LEMUR: A Ultra-Lightweight Distilled Retinal Foundation Model Using Mamba

This repository contains a unified pipeline for distilling a student VMamba model from a RETFound teacher, training classification heads, and evaluating on retinal fundus datasets (IDRiD, APTOS, MBRSET).

This README focuses on the CLI (main.py) and the actual project layout so you can run evaluation and training quickly.

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Repository layout (actual)

• main.py — unified CLI entrypoint (see CLI section below)
• config/ — constants.py (defaults and environment-driven overrides)
• dataloader/ — idrid.py, aptos.py (Lightning DataModules)
• models/ — retfound.py, vmamba_backbone.py, dist.py, models_vit.py
• train/ — distill.py, head.py, train_retfound.py
• eval/ — eval_vmamba.py, eval_retfound.py, shared_eval.py
• optimizers/ — optimizer.py (helper for warmup + cosine schedule)
• utils/ — utilities (flops.py, pos_embed.py, etc.)
• imgs/, results/ — example outputs and CSVs
• requirements.txt, simple_test.ipynb

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CLI (main.py) — modes and arguments

Run python main.py --run <mode> [options].

Modes (value for --run):

• distill — Phase I: distill RETFound teacher -> VMamba student
• head — Phase II: train classification head on distilled backbone
• eval — Evaluate VMamba (expects a checkpoint saved by head training)
• retfound_linear — RETFound linear probe (uses train_retfound.py)
• retfound_finetune — RETFound fine-tuning
• retfound_eval — Evaluate a RETFound Lightning checkpoint

Shared CLI arguments (most common):

• --lr — learning rate (default from config/constants.py)
• --mask_ratio — mask ratio used during distillation
• --dist_epochs — number of distillation epochs
• --head_epochs — number of head training epochs
• --teacher_ckpt — optional teacher checkpoint override
• --load_backbone — path to distilled backbone (required for --run head)
• --load_model — path to full model checkpoint for evaluation (required for --run eval and --run retfound_eval)
• --dataset — idrid (default) or aptos

RETFound-specific:

• --checkpoint — RETFound pretrained checkpoint (optional)
• --epochs — epochs for RETFound linear/finetune modes

The CLI enforces required flags per mode (e.g., --load_backbone for head). See main.py for the full help text.

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Common commands / examples

Evaluation — VMamba (IDRiD):

python main.py --run eval --load_model CHECKPOINT_PATH --dataset idrid

Evaluation — VMamba (MBRSET):

python main.py --run eval --load_model CHECKPOINT_PATH --dataset mbrset

Evaluation — VMamba (APTOS):

python main.py --run eval --load_model CHECKPOINT_PATH --dataset aptos

Evaluation — RETFound Lightning ckpt:

python main.py --run retfound_eval --load_model checkpoints/retfound_finetuned.ckpt --dataset idrid

Distillation (Phase I):

python main.py --run distill --lr 1e-4 --mask_ratio 0.75

Head training (Phase II):

python main.py --run head --load_backbone checkpoints/vmamba_distilled_student.pth --lr 1e-4

RETFound linear / finetune:

# Linear probe
python main.py --run retfound_linear --dataset idrid --lr 3e-4

# Fine-tune
python main.py --run retfound_finetune --dataset aptos --lr 1e-5

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Checkpoints & formats

• VMamba head output (train/head.py) saves a file expected by eval that contains two keys: backbone and head (each a state_dict).
• RETFound evaluation expects a PyTorch Lightning checkpoint compatible with train/train_retfound.RETFoundTask.