The ECVO Hereditary Eye Disease Scheme
Version: 2009, June, 10, Accepted by the Executive Committee 2009-09-09.
1. The Scheme
The ECVO has an Hereditary Eye Disease Scheme (further referred to as the Scheme) as mentioned in the Bylaws of the ECVO, Article 4.9, to be used for the diagnosis and the control of Presumed Inherited Eye Diseases (PIED) in animals.
The main purposes of the Scheme are to diagnose and control PIED which are either disabling, or painful or disturbing to the wellbeing of animals, or necessitate surgical intervention or lifelong medication.
The Scheme provides definitions, guidelines, recommendations and information concerning PIED. Additional information is given in the appendixes, the ECVO-procedure notes and the illustrations on the website (www.ecvo.org/public/index.htm).
The Scheme also has to guarantee that:
- all examiners are able to recognize, differentiate the relevant and irrelevant clinical signs of PIED and establish their significance;
- rules and guidelines are provided for the examination and authentication of specifically trained veterinary European eye specialists (Diplomates) and specifically trained veterinarians (European Eye Scheme Examiners or ESE) to give a service for dog owners, breeders, the breed and kennel clubs and the public in general, by providing an appropriate level of expertise for the diagnosis of PIED.
The Scheme includes a general examination of the eye and its adnexa.
A certificate of the eye examination is issued in respect of PIED. The certificate is valid for one year from the date of examination and it is recommended that the animal is examined annually. If the examination findings are inconclusive it might be necessary for the animal to be re-examined sooner e.g. within 6 months, which shall be stated on the form.
Litter screening can also be performed under the Scheme.
2. Organization and panels
The Practising ECVO Diplomates and the national ESE (if present) shall form a National Panel in countries where this has been agreed and the necessary rules and regulations set. These rules and regulations shall not contain any provision which violates the Constitution or Bylaws of the ECVO or the rules of the Scheme.
The National Panel shall have a Board, elected by its membership. The Board shall consider all business and policies pertaining to the affairs of the National Panel. In the absence of a National Panel, the Eye Disease (HED)Committee of the ECVO will act in its place.
For countries where an established National Panel has been in existence for more than 5 years, on the advice of the Hereditary Eye Disease (HED) Committee, this Panel can apply to the Executive Committee of the ECVO for membership of the ECVO Scheme.
The National Panel must meet at least once per year to discuss the Scheme and its operation.
Panellists approved by the ECVO to perform examinations under the Scheme are:
- Practising Diplomates of the ECVO;
- Eye Scheme Examiners, in countries where this has been agreed, being veterinarians, specifically trained and examined. This contract may be extended ad infinitum by the ECVO.
Training and examination of Eye Scheme Examiners
Before training commences, the candidate must confirm normal stereoscopic, color vision (binocular, corrected for refractive errors).
Before ESE-candidates can qualify to sit the ESE examination for the scheme, the candidate:
- must document the examination of at least 500 dogs under supervision by two different panel members recognized by the ECVO. At least 50 of these dogs shall be examined under supervision by a practicing ECVO Diplomate. Up to 200 dogs can be examined under supervision by an ACVO Diplomate. A record shall be kept for all animals examined.
- must document the examination of at least 100 cats. At least 10 of these cats shall be examined under supervision by a practicing ECVO Diplomate or ESE. A record shall be kept for all animals examined.
- must document the examination of certain specific breeds and diseases, in the minimum numbers as defined in Appendix A.
- must document their participation in at least 3 ECVO recognized continuing education courses in ophthalmology (total duration of 3 days or more) which have included diseases of the anterior and posterior segments, and basic genetic principles.
- should be trained in direct and indirect ophthalmoscopy, slit-lamp biomicroscopy and gonioscopy.
- should have studied literature concerning PIED in animals as defined in the literature list in Appendix B.
An examination is necessary to qualify as an ECVO-Eye Scheme Examiner (ESE). This examination will be coordinated and directed by at least one member of the HED-Committee of the ECVO and by one member of the Examination Committee or the Executive Committee of the ECVO. If no active members are available, a former member of one of these committees, or, as a second person, a Diplomate of the ECVO can be appointed by the Executive Committee. If the second Diplomate is not a present or a past member of one of the committees mentioned, the two Diplomates should be from different countries.
The examination will normally consist of:
- a written section of multiple choice (50; 3 min/question) and/or essay questions on presumed inherited (related) eye diseases;
- a combined practical and written section (40; 2 min/question) based on images of presumed inherited (related) eye diseases;
- a final section which will consist of live case evaluation (at least 5 cases) with oral examination. This final part can only be taken once the candidate has passed the first two parts of the examination.
