Amparo Navea

Excimer laser photorefractive keratectomy for high myopia

Abstract One hundred and thirty‐three eyes of 103 patients had photorefractive keratectomy with a slit scan mode excimer laser for myopia ranging from −6.00 to −22.00 diopters (D). The epithelium was removed with 20% ethanol, and the ablation was done with a tapered profile surrounding the optical zone. Patients were divided into two groups based on preoperative myopia: Group A, −6.00 D to −12.00 D (88 eyes); Group B, −12.50 D to −22.00 D (45 eyes). In Group A, mean preoperative refraction was −9.59 ± 1.79 D. Mean postoperative refraction was −0.29 ± 1.47 D at one month, −0.85 ± 1.68 D at three months, −1.17 ± 2.04 D at six months, and −0.56 ± 0.74 D at one year. Anterior stromal haze was greatest at the end of the first month; it diminished thereafter. This haze did not reduce the best corrected visual acuity in any eye in Group A. Mean preoperative refraction in Group B was −14.69 ± 5.27 D. Mean postoperative refraction was −1.34 ± 2.02 D at one month, −0.76 ± 2.08 D at three months, −3.88 ± 2.32 D at six months, and −5.50 ± 5.00 D at one year. Three eyes in Group B lost one or two lines of best corrected visual acuity as a result of severe stromal haze and epithelial scarring. Group A’s results were similar to those obtained in eyes with low myopia. In Group B, although a percentage of eyes obtained fairly good results, the lower degree of predictability and large variation in the results suggest that using this technique is unadvisable in eyes with extremely high myopia except in selected cases.

High dose intravitreal foscarnet in the treatment of cytomegalovirus retinitis in AIDS.

The efficacy and tolerance of high dose intravitreal foscarnet for cytomegalovirus retinitis in patients with AIDS was studied. Foscarnet in a dose of 2400 micrograms was injected directly into the vitreous of 11 patients (15 eyes). Five patients had active retinitis (eight eyes, 53.3%), and received a 3 week induction therapy of six injections as the first step. Six patients had initial inactive retinitis (seven eyes, 46.7%), and received only maintenance therapy which consisted of a weekly injection. The main indications for intravitreal therapy were: myelosuppression, kidney toxicity, catheter related sepsis, or refusal of intravenous therapy. The patients were followed for a mean period of 16 weeks (range 8-28 weeks) and received a total of 304 injections. Vitreous foscarnet levels were measured by high performance liquid chromatography. After a 3 week course of induction therapy, complete resolution of the active retinitis was seen in 62.5% (5/8 cases), while 37.5% (3/8 cases) had partial resolution. No cases failed to respond or progress. The rate of relapse on maintenance therapy was 33% (five of 15 eyes) by 20 weeks, and two of these eyes did not respond to reinduction and progressed in involvement of the macula or optic nerve. Neither important local complications nor intraocular drug toxicity were observed. Vitreous foscarnet levels in two different patients were 896 mumol/l and 74.9 mumol/l at 22 3/4 hours and 42 1/2 hours after the injection. Intravitreal foscarnet appears to be a safe, effective, and useful alternative in patients with intolerance to intravenous and viral therapy.

Intravitreal Foscarnet for Cytomegalovirus Retinitis in a Patient With Acquired Immunodeficiency Syndrome

We treated a patient who had acquired immunodeficiency syndrome and cytomegalovirus retinitis of the left eye. After anesthetic had been topically administered, the patient received intravitreal injections of 1,200 micrograms of foscarnet. Plasma and vitreous foscarnet levels were measured by high-performance liquid chromatography. Systemic absorption of the drug was not evident. Elimination half-life from the vitreous after one injection was 54.0 hours. Vitreous levels remained above the mean 50% inhibition value for cytomegalovirus for approximately 56 hours and above the mean inhibition value for human immunodeficiency virus for approximately 241 hours. The patients visual acuity improved from 20/30 to 20/25 in the left eye. Ophthalmoscopy showed the retinal lesion to have become inactive, and no reactivation occurred during the follow-up period of more than four months. The drug was well tolerated and no retinal toxicity was evident. We suggest an induction treatment regimen of two injections weekly for three weeks, followed by a maintenance treatment regimen of one injection weekly.

Early lipoic acid intake protects retina of diabetic mice.

The aim of this study was to test the effect of lipoic acid treatment on the retina after a short diabetic insult. Diabetes was induced by alloxan and mice were divided into sub-groups; control, diabetic, diabetic+insulin and all groups received±lipoic acid (100 mg/kg body weight) for 3 weeks. GSH content, MDA concentration, GPx activity were measured and electroretinograms (ERG) were recorded. Early administration of lipoic acid to diabetic mice prevented the statistically significant decreases of GSH content and GPx activity and normalized MDA concentration. Moreover, lipoic acid restored electroretinogram b-wave amplitude of diabetic animals to control values. Lipoic acid has a protective effect on the diabetic retina.

