Comparison of Normal- and High-Tension Glaucoma: Nerve Fiber Layer and Optic Nerve Head Damage

Purpose: The aim of this study was to investigate differences in the nerve fiber layer and glaucoma-induced structural optic nerve head (ONH) damage in patients with normal- (NTG) and high-tension (HTG) glaucoma. Methods: In this retrospective pair-matched comparative study, 22 NTG and 22 HTG eyes were matched according to the same glaucomatous damage based on rim volume, rim area and disk size, as measured by Heidelberg retinal tomography (HRT III). Visual fields (VF) were assessed by Humphrey perimetry, and nerve fiber layer thickness was determined both by scanning laser polarimetry (GDxVCC) and spectral-domain optical coherence tomography (SD-OCT). Comparisons of all measured parameters were made between NTG and HTG groups. Results: Based on HRT results, both NTG and HTG eyes displayed comparable structural damage to the ONH (NTG/HTG, mean: disk area, 2.30/2.31 mm 2 , p = 0.942; rim area, 1.02/0.86 mm 2 , p = 0.082; rim volume, 0.19/0.17 mm 3 , p = 0.398). NTG eyes had significantly less VF damage than HTG eyes (NTG/HTG, mean deviation: –4.23/–12.12 dB, p = 0.002; pattern standard deviation: 5.39/8.23 dB, p = 0.022). The inferior nerve fiber layer of NTG patients was significantly thicker than that of HTG patients (NTG/HTG, mean: GDx inferior: 53.5/46.3 μm, p = 0.046). SD-OCT revealed a significantly thicker nerve fiber in NTG compared with HTG patients in all quadrants (NTG/HTG, total mean: 72.72/58.45 μm, p = 0.002). Conclusion: At comparable glaucomatous stages, nerve fiber loss was more advanced in HTG patients compared with NTG patients

Effect of upper eyelid blepharoplasty on corneal biomechanical, topographic and tomographic parameters 4 weeks after surgery

Purpose!#!To investigate the effect of 'skin-only' upper eyelid blepharoplasty on corneal biomechanics and central as well as peripheral topographic/tomographic parameters before and 4 weeks after surgery.!##!Methods!#!In a prospective study, the corneal hysteresis (CH) and corneal resistance factor (CRF) were evaluated before and after blepharoplasty. Corneal topographic (maximum simulated keratometry value, inferior-superior value, index of surface variance, index of vertical asymmetry, index of height asymmetry, index of height decentration) and tomographic parameters (corneal thickness, corneal astigmatism and mean 5-mm- and 7-mm-zone keratometry value) were measured by the Pentacam HR. Statistical analysis was performed using a linear mixed model considering correlated data of both eyes.!##!Results!#!This study included 42 eyes of 35 patients (mean age: 64.5 years, range 52-82 years). Four weeks after surgery CH and CRF increased (9.4 ± 2.3 to 10.2 ± 2.2 mmHg and 9.7 ± 2.1 to 10.5 ± 2.2 mmHg) but did not reach statistical significance (P = 0.100 and P = 0.072). A significant increase in central maximum simulated keratometry value (Kmax) from 45.0 ± 2.3 to 45.4 ± 2.2 diopters (D) was observed (P = 0.004). Inferior-superior value (I-S) and index of surface variance (ISV) showed significant changes from 0.32 ± 0.98 to 0.10 ± 0.98 D (P = 0.02) and from 19.98 ± 9.84 to 22.93 ± 11.23 (P = 0.009), respectively. These alterations did not affect the subjective spherical equivalent (-0.09 ± 4.71 to -0.04 ± 4.51 D; P = 0.437) and the best-corrected distance visual acuity of patients (0.11 ± 0.14 to 0.15 ± 0.15 logMAR; P = 0.142). Age, gender and corneal thickness were not correlated with pre and postoperative differences of CH, CRF, corneal compensated IOP, Kmax, corneal astigmatism or I-S.!##!Conclusion!#!The trend of increasing CH and CRF values might indicate a rise of corneal damping capacity. Despite statistically significant differences of Kmax, I-S and ISV, all other tomographical and topographical parameters did not change 4 weeks after surgery. The corneal steepening with a mean change of 0.4 diopters and the decrease of I-S with a mean of 0.22 diopters do not seem to have a clinically relevant effect for blepharoplasty patients in daily practice

Biomechanical and Morphological Differences between the Sclera Canal Ring and a Peripheral Sclera Ring in the Porcine Eye

Aim: To investigate a possible association between the biomechanical load and unload behaviour and the elastin content of the sclera canal ring (SCR) and a superiorly localized sclera ring (SPS) in the porcine eye. Methods: Two sclera rings were trephined from each of 40 porcine eyes, one containing the SCR and the other an SPS. The load and the unload curves were measured in the extension range of 0–2.0 mm by a biomaterial tester. Hysteresis was determined from the area enclosed by the loading and unloading curve. Histochemical staining with resorcin-fuchsin and morphometric analysis of paraffin-embedded sections of both rings were performed to detect the area occupied by elastin fibres. Results: At 1 mm extension, the mean load of the SCR was 0.89 8 0.22 N and that of the SPS 1.13 8 0.19 N, which was not significantly different between both rings (p 1 0.05). Mean hysteresis in the SCR was 1.55 8 0.30 N ! mm and 1.90 8 0.18 N ! mm in the SPS, which was significantly different between both rings (p = 0.01). Mean sclera thickness was 986 _ m in the SCR (range: 900–1,060 _ m) and 971 _ m in the SPS (range: 800–1,200 _ m) without a statistically significant difference between both sclera rings (p = 0.78). The area occupied by elastin fibres was 15.5 8 3.4% in the SCR and 4.5 8 1.5% in the SPS, which was significantly different between both rings (p = 0.0001). Conclusion: Hysteresis in the SCR was significantly lower than in the SPS, indicating a higher elasticity of the SCR in the porcine eye. This effect could be explained by a higher content of elastin in the surrounding ring of the peripapillary optic nerve head providing reversible contraction in cases of intra-ocular pressure variations