Dynamic range of focus recovery in presbyopes after laser scleral microporation
Laser scleral microporation rejuvenates dynamic range of focus by increasing scleral pliability, allowing underlying structures to move more freely
While considered by many to be a “normal process of aging,” the loss of the dynamic focusing function of the eye, presbyopia, is a progressive disease of ocular aging. Presbyopia affects approximately 1.8 billion people globally.1 Estimated global annual productivity losses are approximately 0.037% of the global gross domestic
product in presbyopic adults less than 65 years of age.2
This socioeconomic issue is particularly problematic in developing countries where people are less likely to find visual correction.As people depend upon glasses or bifocals to perform near tasks, there is a decrease in health-related quality of life (HRQOL) and an increase in the risk of ocular diseases. Presbyopia is correlated with ocular rigidity, glaucoma, ocular hypertension, dysfunctional lens syndrome, age-related macular degeneration and cataracts, which can contribute to the effects of aging on ocular tissues.3
Accumulation of advanced glycation end products (AGEs) causes crosslinking of collagen fibrils, and they are formed endogenously as well as from exogenous sources.4–6 The production of AGEs results in reactive nitrogen (RNS) and oxygen species (ROS), oxidative stress, inflammation, and structural damage.4 Crosslinking increases stiffness and reduces viscoelasticity in connective tissues such as the crystalline lens, zonules, sclera and other ocular structures that undergo the same aging processes as other connective tissues, making them stiff and rigid.7
Ocular rigidity creates a chain reaction of age-related biomechanical dysfunction, which results in the loss of the eye’s dynamic focusing mechanism including reduced pupillary response, decreased ability to change lens shape to focus light on the retina and decreased excursion capability of the ciliary muscle to exert sufficient forces on the lens for dynamic range of focus (DRoF). Since the accommodation and disaccommodation functions of DRoF are also responsible for the ocular biotransport functions of the eye, there is also a reduction in ocular metabolic efficiency related to age-related biomechanical insufficiency.8 These age-related consequences may also have progressive and long-term effects on ocular health.
Presbyopia treatments include optical devices as well as surgery.Optical devices include bifocal spectacles and contact lenses. Corneal surgeries include implants to change the shape or refractive power, or create a pinhole effect to increase the depth of focus. Corneal refractive surgery may create monovision or alter corneal shape to create multifocality. Intraocular implants manipulate optics to split light in the form of diffractive intraocular lenses (IOLs) or increase the depth of focus in the form of extended depth-of-field IOLS.Topical therapeutics may minimise the pupil size to increase depth of focus for several hours; however, none of these treatments address the cause of the loss of DRoF.
Laser scleral microporation (LSM) rejuvenates DRoF by addressing the biomechanical issues resulting from progressive aging. LSM is performed using an Erbium:YAG laser to reduce ocular rigidity by creating proprietary patterns of micropores in four oblique quadrants avoiding contact with the extraocular muscles (see Figure 1).The result of the therapy is an increase in scleral pliability, allowing underlying structures to move more freely, thereby improving DRoF ability. The direct result of LSM is the increase of ciliary muscle forces, allowing the lens to change shape during both phases of DRoF, ie, accommodation to disaccommodation and disaccommodation to accommodation. LSM therapy recovers the vision lost by progressive age, thereby improving “visual age” and HRQOL.
Results from a pilot study were reported at the British Society of Cataract & Refractive Surgery (BSCRS) meeting in Oxford, England, in July 2023. One hundred eyes of 50 emmetropic presbyopes were prospectively evaluated after receiving binocular laser scleral microporation. Fifteen males and 35 females with an average age of 56.6 (±4.0) with a mean reading addition of +2.00 D (±0.21 D) were enrolled. Presbyopia manifesting as a reading add of greater than 1.25 D, distance corrected near visual acuity at 40 cm of 20/50 or worse, uncorrected near visual acuity of 20/50 or worse, and a Near Activity Vision Questionnaire score of 10 or worse was required.Subjects were emmetropic such that manifest refraction found less than 1.00 D of astigmatism and spherical equivalent of ±0.50 D in each eye. Eyes were free of disease without surgical history except for keratorefractive vision correction (LASIK/PRK). Distance corrected as well as uncorrected acuity at 4 m, 60 cm and 40 cm was measured using ETDRS charts in controlled lighting. Refraction measured the add power required to read 20/20 at 40 cm. Intraocular pressure was measured using Goldmann. The Near Activity Visual Questionnaire was the chosen patient reported outcome measure. All tests were performed at baseline and repeated postoperatively at 3, 6,12, 18 and 24 months.
All subjects underwent an outpatient bilateral LSM procedure in an institutional review board-registered pilot study performed at the Asian Eye Institute, Makati City, Philippines, by principal investigator Robert T. Ang, MD.The LSM procedure was performed using a 2.94-μm Er:YAG laser (Visiolite® Ophthalmic Laser).Four 5 mm x 5 mm diamond matrices of micropores were created in the sclera across 5 critical anatomical zones posterior to the limbus.9 Each micropore was 225 µm in diameter at 85% scleral depth. Topical antibiotics and steroids were used postoperatively for one week. No complications were encountered in the pilot study other than occasional subconjunctival hematoma.
