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Biomedical subjects

J P Craig

Publications and source records attributed to J P Craig.

At least 19 recordsLinked to original sources
PubMed2001

In vivo confocal microscopy of corneal epithelial ingrowth through a laser in situ keratomileusis flap buttonhole.

We report a case of epithelial ingrowth through a buttonhole 6 months after laser in situ keratomileusis. Elevation topography showed irregular astigmatism and an unreliable pachymetric map. In vivo confocal microscopy showed an epithelial basal cell mosaic with prominent borders and distinct nuclei. No corneal nerves were identified in any image. Cells in the anterior stroma possessed bright, reflective nuclei and appeared to form clusters. The interface between the stromal bed and the flap had formation of nests of fibrotic tissue and epithelial cells.

Adult↗
PubMed2001

Safety and predictability of laser in situ keratomileusis enhancement by flap reelevation in high myopia.

PURPOSE: To evaluate the safety and predictability of laser in situ keratomileusis (LASIK) retreatment following primary procedures for high myopia and astigmatism. SETTING: Corneal Diseases and Excimer Laser Research Unit, Department of Ophthalmology, University of Dundee, Dundee, United Kingdom. METHODS: This prospective observational study of retreatment comprised a cohort of 109 eyes having primary LASIK for high myopia and astigmatism with a spherical equivalent (SE) of -9.70 diopters (D) +/- 4.06 (SD). Twenty-four eyes (22%) with an initial myopic SE of -9.83 +/- 3.50 D, a comparable subset of the entire group (P < .05), had retreatment for residual myopia (-3.02 +/- 2.17 D) to improve uncorrected visual acuity (UCVA) by reelevating the corneal flap and ablating the stromal bed. RESULTS: The mean follow-up after retreatment was 12.8 +/- 5.1 months (range 1.5 to 24 months; 19 eyes >/=6 months, 13 eyes > or = 12 months). The mean myopic SE was reduced to +0.53 +/- 0.62 D at 1 week, +0.05 +/- 0.50 D at 1 month, +0.30 +/- 0.50 D at 6 months, and +0.18 +/- 0.42 D at the latest follow-up, 12.8 months. At the latest review, 62% of eyes were within +/-0.50 D of emmetropia and 100% were within +/-1.00 D. The mean refraction did not alter statistically between 1 week and subsequent times. The mean UCVA improved from 6/30 prior to retreatment to 6/9 at the latest follow-up. Uncorrected visual acuity of 6/6 or better, 6/9 or better, and 6/12 or better was achieved by 33.0%, 75.0%, and 95.8% of eyes, respectively. No significant complications that led to a loss of best corrected visual acuity were encountered, although retreatment procedures were more uncomfortable than primary procedures and self-limiting; epithelial ingrowth that did not threaten vision was common, and 2 patients complained of nighttime visual symptoms. CONCLUSIONS: Retreatment of residual myopia by reelevating the flap was relatively safe and predictable, with a low risk of sight-threatening complications. However, longer term studies may be required to detect late complications.

Adult↗
PubMed2001

Comparison of corneal thickness measurements using ultrasound and Orbscan slit-scanning topography in normal and post-LASIK eyes.

PURPOSE: To compare corneal thickness measurements made by ultrasonic and slit-scanning techniques in normal eyes and in eyes after laser in situ keratomileusis (LASIK). SETTING: Corneal Diseases and Excimer Laser Research Unit, University of Dundee, Dundee, Scotland. METHODS: Central corneal thickness (CCT) was measured in 101 eyes of 59 normal subjects and in 30 eyes of 21 post-LASIK patients. Measurements were made with an Orbscan slit-scanning elevation topographer and immediately afterward with an ultrasound pachymeter. RESULTS: The difference in mean CCT between ultrasound (538.0 microm +/- 36.7 [SD]) and Orbscan (566.6 +/- 40.7 microm) pachymetry was statistically significant (P <.001) in the normal eyes; the Orbscan measurement was approximately 28 microm higher than that of the ultrasound pachymeter. The difference in mean CCT between the ultrasound and the slit-scanning techniques was also statistically significant in the post-LASIK eyes (mean values 475.3 +/- 50.3 microm and 461.9 +/- 74.2 microm, respectively; P <.0001). Differences in CCT in individual subjects were much more variable in the post-LASIK eyes than in the normal eyes. The Bland and Altman method for assessing clinical agreement between 2 instruments showed that in 95% of cases, the CCT measurements with both instruments would be within 65 microm in normal eyes and 150 microm in post-LASIK eyes. CONCLUSION: Central corneal thickness measurements were, on average, 28 microm higher with the Orbscan than with the ultrasound pachymeter in normal eyes and 13 microm lower in post-LASIK eyes. The degree of variability within each group indicated that these 2 techniques are not clinically comparable, precluding interchangeable use of their data in planning or assessing corneal surgery.

