The ex vivo eye irritation test (EVEIT) model as a mean of improving venom ophthalmia understanding

Snakes belonging to the genus Naja (Elapid family), also known as "spitting cobras", can spit venom towards the eyes of the predator as a defensive strategy, causing painful and potentially blinding ocular envenoming. Venom ophthalmia is characterized by pain, hyperemia, blepharitis, blepharospasm and corneal erosions. Elapid venom ophthalmia is not well documented and no specific treatment exists. Furthermore, accidental ejection of venom by non-spitting vipers, as Bothrops, also occurs. The Ex vivo Eye Irritation Test model (EVEIT) has enabled important progress in the knowledge of chemical ocular burns. Considering the lack of experimental animal model, we adapted the EVEIT to study venom ophthalmia mechanisms. Ex vivo rabbit corneas were exposed to venoms from spitting (Naja mossambica, Naja nigricollis) and non-spitting (Naja naja, Bothrops jararaca and Bothrops lanceolatus) snakes, and rinsed or not with water. The corneal thickness and the depth of damage were assessed using high-resolution optical coherence tomography (HR-OCT) imaging and histological analysis. All Naja venoms induced significant corneal edema, collagen structure disorganization and epithelial necrosis. Corneas envenomed by African N. mossambica and N. nigricollis venoms were completely opaque. Opacification was not observed in corneas treated with venoms from non-spitting snakes, such as the Asian cobra, N. naja, and the vipers, B. jararaca and B. lanceolatus. Moreover, Bothrops venoms were able to damage the epithelium and cause collagen structure disorganization, but not edema. Immediate water rinsing improved corneal status, though damage and edema could still be observed. In conclusion, the present study shows that the EVEIT model was successfully adapted to set a new experimental ex vivo animal model of ophthalmia, caused by snake venoms, which will enable to explore new therapies for venom ophthalmia.

The Ex vivo Eye Irritation Test (EVEIT) model as a mean of improving venom ophthalmia understanding

Snakes belonging to the genus Naja (Elapid family), also known as "spitting cobras", can spit venom towards the eyes of the predator as a defensive strategy, causing painful and potentially blinding ocular envenoming. Venom ophthalmia is characterized by pain, hyperemia, blepharitis, blepharospasm and corneal erosions. Elapid venom ophthalmia is not well documented and no specific treatment exists. Furthermore, accidental ejection of venom by non-spitting vipers, as Bothrops, also occurs. The Ex vivo Eye Irritation Test model (EVEIT) has enabled important progress in the knowledge of chemical ocular burns. Considering the lack of experimental animal model, we adapted the EVEIT to study venom ophthalmia mechanisms. Ex vivo rabbit corneas were exposed to venoms from spitting (Naja mossambica, Naja nigricollis) and non-spitting (Naja naja, Bothrops jararaca and Bothrops lanceolatus) snakes, and rinsed or not with water. The corneal thickness and the depth of damage were assessed using high-resolution optical coherence tomography (HR-OCT) imaging and histological analysis. All Naja venoms induced significant corneal edema, collagen structure disorganization and epithelial necrosis. Corneas envenomed by African N. mossambica and N. nigricollis venoms were completely opaque. Opacification was not observed in corneas treated with venoms from non-spitting snakes, such as the Asian cobra, N. naja, and the vipers, B. jararaca and B. lanceolatus. Moreover, Bothrops venoms were able to damage the epithelium and cause collagen structure disorganization, but not edema. Immediate water rinsing improved corneal status, though damage and edema could still be observed. In conclusion, the present study shows that the EVEIT model was successfully adapted to set a new experimental ex vivo animal model of ophthalmia, caused by snake venoms, which will enable to explore new therapies for venom ophthalmia.

Rinsing with isotonic saline solution for eye burns should be avoided.

BACKGROUND: Recent approaches to emergency treatment of eye burns have given rise to many questions on the effectiveness of traditional rinsing solutions. This led us to study the use of isotonic saline solution and a recently introduced, highly effective solution, Cederroth Eye Wash, in the initial treatment of eye burns. METHODS: A central area (Ø 10mm) of the cornea of isolated ex vivo rabbit eyes was burnt for 20s with 25+/-1.4 micro L of 2N NaOH. The anterior chamber pH was measured continuously via microelectrode. The corneas were immediately rinsed for 15 min with flow rates of 50, 100, 200, 300, 400, and 500 mL/min. RESULTS: After 20 min measurement, no significant differences in intraocular pH were found between unrinsed eyes and eyes rinsed with isotonic saline solution at any flow rate. At all flow rates, Cederroth Eye Wash brought about a significant decrease (p<0.001; Tukey t-test). CONCLUSIONS: Isotonic saline solution was ineffective in the emergency treatment of severe alkali eye burns in this ex vivo rabbit eye model. Cederroth Eye Wash, even at the lowest flow rate, significantly reduced intracameral pH. Thus a small amount of buffer solution effectively decontaminated the eye, whilst large amounts of saline solution did not.

The consequences of delayed intervention when treating chemical eye burns.

