Philip D. Jaycock

Effects of variation in depth and side cut angulations in LASIK and thin-flap LASIK using a femtosecond laser: a biomechanical study.

PURPOSE To study the corneal biomechanical effects of varying LASIK flap depth and side cut angulations and evaluate the relative contribution of the lamellar and side cuts using a femtosecond laser and radial shearing speckle pattern interferometry (RSSPI). METHODS Forty-two organ-cultured human corneas were divided into a control group and three investigative groups, each undergoing different incision types at both 90- and 160-μm depth using a femtosecond laser. In the first group, typical LASIK flaps were created; in the second group, only the bed was cut (delamination); and in the third group, side cuts alone were affected. Corneal strain was measured using RSSPI before and after treatment following an increase in hydrostatic pressure from 15.0 to 15.5 mmHg and again after 1 week of incubation in culture medium. RESULTS The flap group demonstrated a weakening of strength related to the depth of cut, with strain increasing by 9% and 32% at 90 and 160 μm, respectively. Similar changes, 9% and 33%, were observed following execution of side cuts to the same depths. By contrast, strain increase following delamination showed no relationship with depth, increasing by 5% in both instances. When the side cut angle was made more acute, strain decreased with a 2% strain increase being measured after a 90-μm, 150° side cut was created. No significant changes occurred during the period of organ culture. CONCLUSIONS Vertical side cuts through corneal lamellae rather than horizontal delamination incisions contribute to the loss of structural integrity during LASIK flap creation. Angulating side cuts such that the stromal diameter of the flap exceeds its epithelial diameter can decrease this effect.

Outcomes of Same-Sizing versus Oversizing Donor Trephines in Keratoconic Patients Undergoing First Penetrating Keratoplasty

PURPOSE To investigate whether use of same-size donor and recipient trephines reduced myopia after penetrating keratoplasty for keratoconus. DESIGN Retrospective cohort study. PARTICIPANTS Eight hundred seventy-eight first grafts for keratoconus were reported to UK Transplant between April 1999 and December 2003. There were 234 and 644 grafts in the same-size and oversize donor trephine groups, respectively. At 1 year, mean spherical equivalent (SE) data were available for 116 eyes (50%) and 295 eyes (46%) in the same-size and oversize groups. At 2 years, mean SE data were available for 64 eyes (27%) and 148 eyes (23%) in the same-size and oversize groups. METHODS Logistic regression and univariate analysis of follow-up data submitted to UK Transplant. MAIN OUTCOME MEASURES At 1 and 2 years postoperatively, mean SE, magnitude of the cylindrical component of the refraction, postoperative uncorrected visual acuity (VA), postoperative best-corrected VA, and postoperative complications were recorded. RESULTS The mean SEs for the same-size and oversize donor trephine groups, respectively, were -1.45 diopters (D) and -1.41 D at 1 year (P = 0.6) and -1.74 D and -2.19 D at 2 years postoperatively (P = 0.3). Although there were no differences in graft survival between the groups at 1 and 2 years, there was a higher incidence of postoperative wound leaks in the same-size group (P = 0.03). CONCLUSION Use of same-size donor and recipient trephines did not reduce myopia and was associated with an increased risk of postoperative complications.

Long term topical steroid treatment after penetrating keratoplasty in patients with pseudophakic bullous keratopathy

PURPOSE To assess the use of long-term topical corticosteroid treatment in patients with pseudophakic bullous keratopathy (PBK) after penetrating keratoplasty (PK). DESIGN Retrospective cohort study. PARTICIPANTS This study considered patients with PBK undergoing an initial PK procedure for visual reasons in the United Kingdom between April 1999 and March 2004. There were 1274 initial PK procedures for PBK reported to United Kingdom Transplant in this period, of which 1184 (91%) were grafted for visual reasons. Of these 1184 grafts, follow-up was reported in 1033 instances (87%). METHODS A Cox regression model was used to investigate the combined effects of all preoperative factors (recipient age, human leukocyte antigen [HLA] matching, trephine size, deep stromal vascularization, surgeon activity) on graft failure. The model was fitted using all preoperative factors first, and subsequently, factors associated with corticosteroid and other medications were included. MAIN OUTCOME MEASURES Graft survival. RESULTS Three-year survival of grafts for PBK was 65% (95% confidence interval [CI], 59%-70%). Topical corticosteroids were still being used beyond 18 months after surgery in 378 (37%) of the 1033 corneal grafts included in this study. The grafts of patients not currently receiving steroids were 1.5 times as likely to fail (hazard ratio [HR], 1.5; 95% CI, 1.0-2.2; P<0.03). Lack of HLA matching (P = 0.006), trephine size <or=7.50 mm and >or=8.00 mm (P = 0.03), recipient age younger than 65 years (P = 0.003), and corneal vascularization (P = 0.04) all increased the risk of graft failure. CONCLUSIONS The use of long-term postoperative corticosteroids improved graft survival after PK for PBK. Barring patient contraindications for long-term topical corticosteroid use, clinicians should consider maintaining patients with PBK on long-term postoperative corticosteroid maintenance.