Calculating the error in refractive error.

AIMS AND PURPOSE: To demonstrate a quick way of calculating the optical difference between two refractions using vector analysis, and to express this as a score for examination purposes. METHODS: An existing formula is applied, converted to a defocus equivalent, and then converted to a score. The formula is set out in an Excel spreadsheet. RESULTS: The spreadsheet enabled rapid assessment of the difference between two refractive errors. Examples are demonstrated. CONCLUSION: The spreadsheet was successful in enabling a comparison of any two refractions, expressing the difference either as a correcting (third) refraction, a defocus equivalent or a one-figure score.

Human preocular mucins reflect changes in surface physiology.

BACKGROUND/AIMS: Mucin function is associated with both peptide core and glycosylation characteristics. The authors assessed whether structural alterations occurring during mucin residence in the tear film reflect changes in ocular surface physiology. METHODS: Ocular surface mucus was collected from normal volunteers as N-acetyl cysteine (NAcCys) washes or directly from the speculum after cataract surgery. To assess the influence of surface health on mucins, NAcCys washings were also obtained from patients with symptoms, but no clinical signs of dry eye (symptomatics). Mucins were extracted in guanidine hydrochloride (GuHCl) with protease inhibitors. Buoyant density of mucin species, a correlate of glycosylation density, was followed by reactivity with anti-peptide core antibodies. Mucin hydrodynamic volume was assessed by gel filtration on Sepharose CL2B. RESULTS: Surface fluid and mucus contained soluble forms of MUC1, MUC2, MUC4, and MUC5AC and also the same species requiring DTT solubilisation. Reactivity with antibodies to MUC2 and MUC5AC peaked at 1.3-1.5 g/ml in normals, while dominated by underglycosylated forms in symptomatics. Surface mucins were predominantly smaller than intracellular species. MUC2 size distributions were different in symptomatics and normals, while those of MUC5AC were similar in these two groups. CONCLUSIONS: A reduction in surface mucin size indicates post-secretory cleavage. Dissimilarities in surface mucin glycosylation and individual MUC size distributions in symptomatics suggest changes in preocular mucin that might precede dry eye signs.

Membrane-associated mucins in normal human conjunctiva.

PURPOSE: To examine the presence of specific membrane-associated mucins in normal human conjunctiva. METHODS: Glycoconjugates were extracted from membranes with two detergents: octylglucoside and Triton X114. Mucins were separated by cesium chloride density gradient centrifugation. Size was assessed by gel filtration on Sepharose CL2B and charge by ion-exchange chromatography on MonoQ. Cross reaction with antibodies against mucin gene products was assessed in blots of electrophoresis gels. RESULTS: Extraction of total tissue membranes yielded material with a buoyant density typical of mucins. Gel filtration showed material reacting with antimucin antibodies in a range of molecular sizes. Agarose electrophoresis confirmed the presence of MUC1 and MUC4 and the absence of MUC2 or MUC5AC. Isolation of membrane mucins by sequential, exhaustive extraction with octylglucoside followed by Triton X114 suggested the existence of mucins in different membrane environments. Reagents to carbohydrate epitopes revealed high mobility material, comigrating with MUC1 and MUC4. Low mobility membrane-bound mucins did not cross-react with any antibodies to mucin genes known to be expressed in human conjunctiva. CONCLUSIONS: Membrane-associated mucins are distinct from secreted mucins in normal human conjunctiva. MUC1 and MUC4 mature products decorate the membranes of conjunctival epithelial cells. Their segregation between octyl glucoside and the detergent and aqueous phases of Triton X114 suggests a variety of membrane anchoring modes.

Secreted human conjunctival mucus contains MUC5AC glycoforms.

This study addresses the extent of variation in secreted end-product mucins in human conjunctival mucus. The aim was to determine whether the variety of mucin species found was encompassed by the mucin genes which have been cloned to date. Extraction into guanidine hydrochloride and separation of mucin constituents, by a combination of cesium chloride density gradient centrifugation, size separation on Sepharose CL-2B, MonoQ ion exchange chromatography and agarose gel electrophoresis, demonstrates a complex mixture of mucins. Sample size limitations precluded compositional amino acid analysis. MUC 5AC and MUC1, 2, and 4 are all detected in the buoyant density range 1.3-1.5 g/ml by antibody binding. The mucins vary in size from >40 x 10(6)to <97 x 10(3)Da. A wide range of molecular size was confirmed using rate zonal centrifugation. The presence of smaller species contrasts with other mucous secretions similarly studied. In each size range are low, medium, and high charge mucins. Sialylation predominates in the medium charge and sulfate in the high charge. Only MUC5AC cross-reactivity is maintained throughout the analysis. It is detected in large and medium sized mucins but accounts for only the least mobile mucins within copurified species of similar density, size, and charge resolved using agarose electrophoresis. MUC5AC cross-reactivity is also detected in both medium and high charge species, indicating the presence of glycoforms.

