Does This Patient With Acute Infectious Conjunctivitis Have a Bacterial Infection?: The Rational Clinical Examination Systematic Review.

Importance: Acute infectious conjunctivitis is characterized by ocular redness and discharge, and is a common clinical entity. Evidence-based tools to aid the clinical diagnosis of viral vs bacterial conjunctivitis are lacking and may contribute to overprescribing of topical antibiotics. Objective: To determine the relative prevalence of viral vs bacterial conjunctivitis in adults and children, and to determine which symptoms or signs are suggestive of a viral vs bacterial etiology. Data Sources: A MEDLINE search (January 1946-March 2022) yielded 1891 articles. Included articles were rated using a quality score based on a modified Rational Clinical Examination grading system. Methodological quality levels 1 through 4 required a microbiological reference standard for diagnosis, whereas quality level 5 (the lowest quality) used a clinical reference standard for diagnosis. Study Selection: Consecutive series of patients presenting with acute infectious conjunctivitis and case series of viral or bacterial conjunctivitis alone. Thirty-two studies were included in a meta-analysis to determine prevalence and diagnostic accuracy measures; 27 used a microbiological reference standard for diagnosis and 5 used a clinical reference standard for diagnosis. Results: In studies involving children (5 studies; 881 patients; mean age, 4.7 years [age range, 1 month-18 years]), the prevalence of bacterial conjunctivitis was higher than viral conjunctivitis (71% vs 16%, respectively, P = .01). In the only study of adults (n = 207 patients; mean age, 25.7 years), the prevalence of viral conjunctivitis was higher than bacterial conjunctivitis (78% vs 16%, respectively, P < .001). For the primary analysis of level 1 (n = 6) and level 2 (n = 5) studies (1725 patients total), the clinical findings that best distinguished a viral etiology for conjunctivitis from a bacterial etiology included pharyngitis (sensitivity range, 0.55-0.58; specificity range, 0.89-0.94; positive likelihood ratio [LR] range, 5.4-9.9), preauricular lymphadenopathy (sensitivity range, 0.17-0.31; specificity range, 0.93-0.94; positive LR range, 2.5-5.6), and contact with another person with red eye (sensitivity, 0.18 [95% CI, 0.14-0.22]; specificity, 0.93 [95% CI, 0.90-0.95]; positive LR, 2.5 [95% CI, 1.6-3.7]). Mucopurulent ocular discharge (sensitivity, 0.76 [95% CI, 0.60-0.87); specificity, 0.66 [95% CI, 0.58-0.73]; positive LR, 2.1 [95% CI, 1.7-2.6]) and otitis media (sensitivity, 0.24 [95% CI, 0.20-0.29]; specificity, 0.91 [95% CI, 0.85-0.94]; positive LR, 2.5 [95% CI, 1.5-4.4]) were associated with the presence of bacterial conjunctivitis. Conclusions and Relevance: In this review, bacterial conjunctivitis was more common than viral conjunctivitis in children and viral conjunctivitis was more common than bacterial conjunctivitis in adults, although the prevalence estimates were based on limited evidence. Symptoms and signs associated with a higher likelihood of viral conjunctivitis in adults and children included concomitant pharyngitis, an enlarged preauricular node, and contact with another person with red eye, and signs associated with a higher likelihood of bacterial conjunctivitis included the presence of mucopurulent discharge and otitis media, but no single symptom or sign differentiated the 2 conditions with high certainty.

Efficacy of Intravenous Mannitol in the Management of Orbital Compartment Syndrome: A Nonhuman Primate Model.

