (74%) were treated for POAG, 5 eyes (3%) for NTG, 13 eyes (9%) for secondary glaucoma and 22 eyes (14%) for pseudoexfoliation glaucoma. Of the 13 secondary glaucoma cases, four were due to previous eye trauma, four were due to neovascularization (2 cases of proliferative diabetic eye disease and 2 cases of central retinal vein occlusion, the underlying disease being considered in a stable phase at the time of XEN implantation), three cases were secondary to uveitis and the last two cases were due to steroid-induced glaucoma. In the complete patient group the mean age of patients at the time of surgery was 70.2±10.8 years. The difference in mean patient age was not statistically significant between the four treated patient groups (p=0.24). Before surgery the mean IOP of the 153 eyes was 23.9±7.4 mmHg in the 153 eyes. Statistical analysis revealed significant IOP differences between the four subgroups (Kruskal-Wallis: p<0.01). Further analysis revealed differences of statistical significance when comparing IOP results between POAG and PEX groups (p=0.001), NTG and PEX groups (p=0.001) and NTG and secondary glaucoma groups (p=0.02). The mean number of active substances contained in the applied IOP-lowering eye drops was 2.6±1.2 before surgery, and the comparison between the four treated groups showed no statistically significant difference (Kruskal-Wallis: p=0.56). The mean defect tested by standard automated perimetry was 10.1±4.3 dB before surgery, and the comparison between the four treated groups showed no statistically significant difference (Kruskal-Wallis: p=0.96). The exact demographic data are also presented in Table 1.
In the complete group of eyes analyzed mean IOP before surgery was 23.9±7.4 mmHg. Two days after XEN implantation, mean IOP decreased to 9.2±5.2 mmHg and then increased again to 15.5±7.9 mmHg one month and to 15.9±6.1 mmHg three months after surgery. Thereafter, mean IOP remained stable with a mean value of 15.4±5.1 mmHg one year after XEN implantation, which corresponds to a mean IOP reduction of 31% compared to baseline before surgery. For the complete group of eyes analyzed the difference between the mean IOP results measured at all follow-up examinations and those measured at baseline was statistically significant at all-time points (p<0.01). The exact values and the course of mean IOP during the first 12 months after surgery for the complete group as well as for the four treated subgroups are summarized in Figures 1 & 2 and Table 2.
IOP results in different types of glaucoma
Mean IOP at baseline before XEN implantation in the 113 POAG eyes was 22.8±6.5 mmHg. Two days after surgery mean IOP dropped to 8.9±5.1 mmHg. From the follow-up examination one month after surgery the IOP remained stable at about 15 mmHg and one year postoperatively the mean value was 15.1±4.6 mmHg. This corresponds to an average IOP decrease of 31% compared to baseline. Comparison of mean IOP results before and after surgery showed a difference of statistical significance (p<0.01) at all follow-up examinations.
In the 5 NTG eyes the mean IOP before XEN implantation was 16.6±3.4 mmHg. Mean IOP decreased to 5.6±2.7 mmHg two days after surgery and rose again to 10.0±3.0 mmHg one month after surgery and remained relatively stable thereafter with a mean value of 11.6±2.2 mmHg 12 months after surgery. This corresponds to an IOP reduction of 29% from baseline. IOP was well regulated, with all five eyes achieving an IOP <15 mmHg 12 months after surgery. Comparison of mean IOP results before and after surgery showed a difference of statistical significance (p<0.05) at all follow-up examinations.
In the 22 treated eyes suffering from PEX mean IOP before surgery was 28.0±7.9 mmHg. Similarly to the other treatment groups mean IOP decreased to 11.9±6.4 mmHg two days after surgery and increased to 16.5±8.0 mmHg one month after surgery. Thereafter, IOP remained reasonably stable with a mean value of 17.1±6.6 mmHg one year after XEN implantation, which corresponds to a decrease of 38% compared to baseline. The comparison between the average IOP results before and after surgery showed a difference of statistical significance (p<0.01) at all follow-up examinations.
In the 13 eyes suffering from secondary glaucoma mean IOP before surgery was 28.9±13.9 mmHg. Mean IOP dropped to 8.7±4.6 mmHg 2 days after surgery. Thereafter, as in the other treatment groups, mean IOP increased to 16.7±10.6 mmHg one month after XEN implantation and remained stable with a mean of 15.5±6.9 mmHg at the follow-up examination one year after surgery, which corresponds to a mean IOP decrease of 36% compared to baseline. Comparison of follow-up to baseline results again showed a difference of statistical significance at all-time points (p<0.05).
Further comparison of IOP results between the four treatment groups 12 months after XEN microstent implantation also revealed differences of statistical significance (Kruskal-Wallis: p<0.01). Here further testing revealed differences of statistical significance between POAG and NTG groups (p=0.029) as well as between NTG and PEX groups (p=0.006). However, when comparing results for mean IOP reduction from baseline to 12 months after surgery between the four groups, no difference of statistical significance was found (Kruskal-Wallis: p=0.2).
