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Biomedical subjects

P H Ernest

Publications and source records attributed to P H Ernest.

12 recordsLinked to original sources
PubMed1998

Occurrence of pigment precipitates after small incision cataract surgery.

PURPOSE: To assess the incidence of pigment precipitates and potential association with glaucoma, diabetes, and/or intraocular lens (IOL) optic center thickness in patients having small incision cataract surgery and foldable IOL implantation. SETTING: Eye Care Physicians of Michigan, Jackson, Michigan, USA. METHODS: A retrospective data analysis was conducted of patients with a preoperative diagnosis of glaucoma or diabetes or in whom pigment precipitates had been reported after cataract surgery. Group 1 consisted of 23 patients in whom pigment precipitates had been reported and Group 2, 92 patients in whom no precipitates were reported. Two statistical models were used to analyze preoperative, demographic, surgical, and postoperative variables and determine potential correlations. An overall incidence of the occurrence of pigment precipitates was calculated based on the total number of patients with foldable IOLs. RESULTS: The incidence of pigment precipitates was 0.35% (n = 23/6519). Mean time to occurrence was 5.5 months. No between-group differences were found in pathologies or other demographics or postoperative variables. Intraocular lens size and implantation correlated with the occurrence of pigment precipitates. CONCLUSION: The development of pigment precipitates after foldable IOL implantation did not appear to be affected by the presence of glaucoma or diabetes. Newer, slimmer IOL styles and refined insertion techniques were associated with a lower occurrence of precipitates.

Aged↗
PubMed1995

Endothelial cell loss after 4 mm cataract surgery.

To assess whether a 4 mm scleral tunnel incision with a 1.5 mm internal corneal lip (three-step procedure) causes increased endothelial cell loss and damage to the cornea, we retrospectively evaluated the outcomes of 20 patients (40 eyes) who had a standard 4 mm scleral tunnel incision (two-step procedure) in one eye followed by a three-step incision in the second eye, with in situ phacoemulsification and insertion of a foldable silicone lens in each eye. Mean phacoemulsification time was 2.4 +/- 1.1 minutes for the two-step incisions and 3.4 +/- 1.4 minutes for the three-step incisions. Preoperative and postoperative endothelial cell counts were obtained to determine the effects of surgery on the corneal endothelium. Although the three-step procedure had a trend toward increased endothelial cell loss from the central corneal region compared with the two-step incision, the result was neither clinically nor statistically significant. The difference between the three-step and two-step incisions in postoperative endothelial cell counts from the superior corneal region was statistically significant. The difference in postoperative counts from the inferior region was not statistically significant. Although the three-step 4 mm incision does seem to affect the corneal endothelium, its clinical significance is unknown.

Aged↗
PubMed1995

Relative stability of clear corneal incisions in a cadaver eye model.

Three different clear corneal square incisions--beveled (or paracentesis), stepped, and hinged--were studied in a cadaver eye model to determine whether a critical width existed for each incision type at which resistance to external pressure changed substantially, given identical tunnel length (1.75 mm to 2.00 mm) for each incision. As a comparison, the beveled (paracentesis) incision was also performed as a clear corneal incision at the anterior limbus, making it a limbal beveled incision. One surgeon performed all procedures. Incision width ranged from 2.5 mm to 5.0 mm in 0.5 mm increments. External pressure as high as 525 psi was applied to all eyes at two ranges of intraocular pressure (10 mm Hg to 15 mm Hg and 20 mm Hg to 25 mm Hg) to determine the relative ability of each incision type to resist leakage. The hinged incision performed better than the stepped and corneal beveled incisions. When the beveled (paracentesis) incision was made as a clear corneal limbal beveled incision at the anterior limbus, the limbal structures provided additional support in resisting externally applied pressure. When the clear corneal beveled technique is used, incision width should be 3.0 mm or less. When clear corneal stepped or hinged techniques are used, incision width should be 3.5 mm or less.(ABSTRACT TRUNCATED AT 250 WORDS)

Cadaver↗
PubMed1994

Corneal lip tunnel incision.

To evaluate whether the corneal lip tunnel incision or the sutureless closure causes any refractive problems, we performed a retrospective study on 387 cataract surgery patients who were divided into four groups based on type of wound closure and whether the corneal lip was made. The four groups consisted of patients who received an X-stitch closure without the corneal lip, a horizontal mattress stitch without the lip, a horizontal mattress stitch with the lip, and a sutureless closure with the lip. All patients had phacoemulsification in situ; implantation of a foldable silicone lens was performed through a scleral tunnel incision. Clinical evaluations included preoperative characteristics and postoperative Snellen visual acuity, intraocular pressure, and vector analysis of cylinder. In all four groups, a 4.0 mm wide incision was used. Entrance into the clear cornea during the corneal lip tunnel incision did not induce additional cylinder, and the sutureless closure did not decrease induced cylinder or increase the against-the-rule shift. The results of this study indicate that the combination of a 4.0 mm incision with 1.5 mm corneal lip, phacoemulsification in situ, foldable lens implantation, and sutureless closure is a safe and effective procedure for cataract surgery.

Aged↗
PubMed1994

Relative strength of scleral corneal and clear corneal incisions constructed in cadaver eyes.