PURPOSE: To report the efficacy of intravenous mannitol in the treatment of orbital compartment syndrome. METHODS: An experimental study was conducted on 4 nonhuman primates (8 orbits). Orbital compartment syndrome was simulated by injecting autologous blood into both orbits of each nonhuman primate until a pressure of 80 mm Hg was reached (time 0). After 10 minutes, nonhuman primates were randomized to receive an infusion of either mannitol or saline, given over 15 minutes. Five minutes after the infusion was complete, lateral canthotomy and cantholysis was performed on both orbits in isolated steps every 5 minutes. During the study protocol, orbital and intraocular pressures were recorded every 5 minutes, with a final set of measurements at 60 minutes. The primary outcome measures were the mean change in pressure from time 0 to 60 minutes, as well as the mean change in pressure during the infusion period. RESULTS: There was no statistically significant difference in the mean changes in orbital or intraocular pressure from time 0 to 60 minutes of the protocol. However, during the infusion period there was significantly greater decrease in both orbital and intraocular pressure in the mannitol compared with saline group (-34.0 vs. -9.3 mm Hg for orbital pressure [p = 0.03]; -34.8 vs. -9.7 mm Hg for intraocular pressure [p = 0.04]). CONCLUSIONS: While the definitive treatment of orbital compartment syndrome is lateral canthotomy and cantholysis, mannitol results in a rapid and clinically meaningful drop in orbital and intraocular pressure. The authors believe that their data support the routine use of mannitol in orbital compartment syndrome, especially when there is a delay in timely surgical management.

Identifying predictive morphologic features of malignancy in eyelid lesions.

OBJECTIVE: To determine features of eyelid lesions most predictive of malignancy, and to design a key to assist general practitioners in the triaging of such lesions. DESIGN: Prospective observational study. SETTING: Department of Ophthalmology at Queen's University in Kingston, Ont. PARTICIPANTS: A total of 199 consecutive periocular lesions requiring biopsy or excision were included. MAIN OUTCOME MEASURES: First, potential features suggestive of malignancy for eyelid lesions were identified based on a survey sent to Canadian oculoplastic surgeons. The sensitivity, specificity, and odds ratios (ORs) of these features were then determined using 199 consecutive photographed eyelid lesions of patients who presented to the Department of Ophthalmology and underwent biopsy or excision. A triage key was then created based on the features with the highest ORs, and it was pilot-tested by a group of medical students. RESULTS: Of the 199 lesions included, 161 (80.9%) were benign and 38 (19.1%) were malignant. The 3 features with the highest ORs in predicting malignancy were infiltration (OR = 18.2, P < .01), ulceration (OR = 14.7, P < .01), and loss of eyelashes (OR = 6.0, P < .01). The acronym LUI (loss of eyelashes, ulceration, infiltration) was created to assist in memory recall. After watching a video describing the LUI triage key, the mean total score of a group of medical students for correctly identifying malignant lesions increased from 46% to 70% (P < .001). CONCLUSION: Differentiating benign from malignant eyelid lesions can be difficult even for experienced physicians. The LUI triage key provides physicians with an evidence-based, easy-to-remember system for assisting in the triaging of these lesions.

Orbital compartment syndrome in a burn patient without aggressive fluid resuscitation.

INTRODUCTION: Orbital compartment syndrome may rarely occur in the setting of burns where therapy includes aggressive fluid resuscitation. CASE: We report a case of bilateral orbital compartment syndrome in a 13-year-old male, with superficial facial burns secondary to hydrobromic acid, who did not receive aggressive fluid resuscitation. The patient was treated successfully with bilateral lateral canthotomy and cantholysis. COMMENT: Facial burns may lead to orbital compartment syndrome without aggressive fluid resuscitation, likely due to excessive leakage of fluid and protein into the orbit combined with an inflammatory reaction.

Ocular and systemic safety of bevacizumab and ranibizumab in patients with neovascular age-related macular degeneration.

PURPOSE OF REVIEW: This study reviews differences in both ocular and systemic safety between intravitreal bevacizumab and ranibizumab in the setting of neovascular age-related macular degeneration. RECENT FINDINGS: Serious adverse events associated with either bevacizumab or ranibizumab injections are generally rare. However, acute intraocular inflammation (AII) tends to occur more frequently following bevacizumab injection. Systemic absorption of bevacizumab is greater than with ranibizumab, and many studies have shown an increased risk of systemic adverse events in patients receiving bevacizumab compared with those receiving ranibizumab. SUMMARY: Although rare, adverse events with off-label use of bevacizumab are more common than with ranibizumab. Continued study into long-term safety of the two agents is warranted.

