Corneal morphometry prior to and five years after corneal stromal photoablation: the possible role of topical anesthesia on postablative corneal morphometry / Morfometría corneal previa a y cinco años tras fotoablación estromal corneal: el posible papel de la anestesia tópica en la morfometría corneal postablativa

The aim of this study was to investigate central corneal thickness values prior to and five years after ablation of the central cornea using 193 nm UV radiation. Thirty eight eyes of 38 subjects were analysed in a prospective study. Central corneal thickness measurements were carried out prior to and 60 months after corneal stromal photoablation under a 160 ?m flap with the Summit Excimed SVS plus excimer laser (Summit Technology, Inc. Walthan, MA). Mean intended ablation depth was 55±20 ?m. Central corneal thickness measurements were carried out with the DGH 2000 AP ultrasonic pachymeter (DGH Technology, Inc., San Diego, USA). Consecutive central corneal thickness readings were made until three consecutive measurements were within 5 mm of each other. The mean of these three consecutive readings was used as the value of central corneal thickness in this study. Preoperative mean central corneal thickness was 556±55 ?m; five years later it was 513.41 ?m (p<0.001). The difference between the "theoretical" postablative corneal thickness values and the "real" corneal thickness values observed 60 months after stromal photoablation was also significant (p<0.001). Five years after central corneal stromal photoablation using 193 nm UV radiation there was a disparity between the programmed postoperative residual corneal thickness and the corneal thickness obtained by ultrasound pachymetry. Further research is neccesary in order to identify possible unexpected values of corneal thickness after a paracentral corneal stromal photoablation has been carried out (AU)

El objetivo de este estudio era investigar los valores del espesor corneal previo a y cinco años tras la ablación de la córnea central empleando radiación UV de 193 nm. Treinta ojos de treinta sujetos fueron analizados en un estudio prospectivo. Las mediciones del espesor corneal se realizaron previo a y 60 meses tras la fotoablación estromal bajo un flap de 160 micras con el láser excimer Summit Excimed SVS plus (Summit Technology, Inc. Walthan, MA). La media de la ablación intentada fue de 55ñ20 micras. Las mediciones del espesor corneal central se realizaron con el paquímetro ultrasónico DGH 2000 AP (DGH Technology, Inc. San Diego, USA). Se realizaron mediciones consecutivas del espesor corneal hasta que tres consecutivas de ellas estuviesen entre 5 micras de diferencia. La media de estas tres mediciones consecutivas se usó como el valor del espesor central en este estudio. El espesor central medio era 565ñ55 micras; cinco años después era 513ñ41 micras (p<0.001). La diferencia entre los teóricos valores del espesor corneal y los verdaderos observados 60 meses tras la ablación estromal también fue significativa (p<0.001).Cinco años tras la fotoablación estromal empleando radiación UV de 193 nm existe una disparidad entre el espesor residual postoperativo programado y el espesor corneal obtenido mediante paquimetría ultrasónica. Es necesaria mayor investigación con la finalidad de identificar los posibles valores inesperados del espesor corneal tras ser realizada una ablación estromal paracentral (AU)

pH, ionized calcium and osmotic artifacts can affect determination of rabbit corneal deturgescence in vitro.

Freshly isolated stroma-endothelial preparations were perfused with a glucose, adenosine and glutathione-supplemented Ringer solution at 37 degrees C at a hydrostatic pressure of 20 cm H2O. The composition (tCO2, pH, Ca2+ and osmolality) of the stromal-side bathing solution was analyzed during a 90-min equilibration period during which this solution was covered or deliberately left open to the atmosphere. If exposed to the atmosphere, even for a few minutes, substantial changes in pH, osmolality and ionized calcium occurred such that, when silicone oil was subsequently applied to the stromal surface, significant increases in both the rate and amplitude of deturgescence were observed. The rates and amplitude were proportional to the corneal thickness prior to silicone oil application. The results further indicate that the physicochemical state of the stroma is an important determinant in the corneal deturgescence mechanism.