BACKGROUND: Immediate rescue intervention for chemical and thermal eye burns can save the victim's sight. We studied the anterior chamber pH changes immediately after ex vivo eye burn to investigate the effects of immediate and delayed intervention. METHODS: Twenty three enucleated pigs eyes were burnt with 500 microl 2 mol NaOH for 20 s using a cylinder with a diameter of 10 mm. The corneas were rinsed in groups with 1015 ml ordinary tap water at a flow rate of 1.125 ml/s for 15 minutes immediately after burning (n = 6), and after a delay of 20, 40, and 60 s (n = 5, 3 and 4 respectively). One group of eyes was not rinsed (n = 5). The intraocular pH was defined at the start as 'min pH' and the end as 'max pH'(DeltapH = max pH-min pH). RESULTS: The intraocular pH increased sharply in the untreated eyes from a min pH of 6.76 +/- 0.55 to a max pH of 11.85 +/- 0.24, yielding a DeltapH of 5.08. The difference between the timepoint at which the pH began to increase and the speed of change was significantly different between the unrinsed and rinsed eyes, and there was an inverse correlation between this and the time at which rinsing started (p < 0.001). The best results were achieved in eyes rinsed immediately after burning (p < 0.001). The pH in the eyes not rinsed immediately increased rapidly, and in all groups in which rinsing was delayed the max pH was markedly higher (p = 0.093). CONCLUSIONS: Immediate emergency rinsing is essential in eye burn victims. Appropriate rinsing solutions and treatment facilities in the form of rinsing stations where chemical burns may occur must be available at the workplace. Tap water is also effective as a rinsing solution.

Relationship of eye burns with calcifications of the cornea?

INTRODUCTION: The clinical pattern of corneal calcification has been considered to be a part of chronic eye diseases, such as uveitis, severe glaucoma, keratitis and eye burns. Since, in some cases of eye burns, we have found corneal calcifications to be related to the initial calciferous caustic agents and to the use of phosphate-buffer-containing fluids, we have reviewed our files of clinical eye burns for the incidence and appearance of corneal calcification. METHODS: A total of 176 burnt eyes of 98 patients suffering from severe eye burns were retrospectively reviewed. The following data set was acquired: the type of caustic agent, the time of the burns, the delay and type of immediate treatment and the time and type of first aid, the subsequent medication, the clinical grading and the later results. RESULTS: Calciferous burning agents and corneal calcification are correlated (P<0.01). Initial single rinsing with phosphate does not produce corneal calcification (P=0.134). There is evidence that corneal calcifications are correlated with chronically administered phosphate-buffered eye drops (P<0.005). DISCUSSION: Eye burns followed by calcifications follow two different major patterns: the corrosive substance contained calcium or the continued therapy was applied with phosphate-buffered eye drops. We present case reports of three different types of eye burns and later therapy resulting in corneal calcification. Corneal calcifications are presumably related to longer-lasting phosphate application. One suspicious mechanism is the low content of calcium ion stabilizing proteins such as hyaluronate or fetuin in treatments for severe eye burns. The exceeding of the solubility product of Ca(2+) and PO(4) (-) results in the precipitation of calcium phosphates. In cases of chronic corneal disturbance, we recommend the elimination of phosphate-buffered medications to prevent corneal calcification.

Use of an amphoteric lavage solution for emergency treatment of eye burns. First animal type experimental clinical considerations.

PURPOSE: Severe eye burns occur rarely, but are related to a poor prognosis in rehabilitation. As emergency treatment has been identified as decisive factor for the prognosis of eye burns, new first aid rinsing solutions should be considered carefully in their clinical action. In a first approach, the new drug Diphoterine was subjected to a comparison with saline solution to evaluate the effects in a model of severe eye burns. METHODS: In a double-masked experiment 16 rabbits underwent a severe eye burn of one cornea followed by immediate rinsing with 0.9% sodium-chlorine solution (n=8) or Diphoterine (n=8). During 16 days after burn, an irrigation therapy with 0.9% saline solution three times daily 160 ml was applied in both groups following the recommendation of prolonged irrigation therapy performed in our clinic. In a similar setup, 16 eyes were subjected alkali burns with measurements of aqueous humor pH within 30s after burn and after a period of 5 min rinsing with 500 ml saline 0.9% or Diphoterine, respectively. RESULTS: The result of the severe eye burn with an opaque cornea was similar in both groups. During rinsing no fibrin precipitates occurred in the Diphoterine rinsed group whereas this was detectable in all eyes rinsed with saline solution. After 16 days there was no difference between both groups indicating no harmful effect of Diphoterine as emergency treatment compared to saline 0.9%. After 30s of burn with 1N NaOH and rinsing with 500 ml of the specified solutions the anterior chamber pH was 10+/-0 in the saline group and 9.35+/-0.3 in the Diphoterine group showing efficacy of the buffering capacity of Diphoterine. CONCLUSION: Diphoterine proves to be efficient in the primary treatment of burns. The anterior chamber pH could be lowered by 5min of rinsing. No harmful effects of Diphoterine could be observed compared to rinsing with saline solution in the course of an severe alkali burn of the cornea.