The Impact of Artificial Lighting on the Visual Capacity of Patients With Age-Related Macular Degeneration

Introduction Aging is associated with an increased prevalence of neurodegenerative disorders and leads to irreversible changes in both humans and animal models. The retina, a layer of neural tissue that lines the interior of the eyeball, is exposed to various harmful and stressful environmental factors, including age-related changes, which affect its function. Age-related macular degeneration (AMD) is the leading cause of visual decline and blindness worldwide in individuals aged 65 years and older. The number of patients suffering from AMD is expected to increase significantly in the coming decades. AMD primarily affects the macular region of the retina, which is responsible for central vision. It has a significant impact on patients' lives due to the loss of sharp and color vision, interfering with daily activities such as recognizing faces and reading.

To date, there is no proven treatment that slows or prevents the progression of advanced AMD. Laser photocoagulation and photodynamic therapy reduce the risk of moderate or severe vision loss in some individuals with the neovascular form of the disease. Other medical and surgical interventions are under investigation, but none have been shown to be effective. Identifying the exact pathophysiological mechanisms of AMD remains challenging. However, clinico-pathological observations and epidemiological studies have provided valuable insights into potential pathways involved in AMD development. AMD is generally classified into two forms: non-exudative (dry or atrophic) and exudative (wet).

Exudative AMD is characterized by the development of choroidal neovascularization (CNV), i.e., fibrovascular tissue that grows from the choriocapillaris, penetrates through breaks in Bruch's membrane into the sub-retinal pigment epithelium (RPE) space, and then under the neurosensory retina. Dry AMD involves dysfunction in the RPE-Bruch's membrane-choriocapillaris complex, resulting in lesions such as drusen (small, yellow-white deposits located mainly in the macular area), focal pigment clumping, and RPE atrophy. The most severe atrophic lesion observed in AMD is geographic atrophy, characterized by a well-demarcated round or oval area of depigmentation or clear absence of RPE cells.

The wet form of AMD represents less than 10% of cases but can lead to severe complications if untreated. The latest approach in CNV treatment includes intravitreal injections of anti-angiogenic agents. Vascular Endothelial Growth Factor (VEGF) plays a key role in angiogenesis and in the development of all forms of wet AMD, regardless of angiographic appearance, and increases vascular permeability. Anti-VEGF drugs aim to inhibit VEGF activity, thereby suppressing neovascular growth and reducing vascular leakage. However, this therapy merely delays disease progression. Thus, there is a need for novel preventive and therapeutic strategies targeting AMD.

One factor influencing AMD patients' ability to perform daily activities is lighting conditions. According to current literature, the ideal lighting conditions for AMD patients have not yet been thoroughly studied. Recently, our research team published a pioneering mathematical model to determine optimal lighting intensity in phakic and pseudophakic patients. Identifying optimal lighting for AMD patients could greatly enhance their quality of life.

It is also known that some individuals overestimate or underestimate their functional daily abilities based on self-assessed visual performance using questionnaires. Moreover, visual acuity alone is insufficient to provide a comprehensive assessment of patients' visual capacity. Ideally, any functional impairment should be objectively and realistically evaluated for each patient, either at home or in their work environment, by carefully assessing their performance in specific daily tasks.

Various activities have been developed to assess distance, as well as near and intermediate visual abilities. Mobility has been assessed in individuals with glaucoma using a specific framework of daily activities, and near/intermediate vision tasks have been evaluated in AMD patients. In contrast, performance in individuals with presbyopia and in those who have undergone presbyopia-correcting surgery has been evaluated using a different activity framework under stable or variable lighting conditions to determine optimal illumination levels.

Purpose The aim of this study is to evaluate the performance of patients with advanced-stage dry AMD in daily activities under different lighting conditions.

Method

This is a prospective observational comparative study involving a total of 60 participants, divided into two groups:

Healthy controls over the age of 60

Patients with bilateral diagnosed advanced AMD (according to the UK's National Institute for Health and Care Excellence-NICE-or AREDS 9-step classification), fulfilling at least one of the following criteria:

1. Geographic atrophy of the macula ii) Best-corrected visual acuity in the affected eye <6/18 or logMAR >0.4 with dense/confluent drusen, advanced RPE changes, or vitelliform lesions iii) Fibrous scar iv) RPE tear v) Atrophy (absence/thinning of RPE and/or retina) vi) Cystoid degeneration (persistent intraretinal fluid or tubular structures unresponsive to therapy)

All participants will undergo a clinical evaluation at the Ophthalmology Outpatient Clinic and the Gait Analysis Laboratory of the University General Hospital of Evros. Initial assessments will include best-corrected monocular visual acuity using the validated DDiVAT chart and contrast sensitivity using the Pelli-Robson chart. Diagnostic evaluations will include macular optical coherence tomography (OCT), OCT angiography (OCT-A), and fundus autofluorescence imaging for AMD staging. All examinations will be conducted in accordance with standard clinical practice, without any interventional medical procedures.

Following clinical evaluation, participants will perform five daily activities under eight different lighting intensities (20, 50, 100, 125, 150, 200, 250, and 300 lux), with fixed light temperature (4000K). The performance will be assessed at the Gait Analysis Laboratory, which features a custom lighting setup of four adjustable light fixtures, installed based on a professional lighting design study.

The lab is equipped with an infrared motion-detection camera system, which, through special body-mounted reflectors, captures full-body movement, task duration, and motion fluidity in real time.

Additionally, the setup includes eye-tracking glasses, capable of measuring pupil size, blink rate, and saccadic eye movements. All devices are controlled by integrated software that extracts the data mentioned above. This system will be used to evaluate patients' performance in daily tasks under each lighting condition.

Daily Activities

Mobility: Patients walk a set distance along a corridor with grey obstacles at their self-selected pace.

Reach and grasp tasks: A white table is divided into 9 sections. Three small (24 mm), three medium (55 mm), and three large (73 mm) objects are randomly placed. Participants are asked to locate a specific object and place it on a marked black cross at a designated spot.

Sit-to-stand and stand-to-sit: Patients transition between two chairs placed opposite each other, repeating the sequence three times as fast as possible.

Overhead obstacle avoidance: Patients pass under a stretched rope placed at 1.5 m height.

Clothesline task: Patients pick up four differently colored garments from a basket and hang them on a fixed clothesline using clothespins.

Primary Outcome Activity Scores: Each participant's activity score will be calculated based on task completion time and errors. Errors will incur time penalties. A total completion time will be derived for each activity under each lighting condition. A custom scoring scale from 0 (lowest) to 100 (highest) will be developed. Each participant's performance score will be generated from this scale, determining the optimal lighting condition for AMD patients.

Secondary Outcome Pupil Size: The behavior of patients' pupil sizes under different lighting conditions will be assessed to correlate pupil response with light intensity.

Statistical Analysis An a priori power analysis was conducted. For an effect size of 0.17 of the activity score, 26 participants will be required in each study group to achieve a power of 0.8 at a significance level of 0.05. The normality of measurement data will be assessed using the Shapiro-Wilk test. Normally distributed data will be analyzed with the t-test. Non-normally distributed data will be analyzed with the Mann-Whitney U test. p-values < 0.05 will be considered statistically significant. All statistical analyses will be performed using the Medcalc statistical software (Medcalc Software, Mariakerke, Belgium).