Combining the Tunnel Orbicularis Oculi Muscle Flap Technique With Skin Grafting for Enhanced Adhesion in Burn-Induced Ectropion Repair

PURPOSE

Scar contracture of the eyelid following facial burns often has adverse consequences. Total cicatricial contracture often makes adjustment flap translation challenging to implement. Previously used upper and lower eyelid adhesion methods are ineffective for patients with severe cicatricial contracture, and ectropion can easily recur. This study aimed to retrospectively examine upper and lower eyelid adhesions using an orbicularis oculi muscle flap and verify its stability.

METHODS

In patients with ectropion caused by severe scar contracture following head and face burns, we employed a tunnel orbicularis oculi muscle flap technique, which involved creating a tunnel between the skin and the tarsal plate of the eyelid, mobilizing the orbicularis oculi muscle, and rotating it into this tunnel to provide stable adhesion of the upper and lower eyelids. Full-thickness skin grafting was then performed. The eyelids were examined postoperatively to determine whether reoperation was necessary and to monitor for any potential complications.

RESULTS

This study included 26 patients and 46 eyes. No accidental disconnection occurred after eyelid adhesion, which lasted for an average of 21.87 ± 10.08 months before the eyelid adhesion was cut open. No complications or adverse reactions occurred, and the adhesions did not break unexpectedly.

CONCLUSIONS

Repairing eyelid ectropion with the tunnel orbicularis oculi muscle flap is a simple procedure that immediately creates tension against upper and lower eyelid contractures, providing long-term stable adhesion. This method avoids structural disorders, such as eyelid margin scarring, minimally influences surrounding tissues, and has few postoperative complications. It holds great value for repairing eyelid tissue defects and warrants further study.

Augenverätzungen

Chemical burns of the ocular surface (CBOS) are emergencies of highest urgency. Therefore, an adequate emergency care is mandatory. Following a precise analysis of the initial damage, a staged therapeutic approach is used to prevent persistent impairment of the ocular surface. In the acute stage, the prevention of complications is targeted (symblepharon, conjunctival scarring, lacrimal stenosis, corneal ulceration, intraocular inflammation, elevated intraocular pressure, etc.). In later stages, if complications have developed, a secondary restoration of the ocular surface is focussed. Sometimes this requires several surgical interventions. Based on a review of international literature, this review highlights the pathophysiology according to different chemical agents, CBOS stages as well as main therapy strategies in early and advanced stages of CBOS. Acute treatment aims to lower inflammation, oxidative stress and tries to promote reepithelialisation. Besides conjunctival scarring, loss of goblet cells and corneal opacification a limbal stem cell insufficiency is the most harming complication. Several new techniques have been developed to recover the ocular surface with a sufficient and clear epithelial layer in order to avoid neovascularization of the cornea. The knowledge concerning the high risk potential for persistent visual impairment in CBOS patients and the ability for appropriate emergency care should be kept in every physician's mind dealing with CBOS.

Amniotic Membrane Transplantation in Acute Severe Ocular Chemical Injury: A Randomized Clinical Trial

PURPOSE

To compare the outcomes of conventional medical treatment vs combined medical treatment and amniotic membrane transplantation (AMT) in the management of patients with Roper-Hall grade IV ocular chemical injury.

DESIGN

Randomized, parallel-controlled clinical trial.

METHODS

Setting: Single tertiary referral hospital.

PATIENTS

Sixty eyes of 60 patients with Roper-Hall grade IV ocular chemical injury with a minimum follow-up of 12 months were enrolled in the study.

INTERVENTION

Patients were randomly assigned to 2 groups: Group 1 (30 eyes) received topical preservative-free lubricating gel and drops, chloramphenicol, betamethasone, homatropine, oral vitamin C, and doxycycline; Group 2 (30 eyes) received amniotic membrane transplant (AMT) on the entire ocular surface in addition to the medical treatment provided in Group 1.

OUTCOME MEASURES

The main outcome measure was time to complete corneal epithelialization. Secondary outcome measures were best-corrected visual acuity (BCVA) and neovascularization in the central 5 mm of the cornea.

RESULTS

Mean follow-up time was 20.3 ± 2.5 months (range 13-24 months). Corneal epithelial defects healed within 72.6 ± 30.4 (21-180) days in Group 1 vs 75.8 ± 29.8 (46-170) days in Group 2 (P = .610). Mean BCVA was 2.06 ± 0.67 (0.4-2.6) logMAR vs 2.06 ± 0.57 (1-2.9) logMAR in Groups 1 and 2, respectively (P = .85). Group 1 developed more central corneal neovascularization (22 eyes; 73.3%) compared to Group 2 (16 eyes; 53.3%); however, it was not statistically significant (P = .108).

CONCLUSIONS

In comparison to conventional medical therapy, combined amniotic membrane transplantation and medical therapy does not accelerate corneal epithelialization or affect final visual acuity in severe chemical injuries.

Pattern of ocular injuries in Bangladesh and its surgical management at hospital setting: A retrospective study

OBJECTIVE

To determine the pattern of ocular injuries and their surgical management..

Methods

The retrospective study was conducted at the Chittagong Eye Infirmary and Training Complex, Chittagong, Bangladesh, and comprised hospital data of patients with ocular injuries from October 1, 2016, to December 31, 2017. Information gathered related to type and cause of injuries, visual acuity, postoperative complications, follow-up visits, and outcome. SPSS version 22 was used for data analysis.

Results

Of the total injuries, 370 (91%) were classified open globe and 36 (9%) as close globe. In terms of type of injury, 330 (81.4%) were penetrating, 30 (7.3%) ruptured globe, 29 (7.1%) lime burn and 17 (4.2%) injuries were traumatic hyphaema and chemical in nature. Open globe injuries were mostly found in subjects aged 18 years or below. Surgery was the main mode of management in 388 (95.5%) patients.

Conclusion

Preventive measures along with high-quality management should receive priority for reducing monocular blindness.

[Atypical clinical case of solar retinopathy]

The paper presents an atypical case of solar retinopathy after short-term exposure to reflected focused sunbeams. An ophthalmoscopic peculiarity was the presence of intraretinal hemorrhage. The basis for establishing the diagnosis were spectral optical coherence tomography and fluorescein angiography findings.

A CASE OF ACCIDENTAL OCULAR INJURY FROM COSMETIC LASER BURN

PURPOSE

To report the clinical course of a patient sustaining a ocular laser injury from 1,064-nm Nd:YAG cosmetic laser machine.

METHOD AND PATIENT

A 31-year-old beauty parlor aesthetician was operating an Nd:YAG cosmetic laser machine of 1,064 nm wavelength. However, the probe was held in the opposite direction, and on firing, the laser shot fired into her left eye. The patient heard a "pop" sound followed by immediate floaters and blurring of vision. Her clinical course was followed for 6 weeks, with investigations including optical coherence tomography, fluorescein angiogram, and Humphrey's visual field examination performed.

