原著
The Role of Lens Luxation in Inherited Glaucoma in the Beagle
1998 年 17 巻 1-2 号 p. 1-2_1-1-2_8
詳細
1998 年 17 巻 1-2 号 p. 1-2_1-1-2_8
In primary open angle glaucoma in the Beagle, the lens luxation is secondary to the gradual enlargement of the globe in the untreated disease. The normal zonules are gradually stretched and eventual tear, usually near their insertion at the lens equator. Two litters of Beagles (3 males/4 females) with inherited glaucoma were evaluated, with four dogs (2 males/2 females) receiving unilateral extracapsular lens extractions at four months of age, and the remaining three dogs (1 male/2 females) serving as the controls. All eyes of the dogs were examined serially by applanation tonometry, gonioscopy, tonography and a-scan ultrasonography. From the control group after euthanasia, the globes and lenses were harvested at 6 (2 lenses), 12 (2 lenses), and 28 (2 lenses) months of age for scanning electron microscopy (SEM). The operated dogs were euthanized at 28 months, and all globes and lens were examined by SEM.
The mean intraocular pressure (IOP) began to increase and the tonographic facility of aqueous outflow decreased bilaterally in the four dogs with the unilateral lensectomies and the three nonoperated dogs at about 6 to 8 months of age. In the non-operated fellow eyes, the aphakic crescents associated with the lens subluxation begin to develop when the dogs were 18 month old and axial globe lengths exceeded 21 mm. The lenses remained in the patellar fossa in all dogs at 28 months of age.
The zonules in the pre-glaucomatous Beagle at six months of age appeared normal by SEM. At 12 months and thereafter the zonules appeared to be progressively stretched. In the 28-month-old glaucomatous Beagles (six eyes) focal areas of zonular disinsertation from the periphery of the equatorial lens capsule and zonulary retraction occurred. Zonular transection occurred immediately posterior to the zonular attachments at the lens equator leaving zonular remnants.
Extracapsular lensectomies in these young normotensive Beagles, bred for primary open angle glaucoma, did not prevent nor delay the onset of the disease. The elevation in intraocular pressure, reduction in the facility of aqueous humor outflow (as measured by pneumatonography) and increased axial globe lengths (as measured by a-scan ultrasonography) preceded the gradual stretching and focal disinsertions of the zonules, and subluxation of the lens.
