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Biomedical subjects

J Merayo-Lloves

Publications and source records attributed to J Merayo-Lloves.

16 recordsLinked to original sources
PubMed2005

[Corneal biomechanics].

OBJECTIVE: To review the corneal biomechanic concepts and to analyse, clarify and understand their relevance in refractive surgery. MATERIALS AND METHODS: A literature review has been done using different databases. RESULTS: Corneal biomechanic concepts are not new and are applied implicitly in numerous surgical procedures. Their origin is related to tonometry studies, but they gained in popularity when they were linked to the treatment of keratoconus, a pathology in which the mechanical properties of the cornea are altered. Factors determining corneal stability were thus defined. Corneal biomechanics have also been used following refractive surgery to study post-operative keratectasia and to improve ablation patterns, which ignores the corneal response. The new ablation systems need to include the biomechanical factors, which motivate research conducted in physical-mathematical models and in corneal wound healing, improving our knowledge about the corneal biomechanical response. CONCLUSIONS: The corneal biomechanic concepts have gained in popularity with the advent of refractive surgery, although they did exist previously. Their relevance is linked to improvements in the ablation systems used in an attempt to obtain more accurate and reliable results.

Biomechanical Phenomena↗
PubMed2001

Epstein-Barr virus dacryoadenitis resulting in keratoconjunctivitis sicca in a child.

PURPOSE: To describe a case of severe dry eye syndrome in a child. METHODS: Observational case report. The authors describe a 10-year-old male with severe dry eyes who was profoundly disabled by pain and photophobia despite aggressive conventional therapy. Lacrimal gland histology was consistent with the primary Sjögren syndrome, and serologic and immunohistologic evidence supported the hypothesis of Epstein-Barr virus causality. RESULTS: Treatment with systemic acyclovir and cyclosporin A resulted in dramatic and rapid reversal of the profound sicca syndrome and enabled the patient to resume his normal activities. CONCLUSION: Epstein-Barr virus dacryoadenitis should be considered in the differential diagnosis of keratoconjunctivitis sicca in children. Epstein-Barr virus can cause keratoconjunctivitis sicca, which can be treated successfully with acyclovir therapy in addition to suppression of the inflammatory response.

Acyclovir↗
PubMed2001

Optical response to LASIK surgery for myopia from total and corneal aberration measurements.

PURPOSE: To evaluate the optical aberrations induced by LASIK refractive surgery for myopia on the anterior surface of the cornea and the entire optical system of the eye. METHODS: Total and corneal aberrations were measured in a group of 14 eyes (preoperative myopia ranging from -2.5 to -13 D) before and after LASIK surgery. Total aberrations were measured using a laser ray-tracing technique. Corneal aberrations were obtained from corneal elevation maps measured using a corneal system and custom software. Corneal and total wave aberrations were described as Zernike polynomial expansions. Root-mean-square (RMS) wavefront error was used as a global optical quality metric. RESULTS: Total and corneal aberrations (third-order and higher) showed a statistically significant increase after LASIK myopia surgery, by a factor of 1.92 (total) and 3.72 (corneal), on average. This increase was more pronounced in patients with the highest preoperative myopia. There is a good correlation (r = 0.97, P < 0.0001) between the aberrations induced in the entire optical system and those induced in the anterior corneal surface. However, the anterior corneal spherical aberration increased more than the total spherical aberration, suggesting also a change in the spherical aberration of the posterior corneal surface. Pupil centration and internal optical aberrations, which are not accounted for in corneal topography, play an important role in evaluating individual surgical outcomes. CONCLUSIONS: Because LASIK surgery induces changes in the anterior corneal surface, most changes in the total aberration pattern can be attributed to changes in the anterior corneal aberrations. However, because of individual interactions of the aberrations in the ocular components, a combination of corneal and total aberration measurements is critical to understanding individual outcomes, and by extension, to designing custom ablation algorithms. This comparison also reveals changes in the internal aberrations, consistent with the posterior corneal changes reported using scanning slit corneal topography.

Adult↗
PubMed2000

Secondary glaucoma in patients with juvenile rheumatoid arthritis-associated iridocyclitis.

