Ring keratitis from topical anaesthetic misuse

BACKGROUND

Topical anaesthetic abuse is now an established differential diagnosis of ring keratitis. Published evidence suggests that this condition often has a poor prognosis, with the eyes sometimes requiring penetrating keratoplasty or the patient becoming blind.

METHOD

A case of topical anaesthetic abuse and its subsequent management is presented. Ocular examination including pachymetry and specular microscopy is reported.

RESULTS

The cornea made an excellent recovery, allowing a visual acuity of 6/6. Pachymetry showed corneal thickening and specular microscopy demonstrated a decreased cell count in the affected eye.

CONCLUSIONS

With prompt recognition and appropriate treatment the prognosis for these cases can be excellent. However, there is evidence to suggest permanent cellular damage to the endothelium.

LASIK for post penetrating keratoplasty astigmatism and myopia

AIMS

To report the results of a series of patients who were treated with LASIK to correct post penetrating keratoplasty ametropia.

METHODS

26 eyes of 24 patients underwent LASIK to correct astigmatism and myopia after corneal transplantation; 14 eyes also received arcuate cuts in the stromal bed at the time of surgery. The mean preoperative spherical equivalent was -5.20D and the mean preoperative astigmatism was 8.67D.

RESULTS

The results of 25 eyes are reported. The mean 1 month values for spherical equivalent and astigmatism were -0.24D and 2.48D respectively. 18 eyes have been followed up for 6 months or more. The final follow up results for these eyes are -1.91D and 2.92D for spherical equivalent and astigmatism. The patients undergoing arcuate cuts were less myopic but had greater astigmatism than those not. The patients receiving arcuate cuts had a greater target induced astigmatism, surgically induced astigmatism, and astigmatism correction index than those eyes that did not. One eye suffered a surgical complication. No eyes lost more than one line of BSCVA and all eyes gained between 0 and 6 lines UCVA.

CONCLUSIONS

LASIK after penetrating keratoplasty is a relatively safe and effective procedure. It reduces both the spherical error and the cylindrical component of the ametropia. Correction of high astigmatism may be augmented by performing arcuate cuts in the stromal bed.

Staphylococcal infection under a LASIK flap

PURPOSE

To report a staphylococcal infection under a laser in situ keratomileusis (LASIK) flap and to discuss the management of this rare and potentially devastating complication.

METHODS

A patient was referred to our practice having had bilateral LASIK. She was found to have abscesses under the left corneal flap. Staphylococcus aureus was identified as the infecting organism by corneal scrape and treated with appropriate antibiotics. The cornea improved, and then the abscess recurred. The abscess was again scraped and intensive treatment reinstituted.

RESULTS

After successful treatment, the patient recovered excellent visual acuity with only a minimal astigmatic error.

CONCLUSION

The possible reasons for the apparent improvement and then recurrence of the abscess are discussed. The management of this case including the need for corneal scrape and antibiotic prophylaxis is discussed in relation to previously reported cases.

Toric laser in situ keratomileusis for myopic astigmatism using an ablatable mask

BACKGROUND

To assess the results of toric laser in situ keratomileusis (LASIK) correction of myopic astigmatism.

METHODS

A prospective study was performed over a 20 week period for consecutive patients treated for myopic astigmatism. Spectacle-corrected visual acuity, uncorrected visual acuity, spectacle refraction, videokeratography, and complications were recorded. Vector analysis was performed by the ASSORT program.

RESULTS

Sixty-five eyes of 42 patients underwent toric LASIK with a Summit Technologies Apex Plus excimer laser. Mean preoperative spherical equivalent refraction at the spectacle plane was -6.24 +/- 2.42 D (range, -1.63 to -14.63 D) and mean pre-operative refractive cylinder magnitude was 1.99 +/- 1.35 D (range, 0.75 to 7.00 D); mean attempted refractive cylinder correction was 1.90 +/- 1.00 D. Six months after LASIK (43 eyes followed), mean spherical equivalent refraction at the spectacle plane was -0.40 +/- 0.55 D and 31 eyes (72.1%) were within +/- 0.50 D of emmetropia. At 6 months, mean refractive cylinder magnitude was 0.74 +/- 0.70 D, mean surgically induced astigmatism was 1.46 +/- 0.86 D, mean absolute angle of error was 10.33 degrees, mean astigmatic correction index was 0.93 +/- 0.36 D, and mean index of success was 0.46 +/- 0.39. Uncorrected visual acuity was 6/12 or better in 34 eyes (79.1%) and 6/6 in 15 eyes (35%); spectacle- corrected visual acuity was 6/9 or better in 41 eyes (95.35%). Six eyes (14.0%) lost 1 line of spectacle-corrected visual acuity at 6 months and one eye (2.3%) lost 2 lines. Ten eyes (23.3%) gained 1 line at 6 months.

