Effect of hydrocortisone on the mobilisation of leucocytes in corneal wounds

Critical appraisal of alternative irritation models: three decades of testing ophthalmic pharmaceuticals

BACKGROUND

Testing ocular tolerability of ocular pharmaceuticals is an essential regulatory requirement. The current approved reference model (gold standard) for ocular irritation testing is the Draize test. However this method is subjective and involves using live animals, hence the need to develop alternative in vitro and ex vivo testing strategies.

SOURCE OF DATA

Pubmed, Science Direct, Scopus, Google Scholar, Medline, Current Content, Web of Science and validation reports from international regulatory bodies; The Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM) and European Centre for the Validation of Alternative Methods (ECVAM) were searched for in vitro alternatives.

AREA OF AGREEMENT

Whilst no single in vitro test can effectively replace the Draize eye irritation test, regulatory bodies and cosmetic/pharmaceutical industries agree that there is a need for in vitro alternatives with validated endpoints to evaluate pharmaceutical ingredients and finished eye products.

AREA OF CONTROVERSY

There is no single in vitro test / assay that can predict the ocular irritation potential of mild to moderate test substances.

AREA TIMELY FOR DEVELOPING RESEARCH

This review provides a critical appraisal of the selected in vitro and ex vivo ocular toxicity models recommended by international regulatory bodies. These include cytotoxicity methods, biochemical systems and ex vivo assays. The latter are approved by ECVAM as in vitro alternatives for the well-known Draize test. Hen's egg test-chorioallantoic membrane and the isolated rabbit eye test are also accepted by regulatory agencies in France, Germany, the Netherlands and the UK. A combination of ex vivo assays along with histological examination of excised bovine cornea can predict the conjunctival and corneal tolerability and cover a wider range of ocular pharmaceutical substances.

Detection of anti-lens crystallin antibody in dogs with and without cataracts

OBJECTIVE

To determine if antilens crystallin (ALC) serum and aqueous humor antibodies were present in normal dogs and dogs with cataracts, whether antibody incidence varied with stage of cataract, and whether antibody titer had a relationship to the presence of lens-induced uveitis.

METHODS

Serum and aqueous humor samples were obtained from normal dogs and dogs with cataracts. Lens crystallin was separated by SDS-polyacrylamide gel electrophoresis (SDS-PAGE), and antilens crystallin antibodies were detected by Western immunoblot analysis. An indirect ELISA using crystallin protein as antigen was also used to detect antilens crystallin antibodies in serum and aqueous humor. Test groups included normal, incipient, immature, mature, hypermature and diabetic cataract.

RESULTS

SDS-PAGE identified bands with molecular weights of lens crystallin subunits. Western immunoblotting demonstrated reaction between canine serum and these protein bands. The five canine serum samples that reacted with crystallin subunits on Western blots had corresponding reactivity on the ELISA. All aqueous humor samples (30) were negative. Serum ALC antibodies were detected in 59.3% (16/27) of controls, 66.7% (16/24) of incipients, 50.0% (10/20) of immatures, 37.9% (11/29) of matures, 28.6% (6/21) of hypermatures, and 26.7% (4/15) of diabetics. Serum ALC antibodies were detected in 43.1% (47/109) of all cataract samples. There was a statistically significant negative association between the presence (P = 0.004) and maturity (P = 0.004) of cataract and presence of ALC serum antibodies. In the immature and hypermature cataract groups, there was a statistically significant negative association between ALC serum antibody titer and severity of uveitis (95% confidence interval).

CONCLUSIONS

There is a negative association between the presence (P = 0.004) and maturity (P = 0.004) of cataract and presence of ALC serum antibodies.

Effects of topical diclofenac and prednisolone eyedrops in laser in situ keratomileusis patients

PURPOSE

To compare the effects of a topical nonsteroidal anti-inflammatory agent, diclofenac, and prednisolone acetate on wound healing, postoperative inflammation, and other clinical parameters in laser in situ keratomileusis (LASIK) patients.

SETTING

Fundación VER, Córdoba, Argentina.

METHODS

Laser in situ keratomileusis for myopia was performed simultaneously in both eyes of 16 patients by 1 surgeon. Patients were prospectively randomized to receive diclofenac eyedrops in the right eyes and prednisolone acetate eyedrops in the left. Postoperatively, the drops were administered topically every 2 hours the first day, every 6 hours the first week, every 8 hours the second week, and once a day the fourth week. Preoperatively and at each postoperative visit, evaluation of visual acuity, slitlamp biomicroscopy, corneal topography, and clinical scoring (0-III) of pain and photophobia were done; epithelial interface opacities were objectively evaluated. Follow-up was at 24, 48, and 72 hours, 1, 2, and 3 weeks, and 1, 2, 3, and 6 months. A paired t test was used for statistical analysis.

RESULTS

Mean age of the 16 patients was 29.4 years +/- 6.5 (SD). Preoperatively, mean spherical equivalent was -5.83 +/- 3.61 diopters (D) in the right eyes and -6.96 +/- 4.66 D in the left eyes. At 6 months postoperatively, it was -1.83 +/- 1.87 D and -1.88 +/- 2.13 D, respectively. In the first 24 hours, there were significant clinical symptoms in the diclofenac group.

