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D J Apple

Publications and source records attributed to D J Apple.

At least 109 records · Page 6Linked to original sources
PubMed1996

[Suitability of polyvinylpyrrolidone (PVP) as a substance for hydrogel intraocular lenses].

UNLABELLED: Conventional PMMA intraocular lenses (IOLs) have been shown to restore vision successfully after cataract surgery, but have been associated with complications such as decentration, destruction of intraocular tissue, and posterior capsule opacification. Expansile IOLs based on cross-inked polyhydroxyethylmethacrylate (PHEMA) also undergo chemically induced hydrolysis, polymer leaching and gel fragmentation. The focus of this research is to prepare and characterize hydrogel IOLs prepared from PVP using gamma-irradiation. METHODS: Hydrogels were prepared from aqueous solutions of PVP by free radical polymerization as a function of gamma-irradiation dose (0.5 x 106 to 2.5 x 106 rad), PVP concentration (4% to 16% w/v), molecular weight (MW) (10 x 103 to 360 x 103 Da), and blending with low and high MW PVP. Viscometric analysis, swelling characterization studies, and polymer leaching studies were carried out to access network formation. In addition changes in lens geometry in an animal model were measured in response to cycloplegic eyedrops. RESULTS: Cross-linking efficiency was greatest with an initial MW of 360 x 103 Da and lowest with an initial MW of 10 x 103 Da. The time to reach equilibrium from the glassy state and the degree of swelling in saline decreased with increasing gamma-irradiation dose and increased with concentration of PVP and blending of low and high MW PVP. The equilibrium water content ranged from 90 to 98% (w/w). Eighty-five percent of the equilibrium dimensions could be achieved within 90 min. Gravimetric analysis and HPLC indicate that the amount of PVP that is not incorporated into the network ranges from 0.25% to 6% (w/w). This was inversely related to the gamma-irradiation dose. The MW of the leached samples was estimated to be greater than 10 x 103 Da in all cases. CONCLUSIONS: PVP hydrogel IOLs prepared by gamma-irradiation have advantages in terms of chemical stability, high water content, and ease of preparation. They may not need further purification or sterilization prior to implantation. In addition, they may allow for accommodation. No comments can be made regarding the biocompatibility, long-term stability, or optical quality at this time.

Animals↗
PubMed1995

The capsular bag after short- and long-term fixation of intraocular lenses.

PURPOSE: To investigate the effect of posterior chamber intraocular lens (PC IOL) size and construction on the capsular bag in human cadaver eyes. METHODS: Studies were done at two timeframes: (1) short term (prospective)--the effect of 12 different IOLs on the capsular bag configuration after experimental implantation; and (2) long term--(retrospective) analysis of eyes with PC IOLs obtained post-morterm. RESULTS: The short-term study showed the maximal diameter of the capsular bag to be 11.0 mm for IOLs with total diameter of 12.0 mm and 11.5 mm for 13.5- to 14.0-mm IOLs. Longer IOLs caused more ovaling of the bag with stress lines (striae) on the posterior capsule. Secondary processes such as proliferation of epithelial cells (Soemmering ring) and capsular fibrosis caused the capsular bag to resume a more circular shape with irregular contour. The area of contact between the IOL loops and the capsular equator was significantly lower in eyes with radial tears and IOLs with the J-loop design compared with the C-loop design. In both the short- and long-term groups, maximal capsular diameter did not exceed 12.0 mm. CONCLUSIONS: The results of this study suggest that using the capsulorrhexis technique, a 12.0-mm total diameter IOL is sufficient to provide stable capsular fixation.

Aged↗
PubMed1995

Analysis of 100 explanted one-piece and three-piece silicone intraocular lenses.

