Use of a contact lens telescopic system in low vision patients (original) (raw)

The Optical Functional Advantages of an Intraocular Low-Vision Telescope

Optometry and Vision Science, 2002

An implantable miniaturized telescope (IMT) for low vision has recently been developed. Surgically inserted into only one eye of patients with bilateral central visual loss, the IMT provides a nominal magnification of 3.0؋ and a field-of-view of 6.6°(9.2°for the 2.2؋ magnification version). Theoretical concerns have been raised regarding the ability of patients to function with a large interocular magnification difference, the impact of the monocular restriction of the field-of-view, and the impact of this design on depth perception. This article addresses these concerns regarding the design of the IMT in comparison with spectacle-mounted telescopes and combined intraocular lens/spectacle (or combined contact lens/spectacle) telescopic systems. The effective field-of-view (as determined by the combination of both the field-of-view and the field-of-fixation), the effects of head motion and the vestibular reflex, and the disruption of stereo depth perception with a monocular device are considered here. Physiological optics considerations of these issues show that the IMT may have important advantages over other designs of magnification devices for patients with age-related macular degeneration.

Quality of vision with presbyopic contact lens correction: subjective and light sensitivity rating

Graefe's Archive for Clinical and Experimental Ophthalmology, 2001

Purpose: To quantify the quality of vision achieved with multifocal and bifocal contact lenses. Methods: We analyzed differential light sensitivity by computerized automatic perimetry in 21 patients wearing monofocal soft contact lenses (group 1, controls) and multifocal and bifocal contact lenses (groups 2 and 3, respectively). Seven patients each were fitted with multifocal or bifocal contact lenses; seven patients were without contact lenses (without correction for testing the visual periphery and with near-vision correction using monofocal contact lens for testing the central 30 degrees of vision). The type of correction was randomly changed in a crossover fashion so that each eye was examined at different times with different corrections. Humphrey 640 VFA computerized automated perimetry was used to test visual fields at baseline, 45 days, and 3, 4.5, and 6 months. Results: A statistically significant difference was found between the global sensitivities (GS) of the central visual field in patients with near-vision monofocal contact lenses and with bifocal contact lenses (P=0.0273) and between the GS of the central visual fields with multifocal contact lenses and with bifocal contact lenses (P=0.0261). In both cases, the GS were significantly reduced with bifocal contact lenses (total GS: group 1, 11256 dB (Decibels); group 2, 11154 dB; group 3, 10679 dB). Conclusions: The results indicate that there is reduced differential light sensitivity in the central 30 deg of the visual field with bifocal contact lenses compared with multifocal contact lenses and monofocal contact lenses (controls).

Notes on the use of low magnification telescopes in low vision care

Clinical and Experimental Optometry, 1990

Several areas related to the use of telescopes in low vision are reviewed. These include: contrast sensitivity function; eccentric viewing through a telescope; field of view; telescope used in reverse; and IOL-spectacle lens telescopic systems. Experimental data are included to support selected clinical observations routinely made by low vision clinicians.

In-the-spectacle-lens telescopic device for low vision

Ophthalmic Technologies XII, 2002

Spectacle mounted telescopic systems have been prescribed for visual impairment, providing magnified images of objects at farther distances. Typically, bioptic telescopes are mounted toward the top of spectacle lenses or above the frame with the telescope eyepiece positioned above the eye's pupil. This allows the wearer to alternate between the magnified narrow field of view available through the eyepiece and the unmagnified wide view through the carrier lens using head motion. The main obstacles to acceptance are the obvious appearance, limited field of the smaller Galilean telescopes, and weight of the larger Keplerian telescopes. We designed a spectacle-mounted wide-field Keplerian telescope built completely inside the spectacle lens. The design uses embedded mirrors inside the carrier lens for optical pathway folding and conventional lenses or curved mirrors. The small size of the ocular and its position with additional mirror tilt enable the user to view the magnified field simultaneously and above the unmagnified view of the uninterrupted horizontal field that is important for user's safety. This design enables the construction of cosmetic telescopes that can be produced as a commodity lens blank and surfaced to include the patient prescription. These devices may be also of utility in military and civilian use.

