To test the hypothesis that blunt trauma shockwave propagation may cause macular and peripheral retinal lesions, regardless of the presence of vitreous. The study was prompted by the observation of ...macular hole after an inadvertent BB shot in a previously vitrectomized eye.
The computational model was generated from generic eye geometry. Numeric simulations were performed with explicit finite element code. Simple constitutive modeling for soft tissues was used, and model parameters were calibrated on available experimental data by means of a reverse-engineering approach. Pressure, strain, and strain rates were calculated in vitreous- and aqueous-filled eyes. The paired t-test was used for statistical analysis with a 0.05 significance level.
Pressure at the retinal surface ranged between -1 and +1.8 MPa at the macula. Vitreous-filled eyes showed significantly lower pressures at the macula during the compression phase (P < 0.0001) and at the vitreous base during the rebound phase (P = 0.04). Multiaxial strain reached 20% and 25% at the macula and vitreous base, whereas the strain rate reached 40,000 and 50,000 seconds(-1), respectively. Both strain and strain rates at the macula, vitreous base, and equator reached lower values in the vitreous- compared with the aqueous-filled eyes (P < 0.001). Calculated pressures, strain, and strain rate levels were several orders of magnitude higher than the retina tensile strength and load-carrying capability reported in the literature.
Vitreous traction may not be responsible for blunt trauma-associated retinal lesions and can actually damp shockwaves significantly. Negative pressures associated with multiaxial strain and high strain rates can tear and detach the retina. Differential retinal elasticity may explain the higher tendency toward tearing the macula and vitreous base.
Case-control observational study to evaluate the microvascular and macrovascular changes in patients with hypertension secondary to primary aldosteronism (PA), essential hypertension (EH) and healthy ...subjects. Measurements of arterial stiffness including augmentation index (AIx) and pulse wave velocity (PWV) were assessed using a TensioClinic arteriograph system. Retinal microcirculation was imaged by a Retinal Vessel Analyzer (RVA) and a non-midriatic camera (Topcon-TRC-NV2000). IMEDOS software analyzed the retinal artery diameter (RAD), retinal vein diameters (RVD) and arteriole-to-venule ratio (AVR) of the vessels coming off the optic disc. Thirty, 39 and 35 patients were included in the PA, EH and control group, respectively. The PA group showed higher PWV values compared only with the control group. The mean brachial and aortic AIx values did not show significant difference between groups. In the PA group, the mean RVD and AVR values were significantly lower than in the EH and control groups, whereas the parameters did not differ between the EH and control groups. In conclusion, AVR appears significantly modified in the PA group compared with the EH group and could represent an early and more reliable indicator of microvascular remodeling.
To assess the test-retest variability of central and sectorial macular thickness measurements obtained by Cirrus HD-OCT (Carl Zeiss Meditec, Dublin, CA) in neovascular age-related macular ...degeneration (nAMD).
Macular thickness measurements of nine standard ETDRS subfields were obtained and analyzed. The repeatability of macular thickness measurements by Cirrus HD-OCT was assessed by examining the intrasession within subject standard deviation (Sw), coefficient of repeatability (CR), and coefficient of variation (CV), before and after eyes with retinal segmentation errors were excluded.
Forty-nine nAMD eyes of 49 consecutive patients were included in the study. The CR for the central macular subfield was 42.4 microm (10.5%) and ranged from 12.1 microm (3.7%) for the outer nasal to 41.8 microm (11.4%) for the inner nasal subfields. In a secondary analysis, eyes affected by erroneous detection of inner and outer retinal boundaries (6/49, 12.24%) were excluded. The revised coefficient of repeatability for the central macular subfield was 26.1 microm (8.1%) and ranged from 10.3 microm (3.8%) for the outer superior to 30.2 microm (8.3%) for the inner nasal subfields.
Overall, the test-retest variability of Cirrus HD-OCT is good for the central and sectorial macular subfields, with a low incidence of scan artifacts.
Diabetic macular edema (DME) shows variable clinical characteristics with unpredictable results to local treatment, probably reflecting different phenotypes. The purpose of this study was to evaluate ...the role of structural and functional macular imaging in the characterization of DME patterns.
