Comprehensive ocular exams were performed for all eligible subjects after an interview to collect demographic details and personal risk behavior, dietary history, and utilization of eye care services. Ocular examinations were conducted in a clinic specially set up for the study by two ophthalmologists and optometrists trained for the study.
18 Written informed consent was obtained from the participants before any examination. The optometrists measured distance and near visual acuity, both presenting (with current refractive correction if any) and best corrected after refraction, with logarithm of minimum angle of resolution (logMAR) charts,
19 and performed an external eye examination, assessment of pupillary reaction, and anterior segment examination with a slit lamp biomicroscope. The optometrist also measured intraocular pressure (IOP) with a Goldmann applanation tonometer or a Perkins applanation tonometer if the IOP of a subject could not be measured using the Goldmann applanation tonometer. After examination by the optometrist, the subject was further examined by the ophthalmologist, who verified all abnormal findings noted by the optometrist. The ophthalmologist performed
gonioscopy on all participants with an two-mirror lens (NMRK; Ocular Instruments Inc., Bellevue, WA), and the angle was graded according to the classification of Scheie.
20 If the pigmented posterior trabecular meshwork was not visible in three fourths or more of the angle circumference in the primary position without manipulation in the presence of low illumination, the angle was considered occludable; otherwise, it was considered open. If the patient could not cooperate for gonioscopy, the van Herick technique was used to grade the peripheral anterior chamber depth with the slit lamp
21 ; if the peripheral chamber was less than one fourth of corneal thickness, the angle was considered occludable, otherwise it was considered open. All patients had their pupils dilated unless contraindicated because of the risk of angle closure. After dilatation, the lens was examined with the slit lamp for the presence of PXF and for lens opacities. The lens was graded clinically at the slit lamp against photographic standards for nuclear opalescence, according to the Lens Opacities Classification System III (LOCS III),
22 and for cortical and posterior subcapsular lens opacities, according to the Wilmer classification.
23 Stereoscopic examination of the optic disc and peripapillary area was performed at the slit lamp using a 78-D lens. The vertical cup-to-disc ratio was assessed in units of 0.05 by the ophthalmologist. The following disc features evoked suspicion of glaucomatous damage: vertical cup-to-disc ratio 0.65 or more in either eye; asymmetry in cup-to-disc ratio of >0.2 between the two eyes; neuroretinal rim <0.2 in any quadrant in either eye; notch in the disc in either eye; disc hemorrhage in either eye; and nerve fiber layer defect. We assessed the agreement of examining ophthalmologists in this study for two parameters in 80 eyes: gonioscopy and optic disc evaluation with a 78-D lens. The agreement for grading the angle as open or occludable was high (κ statistic, 0.85), as was the agreement in determining the vertical cup-to-disc ratio (intraclass correlation, 0.97). Fundus examination was also performed with the indirect ophthalmoscope with a 20-D lens. Standard classifications were used to grade age-related macular degeneration and diabetic retinopathy.
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