Ophthalmic drops causing coma in an infant

A 1-month-old infant with Peters anomaly had recurrent episodes of unresponsiveness, hypotension, hypotonia, hypothermia, and bradycardia. An extensive medical evaluation determined these episodes to be caused by brimonidine, an anti-glaucoma agent. There is the potential for serious toxic effects from the systemic absorption of topically applied ophthalmic agents in children.

Assessment of ophthalmology residents' contact lens training

PURPOSE

To characterize the nature and duration of contact lens training in ophthalmology residency training programs and to ascertain the comfort level of residents in fitting various types of contact lenses and in dealing with common contact lens-related complications.

METHODS

Surveys were mailed to 126 ophthalmology residency program directors/coordinators and requested to be distributed to 1,381 ophthalmology residents. The questionnaire addressed issues related to contact lens training, hours of clinical and didactic training, comfort with fitting a variety of different types of contact lenses and dealing with common contact lens-related complications, and plans for incorporation of contact lens dispensing into future practice.

RESULTS

Two hundred and forty-nine residents (18%) responded from 84 programs (67%). Most programs (87%) have some form of supervised contact lens training, frequently conducted by an optometrist (61% of programs), that consists of 20 hours or less of clinical experience and 20 hours or less of didactic training. A majority of the responding graduating residents (66%) feel comfortable fitting spherical soft contact lenses, while less than half of all residents feel comfortable fitting any other type of contact lens. In addition, most residents (65%) feel comfortable diagnosing and treating common contact lens-related complications.

CONCLUSIONS

Most ophthalmology residency programs offer some form of supervised contact lens training which allows a majority of residents to feel comfortable fitting only spherical soft contact lenses, while also dealing comfortably with most contact lens-related problems. A comparison with previous data suggests increasing comfort with fitting most types of contact lenses over the last decade.

Photoastigmatic Refractive Keratectomy in Myopes

PURPOSE

Photoastigmatic refractive keratectomy (PARK) was studied in a multi-center clinical trial. The Nidek EC-5000 excimer laser was evaluated for its effect on refraction, visual acuity, and safety measures as part of a U.S. Food and Drug Administration (FDA) regulated study.

METHODS

Eight U.S. centers enrolled adults with eyes having refractive astigmatism up to 4.00 D and a myopic spherical equivalent refraction up to -8.00 D. Results are reported for 749 eyes of 486 patients with at least 6 months follow-up. The rectangular beam scanning Nidek EC-5000 used a 5.5-mm-diameter treatment zone, a 7.0-mm-diameter peripheral blend zone, and a 40 Hz pulse rate for surface treatment of myopic astigmatism. Nomogram corrections to machine settings were required to achieve the desired results.

RESULTS

Preoperative average spherical equivalent refraction of -4.90+/-1.74 D was reduced to -0.02+/-0.79 D at 6 months. Refractive stability was established at 3 months. Over 62% of eyes were within +/-0.50 D of desired correction at 6 months, with over 86% within +/-1.00 D. Uncorrected visual acuity improved by an average of 10 Snellen lines; over 64% of eyes saw 20/20 or better uncorrected and over 93% saw 20/40 or better uncorrected at 6 and 12 months. PARK treatment effectively reduced astigmatism with little average axis error or magnitude error. Corneal haze and safety concerns were minimal.

CONCLUSIONS

Photoastigmatic refractive keratectomy using the Nidek EC-5000 excimer laser provided significant reduction of myopia and astigmatism, with minimal complications.

Sterile interface keratitis associated with micropannus hemorrhage after laser in situ keratomileusis

Numerous etiologies have been suspected to lead to sterile interface keratitis after laser in situ keratomileusis. This tan interface haze with a rippled appearance has been called Sands of the Sahara. We present 2 cases in which red blood cells entered the interface after a small hemorrhage from peripheral corneal vascularization during the microkeratome pass. Although this bleeding was controlled and all visible blood cells were removed at surgery, both patients developed the appearance of a focal interface keratitis on the first postoperative day.

