Tahra AlMahmoud

Correlation between Refractive Error, Corneal Power, and Thickness in a Large Population with a Wide Range of Ametropia

PURPOSE To determine the correlations between mean keratometry (KM), central corneal thicknesses (CCT), and cycloplegic spherical equivalent (SE) in patients with a wide range of ametropia. METHODS Retrospective analysis of the excimer laser surgery database at the University of Ottawa Eye Institute between 1993 and 2008 was performed. This study included 3395 eyes from 1858 subjects. The refractive error ranged from +6.75 to -14.00 D. CCT was obtained either by ultrasound pachymetry or anterior segment tomography. Keratometry was determined using an autokeratorefractometer. RESULTS In the myopic group, the SE was observed to be inversely proportional to the KM (correlation coefficient, -0.18; P < 0.01). The KM and CCT were also inversely proportional (-0.11; P < 0.01). In hyperopes, a correlation between the cycloplegic SE and KM was also found (-0.25; P < 0.01), but the CCT did not correlate with either of these metrics. A direct correlation for the myopic group was found between KM and the difference in power of the principal meridians (keratometric astigmatism [KA]) (0.08; P < 0.01). This relationship was not observed for the hyperopic group. Within the myopic group the SE correlated with the refractive astigmatism (RA) (-0.04; P = 0 0.04). In all groups, a strong correlation was observed between RA and KA (0.78; P < 0.01). CONCLUSIONS In the myopia group, the KM showed close correspondence with KA and an inverse relationship with SE and CCT. In hyperopes, an inverse correlation between the KM and SE was found, but no correlation with CCT was evident.

Advanced corneal surface ablation efficacy in myopia: changes in higher order aberrations

OBJECTIVE To evaluate the change of ocular and corneal higher order aberrations (HOAs) after wavefront-guided advanced surface ablation (WF-ASA) for myopia using 4 different epithelial management techniques (AA-PRK, LASEK, Epi-PRK, and Epi-LASIK). DESIGN Retrospective single centre excimer database analysis. PARTICIPANTS Two hundred and forty eyes equally divided between the 4 WF-ASA techniques, matched for mean and range of required spherical correction. METHODS Ocular wavefront aberrations were measured using the wavescan aberrometer and corneal aberrations were obtained from corneal topography elevation maps and calculated by ray-tracing. All data were collected preoperatively and 3 months following treatment. The aberrations were described as Zernike polynomials, and analysis focused on total HOAs and spherical aberration (SA). RESULTS Three months postoperatively, there was a statistically significant surgically induced increase in total HOAs and SA both for ocular and corneal analysis (p < 0.001). There was no statistically significant difference in the induced ocular SA and HOAs between the groups, but the differences in induced corneal SA and HOAs were significant (p < 0.010). Ocular changes in SA were weakly correlated to preoperative SA (20.30, p < 0.001) but strongly correlated to applied spherical correction (20.68, p < 0.001). Surgically induced corneal SA was weakly correlated to preoperative corneal SA (20.34, p < 0.001) and applied spherical correction (20.46, p < 0.001). CONCLUSIONS Three months postoperatively, all procedures resulted in an increase in ocular and cornealHOAs and SA. Induced aberrations were most strongly correlated to the applied spherical power correction. Modifying the existing ablation pattern to compensate for induced HOAs might improve the outcome.

Long-term visual and refractive outcomes following surface ablation techniques in a large population for myopia correction.

