Equine Veterinary Journal ISSN 0425-1644 DOI: 10.1111/evj.12437
Editorial
Clinical equine ophthalmology: The current state of the art This month, Equine Veterinary Journal, Equine Veterinary Education and Veterinary Ophthalmology have jointly created an online collection ‘Clinical Equine Ophthalmology: The Current State of the Art’ which can be accessed via the home pages of all 3 journals. The articles in this online collection represent advances in clinical equine ophthalmology over several years. Equine ophthalmology has benefited from increased interaction between practitioners and specialists as equine practitioners have demonstrated increasing interest and sought out additional training in ophthalmology and more veterinary ophthalmologists have focused on ocular disease in the horse. The goal of this online collection is to bring these advances, which together comprise the current state of the art in equine ophthalmology, to a wider audience than had access to each article individually.
Ulcerative and nonulcerative keratitis The first 7 articles offer new approaches to the diagnosis and treatment of ulcerative and nonulcerative keratitis in the horse. In the case series by Ledbetter et al., building upon earlier work by the first author describing the use of confocal microscopy to describe the morphology of the normal equine cornea and to diagnose equine fungal keratitis, in vivo confocal microscopy was used to further characterise corneal lesions identified during clinical examination with slit lamp biomicroscopy [1]. The depth and location of corneal opacities were precisely quantified and the surrounding stroma evaluated for the presence and character of cellular infiltrate and infectious organisms. In all but one patient anaesthetised for surgical corneal foreign body removal, confocal microscopy was performed using only standing sedation. This imaging modality has the potential to provide diagnosis of corneal opacities more specific than can be made using slit lamp biomicroscopy and more rapid than can be made using histopathology. Ophthalmology is by its very nature a visual specialty with diagnoses often made based on identification of visible features. By taking advantage of imaging modalities that can make even histological detail visible in vivo, the diagnosis of equine corneal disease can be raised to a new standard of accuracy. A drug delivery device that has the potential to reduce or even eliminate the need for topical treatment of chronic corneal disease in horses has been developed by Gilger et al. [2]. These silicone matrix episcleral implant devices are surgically placed in the episcleral space under standing sedation or short-acting general anaesthesia. In a retrospective case series reporting the use of these episcleral implants to deliver cyclosporine to horses with nonulcerative keratitis, which had responded favourably to topical immunosuppressive therapy, keratitis in 13 of 19 horses (68%) was controlled for approximately 6 months following implant placement although continued topical therapy was necessary in some cases. Nonulcerative keratitis is a diagnostic as well as therapeutic challenge. It is difficult to rule out infectious aetiologies without diagnostic samples for corneal culture or cytology and the degree of ocular pain and other signs of uveitis can be variable in horses with nonulcerative keratitis. Diagnostic challenge aside, episcleral drug delivery devices have the potential to revolutionise treatment of chronic corneal disease. Chronic ulcerative corneal disease can be frustrating for owners as well as painful for affected horses. Eosinophilic keratitis is a chronic inflammatory ulcerative corneal disease of the equine cornea for which there are too few effective treatment options. In the retrospective series of eosinophilic keratitis cases in this issue, treatment with systemic corticosteroids was found to decrease the duration of clinical signs and treatment with the systemic antihistamine cetirizine was found to decrease likelihood of recurrence [3]. In another retrospective study of ulcerative keratitis in this issue, treatment with diamond burr debridement, which can be performed under standing sedation with topical anaesthesia, was associated with resolution of nonhealing ulcers in horses [4]. Nonhealing ulcers, like eosinophilic keratitis, while rarely associated with catastrophic Equine Veterinary Journal 47 (2015) 251–253 © 2015 EVJ Ltd
outcomes such as globe loss or blindness, are commonly encountered in equine practice and thus advances in their treatment offer a significant contribution to state of the art equine ophthalmology. A collaborative effort between 6 practices identified a series of 9 Friesians who presented with corneal lesions characterised by bilaterally symmetric stromal loss [5]. The clinical syndrome, which appeared to be bilaterally asymmetrically progressive but responded well to surgical repair, was characterised as a corneal dystrophy and compared with pellucid marginal degeneration in people. By compiling cases and evaluating pedigree data from affected horses, this syndrome of stromal loss was found to occur more frequently in males and was suggested to have a genetic component in Friesian horses. An individual case report would have been interesting but a