Long-term Refractive Results of Myopic LASIK Complicated With Intraoperative Epithelial Defects

Keratitis following laser refractive surgery: Clinical spectrum, prevention and management

Laser refractive surgery (LRS) is one of the most demanding areas of ophthalmic surgery and high level of precision is required to meet outcome expectations of patients. Post-operative recovery is of vital importance. Keratitis occurring after LRS can delay visual recovery. Both surface ablations [Photorefractive keratectomy (PRK)] as well as flap procedures [Laser in-situ keratomileusis (LASIK)/Small incision lenticule extraction] are prone to this complication. Reported incidence of post-LRS infectious keratitis is between 0% and 1.5%. The rate of infections after PRK seems to be higher than that after LASIK. Staphylococci, streptococci, and mycobacteria are the common etiological organisms. About 50–60% of patients present within the first week of surgery. Of the non-infectious keratitis, diffuse lamellar keratitis (DLK) is the most common with reported rates between 0.4% and 4.38%. The incidence of DLK seems to be higher with femtosecond LASIK than with microkeratome LASIK. A lot of stress is laid on prevention of this complication through proper case selection, asepsis, and use of improved protocols. Once keratitis develops, the right approach can help resolve this condition quickly. In cases of suspected microbial keratitis, laboratory identification of the organism is important. Most lesions resolve with medical management alone. Interface irrigation, flap amputation, collagen cross-linking and therapeutic penetrating keratoplasty (TPK) are reserved for severe/non-resolving cases. About 50–75% of all infectious keratitis cases post LRS resolve with a final vision of 20/40 or greater. Improved awareness, early diagnosis, and appropriate intervention can help limit the damage to cornea and preserve vision.

Femtosecond-assisted LASIK flaps resistant to lift secondary to corneal epithelial defects: Case reports and ex vivo studies

PURPOSE

To evaluate why epithelial defects created before femtosecond laser ablation result in laser in situ keratomileusis (LASIK) flaps resistant to lift.

SETTING

Boston Eye Group, Brookline, Massachusetts, USA.

DESIGN

Case reports and ex vivo studies.

METHODS

To examine the mechanism of resistance to flap lift after epithelial defects, flap creation with a femtosecond laser was performed in 30 fresh porcine eyes. Before ablation, the eyes were assigned to 3 groups. Group 1 was a control group with intact corneal epithelium. In Group 2, a central 2.0 mm corneal epithelial defect was created by marking it with a 2.0 mm trephine. In Group 3, a peripheral 2.0 mm epithelial defect was created similarly. After the femtosecond laser procedure was performed, the flaps were lifted and the resistance to lift was documented. The corneas were further examined using anterior segment optical coherence tomography.

RESULTS

In Group 1, no resistance was felt during flap lifts. In Group 2, significant resistance was encountered at the edge of the epithelial defects and the flaps could not be lifted in 7 of 10 eyes. In Group 3, similar significant resistance was encountered in all 10 eyes. Six of 10 flaps could not be lifted. Anterior segment optical coherence tomography from a representative cornea from Group 2 demonstrated a deeper dissection plane in the area where the overlying epithelium was missing.

CONCLUSION

Epithelial defects can interfere with proper LASIK flap creation with the femtosecond laser. This seems to be attributable to a deeper cutting plane under the area of the epithelial defects compared with the surrounding area with intact epithelium.

Effect of a hyperosmotic agent on epithelial disruptions during laser in situ keratomileusis

PURPOSE

To evaluate the incidence of epithelial disruptions during primary laser in situ keratomileusis (LASIK) with the use of a preoperative hyperosmotic treatment comprising sodium chloride 5% ophthalmic ointment (Muro-128) and to identify the incidence of epithelial disruptions in various demographic populations.

SETTING

TLC Laser Eye Center, McLean, Virginia, USA.

DESIGN

Comparative case series.

METHODS

Using a matched-pair design, hyperosmotic treatment was randomized to 1 eye of patients having bilateral LASIK. The primary outcome measure, epithelial integrity, was assessed in each eye. Epithelial integrity was evaluated in groups defined by characteristics that included age, sex, ethnicity, skin type, presence or absence of rosacea, eye color, and hair color.