PURPOSE To evaluate the visual and refractive outcome for four wavefront-guided surface ablation (WGSA) techniques (LASEK, LASEK flap-off [LASEK FO], Epi-LASIK, and Epi-LASIK flap-off [Epi-LASIK FO]) in a large myopic population. METHODS This retrospective review included 1000 myopic eyes (spherical equivalent [SE] -1.0 to -8.0 diopters [D]) treated with WGSA (VISX STAR S4 with IR) using four different epithelial management techniques. Flaps were either retained (163 Epi-LASIK, 361 LASEK) or discarded (277 Epi-LASIK FO, 199 LASEK FO). Eyes in each group were stratified to either low, mild, moderate, or high myopia based on preoperative SE. Uncorrected distance visual acuity (UDVA), corrected distance visual acuity (CDVA), manifest refraction spherical equivalent (MRSE), predictability, lines lost, and haze were compared at 3, 6, and 12 months. RESULTS At 1 year, UDVA and CDVA of ≥20/20 and 20/15 were comparable across the four procedure groups and within each subgroup of myopia. Predictability was less than or equal to ±0.5 D of intended correction in 96% to 99% of eyes. LASEK FO and Epi-LASIK FO outperformed the EPI-LASIK in achieved MRSE, especially in the high myopia category (-0.012, 0.040, and -0.27 D, respectively, P < 0.05). No eyes lost more than one line of CDVA; and 50% to 60% of eyes in each group gained one or more lines. No significant haze was recorded in any group. There was no statistically significant difference between groups in the preoperative MRSE and efficacy indices except for LASEK FO. CONCLUSIONS At 1 year, there was no statistically significant difference in visual outcomes between techniques for any degree of myopia. However, the MRSE achieved with LASEK FO and Epi-LASIK FO were closer to emmetropia.

Vehicle occupant restraint systems impact on eye injuries: A review

Vehicle occupant trauma to the eyes and associated facial structures has evolved rapidly in conjunction with safety-oriented vehicle design, including restraint systems. Trends vary worldwide with culture, personal factors, vehicle safety equipment, and the traffic environment-including physical, legislative, and enforcement. Wearing safety belts is essential to occupant protection. Airbags were designed as a supplement to protect the head from hard surfaces in frontal crashes, not as a primary countermeasure. Even where vehicle fleets are new with high airbag prevalence, but safety culture and knowledge of restraints is less than robust, injury attributable to not wearing seatbelts is frequent, especially in countries where high-powered vehicles are prevalent. Upper bodies of rapidly forward-moving unrestrained occupants collide with rearward-accelerating airbags. Airbag deployment produces injuries such as corneal abrasions, alkali burns, and the effects of globe compression.

Ethics teaching in a medical education environment: preferences for diversity of learning and assessment methods

ABSTRACT Background: Ethics and professionalism are an integral part of medical school curricula; however, medical students’ views on these topics have not been assessed in many countries. Objective: The study aimed to examine medical students’ perceptions toward ethics and professionalism teaching, and its learning and assessment methods. Design: A self-administered questionnaire eliciting views on professionalism and ethics education was distributed to a total of 128 final-year medical students. Results: A total of 108 students completed the survey, with an 84% response rate. Medical students reported frequently encountering ethical conflicts during training but stated only a moderate level of ethics training at medical school (mean = 5.14 ± 1.8). They noted that their education had helped somewhat to deal with ethical conflicts (mean = 5.39 ± 2.0). Students strongly affirmed the importance of ethics education (mean = 7.63 ± 1.03) and endorsed the value of positive role models (mean = 7.45 ± 1.5) as the preferred learning method. The cohort voiced interest in direct faculty supervision as an approach to assessment of knowledge and skills (mean = 7.62 ± 1.26). Female students perceived greater need for more ethics education compared to males (p = < 0.05). Students who claimed that they had experienced some unprofessional treatment had a more limited view of the importance of ethics as a subject (P = 0.001). Conclusion: Medical students viewed ethics education positively and preferred clinically attuned methods for learning.

Informed consent learning: Needs and preferences in medical clerkship environments

Purpose Limited information exists regarding students’ routine educational needs in support of ethics and professionalism practices faced in real clinical practice. As such the authors aimed to explore medical students learning needs and preferences for informed consent and relevant ethical issues in the clerkship environments. Materials and methods A cross-sectional study using a self-administered, printed survey distributed to final year clinical clerks. Results 84% completed the survey. Students indicated the need for more attention to all topics related to informed consent (mean = 7.1 on a scale of 0 to 9; ±1.2). Most additional instructional attention was requested for topics raised in discussions with patients concerning the risks, benefits and alternatives to recommended treatments (7.3 ±1.4). The cohort expressed the need for education in the care of vulnerable patients (7.2 ±1.2) with a maximum score for the care of abused children. Women perceived greater need for education concerning informed consent than male respondents (p>0.05). There were significant differences between students who scored high or low on the item “being treated in professional manner” and “endorsement of educational needs for care of adolescents” (p = 0.05). Conclusion There was heightened perception among final year medical students of the need for greater attention to be paid to informed consent education.

