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.

Lateral canthotomy and inferior cantholysis: an effective method of urgent orbital decompression for sight threatening acute retrobulbar haemorrhage

Retrobulbar haemorrhage (RBH) occurs in a variety of situations. It can complicate facial fractures, orbital surgery and retrobulbar injections and can occur spontaneously. It is relatively uncommon and sight-threatening RBH is even less common. If not detected early enough it can lead to devastating loss of vision. We have collected five cases of acute RBH, following trauma, associated with a profound reduction in vision. In each case a permanent loss of vision was avoided using a lateral canthotomy and inferior cantholysis approach to obtain urgent orbital decompression.

Visual function after penetrating keratoplasty for keratoconus: a prospective longitudinal evaluation

AIMS

To evaluate visual function and vision specific health status in patients undergoing penetrating keratoplasty for keratoconus.

METHODS

A prospective longitudinal study measuring logMAR visual acuity, contrast sensitivity, disability glare, binocular visual field, stereoacuity, and subjective visual function (VF-14) was conducted on 18 patients with keratoconus undergoing penetrating keratoplasty (PK), including six patients who had already had PK in the fellow eye. Data were collected preoperatively and at 3, 9, and 18 months after surgery.

RESULTS

Within 3 months of surgery there was significant improvement in aided visual acuity, contrast sensitivity, and stereoacuity (p<0.05); disability glare (p<0.05) no longer had a significant detrimental effect on these variables. VF-14 score improved significantly throughout the postoperative period (p<0.05). There was significant correlation of the VF-14 score with aided visual acuity, binocular visual field, and stereoacuity. Postoperative astigmatism (<4D v >4D) did not affect the VF-14 score significantly.

CONCLUSIONS

There is substantial and rapid improvement in visual function and vision specific health status in keratoconic patients as a result of uncomplicated penetrating keratoplasty.

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.

Management of pellucid marginal corneal degeneration

PURPOSE

A retrospective study to ascertain the management of pellucid marginal corneal degeneration (PMCD).

METHOD AND RESULTS

Sixteen patients (average age 42.6 years) presented with PMCD. PMCD was bilateral in 13 and unilateral in 3 patients. Eight eyes underwent surgery. Nineteen eyes were managed non-surgically. Surgery involved corneal wedge excision (WE) (6 eyes), penetrating keratoplasty (PK) (3 eyes) and lamellar thermo-keratoplasty (LTK) (1 eye). Immediate pre-operative average visual acuity (VA) was 6/24, 6/10 and 6/60 with an average pre-operative astigmatism of 11.40 D, 9.75 D and 20.5 D for WE, PK and LTK respectively. After an average post-operative follow-up of 57 months, 66 months and 1 year, the average astigmatism was 8.90 D, 4.63 D and 6.00 D with an average final VA of 6/19, 6/15 and 6/6 for WE, PK and LTK respectively. In the nonsurgical group, at presentation, 40% of eyes had a VA of 6/12 or better. After an average follow-up period of 32.3 months, 80% of eyes had a visual acuity of 6/12 or better. Optical correction was achieved with spectacles and or contact lenses.

CONCLUSIONS

Surgical correction for PMCD provides poor long-term reduction of astigmatism. Patients with PMCD may be adequately corrected in the long term by the use of scleral fitted gas-permeable contact lenses.

An efficient intelligent analysis system for confocal corneal endothelium images

A confocal microscope provides a sequence of images of the corneal layers and structures at different depths from which medical clinicians can extract clinical information on the state of health of the patient's cornea. A hybrid model based on snake and particle swarm optimisation (S-PSO) is proposed in this paper to analyse the confocal endothelium images. The proposed system is able to pre-process images (including quality enhancement and noise reduction), detect cells, measure cell densities and identify abnormalities in the analysed data sets. Three normal corneal data sets acquired using a confocal microscope, and three abnormal confocal endothelium images associated with diseases have been investigated in the proposed system. Promising results are presented and the performance of this system is compared with manual and two morphological based approaches. The average differences between the manual and the automatic cell densities calculated using S-PSO and two other morphological based approaches is 5%, 7% and 13% respectively. The developed system will be deployable as a clinical tool to underpin the expertise of ophthalmologists in analysing confocal corneal images.

Severe sclerokeratitis due to Pseudomonas aeruginosa in noncontact-lens wearers

PURPOSE

To review the clinical presentation, treatment and outcome in four cases of severe anterior segment infection by Pseudomonas aeruginosa unrelated to contact lens wear.

METHODS

Four cases presenting over an 18 month period were reviewed.

RESULTS

The cases had variable presenting features and outcomes. Complications such as persistent infection, corneal thinning and phthisis bulbi were noted. Possible factors influencing adherence and tissue disruption are discussed.

CONCLUSIONS

Suspicion of infection by P. aeruginosa and prompt isolation of the organism is needed early in the course of disease. Intensive and prolonged treatment with parenteral and topical antibiotics combined with judicious use of topical steroid gives the best chance of a favourable outcome.

