Relationship of Structural Characteristics to Biomechanical Profile in Normal, Keratoconic, and Crosslinked Eyes.

PURPOSE: To evaluate the correlation of corneal biomechanical parameters with structural characteristics in normal, keratoconic, and collagen crosslinked eyes. METHODS: A prospective observational study that included 50 normal, 100 keratoconic, and 25 crosslinked eyes. All eyes were imaged using a Scheimpflug camera and an ocular response analyzer. The main outcome measures analyzed were central corneal thickness (CCT), corneal volume (CV), maximal keratometry (Kmax), corneal hysteresis (CH), and corneal resistance factor (CRF). RESULTS: Significant differences were noted among all 3 groups of eyes for CCT, CV, Kmax, CH, and CRF values (P < 0.05 by analysis of variance). CH and CRF correlated negatively (CH, r = -0.40; CRF, r = -0.44; both P < 0.0001) with the Pentacam topographic keratoconus classification. Both CH and CRF correlated positively with CCT and CV for the normal, keratoconic, and crosslinked eyes. In contrast, significant negative correlations were observed between CH, CRF, and Kmax in the keratoconic eyes (CH, r = -0.43; CRF, r = -0.53; both P < 0.0001), whereas no association was noted for the normal and crosslinked eyes. CONCLUSIONS: CH and CRF are influenced by the corneal structure, with higher values noted in corneas with greater thickness and volume. Corneal biomechanical parameters progressively decrease as the severity of keratoconus increases. After collagen crosslinking, the relationship of the corneal curvature to the biomechanical profile is similar to normal eyes.

Comparative analysis of corneal measurements obtained from a Scheimpflug camera and an integrated Placido-optical coherence tomography device in normal and keratoconic eyes.

PURPOSE: To assess the agreement between a Scheimpflug camera (Pentacam) and a combined Placido-optical coherence tomography device (Visante OMNI) in measuring corneal curvature, thickness and elevation values in normal and keratoconic eyes. METHODS: Corneal measurements of 110 normal eyes (one eye per subject) and 70 keratoconic eyes were obtained from both devices and compared. Agreement was determined using the Bland-Altman analysis 95% limits of agreement (LoA). RESULTS: The Pentacam measured significantly greater keratometry readings in the flattest (K1) and steepest meridians (K2) in normal and keratoconic eyes. The 95% LoA in normal eyes were -0.32 to 0.59 dioptres (D) (K1) and -0.41 to 0.74 D (K2). In keratoconic eyes, the 95% LoA were -1.35 to 1.92 D (K1) and -1.38 to 1.99 D (K2). The Pentacam recorded significantly higher central corneal thickness (CCT) values in both groups of eyes. The 95% LoA were -4.31 to 39.89 microns (µ) and -12.92 to 41.35 µ in normal and keratoconic eyes, respectively. Pentacam anterior and posterior corneal elevations were significantly greater in both groups of eyes. The devices demonstrated excellent repeatability and reproducibility for corneal curvature and thickness but not elevation measurements. CONCLUSIONS: The Pentacam measured significantly greater corneal curvature, thickness and elevation values compared to the Visante OMNI in normal and keratoconic eyes. The devices agree moderately for anterior corneal elevations in normal eyes and do not appear to be interchangeable for corneal measurements in clinical practice.

Outcome of corneal collagen crosslinking for progressive keratoconus in paediatric patients.

PURPOSE: To evaluate the efficacy of corneal collagen crosslinking for progressive keratoconus in paediatric patients. METHODS: This prospective study included 25 eyes of 18 patients (aged 18 years or younger) who underwent collagen crosslinking performed using riboflavin and ultraviolet-A irradiation (370 nm, 3 mW/cm2, 30 min). RESULTS: The mean patient age was 14.3±2.4 years (range 8-17) and mean followup duration was 20.1±14.25 months (range 6-48). Crosslinked eyes demonstrated a significant reduction of keratometry values. The mean baseline simulated keratometry values were 46.34 dioptres (D) in the flattest meridian and 50.06 D in the steepest meridian. At 20 months after crosslinking, the values were 45.67 D (P=0.03) and 49.34 D (P=0.005), respectively. The best spectacle corrected visual acuity (BSCVA) and topometric astigmatism improved after crosslinking. Mean logarithm of the minimum angle of resolution (logMAR) BSCVA decreased from 0.24 to 0.21 (P=0.89) and topometric astigmatism reduced from mean 3.50 D to 3.25 D (P=0.51). CONCLUSIONS: Collagen crosslinking using riboflavin and ultraviolet-A is an effective treatment option for progressive keratoconus in paediatric patients. Crosslinking stabilises the condition and, thus, reduces the need for corneal grafting in these young patients.

