Surgical Decisions in Primary Open Angle Glaucoma with Low or Normal Tension

Normal-tension glaucoma: Current concepts and approaches-A review

Normal tension glaucoma (NTG) has remained a challenging disease. We review, from an epidemiological perspective, why we should redefine normality, act earlier at lower pre-treatment intraocular pressure (IOP) level, and the role of ocular perfusion pressures, noting that perfusion is affected by defective vascular bed autoregulation and endothelial dysfunction. The correlation of silent cerebral infarcts (SCI) and NTG may indicate that NTG belongs to a wider spectrum of small vessel diseases (SVD), with its main pathology being also on vascular endothelium. Epidemiological studies also suggested that vascular geometry, such as fractal dimension, may affect perfusion efficiency, occurrence of SCI, SVD and glaucoma. Artificial intelligence with deep learning, may help predicting NTG progression from vascular geometry. Finally, we review latest evidence on the role of minimally-invasive glaucoma surgery, lasers, and newer drugs. We conclude that IOP is not the only modifiable risk factors as, many vascular risk factors are readily modifiable.

Latest Developments in Normal-Pressure Glaucoma: Diagnosis, Epidemiology, Genetics, Etiology, Causes and Mechanisms to Management

Normal-pressure glaucoma (NPG) is part of the spectrum of the open-angle glaucomas and morphologically characterized, as any glaucoma, by a loss of neuroretinal rim parallel to an enlargement and deepening of the optic cup, and development or enlargement of parapapillary beta zone. These morphological characteristics, in addition to the therapeutic benefit of lowering the intraocular pressure (IOP), make NPG differ from vascular-induced optic neuropathy. Based on the anatomy of the optic nerve as a cerebral fascicle, the physiological counter-pressure against the IOP is the orbital cerebrospinal fluid pressure (CSFP), with both pressures forming the trans-lamina cribrosa pressure difference (TLCPD). In contrast to the IOP, the TLCPD is the true pressure exerting force on the optic nerve fibers when passing through the lamina cribrosa. As a theoretical notion, an abnormally high TLCPD due to a low CSFP, in association with a low arterial blood pressure, could therefore be involved in the pathogenesis of NPG. It fits with the finding that the reduction of the IOP (and thus indirectly of the TLCPD) is (the only proven) procedure for NPG therapy. This review additionally highlights the genetic background, diagnostic methods, and therapeutic modalities of NPG.

Long-term results of deep sclerectomy in normal-tension glaucoma

PURPOSE

To study the long-term outcome of deep sclerectomy with and without mitomycin-C (MMC) in patients with normal-tension glaucoma (NTG).

METHODS

We prospectively analysed consecutive patients randomized to surgery performed either with (MMC group) or without (non-MMC) MMC. Surgery was considered totally successful if, after surgery, the preoperative intra-ocular pressure (IOP) level was reduced by 25% without medication, and a qualified success if medication was required to achieve the same limits.

RESULTS

A total of 37 patients were enrolled, 15 in the MMC and 22 in the non-MMC group. The median (range) follow-up was 7.9 (1.0-9.0) years, with a drop-out of three (8%) patients. The preoperative IOP was 15 (11-21) mmHg in the MMC and 15 (10-19) mmHg in the non-MMC group. At the last 6- to 9-year follow-up, IOP was significantly reduced to 9 (2-13) mmHg (p = 0.002) and 10 (5-13) mmHg (p < 0.001). The overall (groups combined) complete and qualified success rates were 50% and 71%, with no significant difference between groups (p = 0.48 and p = 0.25). Goniopuncture was performed in 87% and 100% of eyes in the MMC and non-MMC groups (p = 0.14). Needling with MMC injection was performed 0 (0-1) times in the MMC group and 0.5 (0-4) times in the non-MMC group (p = 0.056). We encountered no cases of hyphema, shallow anterior chamber, hypotony maculopathy, choroidal effusion, late bleb leakage, blebitis, endophthalmitis or malignant glaucoma.

CONCLUSION

In NTG, long-term significant IOP reduction can be achieved with deep sclerectomy with a low incidence of sight-threatening complications.