Philip J Polkinghorne

Northern New Zealand Rhegmatogenous Retinal Detachment Study: epidemiology and risk factors.

Background: The incidence of retinal detachment in New Zealand is not currently documented in the literature. This study sought to determine the annual incidence of rhegmatogenous retinal detachment (RRD) and associated risk factors in northern New Zealand.

Detection of the Carrier State of X-Linked Retinoschisis

We determined the extent of suppressive rod-cone interaction in 11 obligate carriers and eight potential carriers of X-linked retinoschisis from eight families. Despite otherwise normal ophthalmoscopic and functional testing, all of the obligate heterozygous carriers demonstrated a complete absence of normal rod-cone interaction. Of the potential heterozygous carriers, three had normal rod-cone interactions, two had no detectable interaction, and two yielded technically unsatisfactory results. This lack of rod-cone interactions allows heterozygous individuals to be identified clinically and has implications concerning the origin of this inherited disorder.

Endophthalmitis after pars plana vitrectomy: a New Zealand experience.

Purpose: To describe the clinical course and estimate the incidence of endophthalmitis after pars plana vitrectomy in New Zealand. Methods: A retrospective analysis was performed on all cases of culture-positive endophthalmitis after vitreoretinal surgery over a 10-year period. Results: Five cases of culture-positive endophthalmitis were identified between 1993 and 2002. During this interval, 10,397 vitrectomies were performed, equating to an overall incidence of 0.048%. All patients presented within 7 days of surgery. Conclusions: Endophthalmitis after pars plana vitrectomy is uncommon but is associated with a poor functional outcome.

Functional and anatomical remodeling in human retinal detachment.

Rhegmatogenous retinal detachment is by far the most common indication for retinal surgery and a major cause of severe vision loss. Increased levels of glutamate found in the vitreous of human patients and persistent remodeling, even after reattachment, suggest substantial neurochemical, functional and anatomical changes have occurred in the detached retina. Therefore, this study was designed to characterize the morphological changes and glutamate receptor functionality in human rhegmatogenous retinal detachment. A cation channel permeating probe, agmatine (1-amino-4-guanidobutane; AGB), was employed to track endogenous and kainate (KA) driven channel functionality combined with immunocytochemical characterization of cellular remodeling. In the detached retina increased AGB permeability was identified in the outer retina while there was a decrease in the inner retina in basal conditions. KA receptors exhibited increased AGB permeability in ON bipolar cells and decreased permeability in calbindin labeled inner retinal cells. All retinal detachment samples demonstrated ectopic synaptic protein expression, photoreceptor processes extending toward the inner retina, and other remodeling features of retinal degeneration. These anatomical changes have been demonstrated in animal studies and are novel features unreported in primary cases of human retinal detachment. We conclude that deafferentation in retinal detachment leads to alteration of the glutamatergic pathway.

Infectious endophthalmitis: clinical features, management and visual outcomes

Aim:  To identify the clinical features and outcomes of infectious endophthalmitis in New Zealand.

Functional activation of glutamate ionotropic receptors in the human peripheral retina

Glutamate is the major neurotransmitter in the vertebrate retina. Neurons involved in the glutamate pathway express α-amino-3-hydroxyl-5-methylisoxazole-4-propionic acid (AMPA), kainic acid (KA) and N-methyl-D-aspartate (NMDA) receptors. Functional characterization of these ionotropic glutamate receptors can be achieved by using a cation channel permeating probe named agmatine (1-amino-4-guanidobutane; AGB). Retinal mapping using this guanidinium analog has certain advantages including the immunocytochemical identification of a whole population of neurons expressing functional glutamate gated receptor channels. We have extended AGB studies into the functionality of ionotropic receptors in peripheral aged human retina to serve as a comparison for functional analysis of retinopathies such as retinal detachment. We probed the human retina with AGB after activation with AMPA, KA and NMDA. The results showed patterns of AGB entry into neurons consistent with those previously observed in subunit localization studies in adult mammalian retinae including primates. Application of 30 μM AMPA activated receptors in virtually all calretinin immunoreactive AII amacrine cells in the mid-peripheral human retina. About half of the AII amacrine cells showed AGB permeation after incubation with 50 μM KA. Some bipolar cells including DB3 OFF bipolar cells displayed functional KA receptors. Colocalization of AGB with parvalbumin labeled horizontal cells revealed functional KA and AMPA receptors with no responsiveness to NMDA activation. NMDA activation resulted in AGB labeling of ganglion cells and amacrine cells. The present study provides a description of functional ionotropic glutamate receptors in the aged mid-peripheral human retina.

Amino acid immunoreactivity in normal human retina and after brachytherapy.

We localised amino acids in the mid‐peripheral aged human retina and a retina that had undergone radiation treatment 10 years earlier. The distribution pattern of glutamate, γ‐amino butyric acid (GABA), glycine, glutamine and taurine, reflected patterns established in the primate retina. The retina that had undergone radiation exposure displayed both anatomical and neurochemical remodelling. The proximal retina comprised around 40 to 45 per cent of the total retina and neuronal kinesis and aberrant neuronal projections were also present. Amino acid neurochemistry was strikingly different with Müller cells displaying GABA loading, glycinergic neurons displaced and displaying a very high level of glycine labelling. We conclude that radiation exposure triggered these changes in the human retina and likely reflects general remodelling of structure and function following ischaemic damage to endothelial cells.

Auckland Proliferative Diabetic Vitrectomy Fellow Eye Study

Background: To review medical and ophthalmic findings of primary diabetic vitrectomy patients to examine indices important in progression to fellow eye surgery.