Zig Zag versus Top Hat configuration in IntraLase-enabled penetrating keratoplasty.

AIM: To compare the outcomes with IntraLase-enabled keratoplasty using (IEK) Top Hat (TH) versus Zig Zag (ZZ) configuration. METHODS: Retrospective comparative series of 24 eyes that underwent TH and 10 eyes that underwent ZZ IEK. RESULTS: There were no significant differences in LogMar Best-spectacle corrected visual acuity (TH- IEK=0.3; ZZ-IEK=0.18, p=0.18), spherical equivalent (TH-IEK=-3.55±3.7 dioptres (D); ZZ-IEK=-2.69±4.85 D, p=0.60), manifest cylinder (TH- IEK=3.79±2.43 D; ZZ- IEK=4.61±3.29 D, p=0.45), topographic astigmatism (TH-IEK=3.67±2.34 D; ZZ-IEK=4.26±1.1 D, p=0.63), total higher-order aberrations (TH- IEK=8.26±3.53; ZZ-IEK=8.1±4.71, P=0.92), endothelial cell density change from baseline (TH- IEK= -41.55%±15.86; ZZ-IEK=-25.45%±30.66, p=0.22) or time to suture removal in months (TH- IEK=7.48±4.07; ZZ- IEK=6.93±2.71, p=0.75). There was no difference in requirements for astigmatic keratectomy (TH-IEK=54.2%±13; ZZ-IEK=50%±5, OR=1.18) or complications (TH-IEK=25%±6; ZZ-IEK=30%±3, OR=0.78). CONCLUSIONS: TH-IEK and ZZ-IEK have comparable visual and refractive outcomes, wound healing and endothelial cell counts at 1-year.

Bilateral femtosecond laser-enabled intrastromal astigmatic keratotomy to correct high post-penetrating keratoplasty astigmatism.

A 35-year-old man presented with bilateral high astigmatism following penetrating keratoplasties performed for advanced keratoconus. Femtosecond laser-enabled intrastromal astigmatic keratotomy was performed, resulting in a significant reduction in corneal astigmatism. At 4 months, the corneal astigmatism continued to decrease. The visual acuity, refraction, and serial corneal topographic data are presented.

Keratoconus caused by eye rubbing in patients with Tourette Syndrome.

OBJECTIVE: To report the association between keratoconus and Tourette Syndrome (TS) and to reinforce that eye rubbing may be a causative factor for keratoconus. DESIGN: Observational case series. PARTICIPANTS: Three patients with TS who presented with clinical and topographic findings suggestive of asymmetric or unilateral keratoconus. METHODS: Evaluation of patients in a single clinical practice. RESULTS: Patients' histories revealed asymmetric or unilateral rubbing of the affected eye as a result of a TS tic. Other organic causes associated with keratoconus were absent in these patients. CONCLUSIONS: A possible association between TS and keratoconus exists with chronic eye rubbing being the suggested mechanism. Eye rubbing seems to be an important causative factor for keratoconus.

Deep lamellar endothelial keratoplasty: up to 5-year follow-up.

