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M. L. Goodkin, D. S. Grewal, M. Sehi, D. S. Greenfield; Retinal Ganglion Cell Response to IOP Reduction Following Glaucoma Surgery. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2237.
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The Pattern Electroretinogram (PERG) is a non-invasive method of objectively measuring retinal ganglion cell (RGC) function. Preliminary evidence suggests that PERG may measure reversal of RGC dysfunction in glaucomatous eyes after pharmacologic reduction in intraocular pressure (IOP). This study was undertaken to quantify the RGC response to IOP reduction following glaucoma surgery.
Prospective cohort study of patients uncontrolled on maximal medical therapy, or with progression of glaucomatous optic neuropathy. Patients requiring trabeculectomy or aqueous drainage device who met eligibility criteria were recruited. Eyes with visual acuity less than 20/30, ocular disease other than cataract or glaucoma, or unreliable standard automated perimetry (SAP) were excluded. All patients underwent complete ocular examination, blood pressure, IOP, SAP, and PERG before surgery and at 3 months post-surgery. Each measure of PERG was an average of 600 artifact-free signal registrations. Paired samples t-test, Pearson and Spearman correlation coefficients were calculated.
40 patients (mean age 69.7±12.8 years) were enrolled. Twenty-nine patients (72.5%) underwent trabeculectomy with antifibrosis therapy; 11 patients (27.5%) underwent glaucoma drainage implant surgery. Mean postoperative IOP (10.5±4.8mmHg) and number of glaucoma medications (0.7±1.1) were significantly (p<0.001) reduced compared to prior to surgery (20.7±8.6mmHg and 3.0±1.1, respectively). Mean postoperative PERG amplitude (0.5±0.2) was significantly (p=0.02) increased compared to mean preoperative PERG amplitude (0.4±0.2). Mean postoperative MOPP (52.9±6.7mmHg) was significantly (p<0.001) increased compared to mean preoperative MOPP (44.4±10.8 mmHg). Mean preoperative PERG phase (1.8±0.2rad), SAP MD (-10.7±7.6 dB), and PSD (7.7±3.8 dB) were unchanged (p=0.2-0.7) following surgery. No correlation (p=0.2-0.8) was identified between change in PERG amplitude and preoperative IOP, MOPP, SAP MD or PSD, age, gender, race, eye, or type of surgery.
Our data demonstrates that reversal of RGC dysfunction occurs following surgical reduction in IOP and may be quantified using PERG.
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