Estudio del nervio óptico mediante láser confocal de barrido en familias con glaucoma primario de ángulo abierto

Zusammenfassung

The study of the optic nerve’s morphology is important for the diagnosis and following of primary open-angle glaucoma (POAG ). The structural changes of the optic nerve (ON) often precede the development of a defect in the visual field. Many publications talk about the heritability of different ON morphometric parameters. They are primarily based on the study of twins and comparing ON photographs of dizygotic and monozygotic twins. However, there are few studies in which the heritability of the papilla’s morphological characteristics from parents to children is analyzed, and even less, in which the analysis has been carried out with the fiber layer analyzer HRT III. As a result of the above thery are raised several questions that generate our working hypothesis. It is well known that the disc area (DA) and the most of the ON’s morphological parameters are similar inf sibjects with the same genetic make-up, but what is the correlation between parents and children of the same family? And even more, is that correlation higher in glaucoma families than in healthy? Which corneal thickness correlation is in these families? What optic nerve parameters are associated with? How can we differentiate the optic nerve of an individual at risk for glaucoma, with a relative affected, from a healthy one? The objective of this thesis is to answer all these questions by a prospective observational study in which people who represents all groups (POAG parents, their children, healthy parents and their children) are included. We study the biometric data of ON, mainly DA by HRT III, and check if the correlation of these morphological features is greater in families with POAG than in healthy. We chose the last confocal scanning laser generation, HRT III, because it is highly reproducible and validated in the study of the morphology of the ON. The mainly endpoint chosen for this study is DA, because it is a morphological parameter, it has a stable size in adults and it is not affected by glaucoma pathogenesis. In addition to the biometric parameters, the central corneal thickness (CCT) is studied in families with POAG and healthy. Another secondary objective is to determine the correlation of morphological variables of the papilla, obtained by the HRT, and CCT between siblings of the same family and the differences in ON’s morphology between families with POAG and healthy. They are also evaluated the correlation between the ON’s biometric parameters , and the CCT , and the visual field’s mean deviation. The results obtained in this thesis are revealing. First, our main hypothesis is demonstrated. There is a higher AD correlation between POAG parents and their children than between healthy parents and children. Moreover, this fact also applies to another very important parameter in our clinical practice, vertical cup/disc (C/D) ratio. Although we did not observe a significant correlation in CCT among individuals of the same family, we see that POAG parents’ CCT is significantly lower than in healthy parents. This result provide information to so controversial issue, which is if the thin central corneal thickness is a risk factor for developing glaucoma or it is a consequence of the disease. Individuals with a family history of POAG rise great interest because the goal in these individuals is to detect the disease in its early stages. The study of ON in this group has shown that three parameters are singnificatly lower than in healthy children: ring area, ring volume, and horizontal curvature of the nerve fiber layer measured by GPS. Regarding the correlations between different stereometric parameters obtained by the HRT, we obtain that excavation area and volume, the C/D and ring/disc ratio, ring volume and mean and maximum excavation depth, are correlated among children of POAG patients. Thanks to OHTS we know that the risk of developing glaucomatous damage in the optic nerve in ocular hypertension patients are increased in eyes with thin ECC. It has also been argued that the CCT could have any effect on the optic nerve head’s resistance. Therefore, we want to know the relationship between the CCT and the morphology of the optic nerve head. We have obtained an inverse correlation between the CCT and the ring area and ring volume in the group of POAG patients’ children. Among individuals in this group also is founded a correlation in excavation area and excavation volume, C/D and ring/disc ratio, ring volume and the mean and maximum excavation depth. It is known that large disks often have large excavations and small discs, small excavations. Therefore we believe it is important to know whether there is a relationship between the most relevant morphological parameters that HRT provide and DA. Our results suggest that DA is directly correlated with excavation area, excavation volume and vertical C/D in families with POAG, and ring area in healthy families. Finally, we wanted to know if there is a interrelation among the different morphological characteristics of ON in different groups. Mean and maximum excavation depth is directly correlated with excavation area and volume, total and vertical C/D and, inversely with ring/disc ratio and the ring area, in both, POAG families and healthy families. The mean deviation of the visual field in glaucoma patients is inversely correlated with excavation area, total and vertical C/D and directly with ring area and volume, ring/disc ratio and layer retinal nerve fibers thickness. In conclusion: There is a higher correlation in AD between POAG parents and their children than between healthy parents and their children. POAG parents’ children differ from healhty in a smaller ring area and volume and in the horizontal curvature of the nerve fiber layer measured by GPS. Glaucoma parents differ from healthy in a less CCT. We do not observe a significant correlation between the CCT neither ndividuals of POAG family nor healthy. There is a higher correlation between POAG parents and their children in the vertical C/D than between parents and healthy children. Excavation area and volume, C/D and ring/disc ratio, ring volume and the mean and maximum excavation depth are significantly correlated among the children of POAG patients. DA is directly correlated with excavation area, excavation volume and vertical C/D in POAG parents and their children and with ring area in healthy parents and their children. Mean and maximum excavation depth is directly correlated with the excavation area and volume, total and vertical C/D and inversely with the ring/disc ratio and the ring area, in both, POAG and healthy families. Mean deviation of the visual field in glaucoma patients is inversely correlated with excavation area, total and vertical C/D and directly with ring area and volume, ring/disc ratio and layer retinal nerve fibers thickness. CCT is inversely correlated with the ring area and volumes in the offspring of patients with POAG .