Color vision, contrast sensitivity and higher order aberrations after photorefractive keratectomy

Purpose: To evaluate the effect of myopic photorefractive keratectomy (PRK) on color vision, contrast sensitivity and higher order aberrations (HOAs).Patients and Methods: This prospective study was performed on 46 eyes of 23 patients with 3 to 6 diopter of myopia/myopic astigmatism undergoing PRK. Color vision using Fransworth- Munsell 100 hue test (©2011 X-Rite Inc., Michigan, U.S) and contrast sensitivity using CSV-1000 (Vector Vision, Dayton, OH) were tested preoperatively and 2 and 6 months postoperatively. HOAs were assessed using Zernike analysis map of Pentacam (OCULUS Optikgeräte GmbH, Germany) preoperatively and 6 months postoperatively.Results: No significant change was observed in color vision following PRK. Contrast sensitivity function was also preserved except for an increase in 12 cycles per degree (cpd) spatial frequency 6 months after surgery (P = 0.04). Total HOAs and primary spherical aberrations (total, anterior and posterior surface) increased significantly (P < 0.001), however, primary coma showed no statistically significant change 6 months after surgery compared to baseline values. Induced total HOAs significantly correlated with change in primary vertical coma and total, anterior, and posterior primary spherical aberration. No significant correlation was found between the changes in contrast sensitivity, color vision and HOAs with the amount of preoperative sphere and cylinder.Conclusion: PRK with an aspheric profile in moderate myopia/ myopic astigmatism does not affect color vision and contrast sensitivity at 3, 6 and 18 cpd spatial frequencies. It increases total HOAs and spherical aberration, but not coma. It remains a good option for refractive correction of moderate.Keywords: Color vision, Contrast Sensitivity, Higher order aberrations, Photorefractive keratectomy

Recurrent corneal perforation due to chronic graft versus host disease; a clinicopathologic report

Purpose: To describe a case of chronic graft versus host disease (GVHD) leading to severe dry eye and recurrent corneal perforation in both eyes, its stepwise management and histopathological reports. Case Report: A 22-year-old woman with a history of thalassemia and subsequent high-dose chemotherapy followed by allogeneic bone marrow transplant (BMT) was referred to Farabi Eye Hospital. Despite aggressive medical and surgical intervention, corneal vascularization in her right eye progressed and led to corneal perforation. Cyanoacrylate glue was applied to seal the perforation, however it recurred. Multilayer amniotic membrane transplantation (AMT) was performed to seal the corneal perforation, which was effective for a short period. Subsequently, the corneal perforation recurred and penetrating keratoplasty was performed. After a few months deep vascularization and descemetocele occurred in the fellow left eye and the patient finally underwent therapeutic lamellar keratoplasty. Conclusion: Patients with GVHD are at risk of severe dry eye and subsequent corneal vascularization. Recurrent and recalcitrant corneal perforation resistant to cyanoacrylate glue and multilayer AMT may occur. Proper systemic and ocular management alongside close collaboration with the hematologist is strongly recommended to control the condition

Application of polycaprolactone nanofibers as patch graft in ophthalmology

Purpose: The purpose of the study was to evaluate tissue reaction to polycaprolactone (PCL) nanofiber patches in the cornea, conjunctiva, and anterior chamber (AC) in rabbit eyes and to assess their biocompatibility for use as patch grafts. Methods: Two 100 μ PCL patches were implanted under the conjunctiva and in the corneal stroma of one albino New Zealand rabbit, and pathologic evaluation was done after 3 weeks. In the next step, two PCL patches were implanted; one in the corneal stroma and the other in the AC of two rabbits followed by pathologic evaluation after 3 months. Results: On slit-lamp examination, there was minimum inflammation in all cases. Pathologic examination showed that the contact and probably merging between the host tissue and PCL fibers were achieved with minimal tissue reaction. Conclusion: As a biocompatible material, PCL nanofibers seem to be a promising modality for the repair of different tissue defects including melting, thinning, and perforation. They may also be a suitable material for manufacturing keratoprostheses

Amniotic Membrane Extract Preparation: What is the Best Method?

Purpose: To compare different preparation methods for a suitable amniotic membrane (AM) extract containing a given amount of growth factors. Methods: In this interventional case series, we dissected the AM from eight placentas within 24 hours after delivery, under clean conditions. After washing and mixing, AM extracts (AMEs) were prepared using pulverization and homogenization methods, and different processing and storing conditions. Main outcome measures were the amount of added protease inhibitor (PI), the relative centrifugal force (g), in-process temperature, repeated extraction times, drying percentage, repeated pulverization times, and the effect of filtering with 0.2 μm filters. Extract samples were preserved at different temperature and time parameters, and analyzed for hepatic growth factor (HGF) and total protein using ELISA and calorimetric methods, respectively. Results: The extracted HGF was 20% higher with pulverization as compared to homogenization, and increased by increasing the PI to 5.0 μl/g of dried AM. Repeating centrifugation up to 3 times almost doubled the extracted HGF and protein. Storing the AME at −170° for 6 months caused a 50% drop in the level of HGF and protein. Other studied parameters showed no significant effect on the extracted amount of HGF or total protein. Conclusion: Appropriate extraction methods with an adequate amount of PI increases the level of extractable components from harvested AMs. To achieve the maximal therapeutic effects of AMEs, it is necessary to consider the half-life of its bioactive components