RESULTS

Optical coherence tomography taken over the injured area showed thickened retina and preretinal hyperreflectivities. Fluorescein angiogram showed hypofluorescence superonasal to the disk with late staining of vessels. Humphrey's visual field showed a dense scotoma emanating from the blind spot. The lesion eventually scarred down, and the patient's vision recovered.

DISCUSSION

The eye is the most susceptible body part to laser light injury. A review of reported laser accidents revealed the majority to be ocular injuries. The retina is particularly vulnerable, as laser light with wavelength between 400 nm and 1,400 nm is focused by the cornea and lens onto the retina, increasing the retinal irradiance as a result. Most injuries were parafoveal, suggesting that most injuries occurred during laser beam alignment. The prognosis is generally favorable. As laser use becomes more widespread and its application increasingly heterogeneous, regulation of laser use and monitoring of laser safety are crucial but at the same time challenging.

Bioengineered Corneas Grafted as Alternatives to Human Donor Corneas in Three High-Risk Patients

Corneas with severe pathologies have a high risk of rejection when conventionally grafted with human donor tissues. In this early observational study, we grafted bioengineered corneal implants made from recombinant human collagen and synthetic phosphorylcholine polymer into three patients for whom donor cornea transplantation carried a high risk of transplant failure. These patients suffered from corneal ulcers and recurrent erosions preoperatively. The implants provided relief from pain and discomfort, restored corneal integrity by promoting endogenous regeneration of corneal tissues, and improved vision in two of three patients. Such implants could in the future be alternatives to donor corneas for high-risk patients, and therefore, merits further testing in a clinical trial.

[Features of stress reactivity of the organism and clinical patterns of ocular burn]

Clinical patterns of ocular burn in patients with different types and variants of stress reactivity were studied. It is shown that patients with the maladaptive type of stress reactivity at any stage of the disease are at higher risk of complications. Rapid exhaustion of the sympathoadrenal system or a hyperactive stress response seen in cases of the labile and hyperergic individual adrenergic immune reactivity of the organism (IAIRO) can be considered as manifestations of a regulation disorder. The absence of complications along with mild changes in immune reactivity is characteristic of the normoergic variant of IAIRO.

Bilateral chemical eye injury resulting from airbag deployment

A case report highlighting an unusual cause of a chemical injury and an explanation of the basic initial management of chemical eye injuries: relevant to all Armed Forces medical personnel.

[Fibrinolysis components and angiogenesis regulation by example of burn-induced corneal neovascularization in rabbits]

Increased plasminogen level in tear fluid was found within 28 days and increased plasmin activity in 1-3 and 21 days after alkali burn of cornea, this is the time of cornel ulcers development. Increased plasminogen level and plasmin activity in cornea, conjunctiva and intraocular fluid was found in three days after trauma. Subconjunctival injections of angiostatin K1-4,5 (a product of plasminogen metabolism) during 3 weeks resulted in significant suppression of corneal neovascularization within 14 days and of active branching of the vessels in the following. The use of angiostatin reduced depth and area of corneal ulcers. Obtained data shows the promising potential of development of medications based on angiostatin K1-4,5 for suppression of corneal neovascularization and for treatment of diseases associated with corneal ulceration.

Use of the Boston Ocular Surface Prosthesis in the management of severe periorbital thermal injuries: a case series of 10 patients

PURPOSE

To report the use of the Boston Ocular Surface Prosthesis (BOSP) in patients with severe periorbital thermal injuries.

DESIGN

Retrospective, interventional case series.

PARTICIPANTS

Patients with severe periorbital thermal injuries treated with the BOSP.

METHODS

Chart review of 10 consecutive patients (16 eyes) who sustained severe periorbital thermal injuries during combat missions in Iraq and Afghanistan and were treated for exposure keratopathy with the BOSP, a Food and Drug Administration-approved gas-permeable, scleral contact lens.

MAIN OUTCOME MEASURES

Corneal epithelial defect healing, uncorrected and best-corrected visual acuity, and BOSP wear time.

RESULTS

Exposure keratopathy occurred after severe periorbital thermal injuries and followed a predictable course of scar contracture. In all patients, vision-threatening ocular surface disease developed as a result of chronic ocular exposure. Rehabilitation of the ocular surface was accomplished using the BOSP, with 10 of the 16 treated eyes achieving a corrected visual acuity of 20/70 or better. Five eyes achieved a best-corrected visual acuity of 20/40 or better. The BOSP also was used as a drug-delivery vehicle to treat corneal ulcers successfully in 6 eyes. The only eye that required penetrating keratoplasty was an early intervention believed to be a direct sequelae of the original thermal burn, rather than a failure of the BOSP regimen. The mean BOSP wear time was 16 hours per day.

CONCLUSIONS

The BOSP can play an important role in rehabilitation of the ocular surface for patients with severe periorbital thermal injuries and resultant exposure keratopathy. Use of the BOSP should be considered as a treatment option for these difficult cases of severe periorbital thermal injuries.

Deep anterior lamellar keratoplasty using acellular corneal tissue for prevention of allograft rejection in high-risk corneas

PURPOSE

To determine whether deep anterior lamellar keratoplasty (DALK) using acellular glycerol-cryopreserved corneal tissue (GCCT) could prevent allograft rejection in high-risk corneas.

DESIGN

Prospective, randomized, comparative study.

METHODS

SETTINGS

The Eye Hospital, Wenzhou Medical College, Zhejiang, China.

STUDY POPULATION

All patients with herpes simplex virus keratitis, bacterial keratitis, fungal keratitis, or ocular burn, who were eligible as per study design, were invited to participate.

OBSERVATION PROCEDURES

According to randomized block design, all patients received either GCCT or fresh corneal tissue (FCT) during DALK. Best-corrected visual acuity (BCVA), slit-lamp microscopy, and in vivo confocal microscopy examinations at 1 week and 1, 3, 6, 12, and 24 months after surgery were analyzed. Kaplan-Meier survival analysis was used to evaluate graft survival rate.

MAIN OUTCOME MEASURES

Therapeutic success, 2-year rejection-free graft survival rate and 2-year graft survival rate, in vivo confocal microscopy results, BCVA, and endothelial cell density.

RESULTS

Postoperative BCVA of 20/40 or better at the last follow-up visit was achieved in 57.6% (19/33) of eyes in the GCCT group and in 54.8% (17/31) of the FCT group. No graft rejection occurred in the GCCT group, while in the FCT group 10 episodes of stromal rejection developed in 7 eyes. Overall, the rejection-free graft survival rate at 2 years was significantly higher in the GCCT group as compared with the FCT group (100.0%, 78.8% respectively, P = .006).

CONCLUSIONS

Deep anterior lamellar keratoplasty using acellular glycerol-preserved cornea could prevent allograft rejection and promote graft survival rate in high-risk corneas.

VEGF-induced corneal neovascularisation in a rabbit experimental model

INTRODUCTION AND PURPOSE

Various conditions may cause vascularization of the normally avascular cornea. The aim of the present study was to create a reproducible experimental model that could enable the investigation of the phenomena leading to corneal vascularization. This involved creating a software to record the experimental data, enabling a subsequent digital analysis based on the growth models. The VEGF-induced pattern of neovascularization was also investigated.

