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Biomedical subjects

D J Apple

Publications and source records attributed to D J Apple.

At least 145 records · Page 8Linked to original sources
PubMed1992

Scanning electron microscopic study of modern silicone intraocular lenses.

Silicone, as manufactured today, appears to be a biocompatible material. The safety and efficacy of silicone lenses are primarily related to the intraocular lens (IOL) design. We compared the edge finish of two three-piece polypropylene loop foldable silicone IOL designs (Allergan Medical Optics) and three one-piece designs (Staar Surgical Co., CooperVision-Cilco). Except for an early Staar one-piece design, all lenses including the more recent Staar lenses had acceptably smooth edges with minimal molding flash.

Biocompatible Materials↗
PubMed1992

Variations in manufacturing quality of diffractive multifocal lenses.

The new generation of multifocal intraocular lenses (IOLs) based on diffraction optics is characterized by a stepped discontinuity at zone boundaries on the posterior surface of the IOL optic. The step height at the zone boundaries is less than 2 microns. There are approximately 30 zones on a 6 mm diameter lens, requiring manufacturing precision of about 0.02 mm. Various companies produce this type of lens. On two implanted lenses we found, in addition to the 2 microns boundaries, many small circular rims that appeared to be manufacturing artifacts. The presence of these artifacts may explain the variable clinical acceptance of these IOLs.

Aged↗
PubMed1992

The effect of varying wavelength on subconjunctival scleral laser suture lysis in rabbits.

We studied laser suture lysis of subconjunctival scleral sutures in a rabbit eye using selected wavelengths from a dye and diode laser to determine which wavelength caused the least conjunctival damage. We found an oval shaped area of coagulation necrosis surrounding the suture track in the conjunctival substantia propria measuring in depth 61.0 mu for 488 + 514 nm (blue-green), 105.7 mu for 514 nm (green), 148.3 mu for 630 nm (red), and 29.0 mu with 780 + 830 nm (infrared) wavelengths. No observable damage was noted with 585 nm (yellow) or 610 nm (orange) wavelengths. The energy intensity required for suture lysis was similar across each wavelength studied. No damage was observed in the sclera or conjunctival epithelium. These findings suggest that using the yellow or orange wavelength, when performing laser suture lysis clinically, potentially may limit conjunctival damage.

Animals↗
PubMed1992

[Comparison of various capsulectomy techniques in cataract surgery. An experimental study].

Radial tears at the edge of an anterior capsulectomy are often associated with the occurrence of intraocular lens (IOL) loops coming out of the capsular bag with subsequent IOL decentration. We analyzed the incidence of radial tear formation in 40 human eyes obtained postmortem. These eyes were randomly assigned to four groups: "can opener," linear capsulotomy, capsulopuncture ("postage stamp"), and continuous curvilinear capsulorhexis (CCC). The CCC appeared to be much less likely to be associated with anterior capsular radial tears as opposed to the other three techniques. With the nucleus expression technique used in this study, radial tears occurred in all cases of "can opener," linear capsulotomy and capsulopuncture, whereas no tears occurred with the CCC technique. The results of this study show that CCC is currently the best available anterior capsulectomy procedure for minimizing the incidence of radial tears and sequelae such as decentration.

Aged↗
PubMed1992

[Implantation of IOLs with different diameters].

The intraocular lenses (IOLs) commonly used today are 13.5 to 14 mm in diameter, and this diameter is considered by some to be unnecessarily large. The size of the crystalline lens and the diagonal width between the ciliary sulcus were measured in rabbit eyes and human eyes. Then, IOLs with a smaller diameter (12.5 mm) were evaluated after implantation into rabbit eyes. The mean diameter of the human crystalline lens was 9.6 mm and its thickness was 4.1 mm. The mean width of the ciliary sulcus was 11.1 mm. The crystalline lenses of rabbits were larger than those of humans. Decentration and posterior capsular opacification score were 0.33 mm and 0.63 in 12.5 mm IOL, and 0.47 mm and 0.61 in 14.0 mm IOL. Indicating that the result of implanting the 12.5 mm IOL was not inferior to that of implanting the conventional 14 mm IOL. The average width of the ciliary sulcus is 11.1 mm, indicating that a 12.5 mm IOL is of a sufficient size to be firmly fixed in this sulcus. In addition, a 12.5 mm IOL is considered to be safer, because larger lenses may lead to erosion or vessel compression that could induce ischemia or neovascularization.

Animals↗
PubMed1992

Histologic differences in the conjunctiva of black and white glaucoma patients.

