This prospective study found that patients with glaucoma do not perceive their vision loss as a black tunnel effect or as black patches masking their field of view. These findings are important in the context of depicting the effects of glaucomatous vision loss and raising awareness for glaucoma detection.
This study indicates that many patients with fairly advanced glaucoma, believing that without tunnel vision they are doing well, are being lulled into a false sense of security. They need to be informed of the importance of a variety of visual abnormalities that may indicate the presence of glaucoma and, if present, require examination to exclude or confirm the disease.
To the authors’ knowledge, there has been no direct assessment of patient descriptions of the perception of glaucomatous visual field loss. Having a narrative directly from the patients would be helpful in constructing images and films of what is seen and, perhaps more importantly, dispelling myths about how glaucoma appears to someone with the condition.
Fifty patients ranging in age from 52 to 82 years, with visual acuity better than 20/30 and with a range of glaucomatous visual field defects in both eyes, underwent monocular visual field testing in both eyes using a Humphrey Field Analyzer (HFA) and other tests of visual function. Participants also took part in a recorded interview during which they were asked if they were aware of their visual field loss. If so, there were encouraged to describe it in their own words. They were also shown six images modified in a variety of ways on a computer monitor and were asked to select the image that most closely represented their perception of their visual field loss.
Participants had a range of visual field defect severity, with an average HFA mean deviation of 8.7 dB and 10.5 dB in the right and left eyes, respectively. Thirteen patients (26 percent) reported being completely unaware of their vision loss. None of the patients chose images with a distinct black tunnel effect or black patches. Only two patients chose the image with a tunnel effect with blurred edges. An image depicting blurred patches and another with missing patches was chosen by 54 percent and 16 percent of patients, respectively. Analysis of the recorded interviews indicated frequent use of descriptors of visual symptoms associated with blur and missing features.
The authors note that when participants were asked to name everyday situations in which they noted the impact of their visual field loss, many of the themes reported in studies of quality of life and visual disability in patients with glaucoma re-emerged. For example, mobility, driving, falling, fear of falling, and reading, all were mentioned consistently.
They also note that many participants became more aware of their vision loss at night, as has been highlighted previously as a perceived impairment in glaucoma. Furthermore, an everyday activity that has received little attention in glaucoma but has emerged here as being associated commonly with recognizing symptoms was computer use, especially locating the cursor and using the computer mouse. Perhaps this is reflective of the increasing use of computers and the Internet in an elderly population.
The authors conclude that this study’s results have important clinical implications and are relevant for designing appropriate information about the visual symptoms of glaucoma. Many patients eloquently articulated the recurrent phenomena of missing part of their visual field or described their functional loss as a type of blur. These responses seem orthogonal to the conventional view of the visual symptoms associated with glaucoma, which include the narrowing of peripheral vision. These findings therefore are relevant to the practitioner in primary eye care responsible for screening and identifying cases of glaucoma, especially when making the differential diagnosis between the need for a refractive prescription or correctable vision loss and investigating a complaint of, for instance, blur as a potential symptom of glaucoma.