Purpose To evaluate peripapillary retinal nerve fiber layer (RNFL) thickness in cynomolgous monkey eyes with an elevated intraocular pressure (IOP) over 5-year period of time, and to compare with the non-glaucomatous monkey eyes by using Spectral Domain Optical Coherence Tomography (SD-OCT).
Methods The study comprised 10 eyes of 5 cynomolgous monkeys, in which 5 eyes had been induced elevated IOP for 5 years by applications of argon laser to the trabecular meshwork. The other 5 contralateral intact eyes were served as control. Peripapillary RNFL thickness were determined with high-resolution SD-OCT (Spectralis OCT, Heidelberg Engineering).
Results The peripapillary RNFL were divided into six sections: Nasal (N), Nasal-Superior (NS), Nasal-Inferior (NI), Temporal (T), Temporal-Superior (TS) and Temporal-Inferior (TI). The general RNFL thickness of glaucomatous eyes (52.6±22.9µm) is significantly thinner than the control eyes (94.4±6.1µm)(P<0.05). To compare with the control eyes, RNFL is significantly thin in N, NS, NI, TS and TI sections (P<0.05), but not in T section (P>0.05). The thinning of the RNFL is negatively correlated with IOP level. The most correlated one is the NS section (r=-0.78, P=0.008).
Conclusions This study shows that the RNFL is severely damaged in a five year period time with elevated IOP. However, the temporal section of the peripapillary RNFL, which correspond to the papillo-macular bundle, is still survived. Thinning of the RNFL is correlated with IOP elevation, especially the Nasal-Superior section of the peripapillary RNFL.