Medical Hypothesis, Discovery & Innovation in Optometry

Background: A key manifestation of Parkinson’s disease (PD) is visual impairment. Cognitive impairment has been found to overlap with convergence insufficiency (CI) in patients with PD and is associated with significantly greater near point convergence (NPC) distance. Difficulty in reading and diplopia were the most common symptoms of CI in PD. The prevalence of CI is greater among patients with PD. Therefore, this study aimed to assess the relationship between PD and CI.
Methods: Studies that had included data on CI, NPC, or both were selected by searching PubMed/MEDLINE and clinicaltrails.gov, without any timeline or language limitation. The following terms were used in PubMed/MEDLINE search: ‘Clinical Trials’, ‘Parkinson’s Disease’, and ‘Convergence Insufficiency’. For clinical trials.gov database, the terms ‘Parkinson’s Disease’, ‘Convergence Insufficiency’, and ‘Completed Studies’ were used. Only those studies with control subjects were included. PubMed/MEDLINE search yielded 1,563 articles, but no article was found in the clinical trails.gov search. Twelve articles met the inclusion criteria, among which nine articles were selected as they had data on CI or NPC distance (cm), and PD.  
Results: Overall, there were 1,563 articles; among them, 12 articles met the inclusion criteria. Nine articles were selected based on their data concerning CI or NPC distance (cm) and PD. Relative to the control group, the PD group had high CI. In addition, PD group showed increase in NPC distance than the control group.
Conclusions: These data suggest that the patients with PD had an increased likelihood of developing CI visual symptoms, and increased NPC distance than healthy controls. These findings indicate that regular eye examination is very important for patients with PD.

Background: The MOS 36-Item Short-Form Health Survey (SF-36) Bahasa Melayu language version is widely used to determine the health outcomes in Malaysia. Low vision is a condition where vision cannot be restored and vision rehabilitation is required to overcome the challenges it imposes. The SF-36 Bahasa Melayu language version can be used to measure the health outcomes among low-vision patients. However, little information is available among low-vision patients. This study aimed to assess the reliability of the SF-36 Bahasa Melayu language version among low-vision patients.
Methods: Fifty low-vision patients aged 14 to 74 years (mean ± standard deviation: 44.58 ± 18.70 years) were randomly selected. All low-vision patients were interviewed twice by the same interviewer with a 2-weeks interval.
Results: The SF-36 Bahasa Melayu language version showed acceptable and good Cronbach’s alpha values of 0.68, 0.67, 0.76, 0.72, 0.73, 0.75, 0.72, 0.73 for physical function, role-physical, body pain, general health, vitality, social functioning, role-emotion, and mental health, respectively, in the first interview. The second interview also revealed similar Cronbach’s alpha values. The SF-36 Bahasa Melayu language version also showed a good repeatability between the first interview and the second interview, with Pearson’s correlation coefficients ranging from 0.6 to 0.9.
Conclusions: From this study, it can be concluded that the SF-36 Bahasa Melayu language version is reliable and repeatable. It is a useful tool to measure health outcomes among Malaysian low-vision patients. However, a future study of low-vision patients from the rural population and age groups representing the youth, working adults, and older individuals is necessary to obtain better outcomes of SF-36 in Bahasa Melayu language-based information on the health status of low-vision patients.