RESULTS

The study evaluated 496 eyes of 248 patients. The preoperative hyperosmotic treatment was associated with significantly less corneal epithelial disruption, as indicated by an epithelial integrity score. Compared with control eyes, the rate of corneal epithelial disruptions in the population of treated eyes decreased by 40% (relative risk, 0.60; 95% confidence interval [CI], 0.38-0.95). Among the characteristics studied, age was the best predictor of corneal epithelial disruptions; every 1-year increase in age was associated with a 9.0% increase in the risk for corneal epithelial disruptions (odds ratio [OR], 1.09; 95% CI, 1.05-1.13). Eyes of patients older than 34 years had a 4.4 times greater odds of being associated with epithelial disturbances than eyes of patients 34 years or younger.

CONCLUSIONS

The preoperative use of hyperosmotic agents can reduce the risk for intraoperative epithelial disruptions during LASIK. An increase in epithelial disruptions was associated with increasing age.

Risk factors for epithelial defect formation during laser in situ keratomileusis

PURPOSE

To analyze the occurrence of epithelial defects during primary laser in situ keratomileusis (LASIK) and identify predictive preoperative risk factors.

SETTING

Department of Ophthalmology, Emory University, Atlanta, Georgia, USA.

METHODS

The records of primary LASIK cases performed between January 2001 and May 2002 were retrospectively evaluated. Information abstracted included patient sex, age, and preoperative refraction (spherical equivalent) and the excimer laser used (Nidek EC-5000 or Alcon LADARVision). The primary outcome measure was the rate of intraoperative epithelial defect formation.

RESULTS

A total of 6984 primary LASIK cases were analyzed; these included 6067 cases with myopia and 917 cases with hyperopia. In all cases, the flaps were created with a Hansatome microkeratome (Bausch & Lomb). Most cases (75.6%) were performed with the Nidek EC-5000 excimer laser; all hyperopia cases were performed with the LADARVision laser. Overall, 647 cases (9.3%) had epithelial defects. There were 323 cases (9.5%) of epithelial defect in men and 319 (9.0%) in women (P = .4). The rate of epithelial defect increased with age; 124 (4.1%) occurred in patients younger than 40 years, and 523 (13.2%) occurred in patients older than 40 years (P<.0001). One hundred sixty cases (17.3%) were in hyperopic eyes and 487 cases (8.0%), in myopic eyes (P<.0001). Multivariate analysis of LADARVision cases showed that age older than 40 years and hyperopia were risk factors for epithelial defect (odds ratio 2.7 and 1.7, respectively; P<.0001 and P = .00002, respectively), while sex was not.

CONCLUSION

Risk factors for epithelial defect formation during LASIK included increasing patient age, especially older than 40 years, and preoperative hyperopia.

Infectious and noninfectious keratitis after laser in situ keratomileusis

PURPOSE

To retrospectively review the occurrence, treatment, and visual outcomes associated with various etiologies of keratitis as a postoperative complication of laser in situ keratomileusis (LASIK) at an academic surgical center.

SETTING

John A. Moran Eye Center, University of Utah, Salt Lake City, Utah, USA.

METHODS

The charts of 5618 post-LASIK patients (10 477 eyes) were reviewed for the development of keratitis. Occurrence rates, management regimens, and final best spectacle-corrected visual acuity (BSCVA) were reported for infectious and noninfectious keratitis etiologies.

RESULTS

Post-LASIK keratitis was diagnosed in 279 eyes. The keratitis was diagnosed as infectious in 33 eyes (12%) and as noninfectious in 246 eyes (88%). Infectious cases included 5 eyes (15%) with herpes simplex keratitis (HSV), 18 (55%) with adenoviral keratitis, and 10 (30%) with nonviral (including bacterial, fungal, and parasitic) keratitis. Of noninfectious cases, 193 (78%) were classified as diffuse lamellar keratitis (DLK), 36 (15%) as staphylococcal marginal hypersensitivity, and 17 (15%) as localized debris-related keratitis.

CONCLUSIONS

The occurrence of post-LASIK keratitis was 2.66%, with DLK being the most common diagnosis overall. The occurrence of noninfectious keratitis (2.34%) was 7.5 times greater than the occurrence of infectious keratitis (0.31%). Adenoviral keratitis had the best visual outcomes overall, with all 18 patients achieving 20/20 BSCVA. In contrast, all 5 eyes with HSV keratitis lost 1 or 2 lines of BSCVA. Excluding adenoviral keratitis, infectious etiologies had significantly worse visual outcomes than noninfectious etiologies at the 20/40 and 20/20 levels (P = .0013 and P<.001, respectively).