Nocturnal oxygen saturation in normal and asthmatic children.

At sea level, it appears that oxygen desaturation does not occur in normal children at night and that the desaturation that occurs in moderately severe asthmatic children with therapeutic levels of theophylline does not approach dangerously low levels.

Intravitreal amikacin in the treatment of bacterial endophthalmitis.

Intravitreal administration of broad-spectrum antibiotics is a widely accepted component of initial therapy for bacterial endophthalmitis. Four cases of culture-proved bacterial endophthalmitis are reported to demonstrate the safety of intravitreal administration of amikacin sulfate in conjunction with cephalosporins in patients. The benefits of using amikacin rather than gentamicin sulfate in intravitreal drug therapy are discussed, and a wider role for amikacin as the aminoglycoside of choice for initial intravitreal injection in presumed bacterial endophthalmitis is suggested.

The role of vitrectomy in the treatment of postoperative bacterial endophthalmitis. An experimental study.

While the diagnostic value of vitreous culture in the management of bacterial endophthalmitis is well established, the therapeutic value of vitrectomy in this condition is debated. The present experimental study uses an aphakic model of Staphylococcus aureus endophthalmitis in the rabbit. Animals were treated with the following: (1) intravitreal antibiotics alone; (2) intravitreal antibiotics with vitrectomy; (3) vitrectomy alone; and (4) no treatment. Eyes treated with antibiotics and vitrectomy displayed significantly clearer media at 14 days after therapy compared with eyes treated with antibiotics alone. There was also a greater tendency for eyes treated with antibiotics and vitrectomy to have negative cultures at 14 days, although this difference was not statistically significant. These findings are consistent with beneficial effects of therapeutic vitrectomy as an adjunct to intravitreal antibiotic therapy in an animal model of aphakic bacterial endophthalmitis.

Modulation of corneal wound healing after excimer laser keratomileusis using topical mitomycin C and steroids.

A 193-nm excimer laser system was used to create deep stromal ablations in seven New Zealand white rabbits and shallow ablations in three. Eyes were randomized for treatment with topical mitomycin C, steroids, and erythromycin; topical steroids and erythromycin; or topical erythromycin only. All treatment regimens were instituted twice daily for 14 days. All eyes reepithelialized normally within 3 to 5 days. During 10 weeks of follow-up, all eyes developed moderate reticular subepithelial haze without significant differences among treatment groups. Results of light, fluorescence, and electron microscopic examination showed anterior stromal scarring and markedly reduced new subepithelial collagen formation in the group treated with mitomycin C, corticosteroids, and erythromycin. Focal abnormalities of Descemet's membrane and endothelial abnormalities were present in all treatment groups. Combination therapy with topical steroids, mitomycin C, and erythromycin to control the corneal wound healing response after refractive laser surgery appears promising and warrants further study.

Ophthalmoscopic and histologic findings in cytomegalovirus retinitis treated with BW-B759U.

Recent reports have suggested a role for BW-B759U in the treatment of cytomegalovirus retinitis. The present study presents the ophthalmoscopic features in three treated patients, and examines the microscopic findings in the eyes of the first patient ever treated with BW-B759U for cytomegalovirus retinitis. Ophthalmoscopic findings of improvement on drug therapy included remission of perivascular infiltration, stabilization of the extent of the retinal area involved, and development of a pigmented chorioretinal scar in the involved area. Relapses occurred with cessation of therapy, and repeated courses of therapy were required. One patient developed a rhegmatogenous detachment with retinal breaks in an atrophic area of treated retinitis. Electron microscopic examination of the eyes of one patient disclosed the persistence of cytomegalovirus inclusions in retinal cells despite previous drug therapy. These findings suggest a virostatic action for BW-B759U.

Survey of patients with granular, lattice, avellino, and Reis-Bücklers corneal dystrophies for mutations in the BIGH3 and gelsolin genes.

