Small-diameter corneal inlay in presbyopic or pseudophakic patients.

We report the results of using the small-diameter corneal inlay to create a bifocal cornea. The inlay was implanted in five eyes in January 1993. At 12 months postoperatively, uncorrected near vision had improved from J4 to better than J2 in four of the five. The results indicate that the corneal inlay improves near vision and is compatible within the cornea.

Comparison of three keratometry instruments.

We compared the reliability of measurements of three keratometers and keratometry readings from a corneal topography system to determine if they were as accurate as the "gold standard" Javal-Schiotz keratometer. Same-day measurement of the steepest and flattest powers of the central 3 mm of the corneas of 200 eyes (100 patients) revealed no statistically significant difference in reliability between the newer keratometers and the Javal-Schiotz. In addition, the newer machines are more convenient and efficient in some clinical settings.

The use of collagen shields for drug delivery in cataract and intraocular lens surgery.

Collagen shields are an appealing route of drug administration because they avoid complications associated with periocular injections and frequent topical drug application. A review of past studies establishes the capability of collagen shields to reach therapeutic aqueous drug levels in animal models. More recent studies on human subjects reaffirm the capability of collagen shields to provide adequate prophylaxis against the most common pathogens of postoperative endophthalmitis. Research on the use of collagen shields after routine cataract surgery shows that patients receiving the collagen shields had less postoperative anterior chamber reaction, less corneal edema, and fewer subconjunctival hemorrhages when compared with patients receiving the same medication through subconjunctival injection. Collagen shields may also be useful as a means to deliver other medications such as antivirals, antifungals, and immunosuppressive agents.

Ab-interno neodymium:YAG versus erbium:YAG laser sclerostomies in a rabbit model.

This study was undertaken to determine whether thermally-induced tissue necrosis was a factor in ab-interno contact-laser sclerostomy failure. A rabbit model was used to compare the continuous-wave Neodymium (Nd):YAG with the pulsed Erbium (Er):YAG laser with respect to such failure. Laser energy was focused into a fused-silica fiber optic (400 microns) for the Nd:YAG laser (12 W; 3 to 5 seconds), and into a single-crystal, uncladded sapphire fiber optic (250 microns) for the Er:YAG laser (7 to 8 mJ; 250 microseconds; 6 to 8 pulses). The Nd:YAG and Er:YAG lasers required from 21 to 35 J and from 42 to 64 mJ, respectively, to create the sclerostomies. Filtering blebs and intraocular pressure reduction lasted longer (log-rank test; P less than .03) and surgical complications were fewer in the Er:YAG group than in the Nd:YAG group. By creating sclerostomies with minimal thermal damage, the Er:YAG laser may offer significant clinical advantages over lasers producing larger thermal effects.

Combined microwave heating and surface cooling of the cornea.

We investigated a nonsurgical means of reshaping the cornea to correct hyperopia, keratoconus, or myopia. The object was to heat the central stroma of the cornea to the shrinkage temperature of collagen, 55-58 degrees C. The heating device was an open-ended, coaxial, near-field applicator driven at 2450 MHz; it incorporates cooling of the cornea surface by flow of saline. We investigated the system theoretically by computing the 2-D, axisymmetric temperature distribution with the finite element method. We investigated the system experimentally by heating excised steer corneas. Histology showed the system could shrink the stroma to a depth of 0.6 mm while sparing the epithelium in 75% of cases; the diameter of shrinkage was 1.3 mm. Theory predicted a significantly deeper and narrower region of shrinkage than was observed.

Absorption of 308-nm excimer laser radiation by balanced salt solution, sodium hyaluronate, and human cadaver eyes.

Absorption of the excimer laser radiations of 193-nm argon fluorine and 308-nm xenon chloride in balanced salt solution, sodium hyaluronate, and human cadaver eyes was measured. The absorption of these materials as considerably different for the two wavelengths; we found that 308-nm light experienced much less absorption than the 193-nm light. The extinction coefficient (k) for 308 nm was k = 0.19/cm for balanced salt solution and k = 0.22/cm for sodium hyaluronate. In contrast to this, the extinction coefficient for 193 nm was k = 140/cm for balanced salt solution and k = 540/cm for sodium hyaluronate. Two 1-day-old human phakic cadaver eyes showed complete absorption with both wavelengths. Using aphakic eyes, incomplete absorption was noted at the posterior pole with 308 nm and complete absorption was noted with 193 nm. The extinction in the anterior part of aphakic eyes (the first 6 mm) was 4.2/cm for 308 nm, meaning that the intensity of the light is reduced by a factor of 10 after traveling the first 5.5 mm. However, we observed that the material in the eye fluoresces, meaning the 308 nm is transformed into other (longer) wavelengths that travel through the total eye with minimal absorption. Conclusions drawn from this experiment are that the use of the 308-nm wavelength may have undesirable side effects, while the use of the 193-nm wavelength should be consistent with ophthalmic use on both the cornea and the lens.

