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O Fass; Measurment of Anterior Chamber Width Using a standard Goldmann Lens . Invest. Ophthalmol. Vis. Sci. 2002;43(13):442.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To allow accurate measurement of the anterior chamber width (for placement of phakic or aphakic ACIOLs) using a Goldmann 3 mirror lens. Methods: Using a Goldmann lens, two experiments were performed. Two clamps fastened the Goldmann to a slit lamp at 90 degrees to the slit lamp desk. A ruler was centered and placed flush against the Goldmann (about 3mm from lens center). Millimeter lengths on the ruler were measured using the slit lamp light calipers. This was done to see if the baseline optics of the lens would produce a linear equation. Part II of the experiment simulated the anterior chamber. A series of contact lenses (+8.5 x 4 and a +4.5) were sutured together with 9.0 silk, to provide a lens of +42.5D to simulate a cornea. This mock-cornea lens was placed flush into the curved lens of the Goldmann with Renu saline solution (approximate index of refraction of aqueous humor) and held in place by a small ruler taped to the back of the Goldmann. The anterior portion of the Goldmann lens was then placed and sealed into a hole cut into a container also filled with Renu. This apparatus was clamped to the slit lamp and measurements were taken in the Renu solution with and without the mock cornea. Results: In the first experiment a linear relationship was discovered in two mirrors and the central lens of the Goldmann. The slope was steepest for the central lens; y=0.5833x-0.1611, R2 = 0.9992. The 73 degree mirror equation was; y=0.475x+0.2179, R2=0.9922. The 66 degree mirror yielded only four points because of the small field of view, y=0.32x-0.21, R2=0.9942. The 59-degree mirror proved too difficult because of the small field of view and is not included. In the second experiment, in simulated aqueous, only the central lens and 73-degree mirror are included. The central lens without a cornea yielded y=0.8714x-0.1554, R2=0.9994. When the contact lens was added the slope became slightly steeper (equation A) y=0.8946x+0.0696, R2=0.9988. In the 73 degree mirror this effect was even more pronounced, with a measurement of y=0.745x-0.2, R2=0.9976, without the cornea. When the cornea was added, the equation became steeper: (equation B) y=0.87x-0.145, R2=0.9972. Conclusion: In a setting that approximates the anterior chamber a known length (mm on a ruler) has been calibrated with the slit lamp light calipers. This data will be helpful in measuring the anterior chamber width and making sizing decisions about phakic and aphakic ACIOLs. In the 73-degree mirror, the iris of a dilated pupil may be measured at 90 and 270 degrees and added together using equation B. This sum is added to a measurment of the pupil diameter in the central lens, and calculated with equation A, for an angle to angle measurement that ACIOL size can be based on.
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