OBJECTIVES: To search for novel mutations that cause corneal stromal dystrophies and to confirm or revise the clinical diagnosis of patients with these mutations. PATIENTS: Through review of the records of the Cogan Eye Pathology Laboratory at the Massachusetts Eye and Ear Infirmary, Boston, and of clinical records, we ascertained 14 unrelated patients with the clinical or histopathologic diagnosis of granular (3 cases), Avellino (5 cases), lattice (5 cases), or Reis-Bücklers (1 case) corneal dystrophy. METHODS: Clinical records and histopathologic findings of the index patients and their relatives were reviewed. Patients and selected relatives donated a blood sample from which leukocyte DNA was purified and assayed for mutations in the BIGH3 gene and, in 2 patients, the gelsolin gene, using the polymerase chain reaction and direct genomic sequencing. RESULTS: All index patients with the diagnosis of granular dystrophy or Avellino dystrophy had the missense mutation Arg555Trp or Arg124His, respectively, previously reported in the BIGH3 gene. Of the 5 index patients with a prior diagnosis of lattice dystrophy, 2 had the originally reported lattice mutation (Arg124Cys) in the BIGH3 gene, 1 had a more recently reported missense mutation (His626Arg) in the same gene, 1 had the missense mutation Asp187Asn in the gelsolin gene, and 1 had no detected mutation in either gene. Affected members of the family with Reis-Bücklers dystrophy did not carry the previously reported mutations Arg555Gln or Arg124Leu but instead carried a novel missense mutation Gly623Asp in the BIGH3 gene. CONCLUSIONS: Molecular genetic analysis can improve the accuracy of diagnosis of patients with corneal dystrophies. Two patients with a prior diagnosis of lattice corneal dystrophy had their diagnosis changed to gelsolin-related amyloidosis (1 case) or secondary, nonhereditary localized amyloidosis (1 case). A novel mutation in the BIGH3 gene that causes Reis-Bücklers dystrophy was uncovered through this analysis, and another recently reported novel mutation was encountered. These findings serve to expand our knowledge of the spectrum of pathogenic mutations in BIGH3.

Postkeratoplasty astigmatism with single running suture or interrupted sutures.

In a prospective randomized clinical trial we compared astigmatism after penetrating keratoplasty with two different suture techniques between two groups of patients (38 patients). The first group (18 patients) had a 24-bite single running 10-0 nylon suture (single running suture) with postoperative suture adjustment to decrease astigmatism. The second group (20 patients) had a combination of a 16-bite running 10-0 nylon suture and eight interrupted 10-0 nylon sutures (combined running and interrupted sutures) with selective postoperative removal of interrupted sutures to decrease astigmatism. The single running suture resulted in a lower postoperative astigmatism than a combined running and interrupted suture technique (single running suture, 2.7 +/- 2.2 diopters; combined running and interrupted sutures, 3.9 +/- 2.5 diopters; P < .02). Average length of follow-up was similar in both groups (single running suture, 9.0 +/- 2.2 months and combined running and interrupted sutures, 8.4 +/- 2.2 months). Minimal length of follow-up was six months in both groups. No running sutures were broken. The adjustable single running suture technique provided greater control of astigmatism after penetrating keratoplasty than a technique using a combination of a 16-bite running suture and eight interrupted sutures.

Comparison of suture-in and suture-out postkeratoplasty astigmatism with single running suture or combined running and interrupted sutures.

PURPOSE: To evaluate postkeratoplasty astigmatism between two suture techniques 2 to 4 years postoperatively in a group of patients previously studied 9 months postoperatively. METHODS: Thirty-two patients who underwent penetrating keratoplasty were randomly assigned to one of two groups. Group 1 (16 patients) had a 24-bite single running 10-0 nylon suture with postoperative suture tension adjustment; group 2 (16 patients) had combined 16-bite running and eight interrupted 10-0 nylon sutures with selective postoperative removal of interrupted sutures. During long-term follow-up, the running suture was removed in 19 patients (59%). RESULTS: Postoperative astigmatism was slightly lower in patients with the single running suture technique when sutures were in place and was slightly greater after the sutures were removed compared with the combined running and interrupted suture technique (sutures in: single running suture +/- SD, 2.6 +/- 1.2 diopters [five patients, 31%]; combined running and interrupted sutures, 3.8 +/- 1.1 diopters [eight patients, 50%]; sutures out: single running suture, 3.3 +/- 1.3 diopters [11 patients, 69%]; combined running and interrupted sutures, 2.8 +/- 1.5 diopters [eight patients, 50%]). These differences were not statistically significant (sutures in, P < .13; sutures out, P < .46). Averages of follow-up were group 1,48.3 +/- 10.6 months and group 2, 46.3 +/- 13.0 months. Follow-up ranged from 23 to 60 months. CONCLUSIONS: Postoperative astigmatism 4 years after penetrating keratoplasty is similar for these two suturing techniques, with or without residual sutures. A single running suture results in more rapid visual rehabilitation and less early astigmatism compared with the combined interrupted and running suture technique.