Do findings on routine examination identify patients at risk for primary open-angle glaucoma? The rational clinical examination systematic review.

IMPORTANCE: Glaucoma is the second leading cause of blindness worldwide, and its insidious onset is often associated with diagnostic delay. Since glaucoma progression can often be effectively diminished when treated, identifying individuals at risk for glaucoma could potentially lead to earlier detection and prevent associated vision loss. OBJECTIVE: To quantify the diagnostic accuracy of examination findings and relevant risk factors in identifying individuals with primary open-angle glaucoma (POAG), the most common form of glaucoma in North America. DATA SOURCES: Structured Medline (January 1950-January 2013) search and a hand search of references and citations of retrieved articles yielding 57 articles from 41 studies. STUDY SELECTION: Population-based studies of high-level methods relating relevant examination findings of cup-to-disc ratio (CDR), CDR asymmetry, intraocular pressure (IOP), and demographic risk factors to the presence of POAG. RESULTS: The summary prevalence of glaucoma in the highest-quality studies was 2.6% (95% CI, 2.1%-3.1%). Among risk factors evaluated, high myopia (≥6 diopters; odds ratio [OR], 5.7; 95% CI, 3.1-11) and family history (OR, 3.3; 95% CI, 2.0-5.6) had the strongest association with glaucoma. Black race (OR, 2.9; 95% CI, 1.4-5.9) and increasing age (especially age >80 years; OR, 2.9; 95% CI, 1.9-4.3) were also associated with an increased risk. As CDR increased, the likelihood for POAG increased with a likelihood ratio (LR) of 14 (95% CI, 5.3-39) for CDR of 0.7 or greater. Increasing CDR asymmetry was also associated with an increased likelihood for POAG (CDR asymmetry ≥0.3; LR, 7.3; 95% CI, 3.3-16). No single threshold for CDR or asymmetry ruled out glaucoma. The presence of a disc hemorrhage (LR, 12; 95% CI, 2.9-48) was highly suggestive of glaucoma, but the absence of a hemorrhage was nondiagnostic (LR, 0.94; 95% CI, 0.83-0.98). At the commonly used cutoff for high IOP (≥22), the LR was 13 (95% CI, 8.2-17), while lower IOP made glaucoma less likely (LR, 0.65; 95% CI, 0.55-0.76). We found no studies of screening examinations performed by generalist physicians in a routine setting. CONCLUSIONS AND RELEVANCE: Individual findings of increased CDR, CDR asymmetry, disc hemorrhage, and elevated IOP, as well as demographic risk factors of family history, black race, and advanced age are associated with increased risk for POAG, but their absence does not effectively rule out POAG. The best available data support examination by an ophthalmologist as the most accurate way to detect glaucoma.

Orbital metastasis secondary to merkel cell carcinoma: case report and literature review.

INTRODUCTION: Merkel cell carcinoma is an aggressive malignancy often associated with metastatic spread, but has never been reported to metastasize to the orbit. CASE: An 80 year old male with metastatic Merkel cell carcinoma presented with ptosis and extraocular movement abnormalities, and was found to have a lesion of the orbit consistent with metastatic spread. The lesion responded favorably to radiation therapy. COMMENT: Although the orbit is a frequent site of metastatic disease, this is the first reported case of presumed Merkel cell carcinoma metastasizing to the orbit.

epiDonate - distributed serverless data infrastructure for epidemiological studies.

Motivation: Epidemiological studies face two important challenges: the need to ingest ever more complex data types, and mounting concerns about participant privacy and data governance. These two challenges are compounded by the expectation that data infrastructure will eventually need to facilitate cross-registration of participants by multiple epidemiological studies. Implementation: The portable web-service epiDonate was developed using the serverless model known as FaaS (Function-as-a-Service). The reference implementation uses nodejs. The implementation relies on a simple tokenization scheme, mediated by a public API, that a) distinguishes admin from participant roles, with b) extensible permission configuration operating a read/write structure. General Features: The critical design feature of epiDonate is the absence of business logic on the server-side (the web service). The simplicity removes the need to customize virtual machines and enables ecosystems of multiple web Applications backed by one or more data donation deployments. Availability: https://episphere.github.io/donate.