One hundred fifty-one eyes of 92 diabetic patients with untreated clinically significant macular edema (CSME) underwent best corrected visual acuity (BCVA) determination (logMAR), slit lamp biomicroscopy; fluorescein angiography; optical coherence tomography (OCT; mean central retinal thickness CRT, volume, and DME pattern); fundus autofluorescence (FAF; absent or increased iFAF, single or multiple spots; iFAF area quantification); and microperimetry. Linear correlation, data agreement and three-way analysis of covariance were used for statistics.
Thirty-five (23.2%) eyes had normal FAF; and 116 eyes had iFAF: 48 (31.8%) single-spot iFAF, 68 (45%) multiple-spot iFAF. Retinal sensitivity in areas with iFAF was 11.5±5.3 dB (vs. 15.1±3.9 dB in normal areas, P<0.005). Retinal sensitivity of the central field was 15.1±3.9 dB in normal FAF, 12.4±4.8 dB in single-spot iFAF and 11.4±4.9 dB in multiple-spot iFAF (P<0.05). OCT CRT and volume were not significantly different between the FAF groups. OCT volume correlated to OCT CRT (r=0.68), retinal sensitivity in iFAF (r=-0.50) and BCVA (r=0.42). Cystoid OCT pattern and FA edema patterns correlated with iFAF presence (P<0.0001).
In CSME, FAF correlates better with OCT patterns and central field microperimetry rather than with visual acuity. FAF is a rapid, noninvasive technique that may give new insight into the evaluation of DME. The validity of FAF in the follow-up and treatment outcomes in DME remain to be assessed.
To evaluate the parafoveal cone density in patients with Type 1 diabetes mellitus (DM1).
Adaptive optics retinal images of the photoreceptor mosaic were acquired from 11 DM1 patients (study group) ...and 11 age-matched healthy subjects (control group). Cone density was analyzed, along the horizontal and vertical meridian, at 230-µm, 350-µm, and 460-µm eccentricity from the fovea. Central retinal thickness was measured using a Spectralis spectral-domain optical coherence tomography. A multiple regression model was performed to determine the relationships between the explanatory variables (age, glycohemoglobin level, presence of diabetic retinopathy, duration of diabetes, and central retinal thickness) and cone density.
Patients had a diagnosis of DM1 in the past 9 years to 21 years. Of these, five patients had a diagnosis of no diabetic retinopathy and six had mild nonproliferative diabetic retinopathy. On average, cone density was 10% lower in the study than in the control group at each retinal eccentricity along the horizontal and vertical meridians (analysis of variance, P < 0.001). The central retinal thickness was thicker in DM1 eyes than in the control eyes (278 ± 20 µm and 260 ± 13 µm; P < 0.05). The model explained 61% (P < 0.01) of the variance of cone density in the population, with the variables representing an abnormal glucose metabolism, that is, a higher glycohemoglobin level, the presence of diabetic retinopathy, and a chronic diabetes, having the highest influence on cone density decline.
A subtle decrease of parafoveal cone density was found in DM1 patients in comparison with age-matched control subjects via high-resolution adaptive optics retinal imaging. The cone density decline was moderately associated with a disturbance in the glucose metabolism.
Primary blast injury (PBI) mostly affects air-filled organs, although it is sporadically reported in fluid-filled organs, including the eye. The purpose of the present paper is to explain orbit blast ...injury mechanisms through finite element modeling (FEM).
FEM meshes of the eye, orbit, and skull were generated. Pressure, strain, and strain rates were calculated at the cornea, vitreous base, equator, macula, and orbit apex for pressures known to cause tympanic rupture, lung damage, and 50% chance of mortality.
Pressures within the orbit ranged between +0.25 and -1.4 MegaPascal (MPa) for tympanic rupture, +3 and -1 MPa for lung damage, and +20 and -6 MPa for 50% mortality. Higher trinitrotoluene (TNT) quantity and closer explosion caused significantly higher pressures, and the impact angle significantly influenced pressure at all locations. Pressure waves reflected and amplified to create steady waves resonating within the orbit. Strain reached 20% along multiple axes, and strain rates exceeded 30,000 s(-1) at all locations even for the smallest amount of TNT.
