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Biomedical subjects

A J Bron

Publications and source records attributed to A J Bron.

At least 37 records · Page 2Linked to original sources
PubMed2000

Tear meniscus changes during cotton thread and Schirmer testing.

PURPOSE: To elucidate the effect of the cotton thread test (CT-T) and Schirmer test (S-T) on the tear reservoir by evaluating the radius of tear meniscus curvature. METHODS: The radii (R) of the central lower tear menisci were measured by a newly developed video meniscometer in 11 eyes of 11 normal volunteers (6 men, 5 women; mean age, 27.7 +/- 3.6 years [SD]) and 9 eyes of 9 patients with tear deficiency and severe dry eye in whom the puncta had been therapeutically occluded (9 women; mean age, 50.6 +/- 10.4 years). In this dry eye group, the absence of reflex tearing, coupled with the absence of lacrimal drainage due to punctal occlusion allowed more precise observation of the removal of tears from the meniscus. A 1-minute CT-T was performed, followed after an interval of 10 minutes by a 1-minute S-T. Tear meniscus curvature was documented before (R:(0)) and during the tests at 30 seconds (R(30)) and 60 seconds (R:(60)). RESULTS: In the normal group, respective R values (CT-T; S-T; mean +/- SD mm) were R(0) (0.26 +/- 0.11; 0.26 +/- 0. 07), R(30) (0.27 +/- 0.16; 0.20 +/- 0.13), and R(60) (0.29 +/- 0.15; 0.23 +/- 0.21); and in the dry eye group, respective R: values (CT-T; S-T) were R(0) (0.59 +/- 0.23; 0.51 +/- 0.19), R(30) (0.52 +/- 0.25; 0.22 +/- 0.09), and R(60) (0.51 +/- 0.19; 0.21 +/- 0.08). It was demonstrated in the dry eye group that R was diminished more by the S-T than by the CT-T in the time course of the measurement (P = 0.01). In the dry eye group alteration of R occurred within the first 30 seconds, and in this group significant correlation was found between R(0) and the S-T result (r = 0.67; P = 0.05), and between R(60)- R(0) and the S-T result (r = -0.81; P = 0.01). Also, there was a significant correlation between R(60)- R(0) and the S-T result in the normal group (r = 0.71; P = 0.02). There were no significant correlations between R(0) or R(60)- R(0) and the CT-T results in either group. CONCLUSIONS: These studies afford some insight into the dynamics of the Schirmer test, suggesting that wetting is influenced by the negative hydrostatic pressure within the tear meniscus. With the protocol used, no conclusion could be drawn about the relation between meniscus radius and wetting of the cotton thread.

Adult↗
PubMed1999

Deposits and proteoglycan changes in primary and recurrent granular dystrophy of the cornea.

OBJECTIVE: To investigate the origin and distribution of granular deposits in the corneas of 3 patients with granular dystrophy, 1 of whom had previously received a lamellar keratoplasty in which the granular dystrophy had recurred. METHOD: Corneal tissue from 2 patients with primary granular dystrophy (patients 1 and 2) and from a patient with recurrent granular dystrophy (patient 3) was examined. Corneal graft tissue was fixed in (1) 3% glutaraldehyde in sodium cacodylate buffer, (2) 2.5.% glutaraldehyde in sodium acetate buffer containing cuprolinic blue, and (3) 4% paraformaldehyde in phosphate-buffered saline. RESULTS: In patient 1 (aged 48 years), electron-dense granular structures were observed in epithelium, Bowman layer, and throughout the stroma. Bowman layer was absent in several places. Patient 2 (aged 78 years) showed similar features except with more deposits in the stroma. In patient 3 (aged 48 years), granular structures were heavily deposited in the epithelium; there were also some deposits in the posterior (host) stroma, some of which were associated with partially degenerated keratocytes. Bowman layer appeared normal. In all 3 patients, the intracellular or extracellular granular structures were surrounded by fine fibrillar material and abnormal proteoglycans. Electron-lucent spaces within the corneal stroma contained large quantities of abnormal proteoglycan filaments that were attached in part to collagen fibrils. CONCLUSIONS: Results from patient 3 support an epithelial origin for the deposits, presumably from keratoepithelin, aggregated with other proteins. The role of keratocytes is less clear, although the presence of deposits in the stroma of all 3 patients, some associated with keratocytes, suggests that these cells might produce granular material in addition to abnormal proteoglycans.