PURPOSE: The prevalence and management of glaucoma were evaluated in patients with juvenile rheumatoid arthritis (JRA)-associated iridocyclitis. METHODS: The records of 69 patients with JRA-associated iridocyclitis were reviewed. RESULTS: Twenty-nine (42%) of these patients had secondary glaucoma or ocular hypertension. Glaucoma was controlled with topical treatment in only 7 of the 41 affected eyes (17%); systemic carbonic anhydrase inhibitor therapy resulted in control of another 8 eyes. Surgery controlled all but one of the remainder. CONCLUSION: Glaucoma is a common complication of JRA-associated iridocyclitis. It results from prolonged, inadequately treated intraocular inflammation and in some instances, from steroid use. Medical and surgical therapy for the glaucoma associated with JRA-uveitis is challenging and incompletely effective. We suspect that a more aggressive approach to the treatment of JRA-associated uveitis, earlier in the course of the disease may reduce this vision robbing contribution to the process.

Adolescent↗
PubMed1999

Secondary glaucoma in patients with uveitis.

PURPOSE: To evaluate the prevalence of secondary glaucoma (SG), clinical forms of uveitis more frequently associated with glaucoma, and describe the treatment and complications encountered in a cohort of patients with glaucoma and uveitis during a 10-year period. METHODS: The hospital records of patients with uveitis referred to the Immunology Service of the Massachusetts Eye and Ear Infirmary for a decade were reviewed for cases of SG. RESULTS: One hundred and twenty of the 1,254 patients (9.6%) with uveitis developed SG. SG was more frequent in anterior uveitis (67%) but was also associated with posterior uveitis (13%) and pars planitis (4%). Herpetic keratouveitis (22%), Fuchs' iridocyclitis (19%), juvenile rheumatoid arthritis-associated iridocyclitis (16%), syphilis (14%), and sarcoidosis (12%) were the leading types of uveitis associated with SG. Despite aggressive medical and surgical therapy, SG was associated with progressive visual field loss and optic nerve damage in 39 patients (33%). CONCLUSION: SG is an underappreciated, vision-threatening complication in patients with uveitis. Increased vigilance for emergence of this complicating problem during the care of patients with uveitis is warranted, and medical and surgical treatment for reducing IOP should be especially aggressive in these patients. We hypothesize that earlier, more aggressive treatment of uveitis will reduce the presence of glaucoma as an additional vision-robbing complication of uveitis.

Adolescent↗
PubMed1998

Comparative effectiveness and molecular pharmacological mechanisms of antiallergic agents on experimental conjunctivitis in mice.

The purpose of this study was to determine the effectiveness of antiallergic agents in the treatment of experimental murine ragweed conjunctivitis. SWR/J mice were divided into eight groups: 1; normal controls (unmanipulated); 2, untreated; 3, lodoxamide; 4, cromolyn; 5, livocarbastine; 6, nedocromil; 7, buffer solution (BS); and 8, tetrandine (TDR). Groups 2-8 were exposed to ragweed pollen through topical application to conjunctival and nasal mucosa, followed by conjunctival challenge with the allergen. Allergic conjunctivitis was evaluated by scoring of the clinical signs and histopathology. mRNA gene expression of interleukin 1beta (IL-1beta), IL-6 and tumor necrosis factor alpha (TNF-alpha) in conjunctiva was analyzed by reverse transcription polymerase chain reaction techniques. Exposed mice developed allergic conjunctivitis clinically and histologically that was modulated by topical lodoxamide, cromolyn, livocarbastine, or nedocromil eye drops or TDR intraperitoneally injected. Histopathologic analysis demonstrated that the drugs and TDR significantly reduced conjunctival eosinophil infiltration and the number of intact and degranulating mast cells. IL-1beta and TNF-alpha mRNA gene expression in conjunctiva of treated mice was inhibited compared with untreated and BS-treated controls. No IL-6 mRNA expression was observed even on the conjunctiva of the untreated mice. The antiallergic drugs and TDR exerted a similar action on the murine model of allergic conjunctivitis and demonstrated pharmacologic effectiveness on the conjunctival mRNA expression of cytokines IL-1beta and TNF-alpha.

Alkaloids↗
PubMed1997

Visual outcomes prognosticators in juvenile rheumatoid arthritis-associated uveitis.

