Lênio Souza Alvarenga

An outbreak of Mycobacterium chelonae infection after LASIK

OBJECTIVE To describe an outbreak of mycobacterial keratitis after laser in situ keratomileusis (LASIK), including the microbiologic investigation, clinical findings, treatment response, and outcome. DESIGN Retrospective, noncomparative, interventional case series. PARTICIPANTS Patients (n = 10) who underwent LASIK surgery between August 22 and September 4, 2000, and developed mycobacterial infection. METHODS Patients were prospectively followed in relation to microbiologic investigation, clinical findings, treatment response, and outcome. MAIN OUTCOME MEASURES Most patients underwent bilateral simultaneous LASIK. Postoperative infection was signaled by the appearance of corneal infiltrates in the third postoperative week. The microbiologic workup was performed on cultures obtained either by direct scraping of the cornea or by lifting the flap. Medical therapy was instituted based on drug susceptibility testing. Surgical interventions such as corneal debridement and flap removal were performed during recurrences or when there was no satisfactory clinical response. RESULTS Cultures revealed Mycobacterium subspecies chelonae. Patients were treated with topical clarithromycin (1%), tobramycin (1.4%), and ofloxacin (0.3%). Oral clarithromycin (500 mg twice a day) was prescribed for those patients who did not respond clinically to topical treatment. Four eyes healed on this regimen. Flap removal was necessary in seven eyes. CONCLUSIONS This report highlights mycobacteria as an etiologic infectious agent after LASIK. Diagnosis can be difficult and is often delayed. The treatment mainstay is prolonged antibiotic therapy. Surgical debridement and flap removal may shorten the disease course.

Infectious post-LASIK crystalline keratopathy caused by nontuberculous mycobacteria.

Purpose. To report three cases of infectious crystalline keratopathy caused by non-tuberculous mycobacteria after LASIK surgery. Methods. Interventional case reports and literature review. Results. Infectious keratitis with clinical features of crystalline keratopathy after LASIK is described. Culture revealed Mycobacterium chelonae from the corneal scrapings of the three patients, all of whom underwent medical and surgical (debridement) treatment. Conclusions. Mycobacteria may cause infectious crystalline keratopathy after LASIK. The presence of crystalline keratopathy in patients that underwent LASIK must be considered an indicator of nontuberculous mycobacteria infection. Microbiologic work-up of a corneal specimen is required for the institution of appropriate therapy.

Aerobic bacterial conjunctival flora in diabetic patients.

Objective To study the aerobic conjunctival flora of diabetic patients and its relation to the presence and level of diabetic retinopathy and the duration of the disease. Methods One hundred three patients from the diabetic retinopathy screening program of the Federal University of São Paulo with no evidence of ocular surface disease were included. The diabetic patient cohort was compared with 60 nondiabetic subjects. All patients underwent slit-lamp evaluation, conjunctival scrapings, and indirect ophthalmoscopy. Results The frequency of positive conjunctival cultures was significantly higher in the diabetic group (94.18%) than in the nondiabetic group (73.33%). Among diabetic patients, a significantly higher frequency of positive cultures was detected in those with diabetic retinopathy than in those without retinopathy. Neither the duration of the diabetes nor the hypoglycemic therapy correlated with the culture results. Coagulase-negative Staphylococcus was the most common microorganism isolated, and its identification was more frequent in patients with retinopathy than in those without diabetic retinopathy. Conclusion Diabetic patients have a significantly higher number of positive conjunctival cultures. The presence of diabetic retinopathy was correlated with an increase in positive cultures and a higher proportion of coagulase-negative Staphylococcus.

