Microbial cultures of the microkeratome blade immediately after flap construction in laser in situ keratomileusis

Risk Evaluation of Human Corneal Stromal Lenticules From SMILE for Reuse

PURPOSE

To investigate the pathogenicity and immunogenicity of human corneal stromal lenticules from small incision lenticule extraction (SMILE).

METHODS

Serological testing was completed prior to sample collection to rule out infectious diseases. Pathogens herpes simplex viruses (HSV) type 1 and type 2 were screened for by real-time fluorescent quantitative polymerase chain reaction, and bacteria, fungi, and Acanthamoeba from 128 lenticules of 64 patients were cultured. A total of 132 lenticules from 93 patients were randomly assigned to the fresh group, -78 °C anhydrous glycerol preservation group (glycerol group), and 0.1% sodium dodecyl sulfate decellularization group (SDS group) in pairs and detected by immunohistochemistry, Western blot, transmission electron microscopy, transmittance, and nanoindentation.

RESULTS

The fresh lenticules were all negative for HSV-1, HSV-2, bacteria, fungi, and Acanthamoeba. HLA-I A/B/C and HLA-II DR antigens were all expressed in fresh lenticules but were clearly reduced after preservation at -78 °C in anhydrous glycerol or decellularization in 0.1% SDS. The collagen fibers of the lenticules in the fresh group were regularly arranged, and the keratocytes were intact. The fibers in the glycerol group were regularly arranged, and the integrity of keratocytes was destroyed. The fibers in the SDS group were disordered and had no cellular structure. The transmittance and Young's modulus were highest in the fresh group, lower in the glycerol group, and lowest in the SDS group.

CONCLUSIONS

Risk of infection is low, but risk of rejection exists on the reuse of fresh human corneal stromal lenticules from SMILE. Anhydrous glycerol preservation at -78 °C is an ideal method for reducing antigens without damaging the structure and function of lenticules. [J Refract Surg. 2021;37(1):32-40.].

Clinical diagnosis and treatment of rare painless keratitis caused by three pathogens: clinical practice and experiential discussion

There have been numerous reports regarding the occurrence of keratitis in patients with soft contact lenses, but few reports in patients with rigid gas permeable contact lenses. To the best of our knowledge, the occurrence of infection associated with three species of pathogens has never been reported. Here, we describe a patient who exhibited refractory painless keratitis caused by three pathogens (Staphylococcus epidermidis, Acanthamoeba, and herpes simplex virus) and summarize similar reports published at multiple centers worldwide, with the aim of providing guidance for clinicians who might encounter mixed-type corneal infections. We describe the results of many ophthalmologic and laboratory investigations, which guided our treatment selection. We achieved good treatment efficacy, such that the patient exhibited a corrected visual acuity of 20/20 in the affected eye after a series of treatments, including curettage of ulcer lesions. Corneal infections caused by multiple pathogens are challenging in clinical practice. This summary of our experience in patient diagnosis and treatment can help clinicians to achieve a favorable prognosis in treatment of future patients.

Microbial keratitis after corneal laser refractive surgery

Corneal laser refractive surgery is increasingly being performed on patients with the aim of improving unaided vision. Most candidates for surgery have excellent spectacle- or contact lens-corrected vision. Although microbial keratitis following refractive surgery is a rare complication, and usually has a good visual outcome, it can be sight-threatening. The spectrum of pathogens differs to other causes of microbial keratitis, such as contact lens-associated keratitis, and a different management approach is required. Postoperatively, patients are prescribed topical steroids and broad-spectrum topical antibiotics, typically fluoroquinolones. These do not cover unusual organisms, such as fungi, Nocardia, Acanthamoeba and some atypical mycobacteria. In post-laser-assisted in situ keratomileusis microbial keratitis, the lamellar flap should be lifted to acquire samples for specific microbiological examination, including these atypical organisms. Confocal microscopy is a noninvasive test that provides morphological information, and is operator dependent, but may assist in the rapid diagnosis of fungal, Acanthamoeba or Norcardia keratitis. PCR is not in widespread use, but has high sensitivity and specificity, and may facilitate early diagnosis and specific treatment of the causative organism, which is critical in obtaining the best clinical outcome.