The distance corrected visual acuity (VA) is shown in Figure 2. Distance VA remained stable with no significant change from baseline. Corrected intermediate visual acuity improved from 0.12 logMAR at baseline to 0 at 6 months, 0.07 at 12 months and 0.09 at 24 months. Corrected near visual acuity improved from 0.45 logMAR at baseline to 0.19 at 6 months, 0.24 at 12 months and 0.28 at 24 months. Similar improvements were noted in uncorrected visual acuity (Figure 3).
UDVA remained stable. Uncorrected intermediate visual acuity improved from 0.14 logMAR to -0.005 at 6 months, 0.07 at 12 months and 0.11 at 24 months. UNVA improved from 0.45 logMAR to 0.2 at 6 months, 0.25 at 12 months and 0.32 at 24 months.
The required reading add power dropped significantly after LSM(Figure 4). The mean baseline add power of +2.00 D fell to +1.25 D at 6 months and remained steady until 24 months. The patient-reported outcome results demonstrated significantly improved quality of life at all time points. Rausch score improved from 64.68 at baseline to 40.1 at 12 months, and 38.70 at 24 months. While 98% were a little or completely unsatisfied at baseline, at 12 months only 26% felt unsatisfied. At 24 months, 67% were completely, very, or moderately satisfied.
The most distinct advantages of LSM are that: it is an extraocular procedure, as it is not performed over the visual axis; no optics are manipulated; and it has a quick recovery time, making it an ultraminimally invasive therapeutic. Discomfort is minimal and patients are able to demonstrate improved DRoF quickly with performance of 20/40 or better DCNVA measured the next day (Figure 5). This is a clean procedure, easily performed in an in-office suite. The cornea is untouched, and there is no mechanism for increased glare, halos or dystopias.
Undergoing LSM has no effect on future treatments such as phacoemulsification or keratorefractive procedures. In addition, LSM may be combined with topical miotics and other optical interventions if desired to maximize near visual effect. LSM, unlike other vision correction presbyopia treatments, is dosable and retreatable.
LSM can be performed at onset or anytime after onset, allowing it to be the first therapeutic to treat progressive presbyopia throughout the aging cycle. The long-term data reported are encouraging for a therapeutic that addresses the pathogenesis of presbyopia and is able to effectively recover lost vision due to age.
References
1. Tahhan N, Papas E, Fricke TR, Frick KD, Holden BA. Utility and uncorrected refractive error. Ophthalmology. 2013;120(9):1736-1744.
2. Berdahl J, Bala C, Dhariwal M, Lemp-Hull J, Thakker D, Jawla S. Patient and Economic Burden of Presbyopia: A Systematic Literature Review. Clin Ophthalmol. 2020;14:3439-3450.
3. Croft MA, Lütjen-Drecoll E, Kaufman PL. Age-related posterior ciliary muscle restriction--a link between trabecular meshwork and optic nerve head pathophysiology. Exp Eye Res. 2017;158:187-189.
4. Henning C, Glomb MA. Pathways of the Maillard reaction under physiological conditions. Glycoconj J. 2016;33(4):499-512.
5. Bailey AJ, Paul RG, Knott L. Mechanisms of maturation and ageing of collagen. Mech Ageing Dev. 1998;106(1-2):1-56.
6. Watson PG, Young RD. Scleral structure, organisation and disease. A review. Exp Eye Res. 2004;78(3):609-623.
7. Gautieri A, Passini FS, Silván U, et al. Advanced glycation end-products: mechanics of aged collagen from molecule to tissue. Matrix Biol. 2017;59:95-108.
8. Hipsley AM, Dementiev D. VisioDynamics Theory A Biomechanical Model for the Aging Ocular Organ. Jaypee Brothers Medical Publishers; 2006.
9. Knaus KR, Hipsley A, Blemker SS. The action of ciliary muscle contraction on accommodation of the lens explored with a 3D model. Biomech Model Mechanobiol. 2021;20(3):879-894.
Authors
Professor Sunil Shah, MD | Prof Shah, MD, FRCOphth, is a consultant ophthalmic surgeon at the Birmingham and Midland Eye Centre. He is a specialist advisor for the National Institute for Clinical Excellence and the Medicines and Healthcare Products Regulatory Authority in the United Kingdom, and on the medical advisory board of Ace Vision Group.
AnnMarie Hipsley, DPT, PHD | Dr Hipsley, DPT, PhD, is the founder and CEO of Ace Vision Group.
Robert T. Ang, MD | Dr Ang is senior refractive surgeon at the Asian Eye Institute, Philippines, and a member of the medical advisory board at Ace Visiion Group.
Mitchell Jackson, MD | Dr Jackson is a clinical associate at the University of Chicago Hospitals, the founder and medical director of Jackson Eye, and a board advisor for Ace Vision Group.
