James McKelvie

The influence of tilt, decentration, and pupil size on the higher-order aberration profile of aspheric intraocular lenses.

PURPOSE To characterize the influence of tilt angle, decentration, and pupil size on the higher-order aberration (HOA) profile of 3 aspheric intraocular lenses (IOLs) using a physical model eye. DESIGN A 4-factor (model, pupil, angle, decentration) in vitro experimental design comparing 3 aspheric IOLs using a physical model eye. METHODS Measurements of HOA were obtained using the Zywave aberrometer (Bausch & Lomb, Rochester, NY) and a purpose-built physical model eye. The following IOLs were assessed with various levels and combinations of pupil diameter, decentration, and tilt angle: the AcrySof IQ SN60WF aspheric (Alcon, Hünenberg, Switzerland), Technis ZA9003 aspheric (Advanced Medical Optics, Santa Ana, CA), and Adapt Advanced Optics (Bausch & Lomb). Fifteen Zernike modes were compared using multivariate analysis of variance, canonical discrimination, and regression analysis. Four identical IOLs of each IOL model were assessed at all possible combinations of 3 pupil sizes, 4 levels of decentration, and 4 tilt angles. MAIN OUTCOME MEASURES Individual HOA from z200 to z550. RESULTS Pupil size, decentration, model, and tilt angle all had statically significant effects on the HOA profile. Pupil size contributed most to observed total variability (54.9%), followed by decentration (22.7%), then model (16.6%), and finally tilt angle (5.7%). All factors demonstrated significant interaction terms with respect to HOA. Intraocular lenses with increased aspheric properties inherent in the design of the optic were more sensitive to decentration and change in pupil size. CONCLUSIONS The 3 IOL models demonstrated significant differences in HOAs in response to changes in pupil size, decentration, and tilt angle. All IOL models assessed in this study demonstrated minimal HOA at small pupil diameters. The IOL models with lower, or an absence of, negative spherical aberration were most robust to displacement with increased decentration and tilt angle.

Keratocyte progenitor cell transplantation: A novel therapeutic strategy for corneal disease☆

Keratocytes are specialised cells that produce and maintain corneal stromal matrix and play a key role in corneal wound healing. Abnormal functioning of these cells is likely to play a central role in corneal disorders, such as keratoconus, which in many cases leads to corneal blindness if untreated. The genetic basis of keratoconus is poorly understood but it is likely that apoptosis pathways are involved. The current paper proposes a novel hypothesis for the treatment and prevention of corneal blindness in disorders such as keratoconus as an alternative to the gold standard treatment of penetrating or partial thickness keratoplasty. The proposed hypothesis involves the isolation, purification and transplantation of keratocyte progenitor cells (KPC), with introduction into stroma via femtosecond laser channels in diseased corneal stroma using a carrier medium. The success of this approach will depend upon the viability, migration, and cell division of introduced KPC and production of normal stromal matrix. Results from previous studies suggest that cellular transplantation is possible and may lead to healthy stromal matrix production and remission of a disease phenotype in patients affected with disorders such as keratoconus. If the current hypothesis proves to be correct, it may offer an alternative to invasive keratoplasty for treatment of corneal disorders such as keratoconus that cause significant morbidity for millions of people worldwide.

Relationship between second‐generation frequency doubling technology and standard automated perimetry in patients with glaucoma

Purpose:  The aim of the study was to establish the correlation between visual filed loss as shown by second‐generation Frequency Doubling Technology (Humphrey Matrix) and Standard Automated Perimetry (Humphrey Field Analyser) in patients with glaucoma. Also, compared were the test duration and reliability.

The clinician scientist –quo vadis?

