Assessing RNFL Plus GCIPL Improves Detection of Glaucoma Progression
Ophthalmology, October 2020
Wu et al. considered that progressive thinning of the retinal nerve fiber layer (RNFL) and the ganglion cell inner plexiform layer (GCIPL) may be a more reliable surrogate of glaucoma progression than the thinning of either layer alone. They found that evaluating these layers together helped identify disease progression in eyes that was not captured by looking at either layer separately. Their technique also boosted the ability to detect visual loss.
In this prospective study, the authors monitored 440 eyes of patients with glaucoma and 98 unaffected control eyes at intervals of approximately four months for at least three years. They used swept-source optical coherence tomography (SS-OCT) with a wide field (12 × 9 mm2) to measure RNFL thickness over the parapapillary region, GCIPL thickness over the macula, or the thickness of both layers during the same scan. Thinning was determined from serial SS-OCT data by trend-based progression analysis (TPA). False-positive results were defined as thinning detected by TPA in nonglaucomatous control eyes. Anatomic findings were compared with visual field (VF) results over time.
In the glaucoma group, 127 eyes (28.9%) had progressive thinning of the combined RNFL/GCIPL. Only 74 eyes (16.8%) had progression of the RNFL alone, and just 26 eyes (5.9%) had progression of the GCIPL alone. Thinning of either single layer usually was noted later than thinning of the combined RNFL/GCIPL; the median lag time was about four months. With the false-positive rate controlled at 5%, TPA specificity to detect thinning was 83.7% with the RNFL/GCIPL combo, 94.9% with RNFL only, and 96.9% with GCIPL only. Eyes with thinning of both layers had the greatest risk of visual loss, including “possible” VF progression (hazard ratio [HR], 2.4) and “likely” VF progression (HR, 4.6).
The authors concluded that TPA detection of progressive thinning of the RNFL/GCIPL combo, based on wide-field SS-OCT data, outperformed longitudinal assessment of either layer alone and captured more eyes at risk of visual decline. Analyzing both layers may be worthy of becoming a standard parameter to monitor glaucoma progression, said the authors. They stressed that their findings apply only to TPA of widefield scans and therefore should not be generalized to progression analysis of circumpapillary RNFL thickness or to guided progression analysis of RNFL or GCIPL thickness obtained with cube scans.
The original article can be found here.