W. Houdijn Beekhuis

Incidence of contact-lens-associated microbial keratitis and its related morbidity

BACKGROUND The incidence of contact-lens-associated microbial keratitis is uncertain and its related morbidity in the general population of contact-lens wearers is not known. We examined these issues in a prospective epidemiological study. METHODS We surveyed all practising ophthalmologists in the Netherlands to identify all new cases of microbial keratitis reported during a 3-month period in 1996. Follow-up telephone calls were made to examine ocular morbidity. We undertook annual nationwide telephone surveys between 1994 and 1997 to estimate the prevalence of contact-lens wear. FINDINGS Of 440 ophthalmologists contacted, 379 provided information. There were 92 cases of microbial keratitis; 17 used daily-wear rigid gas-permeable lenses, 63 daily-wear soft lenses, and 12 extended-wear soft lenses. The estimated annualised incidence of microbial keratitis was 1.1 per 10,000 (95% CI 0.6-1.7) users of daily-wear rigid gas-permeable lenses, 3.5 per 10,000 (2.7-4.5) users of daily-wear soft lenses, and 20.0 per 10,000 (10.3-35.0) users of extended-wear soft lenses (p<0.00001 for comparison between all groups), Five of the 92 patients achieved a final visual acuity of 20/70 or less. Pseudomonas and Serratia spp were the organisms most commonly isolated. Pseudomonas keratitis accounted for the largest mean diameter of corneal ulcers, the highest mean number of days in hospital, the greatest number of mean outpatients visits, and the poorest visual acuity outcome. INTERPRETATION The incidence of microbial keratitis among users of extended-wear soft contact lenses in the Netherlands is similar to that reported in the USA during 1989. Awareness of risk factors and improvement in contact-lens materials have not led to a decrease in incidence. Overnight wear should be strongly discouraged.

Trypan blue capsule staining to visualize the capsulorhexis in cataract surgery

A capsulorhexis may be difficult to perform in the absence of a red fundus reflex. Using 0.1 mL of trypan blue 0.1% to stain the anterior capsule in 30 patients with a mature cataract enabled us to visualize the capsulorhexis during phacoemulsification. No adverse reactions were observed up to 12 months after surgery. Trypan blue staining of the anterior capsule appears to be a safe technique to facilitate the performance of a capsulorhexis in the absence of a red fundus reflex.

Cyclotorsion: A possible cause of residual astigmatism in refractive surgery

Purpose: To determine whether cyclotorsion occurs when a subject changes from binocular to monocular fixation and to assess positionally induced cyclotorsion. Setting: Clinics of the Rotterdam Eye Hospital, Rotterdam, The Netherlands. Methods: The axis of astigmatism was measured with the Nidek handheld keratometer in 15 normal subjects under monocular and binocular fixation and in seated and supine positions. The limits of agreement for the repeatability of measurements with the Nidek keratometer were used to identify subjects with statistically significant cyclotorsion. Results: Two subjects (13%) showed statistically significant excyclotorsion when changing from binocular to monocular fixation in a seated position. In a supine position, 3 subjects (20%) showed excyclotorsion when the fixation changed. Body position itself had no influence on ocular torsion. Conclusions: Significant cyclotorsion may occur under monocular viewing conditions. If monocular photorefractive keratectomy procedures are based on binocular keratometry readings, an undercorrection of myopic astigmatism may result. Individuals at risk should be identified before refractive keratectomy is performed.

Newly Acquired Herpes Simplex Virus Keratitis after Penetrating Keratoplasty

BACKGROUND After penetrating keratoplasty for reasons unrelated to herpes simplex virus (HSV) keratitis, any nonspecific epithelial defect may still be caused by HSV. The purpose of this study is to determine the incidence of newly acquired herpetic keratitis and to assess contributing factors. METHODS The authors retrospectively studied the results of 2398 penetrating keratoplasties performed between 1980 and 1995. Three typical case histories are discussed. RESULTS Of 2112 patients in whom the primary diagnosis was not related to HSV keratitis, 18 presented with epithelial herpetic keratitis in their corneal graft. The incidence of newly acquired herpetic keratitis after penetrating keratoplasty was 1.2 per 1000 person-years. In most cases, the infection occurred in the first 2 years after the transplantation. Most often, well-known reactivating stimuli could have caused the HSV infection. CONCLUSIONS Herpes simplex virus keratitis may develop after penetrating keratoplasty even without a clinical history of HSV in the host. Thus, HSV should be considered in the differential diagnosis of a postpenetrating keratoplasty epithelial defect. The high incidence of this infection in the first 2 years after such surgery suggests a causal relation between corneal transplantation and the HSV infection.

Effect of oral acyclovir after penetrating keratoplasty for herpetic keratitis: a placebo-controlled multicenter trial.

OBJECTIVE To determine the prophylactic effect of oral acyclovir on the recurrence rate of herpetic eye disease after penetrating keratoplasty. DESIGN A randomized, double-masked, placebo-controlled multicenter trial. PARTICIPANTS Sixty-eight consecutive patients (68 eyes) with corneal opacities due to herpetic eye disease who underwent penetrating keratoplasty. INTERVENTION Oral acyclovir 400 mg twice daily or placebo tablets for 6 months. MAIN OUTCOME MEASURES The recurrence rate of herpetic eye disease-related events and rejection episodes, proven by viral cell culture or polymerase chain reaction. RESULTS During the 2-year follow-up period, there were 3 culture-proven herpetic eye disease recurrences in the acyclovir group and 9 in the placebo group. Lifetime survival analysis of the probability of remaining free from recurrence revealed a significantly reduced risk of recurrent herpetic disease in the acyclovir-treated group. CONCLUSION This study suggests that oral acyclovir effectively prevents herpes-related recurrences after penetrating keratoplasty in herpetic eye disease.