case series allows more confidence in the conclusions drawn. This case series, which presents a new breedassociated equine corneal disease, arose out of a query to the International Equine Ophthalmology Consortium (IEOC) LISTSERV, illustrating the potential power of social media in scientific endeavours. The review of equine corneal stromal abscess by Henriksen and colleagues explains the evolution in the understanding of the pathogenesis and treatment of this potentially blinding and globe threatening disease [6]. As recently as 30 years ago, the prognosis for retention of vision and even of the globe in horses with a corneal abscess was poor and surgical intervention very often relied upon enucleation of globes that failed to respond to medical therapy. By addressing this disease process surgically, diagnostic samples were more readily available for culture and histology, which allowed identification of infectious aetiologies and led to the conclusion that these abscesses were often due to fungal infection. Therapeutically, by removing infected tissue and replacing it with healthy donor cornea, microsurgical lamellar keratoplasty techniques imported from physician-based ophthalmology revolutionised surgical approaches to equine corneal stromal abscess management and resulted in a more favourable prognosis for retention of a visual comfortable eye. In the final article addressing the diagnosis and treatment of keratitis in horses, Voelter-Ratson et al. present a retrospective report of cases of keratomycosis in Switzerland [7]. Keratomycosis has traditionally been characterised as a disease of warm, wet climates such as the Southeastern United States but this article illustrates that fungal keratitis also occurs in Europe and can be associated with severe clinical disease, with 31% of horses in this retrospective study enucleated and 6% subjected to euthanasia. Diagnosis of fungal keratitis in this series was based primarily on cytology or histopathology and it is not clear if the same organisms are most prevalent as aetiological agents in Europe as elsewhere. As in more temperate climates, duration of treatment for fungal keratitis was prolonged in the cases in this series, with a median of 5 weeks of treatment with an antifungal medication. An important feature of cases in this series was disease severity at presentation; it is possible the keratomycosis is not recognised as readily in places like Europe where it is uncommon and thus referral was later in the course of disease. Wherever the horse and whatever the frequency of keratomycosis in that locale, it is critical that practitioners recognise the clinical signs and are comfortable with diagnostics necessary to identify this potentially devastating equine corneal disease.
Ophthalmic microsurgery In the next 3 articles, novel approaches to and complications associated with ophthalmic microsurgery in horses are presented. First, a review of the visual outcomes after corneal transplant to repair corneal perforation found that 65% were classified as visual post operatively, with an additional 16% retaining at least limited vision [8]. This result constitutes a success rate for retention of a visual globe approximately twice that reported in a similar series almost 20 years ago and suggests that ulcerative iris prolapse no longer need carry the poor prognosis for vision in equine
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patients that it has historically. Second, in a retrospective report describing the use of porcine urinary bladder extracellular matrix to treat keratomalacia, a 94% rate of vision retention suggests that this commercially available biomaterial may be a viable option for affected patients [9]. The third paper in this group describes Descemet’s membrane detachment, a complication of cataract surgery resulting in a disinsertion of Descemet’s membrane from the corneal stroma characterised clinically by corneal oedema in approximately 25% of horses that have undergone phacoemulsification as a surgical treatment for cataracts [10]. Descemet’s membrane detachment has not previously been described in horses.
Ocular neoplasia The next 3 articles address the diagnosis and treatment of ocular neoplasia. Giuliano et al. describe the successful use of photodynamic therapy to treat periocular squamous cell carcinoma [11]. This report sets a standard for clinical reports by quantifying rather than simply describing variables of interest such as tumour size and by employing survival analysis to allow inferences about efficacy to be drawn. There has been a reliance on single cases or small series descriptions without applying the rigour of inferential statistics and precluding direct comparisons between treatment modalities for far too long in equine ophthalmology. The review of ocular neoplasia provides an up-to-date summary of tumour types organised by anatomic location with clinical descriptions, treatment options and prognosis described for each [12]. The multicentre retrospective study of extraocular lymphoma in horses identified 2 factors strongly related to prognosis: eyelid involvement and diffuse distribution which were both strongly associated with a negative outcome [13]. This study provides another example which highlights the value of multicentre collaborations.