Diclofenac sodium and cyclosporin A inhibit human lens epithelial cell proliferation in culture

Abstract• Purpose: To investigate the effect of diclofenac sodium salt and cyclosporin A (CsA) on human lens epithelial cell (HLEC) growth in culture. • Methods: Cultures of HLEC were obtained from anterior capsules from extracapsular cataract surgery. Third-passage cells were seeded in 96-well plates in 0.1 ml culture medium. Cytotoxicity was estimated by the tetrazolium test in confluent monolayers after 24 h exposure to a wide range of concentrations of diclofenac and CsA. The effect of subcytotoxic concentrations of diclofenac and CsA on HLEC proliferation in subconfluent cultures was evaluated after 24 and 72 h of exposure. To investigate the relationship between PGEZ synthesis and the inhibitory effect of these drugs, after 24 h of exposure to diclofenac and CsA the production of PGE2 was measured by radioimmunoassay. We also tested the effect of exogenous PGE2 addition to diclofenac 72-h-treated cultures. • Results: Diclofenac and CsA (at concentrations ≥65 μM and ≥2.5 μM, respectively) inhibited the proliferation of subconfluent cultures of HLEC in a dose-dependent fashion. Diclofenac inhibits PGE2 synthesis, while CsA at high doses stimulates PGE2 synthesis of cultured HLEC. Exogenous PGE2 addition reversed in part the inhibitory effect of diclofenac.• Conclusions: Diclofenac and CsA at appropriate doses are effective in inhibiting cultured HLEC proliferation. This could be of interest to prevent posterior capsule opacification. Further in vivo experimental studies seem worthwhile.

Genetic analysis of 2299delG and C759F mutations (USH2A) in patients with visual and/or auditory impairments

The most common mutation in the USH2A gene (Usherin), 2299delG, causes both typical Usher (USH) syndrome type II and atypical USH syndrome, two autosomal recessive disorders, characterised by moderate to severe sensorineural hearing loss and retinitis pigmentosa (RP). Furthermore, the C759F mutation in the USH2A gene has been described in 4.5% of patients with nonsyndromic recessive RP. We have investigated the presence of the 2299delG and/or the C759F mutations in 191 unrelated Spanish patients with different syndromic and nonsyndromic retinal diseases, or with nonsyndromic hearing impairment. The 2299delG mutation was observed in patients with clinical signs of USHII or of atypical USH syndrome, whereas the C759F mutation, regardless of being associated with the 2299delG mutation or not, was identified in cases with nonsyndromic RP, as well as in patients with RP associated with a variability of hearing impairment. The comparative analysis of both phenotypic and genotypic data supports the hypothesis that sensorineural hearing loss in patients with RP may depend on the nature and on the association of the USH2A allele variants present.

Spectral Transmission of the Human Crystalline Lens in Adult and Elderly Persons: Color and Total Transmission of Visible Light

PURPOSE To experimentally measure the spectral transmission of human crystalline lenses belonging to adult and elderly persons, and to determine the color and total transmission of visible light of such crystalline lenses. METHODS The spectral transmission curve of 32 human crystalline lenses was measured using a PerkinElmer 800UV/VIS spectrometer. Total transmission of visible light and the chromatic coordinates of these crystalline lenses were determined from these curves for solar illumination. RESULTS The crystalline lens that filters UV and its transmission in the visible spectrum decreases with age; such a decrease is greater for short wavelengths. The total transmission of visible light decreases, especially after the age of 70 years, and the crystalline color becomes yellower and saturated. CONCLUSIONS The great variability existing in the spectral transmission of the human crystalline lens is lesser between the ages of 40 and 59 years, but greater from the age of 60 and older. The decrement in transmittance between these two age groups varies from 40% for 420 nm to 18% for 580 nm. Nevertheless, it is proven that age is not the only parameter affecting crystalline transmission. In the range of 40 to 59 years, age does not bear an influence on total transmission of light, but from 60 years and older it does. Moreover, the light transmitted decreases with age. This total transmission of light is similar to or lower than the amount that the different intraocular lenses transmit, even with a yellow or orange filter. The color of the human lens becomes yellowish and saturated with age.