MATERIAL AND METHODS

Twenty-seven rabbits divided in groups were used for the purposes of the present study. Some of them underwent intracorneal implants with or without vascular endothelial growth factor (VEGF) pellets, using an original microsurgical technique. Central and peripheral corneal burns were induced to other groups of animals in order to mimic the neovascularization process induced by inflammation. Finally, Dexamethasone (Maxidex) was given intraocularly, on days 1 and 3 after the onset of neovascularisation, in rabbit groups with both corneal burns and VEGF-implants. Video recording and data analysis of the corneal vascularization were made with an advanced biomicroscope, a computerized imaging system and a special software. A histochemical study of the animals' eyes was also carried out.

RESULTS AND DISCUSSION

The recorded data showed the simplicity and reproducibility of the present experimental model. The results showed the importance of VEGF as an initiator and promoter of corneal vascularization through a non-inflammatory mechanism, quite different from the inflammation illustrated by the corneal burn. At the same time, Dexamethasone therapy proved its effectiveness in corneal angiogenesis induced by thermal burn, but not by VEGF-implant.

Thermal lensing in ocular media exposed to continuous-wave near-infrared radiation: the 1150-1350-nm region

Ocular damage threshold data remain sparse in the continuous wave (CW), near-infrared (NIR) radiation region save for the 1300-nm area that has been investigated in the past several decades. The 1300-nm ocular damage data have yielded unusual characteristics where CW retinal damage was observed in rabbit models, but never in nonhuman primate models. This paper reviews the existing 1300-nm ocular damage threshold data in terms of the fundamental criteria of an action spectrum to assist in explaining laser-tissue effects from near-infrared radiation in the eye. Reviewing the action spectrum criteria and existing NIR retinal lesion data lend evidence toward the significant presence of thermal lensing in ocular media affecting damage, a relatively unexplored mechanism of laser-tissue interaction.

Ex vivo and computer model study on retinal thermal laser-induced damage in the visible wavelength range

Excised bovine eyes are used as models for threshold determination of 532-nm laser-induced thermal damage of the retina in the pulse duration regime of 100 micros to 2 s for varying laser spot size diameters. The thresholds as determined by fluorescence viability staining compare well with the prediction of an extended Thompson-Gerstman computer model. Both models compare well with published Rhesus monkey threshold data. A previously unknown variation of the spot size dependence is seen for different pulse durations, which allows for a more complete understanding of the retinal thermal damage. Current International Commission on Nonionized Radiation Protection (ICNIRP), American National Standards Institute (ANS), and International Electromechanical Commission (IEC) laser and incoherent optical radiation exposure limits can be increased for extended sources for pulsed exposures. We conclude that the damage mechanism at threshold detected at 24 and 1 h for the nonhuman primate model is retinal pigment epithelium (RPE) cell damage and not thermal coagulation of the sensory retina. This work validates the bovine ex vivo and computer models for prediction of thresholds of thermally induced damage in the time domain of 10 micros to 2 s, which provides the basis for safety analysis of more complicated retinal exposure scenarios such as repetitive pulses, nonconstant retinal irradiance profiles, and scanned exposure.

Ocular effects of exposure to industrial chemicals: clinical management and proteomic approaches to damage assessment

Industrial chemicals in a variety of applications are often found in highly populated areas and their presence carries risks. The threat of serious consequences from inadvertent or intentional events involving hazardous chemicals is a possibility. Extremism and/or other illicit activities pose environmental threats from chemical exposures. We present here a review of the threat of ocular injury in small-and large-scale chemical releases and discuss mechanisms of damage and repair to the eyes. The emerging field of proteomics has been described in relation to its potential role in the assessment of ocular changes following chemical exposures and management of ocular trauma.

Effect of overexpression of PPARgamma on the healing process of corneal alkali burn in mice

Wound healing involves both local cells and inflammatory cells. Alkali burn of ocular surface tissue is a serious clinical problem often leading to permanent visual impairment resulting from ulceration, scarring and neovascularization during healing. Behaviors of corneal cells and inflammatory cells are orchestrated by growth factor signaling networks that have not been fully uncovered. Here we showed that adenoviral gene introduction of peroxisome proliferator-activated receptor-gamma (PPARgamma) inhibits activation of ocular fibroblasts and macrophages in vitro and also induced anti-inflammatory and anti-fibrogenic responses in an alkali-burned mouse cornea. PPARgamma overexpression suppressed upregulation of inflammation/scarring-related growth factors and matrix metalloproteinases (MMPs) in macrophages. It also suppressed expression of such growth factors and collagen Ialpha2 and myofibroblast generation upon exposure to TGFbeta1. Exogenous PPARgamma did not alter phosphorylation of Smad2, but inhibited its nuclear translocation. PPARgamma overexpression enhanced proliferation of corneal epithelial cells, but not of fibroblasts in vitro. Epithelial cell expression of MMP-2/-9 and TGFbeta1 and its migration were suppressed by PPARgamma overexpression. In vivo experiments showed that PPARgamma gene introduction suppressed monocytes/macrophages invasion and suppressed the generation of myofibroblasts, as well as upregulation of cytokines/growth factors and MMPs in a healing cornea. In vivo re-epitheliazation with basement membrane reconstruction in the healing, burned, cornea was accelerated by PPARgamma-Ad expression, although PPARgamma overexpression was considered to be unfavorable for cell migration. Together, these data suggest that overexpression of PPARgamma may represent an effective new strategy for treatment of ocular surface burns.

Pericytes are correlated with the permeability of rat corneal neovascular vessels induced by alkali burn

BACKGROUND

Corneal neovascular leakage can lead to edema and secondary scarring. Previous studies have shown that pericytes play a key role in maturation of angiogenesis. The present studies investigate the relationship between vascular permeability and pericyte coverage of endothelial cells in rat corneal neovascular induced by alkali burns.

METHODS

Corneal neovascular vessels induced by alkali burns was performed in Sprague-Dawley rats. Corneas were excised on 1, 2, 3, 5, 7 and 10 days after cauterization. The vascular permeability rate was measured by the Evans blue method. The microvessel pericyte coverage index (MPI) was applied to quantify the pericyte coverage through double immunofluorescent staining of frozen sections of corneas with CD31 as the endothelial and alpha-smooth muscle actin (alpha-SMA) as the pericyte markers. The correlation between permeability rate and MPI was analyzed. Pericyte coverage was confirmed ultrastructually using transmission electron microscopy.

RESULTS

The vascular permeability rate was (1.14 +/- 0.17), (0.24 +/- 0.08), (0.29 +/- 0.16), (0.14 +/- 0.10), (0.09 +/- 0.06) and (0.05 +/- 0.04) microg x ml(-1) x mm(-2) respectively on 1, 2, 3, 5, 7 and 10 days after cauterization. The MPI was 0, 16.07%, 11.95%, 43.84%, 73.97% and 86.21% respectively at the above mentioned time points. The correlation coefficient between MPI and the permeability rate was -0.943 (P = 0.005).