Adult↗
PubMed2001

Differential diagnosis of corneal oedema assisted by in vivo confocal microscopy.

The purpose of this study was to demonstrate microstructural differences between clinically similar, but aetiologically different, cases of corneal oedema in four subjects. In vivo confocal microscopy highlighted oedema of the basal epithelium, prominent nerve-keratocyte interactions, and typical 'epithelialization' of the endothelium in a case of iridocorneal endothelial syndrome; however, a similar microstructural appearance was observed in a case of presumed herpetic disciform keratitis. The latter diagnosis was subsequently revised on this basis. Confocal examination of Fuchs' endothelial dystrophy demonstrated oedema of the basal epithelium, prominent wing cells, anterior stromal alterations, fibrosis of Descemet's membrane and a typical 'strawberry' appearance of the endothelium. In contrast, in vivo microstructural examination of bilateral keratoconus with hydrops confirmed oedema mainly involving the epithelium and anterior stroma. In vivo confocal microscopy allows the clinician to observe the living cornea at a microstructural level and to better diagnose and differentiate borderline or unusual cases of corneal oedema.

Adult↗
PubMed2001

Imaging posterior polymorphous corneal dystrophy by in vivo confocal microscopy.

To identify features of posterior polymorphous dystrophy (PPMD) by in vivo confocal microscopy, the corneas of a female patient with PPMD were exam ned using slit-lamp biomicroscopy and slit-scanning in vivo confocal microscopy. Characteristic endothelial vesicular and band lesions were seen clinically and easily identified using in vivo confocal microscopy. However endothelial pleomorphism, an increased density and reflectance of posterior stromal keratocytes, and prominence of corneal nerves were also delineated. In vivo confocal microscopy enhances clinicopathological diagnosis and follow up of corneal dystrophies with subtle clinical presentations, such as PPMD.

Corneal Dystrophies, Hereditary↗
PubMed2001

Microstructural assessment of rare corneal dystrophies using real-time in vivo confocal microscopy.

PURPOSE: To analyse and describe three cases of rare corneal dystrophy and highlight their in vivo microstructural features. METHODS: Subject 1 was diagnosed with a posterior stromal fleck corneal dystrophy Two of her three children were also affected. Subjects 2 and 3 exhibited an almost identical clinical appearance on biomicroscopic examination, such that both clinically were diagnosed as having pre-Descemet's dystrophies. All subjects underwent in vivo confocal microscopy and approximately 300 sequential digital images were obtained and analysed for each cornea. RESULTS: In vivo confocal microscopy of subject 1 demonstrated an abnormal appearance of numerous large ovoid particles, measuring 50-70 microm in diameter in the mid and posterior stroma as well as smaller hyperreflective dot-like intracellular deposits, of less than 1 microm diameter. Despite the near-identical clinical appearance, subjects 2 and 3 could be clearly differentiated by in vivo confocal microscopy. Subject 2 exhibited small, irregular, optically dense particles, mainly in the anterior stroma, whereas subject 3 possessed classical involvement of the stroma immediately adjacent to Descemet's membrane, with numerous regular small, hyperreflective particles. CONCLUSIONS: The ability of in vivo confocal microscopy to localize and accurately measure various elements in different corneal layers may help to resolve whether abnormalities are intra- or extracellular, and aid clearer differentiation of rare corneal disorders.

Adult↗
PubMed2001

The waiting game: natural history of a cataract waiting list in New Zealand.

