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Biomedical subjects

J J Rowsey

Publications and source records attributed to J J Rowsey.

At least 55 records · Page 3Linked to original sources
PubMed1986

Late development of ulcerative keratitis in radial keratotomy scars.

We describe three patients in whom ulcerative keratitis developed seven months to 2 1/2 years after uncomplicated radial keratotomy. All ulcers occurred along keratotomy scars within the interpalpebral fissure or inferiorly. At least one case developed spontaneously; another patient may have sustained an unrecognized corneal injury. The third patient was using an extended-wear soft contact lens for correction of residual myopia. Bacteria were isolated from two of the ulcers. With therapy, all ulcers healed without reducing visual acuity. We hypothesize that the altered structure of the slowly healing keratotomy incisions coupled with redistribution of the tear film due to changes in corneal topography may result in intermittent epithelial irregularities. Alone or in conjunction with any form of mechanical or hypoxic corneal injury, these changes along keratotomy incisions may predispose to corneal infection.

Adult↗
PubMed1986

Dynamic shifts in corneal topography during the modified Ruiz procedure for astigmatism.

We utilized ten eye bank eyes to evaluate and quantitate the immediate corneal topographic shifts that occur after each stage of a modified Ruiz procedure for astigmatism. Computer digitization of photokeratoscope (Corneascope) photographs revealed that the initial two central paired tangential incisions induced an average of 5.10 diopters (D) of central astigmatism by flattening the meridian perpendicular to the incisions and by steepening the meridian 90 degrees away. Additional tangential incisions did not significantly alter the topography after placement of the first two central incisions. Addition of corridor incisions produced an additional 5.25 D of induced astigmatism by further extensive flattening of the incised meridian. The completed procedure produced an average of 11.03 D of astigmatic shift, but with a wide range of effect (7.15 to 12.96 D). With modification, the Ruiz procedure is a powerful keratorefractive surgical technique.

Astigmatism↗
PubMed1985

A study of optical zone size and incision redeepening in experimental radial keratotomy.

The effects of optical clear zone size and incision redeepening following four- and eight-incision radial keratotomy were studied in a series of human cadaver eyes. Keratometry was measured with both the Terry keratometer and corneascope photographs. After eight incisions, induced corneal flattening for each clear zone (Terry keratometry readings) was 3.0 mm, 9.06 diopters; 4.0 mm, 6.44 D; 5.0 mm, 5.23 D; and 6.0 mm, 2.29 D. Differences were statistically significant, except for the 4.0-mm and 5.0-mm zones. Induced corneal flattening following eight incisions (corneoscopy) was 3.0 mm, 9.83 D; 4.0 mm, 8.87 D; 5.0 mm, 6.04 D; and 6.0 mm, 2.59 D. Differences were statistically significant, except for the 3.0-mm and 4.0-mm zones. Peripheral redeepening of the incisions did not significantly increase the amount of corneal flattening for any optical zone, as measured by the Terry keratometer. However, the 3.0-mm optical zone flattened an additional 1.23 D after the redeepening incisions, as measured by corneoscopy. The redeepening incisions were complicated by perforations in 38% of the eyes. Titrating the effect of radial keratotomy by varying the size of the optical zone appears to be valid, but the value of peripheral redeepening in the acute laboratory situation is not supported by these data.

Cornea↗
PubMed1985

Relaxing incisions. Corneal topography.

The topography of circumferential corneal relaxing incisions in eye bank eyes was studied using the corneascope. Significant flattening in the meridian perpendicular to the corneal relaxing incision was found with steepening 90 degrees away in a ratio of two diopters of flattening to one diopter of steepening. This study demonstrates the range of change in corneal astigmatism from 0.58 D for a single one clock hour incision to 5.93 D for a unilateral three clock hour incision. This is compared to symmetrical relaxing incisions placed 180 degrees apart which produce 0.78 D of astigmatic change for one clock hour incisions, and 13.97 D of change for symmetrical three clock hour incisions. The larger shifts in corneal power were also associated with a small degree of central corneal flattening or decreased corneal power.

Astigmatism↗
PubMed1985

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.

Adult↗
PubMed1984

Refractive reconstruction for acute eye injuries.

Acute tissue repair from corneal trauma requires an understanding of basic corneal topography shifts in keratorefractive surgery. Avoiding astigmatism at the time of the initial repair is propitious, but may not be accomplished even with a careful understanding of the vector forces of suture material when tissue is lost from the cornea. Subsequent wound revision, tissue replacement, relaxing incisions or penetrating keratoplasty may be necessary.

Animals↗
PubMed1984

Model of epithelial downgrowth: II. Scanning and transmission electron microscopy of corneal epithelialization.

We present a cat model of prolific epithelial downgrowth reviewing the scanning and transmission electron microscopy data. The cat model of posterior corneal epithelialization closely mimics the human clinical condition in the following areas: uneven epithelial spread over the endothelial surface on scanning electron microscopy, prominence of intercellular desmosomes and hemidesmosomes, and attachment of the latter to a basement membrane overlying a newly formed posterior collagenous layer. Cell layering is attenuated during the centripetal spread of cells down the center of the cornea. Adjacent endothelial cells show signs of cytotoxicity by increased microvilli and eventual plasma membrane retraction. Endothelial cells are covered by the advancing epithelium with subsequent endothelial cell death. The density of subepithelial collagen attachments would suggest that removal of Descemet's membrane would be required to guarantee total epithelial cell removal.

Animals↗
PubMed1984

Diamond knife corneal incisions.

