Artificial corneas: a regenerative medicine approach.

Corneal substitutes are being developed to address the shortage of human donor tissues as well as the current disadvantages in some clinical indications, which include immune rejection. In the past few years, there have been significant developments in bioengineered corneas that are designed to replace part or the full thickness of damaged or diseased corneas that range from keratoprostheses that solely address the replacement of the cornea's function, through tissue-engineered hydrogels that permit regeneration of host tissues. We describe examples of corneal substitutes that encourage regeneration of the host tissue. We also contend that it is unlikely that there will be a single "one-size-fits-all" corneal substitute for all indications. Instead, there will most likely be a small range of corneal substitutes ranging from prostheses to tissue-engineered matrix substitutes that are tailored to different clusters of clinical indications. The tissue-engineered matrices can either be produced as sterile acellular matrices, or complete with functional cells, ready for implantation.

Changes in measured intraocular pressure after hyperopic photorefractive keratectomy.

PURPOSE: To investigate the effect of hyperopic photorefractive keratectomy (PRK) on intraocular pressure (IOP) measurements. SETTING: University of Ottawa Eye Institute, Ottawa Hospital, Ottawa, Canada. METHODS: In this retrospective cohort study, IOP and central corneal thickness (CCT) were measured preoperatively and at 1, 2, 3, 6, 12, 18, and 24 months in 191 eyes that had hyperopic PRK with the VISX Star excimer laser. All corrections applied were between +1.00 and +6.50 diopters (D) of sphere and less than 3.75 D of cylinder. RESULTS: At all postoperative examinations, the mean IOP in the hyperopic PRK group was 1.0 to 1.8 mm Hg lower than the preoperative IOP (P <.001). A large range of IOP changes was found across the population; eg, at 6 months, 49% of the eyes had a change in IOP from baseline of at least +/-3 mm Hg. A mean reduction of 19 microm of CCT was found with pachymetry after surgery (P < .001). The change in IOP readings postoperatively was not correlated with age, sex, keratometric readings, or applied correction. Changes in IOP were strongly correlated with preoperative IOP at all time points and with preoperative CCT at 18 and 24 months (P < .001). After hyperopic PRK, the measured IOP was more likely to increase in patients with preoperative IOPs less than 14.5 mm Hg and more likely to decrease in patients with preoperative IOPs above 14.5 mm Hg. CONCLUSION: Changes in IOP after hyperopic PRK were similar to changes after myopic PRK, despite only minimal changes in the CCT. This suggests that hyperopic PRK results in biomechanical effects that modify the elastic properties of the cornea beyond the changes in rigidity expected from central corneal thinning. There was a strong negative correlation between the measured preoperative IOP and the change in IOP postoperatively that was likely the result of regression of the mean effect.

Marginal infiltrative ulcerative keratitis secondary to Churg-Strauss syndrome: a case report.

PURPOSE: To describe a patient with keratitis associated with Churg-Strauss syndrome. METHODS: A 44-year-old lady with known Churg-Strauss syndrome was examined with marginal infiltrative ulcerative keratitis. RESULTS: Autoimmune disorders with systemic vasculitis are a major cause of marginal keratitis, and in this patient, the diagnosis of Churg-Strauss was confirmed clinically and pathologically. CONCLUSIONS: Churg-Strauss syndrome should be considered in the differential diagnosis of marginal keratitis.

Recent advances in refractive surgery.

Refractive errors are some of the most common ophthalmic abnormalities world-wide and are associated with significant morbidity. Tremendous advances in treating refractive errors have occurred over the past 20 years. The arrival of the excimer laser has allowed a level of accuracy in modifying the cornea that was unattainable before. Although refractive surgery is generally safe and effective, it does carry some risks. Careful patient selection, meticulous surgical technique and frequent follow-up can avoid most complications. The experience of a surgical team can also affect the outcome and the incidence of complications. The future should bring continued improvement in outcomes, fewer complications and exciting new options for treating refractive errors.

Laser vision correction for low hyperopia. An 18-month assessment of safety and efficacy.

