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Dry eye may affect accuracy of visual field measurements
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Specific conditions of the ocular surface may affect the reliability of visual field measurements in patients with glaucoma, according to a study.
In 34 eyes of 30 patients with open-angle glaucoma without visual field damage, tear break-up time (TBUT), tear meniscus volume (TMV), Schirmer’s test and presence of superficial punctate keratopathy (SPK) were assessed prior to visual field testing. A variety of gaze tracking (GT) parameters were calculated, including frequency of eye movements per stimulus, tracking failure frequency per stimulus (TFF) and the average blinking frequency. Possible associations between GT parameters and ocular surface condition measurements were investigated.
Significant correlations were found between SPK and increased frequency of eye movements and between TMV and increased rates of TFF.
As the authors noted, ocular surface disease is frequently observed in glaucoma patients due to the use of topical medications and to the preservatives that are contained in most of them. In addition, the prevalence of both glaucoma and dry eye increases with age. In this study, only patients without visual field defect were included, and an even higher prevalence of ocular surface disease should be expected in patients with more advanced glaucoma and more severe dry eye.
These findings, according to the authors, suggest that GT and visual field measurements may be altered by the presence of ocular surface disease, in particular by SPK and high TMV.
“Careful consideration is needed when assessing GT results in patients with these characteristics,” the authors concluded. – by Michela Cimberle
Disclosure: The authors reported no conflict of interest
Perspective
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Lisa M. Young, OD, FAAO
Reliability of visual field testing is difficult to control and often requires repeat testing to assure accurate results. Patient attention and ability are primary considerations, but there are many other factors that influence visual field performance.
In this study, Arai and colleagues found that gaze tracking parameters and visual field measurements are altered by the presence of ocular surface disease (OSD), particularly by the presence of corneal superficial punctate keratopathy and high tear meniscus volume.
Interestingly, we know that glaucoma patients are more likely to suffer from OSD, likely due to the use of preserved topical glaucoma medications. This effect is compounded by the fact that OSD increases naturally with age, as does the incidence of glaucoma.
There is no question that OSD can affect all aspects of visual function. This potential impact should be considered as we add topical medications to our treatment regimen, as we are potentially exacerbating the OSD and impacting our ability to accurately determine progressive glaucoma changes.
Laser trabeculoplasty, minimally invasive glaucoma surgery, fixed-combination glaucoma medications and nonpreserved/non-BAK preserved glaucoma medications may assist in better controlling IOP in patients with OSD.
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