Polydispersity of normal human conjunctival mucins.

PURPOSE: To isolate all constituent mucins from human conjunctival mucus. METHODS: Mucins were extracted from human conjunctiva in guanidine hydrochloride and protease inhibitors. The mucins were isolated by density gradient centrifugation, gel filtration, and ion exchange chromatography. Throughout purification, the mucin profile was monitored by agarose electrophoresis and vacuum blotting. Blots were probed for peptide and carbohydrate epitopes. The latter included IE3 and TKH2 specific for Tn and sialyl-Tn, respectively, considered tumor-related antigens. In vivo impression cytology specimens of normal conjunctival goblet cells also were probed with the same reagents. Oligosaccharides were released from isolated mucins by alkaline beta-elimination and then size fractionated. RESULTS: Human conjunctival mucins consist of at least three size populations; the largest is excluded on Sepharose CL2B. The two largest populations are polydisperse. Their overall electrophoretic pattern is conserved between individuals. Similar charge distributions were detected in different buoyant density ranges from the density gradient centrifugation: a less charged population containing three components and a highly charged population with two components on agarose electrophoresis. Cross-reaction with IE3 and TKH2 was detected throughout purification in the largest mucins, which were presumably mature, and in impression cytology. Oligosaccharides from mucins in each buoyant density were largely in the monosaccharide and disaccharide range, consistent with Tn and sialyl-Tn standards. CONCLUSIONS: Secreted human conjunctival mucins are polydisperse, with discrete components appearing consistently in pooled and individual samples. They have a unique oligosaccharide pattern containing Tn and sialyl-Tn. This indicates normal roles in normal human ocular mucins for these antigens, which are disease markers in other tissues.

The mechanical properties of the human lens capsule following capsulorhexis or radiofrequency diathermy capsulotomy.

OBJECTIVE: To quantify the biomechanical properties of the capsulotomy edge following continuous-tear circular capsulorhexis (CTCC) or radiofrequency (RF) diathermy capsulotomy. METHODS: A test apparatus was constructed that allowed controlled stretching of capsulotomy edges following CTCC or RF diathermy capsulotomy. The lens contents were removed by phacoemulsification to permit the implantation of probes that exerted a test force on the capsulotomy edge and were moved in diametrically opposite directions using computer-controlled stepping motors. The magnitude of the force was measured during the capsule stretch, which allowed precise determination of the degree of capsular distention at the time of capsular rupture. Selected capsular edges were subsequently examined by scanning electron microscopy. RESULTS: The capsulotomy edge produced by CTCC was significantly stronger (P < .001) than that following RF. The mean (+/-SD) force to achieve capsule rupture was 0.15 +/- 0.06 N with CTCC compared with 0.02 +/- 0.01 N with RF. The mean (+/-SD) increase in the capsulotomy circumference was significantly greater with CTCC at 53% +/- 14.5% compared with RF at 18% +/- 8.5% (P < .001). Scanning electron microscopy disclosed a smooth edge for the CTCC capsulotomy. In contrast, multiple irregularities were seen in the edge following RF. CONCLUSIONS: Continuous-tear circular capsulorhexis provides a stronger capsulotomy and is the preferred method in routine cataract surgery. However, RF diathermy capsulotomy may have a useful role in conditions unfavorable to the safe completion of CTCC.

Conjunctiva : organ and cell culture.

The conjunctiva is the mucous membrane of the eye. It is a delicate transparent epithelium with its own stroma overlying the tough white sclera, which forms the ball of the eye. Only at the circular limbus, where the sclera meets the transparent cornea, and at the eyelids, is the conjunctiva firmly attached, thus permitting free movement of the eye The loose conjunctiva between these points of attachment folds into a blind sac deepest under the upper and lower lids. Removed in one piece from the eye, the conjunctiva is a flimsy sheet (usually with adherent fascial tissue called Tenon's capsule) with an 1l-mm circular defect in the center.

Visual disturbance of the uncovered eye in patients wearing an eye patch.

We questioned 104 consecutive eye casualty patients about any visual disturbance experienced while wearing an eye patch as part of their treatment. Many (31%) reported momentary loss of vision in the uncovered eye. Some experienced this while driving. It was more common (p < 0.0008) if the 'dominant eye' had been patched (47%) rather than the 'non-dominant eye' (16%). In a separate experiment, a number of co-operative subjects were provided with a translucent-coloured occluder to be worn over each eye in turn. They reported a recurring coloured interference in the uncovered eye sparing the monocular crescent. We propose that the loss of vision in the unpatched eye is due to binocular rivalry suppression by the patched eye. This visual disturbance may be a cause of anxiety or risk for the patient. Patched patients should be warned this may occur, and advised to avoid driving or operating machinery.