Background: This study compared outcomes of combined toric versus spherical intraocular lens (IOL) implantation in patients with low corneal astigmatism.
Methods: In this retrospective contralateral study, patients with corneal astigmatism who received combined toric (FIL 611 T, Soleko, Rome, Italy) and spherical IOL (FIL 611 T, Soleko, Rome, Italy) implants were recruited. Eyes were examined preoperatively and then again 3 months postoperatively. Postoperatively, uncorrected distance visual acuity (UCDVA), residual astigmatism, and spherical equivalent (SE) were compared between the toric IOL-implanted eyes and the spherical IOL-implanted fellow eyes.
Results: Among the 46 included cases (age 69 ± 12.7 years [mean± standard deviation]; range: 60‒78 years), 86.9% of eyes (n = 40) in the toric IOL group had a postoperative refractive cylinder of ≤ 0.25 diopters (D), compared with 4.3% (n = 2) of eyes in the spherical IOL group. Both groups showed a statistically significant reduction in refractive cylinder and improvement in UCDVA after cataract surgery (both P = 0.01). Similarly, toric IOLs were superior (69.6%) to spherical lenses (2.2%) in obtaining a SE of ≤ 0.25 D.
Conclusions: To our knowledge, no previous study had sought to compare low-power toric and spherical IOLs in low corneal astigmatism in the same patient's eyes. Our findings suggest that low-power toric IOLs may result in good refractive outcomes as compared with spherical IOLs implanted in the fellow eye of the same patient, although both result in significant UCDVA improvement. Well‐designed clinical research studies with a longer follow-up and more participants are necessary to confirm these findings.

Background: Accommodation changes ocular parameters, such as the anterior chamber volume (ACV), anterior chamber depth (ACD), anterior chamber angle (ACA), and pupil diameter (PD), which can reflect a risk of angle-closure glaucoma. Previous studies of changes in ocular anterior segment parameters, have used high diopters or maximum amplitude. Here, we focused on normal accommodation at a reading distance of 30‒40 cm. The aim of this study was to assess changes in anterior segment parameters during a normal accommodative state, using a Scheimpflug imaging system.
Methods: In this cross-sectional study, 40 emmetrope subjects (mean ± SD of age: 22 ± 4.0 years) who met the inclusion criteria and provided informed consent were enrolled. Clinical history, refraction, amplitude of accommodation, slit lamp examination, Goldman applanation tonometry, and Pentacam investigations were performed on all subjects. Accommodative and non-accommodative targets were induced via the Pentacam. Two seconds were allowed for accommodation or relaxation prior to measurements in each eye.
Results: Eighty normal eyes were evaluated; a small but statistically significant change in ACV, ACA, and PD during accommodation (P < 0.01, < 0.01, and < 0.05, respectively) was observed. The ACD did not change substantially with accommodation (P = 0.29). The mean ± SD values of ACV, ACD, ACA, and PD before and after accommodation were 151.85 ± 24.04 mm3 and 145.38 ± 23.30 mm3, 2.87 ± 0.28 mm and 2.86 ± 0.27 mm, 35.06° ± 3.68° and 33.84° ± 3.72°, and 3.46 ± 0.57 mm and 3.41 ± 0.53 mm, respectively.
Conclusions: Accommodation changes ocular parameters, such as ACV, ACA, and PD, in healthy young emmetropes. Interestingly, the ACD remains unaltered during accommodation. Nevertheless, although these changes were statistically significant, they were not clinically significant in our study.

Background: There is growing concern that the increased use of personal digital devices, which emit a high proportion of their light in the blue wavelengths, may have harmful effects on the retina. Extensive historical as well as current research demonstrates that exposure to high energy visible light (blue light) can damage the retina under certain circumstances. There are, however, no studies that directly address whether blue light at the intensities emitted by digital devices can potentially cause such harm. The present review aimed to examine whether blue light exposure from computers, tablets, and cell phones can, when used habitually over a prolonged period of time, be harmful to the retinal.
Methods: A search of the literature on blue light-induced retinal damage was performed using a number of scientific search engines, including BioOne Complete™, Google Scholar™, Paperity™, PubMed™, and ScienceOpen™. Studies most significant for addressing the question of possible harmful effects of blue light emitted by personal digital devices were selected from this search and reviewed.
Results: The data from the selected studies were summarized and their limitations in addressing the question of whether the blue light from personal digital devices is capable of producing retinal damage were addressed. Based on these limitations, a practical experimental protocol for collecting the additional data needed was proposed. Data from pilot experiments are presented that indicate the practicality of this approach.
Conclusions: The currently available data on the effects of blue light on the retina are not sufficient to refute the hypothesis that the use of personal digital devices could, over a lifetime, produce retinal damage. Additional studies, such as those proposed in this article, are needed to resolve this issue.