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J. E. Boneta, J. Sherman, S. Nath; Early, Pre-Perimetric and "Slit" RNFL Defects Detected With Optomap® P200c. Invest. Ophthalmol. Vis. Sci. 2010;51(13):4364.
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To determine whether the Optomap® P200C is useful in detecting retinal nerve fiber layer(RNFL) defects and to assess whether such defects correlate with documented structural loss on GDx VCC and OCT and/or visual field loss.
As part of an ongoing study, weekly retrospective review was performed of all Optomap® P200C images taken in one office where all patients are routinely imaged. Composite images from patients (n=1000) were also reviewed in the green laser separation. Charts of patients with nerve fiber layer defects detected with P200C were then reviewed to assess if there was concordant structural or functional loss. If RNFL assessment (with either GDx or OCT-Stratus or Spectralis) or visual fields(VFs) 24-2 SS were not in the chart, the patient was recalled for that testing. If the location of the RNFL loss predicted a field loss beyond 30 degrees, 60-4 VFs were also obtained.
RNFL loss with the P200C in the absence of obvious cupping and pallor was found in 49 patients. GDx and/or OCT correlated in 82% (40/49 eyes) but some additional defects on GDx(and occasionally on OCT) were not detected by the examiner interpreting the P200C images. Corresponding field loss on the 24-2 was found in about 69% (34/49 eyes) of the cases but this increased when results of the 60-4 were also included. Some narrow RNFL defects detected with the P200C do not correlate with GDx, OCT or visual fields. "Slits" in the RNFL, believed to be physiological, occur in the absence of corresponding GDx and OCT defects. In contrast to "authentic" RNFL defects, slits were observed in nearly half of all eyes, are more narrow than major retinal vessels, do not widen peripherally and do not reach the disc. In 9 patients, easily observable 1 DD wide RNFL defects 4 or 5 DDs from the optic nerve head tapered and became undetectable at the disc. In 10 patients,the RNFL loss was due to a non-glaucomatous optic atrophy, such as LHON, AION, disc drusen.
The Optomap® P200C, most often utilized for the detection of retinal abnormalities through an undilated pupil, appears useful in detecting RNFL defects. Moderate to large wedge defects correlate with RNFL reduction with GDx and OCT and less often with visual fields. Narrow defects may be normal variants or may represent very early loss. Follow up examination including diagnostic tests of structure and function are recommended in order to diagnose glaucoma as early as possible.
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