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Refractive Errors, Myopia, and Presbyopia
Published in Ching-Yu Cheng, Tien Yin Wong, Ophthalmic Epidemiology, 2022
Ka Wai Kam, Chi Pui Pang, Jason C. S. Yam
Currently, correction of presbyopia is mainly by optical, surgical, and pharmaceutical methods. Optical correction of presbyopia can be achieved using spectacles, contact lenses, a refractive procedure, or intraocular lenses. Even though this approach is simple, direct, and relatively inexpensive, some people find it inconvenient in daily life and that it limits sport activities.180 Keratorefractive procedures using laser ablation techniques to generate either monovision or a multifocal cornea, i.e., presbyLASIK, are among the surgical approaches. Since presbyLASIK can lead to irreversible compromise in distance vision, patient selection and pre-operative counseling are essential.181 Another surgical approach is intracorneal or corneal inlays. An intracorneal inlay is reversible but it may create biological intolerance and affect optical performance. A corneal inlay is irreversible and provides monovision, but there are complications, including corneal haze, which requires the explantation of the inlay.182 All the surgical approaches are invasive with risk for infection.
Stereoacuity and optics
Published in Pablo Artal, Handbook of Visual Optics, 2017
The results are presented in Figure 23.9, reflecting that monovision with 0.75 D added caused a deterioration in stereoacuity by a factor of close to 4. However, the use of a small aperture in one of the eyes significantly reduced the negative effect of monovision on stereoacuity. The results of the experiment showed that a small aperture (e.g., an intrastromal corneal inlay) can provide values of stereoacuity similar to those found under normal binocular vision. We should mention that these experiments were performed under photopic conditions; mesopic and scotopic illumination conditions were not studied in this work. Therefore, more works are needed to draw conclusions for a wider range of experimental conditions.
Predictive Factors for Corneal Scarring in Progressive Keratoconus Patients after Corneal Collagen Cross-linking
Published in Ophthalmic Epidemiology, 2021
Senay Asik Nacaroglu, Ahmet Kirgiz, Nilay Kandemir Besek, Muhittin Taskapili
In addition to studies indicating that corneal scar development reduces vision, there are also studies suggesting that it does not affect vision.4–11,20 In this study, the postoperative mean CDVA of the scar group did not differ from that of the control group, and the postoperative increase in visual acuity between the groups was found to be significantly lower in the scar group. The postoperative mean CCT in the scar group was considerably lower in comparison with the control group. Although scar formation in the cornea does not affect vision, it may cause difficulty in the follow-up of the progression of keratoconus since it causes the apparent thinning of the cornea. Furthermore, if corneal inlay surgery is planned for these patients in the future, scar formation may affect this adversely. The retrospective design and the lack of confocal microscopic evaluation and perioperative CCT measurement are the limitations of the study.
Sterile Excimer Laser Shaped Allograft Corneal Inlay for Hyperopia: One-year Clinical Results in 28 Eyes
Published in Current Eye Research, 2021
Cafer Tanriverdi, Ayse Ozpinar, Sezer Haciagaoglu, Aylin Kilic
After applying topical anesthesia (proparacaine hydrochloride 0.5%), a femtosecond-assisted flap was created (iFS 150kH, Intralase, Johnson&Johnson Vision, USA) with an intended flap thickness of 110 microns, a flap diameter of 8.8 mm, and a superior hinge of 70 degrees. The stromal interface was rinsed carefully with balanced salt solution during and after the opening of the flap. As a second surgical step, the corneal inlay was carefully transferred onto the exposed stromal bed by using a specially designed stainless steel loop and visually centered on the pupillary axis of the patients’ eye using the surgical microscope of a clinical excimer laser (VISX S4, CustomVue S4IR, Johnson&Johnson Vision, USA). During the final surgical step, the surgeon assured the smoothness of the lenticule’s edges, its centration, and its symmetry prior to replacing the flap by means of a cannula. After the flap was repositioned onto the stromal bed, a soft bandage contact lens (ACUVUE Oasys, Johnson & Johnson Vision Care Inc.) was placed onto the cornea. All implantations of the inlay (Transform, Allotex Inc. Boston, MA, USA) were performed by the same surgeon (AK). The ACI we used in our study had a diameter of 6.0 mm and its thickness varied according to the refractive status of the patient. These ACIs are prepared with the help of excimer laser after all virological and bacteriological tests are performed from human cornea by a certified eye bank. Each ACI comes sterile, in solution in a bottle and has a shelf life of 2 years.
Clinical Efficacy of Pinhole Soft Contact Lenses for the Correction of Presbyopia
Published in Seminars in Ophthalmology, 2019
Si Yoon Park, Young Joon Choi, Ji Won Jung, Moonjung Choi, Eung Kweon Kim, Kyoung Yul Seo, Tae-Im Kim
Ocular dominance testing was performed to determine the more suitable eye for pinhole contact lens application. Two different methods described in previous studies on small-aperture corneal inlay surgery were used.19 For determination of the motor dominant eye, the participants were asked to make a small circle with their fingers extended while looking at a distant target through the circle. Then, they were asked to close each eye sequentially, gaze at a distant target, and identify the eye being used for gazing at the target; the identified eye was designated as the motor dominant eye. The sensory dominant eye was determined by a blur test, which involved the placement of a + 1.50 D spectacle trial lens in front of the eye when the subject’s vision blurred. The eye that was more tolerant to the plus-power blur was defined as the sensory non-dominant eye. When these two dominance tests showed different results, the sensory non-dominant eye was selected for pinhole contact lens application.