Spectral transmittance of animal intraocular lenses in comparison with the spectral properties of their biological lenses.

PURPOSE: To determine the spectral transmittance of artificial intraocular lenses (IOLs) designed for various species (dog, cat, chinchilla, eagle, tiger) and compare them to the spectral properties of the biological lenses of these species. METHODS: Twenty-seven IOLs were scanned with a spectrophotometer fitted with an integrating sphere. RESULTS: All IOLs transmitted long wavelengths well before cutting off sharply at short wavelengths, with insignificant transmission below ca. 340 nm. In comparison with the IOLs, the biological lenses of the cat, dog, and probably the chinchilla transmitted significantly more short wavelengths. The spectral properties of the biological lenses of eagles and tigers, while uncertain, may be a closer match to the IOLs made for these species. CONCLUSION: It is not known if there are any visual or behavioral consequences for animals caused by a mismatch between the spectral properties of their biological lenses and IOLs. However, following IOL implantation there might be a change in the perceived hue of objects due to the removal of UV wavelengths which form a normal part of the visible spectrum for these species and/or a decrease in sensitivity.

Bilateral phacoemulsification and intraocular lens implantation in a young African lion (Panthera leo).

An 18-month-old intact female lioness (Panthera leo) was referred to the Clinica Veterinaria Roma Sud for evaluation of bilateral cataracts. Phacoemulsification and implantation of +30 diopter intraocular lens (IOL) were performed bilaterally. Seven years after surgery, the IOL remained centrally positioned and the patient had normal activity.

Phaco-émulsification bilatérale et implantation d'une lentille intra-oculaire chez une jeune lionne africaine (Panthera leo) . Une lionne entière âgée de 18 mois (Panthera leo) a été dirigée à la Clinica Veterinaria Roma Sud pour l'évaluation de cataractes bilatérales. La phaco-émulsification et l'implantation de lentilles intraoculaires dioptriques +30 (LID) ont été réalisées bilatéralement. Sept années après la chirurgie, les LID sont demeurées en position centrale et la patiente s'adonnait à des activités normales.(Traduit par Isabelle Vallières).

Intraocular lens power calculation for the equine eye.

BACKGROUND: Phacoemulsification and intraocular lens (IOL) implantation during cataract surgery in horses occur with increasing frequency. To reduce the postoperative refractive error it is necessary to determine the proper IOL power. In the present study retinoscopy, keratometry and ultrasonographic biometry were performed on 98 healthy equine eyes from 49 horses. The refractive state, corneal curvature (keratometry) and the axial location of all optical interfaces (biometry) were measured. The influences of breed, height at the withers, gender and age on values obtained and the comparison between the left and right eye were evaluated statistically. Corresponding IOL power were calculated by use of Binkhorst and Retzlaff theoretical formulas. RESULTS: Mean ± SD refractive state of the horses was + 0.32 ± 0.66 D. Averaged corneal curvature for Haflinger, Friesian, Pony, Shetland pony and Warmblood were 21.30 ± 0.56 D, 20.02 ± 0.60 D, 22.61 ± 1.76 D, 23.77 ± 0.94 D and 20.76 ± 0.88 D, respectively. The estimated postoperative anterior chamber depth (C) was calculated by the formula C = anterior chamber depth (ACD)/0.73. This formula was determined by a different research group. C and axial length of the globe averaged for Haflinger 9.30 ± 0.54 mm and 39.43 ± 1.26 mm, for Friesian 10.12 ± 0.33 mm and 42.23 ± 1.00 mm, for Pony 8.68 ± 0.78 mm and 38.85 ± 3.13 mm, for Shetland pony 8.71 ± 0.81 mm and 37.21 ± 1.50 mm and for Warmblood 9.39 ± 0.51 mm and 40.65 ± 1.30 mm. IOL power was calculated with the Binkhorst and Retzlaff theoretical formulas. Calculated IOL power for the several breeds ranged from 18.03 D to 19.55 D. The mean value across all horses was 18.73 D determined with Binkhorst formula and 18.54 D determined with Retzlaff formula. CONCLUSIONS: Mean result of this study is: an 18.5 D IOL seemed to be the most appropriate to achieve emmetropia after IOL implantation in horses. Cataract surgery without IOL implantation results in hyperopic and visual compromised horses. Retinoscopy, keratometry and ultrasonographic biometry should be performed on every affected horse and postoperative visual outcome should be determined.