PURPOSE: The authors analyzed incidence and types of complications seen after implantation of silicone posterior chamber intraocular lenses (PC IOLs). These data were compared with those obtained in previous studies with standard polymethylmethacrylate IOLs. METHODS: Data from the laboratory database were collected on 100 explanted silicone IOLs submitted to the Center for Intraocular Lens Research from 1986 to 1994. RESULTS: Of the 100 IOLs, 63 were three-piece designs with polypropylene loops and 37 were one-piece plate lenses. The two most important reasons for explantation were IOL decentration (42.0%) and inflammation (27.7%). There was no significant difference for the reasons of explantations between one- and three piece IOLs (P > 0.1). Intraocular lenses that had been removed due to inflammatory reactions had a significantly longer implant duration (19.2 +/- 18.9 months) than lenses that were explanted because of decentration (9.19 +/- 12.1 months) (P = 0.018). CONCLUSIONS: The results presented here showed that there is no substantial difference between these IOLs and polymethylmethacrylate lenses in terms of reasons for explantation. The authors' data suggest that clinical outcome is not as dependent on the type of lens selected as it is on the quality of surgery. The key to good results is the use of "capsular surgery," namely techniques that ensure secure in-the-bag IOL fixation.

Cataract Extraction↗
PubMed1995

Atonic pupil after cataract surgery.

We report and describe the clinical findings of three patients who developed atonic pupil after uncomplicated extracapsular cataract extraction with posterior chamber intraocular lens implantation. All patients had normally reactive pupils one day postoperatively, but after two weeks, the pupils were dilated and nonreactive to light, accommodation, and miotics. To estimate the incidence of atonic pupil after cataract surgery, we sent a survey on the frequency, clinical features, and possible etiologies of this syndrome to members of the American Society of Cataract and Refractive Surgery. Of the 567 respondents, 60% had seen at least one case of atonic pupil in the past five years; they reported a total of 1543 cases during that time. This is probably a conservative figure since many cases undoubtedly go unnoticed because of a lack of visual disturbance. We believe this condition occurs more frequently than previously reported. The atonic pupil should be recognized as a possible complication of cataract surgery that should be included in the preoperative consent form.

Aged↗
PubMed1995

Pathology of silicone intraocular lenses in human eyes obtained postmortem.

The increased use of phacoemulsification and small incision surgery has led to interest in a soft intraocular lens (IOL) for implantation after cataract extraction. We present the pathologic findings of seven eyes obtained postmortem from five patients with silicone IOLs. Length of implantation ranged from 6 weeks to 13 months. There was symmetric bag-bag fixation in all cases. Two IOLs had distorted and compressed polypropylene loops, resulting in decentration. The silicone IOL appeared to be well tolerated in all cases.

Aged↗
PubMed1995

Is the sutureless cataract incision a valve for bacterial inoculation?

Many cataract surgeons perform sutureless surgery to decrease operating time, postoperative astigmatism, and healing time. Anecdotal case reports of postoperative endophthalmitis after sutureless surgery prompted our investigation of this type of wound closure and its possible relationship to an increased incidence of infection. This in vitro study addressed the question: Is sutureless more likely than sutured cataract surgery to provide a route for inoculation of microbial organisms into the eye? Twenty-eight human eyes obtained postmortem were randomly divided into 14 pairs and successively incubated for 90, 150, 210, and 270 minutes each in a suspension of Staphylococcus epidermidis in physiologic media. Cultured aqueous aspirates yielded no significant differences between sutured and unsutured eyes in colony counts at any time interval. This suggests that both sutured and unsutured wounds resist bacterial ingrowth equally and that a properly constructed unsutured wound is not a significant valve for bacterial inoculation in an eye pressurized to physiological conditions.

Adult↗
PubMed1995

[Anatomical evaluation of the anterior capsular zonular free zone in the human crystalline lens (age range, 50 approximately 100 years)].

