Treatment of ocular hypertension: Hamlet's Lament revisited

Serum and antibodies of glaucoma patients lead to changes in the proteome, especially cell regulatory proteins, in retinal cells

Purpose

Previous studies show significantly specifically changed autoantibody reactions against retinal antigens in the serum of glaucoma and ocular hypertension (OHT) patients in comparison to healthy people. As pathogenesis of glaucoma still is unknown the aim of this study was to analyze if the serum and antibodies of glaucoma patients interact with neuroretinal cells.

Methods

R28 cells were incubated with serum of patients suffering from primary open angle glaucoma (POAG), normal tension glaucoma (NTG) or OHT, POAG serum after antibody removal and serum from healthy people for 48 h under a normal or an elevated pressure of 15000 Pa (112 mmHg). RGC5 cells were additionally incubated with POAG antibodies under a normal pressure. Protein profiles of the R28 cells were measured with Seldi-Tof-MS, protein identification was performed with Maldi-TofTof-MS. Protein analysis of the RGC5 cells was performed with ESI-Orbitrap MS. Statistical analysis including multivariate statistics, variance component analysis as well as calculating Mahalanobis distances was performed.

Results

Highly significant changes of the complex protein profiles after incubation with glaucoma and OHT serum in comparison to healthy serum were detected, showing specific changes in the cells (e.g. Protein at 9192 Da (p<0.001)). The variance component analysis showed an effect of the serum of 59% on the cells. The pressure had an effect of 11% on the cells. Antibody removal led to significantly changed cell reactions (p<0.03). Furthermore, the incubation with POAG serum and its antibodies led to pro-apoptotic changes of proteins in the cells.

Conclusions

These studies show that the serum and the antibodies of glaucoma patients significantly change protein expressions involved in cell regulatory processes in neuroretinal cells. These could lead to a higher vulnerability of retinal cells towards stress factors such as an elevated IOP and eventually could lead to an increased apoptosis of the cells as in glaucoma.

[Arguments against pressure-lowering treatment of ocular hypertension. Prophylactic treatment is unnecessary]

The main argument against a pressure-lowering treatment for patients with ocular hypertension (OHT) is the principle of "first do no harm". The imprecision of intraocular pressure (IOP) measurements and the fact that increased IOP is only a risk factor for glaucoma raise major doubts on a clinical definition of OHT. The use of IOP-lowering treatment in the absence of functional or morphological glaucomatous changes should only be initiated if the IOP is very high (>32 mmHg). If the IOP is between 21 and 32 mmHg the glaucoma conversion risk of the individual patient should be estimated. The risk factors as proven in major prospective trials (OHTS/EGPS) should be assessed using the risk calculator. Only patients with a high risk (>13%) of conversion profit from prophylactic IOP-lowering treatment. For all patients with intermediate or low risk of conversion the potential side-effects (local and systemic) of the treatment outweigh the possible benefit, so that the principle of "watchful waiting" is the best for patients with OHT. If morphological or functional progression is observed IOP-lowering treatment should be started immediately.