Equine recurrent uveitis Six articles provide valuable data regarding long-term outcomes following surgical intervention for equine recurrent uveitis (ERU), glaucoma and cataracts. The article by Gilger et al. (2010) presents a multicentre review of the long-term outcome of suprachoroidal cyclosporine implants placed in eyes affected by ERU [14]. Based on the results of this study which includes an impressive 151 eyes from 9 centres and echoes the theme of large samples and multicentre collaborations so critical for advancing the science of equine ophthalmology, it appears that suprachoroidal cyclosporine implants can effectively reduce frequency and severity of flare-ups of ERU and therefore extend the visual life of affected globes. This study, which adds to an already impressive body of work on the use of cyclosporine implants as a treatment for ERU, illustrates the value of a programmatic approach to research, which can effectively tighten the link between research and practice by moving from design and pilot studies to studies of clinical efficacy. Transcleral cyclophotocoagulation (TSCP) is a procedure designed to reduce intraocular pressure (IOP) in horses with glaucoma by damaging the ciliary body. The study included in this special issue is the effect of diode laser TSCP on normal equine eyes that were sacrificed 6 months post operatively and supports the use of TSCP as a means of lowering IOP in horses with glaucoma [15]. In addition, by combining the clinical progression of IOP changes over time with pathological changes in treated eyes, this paper suggests that the ciliary body does not appear to regenerate and thus argues against ciliary body regeneration as a cause of treatment failure in clinical cases treated with TSCP. As in the preceding paper on suprachoroidal cyclosporine implants, this report is part of a programmatic research programme directed at the study of equine glaucoma which is poorly understood and for which too few treatment options exist. The review of uveitic glaucoma provides a comprehensive summary of the pathogenesis, clinical appearance and treatment option of this blinding disease [16]. The next 2 papers present the results of fairly large, long-term retrospective studies of cataract surgery in horses [17,18]. These papers highlight the importance of long-term follow up with a low 54% rate of vision at approximately 3 years following surgery in one study and rapidly
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decreasing rates of vision over time with 87, 49, 35 and 26% of horses visual at 1, 6, 12 and 24 months following surgery. These papers suggest that vision immediately following surgery should not necessarily be considered a success as the cataract patient is far from out of the woods at that point. As stated in one paper ‘Horses can live for decades, and a successful visual outcome must be present for years to be considered a success.’
Retinal and orbital disease Finally, 3 articles present valuable new information regarding retinal and orbital disease. The report by Bracun et al. [19] used a technique called streak retinoscopy to measure refractive error, which can be described as the ability to focus on distant objects and is determined in part by the shape of the eye, in over 300 horses and ponies. Techniques to assess vision in horses are underutilised, particularly given the importance of good functional vision for many equine athletes and the relationship between visual testing and performance in horses is not well established. However, as suggested in this paper, more comprehensive visual testing may help identify visual causes of performance problems. Gerding et al. [20] identify clinical features in horses with orbital fractures that warrant more aggressive therapy and illustrate that prompt and aggressive therapy for affected horses can result in good functional and cosmetic outcomes. Premont et al. [21] describe a congenital disease in a family of Shetland and Deutsches Classic ponies which had previously been reported in other breeds. In addition to offering some of the