Bilateral cataract surgery with intraocular lens implant in a captive western lowland gorilla.

We report a case of bilateral cataract surgery performed in a 21-year-old western lowland gorilla. Phacoemulsification with intraocular lens insertion was performed using standard human surgical equipment. Visual function significantly improved. She subsequently mated and gave birth. Ultimately, cataract surgery enabled the birth of a baby gorilla.

Biometry, keratometry, and calculation of intraocular lens power for the bald eagle (Haliaeetus leucocephalus).

OBJECTIVE: To document intraocular measurements and predict intraocular lens (IOL) power specific to the bald eagle. ANIMALS STUDIED: Eleven adult, captive bald eagles. PROCEDURES: Axial globe length (AGL), anterior chamber depth (ACD), crystalline lens thickness (CLT), and the distance from the cornea to the posterior lens capsule (CPLC) were measured in eight adult bald eagles using B-mode with vector A-mode ultrasound. Keratometry was done on four eagles. Two estimates for postoperative anterior chamber depth (PACD) were obtained from four aphakic eyes from three eagles by measuring from the apex of the anterior cornea to the center of an imaginary line that would connect the remaining edges of the anterior lens capsule across the capsulorhexis (PACD1) and from the apex of the anterior cornea to halfway between the anterior and posterior lens capsule (PACD2). IOL strength was predicted using the Colenbrander, Binkhorst, and Fyodorov theoretical formulas. RESULTS: Mean ± SD biometry for phakic eyes was AGL = 26.57 ± 0.45 mm, ACD = 4.45 ± 0.18 mm, CLT = 5.49 ± 0.14 mm, and CPLC = 10.00 ± 0.33 mm. Mean predicted PACD1 was 6.1 ± 0.66 mm, and PACD2 was 6.4 ± 0.70 mm. Mean horizontal and vertical corneal refractive power was 39.91 ± 0.43 diopters (D) and 40.02 ± 0.08 D, respectively. Calculated IOL power ranged from +16.4 to 17.4 D. CONCLUSIONS: Calculations using ultrasonographic biometry, keratometry, and theoretical IOL formulas suggest that the strength of an IOL necessary to return an aphakic bald eagle to emmetropia is between +16.4 and +17.4 D.

Efficacy of COX-2 inhibitors in controlling inflammation and capsular opacification after phacoemulsification cataract removal.

OBJECTIVE: To evaluate the efficacy of 0.9% bromfenac (Xibrom™) or a celecoxib-impregnated intraocular lens (celecoxib-IOL) compared with 1% prednisolone acetate (PA) in controlling postoperative inflammation and posterior capsule opacification (PCO). ANIMAL STUDIED: Fifty-nine dogs undergoing cataract extraction by phacoemulsification. PROCEDURE: Bilateral patients received bromfenac or celecoxib-IOL plus PA in one eye, and PA in the contralateral eye. Unilateral patients received bromfenac or PA. Complete ophthalmic examination including tonometry, slit-lamp grading of flare and PCO, and digital image acquisition for masked PCO evaluation was performed within 24 h and 1, 4, 12, 24, and 56 weeks following surgery. RESULTS: Celecoxib-IOL/PA-treated eyes had significantly less flare than PA-treated eyes, which had significantly less flare than bromfenac-treated eyes 24 h postoperatively. There was no significant difference in intraocular pressure (IOP) postoperatively, or at 1, 24, or 56 weeks. Celecoxib-IOL/PA-treated eyes had significantly lower IOP measurements than bromfenac and PA-treated eyes at 4 and 12 weeks. There was no significant difference in PCO level between groups using slit-lamp biomicroscopy at any time point. Masked evaluation of digital images revealed significantly less PCO in celecoxib-IOL/PA- vs. bromfenac-treated eyes at 4 weeks, and in bromfenac- vs. PA-treated eyes at 56 weeks. CONCLUSIONS: Eyes receiving celecoxib-IOL/PA had better initial control of inflammation. Bromfenac was equally effective compared with PA in controlling inflammation. There was no association between COX-2 inhibitor administration and ocular hypertension. Celecoxib-IOL/PA-treated eyes showed better initial control of PCO (up to 12 weeks), while eyes receiving bromfenac had better long-term control of PCO (56 weeks).

