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

Abstract

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.

Keywords: Haliaeetus leucocephalus; avian; bald eagle; biometry; intraocular lens; phacoemulsification.