The influence of aphakia and vitrectomy on experimental retinal toxicity of aminoglycoside antibiotics.

To study the effect of lens and vitreous surgery on the dose threshold of aminoglycoside-induced retinal toxicity, we performed extracapsular lens extraction (Group 1) or lensectomy and vitrectomy (Group 2) on Dutch Belted rabbits. A single dose of amikacin or gentamicin ranging from 100 to 4,000 micrograms was administered intravitreally. Retinal toxicity was examined by light and transmission electron microscopy seven days after injection. Both groups showed retinal toxicity after 400 micrograms of gentamicin or 1,500 micrograms of amikacin, doses identical to those causing toxicity in intact, phakic rabbit eyes. Thus, neither surgical procedure increased the toxic threshold of injected aminoglycoside. Given the accelerated aminoglycoside clearance reported in aphakic eyes, these findings imply that the mechanism of aminoglycoside toxicity may be related to peak drug concentration rather than duration of tissue exposure.

Clinical analysis of excimer laser photorefractive keratectomy using a multiple zone technique for severe myopia.

PURPOSE: In an investigational procedure, excimer laser photorefractive keratectomy for severe myopia was performed at three clinical trial centers to determine the effectiveness of the multiple zone technique. METHODS: A VisX Model Twenty/Twenty excimer laser (VisX, Santa Clara, California) was used to perform photorefractive keratectomy on 14 severely myopic eyes (-10.37 to -24.5 diopters) of 12 patients by using a multiple zone technique. Postoperative follow-up ranged from six months to two years; retreatments were performed on four patients, with a follow-up of at least nine months. RESULTS: At six months postoperatively, before retreatment, three of the 14 eyes were within 2 diopters and seven of the 14 eyes were within 4 diopters of attempted correction. Regression of effect to more severe myopia was worse in five eyes treated with nitrogen gas blowing. Retreatments also demonstrated considerable myopic regression. Three patients had loss of two or more lines of best-corrected visual acuity, and these patients also had moderate or severe levels of haze. CONCLUSION: Excimer laser photorefractive keratectomy for severe myopia using a multiple zone technique is associated with considerable regression, haze, and loss of best-corrected visual actuity, especially when performed in association with nitrogen gas blowing.

Late onset of haze associated with viral keratoconjunctivitis following photorefractive keratectomy.

BACKGROUND: To report a newly recognized cause of late onset of corneal haze following photorefractive keratectomy (PRK). METHODS: A 35-year old woman who underwent uneventful PRK and subsequently developed viral keratoconjunctivitis 1 year after treatment. RESULTS: During resolution of the viral keratoconjunctivitis, the patient developed extensive central corneal subepithelial infiltrates and anterior stromal fibrosis in the PRK ablation zone. More than 1 year after the initial infection, the central subepithelial fibrosis persisted, complicated by myopic regression, central steep island on videokeratography, and loss of five lines of spectacle-corrected visual acuity. By the end of the second year after the infection, visual acuity had improved with disappearance of the central steep island on videokeratography. However, the myopic regression and subepithelial fibrosis remained. CONCLUSION: Patients who undergo PRK may be at greater risk of visual loss following viral keratoconjunctivitis secondary to persistent subepithelial infiltrates and/or stromal fibrosis within the PRK treatment zone.

Assessment of ablation zone centration after photorefractive keratectomy using a vector center of mass formula.

BACKGROUND: Adequate centration of keratorefractive surgical procedures is essential for a successful outcome. An accurate technique to mathematically describe the centration and topography of the ablation zone after photorefractive keratectomy (PRK) would be valuable in assessing the effects of these variables on subsequent visual results. METHODS: A vector center of mass formula and computerized videokeratography were used to study the postoperative treatment zone centration and topography of 17 consecutive highly myopic patients (-6.00 to 12.00 diopters [D]). Each had undergone PRK using either a single 6.0 mm (n = 11) or three-stepped ablation zone (n = 6), with good visual results. RESULTS: Calculations disclosed mean ablation zone decentration relative to the pupil center for all patients to be 0.20 +/- 0.16 mm using the vector center of mass formula. Areas of uniform central corneal dioptric power (mean diameter 3.4 +/- 0.8 mm) and surrounding transition zones of declining dioptric power (mean slope 1.61 +/- 0.44 D/mm) were also determined. CONCLUSION: A new vector center of dioptric power distribution that analyzes centration and transition zone topography offers a rigorous but straightforward means to assess the effects of refractive corneal surgery procedures on central corneal topography.

