POSTERIOR SEGMENT INJURIES IN OPERATION IRAQI FREEDOM AND OPERATION ENDURING FREEDOM: 2001 to 2011.

BACKGROUND/PURPOSE: To characterize the nature of posterior segment ocular injuries in combat trauma. METHODS: Eyes in the Walter Reed Ocular Trauma Database were evaluated for the presence of posterior segment injury. Final visual outcomes in open-globe versus closed-globe injuries and by zone of injury and the types of posterior segment injuries in open-globe versus closed-globe injuries were assessed. RESULTS: Four hundred fifty-two of 890 eyes (50.8%) had at least one posterior segment injury. The mechanism of injury was most commonly an improvised explosive device in 280 (62.0%) eyes. Sixty-one patients (13.5%) had a Zone I injury, 50 (11.1%) a Zone II injury, and 341 (75.4%) a Zone III injury. Patients with Zone I injuries were more likely to have a final visual acuity of 20/200 or better compared with patients with either a Zone II (P < 0.001) or Zone III injury (P = 0.007). Eyes with a closed-globe injury were more likely to have a final visual acuity of 20/200 or better compared with those with an open-globe injury (P < 0.001). Furthermore, closed-globe injury compared with open-globe injury had a lower risk of vitreous hemorrhage (odds ratio 0.32, P < 0.001), proliferative vitreoretinopathy (odds ratio 0.14, P < 0.001), and retinal detachment (odds ratio 0.18, P < 0.001) but a higher risk of chorioretinal rupture (odds ratio 2.82, P < 0.001) and macular hole (odds ratio 3.46, P = 0.004). CONCLUSION: Patients with combat ophthalmic trauma had similar posterior segment injury patterns to civilian trauma in open-globe versus closed-globe injuries. Zone II and III injuries were associated with a worse visual prognosis.

Evaluation of the vitreous chamber depth: An assessment of correlation with ocular biometrics.

Purpose: The mechanism of ocular growth eludes us and research on vitreous chamber depth (VCD) is lacking. The purpose of this study was to evaluate the role of VCD and its ratio to axial length (AL) in relation to ocular biometry. Methods: This retrospective study of patients planned for cataract surgery was performed at a tertiary center. Data regarding AL, anterior chamber depth (ACD), lens thickness (LT), and central corneal thickness (CCT) of 640 eyes was noted. Anterior segment (AS) was measured as sum of CCT, ACD, and LT, while VCD was calculated as the difference between AL and AS. Correlation of VCD and VCD: AL with ocular biometry was the primary outcome measure. Three groups were formed on the basis of AL and Pearson correlation coefficient (R) was applied. Results: Mean VCD was 15.38+/-1.14 mm. Mean VCD: AL was 0.66+/-0.02. VCD had a very strong relation with AL (R = 0.9, P < 0.001) only, whereas VCD: AL had a good--strong relation with AL (R = 0.5, P < 0.001), AS (R = 0.7, P < 0.001), ACD (R = 0.3, P < 0.001), and LT (R = 0.5, P < 0.001). The relation of VCD: AL with AS was very strong across all groups (R ≤ -0.8, P < 0.001 in all groups). 85% of eyes in group with AL <22 mm had VCD: AL <0.67, conversely 85% of eyes with AL >24.5 mm had VCD: AL >0.67. Conclusion: : We found VCD to have the strongest relation with AL. VCD: AL was more consistent and showed a strong relation to ocular biometry across all ALs. This suggests the possible utility of the ratio VCD: AL while evaluating ocular growth, refractive status, and myopia-related complications.

Quantification of Retinal Nonperfusion Associated With Posterior Segment Neovascularization in Diabetic Retinopathy Using Ultra-Widefield Fluorescein Angiography.

