ABSTRACT
PURPOSE@#We explored changes in photoreceptor function and histology in an iodoacetic acid (IAA)-induced model of feline retinal degeneration.@*METHODS@#From January to October 2014, we studied 11 adult felines (22 eyes) over 2 years of age divided into two groups (two in a control and nine in an IAA group). The mean body weights of these two groups were 1.75 ± 0.35 and 1.61 ± 0.19 kg, and the male:female sex ratios 1:1 and 2:7, respectively. Electroretinograms (ERGs) were obtained before injection and at 1–4 week post-injection (20 mg/kg IAA). Standard paraffin retinal sections were stained with hematoxylin/eosin and other sections subjected to immunohistochemistry. We histologically evaluated the outer nuclear layer, and photoreceptor cone and rod cells.@*RESULTS@#In ERGs of the IAA group, both the rod and cone mean b wave amplitudes decreased significantly from week 1 to week 4 after injection (27.43, 29.41, 64.17, and 56.03; and 61.04, 51.25, 131.36, and 136.68 µV, respectively) compared to baseline (322.48 and 610.00 µV respectively) (p < 0.01). Optical microscopy revealed a significant decrease in the cell count of the outer nuclear retinal layer (16.83 ± 0.89 in the control and 11.98 ± 3.55 in the IAA groups, p < 0.01). Fluorescence microscopy revealed a significant reduction in the mean area per unit length of the rod cell layer (35,225.67 ± 2,477.02 and 14,903.62 ± 2,319.65 in the control and IAA groups, p < 0.01), but not in the cone cell count (26.16 ± 1.34 and 23.98 ± 6.16 in the control and IAA groups, p = 0.075).@*CONCLUSIONS@#ERGs revealed that functional b wave amplitudes fell after IAA-induce retinal degeneration in felines; histology showed that this was accompanied by reductions in the numbers of outer nuclear layers and rod cells. IAA induces photoreceptor degeneration in felines; further study is necessary.
ABSTRACT
PURPOSE: To investigate the change of retinal volume according to anterior segment refractive power using contact lens by spectral domain optical coherence tomography (SD-OCT). METHODS: The retinal volume was measured using a SD-OCT (Heidelberg retinal angiography Spectralis + OCT, Heidelberg Engineering, Heidelberg, Germany) in 60 subjects without any underlying disease. The same examiner performed a 31-section macular volume-scan at 240 µm intervals, re-measured the same area by changing the refractive power of the anterior segment by wearing soft contact lenses of +6.0 diopters and −6.0 diopters. By using the ImageJ software to calculate the cross-sectional area and of the cross-sectional area and the volume was measured. RESULTS: The mean age of the participants was 25.6 ± 1.5 years and the mean axial length was 25.7 ± 1.57 mm. The volume of the posterior pole retina measured without the contact lens was 13.48 ± 0.05 and the mean volume of the retina measured with +6.0 diopter and −6.0 diopter contact lens in the same patient was 13.47 ± 0.07 mm³ and 13.48 ± 0.05 respectively. The mean volume was significantly lower(p = 0.036) in the measurement with the +6.0 diopter lens than in the measurement without the lens, and the mean volume was significantly higher in the measurement with the +6.0 diopter lens (p = 0.042). The change in retinal thickness was increased with longer axial length (r = 0.32, p < 0.05), but the central foveal thickness did not correlate with anterior corneal power (p = 0.463). CONCLUSIONS: The volume of the retina measured using the SD-OCT is affected by the refractive power of the anterior segment and the axial length. Therefore, it is necessary to consider the change of refractive index because it can change the retinal volume measured by SD-OCT.