OBJECTIVE: This study aimed to assess the efficacy and safety of hyperopic photorefractive keratectomy (PRK) and to evaluate the effect of degree of hyperopia, two epithelial removal methods, and various postoperative patient management techniques on clinical outcomes. DESIGN: Prospective, nonrandomized, open-label clinical trial. PARTICIPANTS: A total of 38 patients with mean follow-up of 13.9 months (n = 65 eyes with hyperopia from +1.00 diopter [D] to +4.00 D) participated. INTERVENTION: Hyperopic PRK with the VISX STAR Excimer Laser System was performed. MAIN OUTCOME MEASURES: Spherical equivalent (SE) including vector analysis of SE; uncorrected visual acuity (UCVA); best-spectacle corrected visual acuity (BSCVA); low-, medium- and high-contrast visual acuities; topography; keratometry; pachymetry; and intraocular pressure, haze, and all other potential complications were measured. RESULTS: A total of 80% of eyes were within +/- 0.5 D and all but 1 eye (98%) were within +/- 1.0 D of intended manifest SE at 1 year. There was no induced astigmatism at 1 year. At 12 months, 72% of eyes had UCVA of 20/25 or better and 70% had achieved preoperative BSCVA, with no eye seeing worse than 20/25. These results remained constant at 18 months. There was a tendency toward regression between months 1 and 6 with stabilization of SEs between months 6 and 12. Thereafter, up to 18 months, there was some regression with a mean of +0.31 D, but the number of patients was small. There was one mild decentration and very slight decreases in mean intraocular pressure and central corneal thickness. One patient had grade 1.0 haze develop in both eyes at 12 and 18 months; all other patients experienced trace or no haze. There were no significant complications. CONCLUSIONS: The results of this study support the hypothesis that laser vision correction is safe and effective for treating low hyperopia. The predictability of the hyperopic laser vision correction procedure used in this study was very good. Other than the slower recovery of BSCVA and UCVA seen with this procedure, as compared with myopic PRK, there were no significant complications. The trend toward some later regression needs to be further evaluated in a larger number of patients. Overall, patients were very pleased with the treatment, even in the first 6 months.

Evaluation of current techniques of corneal epithelial removal in hyperopic photorefractive keratectomy.

PURPOSE: To determine the efficacy of 3 current methods used to remove corneal epithelium prior to photorefractive correction of hyperopia and to compare clinical data in patients who had rotary brush or blunt scrape epithelial removal in the treatment of hyperopic photorefractive keratectomy (PRK). SETTING: University of Ottawa Eye Institute, Ottawa General Hospital, Ottawa, Ontario, Canada. METHODS: The epithelium from human eye-bank eyes was removed using a Paton spatula, 15% alcohol, and the Amoils rotating plastic brush. The effects were examined by scanning and transmission electron microscopy. Twelve month postoperative data were obtained on 25 eyes with refractions of +1.00 to +4.00 diopters (D) that had been treated for hyperopia with the VISX Star excimer laser, using blunt scrape or the rotary brush to remove the corneal epithelium. RESULTS: All 3 methods effectively removed corneal epithelium. The Paton spatula, however, left small nicks in Bowman's layer. Both the rotating brush and alcohol debridement left Bowman's layer intact. Alcohol treatment required follow-up epithelial debris removal, while brushing left minimal amounts of debris. There was a strong trend toward rapid epithelial healing in the brushed corneas compared with the scraped ones, but this was not statistically significant. Clinically, at 12 months postoperatively, brushed corneas showed a trend toward more superior outcomes than scraped corneas in actual refractive outcome, uncorrected visual acuity (UCVA), lines of UCVA gained, and predictability of the desired outcomes. However, only the outcome in UCVA of 20/40 or better and the decreased incidence of haze in the brushed corneas over scraped ones were statistically significant. CONCLUSIONS: Both alcohol and the rotating brush provide a quick, effective means of removing the corneal epithelium with minimal risk of damage to Bowman's layer. In our experience, the brush technique was as effective as and possibly superior to the blunt scrape for epithelial removal in hyperopic PRK.

Correction of intraocular pressure for changes in central corneal thickness following photorefractive keratectomy.