Complete and qualified success
Taking into account the WGA guidelines and the criteria summarized above defining complete and qualified success levels A to C, in the complete group of 153 eyes 60% achieved a complete success (A) and 74% a qualified success (A). Complete success levels B and C were achieved by 51% and 45% respectively. Qualified success B and C was achieved by 61% and 56% in the complete group of 153 eyes operated. The exact results for complete and qualified success levels A to C achieved in the four subgroups of different glaucoma entities is summarized in Table 3. Further analysis revealed differences of statistical significance between the four groups treated only concerning complete success (A) (Kruskal-Wallis: p=0.03) and qualified success (C) (Kruskal-Wallis: p=0.01). Further testing revealed that the aforementioned differences of statistical significance were due to higher success rates in the PEX group than in the POAG group (Mann-Whitney test: POAG~PEX for complete success (A) p=0.004 and POAG~PEX for qualified success (C) p=0.001).
The exact course of the number of IOP-lowering eye drops applied is summarized in Figure 3 and Table 4. The average number of active substances applied in the entire group of 153 eyes fell from 2.6±1.2 before to 0.8±1.3 12 months after XEN implantation (p<0.01). In the four subgroups treated the number of applied drugs decreased from 2.5±1.2 to 0.8±1.3 in the POAG group (p<0.01), from 2.6±0.9 to 0.6±0.9 in the NTG group (p<0.05), from 2.9±1.2 to 1.0±1.3 in the PEX group (p<0.01) and from 2.7±0.9 to 0.7±1.4 in the group of eyes suffering from secondary glaucoma (p<0.01) during the first 12 months after surgery.
In the entire group of 153 eyes treated with the XEN microstent, mean BCVA remained stable and showed no difference of statistical significance during postoperative follow-up. Mean BCVA was 0.38±0.52 logMAR before surgery and 0.36±0.49 logMAR 6 months and 0.37±0.49 logMAR 12 months after surgery (p=0.97 after 6 months and p=0.88 after 12 months compared to baseline) (See also Figure 4 for the exact course).
In the 113 POAG eyes mean BCVA was 0.33±0.47 logMAR before and 0.34±0.47 logMAR 12 months after surgery (p=0.31). This included 7 eyes with a BCVA loss of ≥0.2 lines during the 12 months of follow-up. Reasons for this loss of function was glaucoma disease progression in 2 cases, AMD progression in 3 cases, CSME development in 1 case and further progression of senile cataract in 1 case. In the 5 NTG eyes mean BCVA was 0.42±0.46 logMAR before and 0.36±0.37 logMAR 12 months after surgery (p=0.22). In the NTG group no case of BCVA loss of ≥0.2 lines was registered during follow-up. In the 13 PEX eyes mean BCVA was 0.36±0.46 logMAR before and 0.22±0.23 logMAR 12 months after surgery (p=0.92). In the PEX group one case of vision loss of ≥0.2 lines was registered, which was due to progression of glaucoma. In the group of eyes treated for secondary glaucoma mean BCVA was 0.74±0.63 logMAR before and 0.66±0.53 logMAR 12 months after surgery (p=0.91). This included one case experiencing vision loss of ≥0.2 lines, which was due to progression of glaucoma.
Comparison of BCVA between groups showed that there were differences of statistical significance concerning BCVA (Kruskal-Wallis: p<0.01). Mean BCVA was worse in the secondary glaucoma group than in the three other groups treated. Further performed Mann-Whitney tests confirmed a difference of statistical significance when comparing BCVA between the secondary glaucoma and the POAG groups (p<0.01) and between the secondary glaucoma and the PEX groups (p<0.01). Further testing did not reveal differences of statistical significance between any of the other groups. Finally, when comparing the BCVA change occurring over the 12 month follow-up period in between the four groups treated no difference of statistical significance could be revealed (Kruskall-Wallis; p=0.35).
Simultaneously with the drop of mean IOP, mean visual field defect remained stable. In the complete group of 153 eyes treated mean defect was 10.1±4.3 dB at baseline, increased slightly to 10.8±4.3 dB at 6 months (p=0.11) and was 10.8±4.2 dB at 12 months after surgery, which was not statistically significant (p=0.15). Also, the comparison of mean BCVA between the four treatment groups before and 12 months after surgery did not reveal differences of statistical significance (Kruskal-Wallis; before surgery: p= 0.08; 12 months: p=0.3) (see Table 5 for details).
Complications and needling rate
To achieve the results described, 64 needling procedures had to be performed in 54 of the 153 eyes (35.3%). 44 eyes needed 1 needling and another 10 eyes needed 2 needlings during the first year after XEN implantation. None of the eyes needed >2 needlings. The needling rate was different between the four subgroups analyzed (see Table 6). The lowest needling rate was found in NTG eyes (20%) and the highest rate in PEX glaucoma eyes (55%). In the total group of 153 eyes treated 20 eyes showed benign choroidal detachment during the first postoperative month. All cases responded well to conservative treatment (contact lens and cycloplegia). A large and prominent subconjunctival hemorrhage (to the extent that it was classified as clinically significant) was seen in 12 cases immediately after surgery, but was resorbed after 1 to 4 weeks. Blood in the anterior chamber immediately after surgery was seen in 10 eyes and dissolved in all cases without further consequences after 1 to 4 weeks. Postoperative macular edema was seen in 3 eyes, which all responded well to treatment with carbonic anhydrase inhibitors. Apart from the above described incidents, no serious complications were observed in the treated eyes.