Sterile interface keratitis after laser in situ keratomileusis: three episodes in one patient with concomitant contact dermatitis of the eyelids

PURPOSE

To illustrate a case in which sterile interface keratitis after laser in situ keratomileusis (LASIK) occurred concomitantly with an allergic contact dermatitis of the eyelids.

METHODS

Retrospective case review.

RESULTS

Resolution of the interface keratitis and dermatitis occurred following an intense course of topical corticosteroids and brief course of oral corticosteroids. Despite an attempt to eliminate potential causes, the same patient developed interface keratitis in the fellow eye following both the initial LASIK and an enhancement, in which no microkeratome was used. Intense treatment with both topical and oral corticosteroids led to a final uncorrected visual acuity of 20/20 in the right eye and 20/25+2 in the left eye.

CONCLUSION

The etiology and mechanism of sterile interface keratitis after LASIK are unknown, but are probably multifactorial. The concomitant contact dermatitis reaction may indicate a common immune mechanism.

Evaluation of prior photorefractive keratectomy in donor tissue

PURPOSE

To describe a case in which an eye donor had prior bilateral photorefractive keratectomies and to elucidate possible methods of evaluation and screening of donor tissue.

METHODS

Case report. A 62-year-old eye donor was reported to have received radial keratotomy before his death. Further investigation by the eye bank showed a history of photorefractive keratectomy (PRK), not radial keratotomy. The corneas were therefore not used for transplantation, and the eyes were evaluated by slit-lamp examination, photography, corneal topography, and histology.

RESULTS

Slit-lamp and photographic examination did not indicate the presence of PRK ablations. Corneal topography mapping with the TMS-1 was relatively ambiguous for identifying PRK flattening, while multiple data formatting of the cornea with the Orbscan resulted in the strongest suggestion of prior PRK. Histologic analysis showed central corneal thinning and loss of Bowman's membrane consistent with PRK.

CONCLUSIONS

In the absence of a positive donor history for PRK, current methods of screening donor tissue for prior PRK often are insufficient to exclude these corneas from use in transplantation. More refined placido imagery corneal topography or newer technologies such as the Orbscan may allow more sensitive and specific methods of donor tissue screening.

Expanding the scope of lamellar keratoplasty

PURPOSE

To investigate whether applications of current technology, such as cryolathe and excimer laser, might improve outcomes and increase use of lamellar keratoplasty.

METHODS

Six studies were performed, beginning with animals and progressing to human subjects. The first study compared cryolathed with hand-dissected rabbit corneas to ascertain which created a smoother donor interface. The second animal pilot study was done to determine whether thickness of donor cornea resection could be accurately predicted with the cryolathe. A prospective animal trial was then undertaken to compare lamellar keratoplasty outcomes using cryolathed versus hand-dissected tissue. The fourth work extrapolated previous animal findings to lamellar keratoplasty in human disease. Finally, two ongoing studies are described. The first explores the possibility of sutureless lamellar keratoplasty. The second utilizes the excimer laser to dissect the recipient stromal bed.

RESULTS

The initial animal pilot study demonstrated a clearer stromal surface in cryolathed versus hand-dissected corneal tissue. The second pilot showed that plano-powered donor tissue could be generated to predetermined thickness. The prospective animal trial revealed that clear grafts of intended thickness could be obtained with cryolathing. Human studies suggested that lamellar keratoplasty using cryolathe-prepared donor tissue may offer superior results to free-hand dissection. Finally, one ongoing study indicates that sutureless lamellar keratoplasty is untenable, and the other shows that clear grafts can be obtained by combining cryolathed donor tissue with recipient photoablation.

CONCLUSION

This body of work demonstrates that use of new lamellar keratoplasty technology may offer expanded scope and better outcomes than traditional lamellar keratoplasty techniques.

Long-term Effects of Radial Keratotomy on the Corneal Endothelium

BACKGROUND

The long-term effects of radial keratotomy on the corneal endothelium are not well understood. We evaluated the effects of radial keratotomy on the corneal endothelium on the central and midperipheral corneal endothelium.

