Posters

Comparison between contrast sensitivity, visual acuity and retinal nerve fibre layer thickness vs visual field defects in glaucoma patients

Poster Details

First Author: I. Gomes PORTUGAL

Co Author(s):    M. Vila Franca   J. Godinho   J. Segurado   R. Seldon   P. Rosa   J. Fernandes     

Abstract Details

Purpose:

Visual function can be evaluated in several different ways. Among them is visual acuity (VA) and contrast sensitivity (CS). Different methods can be used to assess CS. The Pelli-Robson test determines the minimum contrast requiered to detect constant size characters, ie, the contrast decreases as the font size remains constant. Several studies have described alterations of CS associated with various diseases, including early-stage glaucoma. Therefore, in this study, we aim to investigate the relationship between CS, VA and retinal nerve fibre layer (RNFL) thickness versus visual field defects, in glaucoma patients.

Setting:

Dr. Gama Pinto Institute of Ophthalmology, Lisbon, Portugal.

Methods:

We performed a prospective observational study on 32 eyes of 18 patients, from the glaucoma consultation at our hospital. All patients in this study were either diagnosed with glaucoma, or strongly suspected of having glaucoma or presenting ocular hypertension (OHT) with VA ≥20/50. All patients were assessed for VA using the ETDRS scale test distance of 4 meters. CS was assessed using the Pelli-Robson chart at 1 meter test distance. RNFL thickness was measured by scanning laser polarimetry - GDxPROTM. Visual field defects were evaluated using the index value mean deviation (MD) obtained from computerized static perimetry: Humphrey 30-2 program.

Results:

32 eyes were studied, 47% were from glaucomatous patients, 34% were from patients suspected of having glaucoma, and 19% were from patientes having OHT. There was a moderate positive correlation between VA and MD (r=0.356, p=0.023) and a strong positive correlation between the CS and MD (r=0.601, p<0.001). There was a moderate positive correlation between the average thickness of the RNFL and MD (r=0.386, p=0.014) and between the thickness of the lower RNFL and MD (r=0.353, p=0.024). There was a strong positive correlation between the thickness of the upper RNFL and MD (r=0.561, p<0.001).

Conclusions:

Our results show that an increase on the visual field defect is associated with a decreased CS and decreased in RNFL thickness in patients with glaucoma and VA ≥20/50. Thus, CS evaluation appears to be useful as an early detection and motorization method of glaucoma patients, suspected of having glaucoma patients or OHT individuals, although the small number of patients in each group does not allow the extrapolation of the results and follow up studies on these same patients would prove useful in understanding the predictive and diagnostic values of our observations.

Financial Disclosure:

NONE