Decreased Choroidal Blood Perfusion Induces Myopia in Guinea Pigs.

Purpose: The development of myopia in guinea pigs can be inhibited by attenuating scleral hypoxia by increasing choroidal blood perfusion (ChBP). In this study, we reduced ChBP through surgical and pharmacological methods to determine the effect on myopia development. We also determined whether ChBP was reduced by quinpirole, a drug that enhances form-deprivation myopia (FDM). Methods: ChBP was reduced in the right eyes of guinea pigs via transection of the temporal ciliary arteries or daily injections of phenylephrine into the inferior peribulbar space for one week during normal ocular growth. Other guinea pigs were subjected to two weeks of monocular FDM-with facemasks, along with daily injections of quinpirole, a dopamine D2 receptor agonist, to enhance the FDM. Changes in refraction, axial length, ChBP, and choroidal thickness (ChT) were measured in both treated and fellow eyes of the treatment and control groups. Scleral hypoxia labeling with pimonidazole adducts and α-smooth muscle actin (α-SMA) protein were also measured. Results: Surgical and pharmacological reduction of ChBP induced myopia development in the treated eyes. These treatments rendered the scleral hypoxia and increased scleral α-SMA expression. Furthermore, quinpirole injections, which increased the magnitude of myopia, augmented the FDM-associated reductions in ChBP and ChT and increased the levels of scleral hypoxia and α-SMA protein. Conclusions: Decreased ChBP in guinea pigs leads to scleral hypoxia and scleral myofibroblast transdifferentiation with increased α-SMA expression, ultimately resulting in myopia development. In future clinical trials, ChBP reduction can serve as a potential biomarker for early detection of myopia development.

Surgical management of dysthyroid diplopia with preservation of the anterior ciliary vascularization: review of ten cases.

PURPOSE: During the surgical correction of dysthyroid diplopia, the risk of ischemia by transection of the anterior ciliary arteries is well-known. In order to avoid this, we modified the classical surgical technique: (1) through the preservation of the vascular pedicles during muscle recession and (2) if necessary, through a plication (instead of a resection) of the ipsilateral antagonist muscle. The objective to be achieved is thus the resolution of the diplopia without ischemic complications. SUBJECTS AND METHODS: We report a prospective series of 10 patients with dysthyroid ophthalmopathy, causing strabismic diplopia, all operated on by the same surgeon (BR) after at least 12 months of euthyroidism. Data collection included: history of previous decompressive surgery, surgical procedure, and oculomotor status before and after surgery. RESULTS: Ten patients (8 females), aged 51 to 74 years (mean age, 58.00 ± 7.62 years), were collected between 2008 and 2012. All patients had one or more vascular risk factors (diabetes, smoking, obesity, high blood pressure). With a follow-up from 16 to 67 months (mean ± SD 27.7 months ± 14.87), surgical outcomes were excellent: diplopia was cured in all cases, with recovery of stereoscopic vision. We had no operative or postoperative complications. CONCLUSIONS: The technique of preservation of the anterior ciliary vascularization, which is particularly justified for these fragile patients, is compatible with moderate muscle recessions. For larger deviations, in which a larger recession might increase the proptosis, it is possible to add a plication of the ipsilateral antagonist. This surgical technique made possible the suppression of the diplopia in all cases.

Accurate course and relationships of the intraorbital part of the ophthalmic artery in the sagittal plane.

INTRODUCTION: Knowledge of variations in the course and distribution of the intraorbital part of ophthalmic artery (OA) is necessary for the diagnosis and treatment of anterior cranial and orbital disorders. MATERIAL: 38 human cadaver dissections to demonstrate the microsurgical anatomy of the intraorbital part of the OA were studied in three stages, considering its neighbourhood with the optic nerve in the sagittal plane. RESULTS: The first part of the OA was located on the inferolateral aspect of the optic nerve in 89.47%. The diameter and the length of the first part of the OA were 1.69+/-0.34 mm and 7.58+/-0.89 mm. 73.68% of the cases crossed the optic nerve superiorly, and 26.31% inferiorly. The diameter and length of the second part of the OA were as 1.52+/-0.29 mm and 4.12+/-0.85 mm. The diameter and length of the third part of the OA were 1.07+/-0.18 mm and 4.12+/-0.85 mm. The first branch of the intraorbital part of the OA was the central retinal artery in 26.31% of the specimens. CONCLUSION: A better understanding of the vascular anatomy of the orbit should allow for the modification of surgical techniques to reduce bleeding during biopsy or excision of orbital structures.

Effects of pars plana vitrectomy on retrobulbar haemodynamics in diabetic retinopathy.