Retrospective evaluation of phacoemulsification and aspiration in 41 horses (46 eyes): visual outcomes vs. age, intraocular lens, and uveitis status.

OBJECTIVE: To determine the effect of age at the time of surgery, intraocular lens (IOL) placement, and presence of chronic uveitis on visual outcome after phacoemulsification and aspiration (PA) of cataracts in horses. ANIMALS STUDIED: Records of 41 horses (46 eyes) receiving unilateral or bilateral PA. METHODS: Retrospective analysis of horses receiving unilateral or bilateral PA at the NCSU-VTH (35 horses, 39 eyes) and in Northern Italy (six horses, seven eyes) was performed. Visual status at last follow-up was compared to age at the time of surgery, IOL status, and presence of chronic uveitis preoperatively. Seven horses with chronic uveitis also underwent placement of a suprachoroidal cyclosporine implant. Clinical ophthalmic examinations and owner questionnaires were used to evaluate visual status. RESULTS: Twenty-one of 46 eyes (46%) received an IOL and 12 of 46 eyes (26%) had chronic uveitis. Overall, 25 of 46 eyes (54%) were visual at last follow-up (mean 35.1 ± 34.8 months). Age (mean 8.6 ± 7.7 years) was not significantly associated with visual outcome. Fourteen of 21 (67%) pseudophakic eyes and 11 of 25 (44%) aphakic eyes were visual at last follow-up (P = 0.342). Eyes with preoperative chronic uveitis were significantly less likely to be visual (3 of 12 eyes [25%]) than horses without preoperative chronic uveitis (22 of 34 eyes [65%]) (P = 0.023). CONCLUSIONS: Horses with chronic uveitis had significantly less favorable visual outcome after PA. Older age at surgery and IOL use were not associated with poor visual outcome.

Refractive error of canine cataract patients following implantation with three types of intraocular lenses.

OBJECTIVE: To evaluate refractive state outcomes following phacoemulsification and implantation of 3 different intraocular lenses (IOLs). ANIMALS: A prospective, randomized, controlled study was conducted on 43 client-owned dogs undergoing phacoemulsification with IOL implantation. METHODS: Eyes were randomized to receive either an-vision Fo-X (n = 26), an-vision MD8 (18), or I-MED I-LENS (24) IOL. Refraction was measured 1 week, 1 month, and 3 months postoperatively using streak retinoscopy by 2 examiners masked to each other's results. RESULTS: Postoperative refractive outcomes were highly correlated and not significantly different between 2 examiners for all time points (r = 0.97, 0.98, and 1.00; P = .76, .94, and .98, respectively). One week postoperatively, the refractive errors (mean ± SD) for Fo-X, MD8, and I-LENS were -0.14 ± 2.02 diopters (D), 0.97 ± 2.01 D, and 0.15 ± 2.55 D, respectively. One month postoperatively, the refractive errors were 0.35 ± 2.04 D, 0.06 ± 2.41 D, and -0.82 ± 2.20 D, respectively. Three months postoperatively, the refractive errors were -0.16 ± 2.67 D, 1.60 ± 2.99 D, and 0.59 ± 1.51 D, respectively. There were no significant differences in refractive error outcomes between Fo-X, MD8, and I-LENS at 1 week, 1 month, and 3 months postoperatively (P = .16; F(df=2,66)- = 1.89). However, the Fo-X was the only IOL to yield nearly emmetropic outcomes (±0.50 D) at all 3 time points. CLINICAL RELEVANCE: The postoperative refractive states of dogs were not statistically different when comparing 3 types of IOLs at 3 postoperative time points, though the Fo-X was the only IOL to yield nearly emmetropic outcomes at all 3 time points.