It is important to determine the anterior capsular zonular free zone (ZFZ) in order to minimize the risk of zonular disinsertion. From this point of view the size of the ZFZ of normal suspended lenses was directly measured in 199 human eyes obtained postmortem. The cornea was completely excised and the iris removed to allow clear visualization of the anterior surface of the lens to the equator. After measuring lens diameter with a caliper, a 4 mm continuous curvilinear capsulorhexis was performed, and lens substrate was completely removed by phacoemulsification. Care was taken to minimize trauma to the zonules during surgery. The anterior insertion of the zonules was identified at high power magnification; the size of the ZFZ was measured with a caliper. The mean age was 75.5 +/- 10.3 (+/-SD) years (age range, 50 approximately 100 years). The mean diameter of the lenses was 9.72 +/- 0.31 mm. The mean diameter of the ZFZ was 6.83 +/- 0.35 mm. Statistical analysis revealed no significant correlation between the size of the ZFZ and age, or between the size of the ZFZ and lens diameter. The present study indicates that the size of the ZFZ was constant regardless of age or lens diameter.

Aged↗
PubMed1995

[Centering the posterior chamber lens in autopsy eyes with and without pseudoexfoliation syndrome].

The pseudoexfoliation syndrome (PEX) is an important risk factor for cataract surgery. In this study we examined a series of 24 autopsy eyes with PEX that had undergone cataract surgery and intraocular lens (IOL) implantation. The eyes were grossed for IOL fixation and centration. The results were compared to a control group of 25 non-PEX autopsy eyes that matched the PEX series in age distribution, implant duration and anatomical parameters (i.e., axial length) (P > 0.18). The mean IOL decentration in all PEX eyes (0.75 +/- 0.38 mm) was significantly higher than in the control group (0.40 +/- 0.29 mm) (P = 0.0008). Analysis of subgroups with symmetrical bag/bag fixated IOLs also showed significant higher decentration in the PEX group (P = 0.04). The main reason for decentration was decentration of the entire capsular bag in the PEX eyes (0.28 +/- 0.19 vs 0.10 +/- 0.16 in controls; P = 0.001). Patients with PEX showed a higher amount of IOL decentration. The results indicate that the insufficient suspension apparatus of the lens and decentration of the entire capsular bag are the main reasons for IOL decentration in patients with PEX.

Aged↗
PubMed1994

Clinicopathologic study of ocular trauma in eyes with intraocular lenses.

Data on 41 cases (37 intraocular lenses and four globes) of intraocular lenses explanted or expulsed after ocular trauma were retrieved from over 5,000 intraocular lenses and 1,200 globes. The age of the male and female donors varied significantly (male, 64.4 +/- 13.1 years; female, 75.5 +/- 12.6 years; P = .0334). Twenty-two were posterior chamber, 11 were anterior chamber, and eight were iris-fixated lenses. The mean implant durations were 0.66 +/- 0.9 years for posterior chamber intraocular lenses, 4.0 +/- 3.4 years for anterior chamber lenses, and 9.0 +/- 4.9 years for iris-fixated lenses. Accidental falling was the most common trauma in 14 of 21 cases (67%). In the posterior chamber intraocular lens group, trauma was more severe and resulted in rupture of the globe in 19 of 22 cases (86%) and expulsion of the intraocular lens in 15 of 22 cases (68%). Rupture usually occurred at the surgical wound, even when the trauma happened five years postoperatively. In contrast, most of the eyes with anterior chamber intraocular lenses and iris-fixated intraocular lenses did not rupture, but a minor trauma often resulted in intraocular lens dislocation and secondary complications that necessitated intraocular lens explantation. The pathologic findings were nonspecific (proteinaceous deposits, blood and pigment adherent to the intraocular lens). Severity of trauma and pathologic findings were not correlated. Posterior chamber intraocular lenses are more resistant to minor ocular trauma compared to anterior chamber and iris-fixated intraocular lenses.

Adult↗
PubMed1994

Are there acceptable anterior chamber intraocular lenses for clinical use in the 1990s? An analysis of 4104 explanted anterior chamber intraocular lenses.