CONCLUSIONS

Pericyte recruitment was significantly correlated with the permeability of corneal neovascularization induced by alkali burns in rats. Therapeutic strategies aiming at anti-leakage should be most effective if they promote pericytes proliferation in the course of corneal neovascularization.

Thermal effect of microburst and hyperpulse settings during sleeveless bimanual phacoemulsification with advanced power modulations

PURPOSE

To assess wound temperature during bimanual sleeveless phacoemulsification using customizable power modulations such as hyperpulse and microburst technology.

SETTING

In vitro laboratory.

METHODS

The Millennium Microsurgical System (Bausch & Lomb) with custom control software (CCS) was used to perform phacoemulsification in 5 porcine eyes with MicroFlow needles (Bausch & Lomb) and with power varied from 20% to 80% in 10% increments. Pulse modes were set for fixed microburst (4 ms on, 4 ms off; and 6 ms on, 12 or 24 ms off) and for hyperpulse (30% duty cycle with 8 or 75 pulses per second [pps]), with and without aspiration-line occlusion. Wound temperatures were measured 3 times per second.

RESULTS

Using 80% total power, the wound temperature during 3 minutes of occlusion did not exceed 39.0 degrees C. The maximum temperature with fixed microbursts of 4 ms on, 4 ms off was 29.0 degrees C without occlusion and 37.8 degrees C with occlusion (duration 3 minutes). At 6 ms on, 12 ms off, the maximum temperatures were 28.1 degrees C and 38.7 degrees C, respectively. At 6 ms on, 24 ms off, peak temperatures were 24 degrees C and 23.6 degrees C, respectively. The hyperpulse mode of 30% duty cycle and 8 pps produced maximum temperatures of 25.5 degrees C nonoccluded and 33.4 degrees C occluded. With 30% duty cycle, 75 pps, temperatures were 28 degrees C and 38.0 degrees C, respectively. For all power below 80%, temperatures were lower.

CONCLUSIONS

Customizable power modulation with microburst and hyperpulse technology further reduced wound temperatures during bimanual sleeveless phacoemulsification. This enhances the safety and effectiveness of phacoemulsification through a sleeveless needle and a small stab incision.

Visual Outcome after Fireworks Injuries

BACKGROUND

The epidemiology and prognosis of fireworks-related injuries treated at a tertiary eye care center in less developed nations remain unknown.

METHODS

We conducted a prospective observational study that enrolled all consecutive eyes with fireworks-related ocular injury visiting our trauma clinic during a 1-year period. Eyes were graded by ocular trauma classification and followed for 6 months at least. Best corrected visual acuity (BCVA) at 6 months was considered the final visual outcome. Data were analyzed.

RESULTS

Twenty-five (96%) of a total of 26 patients enrolled during study period were male patients and 13 (50%) were younger than 15 years. The type of fireworks involved was a bottle rocket in 38.5%. Factors significantly associated with better final visual outcome were better BCVA at presentation (p = 0.041), absence of bottle rocket injury (p = 0.028), closed globe injury (p = 0.028), absence of relative afferent pupillary defect (p = 0.019), absence of intraocular foreign body (p = 0.026), and absence of endophthalmitis (p = 0.006). Besides poor visual outcome, bottle rocket injuries were more frequently associated with facial lacerations, intraocular foreign body, and endophthalmitis development.

CONCLUSION

Fireworks-related ocular injuries commonly affect young male subjects of northern India. Visual outcome is better in eyes having better initial BCVA or closed globe injury and if relative afferent pupillary defect, bottle rocket injury, intraocular foreign body, and endophthalmitis are absent.

Expression of Smad7 in mouse eyes accelerates healing of corneal tissue after exposure to alkali

Damage to the cornea from chemical burns is a serious clinical problem that often leads to permanent visual impairment. Because transforming growth factor (TGF)-beta has been implicated in the response to corneal injury, we evaluated the effects of altered TGF-beta signaling in a corneal alkali burn model using mice treated topically with an adenovirus (Ad) expressing inhibitory Smad7 and mice with a targeted deletion of the TGF-beta/activin signaling mediator Smad3. Expression of exogenous Smad7 in burned corneal tissue resulted in reduced activation of Smad signaling and nuclear factor-kappaB signaling via RelA/p65. Resurfacing of the burned cornea by conjunctival epithelium and its differentiation to cornea-like epithelium were both accelerated in Smad7-Ad-treated corneas with suppressed stromal ulceration, opacification, and neovascularization 20 days after injury. Introduction of the Smad7 gene suppressed invasion of monocytes/macrophages and expression of monocyte/macrophage chemotactic protein-1, TGF-beta1, TGF-beta2, vascular endothelial growth factor, matrix metalloproteinase-9, and tissue inhibitors of metalloproteinase-2 and abolished the generation of myofibroblasts. Although acceleration of healing of the burned cornea was also observed in mice lacking Smad3, the effects on epithelial and stromal healing were less pronounced than those in corneas treated with Smad7. Together these data suggest that overexpression of Smad7 may have effects beyond those of simply blocking Smad3/TGF-beta signaling and may represent an effective new strategy for treatment of ocular burns.

Therapeutic effect of topical administration of SN50, an inhibitor of nuclear factor-kappaB, in treatment of corneal alkali burns in mice

We evaluated the therapeutic efficacy of topical administration of SN50, an inhibitor of nuclear factor-kappaB, in a corneal alkali burn model in mice. An alkali burn was produced with 1 N NaOH in the cornea of C57BL/6 mice under general anesthesia. SN50 (10 microg/microl) or vehicle was topically administered daily for up to 12 days. The eyes were processed for histological or immunohistochemical examination after bromodeoxyuridine labeling or for semi-quantification of cytokine mRNA. Topical SN50 suppressed nuclear factor-kappaB activation in local cells and reduced the incidence of epithelial defects/ulceration in healing corneas. Myofibroblast generation, macrophage invasion, activity of matrix metalloproteinases, basement membrane destruction, and expression of cytokines were all decreased in treated corneas compared with controls. To elucidate the role of tumor necrosis factor (TNF)-alpha in epithelial cell proliferation, we performed organ culture of mouse eyes with TNF-alpha, SN50, or an inhibitor of c-Jun N-terminal kinase (JNK) and examined cell proliferation in healing corneal epithelium in TNF-alpha-/- mice treated with SN50. An acceleration of epithelial cell proliferation by SN50 treatment was found to depend on TNF-alpha/JNK signaling. In conclusion, topical application of SN50 is effective in treating corneal alkali burns in mice.

Amniotic membrane transplantation in acute chemical burns

PURPOSE

To evaluate the outcome of fresh amniotic membrane transplantation (AMT) for ocular surface reconstruction in acute chemical burns.