Post-operative outcomes in canine eyes receiving a rhexis-fixated prosthetic intra-ocular lens: 30 cases (2014-2020).

OBJECTIVES: To report the outcomes following the insertion of a rhexis-fixated prosthetic intraocular lens (IOL) in dogs undergoing lens removal. MATERIALS AND METHODS: The results are from 30 eyes of 28 dogs, undergoing lendectomy, in which the lens capsule could not accommodate a conventional prosthetic endo-capsular IOL. The reported cases had sustained either spontaneous or traumatic lens capsule rupture, or accidental intra-operative iatrogenic lens capsule disruption, or had required a planned, large, anterior or posterior continuous curvilinear capsulorhexis, all of which precluded insertion of a prosthetic IOL within the lens capsule. An acrylic IOL (XVET; Medicontur) was modified and positioned across the anterior and/or posterior capsulorhexes. RESULTS: Other than haptic luxation in three cases, no complications were seen that were directly attributable to the rhexis-fixated lens. Over a follow-up period from three to 76 months (mean 20.7 months) 26/30 eyes remained visual. Blindness developed in three eyes due to retinal detachment and one eye was enucleated due to regrowth of a ciliary body adenoma. CLINICAL SIGNIFICANCE: Rhexis fixation provided an alternative method to implant a prosthetic IOL when the lens capsule was unable to accommodate a conventional endo-capsular IOL.

Keratometry, biometry, and prediction of intraocular lens power in adult tigers (Panthera tigris).

OBJECTIVE: To calculate the necessary pseudophakic intraocular lens (IOL) power to approximate emmetropia in adult tigers. ANIMALS: 17 clinically normal adult tigers. PROCEDURES: 33 eyes of 17 clinically normal adult tigers underwent routine ophthalmic examination and B-scan ultrasonography while anesthetized for unrelated procedures. Specific ultrasound data (globe measurements and corneal curvature) and estimated postoperative IOL positions were utilized to calculate predicted IOL power by use of Retzlaff and Binkhorst theoretical formulas. Applanation tonometry and refraction were also performed. RESULTS: Mean ± SD axial globe length was 29.36 ± 0.82 mm, preoperative anterior chamber depth was 7.00 ± 0.74 mm, and crystalline lens thickness was 8.72 ± 0.56 mm. Mean net refractive error (n = 33 eyes) was +0.27 ± 0.30 diopters (D). By use of the Retzlaff formula, mean predicted IOL power for the postoperative anterior chamber depth (PACD), PACD - 2 mm, and PACD + 2 mm was 43.72 ± 4.84 D, 37.62 ± 4.19 D, and 51.57 ± 5.72 D, respectively. By use of the Binkhorst equation, these values were 45.11 ± 4.91 D, 38.84 ± 4.25 D, and 53.18 ± 5.81 D, respectively. Mean intraocular pressure for all eyes was 14.7 ± 2.69 mm Hg. CLINICAL RELEVANCE: The calculated tiger IOL was lower than reported values for adult domestic felids. Further studies evaluating actual PACD and pseudophakic refraction would help determine the appropriate IOL power to achieve emmetropia in this species.