PURPOSE: The authors pose the question as to whether there are any anterior chamber intraocular lenses (AC IOLs) acceptable for clinical use in the 1990s. METHODS: Data on the incidence and types of complications of 4104 AC IOLs that were submitted to the Center for IOL Research from 1982 to 1993 were retrieved from the laboratory database and analyzed using cumulative frequency calculations and the chi-square test. Normalized explantation rates were related to implantation rates that were derived from market-share analysis. RESULTS: Of 4104 explanted IOLs, 50% were closed-loop designs (n = 2095/4104); 26% (1100/4104) were miscellaneous, older designs; and 22% (919/4104) were open-loop lenses. The most important complications were corneal pathology (2065/4104) and inflammation (1370/4104). Closed-loop designs were responsible for almost 80% of corneal pathology, with an increasing complication rate with ongoing implant duration (P < 0.0001). Open-loop AC IOLs showed, in relation to their normalized rate of implantation, a significantly lower rate of complications and explantations (P < 0.01). CONCLUSION: Complication rates of flexible, open-loop AC IOLs are much lower than previously assumed. They should be distinguished clearly from most older AC IOL designs. Consideration of these lenses as an alternative to sutured posterior chamber IOLs for secondary or exchange implantation may be warranted for selected clinical indications. They also could provide an alternative to the aphakic spectacle rehabilitation program in developing countries, which will have a positive impact on the overwhelming backlog of patients with cataract in the underprivileged world.

Anterior Chamber↗
PubMed1994

Capsulorhexis in the rabbit eye as a model for pediatric capsulectomy.

Continuous curvilinear capsulorhexis (CCC) is now a standard procedure in cataract surgery. In pediatric eyes, however, this technique is difficult to perform. Because of the elasticity and tension of the pediatric anterior lens capsule, the danger of radial tears is high. Similar conditions are found in the rabbit eye. The anterior lens capsule of young albino rabbits is very elastic. We developed a CCC technique in rabbits that allows a controlled round capsular opening. This technique was used in an experimental study with 16 rabbits (32 eyes). Mean capsulorhexis diameter was 4.9 mm +/- 0.9. A radial tear occurred in only two of 32 cases. The technique, which permits a controlled circular anterior capsulectomy for capsules with high surface tension and elastic properties, may be useful in pediatric cases. A clinical trial appears warranted.

Animals↗
PubMed1994

Neodymium:YAG laser damage on silicone intraocular lenses. A comparison of lesions on explanted lenses and experimentally produced lesions.

In this study we examined 17 explanted silicone intraocular lenses (IOLs) (two one-piece, 15 three-piece) that had evidence of neodymium:YAG (Nd:YAG) laser damage. The majority of lenses (47.1%) had been explanted because of persistent pigment deposits and chronic inflammation. Decentration or IOL dislocation had occurred with 29.4% of lenses. All 17 patients had had Nd:YAG laser posterior capsulectomy, anterior surface polishing, or both; treatments ranged from one to 13 times. By both clinical and gross examination, the laser lesions appeared dark. This was misinterpreted by some opthalmologists as pigment deposits and some patients had additional Nd:YAG laser treatment, which increased the severity of the laser damage. The mean depth of laser damage on the IOLs was 143 +/- 113.4 microns. It was between 51 and 175 microns in approximately 61.0% and deeper than 300 microns (maximum 660 microns) in 9.3%. We compared the explanted IOLs with silicone IOLs that were experimentally damaged using standard power levels from 0.3 to 3.0 mJ and different focal areas. The appearance of the experimentally induced laser burns was equivalent to that on the explanted IOLs, especially the dark laser pits. Since the laser lesions may resemble pigment deposits on slitlamp examination, we recommend careful examination of patients prior to planned laser therapy.

Cataract Extraction↗
PubMed1994

Intraocular lenses for pediatric implantation: biomaterials, designs, and sizing.