CONCLUSION

Toric LASIK with an ablatable mask using the Summit Apex Plus excimer laser is a safe and relatively accurate procedure for the correction of myopic astigmatism.

Central Focal Interface Opacity After Laser in situ Keratomileusis

BACKGROUND

The acute onset of a focal central interface opacity with visual loss following LASIK has not been described in the peer reviewed literature. Non-peer reviewed reports of various inflammatory lesions have been recorded.

METHODS

We describe three cases in which an acute focal stromal interface opacification was identified within 1 week of laser in situ keratomileusis (LASIK). Each case was performed by a different surgeon on a different day, but using the same method, materials, and the Summit Apex Plus excimer laser. Immediately after surgery, all eyes were normal with good unaided vision. The appearance of the central stromal opacity was associated with acute visual deterioration. Preoperative and postoperative cycloplegic refractions, videokeratography, and postoperative slit-lamp biomicroscopy were performed. Each case was treated with intensive topical corticosteroids.

RESULTS

Each case demonstrated a central circular opacity in the interface between corneal flap and stromal bed, with associated variable stromal thinning. Resolution of the pathological process followed 2 to 4 weeks of treatment with topical corticosteroids and subsequent improvement in slit-lamp biomicroscopy, corneal topography, and vision. Etiology was uncertain.

CONCLUSION

Central interface opacification is a rare but visually important inflammatory complication of LASIK.

Different excitation-contraction coupling mechanisms exist in squid, cuttlefish and octopod mantle muscle

Excitation-contraction (EC) coupling was studied in central zone mantle muscle fibres of a squid (Alloteuthis subulata), a cuttlefish (Sepia officinalis) and an octopod (Eledone cirrhosa). Thin slices of muscle were used for twitch experiments and enzymatic isolation of single fibres for whole-cell patch-clamp studies. The current required for a supramaximal twitch response during direct stimulation of muscle slices was lower for squid than for cuttlefish. In squid, but not in cuttlefish, the current-response relationship was independent of slice thickness (range 0.1-0.5 mm). Twitches of squid and cuttlefish slices were reversibly abolished by removal of extracellular Ca2+. In squid, but not in cuttlefish, the current-response relationship was Na+-dependent, and in the absence of Na+ higher current strengths were required to generate a supramaximal response. In whole-cell voltage-clamp experiments on isolated muscle fibres from squid, cuttlefish and Eledone cirrhosa, a sustained inward current was recorded upon depolarisation. This current was blocked by 5 mmol l-1 Co2+ and suppressed by 10 micromol l-1 nifedipine. In squid, an additional inward fast-activating transient current was seen which was blocked by 2 micromol l-1 tetrodotoxin and depolarised holding potentials. The fast current represents a voltage-activated Na+ channel, and the slow currents represent L-type Ca2+ channels. We conclude that squid possess a specialised rapid EC coupling mechanism in central zone fibres that is absent in cuttlefish and Eledone cirrhosa.

Retreatment of undercorrected photorefractive keratectomy for myopia

Fourteen eyes treated by photorefractive keratectomy (PRK) for myopia required retreatment because of undercorrection. The mean preoperative refraction of these eyes had been -9.82 D (range 5.25 to 17.13). No eyes before photorefractive keratectomy had low myopia, three eyes had myopia between -3.10 and -6.00 D, four were between -6.10 and -10.00 D, and seven had more than -10.00 D of myopia. Retreatment was required for manifest scars in association with regression, unresponsive to topical corticosteroids. The retreatments were performed using a Summit ExciMed UV200LA excimer laser with a dual ablation technique utilizing a phototherapeutic keratectomy followed by a photorefractive keratectomy. Follow-up ranged from 1 to 9 months. Eight eyes followed more than 3 months had a mean spherical equivalent refraction of -0.58 D (range -7.35 to +1.25).