Microbial keratitis trends following refractive surgery: results of the ASCRS infectious keratitis survey and comparisons with prior ASCRS surveys of infectious keratitis following keratorefractive procedures

In 2008, the American Society of Cataract and Refractive Surgery (ASCRS) surveyed its 9121 United States and international members to evaluate the changing trends and incidence, culture results, treatment, and visual outcomes of infectious keratitis following keratorefractive procedures worldwide. This paper presents and analyzes the results with comparisons to the data in surveys conducted in 2001 and 2004. Nineteen infections were reported by 14 surgeons who had performed an estimated 20,941 keratorefractive procedures, an incidence of 1 infection in every 1102 procedures. Sixteen cases presented in the first postoperative week, 1 case during the second week, 1 case between the second and fourth weeks, and 1 case at 1 month or later. The 16 cases that presented in the first week were diagnosed at initial presentation. The most common organism cultured was methicillin-resistant Staphylococcus aureus (MRSA). Microbial keratitis following refractive surgery is an increasingly recognized sight-threatening complication.

A rare devastating complication of LASIK: bilateral fungal keratitis

Purpose. To report an unusual case of severe bilateral fungal keratitis following laser in situ keratomileusis (LASIK). Method. A 48-year-old man developed bilateral diffuse corneal infiltration two weeks after LASIK. The corneal scrapings revealed fungal filaments but cultures were negative. Results. The corneal ulceration was improved on the left eye whereas spontaneous perforation occurred and finally evisceration was needed on the right eye despite topical and systemic antifungal treatment. Conclusions. Fungal keratitis, especially with bilateral involvement, is a very rare and serious complication of LASIK surgery. Clinical suspicion is crucial because most of fungal keratitis are misdiagnosed as bacterial keratitis and can lead serious visual results, even eye loss.

Bacterial contamination of needles used for intravitreal injections: a prospective, multicenter study

PURPOSE

To determine the incidence of bacterial contamination of needles used for intravitreal injections.

METHODS

Patients undergoing intravitreal injections were enrolled prospectively. No pre-injection antibiotics were administered. Following povidone-iodine irrigation, conjunctival cultures were taken and the injection was performed. The needle was cultured. A dry control needle was exposed to the surgical field and cultured.

RESULTS

No patients developed endophthalmitis. Eighteen injection needles (18%) yielded positive bacterial growth. The most commonly encountered organisms were Propionibacterium acnes (n = 8) and Staphylococcus epidermidis (n = 6). Four control needles showed positive growth, in 2 cases with the same organism as a matching positive used needle. The difference between contamination rates of used and control needles was significant (p = .002, McNemar's test).

CONCLUSIONS

Bacterial contaminants are present on a substantial proportion of needles. Since the needle contacts both the ocular surface and the vitreous, it is possible that inoculation of the vitreous cavity occurs in such cases.

Microkeratome complications

PURPOSE OF REVIEW

Complications from laser in-situ keratomileusis surgery are extremely rare. However, most of the complications involve construction of the corneal flap, which is fashioned using various mechanical or femtosecond laser microkeratomes. Here, we review and discuss complications of microkeratome flaps.

RECENT FINDINGS

Several large studies of microkeratome laser in-situ keratomileusis cases report a similar set of complications: partial or irregular flaps, buttonholes, and free flaps. Risk factors for these complications include increased age, preoperative hyperopia, and years of contact lens wear. Numerous animal and clinical studies have shown that the femtosecond platform produces flaps with greater stability with more consistent and accurate dimensions than the mechanical microkeratome. However, there is no significant difference in final visual outcome.

SUMMARY

The aim of this review is to report complications associated with mechanical microkeratomes in the construction of laser in-situ keratomileusis flaps and to see whether there is a significant disadvantage compared with the femtosecond laser.