Evolution of first-line glaucoma therapy, 2007-2018: a population-based analysis.

OBJECTIVE: To evaluate the long-term evolution of first-line glaucoma therapy (FLGT) initiated by ophthalmologists and optometrists. DESIGN: Retrospective population-based study using validated provincial health care databases. PARTICIPANTS: 194,759 Ontario residents, 66 years of age or older, who received FLGT between 2007 and 2018. METHODS: A total of 194,759 individuals from 12 annual cohorts were enrolled, and rates of first-line medical treatment (prostaglandin analogue [PGA], beta-blocker, alpha-2-agonist, and carbonic anhydrase inhibitor) and laser trabeculoplasty (LT) were calculated. Provider (ophthalmologist or optometrist) rates also were assessed. RESULTS: Across the entire study period, of the 194,759 enrolled individuals who received FLGT, 60.2% initially received medical treatment and 39.8% underwent LT. Approximately 94.6% were treated by ophthalmologists. PGA therapy was the most common therapy prior to 2010, whereupon LT became the most common FLGT. By 2015, LT exceeded the total of all medications as FLGT. The annual rate of initial medication prescriptions by optometrists rose to 101.4 per 100,000 population between 2011 and 2018. In 2018, PGA and non-PGA prescription rates by ophthalmologists were 2.6 and 5.0 times higher, respectively, than prescription rates by optometrists. CONCLUSION: LT therapy has become the most common FLGT for Ontario residents 66 years of age or older. PGAs remain the most frequently prescribed glaucoma medication. While ophthalmologists continue to provide the majority of FLGT, optometrists now provide a small but growing fraction of FLGT following the introduction of glaucoma medication prescribing privileges.

Topical pain control for corneal abrasions: A systematic review and meta-analysis.

OBJECTIVES: Corneal abrasions are common ophthalmic presentations to emergency departments. Among emergency physicians and ophthalmologists, there are highly variable practice patterns with regard to management of resultant pain and discomfort. The goal of this study was to review and analyze the efficacy and safety of topical pain therapies for corneal abrasions, including topical anesthetics, nonsteroidal anti-inflammatory drugs (NSAIDs), cycloplegics, steroids, pressure patching, and the use of a bandage contact lens (BCL). METHODS: The review followed the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) guidelines. The protocol was established a priori and published on PROSPERO (CRD42020201288). MEDLINE, EMBASE, CENTRAL, and Web of Science were searched until December 31, 2020. Primary studies comparing topical pain therapies to another therapy or control were included. Primary outcomes included percentage of corneal abrasions healed at 24, 48, and 72 hours, as well as pain control at 24 and 48 hours. Secondary outcomes included use of oral analgesia and incidence of complications. Risk of bias was assessed using validated tools. Quality of evidence was assessed using the GRADE methodology. RESULTS: Overall, 33 studies (31 randomized controlled trials [RCTs], two cohort studies) comprising 4,167 patients with corneal abrasions were analyzed. Only the data for topical NSAIDs were of adequate evidence from which to draw conclusions; topical NSAIDs demonstrated significantly reduced pain scores at 24 hours (standardized mean differences [SMD] -0.69, 95% CI = -0.98 to -0.41) and 48 hours (SMD = -0.56, 95% CI = -1.02 to -0.10) as well as 53% (95% CI = 34% to 67%) lower oral analgesia use compared to control. Based on available data, topical anesthetics, cycloplegics, patching, and the use of a BCL did not result in any significant difference in pain scores or use of oral analgesia, while no studies examined topical steroids. No interventions resulted in healing delays or significantly higher rates of complications compared to controls. CONCLUSIONS: There was strong evidence to support that topical NSAIDs reduce pain associated with corneal abrasions in the first 48 hours and the need for oral analgesia. The existing evidence was insufficient to support or refute the use of topical anesthetics, cycloplegics, steroids, or BCL for pain control in corneal abrasions. Pressure patching was ineffective at pain reduction and may increase the risk of complications. Delays in healing or other complications were not significantly different between any intervention or control for simple, uncomplicated corneal abrasions; however, larger RCTs are required to identify any differences in rare complications.