PURPOSE: The purpose of the study is to delineate the visual prognosticators in juvenile rheumatoid arthritis-associated uveitis. METHODS: The records of 43 patients with juvenile rheumatoid arthritis-associated uveitis who were observed for at least 6 months were studied retrospectively. Bivariate and multivariate statistical models were applied to more than 40 parameters to determine the relative odds of visual rehabilitation among patients with each characteristic. RESULTS: Thirty-seven (86%) patients were females and 6 (14%) males. The mean known age of uveitis onset was 13 years, with females having, on average, 4 years earlier onset of disease compared to males (P = 0.04). Ninety-three percent had chronic, 5% had recurrent, and 2% had an acute monophasic disease course. Of the 76 affected eyes, 93% were nongranulomatous and 97% had iridocyclitis. The mean overall duration of uveitis was 146 months, with females suffering from a significantly longer duration of active disease than did males (P < 0.001). Nineteen (44%) patients underwent cataract extraction, and 16 (37%) underwent vitrectomy. Thirty (70%) of the patients experienced visual improvement with their therapy. When controlling for potential confounders, male sex (P = 0.006), shorter duration of uveitis (P = 0.007), older age at disease onset (P = 0.02), and a shorter delay in presentation to a subspecialist (P = 0.02) were associated significantly with visual acuity improvement. Visual acuity at presentation (P = 0.001), use of systemic nonsteroidal anti-inflammatory drugs (P = 0.01), older age at disease onset (P = 0.02), absence of glaucomatous neuropathy (P = 0.02), and male sex (P = 0.03) were correlated strongly with a final visual acuity outcome of 20/40 or better. CONCLUSION: Juvenile rheumatoid arthritis-associated uveitis is a serious disease with a guarded visual prognosis. It is hoped that increased awareness of its prognosticators will lead to treatment and referral patterns that have the best chance of minimizing the likelihood of visual impairment in patients with juvenile rheumatoid arthritis.

Acute Disease↗
PubMed1997

Potent inhibitory effect of tetrandrine on experimental allergic conjunctivitis in mice.

This study investigated the effectiveness of tetrandrine (TDR) on experimental allergic conjunctivitis secondary to ragweed pollen. SWR/J mice were divided as follows: group 1, normal controls; group 2, sensitized but untreated; group 3, sensitized, buffered saline (BS)-treated; and group 4, sensitized, TDR-treated. The last three groups were exposed to ragweed through topical contact on the nasal and conjunctival mucosae followed by challenge with the allergen on the conjunctiva. Groups 3 and 4 received doses of BS and TDR, respectively. The allergic conjunctivitis was evaluated by scoring of the clinical signs and histopathology. mRNA gene expression of interleukin 1 beta (IL-1 beta) and IL-5 in the conjunctiva was analyzed by polymerase chain reaction techniques. All mice exposed to ragweed developed allergic conjunctivitis clinically and histologically. The conjunctivitis was significantly modulated by intraperitoneal injection of a new anti-inflammatory agent, TDR. Histopathologic analysis demonstrated that TDR strikingly reduced the conjunctival eosinophil infiltration and the number of intact and degranulating mast cells. IL-1 beta and Il-5 mRNA gene expression in the conjunctiva of TDR-treated mice was dramatically down-regulated compared with untreated and BS-treated controls. The results indicate that TDR may have potential clinical use in the treatment of conjunctivitis.

Alkaloids↗
PubMed1996

A new murine model of allergic conjunctivitis and effectiveness of nedocromil sodium.

BACKGROUND: Allergic conjunctivitis is the most common atopic disease affecting the eye. To study the pathophysiology and effectiveness of antiallergic drugs, it is necessary to develop animal models that closely mimic human allergic conjunctivitis. OBJECTIVE: The study was performed to develop an experimental murine model of ocular allergic conjunctivitis to an airborne allergen. METHODS: SWR/J mice were divided into the following groups: group 1, untreated, experimental; group 2, phosphate-buffered saline-treated; group 3, nedocromil sodium-treated; and group 4, unmanipulated controls. Groups 1, 2, and 3 were exposed to ragweed by topical contact with the nasal and conjunctival mucosae. Allergic conjunctivitis was evaluated by scoring of clinical signs, serum IgE levels, and histologic findings. RESULTS: Mice exposed to ragweed had clinicopathologic signs of allergic conjunctivitis and specific anti-ragweed IgE. Allergic conjunctivitis was modulated by nedocromil sodium. Treated mice had fewer clinical signs of allergy, lower levels of ragweed-specific IgE, reduction of conjunctival eosinophil infiltration, decrease in the number of intact and degranulating mast cells, and reduction of cytokine release. CONCLUSION: This is the first report of a murine model of allergic conjunctivitis to an airborne allergen that can be used to study the disease pathophysiology and its response to treatment.