Requirements for maintaining Panellist status.
The Board of the National Panel is responsible for the compliance of their Panellists with the following rules. If no National Panel exists then the HED-Committee of the ECVO will act in its place.
- The Panellist is obliged to work under the rules of both the ECVO Scheme and the National Scheme. If any work is conducted in serious violation of these rules, the Board of the National Panel is entitled to expel the person from the panel.
- If there is proof of continuing misdiagnosis by a Panellist, this person must be re-examined, or the Board of the National Panel is entitled to expel the person from the Panel. If expelled, the former Panellist cannot continue to issue ECVO certificates, nor issue documents which imply the same status as the ECVO certificate.
- The Panellist shall complete the minimum number of examinations for the Scheme of 100 per year or 300 per 3 years; if less, re-qualification is necessary. Recently qualified Panellists are exempted from this requirement during their first full year as Panellist.
- The Panellist shall attend the annual meeting of the National Panel. If absent from 3 consecutive meetings, without dispensation of the Board, the Panellist can be expelled from the National Panel. If the Panels hold other related meetings (e.g. arbitrary or appeal cases), the Panellist shall attend these meetings. If absent from more than half of these meetings over 3 consecutive years, without dispensation of the Board, the Panellist can be expelled from the National Panel.
- The Panellist shall attend at the least one annual scientific meeting of the ECVO during 3 years. If absent without dispensation of the Board of the National Panel (or the HED-Committee) the person can be expelled as ECVO-Panellist by the Board of the National Panel (or the HED-Committee of the ECVO).
- The Panellist must possess good eyesight with a minimum visual acuity of 0.7 (corrected for refractive errors). A certificate of visual acuity is to be presented to the Board of the National Panel or the HED-Committee of the ECVO every 5 years until the age of 70, and after that age, every second year.
In special circumstances the Board of the National Panel, or if there is no Panel, the HED-Committee of the ECVO may grant a Panellist exemption from the minimum number of eye examinations and attendance of meetings.
A decision to expel a Panellist from the Panel is taken by the Board of the National Panel. The Panellist has the right to appeal to the entire National Panel at the next annual meeting or alternatively to the HED-Committee of the ECVO.
A Panellist who is expelled from the panel may be allowed to sit a new examination in order to re-qualify. The decision is taken by the Board of the National Panel (or the HED-Committee of the ECVO), who will also decide the extent of the examination.
4. Arrangements for the Eye Examination
Eye Examination for individual animals:
The owner of an animal can approach his or her own veterinarian and ask for a referral for the animal to be examined under the Scheme or the Panellist can be approached directly by the owner.
As for individual animals.
Group Eye Examination
A society or club can arrange for a group of animals to be examined, e.g. at a show.
5. Procedure for the Eye Examination
Examination for the Scheme is according to the ECVO protocol. Partial or preliminary examinations are not permitted. Gonioscopy may be completed as an additional examination.
A certificate is issued upon completion of the examination.
The following documents should be available before the examination:
- the animal's registration document or other identifying document ;
- any previous eye certification.
The owner and/or his agent will present the animal for examination at the appropriate time together with the documents referred to above. If the animal's registration or other identifying documents are not available, then examination can be undertaken but the Certificate will not be issued until the Panellist has been provided with the relevant documentation.
Prior to the examination, the owner or his agent must sign the completed first part of the Certificate, verifying that the details given in that section are correct. (Details included in this section relate to the animal being submitted for examination and the date of the last eye examination). The owner should be aware that the results of the examination will be available in the public domain. The Panellist, or the Society or club arranging a Group Eye Examination will check the tattoo or microchip.
Certificates for the Scheme can only be issued for animals which can be identified permanently (e.g. by tattoo, microchip or otherwise).
The certificate should record details of the site and type of any lesion present. Any information deemed appropriate by the Panellist should be included in the comments section. Then, subject to the registration documents being available as stated above, the Certificate should be signed and issued by the Panellist and distributed according to the instructions of the National Scheme. In general this distribution will involve:
- top copy (white; preferably plus a photocopy of the animal's registration document) will be sent as soon as possible (within one month of the date of examination) to the appropriate Kennel club or National Scheme authority;
- one copy (yellow) will be sent as soon as possible (within one month of the date of examination) to the appropriate Breed club (if applicable);
- one copy (pink) will be retained by the Panellist as his record;
- one copy (white) will be given to the owner or agent.