OBJECTIVE: To investigate the relation between measurements of intraocular pressure (IOP) and central corneal thickness (CCT) in myopic patients undergoing photorefractive keratectomy (PRK). DESIGN: Descriptive study. SETTING: University-affiliated eye care centre in Ottawa. PATIENTS: A total of 481 consecutive eyes of 318 patients with a mean preoperative refractive error of -6.50 dioptres treated with excimer PRK between March 1993 and December 1996. OUTCOME MEASURES: IOP measured by Goldmann applanation tonometry and CCT before and 3, 6, 12, 18 and 24 months after surgery. RESULTS: CCT was a significant predictor of IOP only before PRK and 6 months after PRK (p < or = 0.05). The relation between IOP and CCT suggests corrections for CCT that are not clinically significant (0.81 mm Hg [standard error (SE) 0.33 mm Hg] and 1.00 mm Hg [SE 0.38 mm Hg] per 100 microns of corneal thinning preoperatively and at 6 months respectively). On average, there was a significant decrease in IOP after PRK (0.96 mm Hg and 1.24 mm Hg at 12 and 24 months respectively) (p < 0.05). There was a significant correlation between change in IOP and change in CCT (decrease of 2.1 mm Hg per 100 microns of corneal thinning) (p < 0.05). For a given change in CCT, individual changes in IOP were variable, with increases or decreases of more than 5 mm Hg in some cases. CONCLUSIONS: There are individual differences in IOP changes following PRK. Until further data are available we propose that the change in IOP between the preoperative visit (or the fellow eye, if healthy or untreated) and the 12-month visit be used as an individual correction factor to be applied to IOP measurements in the operated eye.

Ocular allergic disease.

Ocular allergy is a common condition that usually affects the conjunctiva of the eye and is therefore often referred to as allergic conjunctivitis. The severity of the disease can range from mild itching and redness, as seen in seasonal allergic conjunctivitis, to the more serious vision threatening forms of ocular allergy which affect the cornea, such as atopic keratoconjunctivitis. The pathogenesis of allergic conjunctivitis involves a complex mechanism which centers around IgE-mediated mast cell degranulation and release of multiple preformed and newly formed inflammatory mediators. The diagnosis of allergic conjunctivitis is usually a clinical one which can be made based on a thorough history and careful examination. Treatment of ocular allergy should begin with conservative measures including allergen avoidance, environmental control, ocular irrigation and cold compresses. Pharmacotherapy of allergic conjunctivitis consists of several classes of drugs. Antihistamines are widely used to treat mild conditions such as seasonal and perennial conjunctivitis and potent new agents such as levocabastine and emedastine are now available. Mast cell stabilizers such as sodium cromoglycate are both safe and effective and are commonly used in ocular allergy. More effective mast cell stabilizers such as nedocromil, lodoxamide and olopatadine are now being used. Nonsteroidal antiinflammatory drugs have demonstrated only limited efficacy and, as such, are not widely used. Topical steroids are very effective in treating signs and symptoms but are reserved for only refractory cases due to their serious side effects. Loteprednol and rimexelone are newer corticosteroids which reportedly have less of an effect on intraocular pressure. Cyclosporine has recently been shown to be highly effective in cases of vernal keratoconjunctivitis and atopic keratoconjunctivitis while producing no adverse effects.

Post-traumatic corneal mucormycosis caused by Absidia corymbifera.

OBJECTIVE: The purpose of the study was to report a case of mycotic keratitis caused by the organism Absidia corymbifera (class Zygomycetes, order Mucorales, family Mucoraceae). DESIGN: Case report. PARTICIPANT: A healthy 37-year-old farmer scratched his left cornea on a galvanized nail while working in his barn. Within 24 hours, an infiltrate in the interior cornea developed that advanced superiorly, reducing the vision to hand motion by the following day. He was treated with topical and systemic antibiotics and antifungal medications, but the infiltrate spread to the adjacent nasal limbus. INTERVENTION: An 11-mm penetrating keratoplasty was performed with an adjacent nasal 7-mm superficial lamellar sclerectomy. MAIN OUTCOME MEASURES: Pathologic examination of the keratoplasty specimen. RESULTS: Corneal cultures grew A. corymbifera. The organisms were identified in tissue sections by light, fluorescent, electron, and immunoelectron microscopy. CONCLUSIONS: The authors believe that this is the first reported case of keratitis caused by an Absidia species and, as such, represents an unusual form of mucormycosis in an otherwise healthy individual.