Animals↗
PubMed1996

Prognosticators for visual outcome in sarcoid uveitis.

PURPOSE: The purpose of the study is to delineate the visual prognosticators in sarcoid-associated uveitis given the current standards of care. METHODS: The records of 60 patients with sarcoid-associated uveitis who were observed for at least 6 months were studied retrospectively. Multivariate regression models using the generalized estimating equations approach to adjust for the correlation between fellow eyes were applied to determine disease, patient, and treatment characteristics that altered the odds of visual rehabilitation. RESULTS: One hundred twelve eyes of 43 women and 17 men who met the inclusion criteria were identified. Seventy-seven percent of patients were white, 15% black, and 8% of Hispanic origin. Uveitis developed in the patients at a mean age of 42 (range, 4-82) years. Of the 112 affected eyes, 81% had granulomatous and 15% nongranulomatous uveitis. Most patients (66%) had anterior or intermediate uveitis alone. Ninety-one percent had chronically smoldering disease; another 7% had recurrent flares, and only 1 patient had a monophasic acute course to her uveitis. Vision-threatening complications developed in many patients, including 58% in whom cystoid macular edema developed and 25% in whom media opacities developed, requiring cataract surgery or vitrectomy or both. Overall, 34% of treated eyes and 51% of patients had final visual acuities that were superior to their acuities at presentation. The factors most significantly associated with a final visual acuity of worse than 20/40 after controlling for potential confounders were as follows: delay in presentation to a subspecialist (odds ratio [OR] = 2.94, P = 0.05), total duration of uveitis (OR = 1.04, P = 0.09), development of cystoid macular edema (OR = 0.37, P = 0.07) or glaucoma (OR = 4.54, P = 0.02), presence of intermediate (OR = 5.00, P = 0.01) or posterior uveitis (OR = 8.33, P = 0.04), and systemic steroid use (OR = 0.30, P = 0.03) were the parameters most strongly correlated with a lack of visual acuity improvement. Delay in presentation to a subspecialist (OR = 20.00, P = 0.01), development of glaucoma (OR = 50.00, P = 0.005), presence of intermediate (OR = 25.00, P = 0.02) or posterior uveitis (OR = 50.00, P = 0.02), black race (OR = 11.11, P = 0.02), (log) visual acuity at presentation (OR = 0.05, P = 0.0001), and use of systemic steroids (OR = 0.07, P = 0.02). CONCLUSION: Multivariate outcomes analysis, particularly after correcting for the correlation between fellow eyes, is a useful analytic tool for optimization of standards of care and for disease risk stratification to aid both physicians and patients.

Adolescent↗
PubMed1995

Analysis of the acute ophthalmic manifestations of the erythema multiforme/Stevens-Johnson syndrome/toxic epidermal necrolysis disease spectrum.

PURPOSE: To evaluate the epidemiology, possible etiologic factors, complications encountered, and treatment administered to a group of patients with ocular involvement in the erythema multiforme/Stevens-Johnson syndrome/toxic epidermal necrolysis disease spectrum who were seen at two large tertiary referral centers over a 34-year period. METHODS: Hospital records from 1960 to 1994 at the Massachusetts General Hospital and Shriners Hospital for Crippled Children were reviewed for patients with erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis. Only patients fulfilling specific clinical diagnostic criteria and those who received a diagnosis by a dermatologist were included in the review. RESULTS: A total of 366 patients with erythema multiforme, Stevens-Johnson syndrome, or toxic epidermal necrolysis were identified. Drugs were the most commonly identified etiologic factor in all three conditions: sulfonamides were the most frequently identified agents. Eighty-nine patients (24%) had ocular manifestations at the time of their acute hospital stay. Ocular involvement was seen in 9% of patients with erythema multiforme, in 69% with Stevens-Johnson syndrome, and in 50% with toxic epidermal necrolysis. The ocular problems were more severe in patients with both Stevens-Johnson syndrome and toxic epidermal necrolysis. There was no significant difference between the number of patients who were treated with systemic steroids and those who were not (P = 0.42). CONCLUSIONS: The erythema multiforme/Stevens-Johnson syndrome/toxic epidermal necrolysis disease spectrum remains an important cause of severe visual loss in a significant number of patients. Systemic steroids used during the acute phase of the disease appear to have no effect on the development of ocular manifestations. Studies on the acute immunopathogenic mechanisms occurring in these disease are warranted if more effective therapies are to be found.