most significant advances in equine clinical ophthalmology in a single issue, a salient feature of many of the articles in this special issue is that they arose out of collaborations between veterinary ophthalmologists with a special interest in horses and equine practitioners with a special interest in ophthalmology, between private practitioners and those in academia and between academicians from different institutions. Horses are large and treating them is expensive for the owner and veterinarian. By joining forces, sharing resources and compiling data across practices, meaningful numbers of patients can be averaged to abstract new knowledge and we can continue to advance the art of clinical equine ophthalmology. The online collection can be accessed at http://onlinelibrary.wiley.com/ journal/10.1001/(ISSN)2042-3306 or via the homepage of Equine Veterinary Journal wileyonlinelibrary.com/journal/evj, Equine Veterinary Education wileyonlinelibrary.com/journal/eve or Veterinary Ophthalmology wileyonlinelibrary.com/journal/vop. M. Lassaline and D.A. Wilkie† Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, USA and †Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, Ohio
References 1. Ledbetter, E.C., Irby, N.L. and Schaefer, D.M.W. (2014) In vivo confocal microscopy of corneal microscopic foreign bodies in horses. Vet. Ophthalmol. 17, Suppl. 1, 69-75. 2. Gilger, B.C., Stoppini, R., Wilkie, D.A., Clode, A.B., Pinto, N.H., Hempstead, J., Gerding, J. and Salmon, J.H. (2013) Treatment of immune-mediated keratitis in horses with episcleral silicone matrix cyclosporine delivery devices. Vet. Ophthalmol. 17, Suppl. 1, 23-30. 3. Lassaline-Utter, M., Miller, C. and Wotman, K.L. (2014) Eosinophilic keratitis in 46 eyes of 27 horses in the Mid-Atlantic United States (2008– 2012). Vet. Ophthalmol. 17, 311-320. 4. Lassaline-Utter, M., Cutler, T.J., Michau, T.M. and Nunnery, C.M. (2014) Treatment of nonhealing corneal ulcers in 60 horses with diamond burr debridement (2010–2013). Vet. Ophthalmol. 17, Suppl. 1, 76-81. 5. Lassaline-Utter, M., Gemensky-Metzler, A.J., Scherrer, N.M., Stoppini, R., Latimer, C.A., MacLaren, N.E. and Myrna, K.E. (2014) Corneal dystrophy in Friesian horses may represent a variant of pellucid marginal degeneration. Vet. Ophthalmol. 17, Suppl. 1, 186-194.
Equine Veterinary Journal 47 (2015) 251–253 © 2015 EVJ Ltd
Clinical equine ophthalmology
M. Lassaline and D.A. Wilkie
6. de Linde Henriksen, M., Andersen, P.H., Plummer, C.E., Mangan, B. and Brooks, D.E. (2013) Equine corneal stromal abscesses: an evolution in the understanding of pathogenesis and treatment during the past 30 years. Equine Vet. Educ. 25, 315-323. 7. Voelter-Ratson, K., Pot, S.A., Florin, M. and Spiess, B.M. (2013) Equine keratomycosis in Switzerland: a retrospective evaluation of 35 horses (January 2000–August 2011). Equine Vet. J. 45, 608-612. 8. de Linde Henriksen, M., Plummer, C.E., Mangan, B., Ben-Shlomo, G., Tsujita, H., Greenberg, S., Toft, N. and Brooks, D.E. (2012) Visual outcome after corneal transplantation for corneal perforation and iris prolapse in 37 horses: 1998–2010. Equine Vet. J. 44, Suppl. 43, 115-119. 9. Mancuso, L.A., Lassaline, M. and Scherrer, N.M. (2014) Porcine urinary bladder extracellular matrix grafts (ACell Vetâ Corneal Discs) for keratomalacia in 17 equids (2012–2013). Vet. Ophthalmol. Doi: 10.1111/ vop.12240. 10. Matas Riera, M., Donaldson, D. and Priestnall, S.L. (2014) Descemet’s membrane detachment in horses; case series and literature review. Vet. Ophthalmol. Doi: 10.1111/vop.12199. 11. Giuliano, E.A., Johnson, P.J., Delgado, C., Pearce, J.W. and Moore, C.P. (2013) Local photodynamic therapy delays recurrence of equine periocular squamous cell carcinoma compared to cryotherapy. Vet. Ophthalmol. 17, Suppl. 1, 37-45. 12. Montgomery, K.W. (2014) Equine ocular neoplasia: a review. Equine Vet. Educ. 26, 372-380. 13. Schnoke, A.T., Brooks, D.E., Wilkie, D.A., Dwyer, A.E., Matthews, A.G., Gilger, B.C., Hendrix, D.V., Pickett, P., Grauwels, M., Monroe, C. and
Equine Veterinary Journal 47 (2015) 251–253 © 2015 EVJ Ltd
14.
