PURPOSE: The purpose of this study was to use the Arizona Eye Model to help guide customization of corneal excimer ablation and reduce spherical aberration. METHODS: Myopic eyes were treated with the Nidek EC-5000 excimer laser with a 5.5-mm diameter optic ablation zone and a 7.0-mm diameter transition ablation zone. We analyzed preoperative and postoperative corneal topographies using height mapping. From this data, refractive error profiles and maps were constructed using the Arizona Eye Model. The first group of patients had refractions between -2.00 and -5.00 D. Data was obtained by subtracting postoperative topography from preoperative topography. We then plotted the ideal ablation pattern if no additional spherical aberration was introduced when compared to preoperative topographies. RESULTS: We found that in the central 4 mm, the ablation pattern was highly acceptable, with negligible spherical aberration. As the ablation moved out toward 6 mm, there was increasing spherical aberration. Newer ablation designs require more flattening in the midperiphery of the cornea. These flatter peripheral designs require more blending in the periphery and larger transition zones. CONCLUSION: The use of computerized corneal topography in eye modeling is helpful in designing new ablation patterns to reduce optical and spherical aberration. Ablation zone design is critical to maximizing optical and biologic tolerance.

Astigmatism↗

PubMedDate not supplied

Practical ophthalmic microbiology.

Infection is commonly encountered in everyday ophthalmic practice. It is of great importance that all ophthalmic personnel are familiar with the basic etiologies of these infections, and the basic techniques which are used in diagnosis. When evaluating a patient with possible infection, it is often of great help to be familiar with the normal microbial flora of the human body. This normal flora has been detailed in the article. The assumption is that knowledge of a patient's flora can help guide decisions about the possible etiologies of an infection. When presented with an obvious ocular infection, health care personnel should review the "usual suspects"--that is, the common etiologies for each type of infection. The key to combating ocular infections lies in accurate treatment of the presumed infectious agent. Therefore, the techniques and steps used in the identification of the etiology of an infection should be known to all ophthalmic personnel. The proper sterile techniques of obtaining a specimen from a suspected corneal ulcer or conjunctivitis and the plating of the specimen on specific agar for identification are essential to everyday practice (Figure 8). Patients who will undergo surgery, regardless of the type, are being placed at a special risk for infection. These post-operative infections can destroy the work of the most careful and exact surgical technique. It is an essential part of the procedure that the patient be protected as best they can from subsequent infection. The techniques to reduce the risk of post-operative infection have been detailed above. Proper preparation of a sterile field, sterile draping, and perioperative antibiotics can reduce the chance of a subsequent infection. It is important that these basic steps of care be properly provided to help insure successful surgical outcomes and excellence in health care.

Eye Infections, Bacterial↗