Evaluation of pentoxifylline in the prevention of haze after photorefractive keratectomy in the rabbit.

BACKGROUND: Pentoxifylline (PTX) is a methylxanthine derivative that, besides its hemorrheologic properties, possesses multiple physiologic effects at the cellular level. It has been used in keloid prevention due to its ability to inhibit the secretion of collagen and glycosaminoglycans from activated fibroblasts. METHODS: Ten New Zealand White (NZW) rabbits underwent a -7.00 diopters, 6.0 mm diameter photorefractive keratectomy after laser ablation of the epithelium with a VISX 20/20 excimer laser. The bare stroma was stained with fresh 0.5% dichlorotriazinyl aminofluorescein (DTAF). The procedure was performed on both eyes, 4 days apart. One eye received 1% Pentoxifylline qid and the other balanced salt solution qid as a control for 4 weeks, starting the same day of surgery. Two masked observers graded the amount of haze at 2, 4, 6, and 8 weeks after surgery using slit-lamp biomicroscopy. Three rabbits were sacrificed at 2 and 4 weeks followed by two rabbits at 6 and 8 weeks. The area between the DTAF-stained collagen to the base of the epithelium was measured using a digital image analyzer. RESULTS: There was no statistically significant difference in the amount of haze either by slit-lamp microscopy or by histological analysis between the pentoxifylline-treated eyes and the controls at any time interval (Student's t-test: 0.16 to 0.92) CONCLUSION: Pentoxifylline did not seem to affect haze formation in a PRK rabbit model. As no signs of toxicity were observed, further studies might examine higher concentrations or dose frequencies.

Multicenter study of photorefractive keratectomy for myopia of 6.00 to 8.00 diopters. VISX Moderate Myopia Study Group.

PURPOSE: To summarize the initial results of excimer laser photorefractive keratectomy (PRK) on 89 eyes of 80 patients with moderate myopia (myopia of -6.00 to -8.00 diopters [D]; mean -6.98 +/- 0.90 D) at nine investigational sites. METHODS: All treatments used an argon fluoride excimer laser (VISX, Inc, Santa Clara, Calif) using standard settings. Sixty eyes received single-zone 6.0-millimeter ablations and 29 eyes received two-zone ablations. Follow up ranged from 1 month (n = 89) to 6 months (n = 46). RESULTS: At 3 months, uncorrected visual acuity measured 20/40 or better in 75% and 20/20 or better in 18%; 78% were within +/- 1.00 D of intended correction, 38% were within +/- 0.50 D, and 9% lost two or more lines of spectacle-corrected visual acuity. At 6 months, uncorrected visual acuity measured 20/40 or better in 74% and 20/20 or better in 17%; 67% were within 1.00 D of intended correction, 38% within 0.50 D, and 2% (1/46) lost two lines of spectacle-corrected visual acuity. CONCLUSIONS: PRK for moderate myopia with large diameter ablation zones appears safe and more predictable than that done using smaller ablation zone diameters. Longer follow up is needed to better define stability, the effects of postoperative corticosteroids, and the use of single-versus double-zone ablations.

Cyclotorsion in the seated and supine patient.

We used Maddox double-rod measurements to determine if positionally induced ocular cyclotorsion occurs when a patient moves from the seated to supine position. Maddox double-rod measurements were determined twice while patients (N = 30) viewed a fixation light at a distance of 7 feet in both the seated and supine positions. The difference between axis measurements made in seated and supine positions was not statistically significant. There was also no significant difference between the two measurements made in the seated and in the supine positions. These data show that the eyes do not undergo positionally induced ocular cyclotorsion when a patient moves from a seated to a supine position.

Implantation of collagen plugs into incisional keratotomies.

PURPOSE: To evaluate whether supplementing incisional keratotomy bulk or gape with a biocompatible material enhances the refractive effect. SETTING: Refractive Surgery Laboratory, Massachusetts Eye and Ear Infirmary, Boston. METHODS: Collagen punctal plugs were implanted into astigmatic keratotomy (AK) incisions in the right eyes of five rabbits and six adult cats. The left eyes had AK only and served as controls. RESULTS: Some of the postoperative corneal topographic measurements suggested an enhanced refractive effect. At 1 month, histology demonstrated no remaining implant material and no inflammation in or near the incisions. CONCLUSIONS: Implanting a biocompatible material into AK incisions in two live animal models appears to be safe and may enhance the effect of the incisions. Further study is needed to quantify the magnitude and duration of any refractive effect.