Distribution and Predictors of Initial Glaucoma Care Among Ophthalmologists and Optometrists: A Population-based Study.

PURPOSE: To evaluate evolution in the distribution of new glaucoma patients between ophthalmologists and optometrists, and to examine factors predicting provider type, in the context of expansion in the scope of optometry practice. PATIENTS AND METHODS: A population-based study was undertaken using validated datasets in Ontario, Canada from 2007 to 2018, encompassing time before and after optometry practice scope expansion in 2011. All patients aged 66 and older receiving a glaucoma suspect diagnosis or first-line therapy for glaucoma from ophthalmologists or optometrists were enrolled. Predictors of provider type were evaluated using logistic regression. RESULTS: From 2007 to 2018, 401,560 patients received initial glaucoma care, including 303,440 by ophthalmologists and 98,120 by optometrists. Population rates of glaucoma suspect diagnosis increased for both providers over the study period. The rate of therapy initiation increased annually among optometrists after 2011, while the rate remained stable over that period among ophthalmologists. By 2018, 88% of patients initiating therapy and 59% of patients first diagnosed as a glaucoma suspect received that care from ophthalmologists. In the final study year, therapy initiations per provider were lower among optometrists (median: 2/provider; interquartile range: 1 to 3) than among ophthalmologists (median: 26.5/provider, interquartile range: 10 to 53). Patients were more likely to receive care from an ophthalmologist than an optometrist if they were older, had higher ocular or systemic comorbidity, or lived in urban settings. CONCLUSIONS: Optometrists have a large and growing role in diagnosing glaucoma suspects; however, despite scope expansion, optometrists play a much smaller role in initiating glaucoma therapy.

Predictors of Initial Glaucoma Therapy with Laser Trabeculoplasty versus Medication: A Population-Based Study.

PURPOSE: To investigate patient-level factors associated with first-line glaucoma therapy with laser trabeculoplasty (LT) versus topical medication. DESIGN: Population-based study. PARTICIPANTS: All patients 66 years of age and older in Ontario, Canada, receiving first-ever therapy for glaucoma with either LT or topical medication between April 1, 2007, and March 31, 2019. METHODS: Linked health care databases were used to identify patients receiving first-line glaucoma therapy and to ascertain patient-level factors potentially associated with receipt of LT versus medication. Multivariate logistic regression analyses were undertaken. MAIN OUTCOME MEASURES: Factors associated with receiving LT versus medications were evaluated using adjusted odds ratios (ORs) for age, gender, previous cataract surgery, previous corneal transplantation, previous retina surgery, level of systemic comorbidity, socioeconomic status (SES), and rural versus urban residence. RESULTS: In total, 194 759 patients were included. Older patients were less likely to be treated with LT versus medication (≥81 years of age vs. 66-70 years of age: OR, 0.49; 95% confidence interval [CI], 0.48-0.50), whereas women were more likely than men to receive LT (OR, 1.42; 95% CI, 1.39-1.45). Previous ocular surgeries were associated with decreased probability of treatment with LT, including cataract surgery (OR, 0.31; 95% CI, 0.30-0.32), corneal transplantation (OR, 0.39; 95% CI, 0.31-0.49), and retina surgery (OR, 0.46; 95% CI, 0.41-0.51). Patients with high comorbidity were less likely to receive LT (highest vs. lowest level of comorbidity: OR, 0.94; 95% CI, 0.91-0.97). Laser trabeculoplasty use was less likely among patients at higher levels of SES (highest vs. lowest level: OR, 0.86; 95% CI, 0.84-0.89) and from a rural residence (versus urban: OR, 0.92; 95% CI, 0.90-0.95). Increasing utilization of LT over time was noted (for each additional calendar year: OR, 1.05 per year; 95% CI, 1.05-1.05 per year). CONCLUSIONS: Our results identified patient characteristics associated with use of LT as primary therapy for glaucoma, including factors related to patient demographics, ocular history, and comorbidity. Many of these associations are unexpected based on efficacy data or evidence-based guidelines. These results are topical considering growing evidence supporting use of first-line LT.

