The Role of Nitric Oxide in Ocular Surface Cells

The role of nitric oxide (NO) in the ocular surface remains unknown. We investigated the conditions leading to an increase of NO generation in tear and the main sources of NO in ocular surface tissue. We evaluated the dual action (cell survival or cell death) of NO depending on its amount. We measured the concentration of nitrite plus nitrate in the tears of ocular surface diseases and examined the main source of nitric oxide synthase (NOS). When cultured human corneal fibroblast were treated with NO producing donor with or without serum, the viabilities of cells was studied. We found that the main sources of NO in ocular surface tissue were corneal epithelium, fibroblast, endothelium, and inflammatory cells. Three forms of NOS (eNOS, bNOS, and iNOS) were expressed in experimentally induced inflammation. In the fibroblast culture system, the NO donor (SNAP, S-nitroso-N-acetyl-D, L-penicillamine) prevented the death of corneal fibroblast cells caused by serum deprivation in a dose dependent manner up to 500 micrometer SNAP, but a higher dose decreased cell viability. This study suggested that NO might act as a doubleedged sword in ocular surface diseases depending on the degree of inflammation related with NO concentration.

Risk Factors for Posterior Capsular Rupture in Cataract Surgery

PURPOSE: The purpose of this study was to evaluate the risk factors for posterior capsular rupture in cataract surgery (phacoemulsification or ECCE). METHODS: The charts of patients who had cataract surgery between March 1993 and May 2000 were reviewed retrospectively. Probable risk factors included age, sex, operated eye (right or left), type of surgery, preoperative visual acuity, presence of diabetes mellitus, diabetic retinopathy, hypertension, glaucoma, corneal disease, type of cataract, history of posterior capsular rupture in the other eye (if operated), axial length of the eye, and anterior chamber depth. We compared 63 patients who had posterior capsular rupture with 65 randomly selected patients who had no complications, using statistical analysis. RESULTS: The type of surgery (p<0.0005), presence of diabetic retinopathy (p<0.05) and type of cataract (p<0.05) were significant risk factors. The others were not statistically significant with posterior capsular rupture in cataract surgery. CONCLUSIONS: Patients with risk factors for posterior capsular rupture such as diabetic retinopathy, mature and mixed cataract should be carefully operated by experienced surgeons.

Anterior Chamber Phakic Intraocular lens in Patients with high Myopia

PURPOSE: Anterior chamber phakic intraocular lenses are one of the modalities used to correct high myopia. This study aimed to report the results of implantation of anterior chamber phakic intraocular lenses in high myopia patients. METHODS: Angle-supported phakic intraocular lens(Phakic 6(R), Ophthalmic Innovations Int.) with very flexible haptics for less pupillary distortion and an optical zone of 6mm was implanted in 4 eyes of 2 patients with high myopia. Efficiency, safety, and complications were evaluated preoperatively and at least 6 months postoperatively. The effect of the procedure on the cornea, pupil, and anterior chamber angle were studied. RESULTS: The preoperative mean spherical equivalent refraction was -20.06+/-2.05 D. The postoperative mean spherical equivalent refraction was -1.41+/-0.57 D at 6 months following the operations. The patients' best corrected visual acuity improved 1 line or more at 6 months compared with preoperative values. Significant endothelial cell loss or cataract formation were not demonstrated in any case during the study. Anterior chamber reformation or iridectomy was needed postoperatively in 2 eyes because of ocular hypertension associated with pupillary block. CONCLUSIONS: The results of this study indicate that phakic anterior chamber intraocular lens implantation may be an effective surgical alternative for the correction of high myopia. However, long term follow-up is needed because of the complications such as cataract formation, endothelial cell loss, and ocular hypertension.

The Clinical Efficacy of Amniotic Membrane Transplantation and Limbal-Conjunctival Autograft in Patients with Recurrent Pterygium or Pseudopterygium

PURPOSE: To evaluate the clinical efficacy of amniotic membrane transplantation and limbal-conjunctival autograft for patients with recurrent pterygium or pseudopterygium, the results of 15 eyes of 14 patients were analyzed. METHODS: Total 10 cases of recurrent pterygium and 5 cases of pseudopterygium were surgically managed during June 1998 to July 2000. After excision of pterygium, amniotic membrane was attached on the bare sclera and limbal-conjunctival autograft was transplanted over the amniotic membrane. Mean follow-up period was 47.2 week and all patients were examined for recurrence, which was graded from G0(no vessel) to G3(fibrotic tissue invading the limbus). RESULTS: 12 out of 15 cases(rate 80%) showed no recurrence(grade 0). 1 case of grade 2 recurrence and 2 cases of grade 3(total 3 cases) were observed(rate 20%). Reoperation was performed on 2 cases of grade 3 recurrence. There was no further recurrence necessitating additional reoperation. 1 case of limbal graft was detached and removed. The operation time of this more prolonged than the other procedures, but there were no significant complications. CONCLUSION: Amniotic membrane and limbal-conjunctival autograft for patients with recurrent pterygium or pseudopterygium reconstructed complete ocular surface with less recurrence. Therefore, we recommend this surgical approach as a safe and effective method for the treatment of complicated cases of pterygium.

The role of nitric oxide in ocular surface diseases

The role of nitric oxide (NO) in ocular surface diseases remains unknown. We investigated the conditions leading to increase NO generation in tears and the main sources of ocular surface tissue. We evaluated the possibility of a dual action (cell survival or cell death) depending on the amount of NO. The concentration of nitrite plus nitrate, the stable end-product of NO, was measured in the tears of various ocular surface diseases. We also examined the main source of nitric oxide synthase (NOS) using immunohistochemical staining & Western blot analysis. When cultured human corneal fibroblasts were treated with NO producing donor with or without serum, the viability of cells was studied. We found that sources of NO in ocular surface tissue primarily included corneal epithelium, fibroblasts, endothelium and inflammatory cells. Three forms of NOS (eNOS, bNOS, & iNOS) were expressed in experimentally induced inflammation. Cell death by NO revealed TUNEL positive staining, however in the EM finding, this NO specific cell death was an atypical necrosis showing perinuclear large vacuolization and mitochondrial swelling. In the fibroblasts culture system, the NO donor (SNAP, S-nitroso-N-acetyl-D, L-penicillamine) prevented the death of corneal fibroblasts caused by serum deprivation in a dose dependent manner up to 500 m SNAP, although a higher dose decreased cell viability. This study suggested that NO might act as a double-edged sword in ocular surface disease depending on the degree of inflammatory condition related with NO concentration.

Bilateral Infectious Keratitis following Photore fractive Keratectomy

PRK is presumed to be safe with a high success rate and few complications.However, since epithelial defects created by surgery disrupt corneal barrier function, infectious keratitis may occur.We experienced a case of bilateral infectious keratitis after PRK in a 32 years old woman who had complained of pain and blurred vision in both eyes.To our knowledge, no bilateral infectious keratitis after PRK has been reported in the literature. In our case, we presumed that infectious keratitis after PRK occurred due to therapeutic soft contact lenses, possibility of intraoperative contamination, physical stress or ultraviolet radiation.Although the causative organism was not identified on culture, clinical pattern of keratitis was similar to bacterial infection.The patient was treated with maximal topical antibiotics on both eyes and with amniotic membrane patching in the left eye.After proper management, the patient'suncorrected visual acuity had returned to 1.0/0.9 in Snellen chart. This case emphasizes the need for an informed consent for postoperative complications, careful preoperative examination, and proper management.