Robyn Burton

How Does Glaucoma Look?: Patient Perception of Visual Field Loss

OBJECTIVE To explore patient perception of vision loss in glaucoma and, specifically, to test the hypothesis that patients do not recognize their impairment as a black tunnel effect or as black patches in their field of view. DESIGN Clinic-based cross-sectional study. PARTICIPANTS Fifty patients (age range, 52-82 years) with visual acuity better than 20/30 and with a range of glaucomatous visual field (VF) defects in both eyes, excluding those with very advanced disease (perimetrically blind). METHODS Participants underwent monocular VF testing in both eyes using a Humphrey Field Analyzer (HFA; Carl Zeiss Meditec, Dublin, CA; 24-2 Swedish interactive threshold algorithm standard tests) and other tests of visual function. Participants took part in a recorded interview during which they were asked if they were aware of their VF loss; if so, there were encouraged to describe it in their own words. Participants were shown 6 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 VF loss. MAIN OUTCOME MEASURES Forced choice of an image best representing glaucomatous vision impairment. RESULTS Participants had a range of VF defect severity: average HFA mean deviation was -8.7 dB (standard deviation [SD], 5.8 dB) and -10.5 dB (SD, 7.1 dB) in the right and left eyes, respectively. Thirteen patients (26%; 95% confidence interval [CI], 15%-40%) reported being completely unaware of their vision loss. None of the patients chose the images with a distinct black tunnel effect or black patches. Only 2 patients (4%; 95% CI, 0%-14%) chose the image with a tunnel effect with blurred edges. An image depicting blurred patches and another with missing patches was chosen by 54% (95% CI, 39%-68%) and 16% (95% CI, 7%-29%) of the patients, respectively. Content analysis of the transcripts from the recorded interviews indicated a frequent use of descriptors of visual symptoms associated with reported blur and missing features. CONCLUSIONS 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. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Glaucoma and reading: exploring the effects of contrast lowering of text.

Purpose. Past research has not fully ascertained the extent to which people with glaucoma have difficulties with reading. This study measures change in reading speed when letter contrast is reduced, to test the hypothesis that patients with glaucoma are more sensitive to letter contrast than age-similar visually healthy people. Methods. Fifty-three patients with glaucoma [mean age: 66 years (standard deviation: 9)] with bilateral visual field (VF) defects and 40 age-similar visually healthy control subjects [mean age: 69 (standard deviation: 8) years] had reading speeds measured using sets of fixed size, non-scrolling texts on a computer setup that incorporated an eye tracking device. All participants had visual acuity ≥6/9, and they underwent standard tests of visual function including Humphrey 24-2 and 10-2 VFs. Potential non-visual confounders were also tested, including cognitive ability (Middlesex Elderly Assessment of Mental Status Test) and general reading ability. Individual average raw reading speeds were calculated from 8 trials (different passages of text) at both 100% and 20% letter contrast. Results. Patients had an average 24-2 VF MD of −6.5 (range: 0.7 to −17.3) dB in the better eye. The overall median reduction in reading speed due to decreasing the contrast of the text in the patients was 20%, but with considerable between-individual variation (interquartile range, 8%–44%). This reduction was significantly greater (p = 0.01) than the controls [median: 11% (interquartile range, 6%–17%)]. Patients and controls had similar average performance on Middlesex Elderly Assessment of Mental Status Test (p = 0.71), a modified Burt Reading ability test (p = 0.33), and a computer-based lexical decision task (p = 0.53) and had similar self-reported day-to-day reading frequency (p = 0.12). Conclusions. Average reduction in reading speed caused by a difference in letter contrast between 100% and 20% is significantly more apparent in patients with glaucoma when compared with visually healthy people with a similar age and similar cognitive/reading ability.

Eye Movements in Patients with Glaucoma When Viewing Images of Everyday Scenes

This study tests the hypothesis that patients with bilateral glaucoma exhibit different eye movements compared to normally-sighted people when viewing computer displayed photographs of everyday scenes. Thirty glaucomatous patients and 30 age-related controls with normal vision viewed images on a computer monitor whilst eye movements were simultaneously recorded using an eye tracking system. The patients demonstrated a significant reduction in the average number of saccades compared to controls (P = 0.02; mean reduction of 7% (95% confidence interval (CI): 3-11%)). There was no difference in average saccade amplitude between groups but there was between-person variability in patients. The average elliptical region scanned by the patients by a bivariate contour ellipse area (BCEA) analysis, was more restricted compared to controls (P = 0.004; mean reduction of 23% (95% (CI): 11-35%)). A novel analysis mapping areas of interest in the images indicated a weak association between severity of functional deficit and a tendency to not view regions typically viewed by the controls. In conclusion, some eye movements in some patients with bilateral glaucomatous defects differ from normal-sighted people of a similar age when viewing images of everyday scenes, providing evidence for a potential new window for looking into the functional consequences of the disease.

The United Kingdom Glaucoma Treatment Study: A Multicenter, Randomized, Double-masked, Placebo-controlled Trial: Baseline Characteristics

OBJECTIVE The United Kingdom Glaucoma Treatment Study (UKGTS) tests the hypothesis that treatment with a topical prostaglandin analog, compared with placebo, reduces the frequency of visual field (VF) deterioration events in patients with open-angle glaucoma (OAG) by 50% over a 2-year period. Additional goals are to evaluate study power with novel clinical trial outcomes: (1) VF deterioration velocity and (2) VF and quantitative imaging measurements modeled as joint outcomes. DESIGN The UKGTS is a randomized, double-masked, placebo-controlled, multicenter treatment trial for OAG. PARTICIPANTS A total of 516 patients with newly diagnosed (previously untreated) OAG were prospectively recruited at 10 UK centers between 2007 and 2010. METHODS Eligible patients were randomly assigned to treatment with latanoprost 0.005% or placebo. The observation period was 2 years, with subjects monitored by VF testing, quantitative imaging, optic disc photography, and tonometry at 11 visits. MAIN OUTCOME MEASURES The primary outcome measure is time to VF deterioration within 24 months. Secondary outcomes include the deterioration velocity of VF and quantitative imaging measures. RESULTS The main source of referrals was optometrists (88%). A total of 777 subjects were assessed for eligibility, and 261 were excluded because they did not meet the inclusion criteria or declined to participate. The mean age of the 516 participants was 66 years, and 52.9% were male; 90.1% of the participants were white, and approximately one third (32.2%) reported a family history of glaucoma. A total of 777 eyes were eligible at initial assessment. Both eyes were eligible for 265 participants. Mean (standard deviation) intraocular pressure (IOP) at baseline for the eyes with better versus worse mean deviation (MD) was 18.9 (4.1) and 19.9 (4.7) mmHg, respectively (P = 0.0053). Some 56.1% of all eligible eyes had IOP <20 mmHg at baseline. The median (interquartile range) VF MD for all eligible eyes was -2.9 dB (-1.6 to -4.8 dB). CONCLUSIONS This is the first randomized, placebo-controlled trial to evaluate the efficacy of medical treatment in reducing VF deterioration in OAG. The baseline characteristics for eligible patients and eyes from this cohort are presented and compared with those of previous trials. The baseline characteristics are similar to those of the largely population-based Early Manifest Glaucoma Trial. The early stage of the glaucoma and relatively low IOP at diagnosis suggest remarkably sensitive case findings by community optometrists in the United Kingdom.