Photorefractive keratectomy for myopia of more than -10 diopters

Twenty-seven consecutive eyes of 18 patients with myopia of more than -10.00 diopters (D) were treated by photorefractive keratectomy (PRK) using the ExciMed UV200LA excimer laser and a double ablation technique in an attempt to achieve a refraction of plano. The preoperative mean spherical equivalent refraction was -13.32 D (standard deviation 2.54, range -10.25 to -20.50). Preoperative spectacle corrected visual acuity ranged from 6/6 to 6/60 and one eye had had two previous refractive keratotomies. Follow up ranged from 3 to 15 months (mean 8.9). At 6 months after surgery, the mean change in refraction was 11.03 D, from a preoperative mean of -13.32 D to a postoperative mean of -2.29 D. The mean keratometric flattening was 5.83 D, from a preoperative mean of 42.92 D to a postoperative mean of 39.09 D. The reason for this large difference is uncertain. At three months the mean spherical equivalent refraction was +0.07 D (SD 2.94, range -10.50 to +3.25). The 14 eyes that had achieved 12 months follow up had a mean spherical equivalent of -1.91 D (SD 3.87, range -11.00 to +2.50). Seven of these 14 eyes have been reablated for manifest scars in association with regression. All 14 eyes had best spectacle corrected visual acuity at or better than their preoperative level.

Localisation of the mitogenic epitope of staphylococcal enterotoxin B

Limited digestion of staphylococcal enterotoxin B (SEB) with trypsin resulted in the generation of a 12-Kda amino-terminal fragment and a 17-Kda carboxy-terminal fragment which were isolated by preparative iso-electric focusing. The carboxy-terminal fragment exhibited significant mitogenic activity for murine splenocytes, whereas the isolated amino-terminal fragment possessed little detectable mitogenic activity. Monoclonal antibodies (MAbs) specific for the carboxy-terminal fragment neutralised most of the mitogenic activity of both the intact toxin and the carboxy-terminal fragment. MAbs specific for the amino-terminal fragment had no detectable neutralising activity. These results support the hypothesis that the epitope(s) responsible for mitogenic activity is located in the carboxy-terminal region of SEB.

Calmodulin is associated with microtubules forming in PTK1 cells upon release from nocodazole treatment

To investigate the association of calmodulin (CaM) with microtubules (MTs) in the mitotic apparatus (MA), the distributions of CaM and tubulin were examined in cells in which the normal spindle organization had been altered. A fluorescent CaM conjugate with tetramethylrhodamine isothiocyanate (CaM-TRITC) and a dichlorotriazinyl aminofluorescein conjugate with tubulin (tubulin-DTAF) were injected into cells that had been treated with the MT inhibitor nocodazole. With moderate nocodazole concentration (0.3 micrograms/ml, 37 degrees C, 4 h) in live cells, CaM-TRITC and tubulin-DTAF concentrated identically on or near the centrosomes and kinetochores. In serial sections of these cells, small MT segments were observed by transmission electron microscopy (TEM) in the regions where fluorescent protein had concentrated. When a higher drug concentration was used (3.0 micrograms/ml, 37 degrees C, 4 h), no regions of CaM-TRITC or tubulin-DTAF localization were observed, and no MTs were observed when serial sections were examined by TEM. However, following release from the high-concentration nocodazole block, CaM-TRITC colocalized with newly formed MTs at the kinetochores and centrosomes. Later in the recovery period, when chromosome-to-pole fibers had formed, CaM association with kinetochores diminished, ultimately attaining its normal pole-proximal association with kinetochore MTs in cells that progressed through mitosis. We interpret these observations as supporting the hypothesis that in the MA, CaM attains a physical association with kinetochore MTs and suggest that CaM-associated MTs may be inherently more stable.