METHODS

Anterior radial keratotomy in 25 eyes was performed and patients were followed for a duration of 4 to 10 years after surgery. Eleven non- contact lens wearing control eyes did not have surgery and were followed for the same period. Morphometric analysis of specular microscopic images was performed with regard to cell density, percent hexagonality, and coefficient of variation.

RESULTS

Mean corneal endothelial cell loss rates were 0.4% per year in the radial keratotomy group and 0.9% in the untreated control group over the study duration (mean 7 yr). Morphometric analysis of the cells failed to show a significant change in hexagonality and coefficient of variation. Evaluation of the midperipheral corneal cell counts demonstrated a 1% per year cell loss rate. The cell loss rates in radial keratotomy patients followed over this period were consistent with that noted for normal aging (0.5 to 2.5% per year).

CONCLUSION

Radial keratotomy does not cause accelerated endothelial cell loss over 4 to 10 years.

Trauma and alkali burns induce distinct patterns of cytokine gene expression in the rat cornea

Cytokines such as the interleukins (IL) and tumor necrosis factor alpha (TNF alpha) have traditionally been associated with paracrine regulation of immune reactions. These proteins also have properties suggestive of functional roles in the inflammatory and reparative responses to tissue injury. In this study, mRNA levels for IL-1 alpha, IL-1 beta, IL-6, TNF alpha, interferon gamma, transforming growth factor beta 1, and CD4 were monitored in rat corneas at times from 1 hour through 2 weeks after incisional trauma or alkali burns. Transcripts for IL-1 alpha, TNF alpha, and TGF beta 1 were present in most corneal samples; whereas those for IFN gamma and CD4 were not detected. As early as 1 hour following either of these non-immunologic forms of injury, expression of IL-6 mRNA levels was induced. Only in corneas with alkali burns did IL-6 induction persist from days 1 through 7. The alkali-injured corneas also had markedly increased IL-1 beta mRNA levels from days 1 through 7. These observations indicate that cytokine mRNA is induced in the cornea by trauma without an apparent immunologic stimulus. Our data are consistent with the hypothesis that corneal tissues respond to different types of injury with different patterns of cytokine gene expression.

Survival of streptococcus in optisol-GS medium

BACKGROUND

Donor cornea contamination as a cause of endophthalmitis is one of the most serious complications of penetrating keratoplasty. Optisol-GS corneal storage medium with the combination of gentamicin and streptomycin was designed to provide wider antibiotic coverage, most notably against streptococcal species. However, many enterococci are resistant to streptomycin and genta micin.

METHODS/RESULTS

We report a case in which Enterococcus faecium was isolated from cultures of the donor limbus prior to corneal excision and again from preoperative cultures of the donor corneal rim despite 5 days of preservation in Optisol-GS. The isolate was found to be resistant to both gentamicin and streptomycin.

CONCLUSIONS

This case illustrates the need to raise awareness that streptococcus can remain a viable contaminant of donor corneas despite storage in Optisol-GS medium.

The treatment of persistent wound leak after radial keratotomy

BACKGROUND

Macroperforation of the cornea during refractive keratotomy can result in persistent wound leak and may need treatment by suturing.

METHODS

We describe two eyes that developed a macroperforation during radial keratotomy with persistent leakage of aqueous. The wounds were sutured with 10-0 and 11-0 nylon sutures.

RESULTS

The sutures induced irregular astigmatism as shown by corneal topography. Removal of sutures improved the topography and led to an acceptable outcome.

CONCLUSION

Macroperforations with persistent aqueous leaks should be sutured. Suture removal within a few weeks after surgery can avoid persistent irregular astigmatism and lead to a good refractive result.

The influence of basic fibroblast growth factor on cat corneal endothelial wound healing in vivo

Using standardized freeze wounds in cat corneas, we tested the efficacy of basic Fibroblast Growth Factor (bFGF) solubilized in phosphate buffered saline (PBS) to promote endothelial healing when injected intraocularly at doses ranging from 0.01 microgram to 10 micrograms. After 6 days, animals were humanely sacrificed and corneal tissues were fixed and stained for light microscopy and computation of remaining wound areas. A significant dose-response relationship was found between the dosages of 0.01, 0.1, and 1.0 microgram of bFGF/eye and the stimulation of more completely healed endothelium six days after transcorneal freeze wounding. Significantly larger endothelial wounds were present six days after wounding when the eyes were treated with 10 micrograms of bFGF/eye compared with controls treated with PBS only.