AIMS: To identify the demographic and visual function of patients on the reserve waiting list for cataract surgery at a large public hospital within New Zealand and to determine the ultimate outcome of those on a priority-based, rationed, health-care waiting list. METHODS: Patients from a defined geographical population, placed on a reserve waiting list for possible cataract surgery, during the period January 1997 to March 2000, were invited to attend for further clinical assessment and asked to complete a visual assessment questionnaire. RESULTS: Of 193 patients in the pilot study group who had been on the reserve waiting list for a mean of 18.2 +/- 11.6 months (range 0.1-62.7 months), only 94 (49%) were deemed suitable for, and subsequently underwent, surgery in the public sector. Forty-nine (25%) had undergone surgery earlier, the majority of these (84%) in the private sector. A further 23 (12%) patients were deceased, four (2%) declined surgery and in six (3%) cataract surgery was no longer indicated. The remaining 11 (6%) patients could not be traced. Patients still awaiting surgery had a mean age of 77.2 years (range 48-95 years). Fifty-four were women. Vision had deteriorated by a mean of 0.05 LogMAR units, from Snellen equivalent 6/30 at listing to 6/36, over this time. CONCLUSIONS: Current methods of prioritization for cataract surgery are imperfect, as are the resources for performing adequate levels of cataract surgery. Analysis of a residual waiting list for cataract surgery highlights that the majority (51%) do not ultimately progress to cataract surgery in the public sector for a variety of reasons. During a mean waiting time of 1.5 years vision further deteriorates in this predominantly older population.

Aged↗
PubMed2001

The Auckland Cataract Study: demographic, corneal topographic and ocular biometric parameters.

PURPOSE: To determine patient demographics and the ocular biometric parameters in patients presenting for cataract surgery within the public hospital system, in a defined New Zealand population. METHOD: Prospective study of 502 eyes of 488 consecutive patients undergoing cataract surgery. A clinical assessment, including refraction, keratometry (K), A-scan ultrasound and Orbscan II computerized topography was performed on each eye. RESULTS: The mean age of the group was 74.9 +/- 9.8 years (mean +/- SD) with a female predominance (62%). Ethnic origin included 72% European, 8% Maori, 10% Pacific Islander, 4% Asian, 3% Indian and 3% other ethnic origins. The mean Log MAR visual acuity of eyes prior to cataract surgery was 0.88 +/- 0.57 (approximately 6/48(-1)). Corneal topographic (keratometric) maps were classified into five groups: 34% round, 10% oval, 31% symmetrical bow tie, 12% asymmetrical bow tie and 13% irregular. The mean steepest K measurement was 44.1 +/- 1.7 D, the median keratometric astigmatism 0.89 D (range 0.0-6.5 D) and the steepest corneal meridian was horizontal in 50% and vertical in 43%. Seven per cent of corneas were spherical. Refraction revealed a mean sphere of 0.0 +/- 3.1 D and a mean cylinder of -1.2 (range 0.0-7.5 D). Refractive astigmatism was with-the-rule in 15%, against-the-rule in 50% and oblique in 15%, with 20% spherical. Axial length was a mean of 23.14 +/- 1.03 mm. CONCLUSION: Patients presenting for cataract surgery in this study were predominantly elderly, female, of European Caucasian ethnicity and exhibited relatively poor corrected visual acuity in the affected eye. Interestingly, 41% of eyes demonstrated bow-tie topographic patterns, largely exhibiting with-the-rule astigmatism. However, assessment by keratometry or refraction highlighted against-the-rule more frequently; this may have implications for combined cataract and astigmatic surgery. The mean axial length was slightly shorter than expected for a group of predominantly European ethnic origin, although the mean refractive error was emmetropic.

Adult↗
PubMed2000

Functional, psychological, and satisfaction outcomes of laser in situ keratomileusis for high myopia.