Excimer laser photorefractive keratectomy for low hyperopia: safety and efficacy.

PURPOSE: To assess the safety and efficacy of photorefractive keratectomy (PRK) to correct low hyperopia. SETTING: University of Ottawa Eye Institute, Ottawa General Hospital, Ontario, Canada. METHODS: Twenty-five eyes with refractions of +1.00 to +4.00 diopters (D) and cylinder of 1.00 D or less were treated for hyperopia with the VISX Star excimer laser system using a refined ablation architecture. Thorough visual assessments were performed preoperatively (baseline) and 1, 3, and 6 months postoperatively. Complications were recorded and the level of patient satisfaction was noted. RESULTS: Mean spherical equivalent at 6 months was +0.27 D +/- 0.55 (SD), which was an 89% reduction over baseline. Eighty-four percent of patients gained two to seven lines of near uncorrected visual acuity (UCVA) and 1 patient (4%) lost more than one line. Eight percent achieved 20/25 or better UCVA. Approximately half realized their preoperative distance best corrected visual acuity (BCVA) by 1 month. By the end of the study, all patients had improved, achieved, or were within one line of their baseline distance BCVA. There were some slight reductions in lower contrast acuity at 6 months, although dim lighting conditions did not further reduce these acuities. Most patients had no clinically meaningful change in cylinder. The most common complications included early, transient corneal surface irregularities and visual symptoms and trace haze (grade < or = 0.5) in 14 of 23 patients at 6 months. All but 1 patient expressed a high degree of satisfaction. CONCLUSIONS: These results support the hypothesis that PRK shows great promise as a safe and effective treatment for low hyperopia. There were no significant complications and no decentered ablations. The slight regression occurred with or without the presence of trace haze. Overall, refractive stability was encouraging, although longer follow-up is needed.

Perioperative ofloxacin vs. tobramycin: efficacy in external ocular adnexal sterilization and anterior chamber penetration.

OBJECTIVE: To compare the efficacy of two treatment regimens, tobramycin drops-erythromycin ointment and ofloxacin drops-placebo ointment, in sterilizing the external ocular adnexa when given perioperatively. A second objective was to determine the aqueous humour concentration of ofloxacin and tobramycin. DESIGN: Randomized double-blinded clinical trial. SETTING: University-affiliated hospital. PATIENTS: Patients aged 18 years or more scheduled to undergo planned cataract surgery who were judged likely to complete the trial. NUMBERS: Of 55 patients enrolled 6 were disqualified and 49 completed the trial. INTERVENTIONS: Preoperative instillation of 10 drops of a 0.3% solution of ofloxacin (26 eyes) or tobramycin (23 eyes) in the operative eye, starting the evening before surgery. Tobramycin-treated eyes received erythromycin ointment after surgery; ofloxacin-treated eyes received petrolatum ointment. Lid and conjunctival swabs were obtained from both eyes on the day before surgery (visit 1), at surgery (visit 2) and on the first postoperative day (visit 3). Aqueous humour samples were obtained from the study eyes at surgery. MAIN OUTCOME MEASURES: Threshold growth of bacteria on culture, aqueous humour concentration of ofloxacin or tobramycin. RESULTS: At visit 1, 96% of all eyes had positive cultures; this result persisted at visits 2 and 3 for the control eyes. For the treated eyes the incidence of positive cultures decreased from visit to visit. By visit 3 lid cultures were positive for 7 (27%) of the ofloxacin-treated eyes and 7 (30%) of the tobramycin-treated eyes; conjunctival cultures were positive for 0 (0%) of the ofloxacin-treated eyes and 1 (4%) of the tobramycin-treated eyes. No significant differences were seen in culture positivity between the treatment groups at any visit. The mean aqueous humour concentration of ofloxacin was significantly higher than that of tobramycin (0.4084 vs. 0.0279 microgram/mL) (p < 0.001). CONCLUSIONS: Both ofloxacin-placebo treatment and tobramycin-erythromycin treatment were more effective than no treatment in sterilizing the external ocular adnexa. The two treatments were equally efficacious in eliminating bacteria, more successfully in the conjunctiva than the lids. Topically administered ofloxacin demonstrated significantly greater anterior chamber penetration than topically administered tobramycin.