Posterior chamber intraocular lenses (IOLs) are being implanted in children with increasing frequency. However, with rare exceptions, only IOLs designed for adults are currently available. These lenses may be difficult to insert into small eyes. Since the pediatric crystalline lens is smaller than that of adults and because the capsular bag does not continue to grow after lensectomy, it is worthwhile to determine the biomaterials, designs, and sizes that may be appropriate for pediatric implantation. In a study of 50 pediatric eyes obtained postmortem, we have documented an estimated growth curve for the developing crystalline lens between birth and 16 years of age. Ninety percent of crystalline lens growth occurs during the first two years of life. Based on these data and this study using the Miyake posterior view analysis of implanted standard and prototype IOLs, we recommend the following: Clinical trials of capsular IOLs, downsized to approximately 10.0 mm diameter, are appropriate for children under two years of age. Capsular IOLs are defined as flexible open-loop, one-piece, all poly(methyl methacrylate), modified C-loop designs made specifically for in-the-bag placement. Because the rapid growth phase of the lens is complete by the age of two, we believe that downsizing the IOL is not necessary after this age unless axial length measurements indicate an unusually small eye. Standard flexible 12.0 mm to 12.5 mm diameter capsular IOLs can be safely implanted. Such lenses could be tolerated throughout life, obviating the need for later IOL exchange.

Adolescent↗
PubMed1994

Comparison of mechanized anterior capsulectomy and manual continuous capsulorhexis in pediatric eyes.

Performing a continuous curvilinear capsulorhexis (CCC) can be more difficult in children than in adults because the capsular bag is more elastic. In this study we compared two capsulectomy techniques in pediatric eyes: creating a mechanized circular anterior capsulectomy using a vitrector and creating a conventional smooth-edged curvilinear tear or CCC using a forceps or needle. We used 18 pairs of eyes (36 eyes) obtained postmortem from children ranging in age from four days to 16 years. The mechanized vitrector-cut capsulectomy was unsuccessful in only one eye (from a 16-year-old child) in which a radial tear developed. Manual CCC was unsuccessful in six eyes, all from children less than five years of age. We conclude that mechanized circular capsulectomy is not only easier to perform in very young eyes than manual CCC, but it is also safe and creates a capsular opening that resists radial tearing. This mechanized technique gives the surgeon an alternative to use in pediatric eyes in which standard manual CCC may be difficult to perform and control.

Adolescent↗
PubMed1994

Pediatric cataract surgery and intraocular lens implantation techniques: a laboratory study.

The use of primary posterior capsulectomy and anterior vitrectomy during pediatric intraocular lens (IOL) implantation has been advocated as a means of preventing the development of posterior capsule opacification. In this study, we used pediatric eyes obtained postmortem to compare two different sequences in the surgical procedure: (1) anterior capsulectomy, lens substance removal, primary posterior capsulectomy with anterior vitrectomy, and IOL implantation in the capsular bag; (2) anterior capsulectomy, lens removal, IOL implantation in the capsular bag, and primary posterior capsulectomy with anterior vitrectomy. Both sequences could be safely performed in the laboratory setting while maintaining stable capsular fixation of the IOL. Placing the IOL in the capsular bag was easier when the posterior capsule was intact (sequence 2). However, both techniques appear feasible for clinical use. Surgeons not familiar with mechanized primary posterior capsulectomy can gain clinically relevant experience by operating on pediatric autopsy eyes in a laboratory setting.

Adolescent↗
PubMed1994

Penetrating keratoplasty and intraocular lens exchange: open-loop anterior chamber lenses versus sutured posterior chamber lenses.

Penetrating keratoplasty with intraocular lens (IOL) exchange is generally recommended for eyes with pseudophakic bullous keratopathy, especially when the keratopathy is associated with uveitis, chronic cystoid macular edema, or a uveitis-glaucoma-hyphema syndrome. Review of the literature has shown basically equivalent long-term results of penetrating keratoplasty and IOL exchange using both Kelman-style, flexible, open-loop anterior chamber lenses and acapsular fixation of sutured posterior chamber lenses. The use of suture-fixated posterior chamber IOLs appears warranted in centers where the surgeon has extensive experience with this specific technique and in cases with special indications, for example, in eyes with extensive angle abnormalities. However, because this technique is more difficult to perform, and in the absence of such preexisting contraindications, for most practices we do not hesitate to recommend the use of a Kelman-style anterior chamber lens during routine cases of penetrating keratoplasty and IOL exchange.

Anterior Chamber↗