Evaluation of Vitreous Substitutes in Managing Complicated Vitreo-retinal Surgeries

Background

Vitreous substitutes presently in use for intraoperative tamponade are perfluorocarbon liquids (PFCL) and for post operative tamponade are silicon oil (SO), sulphur hexafluoride (SF₆) and perfluorocarbon gas (PFC). Several factors are important for a thorough understanding of each of these vitreous substitutes. The absorption or necessity for removal, indications for use (including clinical studies and special surgical methods), additives and complications of use have to be considered.

Methods

Three port standard pars plana vitrectomy was performed in 60 consecutive cases requiring intra-vitreal intervention. PFCL was used intra-operatively in 30 cases (PFCL group and X group). The eyes were implanted with SO (silicon oil subgroup), PFC (C₃F₈ sub-group) and SF₆ (SF₆ sub-group) in twenty cases each. Apart from best corrected visual acuity (BCVA), the retinal status and the longevity of gas when used, changes and reaction in both the anterior and posterior segments were noted.

Result

The difference of postoperative BCVA in the PFCL and non-PFCL groups was statistically significant with p < 0.001. In both the PFCL and non-PFCL groups the difference between preoperative and postoperative BCVA was statistically significant with p < 0.0001. All three vitreous substitutes studied are effective given the case where they had been utilised.

Conclusion

PFCL is invaluable in the management of complicated retinal detachment (RD). Where a vitreous microsurgery is indicated, the visual outcome is good. SF₆ is useful for short-term tamponade. Silicon oil and C₃F₈ are useful for longer tamponade.Key Words: Tamponade, Perfluorocarbon liquids, Silicon oil, Sulphur hexafluoride, Perfluorocarbon gas, Retinal detachment     

5-Fluoro-Uracil and Low Molecular Weight Heparin in the Management of Proliferative Vitreo-retinopathy

Background

Proliferative vitreo-retinopathy (PVR) is the most common cause of failed repair of a primary rhegmatogenous retinal detachment (RRD). The success rates for the surgery of complicated RRD has doubled with improved vitreous techniques from 35–40% to approximately 65–75% at six months. However, despite these advances, recurrent vitreo-retinal traction leads to re-detachment in more than one-fourths of the initially successful cases. The use of adjunctive treatments to prevent cellular proliferation holds promise for the prevention of PVR or recurrences after surgery. One focus has been on the use of intra-vitreal antimetabolites to prevent the occurrence of PVR.

Methods

Thirty patients of complicated retinal detachment associated with PVR, C1 or more were managed by vitreo-retinal (VR) surgery with the addition of 250 μg / ml of 5-fluorouracil (5FU) and 1 IU / ml of low molecular weight heparin (LMWH) to the vitreous infusion. The patients were examined for any evidence of PVR till 180 days as also for any systemic or other ophthalmic complication.

Result

Out of the 30 cases in the study group, 25 (83.34%) cases had retinal settlement at the end of six weeks, which is similar to the outcomes of conventional VR surgery. There was no case of any serious complication.

Conclusion

The addition of LMWH and 5FU did not enhance the outcome of VR surgery.Key Words: Proliferative vitreo-retinopathy, Rhegmatogenons retinal detachment, 5-fluorouracil, Low molecular weight heparin     

Optimizing Staining Protocols for Laser Microdissection of Specific Cell Types from the Testis Including Carcinoma In Situ

Microarray and RT-PCR based methods are important tools for analysis of gene expression; however, in tissues containing many different cells types, such as the testis, characterization of gene expression in specific cell types can be severely hampered by noise from other cells. The laser microdissection technology allows for enrichment of specific cell types. However, when the cells are not morphologically distinguishable, it is necessary to use a specific staining method for the target cells. In this study we have tested different fixatives, storage conditions for frozen sections and staining protocols, and present two staining protocols for frozen sections, one for fast and specific staining of fetal germ cells, testicular carcinoma in situ cells, and other cells with embryonic stem cell-like properties that express the alkaline phosphatase, and one for specific staining of lipid droplet-containing cells, which is useful for isolation of the androgen-producing Leydig cells. Both protocols retain a morphology that is compatible with laser microdissection and yield RNA of a quality suitable for PCR and microarray analysis.     

Differential spectrofluorometry in the human vitreous: blood-retina barrier permeability to fluorescein and fluorescein glucuronide

A method is described for the separate quantitation of fluorescein and fluorescein glucuronide in the vitreous by differential spectrofluorometry. An ocular fluorometer was equppied with monochromatic laser excitation at two rapidly interchangeable wavelengths. The data analysis accounts for absorption of light in the cornea, lens, and extrinsic ocular fluorophores. Examination of seven patients with insulin-dependent diabetes and different degrees of diabetic retinopathy demonstrated that both fluorescein and fluorescein glucuronide enter the eye through the blood-retina barrier. The mean ratio between the permeabilities of fluorescein glucuronide and fluorescein was 0.9 (range, 0.3–1.9). Thus, differences in the molecular size and lipid solubility of the two substances appear to be of little or no importance for their inward penetration of the barrier. No association was found between the relative permeability and the degree of retinopathy.This study was supported by Danish Medical Research Council grant 12-8301 Offprint requests to: M. Larsen