Femtosecond dovetail penetrating keratoplasty: surgical technique and case report.

AIM: To report a dovetail configuration for femtosecond-enabled penetrating keratoplasty (PK) with the corresponding laser parameters and suturing technique. METHODS: A 40-year-old man, with a history of penetrating corneal injury as a child, underwent femtosecond-enabled dovetail keratoplasty, anterior vitrectomy and secondary intraocular lens suturing to repair his corneal scar and aphakia. A partial thickness dovetail pattern was performed in the recipient cornea using the femotsecond laser. The posterior side-cut was initiated approximately 100 microm anterior to the Descemet membrane and extended obliquely towards the outer edge of a ring lamellar cut, positioned at approximately 300 microm stromal depth. The anterior side-cut was extended from the internal edge of the ring lamellar cut to the corneal surface. Using an artificial chamber, the femtosecond laser was used to create a full-thickness 0.2 mm oversized femtosecond-enabled dovetail trephination with similar anterior lamellar depth (approximately 300 microm). Wound closure, using interrupted 10-0 nylon sutures, was guided by preplaced radial alignment laser microincisions and tongue-in-groove midstromal suture positioning. RESULTS AND DISCUSSION: Excellent alignment and stability of the donor and recipient tissue were observed immediately postoperatively and 5 months after surgery. The feasibility of the "dovetail" pattern of PK and the tongue-in-groove suture positioning is demonstrated.

Impediments to eye transplantation: ocular viability following optic-nerve transection or enucleation.

Maintenance of ocular viability is one of the major impediments to successful whole-eye transplantation. This review provides a comprehensive understanding of the current literature to help guide future studies in order to overcome this hurdle. A systematic multistage review of published literature was performed. Three specific questions were addressed: (1) Is recovery of visual function following eye transplantation greater in cold-blooded vertebrates when compared with mammals? (2) Is outer retina function following enucleation and reperfusion improved compared with enucleation alone? (3) Following optic-nerve transection, is there a correlation between retinal ganglion cell (RGC) survival and either time after transection or proximity of the transection to the globe? In a majority of the studies performed in the literature, recovery of visual function can occur after whole-eye transplantation in cold-blooded vertebrates. Following enucleation (and reperfusion), outer retinal function is maintained from 4 to 9 h. RGC survival following optic-nerve transection is inversely related to both the time since transection and the proximity of transection to the globe. Lastly, neurotrophins can increase RGC survival following optic-nerve transection. This review of the literature suggests that the use of a donor eye is feasible for whole-eye transplantation.

[Ablation on the undersurface of a LASIK flap. Instrument and method for continuous eye tracking]. / Ablation auf der Unterseite eines LASIK-Flaps. Neues Instrument und Verfahren zum kontinuierlichen Eye-Tracking.

BACKGROUND: The risk of iatrogenic keratectasia after laser in situ keratomileusis (LASIK) increases with thinner posterior stromal beds. Ablations on the undersurface of a LASIK flap could only be performed without the guidance of an eye tracker, which may lead to decentration. A new method for laser ablation with flying spot lasers on the undersurface of a LASIK flap was developed that enables the use of an active eye tracker by utilizing a novel instrument. The first clinical results are reported. PATIENTS AND METHODS: Patients wishing an enhancement procedure were eligible for a modified repeat LASIK procedure if the flaps cut in the initial procedure were thick enough to perform the intended additional ablation on the undersurface leaving at least 90 microm of flap thickness behind. (1) The horizontal axis and the center of the entrance pupil were marked on the epithelial side of the flap using gentian violet dye. (2) The flap was reflected on a newly designed flap holder which had a donut-shaped black marking. (3) The eye tracker was centered on the mark visible in transparency on the flap. (4) Ablation with a flying spot Bausch & Lomb Technolas 217z laser was performed on the undersurface of the flap with a superior hinge taking into account that in astigmatic ablations the cylinder axis had to be mirrored according to the formula: axis on the undersurface=180 degrees -axis on the stromal bed. (5) The flap was repositioned. RESULTS: Detection of the marking on the modified flap holder and continuous tracking instead of the real pupil was possible in all of the 12 eyes treated with this technique. It may be necessary to cover the real pupil during ablation in order not to confuse the eye tracker. Ablation could be performed without decentration or loss of best spectacle-corrected visual acuity. Refractive results in minor corrections were good without nomogram adjustment. CONCLUSIONS: Using this novel flap holder with a marking that is tracked instead of the real pupil, centered ablations with a flying spot laser on the undersurface of a LASIK flap are feasible. Thus, the additional risk of iatrogenic keratectasia associated with stromal enhancement ablations is avoided.