Clinical management of keratoconus. A multicenter analysis.

The clinical management of 746 eyes in 417 patients referred for keratoconus from January 1984 through January 1988 was retrospectively analyzed. In 357 patients, 554 eyes (74%) did not require surgery and were managed with contact lenses or spectacles, 156 eyes (21%) in 137 patients either underwent penetrating keratoplasty (PK) (140 eyes) or surgery was recommended (16 eyes), and 36 eyes (4%) in 34 patients underwent epikeratoplasty. Comparing baseline and final examination findings, the nonsurgical group showed a significant improvement in average best-corrected visual acuity from 20/30 to 20/25, the PK group from 20/70 to 20/25, and the epikeratoplasty group from 20/40 to 20/30. Average keratometry was unchanged in the nonsurgical group, but decreased by 10.7 diopters (D) for the PK group and 6.5 D for the epikeratoplasty group. Corneal cylinder was unchanged in the nonsurgical group, whereas there was a reduction of the percentage of eyes with indeterminant cylinder from 55 to 2% in the PK group and from 36 to 0% in the epikeratoplasty group. Previous contact lens history, best-corrected visual acuity of 20/50 or worse, and average keratometry of 55 D or greater at baseline were associated with a significant risk for PK. No baseline variables were associated with significant risk for epikeratoplasty, suggesting that this group was similar to the nonsurgical group, except for contact lens intolerance. The nonsurgical management of keratoconus continues to play a predominant role in the management of this disorder in a referral population.

Seventy-six consecutive cases of IOGEL intraocular lens implants.

A single piece hydrogel IOGEL (poly-HEMA) intraocular lens was implanted in 76 eyes. Patients obtained a visual acuity of 20/40 or better in 86.9% of cases and a best case visual acuity of 20/40 or better in 98.5% of cases. Patients were followed an average of 12 months (four to 19 months). Two lenses were exchanged with poly(methyl methacrylate) lenses because of decentration-induced glare. Cystoid macular edema occurred in two cases, resulting in visual acuity worse than 20/40 in one case. Results of the study at one year mean follow-up indicate the safety and efficacy of the IOGEL lens as an intraocular implant.

Fibronectin on excimer laser and diamond knife incisions.

The experiment was designed to illustrate the difference between the diamond knife and the excimer laser (ArF 193 nm) on keratotomy incisions. The histopathologic effect of fibronectin applied to these wounds was observed. Fibronectin demonstrated a chemotactic effect on fibroblasts and increased the amount of newly synthesized collagen deposited at the incision sites. The excimer laser incisions treated with fibronectin had 43% more fibroblasts per 2,500 microns 2 than the excimer laser incisions not treated with fibronectin. The adjustable diamond knife incisions treated with fibronectin had 42% more fibroblasts than the adjustable diamond knife incisions not treated with fibronectin. The excimer laser ArF 193 nm incisions had 18% more fibroblasts in the incision area than the adjustable diamond knife incisions independent of fibronectin usage. This indicates that the excimer laser incisions and the diamond knife incisions may have different healing mechanisms--perhaps because of the distinctive modes of action of these instruments.

Endocapsular triple procedure--a new triple procedure technique.

The triple procedure (penetrating keratoplasty, cataract extraction, and intraocular lens implantation) performed using endocapsular cataract extraction and posterior chamber intraocular lens implantation offers advantages over the extracapsular technique. The most significant advantage is easier, assured placement of the posterior chamber intraocular lens entirely in the bag. Another advantage is less chance of injury to the endothelial cells. This paper describes a technique using endocapsular cataract extraction in the triple procedure.

Extending corneal storage with 2.5% chondroitin sulfate (K-Sol).

K-Sol corneal storage medium maintains corneal viability for at least ten days, compared with McCarey-Kaufman (M-K) medium, which does so for a reported maximum of three days. Since many eye banks still use M-K medium exclusively, stored corneas must be used without undue delay, and shipping time further hastens the planned surgery time. Transferring the shipped M-K medium-stored cornea to K-Sol offers a simple way of increasing storage time in our eye bank. Ninety-five out of 100 transferred corneas (95%) remained clear 3 to 18 months postoperatively. There were no primary graft failures, and transferred corneal mates were clear. A comparable series of 100 corneas stored in M-K medium alone, or in K-Sol alone, were clear in 93% and 97% of the transplants. Analysis of donor rims after keratoplasty indicated statistically significantly more endothelial cell loss during storage in corneas transferred to K-Sol compared with 18 corneas preserved only in M-K medium for a similar length of time. There was no statistical significance between the transferred group and the group preserved in only K-Sol. Transferring M-K medium stored corneas to K-Sol medium may be a useful means of extending corneal storage time, resulting in improved tissue utilization.

Effect of excimer laser on microbiological organisms.

