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Muhammed S. Alluwimi, William Howard Swanson, Victor E Malinovsky, Brett J King; A basis for customizing perimetric locations at the macula in patients with glaucoma. Invest. Ophthalmol. Vis. Sci. 2017;58(8):4259.
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© ARVO (1962-2015); The Authors (2016-present)
It has been recognized that the 24-2 grid used for perimetry may poorly sample the macula, which has recently become a critical region for diagnosing and managing patients with glaucoma. We compared patients and controls to provide a basis for customizing perimetric locations at the macula, guided by en face images of retinal nerve fiber layer (RNFL) bundles.
We used Spectralis OCT en face images (Spectralis OCT, Heidelberg Engineering, V 6.0, Heidelberg, Germany) of the RNFL at the macula in 10 patients with glaucoma (ages 56 to 80 years, median 67.5 years). We measured perimetric sensitivities using a customized blob stimulus (a Gaussian blob with 0.25° SD) at 10-2 grid locations to assess the correspondence between damaged RNFL bundles observed on en face images and perimetric defects. However, there is uncertainty about how much displacement of the ganglion cell bodies would affect customized perimetric locations at the macula. We used a McNemar's test to compare the proportions of locations with perimetric defects that fell outside the damaged RNFL bundles, with and without accounting for displacement of the ganglion cell bodies. A perimetric defect was defined as a sensitivity at least 0.5 log unit less than the average sensitivity for that location in 10 age-similar control participants.
All patients had perimetric defects that were consistent with the patterns of damaged RNFL bundles as observed on the en face images. The total number of locations with perimetric defect was 134, the proportions of locations that fell outside the damaged RNFL bundles with and without accounting for displacement of the ganglion cell bodies were 14.2% and 16.4%, respectively. The difference between the two proportions did not reach statistical significance (p = 0.5 for a two-tailed test).
The perimetric losses we found with a 10-2 grid demonstrated similar patterns as the damaged RNFL bundles we observed on the en face images. A few perimetric defects fell outside the damaged RNFL bundles; the locations of these defects should also be considered when customizing perimetric locations at the macula.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
The 10-2 grid locations with perimetric sensitivities superimposed (Y-axis is flipped) on the en face images of the RFNL bundles without (top panel) and with (bottom panel) accounting for the ganglion cell body displacement. The color scale represents the perimetric sensitivities in log units.
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