Quality of life amongst American vs. Canadian patients with retinal diseases.

PURPOSE OF REVIEW: To compare health-related quality of life (HRQoL) in American vs. Canadian populations suffering from retinal diseases. RECENT FINDINGS: A search of Medline was conducted according to a strategy that combined the MeSH heading 'retinal diseases' with either of 'quality of life' as a MeSH or 'utility' as a keyword. We included studies of American or Canadian patients using any of the National Eye Institute 25-item visual functioning questionnaire (NEI-VFQ-25), visual function index (VF-14), short form health survey (SF-36), or utility to assess HRQoL. A total of 22 studies with American patients and five with Canadian patients were found. There was no significant HRQoL difference found between the American and Canadian patients for any of the HRQoL instruments (P = 0.14-0.80); however, for all instruments mean HRQoL correlated positively with mean visual acuity in the better-seeing eye (P < 0.001). SUMMARY: On the basis of a review of the currently published literature, we were unable to detect significant differences in HRQoL between American and Canadian patients. Further research into the topic is necessary.

Acute-onset floaters and flashes: is this patient at risk for retinal detachment?

CONTEXT: Acute onset of monocular floaters and/or flashes represents a common presentation to primary care physicians, and the most likely diagnosis is posterior vitreous detachment (PVD). A significant proportion of patients with acute PVD develop an associated retinal tear that can lead to retinal detachment and permanent vision loss if left untreated. OBJECTIVE: To quantify the association between relevant clinical variables and risk of retinal tear in patients presenting with acute-onset floaters and/or flashes and PVD. DATA SOURCES: Structured MEDLINE (January 1950-September 2009) and EMBASE (January 1980-September 2009) searches and a hand search of references and citations of retrieved articles yielded 17 relevant studies. STUDY SELECTION: Studies of high-level methods that related elements of the history or physical examination in patients presenting with floaters and/or flashes and PVD to the likelihood of retinal tear. RESULTS: For patients with acute onset of floaters and/or flashes who are self-referred or referred to an ophthalmologist, the prevalence of retinal tear is 14% (95% confidence interval [CI], 12%-16%). Subjective visual reduction is the most important symptom associated with retinal tear (likelihood ratio [LR], 5.0; 95% CI, 3.1-8.1). Vitreous hemorrhage on slitlamp biomicroscopy is the best-studied finding with the narrowest positive LR for retinal tear (summary LR, 10; 95% CI, 5.1-20). Absence of vitreous pigment during this examination is the best-studied finding with the narrowest negative LR (summary LR, 0.23; 95% CI, 0.12-0.43). Patients initially diagnosed as having uncomplicated PVD have a 3.4% chance of a retinal tear within 6 weeks. The risk increases with new onset of at least 10 floaters (summary LR, 8.1-36) or subjective visual reduction (summary LR, 2.3-17) during this period. CONCLUSIONS: Primary care physicians should evaluate patients with acute-onset floaters and/or flashes due to suspected PVD, or patients with known PVD and a change in symptoms, for high-risk features of retinal tear and detachment. Physicians should always assess these patients' visual acuity. Patients at increased risk should be triaged for urgent ophthalmologic assessment.

Effect of prophylactic nonsteroidal antiinflammatory drugs on cystoid macular edema assessed using optical coherence tomography quantification of total macular volume after cataract surgery.