The orbit's pyramidlike shape with bony walls and the mechanical impedance mismatch between fluidlike content and anterior air-tissue interface determine pressure wave reflection and amplification. The resulting steady wave resonates within the orbit and can explain both macular holes and optic nerve damage after ocular PBI.
Background
Retinal detachment (RD) associated with aniridia due to globe rupture (GR) is an uncommon condition with a severe prognosis. Surgical technique must address anterior and posterior segment ...issues secondary to the altered compartmentalization and increased risk for corneal toxicity. The purpose of this paper is to report a series of GR patients undergoing combined pars plana vitrectomy (PPV) and artificial iris diaphragm (AID) implant for the repair of RD associated to aniridia.
Methods
The authors retrospectively reviewed 12 consecutive patients operated on by a single surgeon. Surgery consisted of a standard three-port PPV with extensive bimanual dissection of vitreous base and ciliary body membrane and combined AID implant. Office visits included Snellen visual acuity (VA), intraocular pressure measurement, biomicroscopy and indirect ophthalmoscopy. AID prosthesis included aniridic IOLs, Heimann’s PMMA and silicone diaphragm.
Results
Mean age was 53 years and mean follow-up was 19 months. At the end of follow-up, seven patients gained more than two lines (58.3%), two lost their vision (16.6%) and three were unchanged (25%). Seven patients (58.3%) had a VA better than 20/400 and one (8%) 20/40 vision. Eight patients (66.6%) retained a clear cornea, two (16.6%) had minimal corneal oedema and two (16.6%) corneal decompensation. Implanted prosthesis included two silicone diaphragms, four PMMA diaphragms and six aniridic IOLs. After an average 1.6 operations, the retina was completely attached in six patients (50%), partially attached in four (33.3%) and detached in two (16.6%).
Conclusion
RD associated to GR carries a guarded prognosis both due to RD complexity and hypotony. The combined repair of RD and aniridia after GR offers the advantage of addressing all issues at one time allowing correct eye compartmentalization and better tamponade effect. Successful anatomical and functional results can be achieved although multiple surgeries are often needed.
The purpose of this study was to assess long-term functional and structural retinal changes in patients with neovascular age-related macular degeneration treated with intravitreal 0.5 mg ranibizumab.
...Eighteen patients with neovascular age-related macular degeneration have been evaluated in this retrospective 24-month follow-up study. All patients have been treated with 3 injections of 0.5 mg ranibizumab 1 month apart and retreated according to predefined criteria. At baseline, all patients were subjected to visual acuity, fluorescein angiography, MP1 microperimetry, and Stratus optical coherence tomography. Although visual acuity and optical coherence tomography were repeated 28 +/- 2 days after each injection, MP1 was performed at 6, 12, and 24 months.
Seventeen of 18 and 14 of 18 patients completed 12 and 24 months of follow-up, respectively. Mean retinal sensitivity significantly improved from 3.89 +/- 3.0 dB to 7.33 +/- 4.11 dB at 24 months (P = 0.024). Mean visual acuity improved from 48.67 +/- 8.59 to 59.17 +/- 16.45 at 24 months (P = 0.049). Visual acuity improved to >or=15 letters in 33.3% (6 of 18) of patients and <15 letters in 44.4% (8 of 18); 22.2% (4 of 18) of patients lost <15 letters at 24 months. Five of 13 patients (38.5%) with either an instable or relatively instable fixation at baseline showed improvement of fixation stability at 24 months. Central retinal thickness significantly decreased from 310.5 +/- 85.7 to 232.9 +/- 60.1 at 24 months (P = 0.0001).
Intravitreal injections of 0.5 mg ranibizumab determine progressive improvement of retinal sensitivity until 24 months, although visual acuity levels off after 6 months, suggesting that microperimetry may give additional information about macular function not given by visual acuity alone.
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