A-scan biometry, phacoemulsification, and foldable intraocular lens implantation in a young orangutan (Pongo pygmaeus).

Background: Cataracts are the major cause of visual impairment in animals which can be curable by surgical treatment. Phacoemulsification is the standard technique for cataract treatment that is applied to almost all species with a high success rate. Case Description: A 2-year-old intact female orangutan (Pongo pygmaeus) was presented for the study having bilateral opacity of the lenses, for 2 weeks. Ophthalmic examination revealed mature cataract OU. Ocular biometry measurements using A-scan ultrasonography for appropriate intraocular lens (IOL) refractive power calculation were carried out. Electroretinography was applied to ensure retinal function is intact. The orangutan underwent phacoemulsification OU and +24 diopter IOL implantation OS to restore vision. IOL implantation was not carried out OD because of a posterior capsular tear. Retinoscopy after 3 weeks postoperatively revealed +2.0 diopters OS. The outcome of the cataract surgery was successful during 3 years follow-up. The orangutan lived with other orangutans and was alert with normal behavior such as catching food, climbing trees, and swinging hand over hand from one branch to another. Conclusion: Cataract surgery with phacoemulsification OU and adjusted IOL implantation OD was successful with few complications in this orangutan. Vision was restored with normal behavior, even though an adjusted IOL was inserted in only one eye.

A keratoprosthesis prototype for the dog.

OBJECTIVE: To describe the technique for implantation of a novel keratoprosthesis (KP) prototype and evaluate its application for the treatment of corneal blindness in dogs. ANIMALS STUDIED: Seven dogs, all of them being clinically blind before surgery as a result of severe corneal endothelial disease (5/7) or chronic superficial keratitis (2/7) that were unresponsive to prior therapy. PROCEDURES: A silicone KP was implanted unilaterally, just anterior to Descemet's membrane, after creating a stromal pocket by deep stromal lamellar dissection. RESULTS: Implantation of the KP was accomplished without complication in six of seven operated dogs. In the remaining case, an intra-operative complication (perforation of Descemet's membrane) was associated with extrusion of the KP 8 weeks postoperatively. All operated eyes regained limited vision after surgery. Three to six months after implantation purulent keratitis occurred in all five eyes with endothelial disease, necessitating surgical removal of the KP 6 months postoperatively in 5/7 eyes. CONCLUSIONS: This KP prototype shows promise as a treatment for certain blinding corneal diseases. However, changes in the design of this KP, allowing improved stromal integration, will be necessary before its clinical application can be approved.

Evaluation of 30- and 25-diopter intraocular lens implants in equine eyes after surgical extraction of the lens.

OBJECTIVE: To determine appropriate intraocular lens (IOL) implant strength to approximate emmetropia in horses. SAMPLE POPULATION: 16 enucleated globes and 4 adult horses. PROCEDURES: Lens diameter of 10 enucleated globes was measured. Results were used to determine the appropriate-sized IOL implant for insertion in 6 enucleated globes and 4 eyes of adult horses. Streak retinoscopy and ocular ultrasonography were performed before and after insertion of 30-diopter (D) IOL implants (enucleated globes) and insertion of 25-D IOL implants (adult horses). RESULTS: In enucleated globes, mean +/- SD lens diameter was 20.14 +/- 0.75 mm. Preoperative and postoperative refractive state of enucleated globes with 30-D IOL implants was -0.46 +/- 1.03 D and -2.47 +/- 1.03 D, respectively; preoperative and postoperative difference in refraction was 2.96 +/- 0.84 D. Preoperative anterior chamber (AC) depth, crystalline lens thickness (CLT), and axial globe length (AxL) were 712 +/- 0.82 mm, 11.32 +/- 0.81 mm, and 40.52 +/- 1.26 mm, respectively; postoperative AC depth was 10.76 +/- 1.16 mm. Mean ratio of preoperative to postoperative AC depth was 0.68. In eyes receiving 25-D IOL implants, preoperative and postoperative mean refractive error was 0.08 +/- 0.68 D and -3.94 +/- 1.88 D, respectively. Preoperative AC depth, CLT, and AxL were 6.36 +/- 0.22 mm, 10.92 +/- 1.92 mm, and 38.64 +/- 2.59 mm, respectively. Postoperative AC depth was 8.99 +/- 1.68 mm. Mean ratio of preoperative to postoperative AC depth was 0.73. CONCLUSIONS AND CLINICAL RELEVANCE: Insertion of 30-D (enucleated globes) and 25-D IOL implants (adult horses) resulted in overcorrection of refractive error.