Aged↗
PubMed1999

Assessment of meibomian gland function in dry eye using meibometry.

OBJECTIVE: To study meibomian gland function in dry eyes using meibometry. METHODS: Forty-two patients with clinically diagnosed dry eye that was reclassified as meibomian gland dysfunction (MGD [n = 12]), aqueous-tear deficiency (AD [n = 10]), MGD combined with AD (n = 2), "incomplete" dry eye (n = 12), and non-dry eye (6 eyes) were compared with 41 healthy control subjects. The following 2 techniques of meibometry were applied: direct meibometry (DM) measuring lipid imprints using the Meibometer, and integrated meibometry (IM) using image-scanning and computer densitometry. Tear film lipid layer thickness was assessed using interference microscopy. RESULTS: Imprints were homogeneous for all subjects except those with MGD. Mean+/-SE readings on results of DM were 127.24+/-24.4 for MGD, 306.4+/-9.2 for AD, 248.6+/-13.2 for incomplete dry eye, and 268.5+/-6.3 for controls, showing lower values in the MGD group relative to all others (P<.001). Results of IM gave similar results (P<.001, P =.01, and P<.001, respectively). Lipid layers appeared lower for the MGD group than others. CONCLUSIONS: Compared with controls, lid lipid levels are reduced in patients with MGD, and increased in women with AD. Lipid layer thickness is increased in women with AD compared with patients with MGD. Both meibometric techniques may be useful for evaluating MGD. Although DM requires special equipment (the Meibometer), it provides a record of immediate diagnostic value. Although IM is less effective than DM, it offers visual documentation of the lipid imprint, which may itself be of diagnostic value, and uses equipment available in many laboratories.

Aged↗
PubMed1999

Physical properties of stimulated and unstimulated tears.

It has long been assumed that unstimulated tears are more thoroughly equilibrated with epithelial secretions than stimulated tears, since they are in contact with tarsal, bulbar and corneal surfaces for longer. It was also believed from results with model solutions that soluble mucin is responsible for the observed surface tension and viscosity of tears. If longer contact means more mucin is dissolved in the aqueous tears, then the surface activity (surface tension lowered by mucin) and viscosity (raised by mucin) of tears should therefore be enhanced in unstimulated over stimulated tears. Pools of stimulated and minimally-stimulated tears were collected from a group of healthy adult volunteers by glass capillary. Viscosities were measured in the Contraves Low Shear 30 rheometer over the range of shear rates 0-130 sec-1. Surface tension was measured in the collection capillaries by a micro-technique, before and after refrigerated storage. Both surface tension and viscosity were determined for a variety of tear proteins and mucins. No significant difference was found between the viscosity/shear rate plots of stimulated and unstimulated tear samples. The viscosities of solutions of individual tear proteins were low, except for the combination of lysozyme and secretory IgA. Surface tensions were also similar in both cases, and unchanged by storage at room temperature or refrigeration, indicating no significant loss of surface-active material by adsorption on the capillary walls. Results with model mucin solutions gave a variety of results indicating either little surface activity or losses due to wall adsorption. Tear proteins, individually or in combination, did not lower surface tension to the level of tears. Tear viscosity seems not to depend on the level of dissolved mucins. This suggests either that a constant level of these is picked up even by short-term contact with ocular surfaces, or that viscosity arises from currently unknown materials which vary little with tear flow rate. This type of shear-dependent viscosity is most easily simulated in model solutions with polyionic linear macromolecules, including mucins. The contribution of individual proteins to overall viscosity is small, but combinations including lysozyme show tear-like characteristics, and may indicate that proteins whose concentration is relatively independent of tear flow rate combine with other tear components (possibly including mucins or lipids) to produce their full effect on tear viscosity. The surface tension results suggest that mucins are not of primary importance. Theories of tear film structure and performance need revision.