Guidelines on a Code of Ethics and Professionalism for Residents Undertaking Postgraduate Medical Education

The concept of structured Postgraduate Medical Education (PGME) and residency training gained widespread support from Emirati regional health authorities and has become a national priority in the United Arab Emirates (UAE). In cosmopolitan countries, such as the UAE, residents/ trainees are tutored and supervised by trainers from diverse cultural, ethnic and religious backgrounds. The roles and responsibilities of trainees are defined, thereby ensuring the appropriateness and safety ofpatient care countrywide in situations where trainees are involved. The aim of this project was to develop guidelines for a Code of Ethics that would govern the conduct and activities of postgraduate trainees in various medical specialties countrywide. Elements of Residency training involving ethics and professionalism highlighted by various international organizations with recognized high ethical standards and the opinions scholars who have published in this field were reviewed and adapted, with preservation of core Islamic values. This document focuses on professional responsibilities in several domains: professional practice standards, professional community standards, research standards, professional relationships with colleagues, physician duties towards society, physician duties towards workplace establishment, the relationships between trainees and industry, reporting responsibilities, and lists of some behaviors that are considered unacceptable. A formal document is now available to all postgraduate trainees (Residents) to emphasize the importance and relevance of ethical considerations and professionalism in PGME with a strong sense of obligation to patients’ best interests.

Transient cerebral cortex anaesthesia following peribulbar block.

A 68-year-old male with known type II diabetes mellitus treated with dietary control had undergone a previous, uneventful, peribulbar block for cataract extraction in the right eye. Before the current block, the patient’s blood pressure was 160/70 mm Hg, sinus rate 80/min, and respiratory rate 16/min. The ophthalmologist performed the peribulbar block with a 4 mL mixture of equal amounts of 2% lignocaine and 0.375% bupivacaine, in addition to hyaluronidase, injected through a 23-gauge, 25 mm needle. The needle was inserted into the temporal third of the lower lid along the orbital wall to a depth of 2.5 cm. Possible intravascular injection was excluded by aspiration. A Honan balloon was placed on the eye for 10 min. At the stage of capsulorhexis, which was approximately 20 min after performance of the peribulbar block, the patient was noticed to be uncooperative and unresponsive to commands but withdrew his limbs to pain; this may have been present much earlier but unnoticed, as vital signs remained unchanged from the initial findings. The operation was completed under general anaesthesia, and the patient was discharged home the next day without any sequelae. Peribulbar anaesthesia has increased in popularity because it offers the same anaesthetic benefit as retrobulbar injection with fewer complications.1,2 Despite this, the risk of morbidity attributable to peribulbar anaesthesia is not abolished. Complications may occur as a consequence of direct injury from the needle, inadvertent intra-arterial injection, and (or) direct access of anaesthetic agent to the subarachnoid space.3 It is widely accepted that inadvertent injection of local anaesthetic into the subarachnoid space through the optic sheath is the most likely cause of brainstem anaesthesia. In the present case, in which a short needle was used and the globe was in a primary gaze position during anaesthetic infusion, this is unlikely. However, intraconal anaesthesia spread along the optic nerve may explain this occurrence. Peribulbar blocks use the tissue compartment principle,4 in which the injected fluid is spread by virtue of pressure and volume to the surrounding compartment tissue. The possibility exists that injection of the local anaesthetic with hyaluronidase followed by Honan balloon application may have increased intraorbital pressure, amplifying the diffusion of the anaesthetic drug through the fine regional vasculature to the central circulation. An intra-arterial injection with retrograde flow of anaesthetic agents into the carotid circulation might have been the mechanism of the complication in our patient. It is well known that lignocaine, in sufficient dosage, can produce nerve blockade, respiratory collapse, and seizure activity. Because the needle used for ocular block is usually of small gauge, it might not always be possible to detect blood, and several seconds may elapse before blood or cerebrospinal fluid is visible in the hub, making it difficult to detect intravascular or subarachnoid injection.4,5 The findings of delayed onset of unconsciousness and stable vital signs are entirely consistent with exposure of the cerebral cortex to a minimal amount of anaesthetic agent. Thus, if a direct intravascular injection was made, it could account for the constellation of symptoms. If the volume injected had been greater, the possibility of other signs of brainstem anaesthesia might have been manifest.