Accurate calibration of ablation rate by excimer laser prerequisite for precise photorefractive keratectomy (PRK). When a polymethylmethacrylate (PMMA) plate is ablated by excimer laser, debris is generated, which may affect homogeneity of the laser beam and energy density, and change the ablation rate. In order to clarify the effects of the debris on the ablation rate, we studied the changes in the ablation rate when the debris was removed by blowing or aspirating over the ablation area during PRK.PMMA plates were ablated using a scanning excimer laser system (EC-5000, NIDEK, Japan) in PRK mode under the following conditions: (1) with air blowing over the ablation area, (2) with aspiration of the debris, and (3) without treatment. The ablation rates were determined by measuring the refractive power of PMMA plates with a lens meter. The ablated surface was observed by scanning electron microscope (SEM). The ablation rate with blowing was the highest among the three conditions, that with aspiration was the second, and that without treatment was the lowest. The ablation rates with blowing showed no significant change when the ablation rates were changed. However, the ablation rates with aspiration or without treatment decreased as the pulse rate increased. The surface ablated during blowing was the smoothest in SEM photographs. We concluded that calibration of the ablation rate using PMMA plates must be done with appropriate air blowing.
We describe a new membrane filter (PORETEC) technique for processing cytopathologic fluid specimens. This procedure provides excellent cytologic preparations because there is no background staining and only a small amount of fluid specimen is necessary, as there is little cell loss. We compared the number of cells collected by the membrane filter technique with that collected by cytocentrifugation using conjunctival brush cytology specimens from 6 subjects. The number of cells obtained by the new method was significantly higher than that obtained by the cytocentrifugation technique. This method was very useful for ocular fluid specimens such as aqueous humor, vitreous specimens, and scrapings from the cornea and conjunctiva. We showed some examples of these specimens including immunocytochemical staining done by this method. We confirm that this is valuable for diagnostic cytopathologic study of various fluid specimens in ophthalmology.
