Anthony F. Alario

Manual corneal thickness measurements of healthy equine eyes using a portable spectral-domain optical coherence tomography device

REASONS FOR PERFORMING STUDY Corneal thickness measurements of the equine globe using spectral-domain optical coherence tomography (SD-OCT) have not been reported. OBJECTIVES To determine corneal thickness measurements and the intra- and interoperator reliability of a portable SD-OCT device in equine eyes. STUDY DESIGN Prospective observational study. METHODS Horses free of ocular disease were used for this study. Gentle manual restraint, in combination with detomidine hydrochloride and a head stand, were employed to ensure proper animal positioning. Corneal pachymetry measurements were obtained from both eyes of each animal 3 times by 2 operators in succession. A 6 mm corneal pachymetry protocol was performed using a portable SD-OCT device. All measurements were obtained manually by one operator (C.G.P.) using the integrated calliper function. Measurements included epithelial thickness, stromal thickness, Descemets membrane thickness and total corneal thickness. All recorded measurements were analysed to determine both intra- and interoperator reliability. RESULTS Thirty horses with a mean age of 10.6 ± 6.4 years were examined. Mean epithelial, stromal, Descemets membrane and total corneal thickness values obtained were, respectively, 174.7 ± 13.6, 599.2 ± 45.4, 38.4 ± 15.3 and 812.0 ± 44.1 μm for operator A and 175.9 ± 12.9, 599.2 ± 44.9, 38.4 ± 15.0 and 812.9 ± 42.9 μm for operator B. A positive correlation was found between Descemets membrane thickness and age, whereby Descemets membrane thickness increased by 2 μm/year (P<0.0001). The coefficients of variation for both operators were <4% for all measurements. Intraclass correlations ranged from 0.92 to 0.98. CONCLUSIONS Manual corneal thickness measurement using a portable SD-OCT device provides epithelial, stromal, Descemets membrane and total corneal thickness measurements with clinically acceptable intra- and interoperator reliability in healthy equine eyes.

Central corneal thickness measurements in normal dogs: a comparison between ultrasound pachymetry and optical coherence tomography

OBJECTIVE To compare central corneal thickness (CCT) measurements obtained from normal canines using a spectral-domain optical coherence tomography device (SD-OCT) and an ultrasonic pachymeter. ANIMALS Fifteen clinically normal dogs. PROCEDURES Dogs were briefly anesthetized with propofol. Central corneal thickness measurements were obtained from both eyes of each animal four times by one operator using a SD-OCT system. The CCT was automatically calculated using the pachymetry software generated from eight radial scans, 6 mm in length. Ultrasonic pachymetry was then performed in both eyes of each animal by one operator five times in succession. The CCT was recorded for each modality and compared statistically for agreement and bias. RESULTS Fifteen dogs (seven castrated male, eight spayed female) with a mean age of 2.3 ± 1.3 years were examined. The mean CCT for all eyes examined via SD-OCT and ultrasonic pachymetry (velocity set at 1636 m/s) was 587.72 ± 32.44 μm and 598.54 ± 32.28 μm, respectively. Ultrasonic pachymetry consistently overestimated CCT as compared to OCT by a mean value of 10.82 μm (P < 0.0001). No significant difference in CCT was found based on the age or sex of the animal. There was no significant difference in CCT measurements between replicates performed by the same operator for each modality. The coefficient of variation within and between imaging modalities was low (range 0.63-2.5%). The intraclass correlation coefficient comparing methods was 0.92. CONCLUSIONS Correlation between modalities was excellent; however, ultrasonic pachymetry set at a standard velocity of 1636 m/s overestimates CCT as compared to OCT.

