Enhancement of scleral macromolecular permeability with prostaglandins.
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PURPOSE: It is proposed that the sclera is a metabolically active and pharmacologically responsive tissue. These studies were undertaken to determine whether prostaglandin exposure can enhance scleral permeability to high-molecular-weight substances. METHODS: Topical prostaglandin F2 alpha (PGF2 alpha) was administered to monkeys to determine if this altered the amount of scleral matrix metalloproteinases (MMPs). Experiments also were performed to determine whether the prostaglandin F (FP) receptor and gene transcripts are expressed in normal human sclera. Permeability of organ-cultured human sclera following prostaglandin exposure then was studied and the amount of MMP released into the medium measured. Finally, the permeability of human sclera to basic fibroblast growth factor (FGF-2) was determined following prostaglandin exposure. RESULTS: Topical prostaglandin administration that reduced scleral collagen also increased scleral MMP-1, MMP-2, and MMP-3 by 63 +/- 35%, 267 +/- 210%, and 729 +/- 500%, respectively. FP receptor protein was localized in scleral fibroblasts, and FP receptor gene transcript was identified in sclera. Exposure to prostaglandin F2 alpha, 17-phenyltrinor, PGF2 alpha, or latanoprost acid increased scleral permeability by up to 124%, 183%, or 213%, respectively. In these cultures, MMP-1, MMP-2, and MMP-3 were increased by up to 37%, 267%, and 96%, respectively. Finally, transscleral absorption of FGF-2 was increased by up to 126% with scleral exposure to latanoprost. CONCLUSIONS: These studies demonstrate that the sclera is metabolically active and pharmacologically responsive to prostaglandins. Further, they demonstrate the feasibility of cotreatment with prostaglandin to enhance transscleral delivery of peptides, such as growth factors and high-molecular-weight substances, to the posterior segment of the eye. (+info)
Surgical outcomes of deep sclerectomy with collagen implant.
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We evaulated the effectiveness and adverse effects of deep sclerectomy with collagen implant (DSCI), which is a kind of nonpenetrating filtering surgery. In this retrospective study, DSCI was performed in 15 eyes of 11 glaucoma patients. An trabeculo-Descemet's membrane (TDM) window is created by a deep sclerokeratectomy, and the collagen implant is placed in the sclera bed under a superficial flap (deep sclerectomy with collagen implant). In 3 of 15 eyes the DSCI was intraoperatively converted to conventional filtering surgery for a large perforation of the TDM. These eyes were not included in the results of the surgical outcomes. The mean age of the patients was 50.3 +/- 14.4 years, and the mean follow-up period was 11.1 +/- 5.9 months. A diagnosis of chronic open angle glaucoma was made in 7 eyes and a diagnosis of secondary glaucoma in 5 eyes. The mean preoperative IOP was 25.8 +/- 11.9 mmHg, the immediate postoperative IOP was 6.4 +/- 2.9 mmHg, and at the final follow-up, the IOP was 11.9 +/- 2.5 mmHg. The IOP in 5 eyes was under 6 mmHg temporarily. However, there was no serious complication such as shallow anterior chamber. DSCI is considered to be a good surgical procedure that has similar surgical outcomes to a conventional trabeculectomy without serious complications. (+info)
Short term surgical outcomes of modified deep sclerectomy with catgut implant.
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We compared the effectiveness of and complications resulting from modified deep sclerectomy with catgut implant (modified-DSCI) with those of standard deep sclerectomy with collagen implant (DSCI) in the short term following surgery. In this retrospective study, standard-DSCI was performed on thirteen patients (17 eyes), and modified-DSCI was performed on seven patients (11 eyes). After dissection of a 5x5 mm sized superficial scleral flap, a 3x4 mm sized rectangular deep scleral flap was constructed in DSCI and a 2x3 mm sized triangular deep scleral flap in modified DSCI. A collagen implant was placed on the scleral bed in DSCI and # 0 CHROMIC Catgut Absorbable Suture was used in modified DSCI. The mean follow up was 11.0+/-6.1 months in DSCI and 9.3+/-4.7 months in modified DSCI. The mean preoperative intraocular pressure (IOP) was 38.6+/-10.9 mmHg in DSCI and 34.8+/-8.6 mmHg in modified DSCI. In the DSCI group, the IOP was 13.4+/-3.0 mmHg at final follow up, and was 11.4+/-3.2 mmHg in the modified DSCI group. The number of Nd:YAG goniopuncture was 3 cases (25%) in the modified DSCI group, and 3 cases (21.4%) in the DSCI group. The number of intraoperative microperforations was 3 in the DSCI group and 2 in the modified DSCI group. Temporary hypotony was encountered in 8 eyes (57.1%) of the DSCI group and 4 eyes (50%) of the modified DSCI group. There was no significant difference observed between the two groups in regards to the effectiveness or rate of complications seen during short term follow up. (+info)
Studies of aqueous humor dynamics in man. IV. Effects of pilocarpine upon measurements in young normal volunteers.
