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Biomedical subjects

K D Solomon

Publications and source records attributed to K D Solomon.

13 recordsLinked to original sources
PubMed1992

A comparative evaluation of the biostability of a poly (ether urethane) in the intraocular, intramuscular, and subcutaneous environments.

A transparent poly (ether urethane) (PEU) was considered for use as a foldable intraocular lens material. The PEU was found to possess excellent mechanical, optical, and surface characteristics for this application. In vitro hydrolytic and ultraviolet aging studies suggested the PEU to be tolerant to conditions simulating 3-10 years of normal intraocular exposure. Different behavior was obtained, however, from intraocular and subcutaneous implantation of the PEU. After 6 months of intraocular exposure in the feline model, prototype PEU lenses had lost most or all of their optical resolving power. SEM analysis demonstrated scattered pitting and cracking on the lens surfaces. Degradation was found to be more extreme after as little as 30 days of subcutaneous exposure in rabbits. Severe pitting over the entire surface of implanted flat PEU specimens was observed by SEM. Macroscopic examination showed the samples to be frosty in appearance. It was postulated that the subcutaneous implant environment provides an accelerated in vivo model for materials intended for intraocular use. A minimum acceleration of 6-10x was estimated on a preliminary basis. The PEU studied here was found to be unsuitable for use as a foldable intraocular lens material.

Animals↗
PubMed1992

A clinical evaluation of two multifocal soft contact lenses.

We fit two multifocal soft contact lenses, Bausch & Lomb's Bi-Tech and the Unilens contact lens from Unilens Corporation, in two separate populations of presbyopes. Most patients (24/42, 57%) had no prior contact lens experience. Patients were evaluated at 6 and 12 months for comfort, visual acuity, lens fit, and corneal findings. Both distance and near vision were found to be slightly decreased with each contact lens when compared to best corrected visual acuity with spectacles. Seventy-seven percent (14/18) of the Unilens wearers and 67% (16/24) of the Bi-Tech wearers continued to wear their lenses for at least 1 year. Those who discontinued lens wear did so because they were dissatisfied with their vision. Presbyopes who seek correction with soft contact lenses appear to be more tolerant of a decrease in distance vision than a decrease in near vision. Both lenses were comfortable and no corneal pathology was induced. Our results suggest that the Unilens (simultaneous vision design) provides more predictable correction of presbyopic symptoms than the Bi-Tech (alternating vision design) because it is independent of lower lid position and translation. Both of these lenses are viable options for the correction of presbyopic symptoms.

Contact Lenses, Hydrophilic↗
PubMed1989

Protective effect of the anterior lens capsule during extracapsular cataract extraction. Part II. Preliminary results of clinical study.

In a clinical study, 61 patients underwent phacoemulsification with subsequent intraocular lens (IOL) implantation. An intercapsular capsulotomy with phacoemulsification was performed on 23 patients and a can opener capsulotomy with phacoemulsification on 38 patients. Wide-field specular microscopy was performed preoperatively and postoperatively on all of the eyes in the study. The cell counts were not divulged to the surgeon before or at the time of surgery. Average endothelial cell loss for the intercapsular technique was 3.9%; with the can opener technique, the average cell loss was 10.1%. This difference was statistically significant (P less than 0.01). Positive correlations between endothelial cell loss relating to ultrasound time and/or the hardness of the cataract existed for the can opener group only (P less than 0.01). These results demonstrate that a protective effect is provided by the presence of the anterior lens capsule during lens substance removal.

Aged↗
PubMed1989

Protective effect of the anterior lens capsule during extracapsular cataract extraction. Part I. Experimental animal study.

In an experimental study using albino Rex rabbits, the intercapsular cataract extraction (ICCE) technique was performed in 20 eyes with a small anterior capsulotomy. A large, can opener capsulotomy was performed in another 20 eyes, and 10 unoperated eyes served as controls. Endothelial cell loss was determined by vital staining with Trypan blue and Alizarin red S stains. Average endothelial cell loss with the ICCE technique was 1.2%; with the can opener technique, the average cell loss was 6.6%. This difference was statistically significant (P less than 0.01). The percentage of endothelial cell loss in the control eyes was 0.5. A positive correlation between endothelial cell loss related to phacoemulsification time and/or the amount of irrigating fluid used existed for the can opener group only (P less than 0.01). These results demonstrate that the presence of an almost intact anterior lens capsule during removal of lens substance is protective to the corneal endothelium.

Animals↗
PubMed1989

Evaluation of the biocompatibility and fixation of a new silicone intraocular lens in the feline model.

The biocompatibility and fixation of a new silicone intraocular lens was evaluated in the cat eye. Following extracapsular lens extraction, 14 cats were implanted with a silicone lens (SLM 2/UV type) with polypropylene modified J loops in one eye and a poly(methyl methacrylate) (PMMA) lens (Perspex CQ) of a similar design in the fellow eye. Half the lenses were placed in the ciliary sulcus and half in the capsular bag. The eyes were evaluated for up to one year. Neither lens material showed any signs of toxicity clinically or histopathologically. Both lenses achieved stable fixation in the capsular bag; however, some inflammatory reaction and lens dislocation were noted with sulcus placement of both lens types. The amount of proteinaceous and cellular debris on the explanted silicone lenses was significantly less than that on the PMMA lenses as assessed with methylene blue staining. All retrieved lenses were optically clear and no significant change in the lens surface morphology, clarity and/or optical properties was observed.

