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

Full Abstract

OBJECTIVE:
To determine ocular dimensions (A- and B-scan ultrasound) and corneal curvature (radius of corneal diameter determined in B-scan ultrasound) in the equine eye and to calculate the appropriate dioptric power for a posterior chamber intraocular lens (IOL) necessary to achieve emmetropia in the eyes of horses undergoing lens extraction.

ANIMALS:
Fourteen clinically normal adult horses of various breeds. Additionally, for comparison, one American Miniature colt foal, and one 2.5-year-old Shire gelding were examined.

PROCEDURE:
B-scan ultrasound was performed on one eye from each horse. One eye from both the Shire and the American Miniature were examined for comparison. Data from ultrasound (globe measurements and corneal curvature), and the estimated postoperative IOL positions were entered into theoretical IOL formulas (Binkhorst and Retzlaff theoretical formulas) in order to calculate the predicted IOL strength required to achieve emmetropia after lens extraction in horses. Results:
Mean axial length of globes was 39.23 mm +/- 1.26 mm, mean preoperative anterior chamber depth (ACD) was 5.63 +/- 0.86 mm, and mean lens thickness was 11.75 +/- 0.80 mm. Predicted postoperative ACD (PACD) was calculated as the ACD plus 50% of the lens thickness. Additionally, PACD 2 mm anterior and 2 mm posterior to the center of the lens were calculated in order to evaluate the effect of IOL position on its required refractive power. Required IOL strength calculated, using the three values for the predicted postoperative ACD, was 29.91 D +/- 2.50, 29 D +/- 2.52 (center of lens); 27.13 D +/- 2.27, 26.33 D +/- 2.20 (2 mm anterior to center of lens); and 33.18 D +/- 2.78, 32.24 D +/- 2.68 (2 mm posterior to center of lens) with the Binkhorst and Retzlaff theoretical formulas, respectively.

CONCLUSIONS:
An IOL of substantially lower diopter strength than that needed in either dogs or cats is required to achieve emmetropia after lens extraction in adult horses. IOL strength of approximately 30 D, depending on where the IOL ultimately comes to rest, will probably be required.

Learn Faster Today Improve your study skills

Author information

Author/s: McMullen, Richard J (RJ); Gilger, Brian C (BC);

Affiliation: Department of Clinical Sciences, College of Veterinary Medicine, North Carolina State University, Raleigh, NC, USA.

Journal and publication information

Publication Type: Evaluation Studies; Journal Article

Journal: Veterinary ophthalmology (Vet Ophthalmol), published in England. (Language: eng)

Reference: -2006 Sep-Oct; vol 9 (issue 5) : pp 357-60

Dates: Created 2006/08/30; Completed 2006/10/19;

PMID: 16939465, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

External Links for this article (including full text providers, if available):

Click Electronic Full-text Provider Links to see options for finding the electronic full text links to this article. Note there may be a subscription or fee required for access to the full text. See our FAQ for information on finding FREE full text articles.

This article may also be located in paper journal collections available in many libraries. Use the Journal and Publication Information above to find the full article.

MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Animals
Animals, Newborn
Biometry
Cataract - physiopathology; veterinary
Cataract Extraction - veterinary
Cornea - anatomy & histology; ultrasonography

Female
Horse Diseases - physiopathology
Horses
Lenses, Intraocular - veterinary
Male
Postoperative Period

These are the highest related articles currently in the database:

Aspiration of congenital and soft cataracts in foals and young horses. 29 Sep 1974
Significance of lesions of the cornea and lens in the examination of horses for soundness. 29 Sep 1971
Diagnosis and treatment of lens diseases. 29 Nov 1992
Congenital aniridia in a pony. 30 Jan 1985
Diagnostic ultrasonography of equine lens and posterior segment abnormalities. 28 Feb 2004
[Prolapse of the uterus and cataract: a comparison of veterinary and human medicine in Greco-Roman antiquity] 30 Dec 2004
Cataracts in cattle. 13 Jul 1971
Congenital nuclear cataracts in the Morgan horse. 30 May 1984
Iridial hypoplasia (aniridia) accompanied by limbic dermoids and cataracts in a group of related quarterhorses. 30 Aug 1990
The lens and cataracts. 30 Jul 2004

See 100+ related articles.