Bilateral phacoemulsification and intraocular lens implantation in a great horned owl.

CASE DESCRIPTION: A great horned owl of estimated age < 1 year that was captured by wildlife rehabilitators was evaluated because of suspected cataracts. CLINICAL FINDINGS: Nuclear and incomplete cortical cataracts were evident in both eyes. Ocular ultrasonography revealed no evidence of retinal detachment, and electroretinography revealed normal retinal function. TREATMENT AND OUTCOME: For visual rehabilitation, cataract surgery was planned and intraocular lens design was determined on the basis of values obtained from the schematic eye, which is a mathematical model representing a normal eye for a species. Cataract surgery and intraocular lens placement were performed in both eyes. After surgery, refraction was within -0.75 diopters in the right eye and -0.25 diopters in the left eye. Visual rehabilitation was evident on the basis of improved tracking and feeding behavior, and the owl was eventually released into the wild. CLINICAL RELEVANCE: In raptors with substantial visual compromise, euthanasia or placement in a teaching facility is a typical outcome because release of such a bird is unacceptable. Successful intraocular lens implantation for visual rehabilitation and successful release into the wild are achievable.

Scanning electron microscopy of intraocular lenses that had been implanted in dogs.

Scanning electron microscopy was used to evaluate changes on the surfaces of polymethylmethacrylate (PMMA), silicone, and polyhydroxyethylmethacrylate (HEMA) intraocular lenses (IOL) that had been implanted in the anterior chambers of the right eyes of 15 dogs. Five dogs received PMMA IOL; 5 dogs received silicone IOL; and 5 dogs received HEMA IOL. Twenty-eight days after surgery, the IOL were removed and processed for scanning electron microscopy. Nonimplanted IOL of each type were processed identically for comparison. Implanted PMMA IOL had significantly more debris and macrophages on their surfaces than did silicone IOL or HEMA IOL. Silicone IOL had significantly less fibrin deposition than did PMMA or HEMA IOL. Silicone IOL had surface defects attributable to handling by surgical instruments. Implanted HEMA IOL had multiple pits that appeared to be caused by biodegradation.

Clinicopathologic findings after experimental implantation of synthetic intraocular lenses in dogs.

Clinical findings indicate that canine eyes tolerate implantation of polymethylmethacrylate (PMMA) intraocular lenses (IOL) well, although inflammation and ocular damage attributable to the implants is not known. The use of silicone or polyhydroxyethylmethacrylate (HEMA) IOL has not been reported in dogs. In this study, 15 conditioned, mixed-breed dogs were allotted to 3 groups: 5 received PMMA IOL; 5 received silicone IOL; and 5 received HEMA IOL. The IOL optic was inserted into the anterior chamber of the right eye and anchored to the cornea. An identical surgical procedure was done on the left eye, except that no lens optic was inserted. Clinical examination and measurement of corneal thickness were done immediately prior to and after surgery. Aqueous humor samples were collected at the time of surgery and 28 days after surgery. Only mild and transient inflammation was observed in IOL-implanted eyes. On several postoperative days, it was found that PMMA IOL induced significantly greater corneal thickness, aqueous flare, anterior uveal irritation, and corneal edema than did other IOL. Significantly more anterior uveal irritation and increased aqueous humor protein concentration was observed with HEMA IOL than with PMMA or silicone IOL. Silicone IOL induced significantly less fibrin deposition than did PMMA or HEMA IOL.