Adult↗
PubMed1999

Postoperative intraocular lens rotation: a randomized comparison of plate and loop haptic implants.

OBJECTIVE: To compare the postoperative rotation of plate and loop haptic implants of spherical power to ascertain the optimal design appropriate for toric intraocular lenses (IOLs). DESIGN: Randomized, controlled trial. PARTICIPANTS: Forty-eight patients attending for routine cataract surgery by phacoemulsification. METHOD: Patients with cataract as the only ocular disease were randomly implanted with plate or loop haptic implants after uncomplicated phacoemulsification. The baseline position of the IOL was determined from a video frame acquired at the conclusion of surgery. Postoperative IOL position was documented using digital retroillumination images at 2 weeks and 6 months after surgery. Capsular fusion patterns were recorded using slit-lamp biomicroscopy. Correlation of IOL rotation with axial length, capsular contraction, and fusion was attempted. MAIN OUTCOME MEASURES: Early IOL rotation, occurring between surgery and 2 weeks after surgery, was graded as mild (<10 degrees), moderate (10 degrees < to <30 degrees), or severe (>30 degrees) by a semiobjective online comparison of the images. Late IOL rotation, occurring between 2 weeks and 6 months, was measured more precisely using software developed specifically for the study. RESULTS: Twenty-three patients were allocated the loop haptic and 25 the plate haptic IOL. The groups were comparable for demographic variables and numbers of patients excluded from analysis (P > 0.05). Five (24%) of 21 of plate haptic IOLs underwent severe early rotation compared to 2 (9%) of 22 loop haptics (P = 0.36). The median late rotation was 6.8 degrees for loop haptics compared to 0.6 degrees for plate haptics (P = 0.0073). Between 2 weeks and 6 months, anticlockwise rotation had occurred in 16 (89%) of 18 loop haptic IOLs compared to 11 (52%) of 21 plate haptic IOLs (P = 0.0081). CONCLUSIONS: Plate haptic IOLs show greater rotational stability than do loop haptics made from polypropylene once capsular fusion has taken place. Loop haptics invariably rotate anticlockwise after 2 weeks.

Capsulorhexis↗
PubMed1999

The development and maintenance of emmetropia.

The human eye is programmed to achieve emmetropia in youth and to maintain emmetropia with advancing years. This is despite the changes in all eye dimensions during the period of growth and the continuing growth of the lens throughout life. The process of emmetropisation in the child's eye is indicated by a shift from the Gaussian distribution of refractive errors around a hypermetropic mean value at birth to the non-Gaussian leptokurtosis around an emmetropic mean value in the adult. Emmetropisation is the result of both passive and active processes. The passive process is that of proportional enlargement of the eye in the child. The proportional enlargement of the eye reduces the power of the dioptric system in proportion to the increasing axial length. The power of the cornea is reduced by lengthening of the radius of curvature. The power of the lens is reduced by lengthening radii of curvature and the effectivity of the lens is reduced by deepening of the anterior chamber. Ametropia results when these changes are not proportional. The active mechanism involves the feedback of image focus information from the retina and consequent adjustment of the axial length. Defective image formation interferes with this feedback and ametropia then results. Heredity determines the tendency to certain globe proportions and environment plays a part in influencing the action of active emmetropisation. The maintenance of emmetropia in the adult in spite of continuing lens growth with increasing lens thickness and increasing lens curvature, which is known as the lens paradox, is due to the refractive index changes balancing the effect of the increased curvature. These changes may be due to the differences between nucleus and cortex or to gradient changes within the cortex.

Aging↗
PubMed1999

Sugars including erythronic and threonic acids in human aqueous humour.