- one copy (blue) will be either sent to the referring veterinarian or given to the owner to hand over to the referring veterinarian;
All animals presented under the Scheme will have a general examination of the eye and adnexa and this will include the necessary use of a mydriatic.
For those breeds specifically examined for pectinate ligament abnormality, persistent pupillary membrane or iris coloboma, examination before the use of a mydriatic is essential.
The minimum equipment to be used for the examination is a slit-lamp biomicroscope (at least 10 x magnification) and a binocular indirect ophthalmoscope. The use of other equipment is optional.
If electroretinography is used as an early diagnostic test for hereditary retinal degeneration, the following standardised protocol of the ECVO has to be followed: Narfstrom K, Ekesten B, Rosolen SG, Spiess BM, Percicot CL, Ofri R; Committee for a Harmonized ERG Protocol,
Details of all lesions and conditions found at the time of examination, whether relating to hereditary eye disease or not, should be recorded in the descriptive comments section in the middle of the Certificate using drawings and/or written remarks.
The box "Unaffected" for pectinate ligament abnormality/glaucoma (primary) in the results section of the Certificate may only be ticked if gonioscopy has been completed bilaterally and there is no sign of pectinate ligament abnormality present at the time of examination. Gonioscopy is not included in the basic ophthalmoscopic examination. The result of the gonioscopy shall be recorded on the Certificate. It is recommended that gonioscopy is done in all breeds in which primary glaucoma is known to occur.
Recommendation: Barkan, Franklin or Koeppe gonioscopy lenses should be used.
If any additional (or alternative) method of examination is used, the Certificate shall only be valid if accompanied by an additional document specifying the method(s) used.
Arrangement can be made with a member of the Panel to have litters examined for the specific congenital PIED known to occur in certain breeds. This is applicable only in litters younger than 12 weeks, following tattooing or microchipping. A registration document may not be available, but any certification can be completed using the details of the dam and sire, together with the date of birth of the puppies and when applicable, the tattoo/microchip numbers. If a specific Litter Screening Form is available, this may be used until the age of the litter of 12 weeks. Thereafter separate certificates for every littermate shall be used. The distribution of copies is the same as for the Certificate of Eye Examination.
6. Examination outside the Scheme
If a patient is examined outside the Scheme by an ECVO Panellist and a PIED is recognized, the Panellist is strongly recommended to issue an ECVO Certificate. It is recommended that the cost of such a certificate is met by the National Registry or Kennel Club.
If no certificate is issued, the Panellist is obliged to keep record of such cases and report the number of cases per disease to the ECVO HED-Committee annually (due December 31).
7. Publication of Results
The name of the registered animal examined under the Scheme, the registration and identification numbers, together with the results of the examination, will be sent to the appropriate National registration office and if sanctioned by the Members of the national Kennel Club and the particular Breed Club, to the national Kennel Club and Breed Club.
If an animal is exported, all results of former examinations shall be sent together with the pedigree to the importing country.
If an animal is transferred from one registry to an other, the “exporting” registry provides all results of former examinations on presumed inherited disease and the “importing” registry is obliged to include them.
8. Conflicting results of eye examinations conducted on the same animal:
In the event that the results of two eye examinations of the same animal conflict, the most adverse judgment is valid until the animal is examined by the National Panel or Chief Panellist, whose decision will be final
When an animal is found “affected” for a presumed inherited eye disease (PIED) by a panel member or the local appeals authority and the animal is transferred to an other registry, the result “affected” for this PIED will not be changed, unless the animal has been re-examined by the appeals authority of the new registry. This with the exception of conditions which may be changed artificially; theses results are definitive (e.g. distichiasis, entropion, etc.)
9. "Suspicious" cases
It is recommended that “suspicious” cases, after the prescribed period, are re-examined by the National Panel or Chief Panellist, whose decision will be final.
Alternatively, re-examination of cases previously found "suspicious" can be done by the first examiner or another Panellist.
In the event that the first examiner or another Panellist finds the previously judged "suspicious" animal "affected", this last judgment is valid until the animal is examined by the National Panel or Chief Panellist, whose decision will be final.
In the event that the first examiner or another Panellist finds the previously judged "suspicious" animal "unaffected", the "suspicious" judgment remains valid until the animal is examined by the National Panel or the Chief Panellist, whose decision will be final. Alternatively, after a follow up period of at least 1 year, the first examiner plus another examiner, or after 2 years (or 1 year with previous dispensation of the Board of the national panel), the first examiner alone can judge the previously “suspicious” animal as “unaffected”.