METHODS

A prospective study of 15 consecutive eyes with acute chemical burns was performed. In all, 10 eyes had lime burns and five eyes had acid burns. There were three eyes of grade II, four eyes of grade III and eight eyes of grade IV burns. AMT was performed within 3 weeks of injury.

RESULTS

Patients were followed up for 10.14 +/- 4.41 months. All patients had immediate relief of pain postoperatively. Of 15 eyes, nine (60%) showed epithelialization within 1-4 weeks (15.33 +/- 9.91 days). The final visual acuity improved in 10 of 15 eyes (66.66%). Eyes with burns of grade II and III showed more visual improvement than those with grade IV burns. None of the eyes showed perforation. Symblepharon was seen in nine of 15 eyes (60%). Of 15 eyes, 12 (80%) experienced limbal stem cell deficiency and showed superficial corneal vascularization.

CONCLUSIONS

Amniotic membrane transplantation with fresh amniotic membrane increases patient comfort and reduces inflammation. In mild burns, AMT alone restores corneal and conjunctival surfaces. In moderate to severe burns, it probably reduces conjunctival scarring sequelae, but does not prevent the sequelae of limbal stem cell deficiency that requires further limbal stem cell transplantation. In the acute stage, amniotic membrane transplantation probably has a protective role against the progressive melting and perforation.

Thermal comparison of the AdvanTec Legacy, Sovereign WhiteStar, and Millennium phacoemulsification systems

PURPOSE

To determine the operating temperature of ultrasonic tips used with the Alcon AdvanTec Legacy, AMO Sovereign WhiteStar, and Bausch & Lomb Millennium phacoemulsification systems.

SETTING

Mackool Eye Institute, Astoria, New York, New York, USA.

METHODS

Thermal imaging of ultrasonic tips (Legacy, WhiteStar, and Millennium) was performed in air and in human cadaver eyes using a duty cycle of 33% (WhiteStar) and 50% (Millennium and Legacy). In vitro temperatures were measured with the tip centered in the incision and intentionally decentered against the side of the incision. The stroke length of each instrument was also measured, and the operating frequency of the Legacy was evaluated with the addition of a tangential load.

RESULTS

Open air and in vitro testing demonstrated that tip temperatures with the Legacy were consistently the lowest. Temperatures measured with the WhiteStar and Millennium systems were higher and generally similar to each other. At identical console power settings, the stroke length of the WhiteStar and Millennium tips was longer than that of the Legacy. The frequency of the Legacy handpiece did not change significantly (less than 200 Hz) under conditions of tangential tip loading.

CONCLUSIONS

At identical console power settings and similar console duty cycles, the temperature elevation of ultrasonic tips was least for the Legacy and greater for the WhiteStar and Millennium under all conditions. The causes of these findings appear to be the longer stroke length of the WhiteStar and Millennium and the underestimation of the duty cycle with the WhiteStar.

[Fluorescence angiography of the anterior eye segment in the evaluation of impaired microcirculation within the diagnosis of severity of eye burns]

We used fluorescence angiography to study the vascular microcirculation in the anterior eye segment of 14 patients with severe eye bums. The severity of eye burns is not only related with an impaired blood circulation in the conjunctiva, it also depends on a microcirculation status of episcleral vessels. Different degrees of permeability of fluorescein through the conjunctival or episcleral vessels make it possible to specify circulation disorders in both cases. Whether the impaired microcirculation in the anterior eye segment is transient or not can be established through a second fluorescence angiography made during days 7-8 from the burn trauma. The severity of eye burn depends directly on the sizes of ischemic regions of the sclera.

Physiopathologie des brûlures oculaires

Eye burns are frequent among eye traumas. They induce different effects on the ocular structures, depending on the type of burn: chemical, with an important difference between acids and bases, thermal, or ionizing rays. The physiopathology of eye burns reflects the different stages of progression, with a first stage of destruction, a second stage of cleaning and inflammation, and a last stage of reconstruction and scarring. The final prognosis depends on the initial lesions, not only involving the eye ball, but also the conjunctiva and eyelids. Chemical burns by basic fluids have the worst prognosis because they are able to penetrate the tissues quickly. Burns by acids have a better prognosis and thermal burns are located only at the injured area. Treatment is most effective at the initial stage of destruction and can dramatically change the prognosis. The secondary phase of cleaning includes the entire biochemical cascade of inflammation and the production of proteases. At this stage, treatment can be effective but must be closely monitored because it can inhibit progression to the last stage of scarring. At the scarring stage, neovascularization begins, induced by initial ischemia, the reconstruction of epithelium with a probable role of stem cells, the reconstruction of nerve fibers depending on the nerve growth factor (NGF), and the reconstruction of extracellular matrix in which matrix metalloproteinases (MMPs) are essential. At this stage, therapy can only be surgery of functional after effects and esthetic anomalies.

Changes of uPA and uPA-R expression in the cornea after alkali burn

PURPOSE

To investigate the expression levels of uPA and uPA-R in corneal repair after alkali burn.

METHODS

The corneal alkali burn models were established in vitro and in vivo, then immunocytochemistry (ICC) of uPA/uPA-R and image analysis and statistical evaluation were performed to determine their expression levels both in vitro and in vivo.

RESULTS

Compared with control group, the expressions of uPA and uPA-R after alkali burn had no significant increases till 6h, then increased rapidly from 12h to 24h and reached their maxima at 24h. From 24h, their expression levels decreased rapidly. In vivo, they rebounded again after 48h and attained their second peaks at 96h, respectively. After that, their expressions decreased again. The uPA-positive reaction mainly distributed in the cytoplasm while that of uPA-R mostly distributed on the cellular membrane. Their expression changes were similar to each other, both in vivo and in vitro. In vivo, uPA and uPA-R expressed and gathered in the basal layer of corneal epithelium.

CONCLUSIONS

These results suggest that the time phase of 24h after wound is the typical stage associating with the expressional maximum of uPA and uPA-R both in vivo and in vitro. Furthermore, the results also imply that the expression changes of uPA and uPA-R correlate to the wound healing after the corneal alkali burn, uPA and uPA-R coordinate with each other to stimulate the wound healing.

Legacy AdvanTec and Sovereign WhiteStar

PURPOSE

To assess the wound temperature of the Sovereign WhiteStar (S-WS) (AMO) and Legacy AdvanTec (L-ADV) (Alcon) phacoemulsification systems.

SETTING

John A. Moran Eye Center, Health Sciences Center, University of Utah, Salt Lake City, Utah, USA.

METHODS

Phacoemulsification using 20-gauge, 30-degree straight tips with the L-ADV and S-WS systems was performed in fresh cadaver eyes. The power was set at 50%, and aspiration was 12 mL/min; the L-ADV was run at 15 pulses per second (pps) and the S-WS at WS CF (6 milliseconds on, 12 milliseconds off). Temperature was measured at 5-second intervals for 60 seconds using a microthermistor placed in the wound. The phaco tip was angled 30 degrees to increase wound-tissue contact. At 10 seconds, the flow was clamped to simulate occlusion. Five runs, sleeved and unsleeved, were averaged for the phaco tip.