BACKGROUND: The purpose of the present study was to determine the effects of pars plana vitrectomy on retrobulbar haemodynamics in patients with proliferative diabetic retinopathy (PDR). METHODS: Colour Doppler imaging was used for measurement of blood flow velocities and resistive index of the ophthalmic artery (OA), posterior ciliary arteries (PCA) and central retinal artery (CRA) in 14 eyes of 14 patients with PDR before pars plana vitrectomy and at the 1 and 6 months after operation. The patients were also treated by laser photocoagulation before or during surgery. Twenty age- and sex-matched healthy subjects were used as control group. RESULTS: Mean peak systolic velocity and the end diastolic velocity of the CRA in the patients with PDR were lower and the mean resistive index was higher than in those of the control group (P < 0.05). The mean end diastolic velocity of OA in the patients was lower and the mean resistive index was higher than in the control group (P < 0.05). The peak systolic velocity of the OA and the end diastolic velocity of the CRA were significantly increased (P = 0.043 and P = 0.018, respectively) and the mean resistive index of the CRA was significantly decreased after pars plana vitrectomy (P = 0.043). No significant changes were detected among preoperative and postoperative values of peak systolic velocity, end diastolic velocity, and resistive index of the PCA and the mean velocity of the central retinal vein (P > 0.05). CONCLUSIONS: The blood flow velocities of OA and CRA are decreased but the resistive index is increased significantly in patients with PDR. Pars plana vitrectomy in patients with PDR may decrease resistive index and improve blood flow in the CRA.

Neovascularization in the anterior segment of the rabbit eye by experimental anterior ischemia.

PURPOSE: To investigate the effects of anterior ischemia accompanied by neither retinal nor choroidal ischemia on the anterior segment of the eye. METHODS: Both long posterior ciliary arteries in the right eye of 14 rabbits were directly cauterized with an electric coagulator. The eyes were enucleated 1, 2, 4, 7, 9 or 14 days after cauterization, then fixed with 4% paraformaldehyde. Semi-thin sections were studied by light microscopy. Several sections were stained with Griffonia simplicifolia lectin, which bound specifically to mammalian vascular endothelium. Other specimens were examined immunohistochemically for vascular endothelial growth factor (VEGF) protein. The tissue specimens of the first postoperative day were studied for expression of VEGF mRNA by in situ hybridization. RESULTS: Atrophy of the iris and ciliary body was seen after the second postoperative day. Corneal neovascularization appeared after 7 days. Neovascularization on the anterior surface of the iris and in the trabecular meshwork was detected after the ninth postoperative day. The proliferative tissues with newly formed vessels obstructed the iridocorneal angle 14 days after the treatment. There was no histological change in either the retina or choroid. Immunohistochemically, VEGF protein was detected in the epithelial and vascular cells of the iris on the first and fourth postoperative day. Expression of VEGF mRNA was detected in the epithelial cells of the ciliary body on the day following the treatment. CONCLUSIONS: Anterior segment ischemia, when unaccompanied by retinal ischemia, causes neovascularization in the cornea, iris and trabecular tissue.

Anterior segment ischemia after strabismus surgery with microvascular dissection.

Anterior segment ischemia is a rare but well-known complication of extraocular muscle surgery.(1) Several surgical techniques have been used to prevent this complication in high-risk patients. A number of studies have suggested that microvascular dissection and preservation of the anterior ciliary vessels during strabismus surgery may reduce the risk of ischemic complications. (2-4) We present a case in which anterior segment ischemia occurred despite the use of this vessel-sparing technique.

Aqueous vascular endothelial growth factor increases in anterior segment ischemia in rabbits.

Both long posterior ciliary arteries were occluded or the three extraocular muscles were tenotomized to produce anterior segment ischemia in rabbits, and the aqueous levels of vascular endothelial growth factor (VEGF) were measured. The occlusion of both long posterior ciliary arteries led to clinical and histological anterior segment ischemia in varying degrees. The aqueous VEGF levels increased significantly compared with controls on all days examined (Mann-Whitney U test: day 1, P = 0.0039; day 4, P = 0.0065; day 7, P = 0.0039; day 14, P = 0.0104), while the levels at days 7 and 14 decreased significantly compared with those at day 4 (Wilcoxon signed-rank test; day 4 to day 7 and day 4 to day 14, P = 0.0464). In contrast, tenotomy of the three extraocular muscles resulted in no histological changes. The VEGF levels increased significantly compared with controls at day 1 and day 4 decreased significantly compared with those at day 1 (Wilcoxon signed-rank test, P = 0.0499). Aqueous VEGF levels represent the severity of anterior segment ischemia and could be used as an indicator for the extent of ischemia.