PURPOSE: To identify factors that motivate patients to seek laser in situ keratomileusis (LASIK) treatment for myopia and establish subjective levels of functional improvement and satisfaction across a range of indices after LASIK surgery. SETTING: The Corneal Diseases and Excimer Laser Research Unit, University of Dundee, Ninewells Hospital and Medical School, Dundee, Scotland. METHODS: In this questionnaire-based, cross-sectional study, an anonymous 34-item questionnaire was forwarded to 50 consecutive patients in a prospective study who had had LASIK for high myopia by a single surgeon at a single center. The questionnaire used visual analog scales, anchored at each end by an adjectival descriptor. The mean preoperative myopia was -10.7 diopters +/- 4.4 (SD). Seventy-six percent of eyes (83% of patients) achieved post-LASIK uncorrected visual acuity (UCVA) of 6/12 or better; 1 eye lost 2 lines of corrected Snellen visual acuity. RESULTS: A 98% reply rate was achieved. The most common motivating factor for pursuing LASIK was to improve UCVA (88%); only 21% rated improved cosmesis as an important motive. Most patients (81% to 100%) reported functional improvement across the spectrum of visual tasks assessed, although 8.8% reported difficulty with nighttime driving. Ninety-six percent felt their UCVA was as good as anticipated, 97.9% were satisfied with the speed of visual improvement, 93.8% achieved the goals for which they had surgery, 97.9% reported an improved quality of life, and 97.9% were satisfied with the overall outcome of LASIK. CONCLUSIONS: Using an anonymous, wide-ranging questionnaire, high levels of functional improvement and satisfaction with the speed of visual recovery and outcome were reported by patients after LASIK for high myopia. Nighttime driving symptoms of variable severity were, however, noted by 8.8% of patients, despite high levels of satisfaction with other aspects of visual function.

Adult↗
PubMed2000

The role of tear physiology in ocular surface temperature.

PURPOSE: To determine whether the more rapid cooling of the tear film in dry eyes is related to other tear film parameters, a battery of tear physiology tests was performed on dry eye patients and control subjects. METHODS: Tear evaporation rate was measured with a modified Servomed (vapour pressure) evaporimeter and ocular temperature with an NEC San-ei 6T62 Thermo Tracer in 9 patients diagnosed as having dry eye and in 13 healthy control subjects. Variability in temperature across the ocular surface was described by the temperature variation factor (TVF). Lipid layer structure and tear film stability were assessed with the Keeler Tearscope and tear osmolality was measured by freezing point depression nanolitre osmometry. RESULTS: The data were explored by principal component analysis. The subjects with and without dry eye could be separated into two distinct groups entirely on the basis of their tear physiology. Dry eye patients exhibited higher tear evaporation rates, osmolalities and TVF, lower tear film stabilities and poorer-quality lipid layers than the control subjects. A significant linear relationship was found to exist between tear evaporation rate and TVF for all subjects (R2 = 0.242, p = 0.024). CONCLUSIONS: Rapid cooling of the tear film in dry eyes appears to be related to the reduced stability of the tears and the increased rate of evaporation. The higher latent heat of vaporisation, associated with the increased evaporation in dry eyes, may account for the increased rate of cooling of the tear film in this condition.

Adult↗
PubMed1997

Suppression of the immune response to diphtheria toxoid in murine schistosomiasis.

Studies in humans and experimental animals indicate that infection with schistosomes results in impaired immune response to a variety of antigens. Since artificial immunization against a number of infections is frequently attempted in populations in which schistosomiasis is endemic, we have attempted to determine whether this impairment could be demonstrated in response to a commonly used immunogen. We have compared the serum antitoxin response to diphtheria toxoid (DTd) in normal, uninfected mice with that in mice bearing schistosome infections of different duration. Animals were infected with 100 Schistosoma mansoni cercariae 16, 12, 8, 4 and 2 weeks prior to, on the same day as, and 4 weeks after the first of three 1 microgram doses of DTd given at 3 week intervals. The antitoxin level of each mouse was taken as the mean of two sera obtained 1 and 2 weeks after the 3rd dose of DTd. The mean antitoxin level in uninfected-immunized control mice was 0.0457 Antitoxin Units (AU) ml-1. 71% of mice in this group developed antitoxin levels > or = 0.01 AU ml-1. Only 28% of the infected-immunized mice achieved antitoxin levels > or = 0.01 AU ml-1. In infected-immunized mice with infections of all durations, both the percentage of mice with > or = 0.01 AU ml-1 (0 to 50%) and mean antitoxin levels (0.003 to 0.016 AU ml-1) were lower than in uninfected-immunized mice. Antitoxin levels in animals infected 16, 12, 8 and 2 weeks prior to, simultaneously with, and 4 weeks after the first dose of DTd were significantly lower (P = < 0.05) than those of controls. Mice infected 4 weeks prior to the first dose of DTd had antitoxin levels 64% below controls but this difference was not significant. If similar immunosuppression occurs in human schistosomiasis, these findings may have implications for childhood immunization programs in areas where schistosomiasis is endemic.

