Análisis morfológico con OCT del daño glaucomatoso en distintos tipos de glaucoma de ángulo abierto

Abstract

INTRODUCTION: Glaucoma is an optic neuropathy that progressively leads to irreversible morphological changes of the optic nerve head and the retinal nerve fiber layer (RNFL) as well as functional changes with visual field deterioration. There is no consensus on which test, measuring structure or function, can first detect glaucomatous damage. On the other hand, there is agreement in considering by experts that early glaucoma diagnosis is crucial and that combining both structural and functional evaluation improves diagnostic sensibility. Incorporating image techniques, such as OCT, HRT or GDx, in glaucoma management allows to obtain reproducible and quantitative data, avoiding interobserver variability associated with old image techniques. From a functional standpoint, the computerized perimetry remains the screening methods most used glaucomatous damaged. OBJECTIVE: The main purpose of our work, through a prospective, observational and comparative study, is analyze whether OCT allow us to differentiate various types of Open Angle Glaucoma (OAG): Hyperbaric (HBG), Focal (FG) and Pseudoexfoliative (PEXG). We also want to show the differences in demographic characteristics in our study groups, to analize functional damage in each group, link the level IOP with visual field damage present in all three groups and, finally, to evaluate the correlation between optic nerve head topography measured with OCT parameters and the functional impairment index, MD and PSD. METHODS: We included 107 consecutive patients who attended our outpatient glaucoma clinic. 36 of them suffered of HBG, 43 of FG and 26 of PEXG. All subject were evaluated, in addition to a medical history and complete ocular examination, using white-white automated perimetry (Humphrey, HFA II) and a optic coherence tomography (OCT Stratus 3.0) exploration. The analysis of the results was performed using SPSS v15 (SPSS, Inc, Chicago, IL, USA). We considered significant at a value of p< 0,05. RESULTS: We found significant differences in baseline IOP of the 3 groups (p< 0,001) being the group HBG the most pressure and the FG the lowest IOP. We obtained no significant differences neither in the RNFL measurement (p= 0,28) or the visual field index MD (p= 0,191) and DSM (p= 0,074) among the 3 study groups. There was a statistically significant relationship between IOP and the value of MD in the group of HBG and PEXG but only the last showed a significant relationship between IOP and the value of PSD. The FG presented no significant correlation with any indexes. We found no significant differences in the size of the disc among of 3 groups (p= 0,93). PEXG was presenting significant greater area and neuroretinal rim volumen in the OCT analysis (p< 0,0001). We obteined no differences in the parameters of excavation between the HBG and FG groups. CONCLUSIONS: According to our results it´s worth to mention that although the three glaucoma groups start with a different IOP basal, they presented no differences in visual field global indexes or in average RNFL thickness. PEXG group, compared with the other two groups, had better measures of volumen and area rim. The groups of FG and HBG, groups very different in IOP basal, showed no differences in the parameters of excavation of OCT. PEXG is also presenting the best correlation between IOP and visual field global indexes, DM and PSD. Correlation between visual field sensivity and structural damage measured with OCT varies depending on the type of the glaucoma. Both PEXG and HBG presen a moderate structural-functional correlation while FG shows only a weak correlation between visual field indexes and some optic nerve head parameters of OCT.