Design of low cost glaucoma screening.

In 1991 the Netherlands Glaucoma Patient Association organized a glaucoma screening survey. This survey was designed to evaluate the effectiveness of a low cost screening setting. During a screening period of 8 days, 1259 subjects over the age of 49 years were examined by a team of non-ophthalmologically trained students. The following screening methods were used: visual field analysis (Henson CFS3000 perimeter), retinal nerve fiber layer photography (Canon non-mydriatic camera), intraocular pressure measurement (Pulsair non-contact tonometer) and determination of the peripheral anterior chamber depth (slitlamp biomicroscope, the van Herick method). In a later stage, subjects with glaucomatous abnormalities in the visual field and/or the photograph were re-examined by a glaucoma specialist using applanation tonometry, gonioscopy, ophthalmoscopy and Humphrey 30-2 visual field analysis. The time taken to conduct the individual screening tests in a subject varied from 1 to 5 min: perimetry took 5 min, photography 2 min, tonometry 3 min and angle-width determination 1 min. Fifty-six (4.4%) subjects showed glaucomatous defects in perimetry and/or photography. Thirty-seven could be re-examined and glaucoma was diagnosed in 16 subjects. Visual field defects and glaucomatous abnormalities in the photograph were confirmed by Humphrey perimetry in 72.7% and 35.7% respectively. Sixty-seven (5.3%) subjects had an intraocular pressure above 21 mm Hg, while no cases of angle closure glaucoma were found in this population. The costs of this screening setting were estimated at F1. 48,60 per screen. A future low cost screening survey might be limited to non-contact tonometry and visual field analysis with the Henson CFS3000 perimeter or a similar device, using suprathreshold testing with a limited number of points. Screening might be performed by non-medically trained employees. The costs of such a screening program may be estimated at F1. 16,- per screen and F1. 1.989,- per glaucoma case using a mobile screening unit (addendum).

Retinal nerve fiber layer assessment by scanning laser polarimetry and standardized photography.

PURPOSE: To determine whether, in a clinical setting, scanning laser polarimetry and retinal nerve fiber layer photography provide equivalent information on the retinal nerve fiber layer. METHODS: We prospectively studied 60 patients with glaucoma or ocular hypertension and 24 healthy subjects. With scanning laser polarimetry, an estimate of the cross section of the retinal nerve fiber layer was obtained. By using a photographic reference set, we quantified photographs of the retinal nerve fiber layer. Visual fields were used to relate the results of both methods to functional damage. RESULTS: The scanning laser polarimetry measurements yielded reproducible cross-section values (coefficient of variation, 6.6%). Comparison of cross-section values and photograph scores gave Pearson correlation coefficients smaller than r = .4 (P < .01), improving to a maximum of r = .53 after compensation for offset. When cross-section values were compared to the mean deviation of the visual field, the Spearman correlation coefficients varied from an r of -.34 to -.53 (P < .01). Correction for offset resulted in an r of -.54 to -.65. When photograph scores and mean deviation of the visual field were compared, the Spearman correlation coefficients varied from an r of -.65 to -.71 (P < .01). CONCLUSIONS: Because r was maximal at .53, the information on the retinal nerve fiber layer obtained with scanning laser polarimetry and photography seems not equivalent. This result could not have been because of lack of reproducibility. Although the results suggested possible offset in scanning laser polarimetry, other methodologic differences must be considered to explain the differences between the two techniques.