Biomedical subjects

J Khadem

Publications and source records attributed to J Khadem.

5 recordsLinked to original sources

PubMed1999

Photodynamic tissue adhesion with chlorin(e6) protein conjugates.

PURPOSE: To test the hypothesis that a photodynamic laser-activated tissue solder would perform better in sealing scleral incisions when the photosensitizer was covalently linked to the protein than when it was noncovalently mixed. METHODS: Conjugates and mixtures were prepared between the photosensitizer chlorin(e6) and various proteins (albumin, fibrinogen, and gelatin) in different ratios and used to weld penetrating scleral incisions made in human cadaveric eyes. A blue-green (488-514 nm) argon laser activated the adhesive, and the strength of the closure was measured by increasing the intraocular pressure until the wound showed leakage. RESULTS: Both covalent conjugates and noncovalent mixtures showed a light dose-dependent increase in leaking pressure. A preparation of albumin chlorin(e6) conjugate with additional albumin added (2.5 protein to chlorin(e6) molar ratio) showed significantly higher weld strength than other protein conjugates and mixtures. CONCLUSIONS: This is the first report of dye-protein conjugates as tissue solders. These conjugates may have applications in ophthalmology.

Chlorophyllides↗

PubMed1998

Relative strength of photodynamic biologic tissue glue in penetrating keratoplasty in cadaver eyes.

PURPOSE: To compare the relative strength of photodynamic biologic tissue glue (PBTG) with that of 10-0 nylon sutures in closing penetrating keratoplasty (PKP) wounds in cadaver eyes. SETTING: Corneal Research Laboratory, University of Chicago, Chicago, Illinois, USA. METHODS: A 7 mm central corneal trephination was performed on 8 recently enucleated human eyes. Each corneal button was removed and then resutured in its original position, using 4 interrupted 10-0 nylon cardinal sutures and PBTG (n = 7) or 16 interrupted 10-0 nylon sutures (n = 1). Wound leak and incisional bursting pressures were determined. RESULTS: The average pressure at which wound leak and iris prolapse occurred was 124 mm Hg (range 70 to 180) and 185 mm Hg (range 90 to 300), respectively. The pressure required to create wound leak increased as the time between glue application and pressurization of the globe lengthened (mean 22 minutes, range 5 to 60 minutes), indicating that the bonding and stability of the adhesive increased with time. In contrast, the control eye developed wound leak at 70 mm Hg and iris prolapse at 300 mm Hg. CONCLUSIONS: Photodynamic biologic tissue glue was comparable to sutures in providing adequate corneal wound strength in PKP in a cadaver eye model. Wound closure with PBTG may reduce the number of sutures required in corneal transplantation and decrease the incidence of suture-related complications and allograft rejection.

Cadaver↗

PubMed1997

Photodynamic biologic tissue glue to enhance corneal wound healing after radial keratotomy.

PURPOSE: To evaluate the effect of photodynamic biologic tissue glue (PBTG) on corneal wound healing after radial keratotomy (RK). SETTING: Cornea Research Laboratory, The University of Chicago, Chicago, Illinois, USA. METHODS: Bidirectional, eight-incision RK was done in one eye of eight Dutch pigmented rabbits. Then, PBTG was inserted into the RK incisions and activated with an argon blue-green laser in four treatment eyes. The rabbits were divided into three groups: early, in which corneal wound healing was assessed at 1 and 3 weeks; late, in which corneal wound healing was assessed at 8 weeks; enhancement. RESULTS: The PBTG-treated keratotomy wounds had a more prominent epithelial healing response immediately after RK and a decreased propensity for wound dehiscence. Collagen fiber arrangement in the PBTG-treated incisions was sagittal to the keratotomy wound 1 to 3 weeks after RK and then changed to a transverse orientation across the keratotomy wound by 8 weeks. The control keratotomy wounds had a less prominent epithelial healing response and developed late disorganization of the posterior keratotomy wound at 8 weeks. Keratometry measurements 2 months after RK showed corneal flattening of 1.0 diopter (D) in the PBTG-treated eye and 6.5 D in the control eye, which is consistent with histologic studies showing more advanced wound healing in the PBTG-treated eyes. After RK enhancement, the PBTG-treated eye resisted further corneal flattening and had 4.5 D of corneal steepening; the control eye had 2.0 D of additional corneal flattening. CONCLUSION: The nontoxic, laser-activated adhesive PBTG accelerated corneal wound healing after RK and simulated the placement of sutures into the RK wound. Thus, PBTG may be an alternative to sutures to correct hyperopia after RK in humans.

Animals↗

PubMed1996

Practice revenue and cost distribution for ophthalmology, 1988 to 1993.

As opthalmologists need to better manage their practices, information regarding distribution of practice costs becomes more relevant. In this study, we compare revenues and costs from published sources to determine changes over time and across surveys. We also evaluate the reliability and validity of these statistics. Data were obtained from the Health Care Financing Administration (for 1988), the American Medical Association (for 1988, 1990, 1992, and 1993), and the Medical Group Management Association (for 1988, 1990, 1992, and 1993) and were compared across years and surveys. We found large differences among the surveys in both dollar amounts and percentages of total revenue for some of the reported cost categories. Analysis of the data over time showed less of a decline in physician earnings than expected, although there were large increases in the category "other costs." We found considerable divergence among the statistical results. Opthalmologists, public policymakers, and managed care organizations must exercise great caution in interpreting such data and in applying their findings to individual ophthalmic practices and practitioners.

American Medical Association↗

PubMed1994

Photodynamic biologic tissue glue.

We studied both heat- and light-activated tissue glues, and while a heat-activated mixture such as albumin and fluorescein isothiocyanate was effective, we believed that a light-activated substance would have less of an effect on adjacent tissue. Our glue uses a photosensitive singlet oxygen generator to cross-link a protein solder with corneal stromal collagen. The mixture consists of 18% fibrinogen and 2.6 mg/ml of riboflavin-5-phosphate activated with a blue-green (488-514 nm) Argon laser. We tested our glue by soldering 5-mm penetrating central corneal incisions made in human cadaver eyes. The strength of the closure was measured by cannulating the vitreous cavity with an 18-gauge needle connected to a saline reservoir. The pressure in the reservoir was elevated by connecting it to a sphygmomanometer. Immediately following tissue closure, the intraocular pressure was increased until the wound burst. We soldered and measured 10 eyes and found a mean bursting pressure of 154 mm Hg, with a range of 80-260 mm Hg. Our laser-activated tissue glue is an effective adhesive for corneal tissue, and we now plan to carry out toxicity studies in living animals.

Cornea↗