Protection of corneal allografts by CTLA4-Ig.

PURPOSE: CTLA4, a high-affinity ligand of B7, can, in soluble form, prevent antigen-driven T-cell activation by blocking CD28-B7 interaction and can thereby prevent immune graft rejection. In this study, we tested the capacity of soluble CTLA4-Ig alone or in combination with UV-B irradiation to suppress corneal allograft rejection in rabbits. METHODS: Corneas from Dutch belted rabbits were incubated in corneal storage medium containing 0, 1, 10, 25, or 250 microg/ml of CTLA4-Ig for 18 h and were then transplanted into the vascularized or nonvascularized corneas of New Zealand White rabbit recipients. A series of donor corneas were exposed to UV-B irradiation alone or a combination of irradiation and CTLA4-Ig to determine if these two treatments would have an additive effect in prolonging graft survival. The fate and clinical condition of the allografts were evaluated by slit-lamp photomicroscopic observation and corneal-thickness measurements. Grafts that were rejected were processed for histopathologic and immunohistochemical analysis to determine the characteristics of cells infiltrating the grafts. RESULTS: Grafts placed in nonvascularized corneas showed no differences in survival times, regardless of treatment. Among the grafts placed in vascularized corneas, those incubated with CTLA4-Ig at a concentration of 250 microg/ml failed within 7-14 days. Histopathologic and immunocytochemical examination revealed a dense accumulation of immune inflammatory cells, especially class II major histocompatibility complex (MHC)-expressing, antigen-presenting cells, in the failed grafts. Grafts incubated with CTLA4-Ig at concentrations of 1 and 10 microg/ml had mean survival times greater than the control, untreated corneal allografts. Some of the grafts in these two treatment groups survived for the 100-day observation period, whereas none of the grafts in the other treatment groups survived to this end point. UV-B irradiated grafts incubated with CTLA4-Ig at a concentration of 1 microg/ml appeared to have longer survival times and fewer rejections compared with control, untreated grafts and grafts treated with UV-B or CTLA4-Ig alone. CONCLUSION: The results show that the CTLA4-Ig coreceptor blocking agent can prolong corneal allograft survival in vascularized graft sites and that UV-B irradiation followed by incubation in CTLA4-Ig may prolong graft survival better than either treatment alone. These results suggest that agents that prevent second-signal interaction between antigen-presenting cells and T lymphocytes may be useful for inhibiting corneal allograft rejection.

Near vision contrast sensitivity after photorefractive keratectomy.

BACKGROUND: To evaluate near vision contrast sensitivity as a measure of visual performance after photorefractive keratectomy (PRK). SETTING: LSU Eye Center, New Orleans, Louisiana. METHODS: Using Holladay Contrast Acuity Test cards, near (reading) vision for five levels of contrast sensitivity was evaluated in a cross section of 53 eyes of 31 patients 25 to 732 days after PRK. Twenty-four normal eyes of 22 myopic patients served as controls. RESULTS: Near contrast sensitivity decreased at all tested contrast levels for approximately 7 months after PRK and then returned to baseline. This phenomenon paralleled the fluctuation in best corrected distance Snellen acuity. CONCLUSIONS: These preliminary results indicate that Snellen visual acuity and near contrast sensitivity returned to baseline within 1 year after PRK.

Early clinical experience with the Baerveldt implant in complicated glaucomas.

PURPOSE: To evaluate our early experience with the Baerveldt implant in patients with complicated glaucoma. METHODS: We reviewed the charts of all patients with more than six months of follow-up after placement of a Baerveldt implant at LSU Eye Center. Surgery was considered a success if intraocular pressure was 21 mm Hg or less (with or without antiglaucoma medications) at the last postoperative visit, except when further glaucoma surgery had been performed or when loss of light perception occurred. RESULTS: Fifty eyes (50 patients) were divided into six diagnostic groups, with mean follow-up times of 16.1 to 19.2 months. Success was achieved in 36 of 50 patients (72%): 26 of 35 (74%) patients with aphakia or pseudophakia, nine of 12 (75%) patients with previously failed filtering surgery, three of seven patients with neovascular glaucoma, all three patients under the age of 13 years, nine of 13 (69%) patients who underwent penetrating keratoplasty, and four of five phakic patients. Overall, visual acuity improved or remained within one line of the preoperative acuity in 32 (64%) patients. The most frequently observed short- and long-term complications were serous choroidal effusion associated with hypotony in 13 (26%) patients and corneal graft failure in six of 13 (46%) corneal transplant patients, respectively. CONCLUSION: Within the study follow-up time, the Baerveldt implant appeared to be safe and effective, with success rates for intraocular pressure control similar to those reported in a recent retrospective study of the Molteno implant.

In vitro alteration of Schirmer's tear strip wetting by commonly instilled anesthetic agents.

The Schirmer's tear test is often performed with topical anesthesia to reduce reflex tearing. Fluress (Barnes-Hind, Sunnyvale, CA, U.S.A.) and Fluoracaine (Akorn, Abita Springs, LA, U.S.A.) are commonly used anesthetic-fluorescein preparations that contain viscous additives. Because the rate of Schirmer's strip wetting is dependent on capillary action, a property related to solution viscosity and surface tension, spurious results may be obtained if these agents are used for anesthesia. We report in vitro Schirmer's strip wetting rates for various concentrations of Fluress and Fluoracaine, as well as pure fluorescein solution using a tear substitute (Dacriose; IOLAB, Claremont, CA, U.S.A.) as a diluent. Results showed a direct concentration-dependent reduction of Schirmer's strip wetting with time for both Fluress and Fluoracaine dilutions compared with Dacriose alone (p < 0.001) or Dacriose-fluorescein solutions (p < 0.001). In addition, Schirmer's wetting with Dacriose-fluorescein solutions caused a separation of the Dacriose and fluorescein wetting fronts (p < 0.001) but did not affect the overall Dacriose wetting. These data have clinical implications concerning false-positive results when testing for dry eyes.

Pneumotonometry using sterile single-use tonometer covers.

Current methods for cleaning pneumotonometer tips include soaking the removable tip in various chemical agents. Disadvantages of this technique include the potential for incomplete disinfection, corneal contact with cleaning solutions, tip damage or loss, and soaking time. The authors studied the use of an available, disposable latex cover placed over the pneumotonometer tip for measuring intraocular pressure (IOP) in 46 eyes with normal corneas from a glaucoma screening clinic and 141 eyes with normal and abnormal corneas from a cornea and external disease clinic. The mean absolute IOP difference comparing with and without the tonometer cover was 1.6 mmHg for the glaucoma screening patients and 1.8 mmHg for the cornea clinic patients. A tonographic-like effect due to repeated tonometry also was shown. An additional study measuring a series of known IOP values in a cadaver eye showed no significant difference between uncovered and covered readings. These data suggest that placement of a disposable, latex cover over the pneumotonometer tip enables accurate IOP measurements and is a sanitary and convenient alternative method to repeated chemical disinfection.