In the following study, eight linear corneal incisions were made in two human cadaver eyes with three diamond-bladed knives: the KOI, Cooper, and Micra micrometer knives. Prior to the incisions, ultrasonic pachymetry readings of the corneas were recorded, and all knives were calibrated to a guarded cutting depth of 0.55 mm (550 microns). Following the incisions, the corneas were fixed, sectioned, and incision depth carefully measured histologically. In all but two incisions made with the Cooper knife, the incision depth was significantly or highly significantly greater than the calibrated diamond length. There was a significant or highly significant difference in depth among incisions made with the same knife, as well as among incisions made with different knives. Depth variability was noted for all knives except for two comparisons between incisions made with a Micra and KOI knife, and one comparison between two incisions, both made with the Cooper knife. Difference in knife design which may account for the variation of incision depth and contribute to the unpredictability of radial keratotomy is discussed.

Cadaver↗
PubMed1983

Predicting the results of radial keratotomy.

Radial keratotomy on 251 patient eyes was performed. Patients traversing the one-year gate after surgery have demonstrated a refractive change best predicted by the optical zone size, the number of incisions, the corneal dissymmetry, and the age of the patient. One year after surgery, a 16-incision radial keratotomy with 3.0-mm optical zone produced 4.66 diopters of refractive change if the limbus was traversed (N = 13), and 5.18 diopters of refractive change if all incisions remained in clear cornea (N = 39). An eight-incision, 3.0-mm optical zone radial keratotomy produced 5.21 diopters of refractive change at one year (N = 37). A 3.5-mm optical zone, eight-incision radial keratotomy produced 3.66 diopters of change at one year (N = 6). A 4.0-mm optical zone produced 2.67 diopters of change with 16 incisions (N = 8), and 3.45 diopters of change with eight incisions at one year (N = 9). Although older patients appear to have significantly greater refractive change with radial keratotomy at the three-month gate, this difference is not yet confirmed at one year after surgery. The shape of the cornea before surgery contributes to the predictability of the refractive results when the horizontal and vertical keratometer measurements are analyzed. Corneal dissymmetry produces greater refractive results with steeper horizontal K when against-the-rule astigmatism is present before surgery.

Adult↗
PubMed1983

New corneal shapes in keratorefractive surgery.

The corneal shape change as measured by the Humphrey keratometer and the corneascope after radial keratotomy in 50 patients was compared. The Humphrey keratometer analyzes a unique curve fit algorithm of the aplanatic corneal surface and designates this comparison as a shape factor. Both the corneascope photographs and the Humphrey keratometer demonstrated central corneal flattening after successful radial keratotomy. In addition, the normal "plus" shape factor was routinely converted to a "negative" shape factor after the procedure. This is analogous to converting the aplanatic central cornea, which normally approximates the end of an ellipse, to a topography which appears in cross section as the side of an ellipse. This alteration in topography is directly correlated to the magnitude of cycloplegic refractive change seen with this operation. The corneascope map topography of the cornea confirms this alteration in curvature.

Cornea↗
PubMed1983

Ten caveats in keratorefractive surgery.

Topographic shifts in the cornea are associated with refractive changes as follows: (1) The normal cornea flattens over any incision. (2) Radial incisions flatten the adjacent cornea and the cornea 90 degrees away. (3) The cornea flattening effect increases as incisions approach the visual axis. (4) The cornea flattens directly over any sutured incision. (5) The cornea flattens adjacent to loose sutures and flattens 180 degrees away, and steepens 90 degrees away. (6) The cornea steepens adjacent to tight sutures and steepens 180 degrees away, and flattens 90 degrees away. (7) The cornea flattens over wedge resection or tucks. (8) The cornea steepens anterior to wedge resections or tucks. (9) Tissue removal produces corneal flattening over the site of tissue removal, whether traumatic or surgically induced. (10) Full-thickness corneal tissue addition produces corneal steepening over the site of the tissue addition and flattens the adjacent cornea.

Cornea↗
PubMed1983

Rationale for and design of the National Eye Institute Prospective Evaluation of Radial Keratotomy (PERK) Study.

A five-year, multicenter, collaborative clinical trial of radial keratotomy for myopia is being carried out at nine clinical centers. The study, funded by the National Eye Institute, is recruiting approximately 500 patients aged 21 years or older with -2.00 to -8.00 diopters of physiologic myopia who also meet other clearly defined eligibility criteria. Surgeons use a diamond-bladed micrometer knife to make eight radial incisions in the anterior cornea. The diameter of the central clear zone is determined by the amount of myopia and the depth of the incisions by intraoperative ultrasonic pachymetry. Investigators other than the surgeon gather all pre- and post-operative data. Examinations include measurement of visual acuity with standardized charts, verification of refractions by a second observer, measurement of corneal curvature by keratometry and photokeratoscopy, quantitation of glare with a glare tester, and measurement of the size of individual endothelial cells from specular photomicrographs with a computerized digitizer. A formal psychometric questionnaire is used to evaluate the patients' subjective response. Physician monitors insure adherence to the protocol during site visits and members of the Data and Safety Monitoring Board oversee the progress of the study. Biostatisticians at the Coordinating Center insure complete data collection, process the data, and assist in the interpretation of results.

Academies and Institutes↗
PubMed1982

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, Cogan's 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 patient's 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.

Adolescent↗
PubMed1982

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.

Adult↗
PubMed1982

Diamond knife.

We present a new diamond knife which allows for reasonably precise incisions in cornea or sclera. The knife may be ultrasonically cleaned and is sharper than any metal knife whose edge we have examined to date by scanning electron microscopy. The edge is approximately 0.1 micron in width, compared to 1-5 micron width edges of most metal knives. We feel that this prototype will allow investigators to recommend special modifications to the manufacturer of their own choice.

Carbon↗