10. Appeals Procedure
There shall be either National Panel meetings (at least 2 times/year), or a chief panellist (an ECVO-diplomate appointed by the National Panel) available for the evaluation of appeal cases.
An owner has the right to appeal the results of an eye examination and the procedure is as follows:
Any appeal against the result of an eye examination must be lodged in writing with the national Panel or national registry within 60 days of the examination being conducted, except in case of choroidal hypoplasia and retinal dysplasia. Here re-examination must be completed before 12 weeks of age or within 5 days if the puppy was aged 12 weeks at the time of the initial examination.
The owner will take the animal and the Certificate issued by the first Panellist for examination by another Panellist.
- In the event of the second Panellist agreeing with the first Panellist the appeal will be deemed to have failed and the second Panellist will inform the National Eye Panel accordingly. Further appeal to a National Panel Meeting or to the Chief Panellist is possible.
- In the event of the second Panellist disagreeing with the first Panellist then the matter shall be referred to the National Eye Panel Meeting or the Chief Panellist for further examination. This decision will be final.
11. Further details
Further details of the Scheme are issued by the HED-Committee of the ECVO. Unclear rules or regulations, new disease problems etc. are to be reported by the Panellist to the HED-Committee. The HED-Committee, on the advice of the Advisory Committee, will provide further details and inform the Panellists by Procedure notes at least every two years.
The following list of diseases/variations should have been seen and recorded (at the discretion of the national panel)
Persistent pupillary membrane
Perinuclear ring (cortex)
Nuclear fibrillar opacities
Pigment on anterior lens capsule
Cataract, posterior cortical, including posterior polar
Cataract, anterior cortical / subcapsular
Cataract, anterior suture lines
Cataract, other (e.g. suture tips, equatorial)
Lens (sub)luxation (can be seen without supervision)
Persistent tunica vasculosa lentis posterior
PHTVL/PHPV Grade 1 (at least 1 in puppy ≤ 10weeks)
Complete retinal detachment
Partial retinal detachment
PRA early stage
PRA late stage
Glaucoma (can be seen without supervision)
Of the 500 dogs examined at least 50 should be collie/Shetland sheepdog puppies ≤ 10 weeks of age. Of these, at least 10 should be merle dogs.
List of relevant literature
Anatomy, embryology and histology, physiology, immunology, pharmacology and vision
Gelatt Veterinary Ophthalmology 4th ed. 2007 Blackwell Synergy
Pathology of domestic animals (Jubb & Kennedy) , 4th ed., 3 volumes, London Academic Press, 1993.(chapters on eye and related structures)
DeLahunta & Glass: Veterinary neuroanatomy and clinical neurology 3rd Ed. Saunders/Elsevier 2009 (chapters related to the eye and adnexa and vision)
- Gelatt Veterinary Ophthalmology 4th ed. 2007 Blackwell Synergy
- Slatter’s Fundamentals of Veterinary Ophthalmology (Maggs, Milelr & Ofri), 4th ed. , Saunders/Elsevier, 2009
- Ophthalmology for the veterinary practitioner (Stades F,Wyman, Boevé, Neumann, Spiess) , Schlütersche Hannover, 2007
- Small animal ophthalmology, a problem oriented approach (Peiffer R. & Peterson – Jones S.), 2009, 4th ed., Saunders/Elsevier.
- Canine ophthalmology: an atlas and text (Barnett KC ,Heinrich C & Samson J), 2002, WB Saunders.
- Manual of small animal ophthalmology (Peterson – Jones S. et al.), BSAVA Publications Cheltenham, 2002.
- Feline ophthalmology, an atlas and text ( Barnett KC & Crispin SM), WB Saunders, 1998
- Inherited eye diseases in purebred dogs (Rubin L) Williams & Wilkins, 1989.
- ACVO Genetics Committee : Ocular disorders proven or suspected to be hereditary in dogs , Vet.Pract.Publishing Cy ed
- http:// www.optigen.com: testing for inherited eye diseases of purebred dogs
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- Aguirre, G.D., and Acland, G.M.: Variations in retinal degeneration phenotype inherited at the prcd. locus. Exp. Eye. Res. 46:663,1988.
- Aguirre, G.D., and Rubin, L.F.: Progressive retinal atrophy (rod dysplasia) in the Norwegian elkhound: J. Am. Vet. Med. Assoc., 158:208,1971.
- Aguirre, GD; Rubin, LF; Pathology of hemeralopia in the Alaskan Malamute dog. Invest Ophthalmol1974;13, 231-235.