[LASEK: results after 1 year. Retrospective analysis based on the dioptric power matrix for moderate myopic and astigmatic correction]. / Einjahresergebnisse nach LASEK. Retrospektive Analyse mit Hilfe der Refraktionsmatrix bei der Korrektur von mittlerer Myopie und myopem Astigmatismus.

PURPOSE: The aim of this study was to assess astigmatism magnitude and axis changes based on the dioptric power matrix in low to moderate levels of myopia and astigmatism treated with LASEK. PATIENTS AND METHODS: This retrospective analysis included 54 myopic eyes treated with LASEK with a minimum follow-up of 12 months. An epithelial flap was created by 25-45 s of 20% alcohol exposure. The corneal surface was ablated using two different excimer lasers and nomogram adjustment. The flap was repositioned and a bandage applied to the contact lens. Main outcome measures were manifest refraction as calculated with the dioptric power matrix, UCVA, BSVCA, and retreatment rate. RESULTS: Mean manifest refraction is shown in table 2 (Tabelle 2). UCVAs of 20/20 or better were found in 33% of eyes at 1 week and in more than 53% at 3 months to 1 year. The safety index remained > or =0.98 after postoperative week 4. The efficacy index varied between 0.91 and 0.98 after 1 month. CONCLUSION: LASEK for correction of low to moderate myopia and astigmatism seems to be a safe, effective, and stable option.

Diffuse lamellar keratitis: incidence, associations, outcomes, and a new classification system.

PURPOSE: To evaluate the incidence, associations, and visual outcomes in patients with diffuse lamellar keratitis (DLK) after laser in situ keratomileusis (LASIK). SETTING: University-based refractive surgery center, Boston, Massachusetts, USA. METHODS: This retrospective review comprised 2711 eyes that had LASIK between September 1996 and September 1999. All eyes that developed DLK after LASIK were included. They were divided into type I DLK (center sparing) or type II DLK (center involved) and then subdivided into A (sporadic-DLK not diagnosed in other patients treated on the same day) or B (cluster-other patients identified with DLK). Type IA corresponded to center sparing, sporadic; type IB, center sparing, cluster; type IIA, center involved, sporadic; and type IIB, center involved, cluster. The main outcome measures were incidence of DLK after LASIK, time to diagnosis, time to resolution, and changes in best spectacle-corrected visual acuity (BSCVA). Unpaired t tests were used for statistical analyses. RESULTS: Thirty-six eyes (1.3%) developed DLK. Type I occurred in 58.3% of cases (type IA, n = 18; type IB, n = 3) and type II, in 41.7% (type IIA, n = 10; type IIB, n = 5). The mean time to diagnosis was not statistically significantly different between type I (1.8 days) and type II (1.1 days). Fourteen eyes (38.9%) developed DLK after an epithelial defect, representing an odds ratio of 13 times. The association with an epithelial defect was statistically significantly greater with type I (11/21 eyes, 52.4%) than with type II (3/15 eyes, 20.0%; P =.05). The mean time to resolution was 3.5 days in type I (type IA = 3.6 days; type IB = 2.7 days). This was significantly shorter than in type II, which had a mean time to resolution of 12.1 days (type IIA = 9.3 days; type IIB = 10.2 days) (P =.001). Loss of 2 or more lines of BSCVA occurred in 2 of 5 patients with type IIB and in no patients with types IA, IB, or IIA. CONCLUSIONS: Epithelial defects after LASIK increased the risk of DLK occurrence, especially type I. Type II DLK was associated with a prolonged time to resolution and carried a significantly higher risk of BSCVA loss than type I.

