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Biomedical subjects

C A Swinger

Publications and source records attributed to C A Swinger.

At least 19 recordsLinked to original sources
PubMed1999

Fitting contact lenses after myopic keratomileusis.

PURPOSE: To evaluate the long-term efficacy and results of contact lens fitting following myopic keratomileusis (MKM). SETTING: Department of Ophthalmology, Manhattan Eye, Ear, and Throat Hospital, and Swinger Vision Center, New York, New York, USA. METHODS: Postoperative fitting of contact lenses was studied as part of a prospective evaluation of myopic keratomileusis. In this series, 27 eyes of 20 patients had residual postoperative refractive errors that were corrected with contact lenses. Patients were fit at a mean of 9.4 months after surgery by the trial-lens method. Preoperative keratometry readings and refractions, as well as postoperative keratometry readings, refractions, and contact lens specifications, were recorded and used for fitting. RESULTS: Twenty-six eyes (96%) were fit successfully: 24 (89%) with rigid gas-permeable lenses and 2 (7%) with daily-wear soft lenses. The mean diameter of the rigid lenses was 10.00 mm (range 9.4 to 11.0 mm) and the mean base curve, 8.52 mm (range 7.9 to 9.2 mm). The 2 soft lenses had base curves of 8.6 and 8.9 mm. The mean lens power was -5.24 diopters (D) (range -0.37 to -14.75 D), which was, on average, 4.06 D more myopic than the postoperative spectacle refraction. Postoperative keratometry provided a good starting point for the trial lens. Lenses were tolerated for up to 16 years. One eye, fit with a soft lens, developed significant myopia during the fifth year. CONCLUSION: After lamellar refractive surgery, the topography of the cornea is significantly altered. Although the postoperative keratometry readings are steeper than the actual curvature, they are reasonably reliable for determining the base curve of the initial trial lens, validating the use of conventional methods of fitting rigid contact lenses in patients who have had MKM.

Adolescent↗
PubMed1996

Reproducibility of videokeratographic digital subtraction maps after excimer laser photorefractive keratectomy.

BACKGROUND: Digital subtraction photokeratography can best identify topographic changes after excimer laser photorefractive keratectomy (PRK). To evaluate the reproducibility of these topographic maps, the authors used a topographic modeling system to generate multiple subtraction maps from different combinations of technically acceptable preoperative and postoperative maps for eyes that underwent PRK. The assigned patterns for each patient then were evaluated for consistency. METHODS: Seven hundred twenty-two individual subtraction maps were generated for 64 eyes that underwent PRK. A mean of 11.3 maps were generated for each eye. The topography of each map was individually classified as normal, central island, peninsula, or asymmetric. All maps within a set (consisting of examinations for 1 patient at a single postoperative interval) then were examined as a unit to determine the overall topographic classification for that set of maps. Each set in which each constituent map had the same topographic assignment as the set was considered "nonvariant," whereas those sets in which one or more individual subtraction maps had different topographic assignments were considered "variant." RESULTS: Of the 64 sets, 33 (52%) were variant and 31 (48%) were nonvariant. CONCLUSIONS: Any one subtraction map produced by the topographic modeling system may not be a reliable indicator of the excimer effect.

Cornea↗
PubMed1987

Nonfreeze epikeratophakia for the correction of myopia.

We developed a procedure for preparing epikeratophakia tissue lenses for the correction of myopia from unfrozen tissue using a newly developed artificial anterior chamber and the BKS-1000 (Barraquer-Krumeich-Swinger) refractive set. The results of 23 clinical cases involving tissue that was not frozen or lyophilized demonstrate a correlation coefficient of 0.90 in terms of accuracy of correction and good visual acuity results.

Adult↗
PubMed1987

Keratophakia--postoperative astigmatism.

Forty-nine cases of primary keratophakia and 13 cases of secondary keratophakia were analyzed for postoperative astigmatism. For primary cases, the surgically induced astigmatism was 1.55 D, whereas for secondary cases it was 0.19 D (insignificant). There was a tendency for both procedures to induce against-the-rule astigmatism, and both procedures were found capable of producing irregular astigmatism.

Astigmatism↗
PubMed1986

Epithelial ion transport in rabbit corneas following myopic keratomileusis.

In isolated rabbit corneas that had undergone lamellar keratectomy or myopic keratomileusis, the stimulation of chloride transport by 10(-5) M epinephrine was completely inhibited at 1 week following surgery. At 28 days following surgery, both groups responded to 10(-7) M epinephrine. The response to 10(-5) M amphotericin B was normal both at 1 week and at 28 days following surgery. We conclude that, although the Na-K pump was not affected by the lamellar keratectomy and cryolathing, that either the epithelial beta receptors and/or the cAMP pathway were temporarily inhibited for at least 1 week following surgery. A lamellar keratectomy, therefore, can have an adverse effect on the epithelial transport system of the corneal epithelium even though the epithelium may appear normal clinically.

Amphotericin B↗
PubMed1986

A corneal mold to restore normal corneal dimensions.

A corneal mold is described that provides an MK corneal button of normal thickness and curvature from an edematous, post-mortem button. The uniform, processed tissue can then be used for experimental refractive surgery.

Cornea↗
PubMed1985

Dehydration of post-mortem eyes for practice and experimental surgery.

