Purpose
To determine the predictive value of ophthalmic screening tests with visually significant eye disease in a cohort of American Indian/Alaskan Natives from the Pacific Northwest.
Design
Validity assessment of a possible screening protocol.
Methods
Ophthalmic technicians performed a screening examination including medical and ocular history, best-corrected visual acuity, limbal anterior chamber depth assessment, frequency-doubling technology perimetry (FDT, C-20-5), confocal scanning laser ophthalmoscopy, nonmydriatic digital photography, and tonometry on 429 participants. An ophthalmologist performed a comprehensive eye examination on subjects with 1 or more abnormal screening tests and a random selection of those with normal screening tests. We used univariate and multivariate logistic regression to determine the association between abnormal screening test results and visually significant eye disease. We also determined the predictive value of screening tests with ocular disease.
Results
Univariate analysis identified history of eye disease or diabetes mellitus ( P < .001), visual acuity <20/40 ( P < .001), abnormal/poor-quality confocal scanning laser ophthalmoscopy ( P < .001), abnormal FDT ( P < .001), and abnormal/poor-quality nonmydriatic imaging ( P < .001) as associated with visually significant eye disease. A multivariate analysis found visually significant eye disease to be associated ( P < .001; receiver operating characteristic curve area = 0.827, negative predictive value = 84%) with 4 screening tests: visual acuity <20/40, abnormal/poor-quality nonmydriatic imaging, abnormal FDT, and abnormal/poor-quality confocal scanning laser ophthalmoscopy.
Conclusions
Ophthalmic technicians performing a subset of screening tests may provide an accurate and efficient means of screening for eye disease in an American Indian/Alaskan Native population. Confirmation of these results in other populations, particularly those with a different profile of disease prevalence, is needed.
Studies frequently use visual acuity assessment or questionnaires to screen for eye disease. Often these tests in isolation are inadequate to accurately and reliably detect eye disease. Other screening studies report results for a single condition such as diabetic eye disease or glaucoma. These approaches are limited in their comprehensive ability to identify those with other asymptomatic eye disease in a community-based screening.
Only limited work examines screening modalities for multiple ocular diseases. One such study in an adult, primarily black, internal medicine primary care population suggested a 2-step approach, first using a questionnaire to identify those at risk followed by referral for dilated examination. The prevalence of asymptomatic ocular disease within a population would be expected to vary the usefulness of a questionnaire as an initial screening tool. Another study found that presenting visual acuity less than 20/40 was highly sensitive for eye disease, but it was unable to identify an individual vision screening test that was both highly sensitive and specific for disease and it did not evaluate a combination of screening tests.
Early identification and therapeutic intervention reduces the morbidity associated with ocular diseases, particularly those without clinical symptoms in their early stages, such as glaucoma and diabetic retinopathy. Clinical studies, however, have yet to identify screening methods with high predictive values for identifying ocular disease in the general population. We assess the utility of employing a panel of ophthalmic screening techniques administered by an ophthalmic technician to identify participants with ocular disease and compare these results to a comprehensive eye examination by an onsite ophthalmologist. This study provides an opportunity to evaluate the predictive value of a panel of ophthalmic screening tests in a community-based study. Health care providers could use this testing paradigm to identify persons most likely to have eye disease and who would benefit from referral for comprehensive eye examination and treatment.
Methods
Study Population
This study includes data from the previously published Tribal Vision Project, a cross-sectional eye disease prevalence study in American Indian and Alaskan Native participants. The current study is a validity assessment of a possible screening protocol. Briefly, we randomly selected American Indian and Alaskan Native participants from 3 tribes from the northwest United States who were 40 years of age or older. All subjects had access to onsite medical care with ophthalmic care based on referral. We excluded participants with dementia or serious illness preventing travel to the clinic. We provided free transportation if needed. The Portland Area Indian Health Service Institutional Review Board approved this study. All participants signed an informed consent prior to enrollment in the study.
Screening Testing
Ophthalmic technicians performed an interview and examination consisting of a medical and ocular history, random finger stick blood glucose and glycosolated hemoglobin, automated refraction, tonometry (Tono-Pen XL; Medtronic Solan, Jacksonville, Florida, USA), slit-lamp assessment of limbal anterior chamber depth, frequency-doubling technology perimetry (FDT, program C-20-5), confocal scanning laser ophthalmoscopy of the optic disc and peripapillary retina, and nonmydriatic digital imaging of the fundus and optic disc. Participants had normal FDT testing if results had no areas of abnormal sensitivity and the test was reliable (less than 33% fixation losses or false positives). Subjects underwent repeat FDT perimetry if the initial result for an eye was abnormal (at least 1 area of abnormal sensitivity) or unreliable (defined as over 33% fixation losses or false positives). If abnormal or unreliable results persisted on repeat testing, subjects were considered screening failures.
Comprehensive Eye Examination by an Ophthalmologist
Technicians referred subjects for a dilated, comprehensive examination by an onsite ophthalmologist if they had a personal history of glaucoma, retinopathy, macular degeneration, other eye abnormality or diabetes, a blood glucose >127 mg/dL, or an A1C >5.7%. Subjects were also referred if 1 or both eyes had a best-corrected visual acuity <20/40, intraocular pressure >21 mm Hg, temporal limbal anterior chamber depth <25% of corneal thickness, abnormal or unreliable FDT perimetry on initial and repeat testing, borderline or abnormal Moorfield regression or poor-quality confocal scanning laser ophthalmoscopy, or the presence of optic nerve, retinal, or other eye disease on nonmydriatic imaging or poor-quality nonmydriatic digital imaging. If participants met the referral criteria in at least 1 eye, they were encouraged to have an examination. We also randomly selected 30% of subjects with normal screening results to have a dilated eye examination by an ophthalmologist to determine the predictive ability of passing all of the screening tests. The ophthalmologist was masked to the screening test results. The examination included slit-lamp biomicroscopy of the anterior segment, gonioscopy, Lens Opacity Classification System III grading of the lens, dilated fundus examination, and perimetry testing (24-2 Swedish interactive threshold algorithm standard, Humphrey Field Analyzer II; Carl Zeiss Meditech, Dublin, California, USA). The ophthalmologist used standard criteria for classification of ocular disease ( Table 1 ). A separate ophthalmologist independently confirmed any abnormality found during the comprehensive eye examination by chart review of the patient history, testing results, and photographs of the optic disc and macula, and this result was used to define the presence or absence of eye disease.
