Subjects

Eligible patients signed an informed consent form before enrollment in the study. All subjects were established patients on the Glaucoma Service of the Wills Eye Institute. Approximately 2000 charts of all patients returning for examination during the period of the study (March 2006 through December 2006) were screened consecutively for possible inclusion. Before starting enrollment, a prospective plan for selecting patients was designed to assure inclusion of cases with the full range of VF loss (from none to far advanced), with approximately equal numbers of cases with various stages of glaucomatous field loss representing the entire spectrum of glaucomatous damage.

Exclusion criteria included the inability to understand and respond to spoken English, incisional eye surgery within the previous 3 months, laser treatment within the previous 1 month, presence of cataract (Lens Opacities Classification System II grade 2 or more), or presence of significant neurologic, motor, or other comorbidity that might have prevented the patient from completing the study. Patients who had primary open-angle glaucoma, primary angle-closure glaucoma, normal-tension glaucoma, pseudoexfoliative glaucoma, pigmentary glaucoma, inflammatory glaucoma, neovascular glaucoma, angle recession glaucoma, and plateau iris syndrome glaucoma were included in the study.

Of the patients who were considered eligible for inclusion, 50 declined to participate because of the time required. Although 200 subjects agreed to participate and started the study, 6 did not complete the project, all because of time constraints. No patients with ocular hypertension were included in the present study.

Clinical Evaluation

All participants received a standard examination as part of their routine ophthalmic clinical care before giving their informed consent. Visual acuities (monocular and binocular) were measured using the Lighthouse Early Treatment Diabetic Retinopathy Study Distance Visual Acuity Test, 2nd edition. Visual acuity was measured with the patient’s present, walk-in, refractive correction and was scored by counting how many letters were read correctly and converting this value to logarithm of the minimal angle of resolution units. Each participant also underwent monocular VF testing in each eye with an automated perimeter (Humphrey Visual Field Analyzer II; Humphrey Instruments, San Leandro, California, USA) using the 24-2 Swedish interactive threshold algorithm standard program, and binocular VF testing using the Esterman program. An appropriate corrective lens was used in all cases, based on the patient’s refractive correction for distance, modified for the patient’s age or lens status. Patients did not perform new VF tests if they had been tested fewer than 6 months before the study using the same strategy. Binocular contrast sensitivity was measured at 1 m using the Pelli-Robson contrast sensitivity chart and protocol. All patients completed the NEI-VFQ 25 QoL survey.

Visual Field Scoring

For each of the 192 patients, each monocular VF result was scored according to the following staging systems: (1) the Hodapp-Parrish-Anderson score (ordinal, 0 through 4), (2) the Field Damage Likelihood Scale (ordinal, 0 through 7), (3) the Glaucoma Staging System (ordinal, 0 through 5), (4) the Glaucoma Staging System 2 (ordinal, 0 through 5), (5) the Humphrey Visual Field Analyzer II mean defect (MD; −30 through 2 dB), and (6) the Humphrey Visual Field Analyzer II pattern standard deviation (0 through 15).

Fields were also staged according to 2 binocular systems. One of these was the Integrated Visual Field (IVF) system described by Crabb and associates (ordinal, 0 through 104). Each location in the right monocular VF has a corresponding point in the left monocular field in binocular viewing. The maximum raw sensitivity from each of the 2 overlapping locations is then plotted to create a grid of sensitivity values, representing the IVF. Next, each of the 52 points that make up the IVF is considered in turn. A point is scored 0 if it exhibits a measured threshold of 20 dB or better, a point is scored 1 if it has a threshold between 10 and 19 dB, and a point is scored 2 for a threshold of less than 10 dB. The scores at each point are added across the whole of the IVF, giving a summary value of the damage across the field: a completely defective integrated VF results in an IVF score of 104, whereas a normal, unaffected integrated VF yields an IVF score of 0. The other binocular VF test was the Esterman program, which was recorded as the Esterman Binocular Disability Score (ordinal, 0 through 100).

If a patient was unable to complete monocular automated VF testing in the worse eye because of poor vision, an MD score of −30 dB and a pattern standard deviation of 15 were given for that eye, and that eye was assigned the worst clinical stage (4, 7, 5, and 5) within the Hodapp-Parrish-Anderson, Field Damage Likelihood Scale, Glaucoma Staging System, and Glaucoma Staging System 2 staging systems, respectively. Additionally, when calculating the IVF score, each of the points in such eyes was considered to have a sensitivity value of less than 10 dB. The better eye was defined as the eye with the better overall VF sensitivity, as determined by MD.

The Assessment of Disability Related to Vision Test

Tasks included in the ADREV test were based on a second-generation performance-based measure, the Assessment of Function related to Vision. The Assessment of Function Related to Vision instrument validated 5 tests of performance of visually intensive tasks based on item response theory in the form of Rasch analysis and significant relationships with both traditional clinical measures of ophthalmic status, as well as self-reported vision-specific QoL measured by the NEI-VFQ 25. The instrument used within the context of this investigation, titled the ADREV, was developed based on the findings of the Assessment of Function Related to Vision experiment, and the details of its design have been documented elsewhere.

Briefly, the ADREV comprises 9 tests, including: reading in reduced illumination, facial expression recognition, computerized motion detection, recognizing street signs, locating objects, ambulation, placing a peg into different-sized holes, telephone simulation, and matching socks. A description of each test item is presented in the Supplemental Appendix . Each test of performance is graded from 0 through 7 on an interval scale determined through Rasch analysis, where 0 represents the inability to perform the test and 7 indicates a perfect score. In addition to the subscale evaluations, the 9 tests are summed to produce a total ADREV score ranging from 0 to 63. The subscales can be used and interpreted independently from the ADREV total score. Average test administration time, including patient instruction, is approximately 30 minutes. The ADREV was validated previously in a study population involving patients with age-related macular degeneration and diabetic retinopathy through comparison with standard clinical measures of visual function and self-reported QoL.

The tasks were performed with both eyes open and with the subjects wearing their present habitual refractive correction. All 9 tasks were performed under ambient lighting (range, 35 to 40 foot candles), except for reading in reduced illumination, facial expression recognition, and computerized motion detection, all of which were tested in a dark room. Patients also were required to open 3 padlocks of different sizes with 3 different keys. This particular test does not seem to be related to visual ability; it was used to detect malingering and was not included in calculating the final ADREV score.

The NEI-VFQ 25 survey was administered to each subject. The NEI-VFQ 25 was selected as the study’s primary QoL measurement because it is accepted as a reliable and valid means of studying the self-perceived impact of visual impairment on vision-specific QoL. The NEI-VFQ 25 comprises 11 vision-specific subscales that address the following domains: general vision, near vision, distance vision, ocular pain, social functioning, mental health, role difficulties, dependency, driving, color vision, and peripheral vision. Each subscale is scored from 0 to 100, where 100 represents self-perceived perfect functioning and 0 represents the greatest level of difficulty in a given domain. The 11 subscales also are averaged to produce a VFQ total score ranging from 0 through 100. The average test administration time for the VFQ is approximately 10 minutes.

Statistical Analysis

Patient demographics were analyzed using descriptive statistics. Partial Spearman correlations adjusting for age, race, and visual acuity were used to compare scores from each of the ADREV subtests with each of the VF staging systems. We also calculated correlations between the total ADREV score and each of the VF staging systems. P values were adjusted using the method of Benjamini and Hochberg to account for multiple testing and to control the false-discovery rate at 5%. Statistical significance was defined as P < .05. Each of the VF staging systems was compared with the total NEI-VFQ 25 score in a similar manner.