Diminished corneal angiogenesis in gelatinase A-deficient mice.

The goal of the present study was to define the role of gelatinase A in angiogenesis. We performed corneal micropocket assays in gelatinase A-deficient mice and their age-matched wild-type littermates. The corneal neovascular area in gelatinase A-deficient mice (0.15+/-0.14 mm(2)) was significantly less than that of wild-type littermates (0.53+/-0.35 mm(2); P<0.01). Similarly, aortic ring assays showed significant reduction of endothelial outgrowth in gelatinase A-deficient mice (0.26+/-0.14 mm(2)) as compared to wild-type littermates (0.44+/-0.06 mm(2); P<0.05). These results suggest that gelatinase A may play an important role in the regulation of corneal angiogenesis.

Matrilysin cleavage of corneal collagen type XVIII NC1 domain and generation of a 28-kDa fragment.

PURPOSE: To localize endostatin and collagen type XVIII in human corneas and to characterize the enzymatic action of matrix metalloproteinases (MMPs) in the cleavage of collagen type XVIII and generation of endostatin in the cornea. METHODS: Anti-endostatin and anti-hinge antibodies were generated using peptide fragments corresponding to the endostatin region and the adjacent nonendostatin hinge region of collagen XVIII noncollagenous (NC)1 domain, respectively. Confocal immunostaining was performed to localize collagen XVIII in human corneas. SV40-immortalized corneal epithelial cells were immunoprecipitated and incubated with active MMP-1, -2, -3, -7, or -9, and Western blot analysis was performed to study collagen XVIII cleavage. Incubation with MMP-7 was performed at various concentrations (0, 2, 4, and 6 microg/ml) and time intervals (0, 1, 5, and 12 hours). Purified recombinant NC1 fragment of collagen XVIII was also digested with MMP-7, and the cleavage product was sequenced. RESULTS: Collagen XVIII was immunolocalized to the human corneal epithelium, epithelial basement membrane, and Descemet membrane. Western blot analysis demonstrated a 180- to 200-kDa band corresponding to collagen XVIII. MMP-7 (but not MMP-1, -2, -3, and -9) cleaved corneal epithelium-derived collagen XVIII to generate a 28-kDa endostatin-spanning fragment in a time- and concentration-dependent fashion. MMP-7 cleaved purified recombinant 34-kDa NC1 fragment of collagen XVIII in the hinge region to generate a 28-kDa fragment. CONCLUSIONS: Collagen XVIII is present in human cornea. MMP-7 cleaves the collagen XVIII NC1 domain to generate a 28-kDa fragment in the cornea.

LASIK complications: etiology, management, and prevention.

Laser in situ keratomileusis (LASIK) is a rapidly evolving ophthalmic surgical procedure. Several anatomic and refractive complications have been identified. Anatomic complications include corneal flap abnormalities, epithelial ingrowth, and corneal ectasia. Refractive complications include unexpected refractive outcomes, irregular astigmatism, decentration, visual aberrations, and loss of vision. Infectious keratitis, dry eyes, and diffuse lamellar keratitis may also occur following LASIK. By examining the etiology, management, and prevention of these complications, the refractive surgeon may be able to improve visual outcomes and prevent vision-threatening problems. Reporting outcomes and mishaps of LASIK surgery will help refine our approach to the management of emerging complications.

Corneal neovascularization.

