Safe exposure times for slit-lamp fundus biomicroscopy with high plus lenses.
OBJECTIVE
The purpose of this study was to calculate the retinal irradiance and maximum permissible exposure time (MPE) using high plus fundus biomicroscopy lenses.


METHODS
Four Volk handheld condensing lenses (+78 D, +90 D, Superfield NC, and Super 66) were tested with biomicroscopes from three manufacturers (Nikon, Topcon, and Zeiss) on both high and medium illumination. Using the conservation of radiance theorem, the retinal irradiance was calculated and. with guidelines from the American National Standard Institute (ANSI). the maximum permissible exposure time was determined.


RESULTS
The range of MPE time across all lenses and biomicroscopes was from 23 seconds to 74 seconds on high illumination setting. The average MPE times were: for the +78 D, 36 seconds; the Superfield NC, 57 seconds; the Super 66, 32 seconds; and the +90 D, 52 seconds.


CONCLUSIONS
Retinal irradiances and safe exposure times are useful guidelines in both the clinical and academic setting. Fundus biomicroscopy with non-contact high plus condensing lenses produced calculated retinal irradiances and MPE times similar to those of other commonly used ophthalmic equipment. Awareness of the maximum permissible exposure time increases the safety of this valuable technique.
Denial
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A
New England College of Optometry, Boston, Massachusetts, USA.
Hanley
M
M
D004867:Equipment Design; D004869:Equipment Safety; D005126:Eye Burns / Q000209:etiology / Q000517:prevention & control; D006801:Humans; D007909:Lenses; D008027:Light / Q000009:adverse effects; D008853:Microscopy / Q000295:instrumentation*; D009885:Ophthalmology / Q000379:methods*; D012160:Retina / Q000528:radiation effects; D013997:Time Factors