Square scleral corneal, square clear corneal, and rectangular clear corneal incisions were constructed in six cadaver eyes that had no previous intraocular surgery. The 3.2 mm or smaller wounds had sutureless closures. To determine their relative abilities to resist leakage and iris prolapse, eyes were tested at external pressures of up to 525 pounds per square inch (psi) at one of two intraocular pressure (IOP) ranges: 10 to 15 mm Hg or 20 to 25 mm Hg. The square scleral corneal (3.2 mm x 3.2 mm) and square clear corneal wounds (3.2 mm x 3.2 mm, 2.0 mm x 2.0 mm, 1.0 mm x 1.0 mm) withstood external pressure without effect at both IOP ranges, up to the maximum 525 psi. This level of external pressure was far greater than pressures withstood by rectangular clear corneal wounds, especially the wound usually constructed in clinical practice (3.2 mm x 2.0 mm), which leaked and demonstrated iris prolapse at 13 psi at the lower IOP. The square clear corneal wounds that were stable at 525 psi, however, are either clinically impractical (visual axis encroachment from 3.2 mm x 3.2 mm wound) or not technologically feasible until the size of phacoemulsification tips and intraocular lenses can be further reduced. Thus, of the procedures for small incision cataract surgery presently in use, the square scleral corneal incision with 1.5 mm internal corneal lip appears to offer greater stability and safety than the conventional rectangular clear corneal incision (3.2 mm x 2.0 mm).

Cadaver↗
PubMed1993

Scleral tunnel incision with internal corneal lip in patients with low preoperative corneal endothelial cell counts.

We studied 40 eyes from patients with pre-existing corneal endothelial cell dystrophy (endothelial cell counts of less than or equal to 1,200/mm2) to assess whether the scleral tunnel incision with internal corneal lip and phacoemulsification in situ procedure affected the cornea. Identification of endothelial cell dystrophy by measuring preoperative endothelial cell counts was important so minor modifications of decreased phacoemulsification power and frequent viscoelastic endothelial coating could be made to prevent damage to the eyes. The procedures had no effect on corneal thickness or endothelial cell counts. Only about one fourth of the eyes studied (11) had more than 10% endothelial cell loss; none of the 11 eyes showed clinical evidence of corneal decompensation. All patients without other underlying pathologies such as macular degeneration attained postoperative visual acuity of at least 20/40. The scleral tunnel incision with internal corneal lip and phacoemulsification in situ procedure, with minor modifications, is safe in patients with endothelial cell dystrophy of the cornea.

Cataract Extraction↗
PubMed1993

Relative strength of scleral tunnel incisions with internal corneal lips constructed in cadaver eyes.

We constructed scleral tunnel wounds with internal corneal lips and sutureless closures in ten cadaver eyes without previous intraocular surgery. Each wound differed in width, total incision length, and internal corneal lip size. At a low and high range of initial intraocular pressure (IOP, 10 to 15 mm Hg or 20 to 25 mm Hg), we compared the wounds' resistance to leakage during application of external pressure. A square wound with a 4.0 mm width and 4.0 mm overall length, including a 1.5 mm corneal lip, had the optimum wound dimensions. These produced a stable incision that resisted leakage at external pressures up to 525 pounds per square inch equally well at both IOP ranges. Leakage occurred at lower external pressures for wounds with greater width, smaller corneal lips, or wound widths that were greater than wound lengths; such wounds were also more prone to leakage at the low IOP range. When constructed properly and adequately, the 4.0 mm wide scleral tunnel incision with 1.5 mm internal corneal lip is a strong and safe wound for sutureless cataract surgery.

Cataract Extraction↗
PubMed1991

Relative strength of cataract incisions in cadaver eyes.

We evaluated the strength of various incisions used in cataract surgery in cadaver eyes. Fluid was forced into the eye through a paracentesis incision and measured via a second paracentesis incision connected to a pressure transducer. In four eyes with the limbal, two-step procedure and radial sutures, leakage from the wound was seen at 100 mm Hg to 120 mm Hg, and iris prolapse through the wound occurred at 160 mm Hg to 400 mm Hg. In three eyes with the scleral tunnel two-step procedure, no prolapse was observed at pressures up to 400 mm Hg, although leakage was observed in two eyes at 400 mm Hg. In two eyes with the three-step procedure with an internal corneal lip, no leakage or prolapse was observed at pressures up to 400 mm Hg or upon manipulation of the wound at various pressures. In an additional evaluation of four eyes with the three-step procedure, no leakage or prolapse was observed with compressed air at pressures over 2,000 mm Hg. A three-step incision with an internal corneal lip may provide a more pressure resistant wound than a two-step limbal or scleral tunnel incision.

Cataract Extraction↗
PubMedDate not supplied

Posterior limbal incision.

BACKGROUND: Sutureless cataract incisions should ideally remain sealed with increased intraocular pressure and be able to withstand increased external pressure to the posterior aspect. Cadaver eye studies have shown that meeting these criteria requires an internal corneal lip of at least 1.5 mm and a square wound. Scleral incisions can meet these criteria but sacrifice aesthetics and surgical efficiency. Clear corneal incisions provide aesthetics and surgical efficiency but not wound stability. An ideal incision would combined stability with aesthetics and efficiency. METHODS: We tested a posterior limbal incision to assess its stability, aesthetics, and efficiency. The incision originated at the posterior limbus within the conjunctiva, gaining about 1.0 mm in tunnel length over a clear corneal incision. This was enough to obtain a square profile for 3.0 x 3.0 mm wide incisions, while providing the aesthetics and surgical efficiency of a clear corneal incision. We compared a 3.0 x 2.0 mm posterior limbal with a 3.0 x 2.0 mm clear corneal incision. Each was tested in stepped, paracentesis, and hinged profiles. CONCLUSIONS: When compared with the clear corneal incision, the posterior limbal incision is equal in aesthetics and surgical efficiency, slightly superior in patient comfort, and far more stable.

Cataract Extraction↗