BACKGROUND AND OBJECTIVE: To quantify the size and location of nonperfusion associated with posterior segment neovascularization (NV) in proliferative diabetic retinopathy (PDR) using ultra-widefield fluorescein angiography. PATIENTS AND METHODS: Cross-sectional study of 18 eyes with PDR. The total image area, areas of nonperfusion, buds of posterior segment neovascularization (either neovascularization of the disc or elsewhere), and the distances from each bud to the nearest area of nonperfusion and to the disc were measured. RESULTS: Nonperfused areas with associated neovascularization were significantly larger than areas without neovascularization (32.0% ± 5.24% of the retinal image vs. 3.3% ± 0.92%; P < .001) and were more likely to be posteriorly located. Nonperfusion encompassing greater than 23% of the total angiographic image had more associated neovascular buds (9.64 ± 2.16 vs. 0.86 ± 0.29; P < .0001), which were closer to the disc (7.53 mm ± 0.27 mm vs. 9.24 mm ± 0.64 mm; P = .014). CONCLUSION: A threshold size of nonperfusion greater than 23% of the retinal image is associated with posterior segment neovascularization and may serve as an indicator of risk for the development of PDR. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:86-92.].

Distribution of the anterior, posterior, and total corneal astigmatism in healthy eyes.

PURPOSE: To evaluate the magnitude and axis orientation of the anterior, posterior, and total corneal astigmatism in normal healthy eyes of an Iranian population. METHODS: In a prospective cross-sectional study, ophthalmic and anterior segment parameters of 153 healthy eyes of 153 subjects were evaluated by Galilei dual Scheimpflug analyzer. The magnitude and axis orientation [with-the-rule (WTR), against-the-rule (ATR), and oblique] of the anterior, posterior, and total corneal astigmatism measurements (ACA, PCA, and TCA) were compared according to the age, sex, and other ophthalmic parameters. RESULTS: The mean ± SD age of the study population was 30 ± 5.9 years. The mean magnitude was 1.09 ± 0.76 diopters (D) for ACA, 0.30 ± 0.13 D for PCA, and 1.08 ± 0.77 D for TCA. Males had a significantly higher magnitude of PCA than females (p = 0.041). Most eyes had a WTR anterior astigmatism and an ATR posterior astigmatism. The WTR astigmatism had a higher mean magnitude compared to the ATR and oblique astigmatism in all the astigmatism groups, with a significant difference in the ACA and TCA groups (p < 0.05). PCA magnitude exceeded 0.50 D in only 7.8% of the subjects. ACA, PCA, and TCA were significantly correlated with each other and also had a significant correlation with the anterior and posterior maximum corneal elevation measurements (p < 0.001). CONCLUSION: The results of this study although are limited due to the small number of participants and confined to our demographics, provided information regarding a population that was not described before and may be helpful in obtaining optimum results in astigmatism correction in refractive surgery or designing new intraocular lenses.

Influence of posterior corneal astigmatism on postoperative refractive astigmatism in pseudophakic eyes after cataract surgery.

BACKGROUND: To examine the influence of posterior corneal astigmatism on postoperative refractive astigmatism in pseudophakic eyes after cataract surgery. METHODS: The study enrolled 64 pseudophakic eyes of 50 patients (71.8 ± 9.9 years old, mean ± standard deviation) who had undergone phacoemulsification with non-toric IOL implantation. Refractive astigmatism was measured using an auto ref-keratometer with a 0.01- diopter (D) scale. Two types of corneal astigmatism were calculated using anterior segment optical coherence tomography; keratometric and total corneal astigmatism. Keratometric astigmatism was obtained based on anterior corneal curvature alone and total corneal astigmatism was calculated using both anterior and posterior corneal curvatures. The difference between refractive and corneal astigmatism was computed as the vector difference using 1) refractive and keratometric astigmatism and 2) refractive and total corneal astigmatism. RESULTS: The mean refractive, keratometric, and total corneal astigmatism was 0.92 ± 0.48 D, 0.87 ± 0.44 D, and 0.94 ± 0.46 D, respectively. The difference between refractive and keratometric astigmatism (0.70 ± 0.40 D, mean vector of 0.30 D axis 164°) was significantly larger than the difference between refractive and total corneal astigmatism (0.63 ± 0.38 D, mean vector of 0.12 D axis 137°) (P = .019). CONCLUSIONS: The difference between refractive and total corneal astigmatism, calculated using both anterior and posterior corneal curvatures, was significantly smaller than the difference between refractive and keratometric astigmatism using anterior corneal astigmatism alone, implying that the latter overestimates the true postoperative refractive astigmatism and can cause cylindrical inaccuracy after cataract surgery.