An epidemic of mass hysteria in a village in West Bengal

This is a report of an outbreak of mass hysteria, attributed to an unknown infectious disease, in a small village near Baruipur, South 24 Parganas district of West Bengal. The epidemic was triggered following the death of 2 persons of the same family on the same day. Thereafter, several other family members and villagers became ill and complained of similar symptoms. They were hospitalized for observation and all were discharged after a couple of days. We report the detailed sequence of events and the management of this mini epidemic.

Sociocultural context of suicidal behaviour in the sundarban region of India

The role of mental illness in nonfatal deliberate self-harm (DSH) is controversial, especially in Asian countries. This prospective study examined the role of psychiatric disorders, underlying social and situational problems, and triggers of DSH in a sample of 89 patients hospitalised in primary care hospitals of the Sundarban Delta, India. Data were collected by using a specially designed DSH register, Explanatory Model Interview Catalogue (EMIC), and clinical interview. Psychiatric diagnosis was made following the DSM-IV guidelines. The majority of subjects were young females (74.2%) and married (65.2%). Most of them (69.7%) were uncertain about their "intention to die," and pesticide poisoning was the commonest method (95.5%). Significant male-female differences were found with respect to education level, occupation, and venue of the DSH attempt. Typical stressors were conflict with spouse, guardians, or in-laws, extramarital affairs, chronic physical illness, and failed love affairs. The major depressive disorder (14.6%) was the commonest psychiatric diagnosis followed by adjustment disorder (6.7%); however 60.7% of the cases had no psychiatric illness. Stressful life situations coupled with easy access to lethal pesticides stood as the risk factor. The sociocultural dynamics behind suicidal behaviour and community-specific social stressors merit detailed assessment and timely psychosocial intervention. These findings will be helpful to design community-based mental health clinical services and community action in the region.

Centration of donor trephination in human corneal transplantation

PURPOSE

To develop and evaluate a new method to quantify centration of the trephined donor cornea relative to the limbus.

METHODS

After human donor corneas were trephined for penetrating keratoplasty, the remaining corneoscleral discs were stained and subjected to image analysis. The centration of the excised donor cornea relative to the limbus was calculated by measuring their centroids from the "captured" images.

RESULTS

Fifty-two corneoscleral discs were analyzed. The average deviation from the centre was 0.32 mm (SD, 0.18 mm). Neither surgeon nor the type of trephine significantly influenced the mean centroid deviation.

CONCLUSION

We have developed and evaluated a method to quantify centration of human donor cornea. In a small series, decentration did not correlate significantly with either the surgeon or the trephine.

An Unusual Case of a Primary Hyperparathyroidism Mimic

A 32-year-old lady with a history of bulimia nervosa was noted to have a raised adjusted calcium of 2.94mmol/L associated with high parathyroid hormone (PTH) 17.2pmol/L. On review, she had an apparent hypercalcaemia for at least three years, and also had a chronic, severe alkalosis with a bicarbonate up to 81.9mEQ/L. Ionised calcium during that time had actually been low, down to 1.03mmol/L. This case highlights the effects of alkalosis on calcium, as more albumin is available for binding to ionised calcium. This results in a low ionised calcium, which triggers PTH release and overall leads to raised adjusted calcium levels. Clinicians may misdiagnose a similar patient with primary hyperparathyroidism and treatment would cause worsening of true hypocalcaemia.

A study on mortality and morbidity pattern of acute childhood poisoning cases admitted in block primary health centres of Sundarban, West Bengal

A hospital - record based study was conducted in Sundarban of West Bengal to explore the profile of mortality and morbidity pattern of acute accidental poisoning among children. Sundarban is an underdeveloped coastal region of West Bengal. Three years retrospective (1999 - 2001) data of childhood accidental poisoning cases were collected from the indoor admission registers and case history sheets of 11 Block Primary Health Centers (BPHC) of the region. A total of 1056 children with accidental poisoning were admitted during those three years of which 58% were males. Mean age of males was slightly higher than females in all the three years. Organophosphorus pesticide poisoning was the commonest.

Deliberate self-harm prevention in the Sundarbans region need immediate public health attention

Deliberate self-harm is a major public health problem. This study is aimed to examine the sociodemographic characteristics of both non-fatal and fatal deliberate self-harm cases admitted at the 13 block primary health centres of the Sundarbans region under South 24 Parganas district, West Bengal. Retrospective deliberate self-harm data from the admission registers of 13 block primary health centres was collected for the year 1999. A total of 1850 deliberate self-harm cases (639 males and 1211 females) were admitted at the 13 block primary health centres, of which 159 (60 males, 99 females) were fatal (completed suicide). A higher fatality rate for male than female (9.4% compared to 8.2%) was observed. Women (65.5%), especially of younger age groups constituted the major cases. Poisoning (96.9%) was the commonest method of self-harm. Easy availability of pesticides was a common factor. Marital status and seasonal trend (March-April) had important contribution in self-harm incidents. Planned psychosocial intervention as a part of community mental health programme may help to reduce the deliberate self-harm morbidity and mortality at this primary care level.