15.
16. 17.
18.
19. 20.
21.
Plummer, C.E. (2013) Extraocular lymphoma in the horse. Vet. Ophthalmol. 16, 35-42. Gilger, B.C., Wilkie, D.A., Clode, A.B., McMullen, R.J. Jr, Utter, M.E., Komaromy, A.M., Brooks, D.E. and Salmon, J.H. (2010) Long-term outcome after implantation of a suprachoroidal cyclosporine drug delivery device in horses with recurrent uveitis. Vet. Ophthalmol. 13, 294-300. Cavens, V.J.K., Gemensky-Metzler, A.J., Wilkie, D.A., Weisbrode, S.E. and Lehman, A.M. (2012) The long-term effects of semiconductor diode laser transscleral cyclophotocoagulation on the normal equine eye and intraocular pressure(a). Vet. Ophthalmol. 15, 369-375. Annear, M.J., Gemensky-Metzler, A.J. and Wilkie, D.A. (2012) Uveitic glaucoma in the horse. Equine Vet. Educ. 24, 97-105. Edelmann, M.L., McMullen, R., Stoppini, R., Clode, A. and Gilger, B.C. 2014.Retrospective evaluation of phacoemulsification and aspiration in 41 horses (46 eyes): visual outcomes vs. age, intraocular lens, and uveitis status. Vet. Ophthalmol. 17, Suppl. 1, 160-167. Brooks, D.E., Plummer, C.E., Carastro, S.M. and Utter, M.E. (2014) Visual outcomes of phacoemulsification cataract surgery in horses: 1990–2013. Vet. Ophthalmol. 17, Suppl. 1, 117-128. Bracun, A., Ellis, A.D. and Hall, C. (2014) A retinoscopic survey of 333 horses and ponies in the UK. Vet. Ophthalmol. 17, Suppl. 1, 90-96. Gerding, J.C., Clode, A., Gilger, B.C. and Montgomery, K.W. (2014) Equine orbital fractures: a review of 18 cases (2006–2013). Vet. Ophthalmol. 17, Suppl. 1, 97-106. Premont, J.E., Andersson, L. and Grauwels, M. (2013) Multiple congenital ocular anomalies syndrome in a family of Shetland and Deutsches Classic ponies in Belgium. Equine Vet. Educ. 25, 550-555.
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Editorial
Clinical equine ophthalmology: The current state of the art This month, Equine Veterinary Journal, Equine Veterinary Education and Veterinary Ophthalmology have jointly created an online collection ‘Clinical Equine Ophthalmology: The Current State of the Art’ which can be accessed via the home pages of all 3 journals. The articles in this online collection represent advances in clinical equine ophthalmology over several years. Equine ophthalmology has benefited from increased interaction between practitioners and specialists as equine practitioners have demonstrated increasing interest and sought out additional training in ophthalmology and more veterinary ophthalmologists have focused on ocular disease in the horse. The goal of this online collection is to bring these advances, which together comprise the current state of the art in equine ophthalmology, to a wider audience than had access to each article individually.
