**Background:** Various squamate species (snakes and many lizards) have completely fused, transparent eyelids that form a spectacle. This structure is a continuation of the integument and is renewed with each shedding cycle. Between the spectacle and the cornea lies a narrow subspectacular space filled with lacrimal fluid produced by the Harderian gland (lacrimal glands are absent in most spectacled squamates). The fluid drains via a tortuous lacrimal duct to the oral cavity. While ocular disease is uncommon in these reptiles, disorders of the spectacle and subspectacular space are frequently encountered in veterinary practice. This narrative review synthesizes current knowledge on the anatomy, physiology, and clinical disorders of this system.
**Methods:** This is a narrative review that synthesizes published literature on the anatomy, physiology, and clinical disorders of the spectacle, subspectacular space, and lacrimal drainage system in squamates. The authors draw on histological, anatomical, and clinical studies, including computed tomographic anatomy, optical coherence tomography, and experimental wound healing studies. They also incorporate clinical observations from their own experience.
**Key Results:** The spectacle consists of three layers: an outer epithelial layer (3.5–10.5 μm) covered by alternating alpha and beta keratin, an inner epithelial layer (1.6–3.6 μm) continuous with the palpebral conjunctiva, and a stroma (9–132 μm) containing collagen fibrils, blood vessels, fibroblasts, and nerve fibers. Spectacle thickness ranges from 74 to 244 μm in snakes, with the thinnest in arboreal/terrestrial species and the thickest in aquatic/fossorial species. The spectacle is the main refractive surface (refractive index ≥1.5). The lacrimal duct shows a tortuous course that varies between species, potentially predisposing certain taxa to disorders. Common disorders include: (1) Retained spectacle (dysecdysis) due to inappropriate humidity, ectoparasites, or systemic disease; (2) Spectaculitis (inflammation) often from bacterial or fungal infection (e.g., Ophidiomyces ophiodiicola); (3) Pseudobuphthalmos (bullous spectaculopathy) from lacrimal duct obstruction, causing clear fluid accumulation; (4) Subspectacular infection (abscess) from ascending bacterial infection (e.g., Pseudomonas aeruginosa, Aeromonas spp., Salmonella spp.) often with concurrent flagellated protozoa (Tritrichomonas, Monocercomonas). Boa constrictors and Burmese pythons are particularly predisposed to subspectacular infection. Treatment of subspectacular abscess involves partial spectaculectomy (25–30° wedge in ventrolateral quadrant), drainage, and topical antimicrobial therapy based on culture and susceptibility. Conjunctivoralostomy may be required for persistent pseudobuphthalmos.
**Clinical Implications:** A thorough understanding of the unique anatomy and physiology of the spectacle and its drainage system is fundamental for diagnosing and managing these common disorders. Clinical examination should include comparison of both eyes, slit-lamp biomicroscopy, and assessment of the oral cavity for stomatitis. Sampling of subspectacular fluid for cytology, culture, and molecular testing is essential. Treatment must address primary causes such as stomatitis, respiratory infection, or environmental deficiencies. The prognosis for congenital pseudobuphthalmos is poor, while subspectacular infection generally responds well to appropriate surgical and medical therapy. The review emphasizes that the spectacle is an integral part of the skin and heals via a proteinaceous crust scaffold, with full regeneration often requiring one or more shedding cycles.