Acute Disease↗
PubMed1995

T cell receptor V beta gene expression in experimental herpes stromal keratitis.

Our study examined T cell receptor (TCR) V beta mRNA expression in a murine model of experimental herpes simplex keratitis (HSK). We employed a polymerase chain reaction (PCR) technique to detect TCR V beta mRNA expression in the inoculated eyes of both HSK-susceptible and HSK-resistant mice at different time points after corneal inoculation with herpes simplex virus type 1 (HSV-1), followed by Southern blotting and densitometry analysis. In eyes from HSK-susceptible C.AL-20 mice, a more diverse TCR V beta transcript usage pattern was detected as compared with that seen in HSK-resistant C.B-17 mice. V beta 8 family members were expressed in both strains of mice at days 11, 14 and 21 post-inoculation. By densitometry, at day 11, the intensity of expression of V beta 8.2 and V beta 8.3 message was significantly greater in the eyes of C.AL-20 mice; V beta 8.1 was expressed only in C.B-17 mice. There were obvious differences in the TCR V beta expression between HSK-susceptible and HSK-resistant mice. The differences in the intensity of the message expressed by V beta 8 family members between the two strains could be correlated to previous experiments that showed V beta 8.1,2+ T cells as the main infiltrating cells in the corneas of HSK-susceptible mice by day 11 and 14 after challenge with HSV-1.

Animals↗
PubMed1995

Expression of collagens I, III, IV and V mRNA in excimer wounded rat cornea: analysis by semi-quantitative PCR.

A semi-quantitative polymerase chain reaction (PCR) methodology was used to evaluate the kinetic changes occurring in collagens I, III, IV and V mRNA in rat cornea following excimer laser keratectomy. cDNA was synthesized from RNA extracted from rat cornea at various times following excimer laser photoablative keratectomy. Collagen cDNA sequences were subsequently amplified using specific sets of oligonucleotide primers. Competitive PCR amplification was carried out using an internal standard so that a semi-quantitative analysis of message for synthesis of collagen types I, III, IV and V could be performed and time course dynamics of message for these collagens studied. There was a biphasic increase in the levels of collagens III, IV and V mRNA following excimer laser keratectomy. Collagen I mRNA levels demonstrated a more sustained increase and were still elevated at 6 weeks following wounding. Collagens IV and V mRNA showed the largest increase with an approximate three fold increase over controls between 4 days and 1 week. Our results demonstrate that upregulation of stromal collagens I, III, and V mRNA and basement membrane collagen IV mRNA occurs in rat cornea following excimer laser keratectomy.

Animals↗
PubMed1995

Experimental model of allergic conjunctivitis to ragweed in guinea pig.

An experimental model of ocular allergy was developed in the guinea pig by exposing these animals to ragweed through topical contact on nasal and conjunctival mucosae, followed by subsequent challenge with ragweed contact on the conjunctiva. Animals developed clinical and histological signs of allergy with and without the use of interleukin 4 as adjuvant. This model mimics human hay fever conjunctivitis more naturally than do animal models previously reported, and it may be subsequently more valuable in the study of the response of allergic conjunctivitis to different therapeutic approaches.

Adjuvants, Immunologic↗
PubMedDate not supplied

Experimental model of corneal haze in chickens.

PURPOSE: To develop an experimental animal model of corneal haze following photorefractive keratectomy (PRK). METHODS: Fifteen Iber Braun hens underwent unilateral PRK for -9.00 D of myopia. The animals were sacrificed at 1, 3, and 6 months postoperatively, and light microscopy was performed. RESULTS: Slit-lamp microscopy showed haze in the PRK-treated eyes. Histopathologic study disclosed epithelial hyperplasia, basement membrane abnormalities, and extensive anterior stromal disorganization. CONCLUSIONS: An easy and inexpensive model of haze after PRK was developed in an animal with Bowman's layer. This new model could be useful to understand the pathophysiology and pharmacologic modulation of corneal haze.

Animals↗