Ulcerative and nonulcerative keratitis The first 7 articles offer new approaches to the diagnosis and treatment of ulcerative and nonulcerative keratitis in the horse. In the case series by Ledbetter et al., building upon earlier work by the first author describing the use of confocal microscopy to describe the morphology of the normal equine cornea and to diagnose equine fungal keratitis, in vivo confocal microscopy was used to further characterise corneal lesions identified during clinical examination with slit lamp biomicroscopy [1]. The depth and location of corneal opacities were precisely quantified and the surrounding stroma evaluated for the presence and character of cellular infiltrate and infectious organisms. In all but one patient anaesthetised for surgical corneal foreign body removal, confocal microscopy was performed using only standing sedation. This imaging modality has the potential to provide diagnosis of corneal opacities more specific than can be made using slit lamp biomicroscopy and more rapid than can be made using histopathology. Ophthalmology is by its very nature a visual specialty with diagnoses often made based on identification of visible features. By taking advantage of imaging modalities that can make even histological detail visible in vivo, the diagnosis of equine corneal disease can be raised to a new standard of accuracy. A drug delivery device that has the potential to reduce or even eliminate the need for topical treatment of chronic corneal disease in horses has been developed by Gilger et al. [2]. These silicone matrix episcleral implant devices are surgically placed in the episcleral space under standing sedation or short-acting general anaesthesia. In a retrospective case series reporting the use of these episcleral implants to deliver cyclosporine to horses with nonulcerative keratitis, which had responded favourably to topical immunosuppressive therapy, keratitis in 13 of 19 horses (68%) was controlled for approximately 6 months following implant placement although continued topical therapy was necessary in some cases. Nonulcerative keratitis is a diagnostic as well as therapeutic challenge. It is difficult to rule out infectious aetiologies without diagnostic samples for corneal culture or cytology and the degree of ocular pain and other signs of uveitis can be variable in horses with nonulcerative keratitis. Diagnostic challenge aside, episcleral drug delivery devices have the potential to revolutionise treatment of chronic corneal disease. Chronic ulcerative corneal disease can be frustrating for owners as well as painful for affected horses. Eosinophilic keratitis is a chronic inflammatory ulcerative corneal disease of the equine cornea for which there are too few effective treatment options. In the retrospective series of eosinophilic keratitis cases in this issue, treatment with systemic corticosteroids was found to decrease the duration of clinical signs and treatment with the systemic antihistamine cetirizine was found to decrease likelihood of recurrence [3]. In another retrospective study of ulcerative keratitis in this issue, treatment with diamond burr debridement, which can be performed under standing sedation with topical anaesthesia, was associated with resolution of nonhealing ulcers in horses [4]. Nonhealing ulcers, like eosinophilic keratitis, while rarely associated with catastrophic Equine Veterinary Journal 47 (2015) 251–253 © 2015 EVJ Ltd
outcomes such as globe loss or blindness, are commonly encountered in equine practice and thus advances in their treatment offer a significant contribution to state of the art equine ophthalmology. A collaborative effort between 6 practices identified a series of 9 Friesians who presented with corneal lesions characterised by bilaterally symmetric stromal loss [5]. The clinical syndrome, which appeared to be bilaterally asymmetrically progressive but responded well to surgical repair, was characterised as a corneal dystrophy and compared with pellucid marginal degeneration in people. By compiling cases and evaluating pedigree data from affected horses, this syndrome of stromal loss was found to occur more frequently in males and was suggested to have a genetic component in Friesian horses. An individual case report would have been interesting but a case series allows more confidence in the conclusions drawn. This case series, which presents a new breedassociated equine corneal disease, arose out of a query to the International Equine Ophthalmology Consortium (IEOC) LISTSERV, illustrating the potential power of social media in scientific endeavours. The review of equine corneal stromal abscess by Henriksen and colleagues explains the evolution in the understanding of the pathogenesis and treatment of this potentially blinding and globe threatening disease [6]. As recently as 30 years ago, the prognosis for retention of vision and even of the globe in horses with a corneal abscess was poor and surgical intervention very often relied upon enucleation of globes that failed to respond to medical therapy. By addressing this disease process surgically, diagnostic samples were more readily available for culture and histology, which allowed identification of infectious aetiologies and led to the conclusion that these abscesses were often due to fungal infection. Therapeutically, by removing infected tissue and replacing it with healthy donor cornea, microsurgical lamellar keratoplasty techniques imported from physician-based ophthalmology revolutionised surgical approaches to equine corneal stromal abscess management and resulted in a more favourable prognosis for retention of a visual comfortable eye. In the final article addressing the diagnosis and treatment of keratitis in horses, Voelter-Ratson et al. present a retrospective report of cases of keratomycosis in Switzerland [7]. Keratomycosis has traditionally been characterised as a disease of warm, wet climates such as the Southeastern United States but this article illustrates that fungal keratitis also occurs in Europe and can be associated with severe clinical disease, with 31% of horses in this retrospective study enucleated and 6% subjected to euthanasia. Diagnosis of fungal keratitis in this series was based primarily on cytology or histopathology and it is not clear if the same organisms are most prevalent as aetiological agents in Europe as elsewhere. As in more temperate climates, duration of treatment for fungal keratitis was prolonged in the cases in this series, with a median of 5 weeks of treatment with an antifungal medication. An important feature of cases in this series was disease severity at presentation; it is possible the keratomycosis is not recognised as readily in places like Europe where it is uncommon and thus referral was later in the course of disease. Wherever the horse and whatever the frequency of keratomycosis in that locale, it is critical that practitioners recognise the clinical signs and are comfortable with diagnostics necessary to identify this potentially devastating equine corneal disease.