- Albert, D.M., et al: Canine herpes‑induced retinal dysplasia and associated ocular anomalies. Invest. Ophthalmol. Vis. Sci., 15:267, 1976.
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- Bedford PGC. Collie eye anomaly in the United Kingdom Vet Rec 1982. 111: 263-70.
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- Ekesten B, Bjerkås E, Kongsengen K, Narfström K. Primary glaucoma in the Norwegian elkhound. Vet Comp Ophthalmol 1997; 7: 14-18.
- Foster SJ, Curtis R, Barnett KC. Primary lens luxation in the Border Collie. J Small Anim Pract 1986; 27: 1-6.
- Gelatt, K.N. et al.: Animal models for inherited cataracts: A review. Curr. Eye Res., 3(5):765‑778, 1984.
- Grahn BH, Cullen CL Retinopathy of Great Pyrenees dogs: fluorescein angiography, light microscopy and transmitting and scanning electron microscopy. Vet Ophth 2001 4: 191-199.
- Holle DM, Stankovics ME, Sarna CS, Aguirre GD. The geographic form of retinal dysplasia is not always a congenital abnormality. Vet Ophth 1999; 2: 61-66.
- Lazarus JA, Pickett JP, Champagne ES. Primary lens luxation in the chinese Shar Pei: Clinical and hereditary characteristics. Vet Ophthalmol 1998; 1: 101-107.
- Leon A, Curtis R, Barnett KC. Hereditary persistent hyperplastic primary vitreous in the Staffordshire bull terrier. J Am Anim Hosp Assoc 1986; 22: 765-74.
- Leppanen M, Mårtenson J, Mäki K. Results of ophthalmologic screening examinations of German Pinschers in Finland – a retrospective study. Vet Ophth 2001; 4: 165-169.
- Long, SE; Crispin, SM. Inheritance of multifocal retinal dysplasia in the golden retriever in the UK. Vet Rec 1999; 145: 702-204
- MacMillan, AD; Lipton, DE. Heritability of multifocal retinal dysplasia in American cocker spaniels. J Am Vet Med Assoc 1978; 172: 568-572.
- Martin CL, Wyman M. Glaucoma in the basset hound. Journal of the American Veterinary Medical Association 1968; 153: 1320-1327.
- Martin, C.L., and Chambreau, T.: Cataract production in experimentally orphaned puppies fed a commercial replacement for bitch's milk. J. Am. Anim. Hosp. Assoc., 18:115, 1982.
- Martin, C.L.: Development of pectinate ligament structure of the dog: Study by scanning electron microscopy. Am. J. Vet. Res., 35:1433, 1974.
- Martin, C.L.: Gonioscopy and anatomical correlations of the drainage angle of the dog. J. Small Anim. Prac., 10:171, 1969.
- Martin, C.L.: Scanning electron microscopic examination of selected canine iridocorneal angle abnormalities. J. Am. Anim. Hosp. Assoc., 11:300, 1975.
- Martin, C.L.: Slit lamp examination of the normal canine anterior ocular segment. Part I: Introduction and technique. J. Small Anim. Pract., 10:143, 1969.
- Martin, C.L.: Slit lamp examination of the normal canine anterior ocular segment. Part II: Description. J. Small Anim. Pract., 10:151, 1969.
- Martin, C.L.: Slit lamp examination of the normal canine anterior ocular segment. Part III: Description and summary. J. Small Anim. Pract. 10:163, 1969.
- Martin, C.L.: The normal canine iridocorneal angle as viewed with the scanning electron microscope. J. Am. Anim. Hosp. Assoc., 11:180, 1975.
- McLellan GJ, Elks R, Lybaert P, Watte C, Moore DL, Bedford PG. (2002) Vitamin E deficiency in dogs with retinal pigment epithelial dystrophy. Vet Rec 151(22):663-7
- Narfstrom, K.: Progressive retinal atrophy in the Abyssinian cat: Clinical characteristics. Invest. Ophthalmol. Vis. Sci., 26:193, 1985.
- Narfström K, Dubielzig R. Posterior lenticonus, cataracts and microphthalmia; congenital ocular defects in the cavalier king charles spaniel. J Small Anim Pract 1984; 25: 669-77.
- Narfström K. Cataract in the West Highland white terrier. J Small Anim Pract 1981; 22: 467-71.
- Narfström K, Wrigstad A, Ekesten B, Nilsson SEG. Hereditary retinal dystrophy in the briard dog: Clinical and hereditary characteristics. Prog Vet Comp Ophthalmol 1994; 4: 85-92.