In-the-spectacle-lens telescopic device for low vision

2002

Visual performance of two simultaneous vision multifocal contact lenses

Ophthalmic and Physiological Optics, 2013

Purpose: To evaluate and compare the visual performance of two simultaneous vision multifocal contact lenses (CLs). Methods: In this cross-over study design 20 presbyopic subjects were fitted with two different simultaneous vision multifocal CLs (the PureVision Multifocal Low Add and Acuvue Oasys for Presbyopia) in random order. After 1 month, binocular distance visual acuity (BDVA) under photopic (85 cd/m 2) and mesopic (3 cd/ m 2) conditions, binocular near visual acuity (BNVA), binocular distance contrast sensitivity function (CSF) under photopic and mesopic conditions, binocular near CSF and defocus curve were measured. Subjects were then refitted with the alternative correction and the procedure was repeated. Results: Mean BDVA under photopic conditions was similar for the Acuvue Oasys for Presbyopia and PureVision Multifocal Low Add: 0.01 AE 0.08 and 0.00 AE 0.08 logMAR, respectively (P = 0.45). Under mesopic conditions the values of BDVA were 0.20 AE 0.58 and 0.11 AE 0.09 logMAR, respectively (P = 0.005). Mean BNVA was 0.20 AE 0.05 and 0.15 AE 0.08 logMAR for the Acuvue Oasys and PureVision Low Add, respectively (P = 0.06). Binocular distance CSF testing revealed no statistically significant differences between lenses under photopic, mesopic or near conditions. Both lenses provided a comparable intermediate visual acuity. Conclusions: Both simultaneous vision multifocal CLs provided adequate distance visual quality under photopic and mesopic conditions, and better visual acuity was provided under mesopic conditions for the Purevision lens. Both lenses provided adequate visual performance at intermediate distance, but the near visual acuity appears to be insufficient for early presbyopes who require a moderately demanding near visual quality.

Comparative study on the clinical performance of Acuvue and Focus contact lenses

International Contact Lens Clinic, 1997

We compared the visual performance of Acuwue and Focus contact fenses with spectacle correction; 17 Hong Kong-Chinese were recruited, and conrrast thresholds (at spatial frequencies of 1.0, 4.0, and 16.0 c/&g) were measured for each type of correction. Our results showed that the level of myopia did not affect the contrast thresholds measured for each type of correction at all IeveE of spatial frequencies tested. There was also no significant difference in the contrast thresholds between types of correction used. The subjective performances of the two brands of lens used were also assessed by asking each subject to answer a questionnaire at the end of the study. The scorings in the questionnaire for Focus were consistently more favorable than those for Acuwue for all symptom wariables. This suggested that subjects preferred Focus to Acuvue, although the differences did not reach statistical significance. Our results also showed that "lens discomfort" was the most powerful symptom variable that determined a subject's overall Iens preference. 0 Elsewier Science Inc. 1997

