Dry eye in Parkinson's disease: a narrative review

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TL;DR

Dry eye disease affects up to 70% of Parkinson's disease patients due to reduced blink rates, autonomic dysfunction, and medication side effects. This narrative review summarizes the pathogenesis, clinical evaluation, impact on quality of life, and management of dry eye in PD. The authors emphasize that dry eye significantly worsens quality of life and recommend multidisciplinary care including ophthalmologists, but note that most treatments have not been specifically studied in PD patients.

Full summary

4,073 CHARS

**Background** Parkinson's disease (PD) is a neurodegenerative disorder with a wide range of non-motor symptoms, including visual disturbances. Dry eye disease (DED) is particularly common, with a prevalence as high as 70% in PD patients. The aim of this narrative review is to examine the pathogenesis, clinical evaluation, impact on quality of life (QoL), and management of dry eye in PD.

**Methods** This is a narrative review of the literature on dry eye in Parkinson's disease. The authors searched for relevant studies on pathogenesis, clinical evaluation (subjective and objective assessments), impact on QoL, and management strategies. The review includes data from multiple clinical studies comparing PD patients to healthy controls.

**Key Results** - **Pathogenesis**: Several mechanisms contribute to dry eye in PD: (1) Decreased blink rates due to dopamine depletion in the CNS; blink rates are significantly reduced in PD patients compared to controls. (2) Autonomic dysfunction caused by Lewy bodies in the substantia nigra and sympathetic/parasympathetic ganglia, leading to lacrimation disturbances. (3) Changes in meibum lipid composition and tear proteins involved in lipid metabolism, oxidative stress, and immune response. (4) Antiparkinsonian medications (e.g., benzhexol, pramipexole, levodopa) with anticholinergic effects can cause dryness of mucous membranes. - **Clinical evaluation**: - Subjective assessment: The Ocular Surface Disease Index (OSDI) is the most commonly used questionnaire. OSDI scores were significantly higher in PD patients compared to healthy subjects. - Objective tests: - Schirmer test: Significantly lower in PD patients vs. controls in multiple studies (e.g., 6.52 ± 2.94 mm/5 min vs. 11.3 ± 6.16 mm/5 min; 6.56 ± 4.75 vs. 12.81 ± 5.68; 9.08 ± 4.46 vs. 17.16 ± 9.57; 4.3 ± 1.8 vs. 9.4 ± 3.0; 13.20 ± 10.45 vs. 17.49 ± 11.16 mm). - Tear break-up time (TBUT): Significantly lower in PD patients in most studies, though one study found no significant difference. - Ocular surface staining: Higher corneal fluorescein staining in PD patients vs. controls. - Anterior segment OCT: Central corneal thickness (CCT) significantly decreased in PD patients; stromal thickness negatively correlated with disease duration and severity, and positively correlated with TBUT and Schirmer scores. - Blink rates: Significantly decreased in PD patients; inversely correlated with disease severity (Hoehn-Yahr scores) in several studies. - **Impact on QoL**: 53% of PD patients reported moderate-to-severe effect of ophthalmologic symptoms on QoL (vs. 16% of controls). 44% of PD participants reported poor QoL due to visual disturbances. Dry eye is associated with increased risk of depression and anxiety, which are already common in PD (prevalence up to 90%). - **Management**: Treatment options include patient education, elimination of precipitating medications (though often not feasible in PD), artificial tear substitutes, anti-inflammatory agents (topical cyclosporine, corticosteroids), punctal plugs, moisture chamber glasses, and tarsorrhaphy. However, none of these treatments have been specifically studied in PD patients. PD-related motor impairments may hinder self-administration of eye drops. - **Sjögren's syndrome**: The risk of PD is 1.37 times greater in patients with autoimmune rheumatic diseases. Incidence of PD in SS patients was 2.5% (215/8,422). SS should be considered in PD patients with xerostomia and dry eye.

**Clinical Implications** Dry eye is a frequent and underrecognized non-motor symptom in PD that significantly impairs quality of life. Clinicians should routinely assess for dry eye in PD patients using both subjective questionnaires (e.g., OSDI) and objective tests (Schirmer test, TBUT, blink rate evaluation). Management should be individualized, but treatment adherence may be challenging due to motor impairments. A multidisciplinary approach including ophthalmologists is recommended. More research is needed on dry eye treatments specifically in PD populations.