The outcomes of primary scleral buckling during repair of posterior segment open-globe injuries.

OBJECTIVE: To compare visual outcomes of eyes which underwent primary scleral buckling (PSB) treatment during posterior segment open-globe injury (OGI) repair with eyes not treated with PSB. METHODS: We retrospectively reviewed 38 eyes which underwent a posterior segment OGI repair with no preoperative evidence of retinal detachment (RD) at Soroka University Medical Center (1995-2010). 19 (50%) underwent scleral repair alone (control group) and the other 19 eyes were treated with PSB also (PSB group). We compared visual outcomes in these two groups and rates of subsequent postoperative complications. RESULTS: Baseline characteristics of the groups were similar. Compared with the control group, the PSB group had statistically significant lower rates of proliferative vitreoretinopathy (PVR) (5.3% versus 38.4%, P < 0.05) and a trend towards lower rates of RD (15.8% versus 41.1%, P = 0.1). PSB group eyes had a statistically significant improvement of their best distance visual acuity (BDVA) with lower means of final BDVA-grade (P < 0.05) and logMAR vision (P < 0.05). Eyes in the control group had no improvement in these parameters. CONCLUSION: PSB procedure during posterior segment OGI repair may decrease the risk of subsequent retinal complications and improve final visual outcome.

Biomechanics of the posterior eye: a critical role in health and disease.

The posterior eye is a complex biomechanical structure. Delicate neural and vascular tissues of the retina, choroid, and optic nerve head that are critical for visual function are subjected to mechanical loading from intraocular pressure, intraocular and extraorbital muscles, and external forces on the eye. The surrounding sclera serves to counteract excessive deformation from these forces and thus to create a stable biomechanical environment for the ocular tissues. Additionally, the eye is a dynamic structure with connective tissue remodeling occurring as a result of aging and pathologies such as glaucoma and myopia. The material properties of these tissues and the distribution of stresses and strains in the posterior eye is an area of active research, relying on a combination of computational modeling, imaging, and biomechanical measurement approaches. Investigators are recognizing the increasing importance of the role of the collagen microstructure in these material properties and are undertaking microstructural measurements to drive microstructurally-informed models of ocular biomechanics. Here, we review notable findings and the consensus understanding on the biomechanics and microstructure of the posterior eye. Results from computational and numerical modeling studies and mechanical testing of ocular tissue are discussed. We conclude with some speculation as to future trends in this field.

Accommodative movements of the vitreous membrane, choroid, and sclera in young and presbyopic human and nonhuman primate eyes.

PURPOSE: We report, for the first time to our knowledge, dynamic movements of the vitreous membrane and peripheral choroid during accommodation, and age-related changes in the anterior sclera. METHODS: We studied 11 rhesus monkeys (ages 6-27 years) and 12 human subjects (ages 19-65 years). Accommodation was induced pharmacologically in human subjects and by central electrical stimulation in the monkeys. Ultrasound biomicroscopy, endoscopy, and contrast agents were used to image various intraocular structures. RESULTS: In the monkey, the anterior hyaloid membrane bows backward during accommodation in proportion to accommodative amplitude and lens thickening. A cleft exists between the pars plicata region and the anterior hyaloid membrane, and the cleft width increases during accommodation from 0.79 ± 0.01 mm to 1.01 ± 0.02 mm in young eyes (n = 2, P < 0.005), as fluid from the anterior chamber flows around the lens equator toward the cleft. In the older eyes the cleft width was 0.30 ± 0.19 mm, which during accommodation increased to 0.45 ± 0.20 mm (n = 2). During accommodation the ciliary muscle moved forward by approximately 1.0 mm, pulling forward the choroid, retina, vitreous zonule, and the neighboring vitreous interconnected with the vitreous zonule. Among the humans, in the older eyes the scleral contour bowed inward in the region of the limbus, compared to the young eyes. CONCLUSIONS: The monkey anterior hyaloid bends posteriorly during accommodation in proportion to accommodative amplitude and the sclera bows inward with increasing age in both species. Future descriptions of the accommodative mechanism, and approaches to presbyopia therapy, may need to incorporate these findings.