Calmodulin stabilization of kinetochore microtubule structure to the effect of nocodazole

To investigate the function of calmodulin (CaM) in the mitotic apparatus, the effect of microinjected CaM and chemically modified CaMs on nocodazole-induced depolymerization of spindle microtubules was examined. When metaphase PtK1 cells were microinjected with CaM or a CaM-TRITC conjugate, kinetochore microtubules (kMTs) were protected from the effect of nocodazole. The ability of microinjected CaM to subsequently protect kMTs from the depolymerizing effect of nocodazole was dose dependent, and was effective for approximately 45 min, with protection decreasing if nocodazole treatment was delayed for more than 60 min after injection of CaM. The CaM-TRITC conjugate, similar to native CaM, displayed the ability to activate bovine brain CaM-dependent adenylate cyclase in a Ca++-dependent manner and showed a Ca++-dependent mobility shift when subjected to PAGE. A heat-altered CaM-TRITC conjugate also protected kMTs from the effect of nocodazole. However, this modified CaM was not able to activate adenylate cyclase nor did it display a Ca++-dependent mobility shift when electrophoresed. In a permeabilized cell model system, both CaM analogs were observed to bind to the spindle in a Ca++-independent manner. In contrast, a performic acid-oxidized CaM did not have a protective effect on spindle structure when microinjected into metaphase cells before nocodazole treatment. The oxidized CaM did not activate adenylate cyclase and did not exhibit Ca++-dependent mobility on polyacrylamide gels. These results are interpreted as supporting the hypothesis that CaM binds to the mitotic spindle in a Ca++-independent manner and that CaM may serve in the spindle, at least in part, to stabilize kMTs.

Macular suprastructure, stereociliary bonding and kinociliary/stereociliary coupling in rat utricular macula

This report considers rat utricular macular suprastructure after chemical treatment with the sodium salt of N,N-Naphthaloylhydroxylamine (NHA), used alone or in combination with tannic acid (TA). NHA and TA preserve calcium and complex carbohydrate-protein molecules, respectively. Macromolecules of supramacular substance appear comparable morphologically to material of the external lamina of glycocalyx. Similar material crosslinks stereocilia with approximately equal to 58 nm periodicity and couples parts of kinocilia with specific stereocilia. Particles which occur within kinocilia at certain attachment sites connect to dynein arms of the kinocilia. Interstereociliary connections are aligned with internal linkers to actin. Thus, a basis for dynamic communication between kinocilia and stereociliary actin has been shown. The mechanism would appear to be calcium dependent. The findings support the concept that kinocilia are motile and lead to the stereociliary tuft in vestibular hair cells.

Pharmacokinetics of antituberculosis drugs in patients

The pharmacokinetics of rifampin, isoniazid, and ethambutol were determined in 26 ambulatory male patients (aged 49.5 +/- 9.9 yr) with tuberculosis. Rifampin and isoniazid were given individually or together, with or without ethambutol; studies were done after a single dose and after chronic administration. Under the study conditions, with large variability in the extent of disease and physical status and history of alcohol and tobacco abuse and narrow age range, the pharmacokinetics of these three antituberculosis drugs were not modified significantly by patient age. Furthermore, appreciable drug-drug interactions did not occur when the three drugs were administered concurrently. Self-induction of rifampin clearance by chronic dosing with the drug may lead to subtherapeutic levels of rifampin. Administration of isoniazid and ethambutol in two divided doses resulted in peak plasma concentrations below the accepted therapeutic levels of the two drugs. Our findings indicate that at least in the middle-aged patients with tuberculosis, the current single daily dose, multiple-drug regimen is therapeutically sound pharmacokinetically, and clinicians do not have to make adjustments in dosages of these drugs for age and the extent of disease.