PURPOSE: To evaluate the outcomes of small-incision deep lamellar endothelial keratoplasty (DLEK) for the treatment of endothelial dysfunction at up to 5 years of follow-up. DESIGN: Prospective, noncomparative case series. PARTICIPANTS: Sixty eyes of 55 consecutive patients who had corneal edema as a result of Fuchs' dystrophy, pseudophakic bullous keratopathy, bullous keratopathy secondary to glaucoma tube placement, failed graft, or deep endothelial scar. METHODS: Patients underwent DLEK surgery at the Toronto Western Hospital. MAIN OUTCOMES MEASURES: Best spectacle-corrected visual acuity (BSCVA), manifest refraction, corneal endothelial cell density (ECD), and postoperative complications. RESULTS: Data were available for 57, 49, 46, 23, and 7 eyes for examination at 1, 2, 3, 4, and 5 years, respectively. The mean spherical equivalent and refractive astigmatism were -0.18+/-1.62 diopters (D) and 1.67+/-1.36 D, respectively, at 1 year after surgery and remained stable at 2, 3, and 4 years after DLEK. Eliminating eyes with known significant macular or optic nerve disease, BSCVA of 20/188.5 before surgery improved to 20/56.9 at 1 year after surgery (P = 0.0002) and remained stable with BSCVA of 20/52.3, 20/46.2, and 20/56.8 at 2, 3, and 4 years, respectively, (P = 0.59, P = 0.31, P = 0.24, respectively). The number of patients who achieved 20/40 or better visual acuity, increased from a preoperative level of 13.5% to 44.1%, to 40%, to 48.4%, and to 50% at 1, 2, 3, and 4 years after surgery, respectively. The mean donor ECD before surgery was 2762+/-536 cells/mm2 and decreased by 43% at 1 year after surgery (1604+/-787 cells/mm2; P<0.0001), an additional yearly decrease by 14% (1257+/- 684 cells/mm2; P = 0.03), by 4% (1136+/-613 cells/mm2; P = 0.41), and by 1% (1064+/-515 cells/mm2; P = 0.68) was found at 2, 3, and 4 years, respectively. Complications included 4 graft dislocations, 2 primary graft failures, 5 rejections, and 12 secondary failures, with 27.5% graft failure at 4 years. CONCLUSIONS: Small-incision DLEK provides good and stable refractive and visual outcomes. The accelerated endothelial cell loss reported during the first 2 years after DLEK was shown to decrease and stabilize at low rates during the longer-term follow-up, which reduces the concern about progressive cell loss and secondary late endothelial failure. FINANCIAL DISCLOSURE(S): The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Intrastromal corneal ring segment SK implantation for moderate to severe keratoconus.

PURPOSE: To report the efficacy and safety of intrastromal corneal ring segment (ICRS) implantation using a femtosecond laser in the management of advanced keratoconus. SETTING: Private laser center, Toronto, Ontario, Canada. METHOD: In this retrospective nonrandomized study, Intacs SK ICRS were implanted using an IntraLase femtosecond laser in eyes with moderate to severe keratoconus. Evaluation included uncorrected (UDVA) and corrected (CDVA) distance visual acuity, manifest refraction, slitlamp examination, corneal topography, and wavefront analysis of higher-order aberrations. Postoperative visits were at 1, 7, and 30 days and 3 and 6 months. RESULTS: The study evaluated 10 eyes of 8 patients with a mean age of 28 years (range 21 to 42 years). The mean UDVA was significantly better 6 months postoperatively than preoperatively (0.66 logMAR +/- 0.21 [SD] versus 1.19 +/- 0.57 logMAR) (P = .004), as was the mean CDVA (0.25 +/- 0.15 logMAR versus 0.51 +/- 0.20 logMAR) (P = .018). The mean spherical equivalent refractive error was -8.08 diopters (D) preoperatively and -5.03 D at 6 months (P = .65); the mean refractive astigmatism, -5.05 D and -3.90 D, respectively (P = .22); and the mean simulated keratometry value, 57.94 D and 50.07 D, respectively (P = .15). The mean total aberration improved significantly, from 13.48 +/- 4.64 mum preoperatively to 9.42 +/- 1.80 mum postoperatively (P = .007). There were no complications. CONCLUSION: Implantation of ICRS for advanced keratoconus was safe and effective, leading to significant improvement in UDVA, CDVA, and total aberrations. FINANCIAL DISCLOSURE: No author has a financial or proprietary interest in any material or method mentioned.

IntraLase-enabled astigmatic keratotomy for post-keratoplasty astigmatism: on-axis vector analysis.

PURPOSE: To determine the refractive predictability, stability, efficacy, and complication rate of femtosecond laser-enabled astigmatic keratotomy for post-keratoplasty astigmatism. DESIGN: A retrospective case series (pilot study). PARTICIPANTS: Thirty-seven eyes of 34 patients. METHODS: All eyes underwent IntraLase-enabled astigmatic keratotomy for high astigmatism (>5 diopters [D]) after penetrating keratoplasty. MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA), best-corrected visual acuity (BCVA), manifest refraction, higher-order aberrations, and complications. RESULTS: Mean follow-up was for 7.2 months. Uncorrected visual acuity improved from a mean of 1.08+/-0.34 logarithm of the minimum angle of resolution preoperatively to a mean of 0.80+/-0.42 postoperatively (P=0.0016). Best-corrected visual acuity improved from a mean of 0.45+/-0.27 preoperatively to 0.37+/-0.27 postoperatively (P=0.018). The defocus equivalent was significantly reduced by more than 1 D (P=0.025). The value of absolute astigmatism was reduced from 7.46+/-2.70 D preoperatively to 4.77+/-3.29 D postoperatively (P=0.0001). Higher-order aberrations were significantly increased. The efficacy index was 0.6+/-0.6. There were no cases of perforation, wound dehiscence, or infectious keratitis. Three eyes (8%) experienced an episode of graft rejection. Overcorrection occurred in 9 eyes (24%). CONCLUSIONS: IntraLase-enabled astigmatic keratotomy is an effective treatment for high astigmatism after penetrating keratoplasty with an encouraging refractive predictability. Future studies may help refine the treatment parameters required to achieve reduction of cylinder with greater accuracy.