Animals↗
PubMed1989

[Protective effect of the anterior lens capsule: corneal endothelial cell loss following intercapsular phacoemulsification compared with phacoemulsification with large open capsulotomy].

In an experimental study using rabbits, the intercapsular technique was performed in 20 eyes to make a small anterior capsulotomy. A large, "can opener" capsulotomy was performed in 20 eyes, and ten eyes (five non-operated animals) served as controls. Endothelial cell loss was determined by vital staining with Trypan blue and Alizarin red S. Average endothelial cell loss with the intercapsular technique was 1.2%; with the can opener technique the cell loss was 6.6%. This difference was statistically significant (p less than 0.01). The percentage in the control eyes was 0.05%. Positive relations between endothelial cell loss related to phacoemulsification time and/or the amount of irrigating fluid used existed for the can opener group only (p less than 0.01). These results demonstrate that the presence of an almost intact anterior lens capsule during removal of lens substance is protective to the corneal endothelium.

Animals↗
PubMed1988

Decentration of flexible loop posterior chamber intraocular lenses in a series of 222 postmortem eyes.

Two hundred twenty-two postmortem eyes containing posterior chamber intraocular lenses (IOLs) were analyzed for optic decentration in relationship to lens style, implant duration, and loop fixation site. Decentration values were not affected significantly by either lens style or implant duration. In 33.3% of specimens, both loops were situated within the lens capsular sac, 18.0% had both loops fixated in the ciliary sulcus, and in 48.7% one loop was fixated in the lens capsular sac and the opposite loop in the ciliary sulcus or zonular region. There was a statistically significant difference in the amount of decentration in the three fixation groups studied. Capsular fixation provides the best and most consistent centration compared with fixation of both loops in the ciliary sulcus or asymmetrical fixation with only one loop in the capsular sac.

Ciliary Body↗
PubMed1988

Posterior capsular opacification and intraocular lens decentration. Part I: Comparison of various posterior chamber lens designs implanted in the rabbit model.

Experimental phacoemulsification procedures were performed in 54 Rex rabbits. In 96 eyes, posterior chamber intraocular lenses (IOLs) were implanted in the capsular sac, and 12 eyes served as controls with no lens implantation. The IOLs were divided into eight groups consisting of both one-piece and three-piece styles with various optic designs. Each lens was evaluated for the relative effect on posterior capsular opacification (PCO) and optic decentration, two of the most common complications of modern cataract surgery and IOL implantation. Optics with a convex-anterior, plano-posterior design (the type of IOL optic most frequently implanted today) had the highest incidence of PCO. With capsular fixated IOLs, the features that have a statistically significant impact on reducing PCO include (1) one-piece, all-polymethylmethacrylate (PMMA) IOL styles, (2) a biconvex or posterior convex optic design, and (3) angulated loops. Lens decentration was not affected by the optic design, but statistical analysis showed that one-piece, all-PMMA IOL construction provided the most consistent centration.

Animals↗
PubMed1988

Posterior capsular opacification and intraocular lens decentration. Part II: Experimental findings on a prototype circular intraocular lens design.

In a prospective randomized study, 25 New Zealand white rabbit eyes were implanted with four intraocular lens (IOL) designs. These included a one-piece modified J-loop IOL, a three-piece modified J-loop IOL, a rigid disc IOL, and an experimental compressible disc (CD) IOL. The CD IOL revealed the lowest mean posterior capsular opacification (PCO) of all IOLs tested (P less than .01). With all lenses tested, a positive correlation between PCO and decentration was found (R = 0.55, P less than .05). These results suggest that because of its design features (i.e., one-piece construction, biconvex optic, posterior angulation of the fixation element), the CD lens produces a mechanical barrier against lens epithelial cell migration and reduces the incidence of PCO.

Animals↗
PubMed1987

Transcorneal extrusion of anterior chamber intraocular lenses. A report of three cases.

We examined three cases of transcorneal extrusion of anterior chamber intraocular lenses. In each case a preexisting condition (rheumatoid arthritis, glaucoma, and herpes zoster ophthalmicus, respectively) contributed to corneal necrosis and subsequent extrusion of the pseudophakos. The clinicopathologic correlations of this condition are discussed, as well as some causes of corneal decompensation associated with anterior chamber lenses. We emphasize the need for careful evaluation of patients who have preexisting disease before intraocular lens implantation.

Aged↗
PubMedDate not supplied

Posterior capsule opacification.

A complication of extracapsular cataract extraction with or without posterior chamber intraocular lens (PC-IOL) implantation is posterior capsule opacification. This condition is usually secondary to a proliferation and migration of residual lens epithelial cells. Opacification may be reduced by atraumatic surgery and thorough cortical clean-up. Clinical, pathological and experimental studies have shown that use of hydrodissection, the continuous curvilinear capsulorhexis and specific IOL designs may help reduce the incidence of this complication. Capsular-fixated, one-piece all-polymethylmethacrylate PC-IOLs with a C-shaped loop configuration and a posterior convexity of the optic are effective. Polymethylmethacrylate loops that retain "memory" create a symmetric, radial stretch on the posterior capsule after in-the-bag placement, leading to a more complete contact between the posterior surface of the IOL optic and the taut capsule. This may help form a barrier against central migration of epithelial cells into the visual axis. Various pharmacological and immunological methods are being investigated but conclusive data on these modalities are not yet available.

Cataract↗