The effect of radiation emitted from an excimer laser filled with argon fluoride gas at 193 nm on Serratia marcescens, Pseudomonas aeruginosa, Staphylococcus aureus, streptococcus faecalis, Hemophilus influenzae, Candida albicans, and Aspergillus niger (collectively labeled "the microorganisms") was examined. Colonies were subjected to a variable number of radiation pulses from the excimer laser applied after a 36-hour period of incubation at 37 degrees C, at which time the colonies were fully grown and showed no viability. The lack of viability was confirmed with a subculture from each area that received radiation; all subcultures were negative. The characteristics of the radiation paralleled those used by Serdavic, Darrell, Krueger, et al in 1985.(1) This radiation treatment is believed to be within a therapeutic range, which suggests that the excimer laser, pending further investigation, may be useful in the treatment of corneal infections.

The nationwide study of epikeratophakia for aphakia in older children.

A nationwide study of epikeratophakia for aphakia in older children was conducted from March 1984 to March 1986. Sixty-three patients, 8 to 18 years of age, underwent this procedure in 65 eyes. Twenty-eight patients had congenital cataracts and 35 had traumatic cataracts. Fifty-one of the 65 eyes were aphakic at the time of surgery (secondary procedures). All surgeries were successful; no tissue lenses were lost or removed. Postoperatively, 73% of the patients were within 3 diopters (D) of emmetropia. The patients with congenital cataracts gained an average of one Snellen line of best-corrected visual acuity; patients with traumatic cataracts lost an average of one Snellen line of best-corrected visual acuity. In older pediatric patients, epikeratophakia appears to be a safe and effective procedure for the correction of aphakia.

Coated intraocular lenses.

We found that an intraocular lens with a bonded coating of sodium hyaluronate caused less cell damage than an uncoated lens. We also found that an intraocular lens bonded with sodium hyaluronate will provide not only better adherence to viscoelastic materials and endothelial protection, but also may allow for better manipulation of the lens intraocularly. This is the first report of a sodium hyaluronate-coated intraocular lens used to prevent cell damage.

Clinical results of the multifocal lens.

The multifocal posterior chamber intraocular lens was implanted in 46 eyes of 38 patients as part of the first clinical trial of this target-type implant. No major complications were reported. Visual acuity results for distance and near vision were excellent, with best case visual acuities better than 20/40 in over 95% of eyes in the first three months.

Effect of the Nd:YAG laser on polymethylmethacrylate, HEMA copolymer, and silicone intraocular materials.

Recent trends of cataract extraction feature both small surgical wounds and preservation of posterior capsules. The development of safe, reliable, and flexible implant materials that can withstand near impact with a Nd:YAG laser during secondary posterior capsule discissions are required. An in vitro experiment was performed to analyze the effects of Nd:YAG laser irradiation on polymethylmethacrylate (PMMA), hydroxyethylmethacrylate (HEMA), hydroxyethylhydroxymethylmethacrylate (HEMA-MEMA) copolymer combination, and a silicone compound. The HEMA and HEMA-MEMA compounds were the least susceptible to Nd:YAG laser damage in this laboratory setting.

Carbon dioxide laser use in wound sealing and epikeratophakia.

This paper presents current clinical and experimental uses of the carbon dioxide laser and the results of our human and animal tissue fusion investigations. Trials were conducted with human scleral and corneal eye bank tissue and in albino rabbits. With power settings of 100 to 200 mW, optimal laser effect consisting of slight whitening and minimal edge shrinkage occurred between 10 and 70 mJ of total energy. No tissue adherence could be demonstrated with the parameters tested. A final study was made on the feasibility of sealing an epikeratophakia lenticle to its recipient bed using the carbon dioxide laser. The average force required to remove the button in the control experiments was 6.45 g and this increased to 6.99 g after laser treatment although no fusion was apparent. This was statistically significant (P less than .05).

The nationwide study of epikeratophakia for aphakia in adults.

In the nationwide study of epikeratophakia, 154 ophthalmic surgeons who had attended a training course performed 519 procedures for the correction of aphakia in adults: 310 of the eyes had 30 or more days of follow-up after suture removal. Of 229 eyes, 172 (75%) were within 3 diopters of emmetropia after surgery. Of 259 eyes, 245 (95%) demonstrated improved uncorrected visual acuity; 138 (53%) improved by four or more Snellen lines. Of 265 eyes, 209 (78%) achieved within two lines or improved their best corrected visual acuity. Of the 119 patients who achieved or improved their preoperative best corrected visual acuity, 110 (92%) were within two Snellen lines or better by 30 to 60 days after suture removal. Of the 127 patients with more than three months of follow-up after suture removal, 124 (98%) of those between 18 and 70 years of age but only 13 of 23 (54%) of those between 81 and 87 years of age achieved within two lines or better of their best corrected visual acuity. Corneal astigmatism measured by keratometry changed from a preoperative mean (+/- S.D.) of 2.1 +/- 1.8 diopters to a postoperative mean of 2.7 +/- 2.6 diopters. Of the 519 tissue lenses, 22 (4%) were removed, and one third of these patients underwent a second, successful epikeratophakia procedure.