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. 2025 Jun;15(6):2889-2894.
doi: 10.5455/OVJ.2025.v15.i6.58. Epub 2025 Jun 30.

Keratometry, biometry, and intraocular lens power calculation in Bornean sun bears (Helarctos malayanus euryspilus)

Yong Zheng Wai  1 , Boon Nie Yeoh  2 , Wai Seng Chiang  1 , Muhammad Hazim Bin Sharum  1 , Nurhayati Abdul Kadir  1 , Nur Hafizah Binti Mat Jalil  1 , Jessie Si Wai Ho  3 , Nur Nabila Sarkawi  4 , Siew Te Wong  2 , Nadzariah Cheng Binti Abdullah  5
Affiliations

Keratometry, biometry, and intraocular lens power calculation in Bornean sun bears (Helarctos malayanus euryspilus)

Yong Zheng Wai et al. Open Vet J. 2025 Jun.

Abstract

Background: Cataracts are a common ocular condition that affects captive sun bears, yet there is a lack of detailed case reports and ocular studies of this species.

Aim: The examinations aim to calculate the intraocular lens (IOL) power required to achieve emmetropia following cataract surgery.

Methods: Five Bornean sun bears diagnosed with cataracts at the Bornean Sun Bear Conservation Centre in Malaysia underwent ocular examination under general anesthesia. Keratometry and biometry data, including anterior chamber depth, crystalline lens thickness, and axial globe length, were collected using an automated keratometer and B-mode ultrasound. The Retzlaff, Binkhorst, Colenbrander, and Fyodorov formulas were used to estimate the required IOL power.

Results: The mean corneal keratometric power was 56.94 D, the mean axial globe length was 12.93 mm, and the mean calculated postoperative anterior chamber depth was 4.77 mm. The mean calculated IOL power was +92.96 D. Conclusion: Aphakic cataract surgery were decided following these findings showing no available commercial IOL implants for this species. These findings provide valuable baseline data for optimizing cataract surgery in Bornean sun bears.

Keywords: Biometry; Cataract; Intraocular lens power; Keratometry; Sun bear.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Fig 1.
Fig 1.. A: Hypermature crystalline lens dislocated anteriorly, resulting in elevated intraocular pressure. This eye was excluded from keratometry, biometry, and intraocular lens (IOL) power calculations. B: Automated keratometry was performed to measure corneal keratometric power. C: B-mode ultrasonography gently applied to the corneal surface covered with ultrasound gel. The eyelids had been spread apart with lid retractors. D: A-scan biometry, which is commonly used in humans, failed to generate numerical data despite prominent A-scan spikes being observed.
Fig. 2.
Fig. 2.. Axial globe length (AGL) measured using internal calipers on B-mode ultrasonograhy.
See this image and copyright information in PMC

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