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)

Use of biometry and keratometry for determining optimal power for intraocular lens implants in dogs.

Axial length and corneal curvature were determined by use of A-scan ultrasonography and keratometry on both eyes of dogs of various breeds, sizes, and ages. Mean axial length was 20.43 +/- 1.48 mm; axial length was not related to age or sex, but was significantly greater (P = 0.047) in dogs of larger breeds. Mean corneal curvature was 39.94 +/- 2.61 diopters. Dogs of large breeds had significantly (P less than 0.001) flatter corneas. Mild, roughly symmetric astigmatism was detected in a majority of dogs. Use of mean values in a theoretic artificial intraocular lens power equation suggests that aphakic dogs require an implant of approximately 40 diopters to achieve emmetropia.

Keratometry, ultrasonic biometry, and prediction of intraocular lens power in the feline eye.

OBJECTIVE: To determine ocular dimensions (using A-scan ultrasound biometry) and corneal curvature (using keratometry) in the feline eye and to calculate the appropriate dioptric power for a prototype posterior chamber intraocular lens (IOL) necessary to achieve emmetropia in the eyes of cats undergoing lens extraction. ANIMALS: 25 clinically normal adult mixed-breed cats and 10 eyes from 10 clinically normal adult mixed-breed cat cadavers. PROCEDURE: A-scan ultrasonic biometry was performed on both eyes of each live cat. Cats were tranquilized, and keratometry was performed on each eye. Biometry was performed on the cadaver eyes. Five of the cadaver eyes had the lens extracted and an IOL, designed for use in dogs, was implanted. Biometry was repeated to estimate postoperative IOL position. Using 3 theoretical IOL formulas, data from biometry, keratometry, and postoperative IOL position were used to predict IOL strength required to achieve emmetropia after lens extraction in cats. RESULTS: Mean axial length of eyes in live cats was 20.91 +/- 0.53 mm. Mean preoperative anterior chamber depth (ACD) was 5.07 +/- 0.36 mm, and mean lens thickness was 7.77 +/- 0.23 mm. Predicted postoperative ACD was calculated to be 10.84 mm. Measured postoperative ACD in the 5 cadaver eyes was 8.28 mm. Required IOL strength calculated, using the predicted postoperative ACD, was 73 to 76 diopters. The required IOL strength calculated, using the measured postoperative ACD, was 53 to 55 diopters. CONCLUSIONS AND CLINICAL RELEVANCE: An IOL of substantially higher diopter strength than that needed in dogs is required to achieve emmetropia after lens extraction in average cats; an IOL strength of approximately 53 to 55 diopters will likely be required.

Implantation of a foldable intraocular lens in dogs.

A 1-piece, tripod-shaped, acrylic intraocular lens was implanted in the posterior chamber after phacoemulsification to remove cataracts in 20 eyes of 16 dogs. Biomicroscopy and intraocular pressure measurements were performed at 1, 8, 30, and 90 days after surgery; retinoscopy was performed at day 30. Complications were not encountered during implantation of the lens. All dogs had mild ocular inflammation characterized predominantly by aqueous flare and mild corneal edema at day 1, which resolved completely by day 8; 3 eyes had mild hyphema at day 1, which resolved by day 8. Three eyes developed fibrin in the anterior chamber, which resolved by day 30. Two eyes developed distorted pupils caused by adherence of vitreous humor or fibrin to the incision site. Postoperative intraocular pressure ranged from 7 to 21 mm Hg. Implantation resulted in 9 emmotropic eyes, 5 myopic eyes, and 6 hyperopic eyes. Maintenance of central lens position was excellent in 19 eyes; in 1 eyes, a disclocated superior haptic at day 2 was easily repositioned.