Macular Ganglion Cell Complex Reduction Preceding Visual Field Loss in a Patient With Chiasmal Compression With a 21-Month Follow-Up

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Tieger et al (1) reported a series of 23 patients with chiasmal compression evaluated with optical coherence tomography (OCT) and standard automated perimetry (SAP) before and after surgical treatment. Because some of their patients showed complete visual field (VF) recovery despite persistent retinal ganglion cell (RGC) layer thinning on OCT, the authors suggested that RGC loss may precede VF loss, at least when assessed with standard 24-2 or 30-2 threshold strategies. Two invited commentaries pointed out that this is still an unsettled issue regarding compressive disorders of the anterior visual pathway (2,3). I had the opportunity to assess a patient with a pituitary tumor compressing the chiasm, followed for 21 months with OCT, SAP, and manual Goldmann perimetry (GP). My findings strongly support those of Tieger et al.
A 56-year-old woman was seen for a follow-up examination because of a nonsecreting pituitary adenoma mildly compressing the optic chiasm. The adenoma was discovered 8 years previously when MRI was obtained for her menstrual irregularities. At that time, the patient had no visual complaints, visual acuity (VA) was 20/20 bilaterally, and the remainder of the ophthalmic examination, including ophthalmoscopy, was normal. SAP (24-2 Swedish Interactive Threshold Algorithm standard test on the automated perimeter) and GP using the I/4e, I/3e, I/2e, and I/1e targets (with kinetic and central static presentations) were also normal. The patient opted for conservative management with visual and neuroimaging re-evaluation every 6 months. Five years later, with the patient still asymptomatic, bilateral VF defects to the I/2e and I/I3 isopters were detected using GP. MRI showed a small hemorrhage within the pituitary tumor, but the patient declined surgery. Six months later, VF improvement was observed, attributed to slight tumor shrinkage found on MRI. She was followed at 6-month intervals, with minimal VF depression (on both perimeters) in the upper temporal quadrant of each eye.
Six years after initial evaluation, the patient's acuity remained 20/20 bilaterally, VFs were stable (Fig. 1A), and OCT (3D OCT-2000; Topcon Corp, Tokyo, Japan) in each eye was performed. It showed the peripapillary retinal nerve fiber layer (RNFL) to be within normal limits, but the RGC-inner plexiform layer (IPL) in the macular area displayed few points of significant reduction in each nasal hemiretina (Fig. 1A). The GP showed a few points of missing static presentation to the I/1e target (Fig. 2A). Nine months later, repeat VF examination showed slightly better results on SAP (Fig. 1B), although testing on the GP was unchanged as was the tumor size on MRI. However, OCT revealed a slight reduction of peripapillary RNFL thickness and a larger area of RGC-IPL reduction in each macula (Fig. 1B). One year after that, VA was 20/20 bilaterally, and SAP findings were slightly worse in the right eye and unchanged in the left eye (Fig. 1C). On OCT, there was further thinning of the peripapillary RNFL and of the RGC-IPL in each nasal hemiretina (Fig. 1C). The GP showed slight progression of VF loss, greater in the right eye (Fig. 2B).
To determine RGC-IPL thickness per quadrant (a feature not available on the OCT), raw data were exported to a personal computer and analyzed using Orion OCT image analysis software (Orion; Voxeleron LLC, Pleasanton, CA). These values were calculated in a circular fashion, according to the Early Treatment Diabetic Retinopathy Study, but rotated (45°) to provide quadrantic measurements respecting the vertical and horizontal meridians. After excluding the fovea, values were calculated for the inner and outer segments of each quadrant. A comparison of the first and last OCT measurements showed RGC-IPL reduction in the 4 nasal quadrantic measurements ranging from 11% to 34.

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