The influence of epidermal growth factor on cat corneal endothelial wound healing

Using standardized freeze wounds in cat corneas, we tested the efficacy of human recombinant Epidermal Growth Factor (EGF) to promote endothelial healing when solubilized in either phosphate buffered saline (PBS), 1% methylcellulose (MC), or sodium hyaluronate (NaHA), in final intraocular doses ranging from 2 micrograms to 100 micrograms of EGF. After 6 or 7 days' healing, animals were humanely sacrificed and corneal tissues were fixed and stained for light microscopy and computation of remaining wound areas. EGF in NaHA in final intraocular doses of 2 and 10 micrograms prompted significantly more complete healing of transcorneal freeze wounds to endothelium compared with endothelium of eyes treated with NaHA control solution alone. EGF in PBS or in MC in doses ranging from 2-100 micrograms/eye did not promote more complete wound healing than that seen in eyes treated with their respective vehicle solutions alone. All vehicle solutions were associated with similar degrees of wound healing, implying that they have no intrinsic healing properties.

Stimulation of corneal endothelial wound healing in cats by mesodermal growth factor

Several growth factors have been evaluated for their effects on corneal wound healing but few studies have yet demonstrated an acceleration of endothelial repair in vivo. Mesodermal Growth Factor (MGF) was tested in vivo by making standardized freeze wounds in cat corneas and immediately injecting one of four concentrations of MGF in sterile phosphate buffered saline (PBS), or PBS alone, into the anterior chamber. Seven days later, the animals were sacrificed and the corneas excised and stained. Descemet's membrane and endothelium were dissected and mounted onto glass slides. The wound areas were photographed, measured and compared statistically. Those cats receiving the three lowest doses of MGF had significantly smaller wounds than controls (p less than 0.05).

Conjunctival goblet cell response to vasoconstrictor use

Vasoconstrictors such as phenylephrine and naphazoline are used in ophthalmology to decrease hyperemia associated with allergic conjunctivitis and contact lens wear. There is a suspicion, however, that chronic use of these agents can produce dry-eye symptoms in some patients. The purpose of this study was to determine whether vasoconstrictor use interferes with tear film adequacy by decreasing mucin-secreting goblet cells. Cellulose acetate filter strip impressions were taken from the bulbar conjunctiva of rabbit eyes treated with vasoconstrictors or artificial tears for varying periods of time, and the number of goblet cells per light microscopic field counted. There was no significant difference between the number of goblet cells in control and vasoconstrictor-treated animals within each time period. These results indicate that conjunctival goblet cell density is not significantly affected by topical vasoconstrictor use.

The effects of hard and soft contact lenses on the corneal endothelium

We examined the morphologic characteristics of the corneal endothelium in three groups of contact lens wearers: those who had used daily-wear soft contact lenses for an average of 6.3 years, long-term (greater than 20 years) users of hard contact lenses, and former users of hard contact lenses who had worn them for an average of 9.6 years but who had discontinued them for an average of 4.3 years. When compared to age-matched controls, all groups had similar endothelial cell densities but demonstrated significant increases in variation of cellular size (polymegethism) and shape (pleomorphism). We found that daily-wear soft contact lenses can cause endothelial polymegethism and pleomorphism similar to those caused by hard contact lenses and that the endothelial changes induced by hard contact lenses are more profound with greater duration of wear and are apparently not completely reversible.

