Capacidad diagnóstica de la microperimetría, el campo visual y la tomografía óptica de coherencia macular y papilar en el glaucoma

Resumo

INTRODUCTION Glaucoma is the second leading cause of blindness in the world after cataract so it is the main cause of irreversible blindness. The most common type of glaucoma in our country is primary open-angle glaucoma by far, that is defined as a multifactorial and progressive optic neuropathy. Ganglion cell death in the retina is associated with structural and functional changes. Structural damage is made up of disc cupping, thinning of neuroretinal rim, macular ganglion cell layer and retinal nerve fiber layer (RNFL). Functional damage causes several visual field defects with specific patterns. Over the last decade the development of new technologies and computing resources have provided a revolution in the diagnostic procedures of glaucoma. Specifically, the introduction of optical coherence tomography that allows the possibility of measuring papillary and retinal structures and segmentating and estimating the thickness of intraretinal layers, and microperimetry (MP) have let on more precise diagnosis in this disease. PURPOSE The main goal of this study is to evaluate the diagnostic capacity of several structural and functional tests: macular MP, macular automated perimetry (AP), macular and papilar OCT in order to make differences among the evolutionary stages of glaucoma and to investigate the correlation of the results as obtained by different tests. METHODS This is a transversal, descriptive study that recruited healthy patients, ocular hypertensive patients, and patients with primary open-angle glaucoma. These latter ones were divided into early, moderate and severe glaucoma. 128 eyes from 99 patients were finally included: 44 without glaucoma (22 healthy and 22 hypertensive eyes) and 84 with glaucoma (26 early glaucoma, 20 moderate glaucoma and 38 severe glaucoma). Each patient underwent three functional (MP, AP 10-2, AP 30-2) and two structural tests (papillary and macular OCT). Mean sensitivities in decibels and mean sensitivities converted to lineal scale were considered in functional tests. Concerning OCT, neuroretinal rim, cupping, peripapillary RNFL thickness and, in the macular region, thickness of the RNFL, the sum of ganglion cell layer and inner plexiform layer (GCLIPL) and outer retina were measured. Parameters obtained in these tests were compared between general groups in this study (groups with and without glaucoma) and between five subgroups. Otherwise, diagnostic capacities of the different parameters were calculated for structural and functional tests using receiver operating characteristics curves. Finally, a correlation study of the macular structure-function relationship between obtained parameters was conducted. RESULTS Every studied parameter showed diagnostic capacity of glaucoma. The comparison of the values obtained in different subgroup presented significant differences between all the subgroups except for healthy versus hypertensive subgroups (none parameter exhibited to be different) and early versus moderate glaucoma. Comparative analysis of duration in the functional tests concluded that the longest-lasting test was MP, followed by AP 10-2 and AP 30-2. The higher the stage severity was the longer the test was, independently of the kind of test. The comparison of structural results showed that area and volume of the neuroretinal rim, vertical cupping, peripapillary RNFL and macular GCL and RNFL presented diagnostic capacity in glaucoma. These parameters showed different results between different groups although, in general, the greater severity of glaucoma the higher they were. Thickness of outer retina did show no changes between groups. ROC curve analysis showed that the best parameters to distinguish between stages were pattern standard deviation (PSD) and the duration of functional tests that presented better capacity than structural parameters. Correlation analysis demonstrated good associations between both functional macular tests (MP and AP-10-2). The strength of these associations increased as long as the severity of the disease increased. Otherwise, it was found similar macular structure-function relationships using MP and AP 10-2 irrespective of whether the sensitivities were converted into linear scale or not. CONCLUSION Parameters of AP 10-2, microperimetry, papillary and macular OCT studied show a good diagnostic capacity in glaucoma. Plus, they are able to differentiate between different evolutionally stages of glaucoma except for the intervals of healthy and hypertensive patients and early versus moderate glaucoma. Among structural parameters studied, GCLIPL thickness has greater diagnostic capacity than RNFL. Considering functional parameters, the best discriminative power was found for PSD and duration of the tests, that they are superior to OCT parameters. Furthermore, macular structure-function correlations were more numerous and stronger as long as the severity of the disease increases.