Abstract
Purpose: :
To investigate progressive changes of retinal ganglion cell (RGC) function in early normal tension glaucoma (NTG) before and after IOP lowering treatment.
Methods: :
Fifteen NTG glaucoma suspects with mean age 54.9 ±11.8 years (28 eyes) and corrected visual acuity ≥20/20, were followed longitudinally over 6.44 ± 1.07 years, receiving 14.2 ± 2.9 measurements of IOP, Pattern Electroretinogram (PERG) and SAP. After an untreated period, patients received topical treatment for glaucoma based on standard clinical considerations. Rates of PERG/SAP change with time (slopes) for both the untreated and treated conditions were calculated for each eye using bi-linear regression analyses with the time of 1st treated visit as a known break point. IOP measurements were averaged over untreated and treated periods.
Results: :
Medians of untreated and treated measurements were significantly (P<0.001) different for IOP (15.5 mm Hg vs. 14.1 mm Hg) and PERG amplitude slope (-8.4 % /year vs. 0.14% /year), but not for SAP-MD slope (-0.08 dB/year vs. -0.02 dB/year, P = 0.85). In 27 out of 28 eyes, PERG amplitude slopes became less negative after treatment. Eight eyes out of 28 tested (28%) had significant slope improvement after treatment (P<0.001, n=6; P<0.05, n=2). Correlation analysis showed that the steeper the progressive decline of PERG signal before treatment, the larger the magnitude of recovery after treatment (Pearson’s R = -0.83, P<0.001).
Conclusions: :
The results indicate that the PERG may detect progressive RGC dysfunction in early untreated NTG, as well as its potential reversibility after IOP lowering.
Keywords: ganglion cells • intraocular pressure • electroretinography: clinical