Liposomally-entrapped ganciclovir for the treatment of cytomegalovirus retinitis in AIDS patients

Treatment of retinitis by cytomegalovirus (CMV) in AIDS patients requires frequent repetitive injections of intravitreal ganciclovir (GCV). This study was undertaken to establish experimentally whether the intravitreal application of liposomally-entrapped GCV could prolong intraocular therapeutic levels when compared with the intravitreal injection of free GCV, and the clinical effectiveness of this approach in AIDS patients. Intraocular concentration of GCV was determined by means of an ELISA test in rabbit vitreous 2, 3, 7, and 14 days after a single intravitreal injection of either different doses of the free drug (0.2–20 mg) or 1 mg of liposomally-entrapped GCV. After 72 h, only the vitreous of rabbits injected with doses of free GCV greater than or equal to 5 mg showed therapeutic levels of the drug; no GCV was detected after 72 h with any of the doses applied. Moreover, the microscopic study revealed GCV-induced damage in retinal structures in the animals injected with a free GCV dose greater than or equal to 15 mg. Intravitreal injection to rabbits of 1 mg of liposomally-encapsulated GCV showed no retinal toxicity at any of the time points studied, and therapeutic levels were detected up to 14 days after injection (4.67 ± 0.39 μg/ml). Five AIDS patients suffering CMV retinitis were injected with 0.5 mg of liposomally-entrapped GCV (2 mg of lecithin). Complete remission of the CMV retinitis was observed already at the third injection of 0.5 mg GCV (one per week) and relapse did not occur during the 2–4 month follow-up of the patients. In view of the results presented, it can be concluded that intravitreal injection of liposomally-encapsulated GCV increases the time period required for reinjections in the treatemnt of CMV retinitis.

Direct Objective Quantification of Corneal Haze after Excimer Laser Photorefractive Keratectomy for High Myopia

PURPOSE The purpose of the study is to measure regional distribution differences in corneal haze after excimer laser photorefractive keratectomy for high myopia. METHODS The authors developed computerized gradient edge detectors with which were analyzed digitized anterior slit-lamp photographs of 40 eyes, an average of 21.0 plus or minus 14.5 weeks after photorefractive keratectomy for high myopia (-6 to -22 diopters). A treated area an adjacent untreated area on the anterior corneal surface, each containing six regions, were quantified, and the difference was correlated with various parameters. RESULTS Mean differences between scarred and clear areas for haze grade 0.5, 1.0, 2.0, 3.0, and 4.0 were 16.9, 26.6, 42.6, 60.4, and 76.4 gray levels, respectively (rs = 0.96; P = 0.0001). A low but statistically significant correlation between the intended correction and postoperative corneal haze was found (r = 0.33; P = 0.037). The mean coefficient of variation of the amount of opacification within each treated area was 9.4%. This coefficient of variation increased with a longer follow-up time (r = 0.88; P = 0.0001). The difference in the intensity of haze between the center and more peripheral regions over the entrance pupil did not correlate with the attempted correction. However, a strong association between a relatively less severe central corneal haze with respect to more peripheral haze and longer follow-up time was found (r = -0.96; P = 0.0001). CONCLUSION The amount of corneal haze showed a weak positive association with the attempted correction in excimer laser photorefractive keratectomy for high myopia. Corneal haze appeared fairly uniformly distributed within the ablation zone, but a more heterogeneous distribution was found with a longer follow-up time. Furthermore, later postoperative examinations disclosed a clear trend toward diminishing central opacification relative to peripheral regions over the entrance pupil.

Reproducibility of Digital Image Analysis for Measuring Corneal Haze After Myopic Photorefractive Keratectomy

PURPOSE To evaluate the usefulness of digital image analysis for quantifying corneal haze by determining the reproducibility of its measurements at the corneal plane. METHODS In a prospective study, 20 randomly selected eyes that had undergone myopic photorefractive keratectomy were photographed focusing the slit beam on their anterior corneal surface. Each photograph was examined using computer image analysis techniques that detect the edge of the reticular pattern of the image. Quantification of the difference between two areas, treated and adjacent untreated cornea, each containing 3,750 pixels with a resolution of 256 gray levels, was performed. Intra-analyzer variation was determined by evaluating the photographs obtained by two analyzers under standard conditions on four separate visits. Interanalyzer variation was calculated using one measurement and the mean of the four measurements. RESULTS The pooled standard deviation of the measurements for the analyzers was 0.63 and 0.62 gray levels (coefficient of variation, 4.1% and 3.3%). An association between less severe haze measurements and higher reproducibility scores was found (r = .42; P = .007). The mean interanalyzer variation was smaller for the average of four measurements, 0.55 +/- 0.37 gray levels, than for one measurement, 0.94 +/- 0.73 gray levels (P = .014). CONCLUSIONS Good reproducibility for haze measurements by digital image analysis of the differences between the treated and adjacent untreated corneal areas was obtained. When the average of four measurements was used instead of a single measurement, interanalyzer reproducibility increased significantly. This new technique may be used to quantify and analyze corneal haze after myopic photorefractive keratectomy.