The future and relevance of the clinician scientist continues to be debated in this and other medical journals, although the need for more clinician scientists has been well recognized by the National Institutes of Health (NIH) as a primary objective. The contributions of the clinician scientist may be considered as three separate roles: academic clinician, clinical academician and physician scientist. Interestingly, one survey outlined the clinical academician as the most difficult individual to recruit and retain on faculty, the most difficult for whom to find salary support and the most difficult individual to get through the promotions process. Clinician scientists play important roles in bridging the gap between laboratory science and the clinic and are thus identified as key players in translating research into therapies, as future academic teachers and mentors, as well as making important contributions in the clinical arena. Despite such acknowledged benefits in the context of the current deficit in the number of clinician scientists, there is little corresponding effort to identify, recruit and fund clinician scientists for the future. Although many ophthalmologists believe that research benefits education, clinical practice and career, and a high proportion believe research should be part of vocational training, the reasons for pursuing research are not always straightforward. Indeed, motivations for clinicians to conduct research may in some situations be largely for personal career advancement rather than for direct patient benefit. Following a career as a clinician scientist is not an obvious choice for many, and therefore the role of mentors is likely to play a critical role in the decision to enter this career path. Paradoxically, despite the common perception, clinicians conducting research may not necessarily lead to accelerated promotion or enhanced career development. Furthermore, the time required to complete a PhD may be an important barrier for clinicians. Indeed, of approximately 17 000 medical students who graduate each year in the USA only 500 (3%) graduate with combined MD/PhD. Unfortunately, having embarked on such a career path it may also be difficult to fit the clinician scientist into current university structures. To improve this situation, in the UK a clinician scientist scheme has been introduced whereby at the end of a fellowship it is expected the individual will normally be appointed to a senior academic post; however, not all medical schools have accepted this proposal. The duration of training and attendant large medical school loans may also detract from the possibility of a career as a clinician scientist especially with the additional science training/higher degree required and the possibility of subsequent, relatively poorly paid, university positions. To deal with some of the issues, in an enlightened, progressive policy that is jointly funded by a combination of Department of Health, research councils and medical research charities, the UK has created a national funding scheme to support clinician scientist fellowships – notably, this is at a cost of up to half a million pounds per individual. It may be difficult to devote adequate time to research projects while undertaking a busy clinical training; however, it is widely accepted that research and clinical education are complimentary in developing the clinician– scientist role. Interestingly, although a large cohort of US surgeons graduate with significant research experience (that has extended their training for 1–3 years), they have lower rates of (NIH) grant applications and success. Perhaps this reflects time constraints and the often more complicated/prolonged nature of completing clinical research not uncommonly slowed by regulations, recruitment of patients, clinical workload and other related factors. Thus, with limited research budgets clinician scientists can find it very difficult to survive and balance workloads in this role, and many are therefore forced either to assume greater clinical responsibilities to the detriment of research, or forgo clinical duties in order to more effectively compete for research funding and focus on research productivity. Perhaps surprisingly, environmental factors may be more important than personal characteristics in terms of research productivity. Indeed, leadership and mentorship by those with appropriate research expertise and skill have a greater effect on research productivity than characteristics of personal motivation, research training and uninterrupted time. This implies that to encourage and develop clinician scientists we also need to grow dedicated and supportive leadership. As previously noted, to be an effective clinician scientist a higher research degree is almost a prerequisite and known to be positively correlated with number/rate of publications. Nonetheless, although there is increasing pressure to publish primarily in journals with a high Journal Impact Factor (JIF), clinical journals generally do not have such high JIF rankings as many of the laboratory science journals. It therefore remains difficult for clinician scientists to compete with basic science researchers in terms of publication in high JIF journals. Basic science fields tend to produce higher JIF and citation indices, and whereas clinical medicine is more inclined to cite basic science articles the opposite is not true. This is a potential disincentive for physicians seriously committed to research to work as clinician scientists rather than devote themselves entirely to more laboratory-based science research. Clinical and Experimental Ophthalmology 2009; 37: 247–248 doi: 10.1111/j.1442-9071.2009.02040.x

Applying risk analysis to predict posterior capsule rupture during cataract surgery in New Zealand

protruding out of the tube to facilitate removal at a later stage. The Healon GV was partially removed, and a bolus injection of intracameral cefazolin (1mg in 0.1ml solution) was given. The paracenteses were hydrated, and the eye was padded at the end of the surgery. On review, there was a resolution of hypotony and choroidal effusion. The second patient had a rise in intraocular pressure 4days after the stenting, which settled with medical management. The end result in bothpatientswas stable intraocular pressurewith deep anterior chambers; stent removal was not required. In conclusion, stenting of the glaucoma drainage devices tube using Supramid suture appears to be an effective option in the treatment of late hypotony that can occur with these glaucoma drainage devices. It would be particularly useful in patients with reduced aqueous production. In the event of increased intraocular pressure, removal of the stent would be simple and could be carried out under topical anaesthesia. This simple stenting procedure of managing hypotony is more advantageous than the existing alternative management of exposing the drainage plate and tying the tube externally, which requires more manipulation. Further observational studies on a larger number of patients would aid in determining the safety and efficacy of this procedure.

The rising tide of Acanthamoeba keratitis in Auckland, New Zealand: a 7-year review of presentation, diagnosis and outcomes (2009-2016): Acanthamoeba keratitis: a 7-year review

Acanthamoeba is an increasingly prevalent cause of vision‐threatening microbial keratitis.

The Sheep Cornea: Structural and Clinical Characteristics

ABSTRACT Purpose: The aim of this study was to perform qualitative and quantitative analyses to characterize the corneas of young, healthy sheep. Materials and methods: Eight healthy male sheep, 10 months to 1 year of age, were included as experimental subjects. Central corneal thickness was measured using a handheld pachymeter, and an Easygraph corneal topographer provided topographic maps. Microstructural imaging of corneal layers was achieved by using the Heidelberg Retina Tomograph III Rostock Corneal Module in vivo corneal microscope (IVCM). An Ocular Response Analyzer (ORA) provided quantitative measurements of intraocular pressure (IOP), corneal hysteresis (CH), and corneal resistance factor. Tissue histology and immunohistochemistry were carried out to obtain detail on the corneal layers. Results: Light microscopy and immunohistochemical labeling revealed a stratified epithelium, a limbus with numerous limbal crypts, a thick basement membrane, a thin Bowman’s layer, a thick corneal stroma with a dense population of keratocytes, and a thick, hyper-reflective Descemet’s membrane. Using IVCM, the cell density of the basal layer was noted to be significantly higher than that of other epithelial cell types. The density of keratocytes was significantly higher (P value = 0.0223) in the anterior compared to the posterior stroma. The endothelial cells were organized in a characteristic honeycomb pattern. The mean and standard deviation values for central corneal pachymetry were 623.14 ± 19.5 μm and 616.37 ± 34.87 μm for the left and right eyes, respectively. ORA-derived mean values for IOPcc and CH for the left and right eyes were 14.93 ± 1.73 mm Hg and 15.16 ± 2.02 mm Hg and 3.56 ± 0.72 mm Hg and 3.73 ± 0.49 mm Hg, respectively. Conclusions: The anatomical and clinical characteristics of the sheep cornea, as outlined in this study, make the sheep a suitable and relevant model for corneal research. This study provides researchers with important data on the suitability of sheep as a model for ophthalmic experiments.

