M. Orozco

Efficacy of various drugs in the prevention of posterior capsule opacification: Experimental study of rabbit eyes

Purpose: To assess the efficacy of various drugs in the prevention of posterior capsule opacification (PCO) in a closed capsular bag technique. Setting: Ophthalmic Biophysics Center, Bascom Palmer Eye Institute, University of Miami School of Medicine, Miami, Florida, USA. Methods: Lens material was removed using phacoaspiration or phacoemulsification through a microcapsulorhexis according to the hardness of the crystalline lens correlated with the weight and age of the rabbits. A mixture of an ophthalmic viscosurgical device (sodium hyaluronate 1.4% [SHA]) and a drug was injected into the empty capsular bag, allowed to remain inside for 3 minutes, and removed. The capsular bag was rinsed with balanced salt solution (BSS®) and refilled with SHA. In a group of rabbits, the capsulorhexis was sealed with a minicapsulorhexis valve (MCV). Rabbits were treated with 1 of the following: SHA (control), BSS, mitomycin‐C (MMC, 0.2 mg/mL), ethylenediaminetetraacetic acid (EDTA) (10 mM and 15 mM), 5‐fluorouracil (5‐FU, 33 mg/mL), acetic acid (3%, 0.3%, and 0.003%), and distilled water. Results: Upon completion of the study, the control and treated eyes had PCO and new lens material (not residual). Anterior capsule proliferation was observed in eyes treated with 5‐FU. The order of PCO appearance (earliest to latest) was as follows: 15 mM EDTA, SHA, MMC, acetic acid 0.3%, acetic acid 3%, BSS, distilled water (small animals; no MCV), acetic acid 0.003%, 5‐FU, 10 mM EDTA, and distilled water (large animals; MCV). The earliest appearance was day 1 postoperatively and the latest, day 47. Conclusions: Distilled water and 10 mM EDTA treatments were the most efficient in retarding the appearance of PCO.

Evaluation of an Integrated Orbital Tissue Expander in Congenital Anophthalmos: Report of Preliminary Clinical Experience

PURPOSE To evaluate the effectiveness of an orbital tissue expander designed to stimulate orbital bone growth in an anophthalmic socket. DESIGN Retrospective, noncomparative, interventional case series. METHODS SETTINGS Institutional. STUDY POPULATION Nine consecutive patients with unilateral congenital anophthalmos. INTERVENTION The orbital tissue expander is made of an inflatable silicone globe sliding on a titanium T-plate secured to the lateral orbital rim with screws. The globe is inflated by a transconjunctival injection of normal saline through a 30-gauge needle to a final volume of approximately 5 cm(3). Computed tomography scans were used to determine the orbital volume. The data studied were: demographics, prior orbital expansion procedures, secondary interventions, orbital symmetry, and implant-related complications. MAIN OUTCOME MEASURES The primary outcome measure was the orbital volume change, and the secondary outcome measures were changes in forehead, brow, and zygomatic eminence contour and adverse events. RESULTS The average patient age at implantation was 41.89 ± 39.42 months (range, 9 to 108 months). The initial average volume of inflation was 3.00 ± 0.87 cm(3) (range, 2.0 to 4.0 cm(3)), and the average final volume of 4.33 ± 0.50 cm(3) (range, 4.0 to 5.0 cm(3)) was achieved. The duration of expansion was 18.89 ± 8.80 months (range, 4 to 26 months). All patients demonstrated an average increase in the orbital tissue expander implanted orbital volume of 5.112 ± 2.173 cm(3) (range, 2.81 to 10.38 cm(3)). The average difference between the volume of the implanted and the initial contralateral orbit was 5.68 ± 2.34 cm(3), which decreased to 2.53 ± 1.80 cm(3) at the final measurement (P < .001, paired t test). All implants remained inflated except for 2 iatrogenic punctures at the second inflation and 1 that was the result of implant failure. All were replaced. CONCLUSIONS The integrated orbital tissue expander is safe and effective in stimulating anophthalmic socket bone growth.