Corneal neovascularization (NV) is a sight-threatening condition usually associated with inflammatory or infectious disorders of the ocular surface. It has been shown in the field of cancer angiogenesis research that a balance exists between angiogenic factors (such as fibroblast growth factor and vascular endothelial growth factor) and anti-angiogenic molecules (such as angiostatin, endostatin, or pigment epithelium derived factor) in the cornea. Several inflammatory, infectious, degenerative, and traumatic disorders are associated with corneal NV, in which the balance is tilted towards angiogenesis. The pathogenesis of corneal NV may be influenced by matrix metalloproteinases and other proteolytic enzymes. New medical and surgical treatments, including angiostatic steroids, nonsteroidal inflammatory agents, argon laser photocoagulation, and photodynamic therapy have been effective in animal models to inhibit corneal NV and transiently restore corneal "angiogenic privilege."

New lamellar keratoplasty techniques: posterior keratoplasty and deep lamellar keratoplasty.

Posterior keratoplasty is a new surgical technique that may be valuable in treating patients with corneal decompensation secondary to endothelial dysfunction. There are currently two approaches to posterior keratoplasty. In the first approach, a corneal flap is created using a microkeratome (similar to laser in situ keratomileusis flap), and posterior stromal tissue is excised (by trephination or excimer laser keratectomy). In the second approach, a deep stromal pocket is created across the cornea through a superior scleral incision. A custom-made flat trephine is inserted into the pocket to excise a posterior lamellar disc. Preliminary studies have shown the feasibility of performing these techniques in sighted human eyes. Despite potential advantages, further clinical studies are needed to determine whether these techniques reduce interface scarring, astigmatism and graft rejection, improve visual outcomes, or are potentially an alternative for penetrating keratoplasty.

Surgically induced topographical abnormalities after LASIK: management of central islands, corneal ectasia, decentration, and irregular astigmatism.

Proper preoperative evaluation is critical for avoiding many postoperative complications associated with laser in-situ keratomileusis (LASIK). Proper nonsurgical management includes careful monitoring of patients during the recovery period using various testing procedures, including corneal topography. When surgical intervention is required, a stepwise approach often is used as a conservative treatment, allowing further treatment if necessary. Many complications after LASIK are amenable to further treatment. However, it often is advisable to monitor patients until improved instrumentation is developed. The authors review the etiology and management of several complications after LASIK by reviewing the literature and relaying their own clinical experiences.

Laser subepithelial keratomileusis: electron microscopy and visual outcomes of flap photorefractive keratectomy.

Laser epithelial keratomileusis (LASEK) is a surgical technique that may be performed in patients with low myopia who are considering conventional photorefractive keratectomy (PRK), in patients with thin corneas, and in patients with professions or lifestyles that predispose them to trauma. Ethanol (18%) is applied for 25 seconds and a hinged epithelial flap is created. After laser ablation, the flap is repositioned over the ablated stroma. Our data showed that epithelial defects occurred in 63% eyes on Day 1. Postoperative pain was absent in 47%. Uncorrected visual acuity of 20/40 or better was achieved in all patients at 1 week. Data from several studies suggest that LASEK may reduce postoperative pain and corneal haze associated with PRK. LASEK offers the potential advantage of avoiding flap-related complications associated with laser in situ keratomileusis and decreasing postoperative pain and corneal scarring associated with PRK. Long-term studies are needed to confirm these potential advantages and to determine the safety, efficacy, and predictability of this surgical technique.

Posterior corneal surface changes after refractive surgery.