Animals↗
PubMed1997

Importance of the lipid layer in human tear film stability and evaporation.

PURPOSE: Previous work on rabbits has demonstrated a four-fold increase in tear evaporation when the tear lipid layer is removed. However, in vitro work has suggested that the lipid layer does not play a role in retarding evaporation of the aqueous layer. The importance of the lipid layer in human tear film stability and evaporation was determined in the current study by measurement of these parameters in the same individuals. METHODS: The left eyes of 161 normal and dry eye subjects (72 males, 89 females), with an age range of 13 to 85 years, were examined. Tear evaporation was derived from the vapor pressure gradient measured with a modified Servomed evaporimeter. Lipid layer structure and noninvasive break-up time (NIBUT) were assessed clinically, by specular reflection, with the Keeler Tearscope. Lipid layer structure was categorized into marmoreal (open and closed meshwork), flow, amorphous, and colored fringe (normal and abnormal) patterns. These observed patterns reflect lipid layer thickness. Ambient temperature and relative humidity remained fairly constant throughout the experiment. RESULTS: Tear evaporation rate was found to vary significantly with different lipid layer patterns. Eyes with no visible lipid layer, or exhibiting an abnormal colored fringe pattern (with clumping of lipid amidst areas of little or no lipid cover), demonstrated a significantly higher rate of evaporation of the tear film (p < 0.001). There were no significant differences amongst the remainder of the patterns. The NIBUT was also found to vary significantly with lipid layer pattern (p < 0.001), with the absent or abnormal colored fringe lipid patterns exhibiting the poorest stability. CONCLUSIONS: Where the human lipid layer is absent, or is not confluent, and the tear film is unstable, tear evaporation is increased four-fold. However, where there is a stable, intact lipid layer, regardless of lipid thickness, tear evaporation is retarded.

Adolescent↗
PubMed1995

Effect of age on tear osmolality.

Certain aspects of tear physiology change with age (reflex secretion and stability), whereas others remain unchanged (tear volume, evaporation rate, basal tear production). To establish the variation in tear osmolality with age, 0.2 to 0.4 microliter samples were collected from 50 normal males and 50 normal females (age range 17 to 75 years). Nanoliter aliquots of the samples were analyzed by freezing point depression nanoliter osmometry. Mean tear osmolality for the whole group was 303.6 +/- 13.0 mOsm/kg and was not significantly affected by age (r2 = 0.014, p = 0.378). For males the mean was 307.1 +/- 14.4 and for females 300.1 +/- 10.4 mOsm/kg, a significant gender difference (p = 0.006). Males under age 41 had tear osmolality which was not significantly different from that of males over 41 years of age (307.7 +/- 15.6 and 305.7 +/- 11.5 mOsm/kg, respectively, p = 0.671) but the mean tear osmolality for females under age 41 years (297.6 +/- 11.2 mOsm/kg) was significantly different from that of older females (304.8 +/- 6.7 mOsm/kg, p = 0.017). There was no significant correlation between age and osmolality for males (r2 = 0.003, p = 0.699), but there was a significant correlation for females (r2 = 0.159, p = 0.004). Males under age 41 years have a significantly higher mean tear osmolality than females under 41 years of age (p = 0.003). The age and gender differences found for tear osmolality can be accounted for by the low values in young females, which may be related to the increased tear flow observed in young females. A reduction in this high flow rate to a more "normal" level in older females may account for the rise in tear osmolality to a level which is not significantly different from that of older males. Generally in normal eyes, the osmolality of tears remains within normal limits and is not affected by age.

Adolescent↗