RESULTS

The mean temperature was significantly higher with L-ADV than with S-WS (from 10 seconds on in the sleeved condition and from 5 seconds on in the unsleeved condition after the aspiration line was clamped). In 2 of 5 sleeved runs and 4 of 5 unsleeved runs, the L-ADV handpiece decreased power as the temperature increased. One run with the L-ADV with sleeve showed signs of wound burn. There were no signs of wound burn with the S-WS. The highest temperature recorded was 57.5 degrees C with the L-ADV and 38.6 degrees C with the S-WS. Power tests showed L-ADV protected the stroke length and S-WS had constant power except in air where it increased power.

CONCLUSIONS

There was less increase in wound temperature over time with the S-WS than with the L-ADV system in sleeved and unsleeved simulated surgery in human eye-bank eyes. Because the ultrasound handpieces respond differently under different load scenarios, meaningful comparisons of pulsing features are difficult to create.

Bimanual phacoemulsification through 2 stab incisions. A wound-temperature study

PURPOSE

To determine the thermal parameters of bimanual ultrasound-based phacoemulsification through 2 stab incisions with a bare aspiration needle.

SETTING

In vitro laboratory.

METHODS

The Sovereign phacoemulsification unit (Allergan) was used in 3 modes in conjunction with the Olson irrigating chopper (ASICO) in 6 fresh human cadaver eye-bank eyes to determine the temperature at which a wound burn would occur. A wound burn was defined as temperature exceeding 45 degrees C, whitening around the wound, or wound contraction.

RESULTS

One hundred percent ultrasound power was required to create a wound burn in the unoccluded mode in continuous ultrasound and the burst mode. The time to create the wound burn was 160 and 180 seconds in 2 eyes in continuous ultrasound and 42 and 50 seconds in 2 eyes in the burst mode; it was 58 and 70 seconds in continuous ultrasound with complete occlusion and required 80% power.

CONCLUSIONS

The energy necessary to obtain a wound burn during 2-incision bimanual ultrasound-based phacoemulsification with a bare aspiration needle in human cadaver eyes was extremely high. The parameters necessary to create a wound burn in each modality occurred well beyond normal clinical settings and provide evidence that 2-stab ultrasound-based lens extraction can be performed safely with the Sovereign machine.

Microphacoemulsification with WhiteStar. A wound-temperature study

PURPOSE

To verify the temperature-induction effect of bimanual ultrasound-based phacoemulsification through 2 stab incisions with a bare aspiration needle and new proprietary technology.

SETTING

In vitro laboratory.

METHODS

The Sovereign phacoemulsification unit and the WhiteStar system (Allergan) were used in conjunction with the Olson irrigating chopper (ASICO) and a 19-gauge bare phaco needle in 2 human cadaver eye-bank eyes at 100% power unoccluded, 100% power with aspiration completely occluded, and 100% power with aspiration and flow completely occluded. Temperature data were monitored throughout the experiment. Any sign of a wound burn, defined as temperature exceeding 45 degrees C, whitening around the wound, or wound contraction, was the end point.

RESULTS

At 100% continuous phacoemulsification power, the temperature did not rise above 27.3 degrees C. When the aspiration line was totally occluded at 100% continuous power, the temperature did not rise above 32.5 degrees C. When flow into the eye and aspiration were completely occluded at 100% power, a wound change and temperature of 45 degrees C occurred in 45 seconds in the first eye and in 29 seconds in the second eye.

CONCLUSIONS

Using the Sovereign phacoemulsification unit with the WhiteStar system during 2-stab-incision bimanual microphacoemulsification with a bare 19-gauge aspiration needle in human cadaver eyes, a wound burn could not be produced at the highest energy settings unless all flow into the eye and all aspiration were occluded. These settings were well beyond clinically applicable conditions and provide evidence that microphacoemulsification can be performed safely with the WhiteStar system.

[Blood-eye barrier in the acute period of experimental severe alkaline burn of the eye by injection of deoxyglucose into the central vein]

The permeability of the blood-eye barrier for 14C-labeled deoxyglucose injected intravenously was studied on a model of severe experimental eye burn in 12 rabbits (24 eyes). The barrier permeability was evaluated by the content of radioactive material in the burnt eye humor in comparison with intact eye. Analysis of radiometric data showed a significant difference in the content of 14C in damaged and intact eyes. The permeability of the blood-eye barrier was increased in the damaged eye, this permeability depending on the concentration of the agent in the blood.

Management of alkali burns : an 11-year retrospective review

OBJECTIVE

To review the spectrum of patients with alkali burns admitted over an 11-year period and to assess the clinical outcomes after the introduction of a standard alkali burn treatment protocol.

DESIGN

Retrospective nonrandomized comparative study.

PATIENTS AND INTERVENTIONS

A total of 121 patient records with alkali burns (n = 177 eyes) admitted to a tertiary hospital between 1987 and 1998 were reviewed. Eyes treated with a standard alkali burn treatment protocol, which included intensive topical steroids, ascorbate, citrate, and antibiotics, were compared with eyes treated by conservative management with antibiotics, and a short course of steroids.

MAIN OUTCOME MEASURES

Time to corneal reepithelialization, final best-corrected visual acuity, and time to visual recovery, length of hospital stay, and complications were analyzed.

RESULTS

The standard protocol tended to delay corneal reepithelialization by one day (P: = not significant) in eyes with grade 1 burns (n = 76) and by 2 days (P: = 0.04) in grade 2 burns (n = 52), with no difference in final visual outcome. There were 37 eyes with grade 3 burns. Those treated with the standard protocol showed a trend toward more rapid corneal reepithelialization. Twenty-seven of 29 (93%) eyes with grade 3 injuries achieved a final best-corrected visual acuity of 20/40 or better compared with 3 of 6 (50%) eyes not treated according to the standard protocol (P: = 0.02). Eyes with grade 4 burns (n = 12), whether treated with the standard protocol or not, required 10 to 12 weeks for corneal reepithelialization. There was no statistically significant difference in final visual acuity.

CONCLUSIONS

On the basis of our findings, a number of recommendations can be made for the management of alkali injuries. Patients with a grade 1 or 2 injury do not require routine admission and do not benefit from the use of intensive treatment with ascorbate and citrate. A trend toward more rapid healing and a better final visual outcome were apparent in grade 3 burns, but our standard protocol made no difference in grade 4 burns.

Nerve growth factor promotes corneal healing: structural, biochemical, and molecular analyses of rat and human corneas

PURPOSE

A recent clinical report demonstrated that topical nerve growth factor (NGF) treatment in patients affected by corneal neurotrophic ulcers induced epithelial and stromal healing restoring corneal integrity. Mechanisms(s) undergoing these clinical NGF actions are still unclear. The aim of this study was to investigate the role of NGF in human and rat cornea physiopathology.