Effect of methods of myopia correction on visual acuity, contrast sensitivity, and depth of focus

Purpose: To psychophysically measure spherical and irregular aberrations in patients with various types of myopia correction. Setting: Laboratory of Experimental Ophthalmology, University of Groningen, Groningen, The Netherlands. Methods: Three groups of patients with low myopia correction (spectacles, soft contact lens, and Intacs) and 4 groups with high myopia correction (spectacles, rigid contact lens, Artisan claw lens, and laser in situ keratomileusis [LASIK]) had through‐focus contrast sensitivity measurements to establish the myopic shift and depth of focus. From these 2 parameters, spherical and irregular aberrations were determined using theoretical eye models and geometric optics. Visual acuity, stray light, and predictability were also studied. Results: There were no differences in best corrected visual acuity (BCVA) or best corrected contrast sensitivity between the low myopia groups. The Intacs group had a significantly larger depth of focus (P<.05). The results in the soft contact lens group were comparable to those in a human eye model with an average amount of spherical and irregular aberrations. The LASIK group had worse uncorrected visual acuity (UCVA) and best corrected contrast sensitivity than the spectacles, rigid contact lens, and Artisan claw lens groups (P<.05) due to the amount of spherical and irregular aberrations present after LASIK. The low and high myopia spectacles groups had average amounts of spherical and irregular aberrations. Conclusions: Neither surgical techniques nor contact lenses resulted in BCVA or best corrected contrast sensitivity that surpassed the values measured in the best corrected spectacles groups. The Artisan claw lens performed better than LASIK in UCVA, predictability, and best corrected contrast sensitivity.

Postoperative astigmatism after central vs eccentric penetrating keratoplasties

Six patients with markedly eccentric penetrating keratoplasties had severe corneal astigmatism (mean, 10.38 +/- 2.91 diopters). In four of these patients the flat meridian was lying in the direction of graft displacement. Laboratory experiments disclosed no statistically significant difference in diameter between the major and minor axes of the corneal buttons in the centrally and eccentrically trephined eyes and we could not elucidate the mechanism of the severe astigmatism. However, in the eccentrically trephined eyes the longer axis consistently lay in the direction of decentration whereas in the centrally trephined eyes the long axis was oriented randomly.

Corneal endothelial cell density after trypan blue capsule staining in cataract surgery

Abound,” Ocular Surgery News, September 1, 2001, pages 35, 38). The blade technology is undergoing clinical protocols in many areas such as glaucoma, vitreoretinal, refractive, and plastics. The blade has been used for bloodless tonsillectomy, bloodless resection of throat cancer, and revision of severe facial scars by plastic surgeons. Our hospital staff uses the unit constantly. We even do pediatric cataracts with it.

Intravitreal vancomycin and gentamicin concentrations in patients with postoperative endophthalmitis

BACKGROUND/AIMS To study the intravitreal antibiotic concentrations and the efficacy of an intravitreal dosing regimen to treat patients with postoperative bacterial endophthalmitis. This regimen, based on pharmacokinetic/pharmacodynamic considerations, relies on a repeat antibiotic injection of a lower dose than is generally used. METHODS In consecutive patients with suspected postoperative endophthalmitis a vitreous biopsy for bacterial culture was taken before 0.2 mg vancomycin and 0.05 mg gentamicin were injected intravitreally. After 3 or 4 days a second biopsy was taken for bacteriological culture and to measure intravitreal vancomycin and gentamicin concentrations, followed by a repeat injection of 0.2 mg vancomycin. RESULTS 17 patients entered the study. In 11 patients the initial bacterial culture was positive, predominantly coagulase negative staphylococci. All second vitreous biopsies were sterile. Intravitreal vancomycin levels varied between 2.6 and 18.0 μg/ml (mean 10.3 (SD 4.1) μg/ml) after 3 days and between 3.1 and 16.6 μg/ml (mean 7.5 (6.2) μg/ml) after 4 days which is well above the minimal inhibitory concentration for most micro-organisms. Concentrations of intravitreal gentamicin varied between 0.90 and 3.3 μg/ml (mean 1.6 (0.72) μg/ml) after 3 days and between 1.2 and 2.6 μg/ml (mean 1.9 (0.99) μg/ml) after 4 days. CONCLUSION This dosing regimen resulted both in adequate intravitreal vancomycin and gentamicin levels for over a week as well as in negative second cultures. This study also provides new information on intravitreal vancomycin and gentamicin concentration over time in patients with postoperative endophthalmitis.

Contact lens fitting in a patient with keratectasia after laser in situ keratomileusis

We present a case of unilateral iatrogenic keratectasia developing 15 months after bilateral laser in situ keratomileusis using a broad-beam excimer laser (Bausch & Lomb Keracor 116) to treat -3.5 -1.5 x 85 diopters of myopia. Preoperative pachymetry in the eye measured 450 microm without topographical changes suggesting keratoconus or forme fruste keratoconus. Contact lens fitting to provide 20/25 visual acuity is described.