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The acute effects of topical pilocarpine 4 per cent, administered to one eye, have been studied in replicate experiments in young volunteers. One hour after medication administration the intraocular pressure was significantly lower. The magnitude of the reduction exceeded that predicated from the significant increase of true facility of outflow. This is explained by the observation of a significant reduction of calculated aqueous humor flow. Pilocarpine caused a significant increase of pseudofacility, a clinically useful drug effect not previously reported. One hour after medication administration, measured episcleral venous pressure was not different from the pretreatment level. (+info)
The characterization of the hexokinases in several tissues of the calf eye.
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Several tissues from the calf eye were studied so as to determine the characteristics of the hexokinases in each tissue. The corneal stroma, sclera, and vitreous body are devoid of measurable hexokinase activity. The tissue specific activities decrease in the following order: retina, ciliary body, corneal endothelium, lens capsule-epithelium, corneal epithelium, and lens cortex-nucleus. Each tissue possesses Types I and II hexokinase in varying proportions in the soluble and insoluble fractions; latent hexokinase is Type I in all tissues except the retina in which both Types I and II are found in the latent fraction. No hexokinase Type IIa, III, or IV is found in any ocular tissue. Michaelis constants for glucose and MgATP= are similar to those found in extraocular tissues. Except for retinal hexokinase, ocular hexokinases are quite similar to extraocular hexokinases. The activity of retinal hexokinase varies greatly and abruptly with time and with change in buffer composition; in the absence of Na2EDTA, glucose, and -SH compounds, there is a rapid deactivation of hexokinase and a shift of the soluble to the insoluble form. The relevance of these findings to glycolysis in each tissue is discussed. (+info)
Pathology of cyclodiode laser: a series of nine enucleated eyes.
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AIM: To study the histological effects of cyclodiode laser treatment in humans, and to compare these findings with the clinical course, treatment response, complications, and indications for enucleation. METHOD: Detailed histological examination of nine enucleation specimens was undertaken in conjunction with a retrospective review of patient case notes. RESULTS: Retreatments had been undertaken in three cases. Although all globes showed damage to pars plicata, intact ciliary processes within the treatment zone were present in all cases. Pars plana injury was also noted in two thirds of cases. Inflammation was mild. Ciliary epithelial proliferation was seen in most cases with increasing time following treatment, in a disorganised pattern, without replication of the ciliary epithelial bilayer. No regeneration of the ciliary processes with fibrovascular cores was found. The three patients with good IOP control at enucleation had all had multiple diode treatments. Neither phthisis nor sympathetic ophthalmia was seen. CONCLUSIONS: Diode laser cyclophotocoagulation produces very characteristic injury to pars plicata, which frequently extends into pars plana, but with only mild persisting inflammation. Ciliary processes are, however, frequently spared within the treatment zone and may account for early or late treatment failure. (+info)
Limited macular translocation with scleral retraction suture.
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BACKGROUND/AIMS: Macular translocation with scleral imbrication is a new technique for treating subfoveal choroidal neovascular membranes (CNV). This procedure shortens the sclera but may result in a minimal decrease in the internal circumference of the globe and limits the amount of foveal displacement. The authors propose a new scleral retraction suture aimed at decreasing the internal circumference of the globe in an effort to increase foveal displacement. METHODS: Using a cadaver model, they compared the amount of scleral shortening using a standard scleral imbrication technique and a modified three suture scleral retraction technique. Sections of the globes were digitised and specialised software was used to estimate the amount of scleral shortening. Three patients with subfoveal choroidal neovascularisation underwent limited macular translocation using pars plana vitrectomy and macular detachment with the modified scleral suture technique. The main outcome measures were visual acuity, foveal displacement, and complications. RESULTS: In the cadaver model, the scleral retraction suture resulted in a flatter internal scleral fold compared to the standard suture technique and created approximately 890 microm of effective scleral shortening. In the patients who underwent macular translocation and laser photocoagulation of the CNV, visual acuity improved in two patients and worsened in one patient. The range of foveal displacement was 1400-2400 microm. CONCLUSION: The foveal displacements achieved in this limited study compared to median displacement previously published using standard suture techniques demonstrates that the scleral retraction suture technique may be a useful adjunct to limited macular translocation. The advantage of this type of suture in conjunction with translocation may depend on the effective scleral shortening offered by this retraction suture. (+info)
The sclera, the prion, and the ophthalmologist.
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Prions have emerged in the past 5 years as serious transmissible infective agents. Ocular tissue transplantation has come under scrutiny after potential infected tissue was transplanted into healthy patients. In this review we examine the evidence for the risk of transmission of prions after scleral transplantation and explore alternative materials that may be used in ocular surgery. (+info)