Ophthalmic Research – Heather MAK

MAK Kayew Heather

 

Research areas:

(1) Anterior segment optical coherence tomography imaging
(2) Mechanisms of retinal ganglion cell degeneration and regeneration

Publications:

  1. Mak H, Xu G, Leung CK. Imaging the iris with swept-source optical coherence tomography: relationship between iris volume and primary angle closure. Ophthalmology. 2013;120:2517-24.
  2. Lai I, Mak H, Lai G, Yu M, Lam DS, Leung CK. Anterior chamber angle imaging with swept-source optical coherence tomography: measuring peripheral anterior synechia in glaucoma. Ophthalmology.
    2013;120:1144-9.
  3. Leung CK, Yu M, Weinreb RN, Mak H, Lai G, Ye C, Lam DS. Retinal nerve fiber layer imaging with spectral-domain optical coherence tomography: interpreting the RNFL maps in healthy myopic eyes. Invest Ophthalmol Vis Sci. 2012;53:7194-200.

 

Research Highlights:

(1) Measurement of iris volume with swept-source OCT
Iris plays an important role in determining the anterior chamber angle dimensions. Individuals with a narrow/closed angles are at a higher risk of developing angle-closure glaucoma – a leading cause of irreversible blindness. In this study, we measured iris volume and anterior segment parameters using a new swept-source anterior segment optical coherence tomography (OCT) and investigate factors associated with iris volume and iris volume change after pupil dilation in eyes with open angles and angle closure. We demonstrated that the mean iris volume decreased after pupil dilation in open-angle and angle closure eyes, and the degree of reduction was less in eyes with a smaller ACV. Both iris volume and ACV were important determinants.
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Figure 1. Algorithm for measurement of iris volume – Iris volume is calculated as a summation of pixel volume derived from individual B-scan images. A pixel volume is represented by [p(r+0.5)2- p(r – 0.5)2] ./2p = r. (pixel)3, where r is the distance between the pixel and the radial rotation axis and . is the angle between adjacent B-scans.

 

(2) Peripheral anterior synechiae imaging with swept-source OCT
Peripheral anterior synechiae (PAS) represents adhesional contact between the peripheral iris and the anterior chamber angle, which can be found in primary and secondary angle closure, acute angle closure, and chronic angle-closure glaucoma. We investigated the use of swept-source optical coherence tomography (OCT) for measuring the area and degree of peripheral anterior synechia (PAS) involvement in patients with angle-closure glaucoma. This is the first study illustrating the application of a swept-source OCT for reproducible measurements of the area and degree of PAS involvement. The finding can provide a new paradigm for evaluation of PAS progression and risk assessment for development of angle-closure glaucoma.
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Figure 2. Imaging of peripheral anterior synechiae with swept-source OCT: A video clip illustrating 3-dimensional, rotational display of peripheral anterior synechiae in a 62-year-old patient with primary chronic angle closure glaucoma with a history of trabeculectomy.

 

(3) Studying the intrinsic mechanisms of retinal ganglion cell regeneration
Retinal ganglion cells (RGCs), like other central nervous system neurons, are well-recognized for their developmental decline in regenerative potential. RGCs progressively lose the ability to regenerate axons with age. The loss of regenerative capacity of RGCs renders optic nerve injuries or degenerative optic neuropathies irreversible, leading to permanent visual impairment. We are investigating the intrinsic pathways to promote axonal regeneration of RGCs after optic nerve injury.
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Figure 3. Isolation of retinal ganglion cells – A retinal ganglion cell was isolated from a rat and identified with TUJ1 (Neuron-specific class III beta-tubulin).