Visual Performance of Subjects Wearing Presbyopic Contact Lenses

Optometry and Vision Science, 2006

Purpose. The purpose of this study is to assess the visual performance of subjects wearing gas-permeable (GP) multifocal contact lenses, soft bifocal contact lenses, GP monovision lenses and spectacles. Methods. The study included 32 subjects between the ages of 42 and 65 years wearing GP monovision, the Acuvue Bifocal (Vistakon), the Essentials GP Multifocal (Blanchard), and progressive addition lenses (PAL; spectacles group). There were eight subjects in each of these groups who were already wearing these modalities. Binocular low (18%) and high (95%) contrast acuities were recorded using the Bailey-Lovie chart; binocular contrast sensitivity from 1.5 to 18 cycles per degree (cpd) measured with the Vistech VCTS 6500 system, and monocular glare sensitivity at three luminance settings (400, 100, and 12 foot lamberts) was measured using the brightness acuity tester (BAT). Binocular near visual task performance (a modified version of letter counting method used in previous presbyopic studies) was also assessed. Results. For the contact lens-wearing groups, subjects wearing GP multifocals provided the best binocular high and low contrast acuity followed by soft bifocal wearers. There was relative parity between the binocular high and low contrast acuity with PAL and GP multifocal wearers. Monovision acuity, measured binocularly, was determined to be lower than the other three groups with this difference being most significant with high contrast acuity. Among contact lens-wearing groups, it was observed that GP multifocal lens wearers experienced the lowest amount of monocular disability glare followed by soft bifocal wearers and monovision wearers. Subjects wearing soft bifocal lenses and monovision demonstrated slightly reduced binocular contrast sensitivity at all spatial frequencies. In the contact lens groups, GP multifocal lens wearers had the highest binocular contrast sensitivity at all spatial frequencies, on parity with PAL wearers, except at the highest spatial frequency (18 cpd) at which PAL wearers had better vision. Error scores for the binocular near visual task performance between the four groups revealed subjects with GP multifocal lenses and PAL wearers to have the least errors, followed by monovision users and then soft bifocal wearers with the most errors. Conclusion. Subjects wearing GP multifocals, soft bifocals, monovision, and PAL spectacles have good binocular contrast sensitivity, satisfactory binocular low and high contrast acuity, and increased sensitivity to glare. Presbyopic subjects requiring the use of contact lenses under dim light levels could benefit from GP multifocal lenses. Contrast and glare sensitivity evaluations provide significant information regarding the visual performance of the presbyopic contact lenses and should be included in regular presbyopic contact lens fitting. (Optom Vis Sci 2006;83:611-615)

The Impact of Scleral Contact Lens Vault on Visual Acuity and Comfort

Eye & Contact Lens: Science & Clinical Practice, 2018

To assess how varying degrees of corneal clearance of scleral contact lenses (ScCL) impact visual acuity (VA) and comfort in patients with corneal ectasia. Method: Three ScCL were fitted to 20 subjects with previous diagnosis of either keratoconus (n¼18) or pellucid marginal degeneration (n¼2). Fitting of ScCL was based on corneal sagittal height (CSH) measured with Visante OCT at a 15-mm chord on the horizontal meridian. To select the ScCL from the diagnostic lens set, values of 325, 375, and 425 mm were randomly added in sequence to CSH. Subjects wore ScCL for 1 hr. Central corneal clearance (CCC) and topographic corneal clearance (TCC) along the vertical meridian were assessed using an ultralong optical coherence tomographer. High-contrast VA (HCVA) and low-contrast VA (LCVA) were measured using a logarithm of the minimum angle of resolution VA chart, and comfort ratings were obtained with a standard comfort scale (0-100). Results: Mean CSH in the horizontal meridian was 3.7860.53 (range: 3.33-4.17) mm at a 15-mm chord. Mean CCC was 1906100 mm (TCC: 160694 mm at +3 mm and 180694 mm at 23 mm), 3606120 mm (TCC: 2606100 mm at +3 mm and 3306110 mm at 23 mm), and 4506170 mm (TCC: 3206120 mm at +3 mm and 4006120 mm at 23 mm) for each lens (P¼0.001). Mean HCVA for lenses 1, 2, and 3 were 0.0560.12, 0.0760.11, and 0.1160.08 respectively, which were significantly different (P¼0.02). Tukey post hoc analysis showed that this difference was only significant between lenses 1 and 3 (P¼0.01). Similar findings were found for LCVA. Comfort ratings for lenses 1, 2, and 3 were 74.969.2, 79.7611.6, and 78.6610.8, respectively (P¼0.24). Conclusion: The CSH is an effective method of determining the appropriate lens/cornea relationship. Lens 2 (+375 mm) gave the best combination of acuity and comfort ratings. Evaluation of the fluorescein pattern must be balanced with VA and comfort ratings for successful fitting in a clinical setting.

Increase use of contact lenses for optical correction

Journal of Institute of Medicine, 2007

Contact lenses (CL) are considered as a widely accepted modality of refractive correction in the last few decades, though their history is nearly about 100 years old. Millions of people are wearing contact lenses all over the world. Every year the number of CL wearers has increased significantly. No definite statistics are available regarding the number of people wearing contact lenses in Nepal. Contact lenses are not used only for refractive correction but also for therapeutic and cosmetic use. 1

Use of a contact lens telescopic system in low vision patients (original) (raw)

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