Validation of the barraquer tonometer for high intraocular pressure estimation

PURPOSE To compare the pneumatonometer and the Tono-Pen XL in a closed ex-vivo system in human eye bank eyes at high intraocular pressures (IOP) and evaluate the validity of high IOP measurements with the Barraquer tonometer. METHODS Intraocular pressure was monitored by cannulation of the anterior chamber and vitreous cavity in eight human cadaver eyes (mean donor age: 77.3 +/- 4.9 years, range: 72 to 84 years). Intraocular pressure measurements were taken at 50, 65, and 90 mmHg with the Tono-Pen XL and pneumatonometer. Intraocular pressure was raised to 110 mmHg and then the eyes were deflated slowly until they reached 50 mmHg. Pressure readings with the Barraquer tonometer were recorded when the corneal tonometer interface reached the inner and outer rings. RESULTS The Tono-Pen XL underestimated IOP, a tendency that was more evident at higher IOP In contrast, the pneumatonometer was more accurate and reliable at IOP of 50 and 65 mmHg but its readings underestimated IOP at 90 mmHg. The Barraquer tonometer used in this experiment accurately estimated high IOP A variability of 5.9 mmHg and 5.8 mmHg were recorded for the inner and outer ring, respectively. CONCLUSIONS The Tono-pen XL is an inadequate instrument to assess pressures normally encountered during LASIK flap creation in an ex vivo model using human cadaver eyes. The pneumatonometer and the Barraquer tonometer are accurate instruments at high IOP; however, the pneumatonometer underestimated pressures around 90 mmHg.

Treatment of retinal detachment with an encircling band and buckle implant: A comparative pilot study between poly (styrene- b -isobutylene- b -styrene) (SIBS) and trimethyl terminated polydimethylsiloxane (PDMS)

Purpose: To demonstrate the biocompatibility of SIBS implants as compared to PDMS implants in the treatment of retinal detachment in New Zealand White (NZW) rabbit model.1,2 Introduction: Scleral encircling bands, fixation rings and buckles are utilized for closure of retinal breaks and retina reattachment. The FDA approved PDMS-implant is associated with several post-operative complications, involving thick-fibrotic encapsulations. SIBS, an elastomeric triblock copolymer, was recently FDA approved for use in a cardiovascular drug eluting stent (TAXUSTM, Boston Scientific Corp., MA) and showed excellent biocompatibility and slow drug release capability. Materials and Methods: SIBS (9-mol%-styrene) implants were fabricated (InnFocus LLC, USA) to match PDMS implants (Labtician, Inc, Canada) dimensions. 5 NZW rabbits received SIBS and 4, PDMS-implants. Post-operative exam sequence: day 1 and 2, week 1, 2, 3, 4 and 6, and monthly thereafter for up to 1 year. Anatomohistopathology exams sequence: one SIBS animal at 6 weeks and one animal of each treatment group at 3 and 6-months, and two at 12-months. Results: SIBS compared to PDMS animals exhibited less inflammation and a better buckling effect during the first 6 weeks. At POD 9 months, the conjunctival injection in the SIBS rabbit was none as opposed to the PDMS value and the buckling effect for both groups were equal. There were no visible signs of encapsulation with SIBS. There were no infections in the 9 animals and none of the implants extruded thus far (<10 months). Conclusion: SIBS encircling bands, sleeves, and buckle implants are well tolerated in the rabbit model.

Endocapsular hyperthermia probe to prevent posterior capsular opacification

Purpose: To evaluate the feasibility to induce lens epithelial cell death with intraoperative hyperthermia for prevention of secondary cataract. Methods: A prototype miniature resistive hyperthermia probe was designed. The probe contained a thermocouple for temperature feed-back. A timer allowed monitoring of the electrical driving of the hyperthermia probe and the temperature induced as a function of time. To model the heating response, a simple model of the lens capsule was constructed using a thin acrylic plastic shell embedded in a sponge immersed in a water bath at 37°C. The shell was filled with sodium hyaluronate. The probe was positioned at the center of the shell with the thermocouple next to the wall. An experimental protocol was developed to assess the feasibility of increasing the temperature of the human lens to hyperthermia levels in fresh cadaver eyes: An annular metal ring was bonded just below the limbus, the cornea and iris were sectioned, the lens material was removed through a central 5mm diameter capsulorhexis, the capsule was filled with SHA and the globe was set on a temperature-controlled cylindrical vial. Preliminary Results: At 3.3W (2.2V, 1.5A) the shells content increases from 37°C to 51°C in 30s. At that temperature, LEC death is expected to occur within 1sec. Conclusion: This preliminary study demonstrates the feasibility of increasing the temperature of the capsular bag to kill LECs by hyperthermia.