Intra and inter-user reliability of central corneal thickness measurements obtained in healthy feline eyes using a portable spectral-domain optical coherence tomography device

OBJECTIVE To determine the intra and inter-user reliability of central corneal thickness (CCT) measurements obtained using a portable spectral-domain optical coherence tomography (SD-OCT) device in healthy feline eyes. ANIMALS Twenty clinically normal cats. PROCEDURES Gentle manual restraint was utilized for proper animal positioning. Central corneal thickness measurements were obtained from both eyes of each animal three times by two operators in succession. A 6 mm, corneal pachymetry protocol was performed using the Optovue® iVue SD-OCT system. The CCT was automatically calculated using the pachymetry software generated from eight radial scans, 6 mm in length. The CCT was recorded for each operator and compared statistically for both intra and inter-user reliability. RESULTS Twenty cats (11 CM, 9 SF) with a mean age of 4.7 years were examined. The mean CCT for all eyes examined was 629.08 ± 47.05 μm. No significant difference in CCT was found based on the eye examined (OD vs. OS) or age of the animal. However, the CCT of spayed females was significantly higher (42.64 ± 18.0 μm) as compared to castrated males (P = 0.03). There was no significant difference in CCT measurements between replicates performed by the same operator or between operators. The mean difference in CCT between operators was 0.38 μm. The coefficient of variation for each user and between users was very low (range 0.68-1.5%). The intra-class correlation coefficient comparing operators was 0.975. CONCLUSIONS The Optovue® iVue SD-OCT device is capable of obtaining CCT measurements with excellent intra and interoperator reliability in healthy feline eyes.

A spectral-domain optical coherence tomography device provides reliable corneal pachymetry measurements in canine eyes

The objective of this study was to determine central corneal thickness (CCT) and the intra- and interuser reliability using a portable spectral-domain optical coherence tomography (SD-OCT) device in canine eyes. Twenty clinically normal dogs were examined. CCT measurements were obtained from both eyes of each animal three times by two operators in succession. The CCT was automatically calculated using the pachymetry software generated from eight radial scans, 6 mm in length. Mean canine CCT was 606.83±39.45 μm for all eyes examined. There was no significant difference in CCT based on the eye examined (OD vs OS), age or gender of the animal. There was no significant difference in CCT between replicates performed by the same operator; however, a small but significant difference was noted in CCT between operators. The mean difference in CCT between operators was 1.9 μm (P=0.03). The coefficient of variation for each user and between users was very low (range 0.64–1.7 per cent). The intraclass correlation coefficient comparing operators was 0.975. Based on these results, the SD-OCT device evaluated is capable of obtaining precise CCT measurements with excellent intra- and interoperator reliability in canine eyes.

Anterior segment fluorescein angiography of the normal feline eye using a dSLR camera adaptor.

PURPOSE To describe anterior segment fluorescein angiography (ASFA) of the normal feline eye using a digital single-lens reflex (dSLR) camera adaptor. ANIMALS Ten cats free of ocular and systemic disease were evaluated. METHODS All cats received maropitant citrate (1.0 mg/kg SQ) and diphenhydramine (2.0 mg/kg SQ) 20 min prior to anesthesia using propofol (4 mg/kg IV bolus, 0.2 mg/kg/min CRI). Standard color and red-free images were obtained prior to the administration of 10% sodium fluorescein (20 mg/kg IV). Imaging was performed using a dSLR camera (Canon 7D), dSLR camera adaptor, camera lens (Canon EF-S 60 mm f/2.8 macro), and an accessory flash (Canon 580EXII). Imaging occurred at a rate of 1/second immediately following IV bolus of sodium fluorescein for a total of 30 s, then at 1, 2, 3, 4, 5, and 10 min. RESULTS Ten cats with an average age of 3.7 ± 0.9 years and various iris colors were imaged. Arterial, capillary, and venous phases occurred 4.6, 7.8, and 8.9 s postinjection, respectively. Visibility of the vasculature was not impaired by the degree of iris pigmentation. Patency of a persistent pupillary membrane was noted in one cat. Vessel leakage was common, as well as, leakage into the aqueous humor. Proper patient positioning and restricted ocular movements were critical. No adverse events were noted. CONCLUSIONS This study demonstrates ASFA findings in normal feline eyes using a cost-effective dSLR camera adaptor. Fluorescein leakage from vessels and into the aqueous humor was a common finding. Visibility of iris vasculature was not impaired by the degree of iris pigmentation.

