Short Wavelength (Blue) Light Is Protective for Lens-Induced Myopia in Guinea Pigs Potentially Through a Retinoic Acid-Related Mechanism.

Purpose: To investigate the effect of short-wavelength light (SL) on guinea pigs with lens-induced myopia (LIM) and the possible retinoic acid (RA)-related mechanisms. Methods: Two-week-old guinea pigs (n = 60) with monocular -5D lenses were reared under white light (WL, 580 lux) or SL (440 nm, 500 lux). The left eyes were uncovered as control. Refractive error (RE) and axial length (AL) were measured at baseline, one week, two weeks, and four weeks after intervention. Retinal RA was measured from four guinea pigs after two and four weeks of treatment with HPLC. Two-week-old guinea pigs (n = 52) with monocular -5D lens were fed with either RA or its synthesis inhibitor citral every third day in the morning, and half from each group were reared under WL or SL conditions. RE and AL were recorded at baseline and two and four weeks after intervention. Retinal RA was measured after four weeks of intervention. Results: At the end of treatment, guinea pigs exposed to SL were less myopic than to WL (2.06 ± 1.69D vs. -1.00 ± 1.88D), accompanied with shorter AL (P = 0.01) and less retinal RA (P = 0.02). SL reduced retinal RA even after exogenous RA supplementation (P = 0.02) and decelerated LIM compared to WL (1.66 ± 1.03D vs. -3.53 ± 0.90D). Citral slowed ocular growth, leading to similar RE in W+CI and S+CI groups (3.39 ± 1.65D vs. 5.25 ± 0.80D). Conclusions: Overall, SL reduced LIM in guinea pigs, even in those supplemented with oral RA, accompanied by reduced retinal RA levels. Oral RA accelerated eye elongation, but citral equally decelerated eye elongation under SL and WL with no significant retinal RA reduction.

Optic nerve head cupping in glaucomatous and non-glaucomatous optic neuropathy.

BACKGROUND: Enlargement of optic disc cupping is seen both in glaucoma and in neurological disorders. We used enhanced depth imaging with spectral-domain optical coherence tomography to differentiate glaucoma from non-glaucomatous optic neuropathy. METHODS: The optic discs were scanned in this prospective comparative study, and the lamina cribrosa (LC) thickness and anterior laminar depth (ALD) in the central, superior and inferior optic nerve head, and peripapillary choroidal thicknesses, were measured. RESULTS: There were 31 eyes of 31 patients with severe glaucoma and 33 eyes of 19 patients with non-glaucomatous cupping. Eyes of 29 healthy controls were also enrolled. There was no significant difference in the cup-to-disc ratio and in the average peripapillary nerve fibre layer thickness between the glaucoma and non-glaucomatous cupping groups (p>0.99). The average peripapillary choroidal thickness was thinner in glaucoma eyes than in the control eyes after adjusting for age and axial length. Glaucomatous and non-glaucomatous eyes had greater ALD and thinner LC than the control eyes (p<0.001 for both). ALDs of glaucoma eyes were deeper than non-glaucomatous eyes (p=0.01 for central ALD) when age, axial length and peripapillary choroidal thickness were included in the linear mixed model. Prelaminar thickness and LC thickness of glaucoma eyes were not different from non-glaucomatous eyes after adjusting. CONCLUSION: Deeper ALD was observed in glaucoma than non-glaucomatous cupping after adjusting for choroidal thickness.

Lamina cribrosa depth according to the level of axial length in normal and glaucomatous eyes.

