OP4.4 | Corneal Opacity: Identification, Grading and Management — Summary & Reflection

KEY TAKEAWAYS

Corneal opacity is classified by density: nebula (faint, oblique illumination, iris clearly visible), macula (visible in direct light, iris visible through it), leukoma (dense white, iris not visible), and adherent leukoma (leukoma adherens — iris adherent to posterior scar surface, typically post-perforation). Location relative to the visual axis determines visual impact; depth determines surgical approach.

Pathophysiology: scar tissue replaces the regular Maurice collagen lattice with disorganised fibrous collagen, causing constructive (not destructive) light scatter and permanent opacity.

Assessment: slit-lamp optical section (depth), AS-OCT (precise depth measurement), specular microscopy (endothelial cell count), visual acuity + pinhole (pinhole does NOT improve opacity-related VA), projection of light test + B-scan (posterior segment integrity before surgery).

Management modalities:
- PTK (excimer laser): anterior opacity ≤150 µm
- DALK: anterior-mid stromal opacity with healthy endothelium; no rejection of host endothelium
- PK: full-thickness opacity or Descemet's/endothelium involved; endothelial rejection risk — needs lifelong topical steroids
- DSEK/DMEK: endothelial failure alone without stromal opacity

REFLECT

The woman in the hook has waited 20 years with a leukoma. She is not unusual — corneal blindness in rural India is under-served because eye banking is concentrated in urban centres. As you finish this module, reflect: what barriers exist between a rural patient with a post-infective leukoma and a corneal transplant? What could a primary-care doctor in a rural area do at the first presentation of corneal ulcer to prevent the scar forming, or to make an early referral? If you were designing a screening programme for corneal blindness in India, what clinical skill — learnable by a rural health worker — would you prioritise?