METHODS

Expression of high-affinity NGF receptors, NGF-mRNA, and NGF protein was evaluated in human and rat normal corneas, in human and rat corneal epithelial cell cultures, in human corneal organ culture, and in the rat cornea after an experimental model of epithelial injury, by means of immunohistochemistry, in situ hybridization reverse transcription-polymerase chain reaction, and enzyme-linked immunosorbent assay.

RESULTS

The resultant data demonstrated that NGF is a constitutive molecule present and produced in normal human and rat corneas. In vitro human and rat corneal epithelial cells produce, store, and release NGF and also express high-affinity NGF receptors (TrkA). In human organ culture, epithelium, keratocytes, and endothelium have been shown to bind exogenous radiolabeled NGF, and the epithelial cells' binding was increased after epithelium injury. In vivo, after rat corneal epithelial injury, a transient increase of corneal NGF levels was observed. Inhibition of endogenous NGF activity by neutralizing anti-NGF antibodies delayed the corneal epithelial healing rate, whereas exogenous administration of NGF accelerated healing.

CONCLUSIONS

Taken together, the above findings show that NGF plays an important role in corneal physiopathology and suggest that this neurotrophin may exert therapeutic action in wide-spectrum corneal diseases.

Long term results after autologous nasal mucosal transplantation in severe mucus deficiency syndromes

AIM

Severe mucus deficiency syndromes may require substitution of mucous membrane for re-establishment of the ocular surfaces. The long term results after autologous nasal mucosal transplantation were investigated.

METHODS

55 eyes of 50 patients with severe mucus deficiency syndromes were followed retrospectively after free autologous nasal mucosal transplantation-group A: patients after severe lye, acid, heat burns, or radiation (n=38 eyes), group B: patients with systemic mucosal disease (n=17 eyes). The results of routine clinical examination were recorded and patients were followed for a median of 37 months. 17 biopsies of transplanted nasal mucosa were studied by light microscopy and 22 patients by impression cytology before and at several intervals after mucosal transplantation.

RESULTS

All nasal mucosal grafts healed well and no intraoperative complications occurred. During follow up 107 additional surgical procedures were performed including 16 lamellar and 21 penetrating keratoplasties. Subjective complaints improved in 44/47 patients with preoperative symptoms. Best corrected visual acuity at the end of follow up was increased in 23 eyes, 10 eyes (18. 2%) reached a final visual acuity equal to or greater than 20/200. Histopathologically, all (n=17) biopsies showed vital intraepithelial mucin producing goblet cells in the nasal mucosal graft (median 25 cells/field (400x magnification)). The mean density of goblet cells before transplantation was 48/mm(2) and after nasal mucosal grafting 432/mm(2) measured by impression cytology (p<0. 0001).

CONCLUSIONS

Functional goblet cells persist in autologous nasal mucosa for up to 10 years after transplantation. In patients with severe mucus deficiency syndromes of different origin nasal mucosal transplantation can re-establish the ocular surface, substitute the mucus components of the tear film, improve symptoms of the patients, and facilitate a moderate increase in visual acuity.

The effect of propolis extract in experimental chemical corneal injury

PURPOSE

To investigate the effect of propolis, a natural resin produced by honeybees, in the treatment of alkali-injured rabbit eyes.

METHOD

A corneal alkali burn was induced by applying filter paper immersed in 1 N NaOH on the central axis of the right corneas of 24 rabbits for 30 s. The animals were divided into three treatment groups: group 1 (control) was given 0.3% tobramycin and phosphate-buffered solution; group 2 was treated with antibiotic coverage and topical 1% ethanolic extract of propolis; group 3 received antibiotic coverage and topical 1% dexamethasone. The dexamethasone-treated group was maintained as the positive control. Drugs were instilled 4 times a day for 7 days. The corneal inflammation was evaluated by calculating the average inflammatory index obtained from clinical observation of the ciliary hyperemia, central and peripheral corneal edema at 24 h, 48 h, on day 5 and day 7, before sacrificing the animals. Then, the corneas underwent routine histological examination.

RESULTS

The effects of dexamethasone and propolis on healing of injured corneas were similar (p>0.05) and significantly better than controls at 24 h (p<0.01, p< 0.05, respectively), and on day 7 (p<0.05) with respect to the inflammatory index. On histological observation, inflammatory cell infiltration was lower as compared to control in both the dexamethasone and propolis groups (p<0.001) and similar with each other (p>0.05).

CONCLUSIONS

Our study shows that propolis has an anti-inflammatory effect comparable to dexamethasone in chemical corneal injury.

[Observation of the endothelial healing in rabbit corneal alkali wounds by alizarin red S-trypan blue staining method]

PURPOSE

To study the healing of the corneal endothelial cells in rabbit corneal alkali wounds.

METHODS

26 New Zealand white rabbits were used. A alkali wound was created with a round filter paper, 8 mm in diameter, which was soaked in 0.5 N NaOH for 5 seconds and was placed centrally on the cornea for 60 seconds. The rabbits were killed in 20 minutes; 1, 2, 6, 12 h; 1, 2, 3, 5, 7, 10, 14, 30 days after injury. The corneal endothelium was examined in the light microscope using a lizarin red S-trypan blue staining method.

RESULTS

Twenty minutes after the wound, the corneal endothelial cells were destroyed. 72 hours following the wound, the endothelial cells surrounding the burns became larger, irregular and started to migrate onto the denuded descemet's membrane. The endothelial cells covered the burn with the spindle-shaped cells 7 days after wound.

CONCLUSION

The endothelial damage is healed by the division and migration of remaining endothelial cells at the margin of the wound, which has some characters of fibroblast.

Krill protease effects on wound healing after corneal alkali burn

PURPOSE

To study the effect of a novel protease in the development and progression of corneal ulceration secondary to alkali burning.

METHODS

By using a 4N alkali burn model of corneal ulceration in rabbits, the effects and efficacy of topical application of a novel protease (PHM-101) capable of degrading metalloproteinases was studied for 28 days of treatment and 7 days off treatment for its effect on corneal ulceration and recurrent erosion.

RESULTS

At day 28, both the protease- and placebo-treated groups had different numbers of eyes showing reepithelialization (nine (45%) of 20 and six (33%) of 18, respectively]. By day 35 the protease-treated group had significantly fewer recurrent epithelial defects [two (13%) of 15 vs. eight (61%) of 13; p = 0.02]. Similarly, at day 35 the protease-treated group showed significantly less corneal ulceration [two (13%) of 15 vs. six (46%) of 13; p = 0.02], and those ulcers were of a lesser severity (three units vs. 17.76 units). No difference was found in the degree of stromal edema or neovascularization, nor was there any difference in histopathologic characteristics of inflammatory cell infiltration and corneal scarring.

CONCLUSION

We conclude that this novel protease is efficient in reducing recurrent corneal epithelial defects and stromal ulceration after alkali burning.

[The experimental investigation of epithelial healing in rabbit central corneal alkali wounds]

PURPOSE

To observe the morphologic changes of epithelium in the alkali wounds at the central corneal of rabbits.