Histopathologic evaluation of the anterior segment of eyes enucleated due to glaucoma secondary to primary lens displacement in 13 canine globes

PURPOSE  To describe histologic anterior segment changes in eyes affected with primary lens displacement (PLD) and secondary glaucoma. METHODS  Histologic sections stained with H&E from canine eyes enucleated because of PLD and secondary glaucoma were examined. RESULTS  Thirteen eyes from 12 patients were evaluated. Four dogs were castrated males and eight spayed females. Median age was 8 years of age (range 3-13). Breeds included seven terriers and five other breeds. All eyes examined demonstrated varying degrees of inflammation involving the iris and cleft. Mononuclear and melanophagic infiltration of the cleft was found in all specimens. Four globes also showed polymorphonuclear infiltrate. Pre-iridal fibrovascular membranes were clearly identified in 10 of 13 eyes. Total inflammatory score was significantly greater in all globes examined compared with an age-matched group of normal dogs. The posterior pigmented iris epithelium demonstrated a consistent pattern of hyperplasia and/or hypertrophy and cystic degeneration, more prominent in the more central regions. In some cases, hyperplasia was of greatest severity in the mid-iris and associated with thinning or flattening of the pupillary region. CONCLUSIONS  These results suggest that lens instability may be associated with chronic inflammation and secondary glaucoma. Mechanical irritation from an unstable lens may result in hypertrophy and/or hyperplasia of the posterior pigmented iris epithelium and subsequent cellular exfoliation and release of melanin. An inflammatory reaction directly or indirectly related to melanin release may obstruct the outflow pathways ultimately leading to glaucoma and loss of vision. Use of topical steroids may be warranted in dogs with PLD.

Anterior segment angiography of the normal canine eye: a comparison between indocyanine green and sodium fluorescein.

The objective of this study was to assess and compare indocyanine green (IG) and sodium fluorescein (SF) angiographic findings in the normal canine anterior segment using a digital single lens reflex (dSLR) camera adaptor. Images were obtained from 10 brown-eyed Beagles, free of ocular and systemic disease. All animals received butorphanol (0.2 mg/kg IM), maropitant citrate (1.0 mg/kg SC) and diphenhydramine (2.0 mg/kg SC) 20 min prior to propofol (4 mg/kg IV bolus, 0.2 mg/kg/min continuous rate infusion). Standard color imaging was performed prior to the administration of 0.25% IG (1 mg/kg IV). Imaging was performed using a full spectrum dSLR camera, dSLR camera adaptor, camera lens (Canon 60 mm f/2.8 Macro) and an accessory flash. Images were obtained at a rate of 1/s immediately following IG bolus for 30 s, then at 1, 2, 3, 4 and 5 min. Ten minutes later, 10% SF (20 mg/kg IV) was administered. Imaging was repeated using the same adaptor system and imaging sequence protocol. Arterial, capillary and venous phases were identified during anterior segment IG angiography (ASIGA) and their time sequences were recorded. ASIGA offered improved visualization of the iris vasculature in heavily pigmented eyes compared to anterior segment SF angiography (ASSFA), since visualization of the vascular pattern during ASSFA was not possible due to pigment masking. Leakage of SF was noted in a total of six eyes. The use of IG and SF was not associated with any observed adverse events. The adaptor described here provides a cost-effective alternative to existing imaging systems.