Contour resolution of the EyeSys Corneal Analysis System.

We investigated the accuracy of a conventional videokeratography instrument (Corneal Analysis System, EyeSys Laboratories) to measure contour information using specialized software developed by the manufacturer. Seven calibrated spheres were measured and the results tabulated. A contour resolution for all spheres for all reflected rings was found to be +/- 0.0047 mm, representing a 95% confidence interval. This level of resolution is high enough to obtain clinical value from using the EyeSys instrument as a contour measuring device.

Dilute ethanol versus mechanical debridement before photorefractive keratectomy.

PURPOSE: To compare 18% ethanol versus mechanical epithelial debridement in a group of patients having photorefractive keratectomy (PRK) for low to moderate myopia or astigmatism. SETTING: Hospital San Jose de Monterrey, Mexico. METHODS: This prospective, paired study comprised 18 patients who had bilateral PRK between June 1994 and March 1995. One eye had ethanol (alcohol) debridement and the other, mechanical. Time between PRKs was about 6 months. The two groups (alcohol versus mechanical) were compared for rate of re-epithelialization, refractive outcome, improvement in uncorrected visual acuity (UCVA), subjective haze grading, and loss of best corrected visual acuity (BCVA). RESULTS: There was a nonsignificant trend in the alcohol-treated eyes toward a more rapid visual recovery. One week after PRK, 76% in the alcohol group but only 31% in the mechanical group had a UCVA of 20/40 or better. There were no significant between-group differences in rate of re-epithelialization, refractive outcome, subjective haze grading, and loss of BCVA. CONCLUSION: Chemical de-epithelialization with dilute ethanol appears to be a simple, safe, and effective alternative to mechanical scraping before PRK and might promote faster visual rehabilitation.

Natural history of corneal astigmatism after cataract surgery.

Little information on the natural course of corneal astigmatism following cataract surgery exists. We report a prospective, computerized analysis of postoperative astigmatism, based on keratometry measurements, of 137 cases of extracapsular cataract extraction with intraocular lens implantation performed by one surgeon. No sutures were cut postoperatively. Surgery induced 1.44 diopters (D) of with-the-rule astigmatism at one month, which declined at a rate of 0.77 D and 0.35 D per month for the next two months, respectively, with a more gradual decline thereafter. The mean surgically induced astigmatism at the last postoperative visit ranged from 0.29 D at six months (minimum follow-up) to 1.23 D at 48 months; both were against-the-rule. Mean follow-up was 28.92 months. These findings may be technique specific and suggest that (1) corneal curvature continues to change slowly even two to four years postoperatively; (2) most patients develop against-the-rule astigmatism, thus more with-the-rule astigmatism is desirable in the early postoperative period; (3) selective suture removal is necessary only when significantly more than 3.00 D of surgically induced with-the-rule astigmatism is present.

Temperature measurements during phacoemulsification and erbium:YAG laser phacoablation in model systems.

PURPOSE: To compare the potential for thermal injury to ocular structure resulting from phacoemulsification ultrasound energy and erbium:YAG (Er:YAG) laser output. SETTING: Morse Laser Laboratory, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston. METHODS: Ultrasonic phacoemulsification energy and ER:YAG laser output (10 J/cm2, 10 Hz, 0.3 watts) sufficient for lens removal were applied to model systems and human cadaver eyes. Temperatures were measured with ultrafine thermocouples interfaced to a microcomputer data acquisition system. RESULTS: Although greater than 95% of energy from laser output is converted to thermal energy, temperature rise in model systems and cadaver eyes was 10 to 15 times greater after pulsed application of ultrasound energy than after Er:YAG laser application. At 100% power, approximately 4 watts of ultrasound power is converted to heat. Temperature rise following both laser and ultrasound applications decreased with irrigation in cadaver eyes and increasing volume in a model system. With continuous irrigation (20 cc/min), the temperature rise at 2 minutes measured at the corneal endothelial surface, within the corneal stroma, and in the anterior chamber angle of cadaver eyes was approximately 0.5 degrees Celsius (degrees C) after laser application and 7.0 degrees C after ultrasound application. Without irrigation, temperatures rose 2.5 degrees C after laser application and 35.0 degrees C after ultrasound application. CONCLUSION: At operating parameters sufficient for lens removal, the Er:YAG laser imparted less thermal energy to whole eyes and model systems than ultrasonic phacoemulsification.