Intraoperative Microkeratome Complications in 47,094 Laser in situ Keratomileusis Surgeries

PURPOSE We evaluated the incidence and intraoperative microkeratome-related complications in laser in situ keratomileusis (LASIK). METHODS We present non-randomized, retrospective, comparative, interventional case series. We reviewed the records of patients who underwent LASIK from August 2000 to March 2004 at Excimer Laser Santa Cruz, São Paulo, Brazil (47,094 eyes). We identified 369 eyes (0.0078%) with an intraoperative complication. Data were collected regarding microkeratome, average keratometric power, and type of complication. RESULTS The Hansatome microkeratome was the most common microkeratome used (34,182 eyes; 73%), followed by the Automated Corneal Shaper-ACS (11,164 eyes, 24%) and the Nidek MK-2000 (1748 eyes, 3.7%). Intraoperative complications were more common with the ACS (1.26%) than with the Hansatome (0.63%) and MK-2000 (0.63%) (P<.001; P=.03; respectively). Complications included incomplete flaps (0.23%), buttonholes (0.13%), thin flaps (0.08%), and free flaps (0.08%). Buttonholes were more frequent with the ACS (0.34%) than with the Hansatome (0.06%) (P<.001) and free flaps were more common with the ACS (0.20%) and MK-2000 (0.29%) than with the Hansatome (0.04%) (P<.001). Keratometric power of eyes with intraoperative complications was significantly higher in the ACS group compared to the Hansatome group. CONCLUSIONS Intraoperative complications were more common with the ACS than with the Hansatome or MK-2000. Buttonholes were most frequent with the ACS, and the Hansatome had the lowest incidence of free flaps.

Corneal graft survival after therapeutic keratoplasty for Acanthamoeba keratitis

Purpose:  To describe corneal graft survival and visual outcome after therapeutic penetrating keratoplasty in patients with Acanthamoeba keratitis (AK) that is unresponsive to clinical treatment.

Factors Modulating p63 Expression in Cultured Limbal Epithelial Cells

Purpose: The expression pattern of p63, a homologue of the transcription factor p53, and whether it can be used as a corneal epithelial stem cell specific marker remain controversial. We investigated the p63 expression pattern in cultured limbal epithelial cells at different time points in culture, in sparse and confluent cultures, after growth factor starvation, and in single-cell-derived colonies. Methods: Harvested limbal epithelial cells were plated at 2.5 (sparse) or 5 (dense) × 104 cells/cm2 and evaluated for p63 expression at day 1, day 4, day 7, after starvation for 72 hours, or in colonies derived from single cells. Expression of corneal lineage specific differentiation marker keratin 3 (K3) was correlated with p63 expression. Results were compared by 1-way ANOVA. Results: More than 85% (85%-90%) of cells expressed p63 on day 1 regardless of cell plating density. On day 4, sparsely plated cultures were subconfluent and demonstrated high p63 expression (87.4%), whereas densely plated cells were confluent and had markedly reduced p63 expression (16.9%). Starvation of subconfluent cultures arrested cell division but did not decrease p63 expression. High-p63-expressing cultures expressed low levels of K3, and this trend was reversed in confluent cultures. Most cells in all colonies derived from single cells expressed p63. Conclusions: The majority of corneal limbal epithelial cells express p63 in colonies derived from single cells and in subconfluent cultures regardless of time in culture or continuance of cell division. This suggests that p63 expression in culture cannot be used as a marker for stem cells. Significantly reduced number of cells express p63 in confluent cultures, associated with increased cell-cell contact. It is notable that these cells continue to express p63 amid areas of increased cell-cell contact several days after cultures have attained full confluency. This may represent a unique subpopulation of cells that retain proliferative potential in a confluent culture and may be analogous to a subpopulation of stem cells present in vivo.

Cleaning Solutions as a Cause of Diffuse Lamellar Keratitis

PURPOSE To assess the capability of two microkeratome cleaning solutions in causing diffuse lamellar keratitis (DLK) in a rabbit model of laser in situ keratomileusis (LASIK). METHODS Two cleaning solutions (Palmolive 2:100 and Cidezyme 2:250) were tested. These solutions were diluted with balanced salt solution according to directions from the Hansatome microkeratome manual. Two additional solutions were prepared using an additional ten-fold dilution, creating a total of four study solutions. A LASIK flap was created in one eye each of 25 rabbits using the ALK Chiron microkeratome. The rabbits were divided into five study groups. The flaps were reflected and a drop of one of the study solutions (or BSS, control group) was placed on the interface. After 1 minute, the solution was washed out from the interface and the flap was repositioned. The eyes were examined at the slit lamp on postoperative days 1, 2, 3, 5, and 7. RESULTS In 12 eyes, a flap displacement was identified. Four eyes showed flap retraction and five others, epithelial ingrowth in flap margins. The incidence of these events did not differ among groups. Thirteen eyes were then evaluated for DLK. No DLK-like interface inflammation was seen in the studied eyes. CONCLUSION The cleaning solutions, when diluted as recommended by the microkeratome manufacturer, when in contact with the corneal stroma, and provided that the interface was washed with BSS did not cause DLK interface inflammation in rabbit LASIK models.