PURPOSE: Sugars in the aqueous humour of the eye serve both as a source of nutrients to the lens and other anterior ocular tissues, and potentially as an indicator of waste products from these tissues. In this work we intended to measure the levels of sugars in human blood and aqueous humour from cataract patients with and without diabetes. After initial results we decided to identify an unknown sugar component. METHODS: Sugars were measured by hplc. The unknown sugar peak was identified by gas chromatography/mass spectrometry RESULTS: Very little fructose and sorbitol were found. Glucose levels were higher in both blood and aqueous from diabetic patients. During these analyses we found a major component that did not correspond to any sugar reported previously in aqueous humour. This was identified as a mixture of threonic and erythronic acids. CONCLUSIONS: Glucose levels increase in human aqueous humour in diabetes without markedly raised levels of sorbitol or fructose. Erythronic and threonic acids are normal components of aqueous humour and blood. They may be derived from glycated proteins or from degradation of ascorbic acid.

Aged↗
PubMed1998

The meibomian glands and tear film lipids. Structure, function, and control.

Meibomian gland disease--and, in particular, obstructive meibomian gland disease--makes an important contribution to ocular surface disease, in the form of meibomian keratoconjunctivitis. With improved methods for the study of meibomian oil composition and function, we are moving closer to the possibility of distinguishing the contribution of meibomian deficiency, as opposed to inflammatory events, to this disorder. More importantly, where aqueous tear deficiency and meibomian gland disease coincide in patients with dry eye, we are closer to the possibility of distinguishing their relative contributions to the dry eye state. This has implications for future therapies.

Androgens↗
PubMed1998

Nutrition supplements and the eye.

PURPOSE: A review of the role of vitamins, minerals, carotenoids and essential fatty acids in relation to eye health. The mode of action may be directly on the eye or by promoting bodily health on which the eye depends. RESULTS: The lens and retina suffer oxidative damage and the anti-oxidant vitamins A, C and E are implicated as protective. Studies in man give indifferent support to the role of nutrition in the development of cataract. In the elderly, vitamin intake may be inadequate, so that a vitamin supplement may be reasonable. Zinc has a role in retinal metabolism and may be beneficial in macular degeneration. Selenium has an anti-oxidant role. Other minerals including copper have a less defined role. Carotenoids are concentrated at the macula and have an anti-oxidant role. A reduced risk of macular degeneration is found in relation to a high serum level. The essential fatty acid, gamma-linolenic acid (GLA), is useful in Sjögren's syndrome and may help in other dry eye conditions. Omega-3 fatty acids are important in retinal development and have a role in preventing cardiovascular disease. CONCLUSION: All persons should be encouraged to maintain healthy nutrition. Middle-aged and elderly patients may benefit from a supplement. An intake in excess of the recommended daily intake may be beneficial, but this is not proven. Further clinical trials are indicated to define the advisability of vitamin, mineral and other supplements. Dosages for recommended intake and for supplements are given.

Carotenoids↗
PubMed1998

Comparison of the efficacy and safety of two eye gels in the treatment of dry eyes: Lacrinorm and Viscotears.

PURPOSE: To compare the efficacy and safety of two carbomer 940 eye gels in the treatment of dry eyes: Lacrinorm (also called GelTears), a recently introduced eye gel, and Viscotears (also called Vidisic or Lacrigel), used as a reference gel. The main difference between the two gels is in the preservative, respectively benzalkonium chloride and cetrimide. METHODS: A double-masked, randomised, parallel-group study was conducted in 16 centres in four European countries. A total of 179 patients suffering from aqueous-deficient dry eye were enrolled, of whom 92 were randomised to treatment with Lacrinorm and 87 to the reference gel. Gel was instilled four times a day for a period of 30 days. RESULTS: After 30 days of treatment, subjective symptoms (the combined scores of foreign body sensation, ocular dryness, burning or pain, and photophobia) had improved by 50% in the Lacrinorm group and by 45% in the reference gel group, and objective test results (break-up time, fluorescein test, Schirmer test, Lissamine Green test) by 35-36% in the Lacrinorm group and 25-45% in the reference group. The improvements were significant in both treatment groups (p < 0.001), with no significant differences between the treatment groups. Subjective local tolerability upon instillation on day 30 was rated 'good' or 'very good' by 91% of patients in both treatment groups. Adverse events were reported for 21 patients in the Lacrinorm group and 17 in the reference group, the most frequent being discomfort, blurred vision, hyperaemia, burning and itching. The frequency and descriptions of adverse events did not differ significantly between the two treatment groups. No serious adverse events were reported. CONCLUSIONS: Over the period of study, Lacrinorm eye gel was as effective and safe as Viscotears/Lacrigel in the treatment of dry eye.