OBJECTIVE: To determine the frequency of changes in posterior corneal surface after laser in situ keratomileusis (LASIK) and photorefractive keratectomy (PRK). DESIGN: Nonrandomized, comparative trial. PARTICIPANTS: Ninety-five eyes (71 patients) that underwent PRK (n = 45) or LASIK (n = 50). CONTROLS: Twenty nonsurgery eyes were used to validate the method of analysis of the posterior corneal curvature (PCC). Seventy nonsurgery eyes were used for comparisons. METHODS: Float, apex-fixed best fit corneal curvature (ABC), and posterior elevation difference were evaluated in 20 elevation topography maps at 6 zone diameters (3-7 and 10 mm) and at two time points. Corneal elevation maps before and after PRK or LASIK were analyzed by the ABC and float methods and compared with a nonsurgery group. MAIN OUTCOME MEASURES: Posterior corneal curvature change (mm) was classified as flattening, steepening, or no change. RESULTS: Flattening of more than 0.12 mm was found in 22.2% of eyes (n = 10) in the PRK group, a change of +/-0.12 mm was found in 53.3% of eyes (n = 24), and steepening of more than 0.12 mm was found in 24.4% of eyes (n = 11) using the float method and in 28.9% of eyes (n = 13), 35.6% of eyes (n = 16), and 35.6% eyes (n = 16), respectively, using the ABC method. In the LASIK group, the float method registered flattening in 20% of eyes (n = 10), no change in 52% of eyes (n = 26), and steepening in 28% of eyes (n = 14), whereas the ABC method registered flattening in 30% of eyes (n = 15), no change in 40% of eyes (n = 20), and steepening in 30% of eyes (n = 15). The nonsurgery group showed a similar change in PCC at two different time points similar to that of the PRK and the LASIK groups. CONCLUSIONS: The differences observed in the PCC after PRK or LASIK were not statistically significantly different from those observed over time in the nonsurgery control group.

Monovision outcomes in presbyopic individuals after refractive surgery.

PURPOSE: To characterize monovision outcomes and patient satisfaction with conventional monovision (dominant eye corrected for distance) and crossed monovision (dominant eye corrected for near) in presbyopic individuals after excimer laser photorefractive keratectomy (PRK) and laser in situ keratomileusis (LASIK). DESIGN: Retrospective observational case series. PARTICIPANTS: One hundred forty-four consecutive patients, 45 years or older, who were treated with excimer laser refractive surgery between December 1995 and June 1998. METHODS: Patients in whom the surgical outcome was monovision (MV) (distance vision spherical equivalent [SE] -0.50 to +0.50 diopter (D), near vision SE -3.75 to -1.00 D and anisometropia 1.00 D or greater), crossed MV (dominant eye corrected for near vision and the nondominant eye for distance vision) and full correction (bilateral SE -0.50 to +0.50) were identified. Data were abstracted and analyzed statistically. MAIN OUTCOME MEASURES: Preoperative and postoperative visual acuity and refraction. Patient satisfaction with monovision RESULTS: Forty-two patients had surgical outcome of MV. In MV patients, the average distance vision SE, near vision SE, and anisometropia were -0.04 +/- 0.27 D, -1.95 +/- 0.70 D, and 1.92 +/- 0.74 D, respectively. Patient satisfaction was 88% with MV. Twelve patients attained crossed MV. All patients with crossed MV were satisfied with their vision. Patient satisfaction with MV showed no relationship to gender, age at initial surgery, preoperative trial of monovision, laterality of treatment, type of monovision, or predictability of outcomes. CONCLUSIONS: Monovision may be a valuable option for presbyopic individuals considering refractive surgery. Crossed monovision can result in satisfactory visual outcomes.

Determination of corneal asphericity after myopia surgery with the excimer laser: a mathematical model.

