J. James Rowsey

Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study One Year After Surgery

The Prospective Evaluation of Radial Keratotomy (PERK) study is a nine-center, self-controlled clinical trial of a standardized technique of radial keratotomy in 435 patients who had physiologic myopia with a preoperative refraction between -2.00 and -8.00 diopters. The surgical technique consisted of eight incisions using a diamond micrometer knife with blade length determined by intraoperative ultrasonic pachymetry and the diameter of central clear zone determined by preoperative refraction. At one year after surgery, myopia was reduced in all eyes; 60% were within +/- 1.00 diopter of emmetropia; 30% were undercorrected and 10% were overcorrected by more than 1.00 diopter (range of refraction, -4.25 to +3.38 D). Uncorrected visual acuity was 20/40 or better in 78% of eyes. The operation was most effective in eyes with a refraction between -2.00 and -4.25 diopters. Thirteen percent of patients lost one or two Snellen lines of best corrected visual acuity. However, all but three eyes could be corrected to 20/20. Ten percent of patients increased astigmatism more than 1.00 diopter. Disabling glare was not detected with a clinical glare tester, but three patients reduced their driving at night because of glare. Between six months and one year, the refraction changed by greater than 0.50 diopters in 19% of eyes.

Endophthalmitis: current approaches.

Seventy patients referred with a diagnosis of endophthalmitis underwent anterior chamber and vitreous taps with intracameral antibiotic injections. Fifty-four eyes were culture positive, 34 (63%) after previous intraocular surgery, 12 (22%) had sustained penetrating trauma, and 8 (15%) resulted from a metastatic infection. Of 61 total isolates, 48 (79%) were gram positive, 9 (15%) were gram negative, and 5 (8%) were fungi. Visual recovery after surgery was related to the relative virulence of the organisms isolated. Twenty-four (44%) eyes achieved 20/400 or better vision, but only seven (13%) obtained 20/40 or better vision. Patients with a markedly abnormal ERG operatively demonstrated poor visual acuity recovery, while patients with near normal ERG recovered better vision. The authors currently recommend vitrectomy in patients with endophthalmitis whenever the retina cannot be visualized.

Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study Five Years after Surgery

In the Prospective Evaluation of Radial Keratotomy (PERK) Study, 793 eyes of 435 patients with 2 to 8 diopters (D) of myopia received a standardized surgery consisting of 8 incisions with a diamond-bladed knife set at 100% of the thinnest paracentral ultrasonic corneal thickness measurement and a diameter of the clear zone of 3.0 to 4.5 mm; 97 eyes (12%) received an additional 8 incisions. There were 757 eyes (95%) followed for 3 to 6.3 years. After surgery, uncorrected visual acuity was 20/40 or better in 88% of eyes. The refractive error was within 1 D of emmetropia for 64% of eyes; 19% were myopic and 17% were hyperopic by more than 1 D. Between 6 months and 5 years after surgery, 22% of the eyes had a refractive change of 1 D or more in the hyperopic direction. For 25 eyes (3%) there was a loss of 2 or more lines of best spectacle-corrected visual acuity.

Preliminary Results and Complications of Radial Keratotomy

We preformed radial keratotomy for myopia on 126 eyes of 102 patients. We observed as much as 12 diopters of early postoperative refractive corneal flattening, but a mean of only 5.16 diopters of refractive change can be expected after one year. Among the many complications observed were corneal scarring, an endothelial cell loss of 220 cells/mm2 (6.9%), epithelial ingrowth in 18 eyes (14%), corneal vascularization in one of 126 patients (1%), pain, Cogans corneal dystrophy, overcorrections in 18 patients (14%), anisometropia, perforations of the anterior chamber in 12 patients (10%), iatrogenic astigmatism, corticosteroid glaucoma, night glare in 99 patients (79%), and fluctuating vision in 95 (75%). We studied the following factors to determine if they had predictive value: the patients age, diopters of myopia, corneal diameter, corneal thickness, anterior chamber depth, axial length, scleral rigidity, keratometric readings, and the size of the optical zone. We found that no preoperative factor can be used to estimate precisely the postoperative result. The only consistent variable was the size of the optical zone. The smaller the optical zone, the larger the refractive change. This lack of predictability is the most serious shortcoming of radial keratotomy.