Recurrent erosion. Treatment by anterior stromal puncture

The majority of patients with recurrent corneal erosion respond to conventional forms of therapy such as topical lubricants, patching, debridement, or bandage soft contact lenses. However, there remain a small number who do not. For the small number of patients who do not respond to this type of treatment, this report describes a procedure: multiple anterior stromal punctures are created that presumably stimulate more secure epithelial adhesion to the underlying stroma. Of 21 eyes in 18 patients treated in this manner, three eyes required retreatment of adjacent areas; otherwise, there were no recurrences in follow-up periods ranging from 5 months to 12 years. This procedure is a simple and effective method for safe office treatment of patients with recalcitrant recurrent erosion.

The effect of radial keratotomy on the corneal endothelium

Morphometric analysis of the corneal endothelium was performed on 11 eyes of patients who underwent anterior radial keratotomy with the contralateral eye serving as the controls. We analyzed cell density, variation in cell size (polymegethism), and cell shape (pleomorphism) by computer analysis of central and midperipheral specular micrograms one year after surgery. The central endothelial density decreased from 2,503 to 2,419 cells/mm2 (3.3% decrease). The coefficient of variation in cell size (polymegethism) was 0.290 preoperatively and 0.309 postoperatively centrally. Central hexagonality was reduced centrally from 61.4% preoperatively to 56.8% in the operated on eye. These differences were not statistically significant (P greater than .05). In a separate subgroup of six patients, midperipheral specular microscopy under and between incisions disclosed a similar pattern of mild cell density decrease and morphometric remodeling one year after surgery. No morphometric characteristic was significantly different from the central control values (P greater than .05), suggesting that the corneal endothelial monolayer had stabilized one year after radial keratotomy.

Keratocyte survival in keratophakia lenticules

Keratocyte survival in corneal lenticules preparing by cryolathing was evaluated using the vital stain, nitroblue tetrazolium. A comparison was made between lenticules inserted in the recipient cornea immediately after grinding and those inserted after one week of storage in either glycerin or liquid nitrogen. In all three groups, no viable keratocytes stained in the donor lenticule at one or three days after surgery. Ten days after insertion, however, all three groups showed a few staining cells within the body of the lenticule, suggesting beginning repopulation of the donor collagenous framework with viable cells from the host. Since the donor keratocytes are dead, healing of keratophakia lenticules is not influenced adversely by storing the donor material. Thus, keratophakia lenticules could be prepared in advance of surgery and stored in glycerin or liquid nitrogen until needed.

A technique for preparing corneal lamellar donor tissue using simplified keratomileusis

A technique is described for producing lamellar buttons from donor corneas using modified keratomileusis. Although refractive keratoplasty is complex, producing planopower corneal discs is much simpler. Accuracy in preparing lamellar tissue of known thickness is potentially greater with keratomileusis than free-hand dissection and should produce better visual results. Eye banks could store precut lamellar buttons in various thicknesses and thereby decrease the amount of time spent in the operating room during lamellar keratoplasty.

Keratophakia using preserved lenticules

Using cats as an experimental model, we compared the clarity of fresh, glycerine-preserved and nitrogen-preserved lenticules (corneal stromal implants) in keratophakia. No difference in final clarity was observed and the change in corneal curvature was maintained. In six patients freshly cut lenticules were used; in nine patients liquid nitrogen-preserved lenticules were used. Again, no difference in final clarity or correction was noted. The use of preserved, precut tissue in keratophakia will make this technique available to the general ophthalmic surgeon.

Stimulation of corneal wound healing with mesodermal growth factor

Mesodermal growth factor (MGF) from mouse submaxillary glands was tested in vivo for stimulating effects on corneal wounds in rabbits. Intrastromal injection of 5 microgram of MGF induced widespread fibroblast activity and stromal cell division, and markedly stimulated stromal healing. At high doses (greater than 25 microgram), corneal destruction was indicated by extensive necrosis and perforation. When low doses (1 to 5 microgram) of MGF were applied to the lip of nonperforating knife wounds of the cornea, three major differences were noted between control and experimental wounds. In wounds treated with MGF, the depth of stromal healing was greater, as was the intensity of the fibroblast activity, and the width and depth of the epithelial plug were significantly decreased. These results establish that MGF is an effective growth-stimulating agent in vivo and that the initial stages of corneal wound healing may be accelerated in vivo.