Shape change of the vitreous chamber influences retinal detachment and reattachment processes: is mechanical stress during eye rotations a factor?

PURPOSE: We aim to understand how mechanical causation influences retinal detachment and reattachment processes. In particular, myopes suffer retinal detachment more frequently than emmetropes, and following a retinal detachment, scleral buckling promotes retinal reattachment. We test the hypothesis that stresses arising from saccadic eye rotations are involved in the processes, and that the alteration in the stress due to the change in the vitreous chamber geometry is sufficient to explain the phenomena. METHODS: The vitreous chamber of the eye has an approximately spherical shape and it is filled with vitreous humor. We developed a mathematical model, treating the vitreous chamber in emmetropic and myopic eyes as a spheroid and in eyes subjected to scleral buckling as a sphere with a circumferential indentation. We assume that the eye performs prescribed small-amplitude, periodic, torsional rotations and we solve semi-analytically for the fluid pressure, velocity, and stress distributions. RESULTS: The shape of the vitreous chamber has a large effect on the retinal stress. The vitreous and the retina of a highly myopic eye continuously experience shear stresses significantly higher than those of an emmetropic eye. An eye fitted with a scleral buckle experiences large stress levels localized around the buckle. CONCLUSIONS: Our results provide a mechanical explanation for the more frequent occurrence of posterior vitreous detachment and retinal detachment in myopic eyes. To understand how the stress distribution in a buckled eye facilitates reattachment, an additional model of the details of the reattachment process should be coupled to this model.

[Myopic traction maculopathy - vitreoretinal traction syndrome in high myopic eyes and posterior staphyloma]. / Traktive myope Makulopathie - vitreoretinales Traktionssyndrom bei hoher Myopie und hinterem Staphylom.

The pathology of the posterior pole in high myopic eyes is characterised by scleral thinning and staphyloma associated with structural changes of the retina. Epiretinal membranes and epiretinal traction together with partial separation of the ILM result in myopic foveoschisis and posterior tractional detachment with myopic macular holes. Foveal detachment and retinoschisis in highly myopic eyes may resolve after vitrectomy with ILM peeling: however, there is a considerable risk for the development of macular hole formation. Skleral buckling surgery is currently regaining interest and allows one to reduce the tractional forces in selected cases. While reading visual acuity is usually not regained after macular hole development, prophylactic measures should be considered for the fellow eye. Vitreous surgery might have a rationale as prophylactic treatment for highly myopic eyes at high risk of macular hole development; however, this needs to be weighed against possible surgical complications.

Effect of induced myopia on scleral myofibroblasts and in vivo ocular biomechanical compliance in the guinea pig.

PURPOSE: To examine the effect of induced myopia on scleral myofibroblast populations and in vivo ocular biomechanical compliance. METHODS: One-week-old guinea pigs were monocularly deprived (MD) of form vision for 2 weeks. Ocular biomechanical compliance was measured in both eyes of anesthetized animals by increasing the intraocular pressure (IOP) to 50 mm Hg for 1 hour, while A-scan ultrasound measures were made every 10 minutes to investigate the change in axial length. The total cell population and myofibroblast subpopulation of the posterior 100° of the sclera was determined with immunohistochemical techniques. RESULTS: The vitreous chamber depth (VCD) of MD and contralateral control eyes showed significant elastic expansion on increasing the IOP, compared with that of the nonmanipulated normal eyes. The creep response of the VCD in response to increased IOP was initially greater in the normal eyes until eye length was similar to the MD and control eyes. An unexpectedly high proportion of the scleral cell population were myofibroblasts (63.7% ± 1.7%, average ± SEM; n = 30). MD significantly decreased the total number of cells in the region between the optic nerve and 10° nasal (equivalent to myopic crescent location in humans) compared with the number in control or normal eyes, but no significant effect on myofibroblasts or the total number of cells was found elsewhere. CONCLUSIONS: A high proportion of scleral cells have contractile potential. This proportion is unaffected by MD. However, there is a significant difference in the in vivo elastic response of the sclera between MD and normal eyes, suggesting that factors other than number of cells have an effect on axial length.