Unilateral phacoemulsification in a captive African elephant (Loxodonta africana).

Background: The following case reports describe the clinical presentation, surgical protocol, post-operative care, and long-term follow-up of an African elephant (Loxodonta Africana) presenting with a unilateral cataract. Case description: A 42-year-old female African elephant presented for the assessment of ocular discomfort and visual deterioration in the left eye. Pre-surgical treatment included topical anti-inflammatory medication for 20 days prior to surgery. On the day of surgery, following anesthetic induction, a two-handed phacoemulsification technique was performed in the left eye. She was left aphakic post-operatively. Nine days post-operatively, the patient had an intact menace response, dazzle reflex, and direct pupillary light reflex. Fundoscopy at that stage was unremarkable. Follow-up information was available for 5 years, from the time of surgery to the present day. Conclusion: Despite remaining aphakic, this case presents a successful visual outcome. To the best of the authors' knowledge, there is no other published report of phacoemulsification in a captive elephant.

Refractive state following retinal reattachment and silicone oil tamponade in dogs.

OBJECTIVE: To evaluate the refractive error induced by intraocular administration of silicone oil (SiO) in dogs. ANIMALS: 47 client-owned dogs evaluated for blindness secondary to retinal detachment. PROCEDURES: -3-port pars plana vitrectomy with perfluoro-octane and SiO exchange (1,000- or 5,000-centistoke SiO) was performed in 1 or both eyes for all dogs (n = 63 eyes), depending on which eye or eyes were affected. Dogs were normotensive, had complete oil filling of the eyes, and were examined in a standing position for retinoscopic examination of both eyes (including healthy eyes). RESULTS: The mean refractive error for SiO-filled phakic and pseudophakic eyes was 2.67 and 3.24 D, respectively. The mean refractive error for SiO-filled aphakic eyes was 6.50 D. Dogs in which 5,000-centistoke SiO was used had consistently greater positive refractive errors (mean, 3.45 D), compared with dogs in which 1,000-centistoke SiO was used (mean, 2.10 D); however, the difference was nonsignificant. There was no significant linear relationship between refractive error and the number of days between surgery and retinoscopy. CONCLUSIONS AND CLINICAL RELEVANCE: Hyperopia was observed in all dogs that underwent SiO tamponade, regardless of lens status (phakic, pseudophakic, or aphakic). Aphakic eyes underwent a myopic shift when filled with SiO. Pseudophakic eyes appeared to be more hyperopic than phakic eyes when filled with SiO; however, additional investigation is needed to confirm the study findings.

Aphakic hydrogel contact lens fitting on a monocular canine: a case report.

BACKGROUND: Though plano bandage contact lenses used for therapeutic purposes are not uncommon for dogs, no literature regarding contact lenses to correct aphakic canines currently exists. CASE REPORT: Oliver, a 7-year-old terrier mix, was aphakic in his left eye and essentially blind in his right eye as the result of a large retinal detachment. Surgical complications and endothelium damage contraindicated an intraocular lens implant in his left eye. While co-managed with his veterinary ophthalmologist, Oliver was prescribed an aphakic hydrogel contact lens to improve his monocular vision. CONCLUSION: Oliver was successful (by clinical criteria) with his contact lens. Although it is difficult to quantify his vision without a visual evoked potential, Oliver appeared more attentive and confident with the contact lens. This case report demonstrates a successful canine aphakic contact lens fit through the efforts of his owners, co-managing veterinary ophthalmologist, and optometrist.

Effect of optical defocus on visual acuity in dogs.

OBJECTIVE: To determine the effect of optical defocus (such as what develops in spontaneous myopia and subsequent to cataract extraction) on visual acuity in dogs. ANIMALS: 3 young adult male Beagles. PROCEDURE: The effect of optical defocus on visual acuity was determined by sweep visual evoked potential, using a within-subjects/repeated measures design in which each dog served as its own control. Dogs were positioned so that the eye being tested was 60 cm in front of the video display, and the target was centered on the area centralis. To create ametropia relative to the video screen, a series of concave and convex spherical lenses were placed 1 cm in front of the eye, and sweep visual evoked potential acuities were obtained. RESULTS: Maximal acuity was 7.0 to 9.5 cycles/degree. Defocusing by 2.0 diopters reduces Beagle grating acuity approximately 1 octave. Mimicking aphakia resulted in a marked depression of acuity to 0.7 cycles/degree or less. CONCLUSIONS: Even mild degrees of ametropia have appreciable impact on the resolving power of the canine visual system. CLINICAL RELEVANCE: Spontaneous myopia is encountered in dogs and may be associated with impaired visual performance attributable to a reduction in visual acuity. Previous reports indicate the possibility of myopia in dogs to have a heritable component. On the basis of our results, refractive correction of aphakia is advisable, and refractive screening of dogs with demanding visual tasks (eg, service dogs, field-trial Labrador Retrievers) is recommended.

Refractive state of aphakic and pseudophakic eyes of dogs.

Streak retinoscopy was performed by 5 ophthalmologists on 256 eyes (191 dogs) to determine their postoperative refractive state after cataract extraction. Aphakic and pseudophakic eyes that had been implanted with 1 of 5 intraocular lenses (IOL) with dioptric powers ranging from +14.5 to +38 diopters (D) were studied. By use of ANOVA, breed and body type of dog and individual performing refraction were found to have no detectable effect on final refractive state. Mean refractive state of aphakic eyes was +14.4 +/- 2.10 D. Mean refractive state for different IOL powers was as follows: +14.5 D IOL = +11.54 +/- 1.18 D (n = 13); +30 D IOL = +5.15 +/- 1.18 D (n = 105); +34.0 D IOL = +3.5 D (n = 1); +36 D IOL = +2.34 +/- 0.73 D 9 (n = 61); and +38 D IOL = +1.41 +/- 0.56 D (n = 28). Residual hyperopia ranged from +0.5 D to +2.5 D with +38 D IOL, and no eyes were myopic (overcorrected) by use of any of the IOL studied. Linear regression analysis of refractive state on IOL power for all dogs predicted that dioptric strength of +41.53 D was necessary to best approximate emmetropia for the population as a whole. Body type of the dog had only slight effect (< 1.0 D) on predicted optimal IOL power. Further linear regression analysis of the 7 breeds studied predicted variations from +39.62 to +43.14 D in IOL powers necessary to approximate emmetropia.(ABSTRACT TRUNCATED AT 250 WORDS)

Follow-up report of a case of surgical aphakia with an analysis of equine visual function.

More work is necessary to establish corneal dimensions and retinal structure and neural organisation in the equine eye. This paper reports a case of surgical management of bilateral cataracts in a pony and the results of a survey of refractive error in normal horses. Aspects of accommodation are discussed. It is suggested that a difference in retinal receptor organisation between horse and human eyes could explain the good visual performance of the aphakic pony; and that the degree of blurring of vision in the aphakic situation is less, both in absolute terms and in proportion to presumed normal levels of vision, in the horse than in man. It would not seem necessary to consider intra-ocular implants for horses at this stage. The authors feel it is unwise to extrapolate too freely from human data. More information is needed on the optics and retinal topography of many species, particularly horses and dogs, before routine implant surgery on eyes is undertaken.