Vitreoretinal fellow surgical outcome of small gauge pars plana vitrectomy for acute rhegmatogenous retinal detachment

BackgroundOur purpose was to determine the anatomical outcome following small gauge vitrectomy for acute rhegmatogenous retinal detachment (RRD) operated by vitreoretinal fellows.MethodsWe undertook a retrospective review of adult patients presenting with an acute RRD treated with small gauge vitrectomy where the operating surgeon was either a vitreoretinal fellow or consultant surgeon. The patient’s demographics were recorded as well as relevant clinical findings. The end point was determined to be the anatomical outcome and number of surgeries.ResultsTwo hundred and twelve eyes were included in this study. The age range was 21–90 years, with approximately one third of the patients being female. The macula was attached in 53% at presentation, and 65% of the eyes were phakic. Primary re-attachment with a single operation was achieved in 75% of cases, and final re-attachment rate was 92%. Mean presenting visual acuity was LogMAR 1.07 (SD 1.09) and final visual acuity was LogMAR 0.63 (SD 0.85). We found no association between final anatomical success and experience of the surgeon (p = 0.6).ConclusionWe found that acute RRD treated by vitreoretinal fellows using small gauge vitrectomy did not place the patient at any discernable disadvantage.

Cataract surgery practices and endophthalmitis prophylaxis by New Zealand Ophthalmologists.

Some countries have reported increased use of intracameral antibiotics since the publication of the preliminary results of the European Society of Cataract and Refractive Surgeons (ESCRS) Endophthalmitis Study in 2006, which showed an approximately fivefold decrease in the rates of endophthalmitis with intracameral cefuroxime. In New Zealand, the reported rate of intracameral antibiotic use at the time of cataract surgery increased from 3.9% of surveyed ophthalmologists in 2003 to 24% in 2007. However, there have not been any recent reports describing the current practice patterns and strategies of endophthalmitis prophylaxis in New Zealand. We surveyed New Zealand ophthalmologists to determine the contemporary cataract surgery practices and methods of endophthalmitis prophylaxis. This study was approved by the Royal Australia and New Zealand College of Ophthalmology ethics committee. In November 2015, three separate email requests with a link to an online survey were sent to 115 Fellows of the Royal Australia and New Zealand College of Ophthalmology New Zealand branch. The survey was anonymous, and only consultant members were invited to respond regarding their practices during the period of 1 November 2014 through 31 October 2015. The questionnaire allowed respondents to report their practices as percentages (i.e. 30% subTenon’s, 70% topical anaesthesia) in case their practice pattern varied according to location. A total of 71 (61.7%) of the 115 invited ophthalmologists completed the survey. The responding ophthalmologists had been practising for a median of 15 years (range, 1–34years). All respondents reported performing cataract surgery, with an overall practice setting of 40% public and 60% private. The total self-reported number of cataract operations was 24089. The number of cataract operations performed and/or supervised in the preceding year was <100 cases for 4.2%, 100–299 for 38.0%, 300 to 499 cases for 36.6% and ≥500 cases for 18.3% of surgeons. Two surgeons did not provide the number of cataract surgeries performed in the preceding year. A total of nine cases of post-cataract endophthalmitis (both sterile and culture-proven) were reported equating to a self-reported endophthalmitis rate of 0.037%. The cataract surgery practice patterns and methods of chemoprophylaxis are found in Tables 1 and 2, respectively. Topical preoperative povidone-iodine antisepsis was used almost universally with chlorhexidine reported by some surgeons in cases of allergy to iodine. Injection of intracameral antibiotics occurred in 42.6% of the practices (used by 48% of respondents), with cefuroxime used most frequently, followed by cefazolin. The use of intracameral antibiotics was similar among the more experienced surgeons (over 15years as specialist, 44%) and less experienced surgeons (15years or less as specialist, 51%) (P=0.63). Of those respondents who used intracameral antibiotics and worked in both public and private practice settings (n=30), 80% used them in both settings and 20% used them in the private surgical setting only. Of the respondents who did not use intracameral antibiotics (n=37), the listed reasons were: lack of available pre-formulated preparation (cited by 65%), concerns about mixing/compounding risks (62%), not convinced of need or benefit based on available evidence (43%), risk of endothelial toxicity (30%), cost (30%) and institutional regulations (24%). Preoperative topical antibiotic prophylaxis was used in 14.5% of the practices, with approximately half (7.5% overall) being started prior to the day of surgery (mean 3.1days, range 1–7days preoperatively). Postoperative topical antibiotic was the norm in 94.6% of the practices. The duration of use was <7days for 7.9%, 7–13days for 67.9%, 14–20days for 13.3%, 21–27days for 6.3% and ≥28days for 4.7% of respondents. No surgeons reported routine administration of oral or intravenous antibiotics for surgery complicated by vitreous loss. In comparison to previous surveys, the use of intracameral antibiotics in New Zealand (48% of respondents in 2015) has increased over 10-fold since 2003 (3.9%) and doubled since 2007 (24%). In Australia, there has also been a marked increase in intracameral antibiotic use in recent times increasing from 5% of surgeons in 2003 to 78% in 2012. Of New Zealand ophthalmologists not using intracameral antibiotics, over half had concerns about risks of non-commercially prepared antibiotic preparations and nearly half had concerns about the necessity or effectiveness of intracameral prophylaxis. These concerns are similar to those elicited by a 2008 survey in the United Kingdom and a 2014 survey of the American Society of Cataract and Refractive Surgery members.