A technique has been developed that allows for rapid dehydration of the cornea of an intact globe. This technique results in a marked improvement in corneal clarity and visualization of anterior chamber structures. Treated eyes can be used for practice and experimental surgery.

Animals↗
PubMed1985

Retinal evaluation and treatment after refractive corneal surgery.

Refractive corneal surgery (a collective term used to describe a variety of surgical procedures that alter the refractive status of the eye through the surgical modification of corneal curvature) shows promise for use in situations where current methods of optical correction do not meet the patient's needs. This article reviews our experiences with the retinal evaluation of patients who have undergone corneal refractive surgery and offers recommendations for the treatment of retinal pathology after such surgery.

Cornea↗
PubMed1984

Prospective evaluation of myopic keratomileusis.

The initial results of a prospective evaluation of myopic keratomileusis are reported. The procedure was attempted on 42 eyes, with an average follow-up of 10 months. The average reductions of myopia were 7.05 D and 11.59 D when measured by keratometry and refraction, respectively. Regular astigmatism increased by 0.50 D on keratometry, but there was no change in the refractive cylinder. The majority of patients had some irregular astigmatism on corneoscopy. The average percent correction, based on refraction, was 94.1 +/- 24%, and the correlation coefficient was 0.43. Visual rehabilitation was rapid. No patient followed for 1 year or more had a decrease in the best-corrected acuity, and 63% of this group had an average improvement of 1.5 lines with as much as five lines. The final refraction may take up to 6 months to stabilize. Complications consisted of epithelium and debris in the interface and focal necrosis of Bowman's membrane. The technique is difficult but may have application in the visual rehabilitation of the high myope.

Adolescent↗
PubMed1984

Selective positioning of the donor cornea in penetrating keratoplasty for keratoconus: postoperative astigmatism.

The final "sutures-out" astigmatism in patients who had undergone penetrating keratoplasty for keratoconus was evaluated for two groups of patients. Group 1 consisted of patients operated upon using the Troutman surgical keratometer but without giving attention to the orientation of the donor button in the recipient bed. Patients in Group 2 were also operated upon utilizing the surgical keratometer, but the donor button was rotated in the recipient bed until a position of apparent sphericity was indicated by the keratometer before suturing the graft. The mean final astigmatism was 4.42 +/- 1.85 D for Group 1 and 5.13 +/- 3.17 D for Group 2. The difference was not statistically significant. The results indicate that selective positioning of the donor button in an attempt to minimize astigmatism, as determined with a qualitative surgical keratometer, does not lead to a reduction in the final astigmatic error in patients undergoing penetrating keratoplasty for keratoconus.

Adult↗
PubMed1983

Comparison of results obtained with keratophakia, hypermetropic keratomileusis, intraocular lens implantation, and extended-wear contact lenses.

The limited experience with LRK precludes a valid comparison with IOLs and extended-wear contact lenses. Only observations, unsupported by valid statistical analysis, are possible. Some of these observations follow. Technically, LRK is very difficult. In their present form, the classic Barraquer procedures could never be used widely. However, if lenticle banks were to supply preground lenticles, the level of difficulty of LRK procedures would be comparable to IOL implantation. The magnitude of refractive correction possible with LRK compares favorably with that of contact lenses and IOLs. However, the accuracy of achieving a given correction is lower with LRK. Unlike contact lenses or IOLs, LRK induces both regular and irregular astigmatism. The latter accounts, in part, for the delayed visual result with LRK. The percentage of patients with 20/40 or better vision following LRK compares favorably with the percentages for contact lenses or IOLs, whereas the percentage of patients with 20/25 or better vision does not. This is true for at least 1 year following surgery. Compared to extended-wear contact lenses, IOLs and LRK typically require less commitment, fewer postoperative visits, and less expenditure by the patient, in terms of time and money, to achieve full-time correction. Although LRK is associated with a number of postoperative complications, none are known to be intraocular, and there have been no known reports of permanent severe visual loss. In contrast, the patient with an extended-wear contact lens or IOL is permanently at risk to develop sight-threatening complications. This is not the case with LRK, which has no known complications after the early postoperative period. Application of the IOL or extended-wear contact lens to the neonate or pediatric patient is associated with increased risk and difficulty. This may not be true with LRK, especially epikeratophakia. The major advantages of LRK appear to be permanent optical correction without the threat of intraocular or long-term complications and the ability to correct contact lens failures without the necessity of reentering the eye. Its major disadvantage is a slightly reduced visual acuity with delayed visual result. Extended-wear contact lenses, IOLs, and LRK are each unique enough that they should be adjuncts to one another. These corrective modalities should be applied judiciously by the patient-surgeon team to the best advantage of the given patient.

Aphakia, Postcataract↗
PubMed1981

Ultrastructure of human lenticles in keratophakia.

Three patients experienced technical failures from their keratophakia procedures and their lenticles were removed at intervals of three days, 2 1/2 months, and nine months, respectively, postoperatively. All three lenticles displayed, by both light and electron microscopy, degeneration of their keratocytes without any evidence of repopulation by the host's keratocytes. Small increases in amorphous material were noted between the collagen fibrils, but the stromal lamellae were otherwise well preserved and oriented. There was not clear evidence of new collagen production at the edges of the lenticles. One failure was caused by the mistaken inclusion of Descemet's membrane in the lenticle. Another specimen with epithelial ingrowth also displayed degeneration of the collagen fibrils along one edge; this degeneration was possibly the result of collagenase activity.

Adult↗