Anterior segment fluorescein angiography of the normal canine eye using a dSLR camera adaptor: ANTERIOR SEGMENT FLUORESCEIN ANGIOGRAPHY IN DOGS

PURPOSE  To describe anterior segment fluorescein angiography (ASFA) of the normal canine eye using two different sedation/anesthetic protocols and a digital single lens-reflex (dSLR) camera adaptor. METHODS Dogs free of ocular and systemic disease were used for this study. Dogs received maropitant citrate (1.0 mg/kg SQ) and diphenhydramine (2.0mg/kg SQ) 20min prior to butorphanol [n = 6] (0.2 mg/kg IV) or propofol [n=6] (4 mg/kg IV bolus, 0.2 mg/kg/min CRI). Standard color and red-free images were obtained prior to administration of 10% sodium fluorescein (20 mg/kg IV). Image acquisition was performed using a dSLR camera (Canon 7D), dSLR camera adaptor, camera lens (Canon EF-S 60 mm f/2.8 macro), and an accessory flash (Canon 580EXII). Imaging occurred at a rate of 1/s immediately following bolus for a total of 30 s, then at 1, 2, 3, 4, 5, and 10 min. RESULTS  Twelve dogs with a combined mean age of 5.1 years and various iris colors were imaged. Arterial, capillary, and venous phases were identified and time sequences recorded. Visibility of the vascular pattern was inversely related to iris pigmentation. Complete masking of blood flow was noted with heavily pigmented irises. Vessel leakage was noted in some eyes. Proper patient positioning and restricted ocular movements were critical in acquiring quality images. No adverse events were noted. CONCLUSION This study demonstrated that quality high resolution ASFA images were obtainable using a novel dSLR camera adaptor. ASFA of the normal canine eye is limited to irises, which are moderately to poorly pigmented. Use of general anesthesia produced higher quality images and is recommended for ASFA in the dog.

Use of indocyanine green and sodium fluorescein for anterior segment angiography in ophthalmologically normal cats

OBJECTIVE To assess and compare results of anterior segment angiography of ophthalmologically normal cats following IV injection with indocyanine green and sodium fluorescein dyes. ANIMALS 10 client-owned cats. PROCEDURES Anterior segment angiography was performed in anesthetized cats following administration of 0.25% indocyanine green (1.0 mg/kg, IV) or 10% sodium fluorescein (20 mg/kg, IV) solution. All cats received both treatments. Imaging (1 eye/cat) was performed with a full-spectrum digital single-lens reflex camera equipped with an adaptor (1 image/s for 30 seconds) immediately following IV dye injection and 1, 2, 3, 4, and 5 minutes after injection. Onset and duration of arterial, capillary, and venous phases of iris vasculature were identified and compared statistically between treatments. Degree of iridal pigmentation, leakage of dye from iris vasculature, and image quality were subjectively assessed. RESULTS No differences were found in onset or duration of vascular phases between treatments. Visibility of the iris vasculature was not impaired by poor or moderate iridal pigmentation with either method. Indocyanine green provided subjectively better vascular detail and image contrast than sodium fluorescein. No vascular dye leakage was observed following indocyanine green administration. Leakage of dye from blood vessels in the stroma (in 10 cats) and presence of dye in the anterior chamber (in 5 cats) were detected after sodium fluorescein administration. CONCLUSIONS AND CLINICAL RELEVANCE Images obtained with either fluorescent dye were considered to be of diagnostic quality. Lack of leakage following indocyanine green administration suggested this treatment may have better diagnostic utility for anterior segment angiography. The photographic equipment used provided a cost-effective alternative to existing imaging systems.

Medical Treatment of Primary Canine Glaucoma

Glaucoma is a painful and often blinding group of ocular diseases for which there is no cure. Although the definition of glaucoma is rapidly evolving, elevated intraocular pressure (IOP) remains the most consistent risk factor of glaucoma in the canine patient. Therapy should be aimed at neuroprotection. The mainstay of therapy focuses on reducing IOP and maintaining a visual and comfortable eye. This article discusses the most current ocular hypotensive agents, focusing on their basic pharmacology, efficacy at lowering IOP, and recommended use in the treatment of idiopathic canine glaucoma.