An in-vivo comparison of two tear osmometers

Dry eye disease (DED) is defined by the Dry Eye Workshop (DEWS) as “a multifactorial disease of the ocular surface characterized by a loss of homeostasis of the tear film, and accompanied by ocular symptoms, in which tear film instability and hyperosmolarity, ocular surface inflammation and damage, and neurosensory abnormalities play etiological roles.” Given the central importance of hyperosmolarity in the pathophysiology DED, there is significant interest in clinical measurement of tear osmolarity as part of the diagnosis and ongoing management of DED. There are several methods available to measure tear osmolarity. Historically freezing point depression osmometers and vapour pressure osmometers have been used to measure tear osmolarity. These osmometers involve quite a complex process of tear osmolarity determination better suited to a research, rather than a clinical, setting. Both instruments require collection of tears using micropipettes and a significant degree of expertise is required to obtain accurate measurements. More recently, other osmometers have been developed which are more suitable to a clinical environment. Two of these are the TearLab (TearLab Corporation, San Diego, California) and the i-Pen (i-Med Pharma, Dollard-des-Ormeaux, Quebec, Canada). Both the TearLab and the i-Pen, measure electrical impedence to determine osmolarity. The TearLab uses a disposable test card attached to a collection pen is used to obtain a sample of tears from the inferotemporal tear meniscus. Less than 20 nL of fluid is required for osmolarity testing. The i-Pepm (I-Med Pharma) employs disposable strips which measure tear osmolarity when touched against the tarsal conjunctiva of the lower lid. The purpose of the current study was to assess the agreement between two tear osmolarity measuring devices, the iPEN and the TearLab. Ethics approval was obtained from the hospital ethics committee. Consent was obtained from all participants. All procedures were followed in accordance with the Helsinki Declaration of 1964, as revised in 2013. Fifty-seven eyes of 31 consecutive patients attending the Corneoplastic Unit at Queen Victoria Hospital, East Grinstead, UK had tear osmolarity tested with both devices at the same time during the same visit. Patients had been referred for a variety of corneal or oculoplastic disease, not specifically dry eye disease. Patients without a prior diagnosis of DED were chosen as these devices have been developed as diagnostic tools for DED. Calibration was performed for the TearLab daily and was not required for the i-PEN as per the manufacturer instructions.

Cicatricial ectropion surgery: a prospective study of long-term symptom control, patient satisfaction and anatomical success: Cicatricial ectropion: long-term outcomes

Cicatricial ectropion repair is effective and has a low complication rate.

Eyelid reconstruction using the “Hughes” tarsoconjunctival advancement flap: Long-term outcomes in 122 consecutive cases over a 13-year period

ABSTRACT This article evaluates the complications and long term functional and cosmetic outcomes of tarsoconjunctival advancement flaps for repairing a range of lower eyelid defects in a large cohort of consecutive cases. A retrospective series of 122 consecutive cases of eyelid reconstruction using tarsoconjunctival-advancement flaps was conducted at Waikato Hospital, or Hamilton Eye Clinic, New Zealand. All cases of lid reconstruction using tarsoconjunctival-advancement flaps between January 1, 2001 until April 3, 2014 were included for analysis. All patients provided written consent for surgery and the study complied with New Zealand Health and Disability Ethics Committee guidelines and the Declaration of Helsinki. Data were collected on patient demographics, lesion histology, defect size, adjuvant surgical procedures required for reconstruction, surgical and postoperative complications, cosmesis and patient satisfaction. Patients requiring lower eyelid reconstruction were predominantly male (56%) and basal cell carcinoma was the most common pathology (>80%). Male gender was associated with larger tarsoconjunctival-advancement-flap width (P-value = 0.0432), larger maximum flap width (20 vs 15 mm), and required on average more adjuvant procedures for reconstruction (1.80 vs 1.48, P-value = 0.02). Mean duration to flap division was 37 days and decreased over the duration of the study. Complicated cases were associated with shorter duration to flap division. Mean follow-up was 7 months, complications were observed in 14% with revision required in 4%. Tarsoconjunctival flap reconstruction of the lower lid is suitable for a range of defect sizes and produces excellent functional and cosmetic outcomes. Complications are relatively infrequent and may be associated in some cases with decreased duration to flap division.