PURPOSE: To determine the theoretical change of corneal asphericity within the zone of laser ablation after a conventional myopia treatment, which conforms to Munnerlyn's paraxial formula and in which the initial corneal asphericity is not taken into consideration. METHODS: The preoperative corneal shape in cross section was modeled as a conic section of apical radius R(1) and shape factor p(1). A myopia treatment was simulated, and the equation of the postoperative corneal section within the optical zone was calculated by subtracting the ablation profile conforming to a general equation published by Munnerlyn et al. The apical radius of curvature r(2) of the postoperative profile was calculated analytically. The postoperative corneal shape was fitted by a conic section, with an apical radius equal to r(2) and a shape factor p(2) equal to the value that induced the lowest sum of horizontal residuals and the lowest sum of squared residuals. These calculations were repeated for a range of different dioptric treatments, initial shape factor values, and radii of curvature to determine the change of corneal asphericity within the optical zone of treatment. RESULTS: Analytical calculation of r(2) showed it to be independent of the initial preoperative shape factor p(1). The determination of p(2) was unambiguous, because the same value induced both the lowest sum of residuals and the lowest sum of the squared residuals. For corneas initially prolate (p(1) < 1), prolateness increased (p(2) < p(1) < 1), whereas for oblate corneas (p(1) > 1), oblateness increased (p(2) > p(1) > 1) within the treated zone after myopia treatment. This trend increased with the increasing magnitude of treatment and decreased with increasing initial apical radius of curvature R(1). CONCLUSIONS: After conventional myopic excimer laser treatment conforming to Munnerlyn's paraxial formula, the postoperative theoretical corneal asphericity can be accurately approximated by a best-fit conic section. For initially prolate corneas, there is a discrepancy between the clinically reported topographic trend to oblateness after excimer laser surgery for myopia and the results of these theoretical calculations.

Amniotic membrane inlay and overlay grafting for corneal epithelial defects and stromal ulcers.

OBJECTIVES: To determine the effect of amniotic membrane transplantation (AMT) on persistent corneal epithelial defects (PEDs) and to compare the efficacy between inlay and overlay techniques. METHODS: Thirty patients (30 eyes) underwent AMT for PED. The use of AMT was restricted to patients in whom all previous measures, including bandage contact lens and tarsorrhaphy, had failed. The amniotic membrane was placed on the surface of the cornea in overlay (group A) or inlay (group B) fashion. RESULTS: The PED healed after the first AMT in 21 eyes (70%) within an average of 25.5 days after surgery and recurred in 6 eyes (29%). Among the 22 eyes treated with an overlay AMT (group A), the PED healed after the first AMT in 14 eyes (64%) within an average of 24.5 days and recurred in 4 eyes (29%). Among the 8 eyes treated with an inlay AMT (group B), the PED healed within an average of 27.4 days after AMT, which did not statistically significantly differ from group A (P = .72). The PED healed after the first AMT in 7 eyes (88%) and recurred in 2 (29%) of 7 eyes. CONCLUSIONS: The AMT can be helpful in the treatment of PED in which all other conventional management has failed. However, the success rate in our study was not as high as that previously reported, and our results showed a high incidence of recurrences of epithelial defects. We did not find any difference between overlay and inlay techniques in terms of healing time and recurrence rate.

Phototherapeutic keratectomy for decentration and central islands after photorefractive keratectomy.

PURPOSE: To determine visual outcomes after treatment of decentration and central islands occurring after photorefractive keratectomy (PRK). DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Patients (n = 14) who exhibited decentration or central islands after PRK and photoastigmatic keratectomy (PARK). METHODS: Fourteen eyes with post-PRK decentration (group I) or central islands (group II) were treated by transepithelial phototherapeutic keratectomy guided by epithelial fluorescence without modulating agents, and subsequently were treated with PRK or PARK. Mean follow-up time was 9 months (range, 45 days-21 months). MAIN OUTCOME MEASURES: We analyzed pre- and postoperative keratometry, refractive errors, uncorrected visual acuity (UCVA), best-corrected visual acuity, and haze. In group I, we also measured pre- and postoperative decentration; in group II, we compared pre- and postoperative central island power. RESULTS: Group I showed improvement in centration (P = 0.003). Group II showed decreased central island power (P = 0.18). -LogMAR UCVA improved from 0.59 (20/80(+1)) to 0.17 (20/30) (P = 0.03) and from 0.74 (20/100(-1)) to 0.21 (20/30(-1)) (P = 0.01) after retreatment of groups I and II, respectively. CONCLUSIONS: Retreatment of patients having decentration and central islands after PRK results in improved visual outcomes.