Ophthalmic Research – Sayantan BISWAS

Sayantan BISWAS

 

Research areas:

(1) Prevalence of glaucoma in myopic individuals
(2) Application of a myopic normative database for detection of RNFL abnormalities.

 

Supervisor:

Prof LEUNG Kai Shun, Christopher

 

Publications:

  1. Biswas S, Jhanji V, Leung CK. Prevalence of Glaucoma in Myopic Corneal Refractive Surgery Candidates. Journal of Refractive Surgery. 2016, In press.
  2. Biswas S, Chen Lin, Leung CK. Retinal Nerve Fiber Layer Imaging in Myopia: Evaluation of a Myopic Normative Database for RNFL Thickness Analysis. Accepted for revision in JAMA Ophthalmology.

 

Research Highlights:

(1) Prevalence of Glaucoma in Myopic Corneal Refractive Surgery Candidates

Parapapillary atrophy and tilted optic disc configuration in myopia can blur the distinction between glaucomatous and non-glaucomatous optic discs, which may have caused the discrepancy in studies investigating the association between myopia and glaucoma. In this study, we investigated the prevalence of glaucoma, determined by the presence of retinal nerve fiber layer (RNFL) and neuroretinal rim abnormalities using spectral-domain optical coherence tomography (OCT) and color optic disc stereophotography in myopic corneal refractive surgery candidates and to investigate biometric factors associated with the occurrence of glaucoma. We showed that glaucoma was evident in 5.1% of myopic patients seeking corneal refractive surgery in China. The only biometric variable significantly associated with glaucoma was IOP. Corneal refractive surgeons should be watchful in the diagnostic evaluation of glaucoma among myopic corneal refractive surgery candidates.

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Figure 1. Examples illustrating a (A) glaucomatous eye and a (B) normal eye. Glaucoma was diagnosed when narrowed neuroretinal rim and optic disc excavation was detected in color optic disc stereophotographs with corresponding retinal nerve fiber layer (RNFL) abnormalities observed in both the RNFL thickness map and the RNFL thickness deviation map. In panel (A), narrowed neuroretinal rim and optic disc excavation were found at the inferotemporal sector of the optic disc. Corresponding inferotemporal RNFL abnormalities were evident in the RNFL thickness map and the RNFL thickness deviation map. In panel (B), although RNFL abnormalities were found in the RNFL thickness deviation map, there was no corresponding RNFL loss in the RNFL thickness map. The superotemporal and inferotemporal RNFL bundles appeared normal and symmetric in the RNFL thickness map. The convergence of the superotemporal bundles towards the macula rendered the superior quadrant encoded as “abnormal” in the RNFL thickness deviation map. No neuroretinal rim loss or optic disc excavation was detected in the color optic disc photograph.

 

(2) Retinal Nerve Fiber Layer Imaging in High Myopia: Evaluation of a Myopic Normative Database for RNFL Thickness Analysis

Analysis of optical coherence tomography (OCT) retinal nerve fiber layer (RNFL) abnormalities in high myopia eyes (spherical equivalent; SE≤-6.0D) has been complicated by high false positive errors. It is likely related to the lack of inclusion of high myopic subjects in the normative databases of many OCT instruments. We compared the diagnostic performance of a myopic normative database and the Cirrus HD-OCT (Carl Zeiss Meditec) built-in normative database for detection of RNFL abnormalities in high myopic eyes. Using different criteria to define RNFL abnormalities in the circumpapillary RNFL profile and in the RNFL thickness map, the myopic normative database outperformed the Cirrus HD-OCT normative database for detection of RNFL abnormalities in high myopic eyes. Hence, the application of a myopic normative database significantly improved the specificity without compromising the sensitivity compared with the instrument’s built-in normative database for detection of RNFL abnormalities in eyes with high myopia.

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Figure 2. Examples showing optic disc photographs (upper panel), retinal nerve fiber layer (RNFL) thickness deviation maps and circumpapillary clock hour RNFL profile (scan circle diameter ~3.46mm) analysed by the Cirrus HD-OCT normative database (middle panel) and the myopic normative database (lower panel) of a pathological high myopic healthy eye (spherical equivalent -8.75D; axial length 26.39mm) (A) and a pathological high myopic glaucomatous eye (spherical equivalent -7.00D; axial length 26.10mm) (B). RNFL thickness measurements below the lower 95% and 99% percentiles are encoded in yellow and red, respectively, in the RNFL thickness deviation map and in the circumpapillary clock hour RNFL profile.