- Narfstrom K, Ekesten B, Rosolen SG, Spiess BM, Percicot CL, Ofri R; Committee for a Harmonized ERG Protocol, European College of Veterinary Ophthalmology. Guidelines for clinical electroretinography in the dog. Doc Ophthalmol. 2002; 105: 83-92.
- Parshall CJ, Wyman M, Nitroy S et al. Photoreceptor dysplasia: An inherited progressive retinal dystrophy of miniature schnauzer dogs. Prog Vet Comp Ophthalmol 1991; 1: 187-203.
- Petersen-Jones SM, Clemens PJM, Barnett KC et al. Incidence of the gene mutation causal for rod-cone dysplasia type 1 in Irish setters in the UK. J Small Anim Pract 1995; 36: 310-14.
- Petersen-Jones S.M. Abnormal ocular pigment deposition associated with glaucoma in the Cairn terrier. J Small Anim Pract 1991; 32: 19-22.
- Read RA, Wood JLN, Lakhani KH. Pectinate ligament dysplasia (PLD) and glaucoma in flat coated retrievers. I. Objectives, technique and results of a PLD study. Veterinary Ophthalmology 1998; 1: 85-90.
- Roberts, S.R., and Dellaporta, A., and Winter, F.C.: The collie ectasia syndrome. Pathology of the eyes of young and adult dogs. Am. J. Ophthalmol., 62:728, 1966.
- Roberts, S.R., Dellaporta, A., and Winter, F.C.: The collie ectasia syndrome. Pathologic alterations of the eyes of pups one to fourteen days of age. Am. J. Ophthalmol., 61:1458, 1966.
- Roberts, S.R.: The Collie eye anomaly. J. Am. Vet. Med. Assoc., 155:859, 1969.
- Schmidt, GM; Ellersieck, MR; et al. Inheritance of retinal dysplasia in the English springer spaniel. J Am Vet Med Assoc 1979; 174: 1089-1090.
- Rubin, LF; Clinical features of hemeralopia in the adult Alaskan Malamute. J Am Vet Med Assoc 1971; 158: 1696-1698.Silverstein, A.M.: The pathogenesis of retinal dysplasia. Am. J. Ophthalmol., 72:13‑21, 1971.
- Sargan DR, Withers D, Pettit L, Squire M, Gould DJ, Mellersh CS. Mapping the mutation causing lens luxation in several terrier breeds. J Hered 2007. doi:10.1093/jhered/esm029
- Smith RIE, Peiffer RL, Wilcock B. Some aspects of the pathology of canine glaucoma. Prog Vet Comp Ophthalmol 1993; 3: 16-27.
- Stades FC. Persistent Hyperplastic Tunica Vasculosa Lentis and Persistent Hyperplastic Primary Vitreous (PHTVL/PHPV) in 90 closely related Dobermann Pinschers, Clinical aspects. J Amer Anim Hosp Assoc 1980: 16: 739.
- Turney C, Chong NHV, et al. Pathological and electrophysiological features of a canine cone-rod dystrophy in the miniature longhaired dachshund. Invest Ophthalmol vis Sci 2007;48:4240-4249.
- van der Linde-Sipman JS. Dysplasia of the pectinate ligament and primary glaucoma in the Bouvier des Flandres dog. Vet Pathol 1987; 24: 201-6.
- Wallin-Håkanson, B; Wallin-Håkanson, N; Hedhammar, Å; Influence of selective breeding on the prevalence of chorioretinal dysplasia and coloboma in the rough collie in Sweden. J Small Anim Pract 2000; 41: 56-59.
- Wallin-Håkanson, B; Wallin-Håkanson, N; Hedhammar, Å; Collie eye anomaly in the rough collie in Sweden: genetic transmission and influence on offspring vitality. J Small Anim Pract 2000; 41: 254-258.
- Wood JLN, Lakhani KH, Read RA. Pectinate ligament dysplasia (PLD) and glaucoma in flat coated retrievers. II Assessment of prevalence and heritability. Veterinary Ophthalmology 1998; 1: 91-99.
Wrigstad A, Nilsson SEG, Dubielzig R, Narfström K. Neuronal ceroid lipofuscinosis in the Polish owczarek nizinni (PON) dog. A retinal study. Doc Ophthalmol 1995; 91: 33-47.
Veterinary Ophthalmology (2002 onwards)
Relevant articles in (2002 onwards)
Journal of Small Animal Practice