Acrylic Resins↗
PubMed1997

Cavernous-dural fistula with secondary angle-closure glaucoma.

PURPOSE: To report a rare case of angle-closure glaucoma, secondary to the rapid development of a choroidal effusion, in a patient with a long-standing cavernous-dural shunt. METHODS: Case report. Investigations included computed tomographic scan, magnetic resonance imaging, and carotid angiography. RESULTS: The development of the choroidal effusion occurred because of partial thrombosis of the ipsilateral superior ophthalmic vein and cavernous sinus. Drainage of the choroidal effusion resolved the angle-closure glaucoma. CONCLUSIONS: The combination of worsening signs and evidence of thrombosis indicates impending resolution of a cavernous-dural shunt. However, if a choroidal effusion causes angle-closure glaucoma, prompt surgical drainage should be considered to prevent permanent peripheral anterior synechiae formation, with the expectation that the effusion will not recur.

Aged↗
PubMed1997

Decentration of 5.1 mm intraocular lenses after continuous curvilinear capsulorhexis and in-the-bag fixation.

PURPOSE: To determine the incidence of decentration in eyes with 5.1 mm optic intraocular lenses (IOLs) and to assess the effect on vision. SETTING: Clinical Cataract Research Unit, Oxford Eye Hospital, Oxford, England. METHODS: Patients having phacoemulsification and small IOL implantation over 12 months were identified and invited for assessment. Intraocular lens decentration was measured geometrically using a modified, digital, retroillumination camera. The expected incidence of symptoms caused by decentration was estimated by determining the presence of an IOL edge within an artificial pupil overlaid on the digital image. RESULTS: In 13 eyes (20%), IOL decentration was more than 0.5 mm. Symptoms were expected in 38 patients (59%) but occurred in only 14 (22%). CONCLUSION: Decentration of the 5.1 mm optic IOL caused fewer clinical problems than anticipated, although the results raise concerns that such IOLs may be inappropriate in patients who need excellent vision in scotopic illumination.

Aged↗
PubMed1996

Ultrastructural study of the cornea in a bone marrow-transplanted Hurler syndrome patient.

This case report describes a 14-year-old girl with Hurler syndrome, who had received a successful bone marrow-transplant at the age of two. Corneal clouding was present at the time of transplant and has only partially cleared. A right penetrating keratoplasty was performed and the corneal specimen was examined by light microscopy, transmission electron microscopy with Cuprolinic blue staining for proteoglycans, and low-angle X-ray diffraction. The results show the corneal stroma to be disrupted by vacuolated stromal cells. There is abnormal accumulation of proteoglycans in the vacuolated stromal cells and nearby stroma. These proteoglycans mainly contain chondroitin/dermatan sulphate glycosaminoglycans since they are susceptible to chondroitinase ABC. There are a large range of fibril diameters (12.5-50.1 nm) and there is an abnormal distribution of the fibril diameters measured from micrographs. Both are confirmed by X-ray diffraction results (the mean collagen fibril diameters are in a range between 29.7 and > 51.1 nm). X-ray diffraction also shows that the mean centre-to-centre distance of the fibrils slightly increases. These findings suggest that proteoglycans play a role in modelling the stromal structure and can also explain the corneal clouding. Many long-spacing collagen structures with a mean periodicity of 91.8 nm are observed in the corneal stroma. The finding that the long-spacing collagen consists of fine collagen fibrils and that very few proteoglycans filaments bind to them suggests that some change in the interaction of proteoglycans and collagen is responsible for the formation of long-spacing collagen. To our knowledge, this is the first ultrastructural study of the cornea from a bone marrow-transplant patient with Hurler syndrome. The structural features documented here relate to a cornea incompletely corrected by bone marrow transplantation.

Adolescent↗