Innervation patterns in rat saccular macula. A structural basis for complex sensory processing

Serial sections through the anterior part of rat saccular macula were reconstructed as montages. Findings are that type II hair cells are integrated into the neural circuitry of type I cells, chiefly by synapses with neighboring calyces and their collaterals; and that complex interactions between afferent- and efferent-type nerve elements take place. Three basic types of nerve/calyx pattern are present: U-type nerves lose their myelin before they enter the macula and have complex calyces with several collaterals; M-type nerves are myelinated up to the calyx, which lacks collaterals; and M/U-type nerves have short, unmyelinated segments proximal to their calyces, which have few collaterals. Both afferent- and efferent-type collaterals spring from calyces, chiefly from those of U-type nerves. Type II cells are presynaptic both to electron-lucent and to vesiculated terminals; some synapses are reciprocal. Electron-lucent boutons sometimes are presynaptic to calyces and to type II hair cells; and morphologically afferent-to-afferent kinds of synapses occur in the neuroepithelium. The anatomical findings indicate that complex information processing must occur in mammalian gravity receptors.

Induction of suppressor cells in vitro by Candida albicans

Normal splenocytes cultured with Formalin-killed Candida albicans were shown to acquire significant suppressor cell activity in a period of 3 days. These cells were found to suppress both the phytohemagglutinin-induced mitogen response as well as the anti-sheep erythrocyte antibody response. Experiments were carried out to determine the nature of the suppressor cell population. Results showed that these cells were not susceptible to treatment with anti-Thy 1 antibody and complement. Panning experiments showed that the suppressor cells were not plastic-adherent or Mac-1 antigen-positive. The suppressor cells were, however, adherent to anti-mouse immunoglobulin (F(ab')2-fragment)-coated dishes. Additional experiments showed that the suppressor cell activity was susceptible to treatment with monoclonal anti-Lyb 2.1 antibody and complement. These results suggest that the suppressor cell induced in vitro by Candida is a member of the B-lymphocyte lineage.

Microinjected ras family oncogenes stimulate DNA synthesis in quiescent mammalian cells

Oncogenes of the ras family stimulate DNA synthesis when microinjected into quiescent mouse and hamster fibroblasts, as detected by in situ autoradiography. The molecularly cloned genomes of Harvey and Kirsten sarcoma viruses, the cloned Harvey ras gene, and the product of the v-ras gene, the p21v-rasH protein, stimulate DNA synthesis in quiescent cells. This stimulation is comparable to the stimulatory activity of the microinjected SV40 T-antigen-coding gene. The demonstration that these oncogenes can stimulate transient DNA synthesis in quiescent cells is relevant to understanding the mechanism by which these genes are able to transform cells in vitro and induce tumors in animals.

Effects of Wy-18,251 (3-p-chlorophenyl)thiazolo[3,2-a]benzimidazole- 2-acetic acid), levamisole and indomethacin on the generation of murine T suppressor cells in vitro

In vitro culture of normal BALB/c spleen cells with staphylococcal enterotoxin B (SEB) activates antigen non-specific suppressor T cells (Ts) which can be assayed by their ability to suppress antibody production in a plaque assay. Addition of the experimental immunomodulatory drug Wy-18,251 (10-100 microM) to cultures of spleen cells plus SEB significantly increased Ts activity relative to cultures without the drug. Similar results were obtained with levamisole, but, in contrast, indomethacin (0.1-10 microM) inhibited SEB-induced suppressor cell activity. The ability of Wy-18,251 to augment Ts activity could be therapeutically useful in the treatment of those autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus, in which hyperactive B cell function is a characteristic feature.

T4 phage-coded dihydrofolate reductase. Subunit composition and cloning of its structural gene

The structures of phage-coded dihydrofolate reductases are of interest because of 1) possible relationship to plasmid-coded dihydrofolate reductases; 2) unusual regulation of enzyme synthesis; and 3) multiple roles and intermolecular interactions involving the protein. To prepare for primary structural studies, we have cloned the T4 frd gene, which codes for dihydrofolate reductase, and we have determined for redetermined some physical properties of the enzyme. The native enzyme has a molecular weight of about 44,500, as determined by sedimentation velocity and gel filtration, and a subunit molecular weight of about 23,000, as determined by aminopterin titration and denaturing gel electrophoresis. We conclude that the enzyme is a dimer, with each subunit containing one methotrexate-binding site. A 1.1-kilobase pair fragment from a HindIII restriction digest of cytosine-substituted T4 DNA was cloned into pBR322, and recombinants were identified by trimethoprim resistance. Cells carrying this recombinant plasmid produce both the host cell and phage-coded dihydrofolate reductases.