CONCLUSIONS

Wound healing was stable, with no regression, in the diclofenac and prednisolone groups. Both anti-inflammatory agents worked well in LASIK patients.

Central Focal Interface Opacity After Laser in situ Keratomileusis

BACKGROUND

The acute onset of a focal central interface opacity with visual loss following LASIK has not been described in the peer reviewed literature. Non-peer reviewed reports of various inflammatory lesions have been recorded.

METHODS

We describe three cases in which an acute focal stromal interface opacification was identified within 1 week of laser in situ keratomileusis (LASIK). Each case was performed by a different surgeon on a different day, but using the same method, materials, and the Summit Apex Plus excimer laser. Immediately after surgery, all eyes were normal with good unaided vision. The appearance of the central stromal opacity was associated with acute visual deterioration. Preoperative and postoperative cycloplegic refractions, videokeratography, and postoperative slit-lamp biomicroscopy were performed. Each case was treated with intensive topical corticosteroids.

RESULTS

Each case demonstrated a central circular opacity in the interface between corneal flap and stromal bed, with associated variable stromal thinning. Resolution of the pathological process followed 2 to 4 weeks of treatment with topical corticosteroids and subsequent improvement in slit-lamp biomicroscopy, corneal topography, and vision. Etiology was uncertain.

CONCLUSION

Central interface opacification is a rare but visually important inflammatory complication of LASIK.

Chemical injuries of the eye: current concepts in pathophysiology and therapy

Chemical injuries of the eye may produce extensive damage to the ocular surface epithelium, cornea, and anterior segment, resulting in permanent unilateral or bilateral visual impairment. Pathophysiological events which may influence the final visual prognosis and which are amenable to therapeutic modulation include 1) ocular surface injury, repair, and differentiation, 2) corneal stromal matrix injury, repair and/or ulceration, and 3) corneal and stromal inflammation. Immediately following chemical injury, it is important to estimate and clinically grade the severity of limbal stem cell injury (by assessing the degree of limbal, conjunctival, and scleral ischemia and necrosis) and intraocular penetration of the noxious agent (by assessing clarity of the corneal stroma and anterior segment abnormalities). Immediate therapy is directed toward prompt irrigation and removal of any remaining reservoir of chemical contact with the eye. Initial medical therapy is directed promoting re-epithelialization and transdifferentiation of the ocular surface, augmenting corneal repair by supporting keratocyte collagen production and minimizing ulceration related to collagenase activity, and controlling inflammation. Early surgical therapy if indicated, is directed toward removal of necrotic corneal epithelium and conjunctiva, prompt re-establishment of an adequate limbal vascularity, and re-establishment of limbal stem cell population early in the clinical course, if sufficient evidence exists of complete limbal stem cell loss. Re-establishment of limbal stem cells by limbal autograft or allograft transplantation, or by transfer in conjunction with large diameter penetrating keratoplasty, may facilitate development of an intact, phenotypically correct corneal epithelium. Limbal stem cell transplantation may prevent the development of fibrovascular pannus or sterile corneal corneal ulceration, simplify visual rehabilitation, and improve the visual prognosis. Advances in ocular surface transplantation techniques which allow late attempts at visual rehabilitation of a scarred and vascularized cornea include limbal stem cell transplantation for incomplete transdifferentiation and persistent corneal epithelial dysfunction, and conjunctival and/or mucosal membrane transplantation for ocular surface mechanical dysfunction. Rehabilitation of the ocular surface may be followed, if necessary, by standard penetrating keratoplasty if all aspects of ocular surface rehabilitation are complete, or by large diameter penetrating keratoplasty if successful limbal stem cell transplantation cannot be achieved but other ocular surface rehabilitation is complete.

Steroid inhibition of limbal blood and lymphatic vascular cell growth

Steroids are widely used in the prevention of corneal neovascularization in a wide range of natural and experimental situations. However, no information is available on their effect on the growth of the individual limbal blood vascular cells or of lymphatic cells involved in corneal neovascularization. In addition, tritiated thymidine labelling index is commonly used as an indicator of cell population but doubt exists as to whether it truly represents cell growth. Remote thermal cautery of the rat cornea was used to elicit corneal neovascularization. New cell growth was measured by tritiated thymidine uptake and by the number of cell nuclei per section. Cells investigated were the arteriolar, venular, capillary and lymphatic endothelial cells as well as the arteriolar and venular perivascular cells. A total of 89,320 blood vascular endothelial and perivascular cell nuclei and 12,075 lymphatic nuclei were counted. Thermal cautery elicited a significant increase in labelling index and cell population of all limbal vascular cell types. Steroid application elicited a significant short term inhibition or delay for all six cell types although this was not apparent for venular endothelial cells using labelling index as a growth indicator. At six days only the lymphatic endothelial cell population showed a significant (p < 0.001) increase associated with steroid use.