Ophthalmic microsurgery In the next 3 articles, novel approaches to and complications associated with ophthalmic microsurgery in horses are presented. First, a review of the visual outcomes after corneal transplant to repair corneal perforation found that 65% were classified as visual post operatively, with an additional 16% retaining at least limited vision [8]. This result constitutes a success rate for retention of a visual globe approximately twice that reported in a similar series almost 20 years ago and suggests that ulcerative iris prolapse no longer need carry the poor prognosis for vision in equine
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patients that it has historically. Second, in a retrospective report describing the use of porcine urinary bladder extracellular matrix to treat keratomalacia, a 94% rate of vision retention suggests that this commercially available biomaterial may be a viable option for affected patients [9]. The third paper in this group describes Descemet’s membrane detachment, a complication of cataract surgery resulting in a disinsertion of Descemet’s membrane from the corneal stroma characterised clinically by corneal oedema in approximately 25% of horses that have undergone phacoemulsification as a surgical treatment for cataracts [10]. Descemet’s membrane detachment has not previously been described in horses.
Ocular neoplasia The next 3 articles address the diagnosis and treatment of ocular neoplasia. Giuliano et al. describe the successful use of photodynamic therapy to treat periocular squamous cell carcinoma [11]. This report sets a standard for clinical reports by quantifying rather than simply describing variables of interest such as tumour size and by employing survival analysis to allow inferences about efficacy to be drawn. There has been a reliance on single cases or small series descriptions without applying the rigour of inferential statistics and precluding direct comparisons between treatment modalities for far too long in equine ophthalmology. The review of ocular neoplasia provides an up-to-date summary of tumour types organised by anatomic location with clinical descriptions, treatment options and prognosis described for each [12]. The multicentre retrospective study of extraocular lymphoma in horses identified 2 factors strongly related to prognosis: eyelid involvement and diffuse distribution which were both strongly associated with a negative outcome [13]. This study provides another example which highlights the value of multicentre collaborations.
Equine recurrent uveitis Six articles provide valuable data regarding long-term outcomes following surgical intervention for equine recurrent uveitis (ERU), glaucoma and cataracts. The article by Gilger et al. (2010) presents a multicentre review of the long-term outcome of suprachoroidal cyclosporine implants placed in eyes affected by ERU [14]. Based on the results of this study which includes an impressive 151 eyes from 9 centres and echoes the theme of large samples and multicentre collaborations so critical for advancing the science of equine ophthalmology, it appears that suprachoroidal cyclosporine implants can effectively reduce frequency and severity of flare-ups of ERU and therefore extend the visual life of affected globes. This study, which adds to an already impressive body of work on the use of cyclosporine implants as a treatment for ERU, illustrates the value of a programmatic approach to research, which can effectively tighten the link between research and practice by moving from design and pilot studies to studies of clinical efficacy. Transcleral cyclophotocoagulation (TSCP) is a procedure designed to reduce intraocular pressure (IOP) in horses with glaucoma by damaging the ciliary body. The study included in this special issue is the effect of diode laser TSCP on normal equine eyes that were sacrificed 6 months post operatively and supports the use of TSCP as a means of lowering IOP in horses with glaucoma [15]. In addition, by combining the clinical progression of IOP changes over time with pathological changes in treated eyes, this paper suggests that the ciliary body does not appear to regenerate and thus argues against ciliary body regeneration as a cause of treatment failure in clinical cases treated with TSCP. As in the preceding paper on suprachoroidal cyclosporine implants, this report is part of a programmatic research programme directed at the study of equine glaucoma which is poorly understood and for which too few treatment options exist. The review of uveitic glaucoma provides a comprehensive summary of the pathogenesis, clinical appearance and treatment option of this blinding disease [16]. The next 2 papers present the results of fairly large, long-term retrospective studies of cataract surgery in horses [17,18]. These papers highlight the importance of long-term follow up with a low 54% rate of vision at approximately 3 years following surgery in one study and rapidly
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decreasing rates of vision over time with 87, 49, 35 and 26% of horses visual at 1, 6, 12 and 24 months following surgery. These papers suggest that vision immediately following surgery should not necessarily be considered a success as the cataract patient is far from out of the woods at that point. As stated in one paper ‘Horses can live for decades, and a successful visual outcome must be present for years to be considered a success.’