METHODS

38 rabbits weighing 2.5 kg were used. A alkali wound of the corneas was performed in the right eye of 38 New Zealand white rabbits with round filter paper, 8 mm in diameter, which were soaked in 0.5 mol/L NaOH for 5 seconds and then were placed centrally on the cornea for 60 seconds. The corneal burns were examined and photographed after the staining of 2% fluoresent staining with a slit lamp every day. The excised corneas were examined in the light microscope, electron microscope.

RESULTS

The epithelial cells had rapidly disappeared in the burned area. The epithelial cells regrowth started at 8 hours following the burn, and 1-2 layers epithelial cells covered the burned area by 24 hours. The epithelial defects occured again on the 4th day. The desmosome and microvilli of the regenerating epithelium had a reduced number. There was no basement membrane between the regenerating epithelium and the strom. There were increased intercellular spaces between the regenerating epithalial cells.

CONCLUSION

The epithelial healing were achieved through the division and migration of epithelial cells at the margin of the wound in rabbit central corneal alkali wound. The decrease of the junctions and the increase of intercellular spaces between the regenerating epithalial cells may be responsible for the second epithelial defects.

Strampelli osteo-odonto-keratoprosthesis: case report

Case report of a patient equipped with an osteo-odonto-keratoprosthesis in both eyes (left in 1968 and right in 1971). The left eye was recently enucleated because of unbearable pain, in an eye without light perception since 20 years. The histology shows an ancient retinal detachment and an eye completely filled with blood. Indications and complications of the technique are discussed.

Video fluorescein angiography of the anterior eye segment in severe eye burns

PURPOSE

Severe eye burns often result in extensive necrosis of the conjunctiva and episcleral tissue. Video fluorescein angiography was performed to reveal the perfusion of the anterior eye segment after severe eye burns.

METHODS

A scanning laser ophthalmoscope was used for anterior segment fluorescein angiography in 12 patients (14 eyes) with severe burns grade III-IV and in 7 healthy volunteers.

RESULTS

Necrotic tissues occurred as non perfused areas and remained dark throughout the whole angiogram. In general, the borders from healthy to necrotic conjunctival tissue were sharply demarcated. Thus, the extent of scleral and limbal ischemia could be determined exactly. Injured vessels showed hyperfluorescence with late leakage. Damage of the subconjunctival tissue appeared as a deep weak fluorescence in the early angiography and exhibited patchy leakage in the late angiogram.

CONCLUSIONS

Anterior segment angiography provides a basis for deciding the extent of surgical debridement of necrotic tissue in the acute phase of the burn. The determination of the extent of limbal and scleral ischemia may give useful information for early plastic-reconstructive procedures.

Alkali burn-induced synthesis of inflammatory eicosanoids in rabbit corneal epithelium

PURPOSE

Alkali burning of the rabbit cornea is a well-established model for the study of anterior surface inflammation, neovascularization, and wound-healing processes. 12-hydroxyeicosanoids have been implicated as mediators of such responses. 12(S)-hydroxyeicosatetraenoic acid (12[S]-HETE) is a lipoxygenase-derived arachidonate metabolite and 12(R)-hydroxyeicosatetraenoic acid (12[R]-HETE) is formed by a cytochrome P450 monooxygenase; both give rise to the potent angiogenic factor 12(R)-hydroxyeicosatrienoic acid (12[R]-HETrE). In this study, the authors correlate the pattern of their synthesis in the corneal epithelium with the inflammatory response after alkali injury.

METHODS

New Zealand albino rabbits were anesthetized and alkali burns created with 10-mm filter paper discs (1 N NaOH for 2 minutes). Corneas were then rinsed; 1 to 7 days later, corneal epithelium was scraped and used to assess 14C-arachidonic acid conversion to 12-HETE and 12-HETrE enantiomers in the presence of NADPH by chiral high-pressure liquid chromatography. The inflammatory response secondary to the alkali burn was quantified through area measurements of reepithelialization and neovascularization.

RESULTS

Alkali burn induced a time-dependent production of corneal epithelial 12-HETE and 12-HETrE. A marked increase in 12-HETE and 12-HETrE synthesis was evident at day 2 (from 22 +/- 7 to 139 +/- 22 ng/hour) after injury, increasing to 800 +/- 68 ng/hour at day 7. Chiral analysis revealed a time-dependent synthesis of the R and S enantiomers of 12-HETE (24% R, 76% S) and 12-HETrE (72% R, 28% S). Total arachidonate metabolism, as well as the formation of 12(R)-HETrE, correlated with the area of neovascularization (P < 0.01 and P < 0.02, respectively).

CONCLUSIONS

The results demonstrate that surviving and regenerating epithelium has an increased capacity of synthesizing 12(S)-HETE and 12(R)-HETE and that maximal production of 12(R)-HETrE, a known direct and indirect angiogenic factor, coincides with neovascularization in this model. Thus, the lipoxygenase and cytochrome P450-dependent activities increased in a time-dependent manner, indicating the potential involvement of both pathways in the inflammatory response to alkali burn. The formation of significant quantities of 12(R)-HETE and 12(R)-HETrE is a novel finding in this alkali injury model.

Effect of synthetic metalloproteinase inhibitor or citrate on neutrophil chemotaxis and the respiratory burst

PURPOSE

A topical synthetic metalloproteinase inhibitor (SIMP) has been reported to reduce the incidence of corneal ulcerations in the alkali-injured eye by the putative mechanism of collagenase inhibition. The current study was performed to determine whether SIMP has a direct inhibitory effect on the activation of neutrophils and to compare any such effect with that of citrate, a known inhibitor of polymorphonuclear leukocyte (PMNL) activity.

METHODS

The effect of SIMP or citrate was tested on chemotaxis of PMNL and the respiratory burst in vitro.

RESULTS

Synthetic metalloproteinase inhibitor (1 mM) or citrate (12 mM) produced significant inhibition of chemotaxis of PMNL and the accompanying behavioral characteristics of motility. Synthetic metalloproteinase inhibitor, but not citrate, generated a dramatic respiratory burst when incubated with resting PMNL. Both SIMP and citrate inhibited the respiratory burst of PMNL in the presence of opsonized zymosan. For a brief, initial period each substance enhanced the respiratory burst generated by the metabolic stimulant from alkali-degraded corneas, followed by a rapid decline in activity that was associated with cell death.

CONCLUSIONS

Although SIMP has been shown to exhibit powerful collagenase inhibition, its inhibitory effect on chemotaxis of PMNL might be the primary mechanism in reducing the incidence of ulceration in the alkali-injured cornea. Very significant reduction in the accumulation of PMNL in SIMP-treated corneas supports this conviction. Activation by SIMP of the respiratory burst in resting PMNL is of concern, but overall its beneficial effect is favorable, as demonstrated in prior alkali-injured animal models. The dual effect of inhibition of chemotaxis of PMNL and activity of collagenase makes SIMP a potential drug for combating ulceration in the alkali-injured cornea.