We compared perioperative conjunctival biopsy specimens from 31 consecutive trabeculectomy patients to determine if there were any histologic differences between black and white glaucoma patients. We found a statistically significantly greater mean and distribution of mast cells and neutrophils in the white patients. No significant difference was found in the mean number of goblet cells, eosinophiles, macrophages, fibroblasts, plasma cells, or lymphocytes; or in thickness of the epithelium, vascular density, or collagen or mucopolysaccharide staining. We conclude that histological conjunctival factors that could be evaluated preoperatively probably are not related to the poor results in black patients of filtration surgery noted by some investigators.

Aged↗
PubMed1991

The elastic properties of the lens capsule in capsulorhexis.

We investigated the ability of the anterior lens capsule to stretch and allow removal of lens substance and intraocular lens implantation through a continuous circular capsulorhexis. Capsulorhexis of various sizes (2.5 to 7.5 mm) were performed in 50 eyes obtained post mortem from 31 patients. The nucleus and cortex were removed by either phacoemulsification (35 eyes) or manual extracapsular cataract extraction (15 eyes). The opening of the capsule was then gradually enlarged, using a modified caliper with two pins attached to its tips, until the margins were torn. The capsule was torn when the circumference at the time of rupture was 1.6 times larger than the circumference of the original circular capsulectomy or 5.0 times larger than the diameter of the capsulectomy. Manual extraction of a lens nucleus with profile circumference (sagittal or anteroposterior) of 18.0 to 22.0 mm can be performed through a 5.5-mm opening and a 6.0- to 7.0-mm optic intraocular lens (profile circumference of 13.0 to 17.0 mm) can be implanted through a 4.5-mm capsulectomy.

Aged↗
PubMed1991

An experimental study comparing various anterior capsulectomy techniques.

Radial tears at the margin of an anterior capsulectomy may be associated with the exit of at least one loop of an intraocular lens out of the capsular bag ("pea pod" effect) and subsequent decentration. Many ophthalmologists have gained a clinical impression that the anterior capsule is more likely to remain intact if the continuous circular capsulorhexis (CCC) technique is used. However, controlled comparison of the incidence of radial tears with the use of different capsulectomies under standardized conditions has not been performed, to date. In this study, we analyzed the incidence of radial tear formation in 40 human eyes that were obtained post mortem. These eyes were randomized to four technique groups: (1) "can opener," (2) linear capsulotomy, (3) capsulopuncture, and (4) CCC. We demonstrated that the CCC technique is much less likely to cause or be associated with anterior capsular radial tears as opposed to the other three techniques. With the technique of nuclear expression used in this study, radial tears occurred in 100% of cases treated with the can opener, linear capsulotomy, and capsulopuncture techniques, whereas no tears occurred with the CCC technique. This study provides convincing evidence that the CCC is the best available anterior capsulectomy procedure to minimize the incidence of radial tears.

Aged↗
PubMed1991

Carcinoma arising in an odontogenic keratocyst with orbital invasion.

A 54-year-old black female presented with proptosis and reduced visual acuity of the left eye. Computerized tomography (CT) revealed tumor involvement of the left cavernous sinus and posterior orbit. The patient had a nineteen year history of a left-sided jaw tumor which recurred despite surgical and radiation therapy. Biopsy demonstrated a parakeratinized odontogenic keratocyst with areas of transformation into an invasive squamous cell carcinoma. Although a parakeratinized odontogenic keratocyst may be locally invasive, to our knowledge, no case of a parakeratinized odontogenic keratocyst involving the orbit or cavernous sinus previously has been reported.

Carcinoma, Squamous Cell↗
PubMed1991

Mechanism of radial tear formation and extension after anterior capsulectomy.

The mechanisms of anterior capsular radial tear formation and extension around the equator onto the posterior capsule were investigated in 57 eyes obtained postmortem. Experimental radial tears were created by gradual opening of a caliper. In 95% of cases, the tear immediately reached the equator but none extended to the posterior capsule. The elastic forces of the zonules attached to or crossing the edges of the tear resisted a widening of the gap between the edges and thus limited the radial progression of the rupture. A significantly stronger force and severing of the zonules were necessary for a tear to extend around the equator. The authors have determined that radial tears in the anterior capsule seldom extend around the equator, providing the zonules bridging the tear are intact. There is a diminution of the tearing force when the flaps are widely open. Careful surgery with preservation of the integrity of the capsular-zonular apparatus is a major factor in preventing major complications such as posterior capsular ruptures.