Wavefront Analysis in Asian-Brazilians

PURPOSE To compare the distribution of ocular higher order wavefront aberrations (third to sixth order) in the Brazilian population of Asian and non-Asian refractive surgery patients. METHODS Preoperative refractive and wavefront data were reviewed for 648 eyes in 324 patients who underwent custom ablation at the Excimer Laser Santa Cruz refractive surgery center in São Paulo, Brazil, from March 2002 to July 2005. Patients were divided into two groups: Asian patients and non-Asian patients, based on family history. Statistical analysis was performed to assess the differences between the groups with respect to manifest refractive spherical equivalent, astigmatism, pachymetry, OPD-root-square-mean (RMS) for a 6.0-mm pupil, total wavefront aberrations, third- to sixth-order higher order aberrations, and individual aberrations. RESULTS The mean spherical equivalent refraction in the Asian group of -4.38 diopters (D) was significantly higher than the spherical equivalent refraction of -3.46 D in the non-Asian group (t= -4.32; P=.00001). Comparison of the differences between groups with respect to higher order aberrations, coma, trefoil, quadrafoil, spherical aberration, higher order astigmatism, and pachymetry was not statistically significant. CONCLUSIONS Asian patients have a higher prevalence of myopia than non-Asian patients. No differences were noted in higher order aberrations between Asian and non-Asian patients.

Refractive outcome of Nidek OPD-scan customized ablations.

PURPOSE Custom ablation is an improved refractive laser treatment that aims to optimize the optical system of the eye. We report preliminary results of laser in situ keratomileusis (LASIK) using customized ablation and the Nidek OPD-Scan. METHODS We report a prospective, non-comparative interventional case series. After OPD-Scan analysis, patients underwent LASIK. Eighty-four eyes were included: 44 eyes were treated with Flex Scan, 22 eyes with customized ablation based on Nidek OPD-Scan analysis, and 18 eyes were treated with conventional (scanning slit) ablation. RESULTS Visual outcome did not differ among groups. No patient experienced a significant decrease (more than 1 Snellen line) in best spectacle-corrected visual acuity. CONCLUSIONS LASIK with the Nidek OPD-Scan system was safe and effective in this small group of patients.

Alterações da microbiota conjuntival e palpebral após uso tópico de lomefloxacina e tobramicina na cirurgia de catarata e cirurgia refrativa

Purpose: To determine the changes in the conjunctival and palpebral flora after topical use of 0.3% lomefloxacin and 0.3% tobramycin eye drops in the preoperative management of patients submitted to cataract and refractive surgery and to assess the chemosensitivity of bacterial isolates from the conjunctiva and eyelid to these antibiotics. Methods: A prospective study of the conjunctival and palpebral flora of patients submitted to cataract or to refractive (PRK or LASIK) surgery was performed. An analysis of the conjunctival and palpebral flora was carried out in patients before surgery without prophylaxis, after surgery during the use of prophylaxis (0.3% lomefloxacin or 0.3% tobramycin qid) and after discontinuation of the antibiotic. Results: Tobramycin and lomefloxacin reduced the number of positive cultures in specimens from the conjunctiva and eyelid of individuals submitted to cataract and refractive surgery. In both groups, isolated microorganisms displayed a greater resistance to tobramycin. In the group submitted to cataract surgery, patients treated with prophylactic tobramycin showed a slower recovery of the flora after discontinuation of the antibiotic than those treated with lomefloxacin, with the opposite occurring in the group submitted to refractive surgery. Conclusion: Both lomefloxacin and tobramycin were effective in reducing conjunctival and palpebral flora during drug administration. This reduction was more marked in the conjunctiva. Among the various bacterial isolates, there was a greater resistance to tobramycin than to lomefloxacin. The use of antibiotics reduced the incidence of positive cultures more for the conjunctiva than the eyelids.