Immunohistologic findings and results of treatment with cyclosporine in ligneous conjunctivitis

Using immunohistochemical techniques, we studied ligneous conjunctival lesions from two patients. A significant immune reaction was detected that was characterized by activated T lymphocytes and focal accumulation of plasma cells and B lymphocytes. Immunofluorescent studies demonstrated that IgG was a prominent component of the amorphous hyaline material seen in these lesions. After previous treatment methods had failed, both patients were treated with excisional biopsy and topical cyclosporine. Patient 1 had a dramatic response, with complete resolution of the lesions. Patient 2 had a significant improvement resulting in small, slow-growing recurrences instead of the rapid and extensive recurrences that occurred before treatment with cyclosporine.

Three-year Results of the Prospective Evaluation of Radial Keratotomy (PERK) Study

The Prospective Evaluation of Radial Keratotomy (PERK) study is a nine-center clinical trial of a standardized technique of radial keratotomy in 435 patients who had simple myopia with a preoperative refractive error between -2.00 and -8.00 diopters (D). We report results for one eye of each patient. The surgical technique consisted of eight incisions using a diamond micrometer knife with the blade length determined by intraoperative ultrasonic pachymetry and the diameter of the central clear zone determined by the preoperative refractive error. At three years after surgery, 58% of eyes had refractive error within one diopter of emmetropia; 26% were undercorrected, and 16% were overcorrected by more than one diopter. Uncorrected visual acuity was 20/40 or better in 76% of eyes. The operation was more effective in eyes with a preoperative refractive error between -2.00 and -4.37 diopters. Between one and three years after surgery, the refractive error changed by 1.00 diopter or more in 12% of eyes, indicating a lack of stability in some eyes.

Radial Keratotomy: Preliminary Report of Complications

We have observed the following complications with radial keratotomy which require further evaluation: missing the visual axis while marking the central cornea, regression of myopic flattening, epithelial defects, recurrent erosions, stromal overgrowth, Cogans map-dot fingerprint corneal dystrophy with Moncreiff iron lines, blood in the incisions, vascular ingrowth, perforation of the anterior chamber, induction of astigmatic errors, epithelial ingrowth, glare complaints and decreased night vision, pain, fluctuating vision from morning to evening, overcorrection and unpredictable results, contact lens refitting difficulties, endothelial cell loss, and corneal scarring. We feel these complications require extensive further study before the relative safety and long-term efficacy of this experimental procedure may be determined.

Ocular Infections Associated With Comamonas acidovorans

Comamonas acidovorans (Pseudomonas acidovorans) is a ubiquitous gram-negative rod. Although generally considered nonpathogenic, we found C. acidovorans to be associated with six cases of ocular infections. The organism was the only isolate in three cases, whereas an association of other organisms was present in three cases. The multiple resistance patterns of these strains to antibiotic susceptibility testing emphasizes the need for culturing ocular infections. We recommend the identification and susceptibility testing of all ocular gram-negative rod isolates.

Intraocular Lens Disasters: Peripheral Anterior Synechia

Peripheral anterior synechia formation appears to complicate intraocular lens use by producing (1) progressive endothelial cell loss, (2) fibrous metaplasia of the endothelium, and (3) angle cicatrization with glaucoma. We present 13 patients with these complications and the anterior segment reconstruction techniques that are necessary to alleviate these relatively late intraocular lens complications.

Photography of Shock Waves During Excimer Laser Ablation of the Cornea: Effect of Helium Gas on Propagation Velocity

Shadow photography of shock waves excited by means of a xenon chloride excimer laser was performed to determine the shock wave propagation velocity in air, nitrogen and helium. Energy densities between 500 and 2,000 mJ/ cm2 were used to ablate a rotating rubber cylindrical target and porcine corneas. In ablating the rubber cylinder, a shock wave velocity of 3.3 km/s was generated in air and nitrogen at 40 ns; this decreased to 1.4 km/s at 320 ns. When helium was blown on the target, the velocity increased by a factor of approximately two, to 5.9 km/s at 40 ns and 2.7 km/s at 320 ns. We suggest that blowing helium on the surface of the cornea during excimer laser ablation may speed the dissipation of high-energy acoustic waves and gaseous particles, and thus reduce the exposure and transfer of heat energy to the surrounding tissue.