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Biomedical subjects

L H Koh

Publications and source records attributed to L H Koh.

6 recordsLinked to original sources
PubMed2001

Complete sequences and phylogenetic analyses of a Singapore isolate of broad bean wilt fabavirus.

The complete nucleotide (nt) sequence of a Singapore isolate of broad bean wilt fabavirus from Megakepasma erythrochlamys L., designated BBWV-ME, was determined. Its bipartite genome consisted of two positive-sense single-stranded ribonucleic acids (RNA). RNA1 (5951 nt in length) encoded a putative protease cofactor, nucleotide triphosphate (NTP)-binding domain (helicase), viral genome-linked protein (VPg), protease and RNA-dependent RNA polymerase (RdRp). RNA2 (3607 nt in length) encoded a putative movement protein (MP) and coat proteins (CP). Genome organization of BBWV-ME was similar to other viruses in the Comoviridae family. Phylogenetic analyses showed that fabaviruses were more closely related to the comoviruses than the nepoviruses.

Base Sequence↗
PubMed1999

Size constancy and angular size matching in size perception of near objects.

Accurate judgment of the relative sizes of near objects at various distances is important for a variety of occupational visual tasks. This study involved matching the apparent size of each of a series of standard targets, placed at distances between 0.2 and 3 m and all subtending 2 degrees at the eye, with a comparison target of similar geometry, but at a fixed distance of 2 m. Natural binocular viewing of the targets demanded exercise of accommodation and convergence in an environment rich in cues to target size and distance. As the available cues were reduced, judgements of the lateral dimensions of the targets were found to change gradually from those predominantly based on size constancy to those mainly based on angular size matching. These results are qualitatively very similar to those observed in past studies with more distant objects and emphasize the need to maintain adequate cues if linear size is to be judged accurately.

Accommodation, Ocular↗
PubMed1998

Accommodative responses to anisoaccommodative targets.

Young subjects (mean age 25.2 +/- 2.3 years) viewed with symmetric convergence two fusible targets situated at different distances (i.e. anisoaccommodative targets). The fused target was a Maltese cross which subtended 3 degrees at the eye: the right and left arms of the cross were seen by both eyes and each of the other arms was seen by only one eye. The vergences of the anisoaccommodative targets differed by either 3.00 or 0.50 D. Accommodation of each eye was measured by a Canon R1 auto-refractor. There was no evidence of systematic anisoaccommodation. When presented with anisoaccommodative targets, the accommodation of both eyes tended towards a level which was more appropriate to the farther target, i.e. that which required less accommodative effort. Implications of the findings for optometry are briefly discussed.

Accommodation, Ocular↗
PubMed1998

Accommodation to perceived depth in stereotests.

The question of whether the eye may accommodate to the stimulus provided by apparent depth in stereograms is considered theoretically in relation to the magnitudes of the disparities and viewing distances found in typical clinical stereotests. It is concluded that, for the relevant range of disparities (< or = 2000 arc sec), any shift in accommodation is likely to be small (< or = 0.15 D). An experimental study with two different clinical stereotests (Lang, TNO) confirms this prediction.

Accommodation, Ocular↗
PubMed1997

A two-year experience of an acute pain service in Singapore.

The first anaesthesia-based acute pain service in Singapore is described. The benefits, risks and resource implications of such a service during its first two years are reviewed. One thousand two hundred and sixty-eight (1,268) post-operative patients were treated with either patient-controlled analgesia (310 patients) or epidural opioid analgesia (958 patients). Retrospective analysis of the data revealed good patient satisfaction with a low incidence of potentially life threatening side-effects: more than 79% of patients reported satisfaction with pain control while only 0.2% of patients receiving epidural opioid analgesia experienced clinically significant respiratory depression. There were no reports of respiratory depression in the patient-controlled analgesia group. The authors conclude that the provision of an acute pain service in the local context was safe and resulted in excellent post-operative patient satisfaction.

Acute Disease↗