Aged↗
PubMed1991

Anterior capsular tears and loop fixation of posterior chamber intraocular lenses.

Two hundred fifty consecutive postmortem eyes containing posterior chamber intraocular lenses (PC IOLs) were analyzed according to the presence and number of radial anterior capsular tears. Over 90% of cases had been done with the "can opener" technique. A surprisingly high percentage of cases, 86%, had one to five radial tears. Furthermore, our analysis showed that the most consistent and most permanent in-the-bag fixation was achieved when only one tear or less was present in the anterior capsule. Because this study shows that the incidence of radial tears is very high after nuclear expression with "can opener" capsulectomy, it provides a scientific basis supporting the transition toward the continuous circular capsulorhexis technique that is slowly evolving. The latter technique has been shown to minimize the incidence of anterior capsular radial tears. This may ultimately serve to decrease the incidence of PC IOL decentration, an important goal if the use of bimultifocal IOLs and IOLs with small or aspheric optics is to be successful.

Aged↗
PubMed1991

An analysis of flexible anterior chamber lenses with special reference to the normalized rate of lens explantation.

A survey of 1204 closed-loop anterior chamber intraocular lenses (AC-IOLs) and 310 open-loop AC-IOLs accessioned between November 1982 and January 1990 was conducted at the Center for Intraocular Lens Research. An analysis of complication rates was done after normalization of data with respect to market share totals. The results establish that an unacceptable complication rate is associated with the closed-loop design when compared with either the tripod or quadripod lens styles. Furthermore, the closed-loop designs, while comprising an estimated 45% of the total number of AC-IOLs estimated to be implanted in the United States (n = 674,000), were responsible for 80% of the AC-IOLs explanted after complications and accessioned at the authors' center. A rethinking of the extreme condemnation of all anterior chamber IOLs that has surfaced in recent years is warranted. This is particularly true with respect to indications for use of sutured posterior chamber (PC) IOLs as well as with regard to possible use of open-loop AC-IOLs in less-industrialized nations.

Anterior Chamber↗
PubMed1991

Transscleral cyclophotocoagulation using a semiconductor diode laser in cadaver eyes.

We studied the effectiveness of semiconductor diode laser transscleral cyclophotocoagulation in cadaver eyes using the Miyake technique and light microscopy. Thermal lesions in the ciliary processes were induced with 0.7-second, 1200-mW, and 100- to 500-microns applications, 0.5 mm from the surgical limbus and defocused 1 mm posteriorly. An effective ciliary body reaction was observed grossly as tissue blanching, shrinkage, and pigment dispersion; and histologically, as coagulation necrosis and epithelial cell disruption. No damage to crystalline or intraocular lenses was evident. This successful application of diode laser transscleral cyclophotocoagulation in cadaver eyes suggests that it may prove useful in treating patients with glaucoma.

Ciliary Body↗
PubMed1991

A comparison of neodymium: yttrium aluminum garnet and diode laser transscleral cyclophotocoagulation and cyclocryotherapy.

The cyclodestructive effects of cyclocryotherapy and of the neodymium:yttrium aluminum garnet (Nd:YAG) and diode laser transscleral cyclophotocoagulation were investigated in phakic and pseudophakic cadaver eyes using a modified Miyake posterior-view technique and light microscopy. Cyclocryotherapy to -80 degrees C was applied with a 2.5-mm diameter tip, 1 and 2 mm from the limbus. Freezing at the ciliary processes was evident after 10-15 sec and reached a diameter of 3-4 mm by 30 sec. No visible changes were evident grossly in the ciliary processes, crystalline lens, or intraocular lens. Histologically increased separation of cells was observed. Effective noncontact Nd:YAG and diode laser applications to the ciliary processes were observed grossly as tissue blanching and shrinking and pigment dispersion. This effect was obtained by aiming 0.5-1.0 mm behind the limbus at a 1-mm defocus using 4 J of energy for the Nd:YAG and 1.2 J for the diode laser. The diode laser spot size did not affect the tissue response. No damage was observed in the crystalline or intraocular lens with either type of laser. Histologic changes using both lasers were coagulation necrosis with fragmentation and detachment of the ciliary body epithelium. This study suggested that the gross and histologic thermal effects produced by the diode and Nd:YAG laser were similar in the ciliary body. Also, at the time of surgery, these cyclodestructive procedures potentially cause little alteration of the crystalline or intraocular lens.

Ciliary Body↗