PURPOSE: To compare the lamina cribrosa (LC) depth of the optic nerve head in normal and glaucomatous eyes over a wide range of axial length (AXL). METHODS: A total of 402 eyes, including 210 normal and 192 glaucomatous eyes, were imaged by spectral domain optical coherence tomography. Normal and glaucomatous eyes were each divided into three subgroups according to the level of AXL; long (> 26 mm), mid-level (23-26 mm), and short (< 23 mm). Visual field mean deviation (VF MD), LC thickness, and LC depth were compared between normal and glaucomatous eyes in each of the AXL subgroups. These parameters were also compared between normal and glaucomatous eyes in the three AXL subgroups. Factors associated with LC depth in each AXL subgroup were evaluated by univariate and multivariate regression analyses. RESULTS: A comparison of the three AXL subgroups in normal eyes showed that the LC was thinnest in the long AXL subgroup (short; 189.7 ± 24.1 µm, mid-level; 179.9 ± 34.3 µm, long; 149.2 ± 36.2 µm, p < 0.001), but LC depth did not differ significantly in the three subgroups (short; 527.1 ± 144.4 µm, mid-level; 578.2 ± 163.5 µm, long; 594.4 ± 187.5 µm, p = 0.144). In glaucomatous eyes, glaucoma severity assessed by VF MD did not differ significantly among the three AXL subgroups (short; -6.99 ± 8.50 dB, mid-level; -6.40 ± 7.64 dB, long; -4.61 ± 5.22 dB, p = 0.168). However, LC depth was greater in the long than in the short AXL subgroup (679.5 ± 192.7 µm and 555.9 ± 134.1 µm, respectively, p = 0.004), although neither subgroup differed significantly in LC depth from the mid-level AXL subgroup (611.8 ± 162.3 µm, p = 0.385, p = 0.090). LC thickness was significantly different between normal and glaucomatous eyes (p < 0.001). LC depth was not different between normal and glaucomatous eyes in both short and mid-level AXL subgroups (p = 0.297, 0.222), but differed in the long AXL subgroup (p = 0.022). The presence of glaucoma was associated with greater LC depth only in the long AXL subgroup (p = 0.012). CONCLUSIONS: LC depth may vary according to the level of AXL in glaucomatous eyes with a similar level of glaucoma severity, with the greatest LC depth found in eyes with long AXL. Those findings suggest that glaucomatous optic disc cupping would manifest differently according to the level of AXL.

Topographical Analysis of Non-Glaucomatous Myopic Optic Discs Using a Confocal Scanning Laser Ophthalmoscope (TopSS).

OBJECTIVES: To show normative data of optic discs and the mechanism of glaucoma in people with myopia. DESIGN: Cross-sectional study. PARTICIPANTS: This study investigated 89 Korean adults with myopia but without glaucoma. METHODS: Patients were divided into three groups according to the refractive error: low, moderate, and high; and axial length: normal or below normal length, moderately long, and extremely long. Optic disc variables were obtained by confocal scanning laser ophthalmoscope and compared among groups. RESULTS: The optic disc parameters have a correlation between the refractive error and the optic disc parameters such as average depth, volume below, and half-depth volume. Those parameters also decreased as the axial length increased. The thickness of the volume above decreased significantly as the axial length increased, but a similar relationship was not evident with the refractive error change. In addition, the optic disc parameters were analyzed with respect to the 12 clockwise directions. CONCLUSIONS: Analyses of optic disc parameters provided by TopSS™ revealed the height of the disc decreased as the myopic refractive error and/or axial length increased. The RNFL bundle became compacted in the thinner disc of the myopic population. This could be an explanation for the fragility of the RNFL in the myopic population. The 12 radial section analyses revealed the shallow cupping at the temporal side in the high-myopic, very-long-axis group. The neuroretinal rim (NRR) height significantly decreased at the superior and inferior sides. These findings suggest that the RNFL bundle should be under high mechanical strain in these sectors.

Biometry and spectral domain optical coherence tomography parameters in children with large cupping.

PURPOSE: The purpose of this study is to investigate optic nerve head using spectral domain optical coherence tomography (SD-OCT) in children with large cupping. METHODS: 111 eyes (4-10 years) were divided into three groups according to the cup to disc ratio: group 1, ≤0.3; group 2, 0.4-0.6; and group 3, ≥0.7. The rim area, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume were investigated using SD-OCT (Cirrus HD-OCT, Carl Zeiss, Jena, Germany), and the axial length and anterior chamber depth (ACD) were measured by IOL master (IOL master 500, Carl Zeiss, Jena, Germany). Next, we compared ocular biometry and SD-OCT between the three groups. RESULTS: The mean age of group 1 was 6.48 ± 1.42 years, 7.00 ± 1.75 years in group 2, and 6.63 ± 1.82 years in group 3 (p = 0.370). A significant difference was seen in the spherical equivalent between the groups (p = 0.001). Group 2 had the most myopic refractive errors. As the cup to disc ratio increases, disc area, average cup to disc ratio, vertical cup to disc ratio, and cup volume increase significantly. When the results of ocular biometry and SD-OCT are adjusted for axial length, only disc area showed a significant correlation with cup to disc ratio (ACD: p = 0.473, rim area: p = 0.639, disc area: p = 0.005, and cup volume: p = 0.325). CONCLUSION: Axial length is the key factor determining disc size, which in turn is important for determining cup to disc ratio. Normal children with large cupping should be examined for axial length, myopic refractive errors, and disc size.