Postoperative irradiation following immediate breast reconstruction using a temporary tissue expander.

Ten consecutive patients at Howard University Hospital underwent modified radical mastectomy with immediate breast reconstruction using a temporary tissue expander. Postoperative irradiation was delivered to the breast mound encompassing the tissue expander. The effects of expansion on the delivery of postoperative irradiation was assessed. Dosimetric measurements with thermoluminescent dosimeters revealed that the saline-filled expander attenuated the photon beam 3% less than tissue-equivalent material of equal volume. This dose variation was negligible, so no adjustments were made. Postoperative treatment consisted of 5040 cGy to 5220 cGy delivered in 5 to 10 weeks using 4 mV photon tangentials. Cosmesis was assessed over a 2-year period. Six patients completed reconstruction and irradiation without complications. Cosmesis was good in five and fair in one. One patient developed a moist reaction secondary to postoperative irradiation; however, final cosmesis was good. Three patients developed complications leading to the loss of the reconstructed breast. Successful final reconstruction can be achieved with careful patient selection and close follow-up by the plastic surgeon and radiation oncologist.

Pars plana vitrectomy in the management of vitreous touch syndrome.

The management of three patients with aphakic bullous keratopathy by means of pars plana vitrectomy is described. The patients had previously undergone uneventful intracapsular cataract extraction with intact vitreous face. Eventual herniation of the vitreous into the anterior chamber with resultant corneal endothelial touch caused the corneal edema in all three cases. Pars plana vitrectomy resulted in resolution of photophobia and irritation. The visual acuity improved from 20/200, 20/200 and 20/70 to 20/70, 20/60 and 20/40 respectively. The central cornea was cleared of edema in all three cases. The final vision was limited in two of the patients by the persistence of preoperative cystoid macular edema. Pars plana vitrectomy may be used in the management of selected cases of aphakic bullous keratopathy from vitreous touch.

Differentiating conjunctivitis of diverse origins.

While symptoms can be very distressing, patients with conjunctivitis general maintain good vision and recover completely without permanent sequelae. The great majority of cases of conjunctivitis are infectious or allergic in origin. Seen with increasing frequency are external eye diseases related to contact lens wear or prolonged use of ophthalmic medications. The various forms of conjunctivitis are often not associated with pathognomonic features. A thorough history and ophthalmic examination often permit a presumptive diagnosis and initiation of empiric therapy. For example, a chronic bilateral conjunctivitis, characterized by itching and papillary hypertrophy, suggests an ocular allergy, most frequently the result of exposure to airborne allergens. However, a number of causes, including infections and hypersensitivity reactions, have the potential to threaten vision or produce marked conjunctival scarring which must be identified by the use of appropriate laboratory techniques, followed by specific therapy. Most bacterial and viral conjunctivitis are self-limited, but antimicrobial therapy for the former is advocated to shorten the course, improve patient comfort, prevent recurrence, avoid complications and limit spread to other individuals.

Idiopathic conjunctival granulomas.

A 12-year-old white boy presented with a 1-year history of intermittent bilateral follicular conjunctivitis with yellowish bulbar and limbal nodules and few symptoms. Histopathological examination of conjunctival biopsy specimens showed non-caseating epithelioid cell granulomas with giant cell formation. The lesions partially responded to therapy with topical corticosteroids but persisted for another 4 years and then gradually cleared over the next 5 years. A systemic investigation failed to disclose a specific cause. At the time of writing, the nodules had completely resolved and no associated systemic disease had developed.

Cataract extraction in uveitis: comparison of aphakia and posterior chamber lens implantation.

We reviewed the charts of 39 patients (45 eyes) with uveitis who underwent cataract extraction (intracapsular or extracapsular) with or without implantation of a posterior chamber intraocular lens (IOL) at the Royal Victoria Hospital, Montreal, between 1981 and 1990. The nine eyes with Fuchs' iridocyclitis in which an IOL was implanted had good visual results and few postoperative complications. The 18 eyes with uveitis other than Fuchs' iridocyclitis that received an IOL did not show a greater risk of postoperative complications than those left aphakic (n = 17), and the postoperative visual acuity was comparable to that of the aphakic eyes. Although the numbers are small, we conclude that the presence of uveitis does not automatically exclude posterior chamber pseudophakia.