RESUMEN
BACKGROUND AND OBJECTIVE: To determine the corneal flap thickness produced by using two different types of blades on the same microkeratome for LASIK, comparing flap thickness in the first and second eyes. PATIENTS AND METHODS: The corneal flap thickness was measured in two sets of 100 consecutive patients undergoing bilateral LASIK procedures using the Moria M2 microkeratome with a 110 head (Moria, France) and either Moria or CLB blades (Med-Logics Inc., Laguna Hills, CA). Corneal flap thickness was determined by intraoperative pachymetry using an ultrasonic pachymeter. RESULTS: The mean corneal flap thickness was 138.95 +/- 21.6 microm (range: 75-205 microm) with Moria blades and 115.07 +/- 16.0 microm (range: 70-153 microm) with CLB blades, which is a significant difference (P < .001). The difference in flap thickness between the first and second eyes was not significant with the Moria blades (141.46 +/- 21.46 microm vs 136.45 +/- 21.55 microm, P = .965), but it was when the CLB blades were used (123.21 +/- 12.07 microm vs 106.93 +/- 15.51 microm; P= .013). CONCLUSION: In LASIK surgery using a Moria M2 microkeratome, blades from different manufacturers may produce significantly different corneal flap thicknesses, as well as differences between the first and second eyes.
Asunto(s)
Astigmatismo/cirugía , Sustancia Propia/patología , Queratomileusis por Láser In Situ/instrumentación , Láseres de Excímeros/uso terapéutico , Miopía/cirugía , Colgajos Quirúrgicos/patología , Adulto , Pesos y Medidas Corporales , Sustancia Propia/diagnóstico por imagen , Femenino , Humanos , Masculino , Persona de Mediana Edad , Estudios Retrospectivos , Ultrasonografía , Agudeza VisualRESUMEN
BACKGROUND AND OBJECTIVE: To investigate inaccuracy and variability in residual stromal thickness estimation in LASIK by pachymetry and measurements of corneal thickness, flap thickness, and ablation depth. PATIENTS AND METHODS: In 73 eyes of 37 patients, preoperative and postoperative corneal thicknesses were obtained with slit-scanning elevation topography and the ultrasound pachymeter. LASIK was performed and corneal flaps were created with a microkeratome. Flap thickness and ablation depth (expected and achieved) were calculated. Residual stromal thickness estimation error was analyzed. RESULTS: The mean preoperative corneal thicknesses were 559.58 +/- 23.47 and 554.92 +/- 29.95 microm for the ultrasound pachymeter and slit-scanning elevation topography, respectively. Measurement differences ranged from -36 to 30 microm. With the pachymeter, calculated mean flap thickness was 139.58 +/- 17.59 microm. With this device, predicted ablation depth differed from achieved depth by 20% or more in approximately one-third (30.14%) of treated patients; ablation differences ranged from 10.0% to 19.99% in 37% of patients and 1.00% to 9.99% in 31.5% of patients. CONCLUSION: Imprecision of microkeratome cuts, preoperative corneal pachymetry, and laser ablation depth have a significant impact on the inaccuracy of residual stromal thickness prediction. Especially in patients with borderline corneal thickness, intraoperative pachymetry measurements and a residual stromal thickness higher than the safety margin of 250 microm are recommended to minimize iatrogenic ectasia.
Asunto(s)
Sustancia Propia/patología , Queratomileusis por Láser In Situ/métodos , Miopía/cirugía , Colgajos Quirúrgicos/patología , Adulto , Pesos y Medidas Corporales , Sustancia Propia/diagnóstico por imagen , Femenino , Humanos , Masculino , Microscopía Acústica , Persona de Mediana Edad , Estudios Prospectivos , Reproducibilidad de los ResultadosRESUMEN
PURPOSE: To describe a series of cases (Elevated Intraocular Pressure Induced Interlamellar Stromal Keratitis (PISK)) that appears to be identical to post-laser in situ keratomileusis (LASIK) diffuse lamellar keratitis (DLK), but was present at a later time frame and was associated with a significant elevation of intraocular pressure (IOP). Unlike DLK, this syndrome is not steroid responsive, but resolves with a lowering of the IOP. DESIGN: Retrospective, noncomparative, small case series. PARTICIPANTS: The medical records of four LASIK patients with IOP-induced interface changes for the 1-year period March 2000 to March 2001 were reviewed retrospectively. MAIN OUTCOME MEASURE: Slit-lamp appearance. RESULTS: In the four cases presented, the slit-lamp findings and visual degradation appeared identical to DLK. All cases, however, presented outside of the first postoperative week and were not associated with any antecedent trauma. All four cases failed to respond to high-dose topical steroids. Significant IOP elevations were noted in all cases, and the interface changes responded dramatically to both a lowering of the IOP and a discontinuation or lowering of the topical steroids. CONCLUSIONS: Elevated IOP-induced post-LASIK interface keratitis (PISK) is a poorly documented phenomena. Because the condition may be caused by or worsened by frequent topical steroids, early recognition is important. Treatment consists primarily of normalizing the IOP.