Femtosecond laser-assisted mushroom configuration deep anterior lamellar keratoplasty.

PURPOSE: To review patient outcomes after femtosecond laser-assisted mushroom configuration deep anterior lamellar keratoplasty. METHODS: Seven eyes of seven patients with a mean age of 30 years underwent femtosecond laser-assisted mushroom configuration deep anterior lamellar keratoplasty from April 2008 to September 2008. Patients had keratoconus, corneal ectasia or scarring. Set for 100 mum of residual cornea, the femtosecond laser was used to create a mushroom-shaped recipient bed and donor button (having a larger anterior than posterior diameter). The posterior central lamella was manually dissected using Melles technique. RESULTS: Mean follow up was 4 months (range, 3-6.5 months). Preoperative mean best-corrected visual acuity was 20/95 (range, 20/40-20/400). Intraoperative complications included two cases (28.6%) of small Descemet membrane perforation. Postoperatively, there was one case of stromal rejection that resolved with topical steroids and two cases of steroid-related intraocular pressure rise that were treated with a prostaglandin analog. At 3 months, mean best-corrected visual acuity was 20/40 (range, 20/25-20/60), mean spherical equivalent refraction was -3.21 D (range, -6.75 D to plano), mean cylindrical refractive error was 3.57 D (range, 1.5-7 D), and mean keratometric cylinder measured 5.56 D (range, 3.79-7.00 D). Selective suture removal occurred in six patients (86%) at a mean of 3.8 months (range, 2-6 months) postoperatively. CONCLUSIONS: This preliminary series demonstrates that the use of the femtosecond laser to perform corneal cuts in a mushroom configuration for deep anterior lamellar keratoplasty is feasible. The mechanical stability and wound healing advantages for stepped corneal wounds should be considered in lamellar surgery.

Buccal mucous membrane for the reconstruction of complicated leaking trabeculectomy blebs.

PURPOSE: Late onset trabeculectomy bleb leaks often require surgical repair to avoid hypotony and/or infection. Repair using local conjunctiva is typically performed. However, in cases in which local conjunctiva is limited and/or has failed, buccal mucous membrane can be used as a conjunctival substitute. METHODS: Four cases of buccal mucous membrane repair for leaking trabeculectomy blebs are reported. Surgical technique is described. RESULTS: In each case of bleb leak, multiple nonincisional techniques failed to control the leak. In 3 of 4 cases, earlier reconstruction attempts with conjunctival advancement and/or free flaps failed. Each was ultimately repaired with buccal membrane autograft. One case required additional minimally invasive procedures to control postoperative leaking. One case required a second adjacent buccal graft for leaking residual conjunctival bleb. Each graft was functioning well at most recent follow-up ranging from 1 to 17 months. DISCUSSION: Buccal membrane is an abundant and effective conjunctival substitute for the repair of recalcitrant leaking trabeculectomy blebs. It may be useful in cases in which earlier conjunctival-based repairs have failed.

Daytime presentations to a metropolitan ophthalmic emergency department.

BACKGROUND: To determine the diagnoses causing patients to present to a dedicated ophthalmic emergency department. To detect associations with patient demographics. METHODS: A retrospective review of all presentations to the Sydney Eye Hospital Emergency Department between 08:00 and 17:00 hours from 1 January to 31 December 2001 was conducted. Data were analysed for frequency of diagnoses and patient demographics. RESULTS: A total of 10 599 patients presented to the emergency department on 16 870 occasions. On average, 46 patients were seen daily. Men accounted for 57.7% and women for 42.3% of presentations. The five commonest reasons for presentation were conjunctivitis, keratitis, cataract, corneal abrasion and iridocyclitis. CONCLUSIONS: Ocular surface and anterior segment diagnoses are predominant among emergency presentations. Statistically significant associations exist between sex and selected diagnoses, and between age and almost all of the commonest diagnoses. The emergency department functions as a primary care provider with most patients discharged following initial consultation.