PURPOSE: To evaluate the efficacy of prophylactic administration of the topical nonsteroidal antiinflammatory drug (NSAID) ketorolac tromethamine 0.5% on acute (within 4 weeks of surgery) cystoid macular edema (CME) and total macular volume (TMV) in patients having phacoemulsification cataract surgery. SETTING: Department of Ophthalmology, Queen's University, Hotel Dieu Hospital, Kingston, Ontario, Canada. METHODS: This open-label nonmasked randomized (random number assignment) study comprised 106 eyes of 98 patients. Exclusion criteria included hypersensitivity to the NSAID drug class, aspirin/NSAID-induced asthma, and pregnancy in the third trimester. Ketorolac tromethamine 0.5% was administered starting 2 days before surgery and for 29 days after surgery for a total of 31 days. The outcome measure was macular swelling, which was quantified by the optical coherence tomography. RESULTS: At 1 month, there was a statistically significant difference in TMV between the control group (0.4420 mm3) and the ketorolac group (0.2392 mm3), with the ketorolac group having 45.8% less macular swelling (P = .009). Multiple linear regression with backward selection indicated a 44.3% (P = .013) and 46.1% (P = .030) reduction in macular swelling in the ketorolac group at 1 week and 1 month, respectively. CONCLUSION: Used prophylactically after cataract surgery, ketorolac 0.5% was efficacious in decreasing postoperative macular edema.

Seasonal photosynthetic gas exchange and leaf reflectance characteristics of male and female cottonwoods in a riparian woodland.

Cottonwoods (Populus spp.) are dioecious phreatophytes of hydrological and ecological importance in riparian woodlands throughout the Northern Hemisphere. In streamside zones of southern Alberta, groundwater and soil water typically decline between May and September. To understand how narrowleaf cottonwoods (Populus angustifolia James) are adapted to this seasonal decrease in water availability, we measured photosynthetic gas exchange, leaf reflectance, chlorophyll fluorescence and stable carbon isotope composition (delta(13)C) in trees growing in the Oldman River valley of southern Alberta during the 2006 growth season. Accompanying the seasonal recession in river flow, groundwater table depth (Z(gw)) declined by 1.6 m, but neither mean daily light-saturated net photosynthetic rate (A(max)) nor stomatal conductance (g(s)) was correlated with this change. Both A(max) and g(s) followed a parabolic seasonal pattern, with July 24 maxima of 15.8 micromol m(-2) s(-1) and 559 mmol m(-2) s(-1), respectively. The early summer rise in A(max) was related to an increase in the chlorophyll pool during leaf development. Peak A(max) coincided with the maximum quantum efficiency of Photosystem II (F(v)/F(m)), chlorophyll index (CI) and scaled photochemical reflectance index (sPRI), but occurred one month after maximum volumetric soil water (theta(v)) and minimum Z(gw). In late summer, A(max) decreased by 30-40% from maximum values, in weak correlation with theta(v) (r(2) = 0.50). Groundwater availability limited late-season water stress, so that there was little variation in mean daily transpiration (E). Decreasing leaf nitrogen (% dry mass), CI, F(v)/F(m) and normalized difference vegetation index (NDVI) were also consistent with leaf aging effects. There was a strong correlation between A(max) and g(s) (r(2) = 0.89), so that photosynthetic water-use efficiency (WUE; A(max)/E) decreased logarithmically with increasing vapor pressure deficit in both males (r(2) = 0.75) and females (r(2) = 0.95). The male:female ratio was unequal (2:1, chi(2) = 16.5, P < 0.001) at the study site, but we found no significant between-sex differences in photosynthetic gas exchange, leaf reflectance or chlorophyll fluorescence that might explain the unequal ratio. Females tended to display lower NDVI than males (P = 0.07), but mean WUE did not differ significantly between males and females (2.1 +/- 0.2 versus 2.5 +/- 0.2 mmol mol(-1)), and delta(13)C remained in the -28.8 to -29.3 per thousand range throughout the growth season, in both sexes. These results demonstrate changes in photosynthetic and water-use characteristics that collectively enable vigorous growth throughout the season, despite seasonal changes in water supply and demand.