Retinal and orbital disease Finally, 3 articles present valuable new information regarding retinal and orbital disease. The report by Bracun et al. [19] used a technique called streak retinoscopy to measure refractive error, which can be described as the ability to focus on distant objects and is determined in part by the shape of the eye, in over 300 horses and ponies. Techniques to assess vision in horses are underutilised, particularly given the importance of good functional vision for many equine athletes and the relationship between visual testing and performance in horses is not well established. However, as suggested in this paper, more comprehensive visual testing may help identify visual causes of performance problems. Gerding et al. [20] identify clinical features in horses with orbital fractures that warrant more aggressive therapy and illustrate that prompt and aggressive therapy for affected horses can result in good functional and cosmetic outcomes. Premont et al. [21] describe a congenital disease in a family of Shetland and Deutsches Classic ponies which had previously been reported in other breeds. In addition to offering some of the most significant advances in equine clinical ophthalmology in a single issue, a salient feature of many of the articles in this special issue is that they arose out of collaborations between veterinary ophthalmologists with a special interest in horses and equine practitioners with a special interest in ophthalmology, between private practitioners and those in academia and between academicians from different institutions. Horses are large and treating them is expensive for the owner and veterinarian. By joining forces, sharing resources and compiling data across practices, meaningful numbers of patients can be averaged to abstract new knowledge and we can continue to advance the art of clinical equine ophthalmology. The online collection can be accessed at http://onlinelibrary.wiley.com/ journal/10.1001/(ISSN)2042-3306 or via the homepage of Equine Veterinary Journal wileyonlinelibrary.com/journal/evj, Equine Veterinary Education wileyonlinelibrary.com/journal/eve or Veterinary Ophthalmology wileyonlinelibrary.com/journal/vop. M. Lassaline and D.A. Wilkie† Department of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, USA and †Department of Veterinary Clinical Sciences, The Ohio State University, Columbus, Ohio
References 1. Ledbetter, E.C., Irby, N.L. and Schaefer, D.M.W. (2014) In vivo confocal microscopy of corneal microscopic foreign bodies in horses. Vet. Ophthalmol. 17, Suppl. 1, 69-75. 2. Gilger, B.C., Stoppini, R., Wilkie, D.A., Clode, A.B., Pinto, N.H., Hempstead, J., Gerding, J. and Salmon, J.H. (2013) Treatment of immune-mediated keratitis in horses with episcleral silicone matrix cyclosporine delivery devices. Vet. Ophthalmol. 17, Suppl. 1, 23-30. 3. Lassaline-Utter, M., Miller, C. and Wotman, K.L. (2014) Eosinophilic keratitis in 46 eyes of 27 horses in the Mid-Atlantic United States (2008– 2012). Vet. Ophthalmol. 17, 311-320. 4. Lassaline-Utter, M., Cutler, T.J., Michau, T.M. and Nunnery, C.M. (2014) Treatment of nonhealing corneal ulcers in 60 horses with diamond burr debridement (2010–2013). Vet. Ophthalmol. 17, Suppl. 1, 76-81. 5. Lassaline-Utter, M., Gemensky-Metzler, A.J., Scherrer, N.M., Stoppini, R., Latimer, C.A., MacLaren, N.E. and Myrna, K.E. (2014) Corneal dystrophy in Friesian horses may represent a variant of pellucid marginal degeneration. Vet. Ophthalmol. 17, Suppl. 1, 186-194.
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